JP7684562B2 - Dimming control device and dimming device - Google Patents

Description

The present invention relates to a dimming control device and a dimming device.

Conventionally, there has been an LED drive circuit that drives a light-emitting diode (LED) by controlling the conduction angle of the AC supplied from a commercial AC power source to phase-control the current supplied to the LED, a rectifier circuit that rectifies the AC voltage output from the dimmer circuit, a smoothing circuit that smoothes the DC voltage output from the rectifier circuit, a switching element connected in series to the LED, and a constant current control circuit that outputs a high-frequency pulse signal to the switching element to control the on/off of the switching element so that the current flowing through the LED is constant. The bleeder circuit is disposed between the output end of the rectifier circuit and ground and has a bleeder resistor and a bleeder switch connected in series, and the high-frequency pulse signal is input to the bleeder switch, causing a high-frequency pulse-like bleeder current to flow through the bleeder resistor (see, for example, Patent Document 1).

JP 2011-124163 A

In order to control the dimming of light-emitting elements such as LEDs, dimmers that control phase with positive or negative phases are sometimes used. Phase control is completely different between positive and negative phases, but conventional light-emitting element driving devices are not configured to be compatible with either positive or negative phases. Dimmers that control phase with positive phase and dimmers that control phase with negative phase are of different types.

Therefore, the objective is to provide a dimming control device and a dimming device that can accommodate different types of dimmers.

The dimming control device according to an embodiment of the present invention includes a voltage acquisition unit that acquires a rectified voltage obtained by rectifying the output of a dimmer that controls the phase of an AC voltage in a positive or negative phase in a rectifier circuit, a current control element that controls the drive current supplied to a light emitter, and a drive control unit that drives and controls the current control element according to the voltage acquired by the voltage acquisition unit. The drive control unit has a drive control signal generation unit that sets a duty ratio in the pulse width modulation of a drive control signal that drives the current control element according to the voltage acquired by the voltage acquisition unit, and generates a drive control signal having the duty ratio, and a falling edge detection unit that detects a falling edge of the absolute value of the voltage when the voltage acquired by the voltage acquisition unit is in the opposite phase, and the drive control signal generation unit sets the duty ratio by setting the time point at which the falling edge is detected by the falling edge detection unit as the end time point of the on period of the pulse width modulation.

It is possible to provide a dimming control device and a dimming device that are compatible with different types of dimmers.

FIG. 2 is a diagram showing a circuit configuration of a light control device 100 according to an embodiment. FIG. 2 is a diagram illustrating a positive phase and a negative phase. FIG. 4 is a waveform diagram illustrating an operation 1 of the dimming control device 100A. FIG. 13 is a flowchart showing a process for realizing operation 1. FIG. 11 is a waveform diagram illustrating an operation 2 of the dimming control device 100A. FIG. 13 is a flowchart showing a process for realizing operation 2. FIG. 11 is a diagram illustrating an operation 3 of the dimming control device 100A. FIG. 13 is a flowchart showing a process for realizing operation 3. FIG. 11 is a diagram for explaining an operation 4 of the dimming control device 100A. FIG. 13 is a diagram showing a correction table indicating correction values of duty ratios. FIG. 11 is a diagram for explaining an operation 5 of the dimming control device 100A. FIG. 6 is a diagram for explaining an operation 6 of the dimming control device 100A.

The following describes an embodiment in which the dimming control device and dimming device of the present invention are applied.

<Embodiment>
FIG. 1 is a diagram showing a circuit configuration of a dimming device 100 according to an embodiment. The dimming device 100 includes a dimming control device 100A, a dimmer 10, and an LED (Light Emitting Diode) 20. The LED 20 is an example of an illuminant. The dimming device 100 can be used as a lighting device for a room in a building, for example. In the following, as an example, a configuration in which the dimming device 100 is installed in a room of a building, the dimmer 10 is attached to a wall or the like in the building, and can be operated by a user in the building will be described. The building in which the dimming device 100 is installed has power supply terminals 1A and 1B that supply power to the dimming device 100. The power supply terminals 1A and 1B output AC power.

The dimmer 10 has a dial switch or the like for adjusting the amount of light, and the light amount of the LED 20 is adjusted by the dimming control device 100A when the user operates the dial switch or the like. The dimmer 10 is inserted in series between the power supply terminal 1A and the terminal 101A of the dimming control device 100A, and controls the phase of the AC power voltage input from the power supply terminal 1A in a positive or negative phase and outputs it to the terminal 101A. There are two types of dimmers 10: one that performs phase control in a positive phase, and one that performs phase control in a negative phase. The dimming control device 100A can be used with either type of dimmer 10.

Before explaining the configuration of the dimming control device 100A, we will now explain the positive and negative phases using Figure 2.

<Positive and negative phase>
Fig. 2 is a diagram explaining the positive phase and the negative phase. In Fig. 2, the horizontal axis indicates time and the vertical axis indicates voltage. Fig. 2(A) shows an AC voltage with a period T. The amplitude (voltage) of the AC voltage changes sinusoidally as time passes from time t0. The period from time t0 to T/2 is the first half, and has a positive amplitude. The remaining period of T/2 is the second half, and has a negative amplitude. Power supply terminals 1A and 1B output an AC voltage as shown in Fig. 2(A).

Figure 2 (B) shows the output waveform of the dimmer 10 performing phase control in positive phase. The AC voltage shown in Figure 2 (A) is input to the dimmer 10, and the positive phase dimmer 10 cuts the waveform from the start of the first half T/2 period to the period T1 and outputs it, and also cuts the waveform from the start of the second half T/2 period over the period T1 and outputs it.

Figure 2 (C) shows the output waveform of a dimmer 10 that performs phase control in the opposite phase. The AC voltage shown in Figure 2 (A) is input to the dimmer 10, and the opposite phase dimmer 10 cuts the waveform from the end of the first half T/2 period to the period T1 and outputs it, and also cuts the waveform from the end of the second half T/2 period over the period T1 and outputs it.

In this way, the period during which the waveform is cut is different between the positive phase dimmer 10 and the negative phase dimmer 10. The output of the positive phase dimmer 10 is less susceptible to the effects of the capacitance, inductance, etc. of the dimming control device 100A because the waveform starts to increase from a zero amplitude state in both the first and second halves of one cycle T.

In contrast, the output of the opposite-phase dimmer 10 suddenly cuts off the waveform from a state where there is a certain amount of amplitude in both the first and second halves of one cycle T, so that due to the influence of the capacitance and inductance of the dimming control device 100A, the amplitude does not suddenly drop to zero at the start of period T1 as shown in FIG. 2(C), but drops gradually. When such an event occurs, the amount of light emitted by the LED 20 does not become the amount of light adjusted by the dimmer 10, and the amount of light emitted becomes brighter than the amount of light the user expects.

When the dimming control device 100A is connected to a reverse phase dimmer 10, it is possible to adjust the light emission amount of the LED 20 according to the amount of operation of the dimmer 10, just as when it is connected to a positive phase dimmer 10. In this way, a dimming control device 100A and a dimming device 100 that can be used with different types of dimmers 10 are provided. Next, the configuration of the dimming control device 100A will be described using FIG. 1.

<Configuration of dimming control device 100A>
The dimming control device 100A includes terminals 101A and 101B, a filter circuit 111, a rectifier circuit 112, a voltage dividing circuit 113, a power factor correction (PFC) circuit 114, a smoothing capacitor 114A, a field effective transistor (FET) 115, a transformer 116, a rectifier circuit 117, an output voltage detection unit 117A, a current control element 118, a capacitor 118A, and output terminals 119A and 119B. The voltage dividing circuit 113 is an example of a voltage acquisition unit.

The dimming control device 100A further includes a first driver 120, a control device 130, a second driver 140, a discharge circuit 150, a temperature detection unit 160, and an output voltage detection unit 170.

In the following, of the two power transmission lines connecting the filter circuit 111, rectifier circuit 112, PFC circuit 114, smoothing capacitor 114A, and FET 115 between terminals 101A, 101B, and the primary coil 116P of the transformer 116, the high-potential power transmission line connecting terminal 101A and the primary coil 116P is referred to as power transmission line 102H, and the low-potential power transmission line connecting terminal 101B and the primary coil 116P is referred to as power transmission line 102L.

Of the two power transmission lines connecting the rectifier circuit 117, the current control element 118, and the capacitor 118A between the secondary coil 116S of the transformer 116 and the output terminals 119A and 119B, the high-potential power transmission line connecting the secondary coil 116S and the output terminal 119A is referred to as power transmission line 103H, and the low-potential power transmission line connecting the secondary coil 116S and the output terminal 119B is referred to as power transmission line 103L.

Terminals 101A and 101B are a pair of input terminals of the dimming control device 100A. Terminal 101A is connected to power supply terminal 1A via the dimmer 10, and terminal 101B is directly connected to power supply terminal 1B. A filter circuit 111 is connected to the output side of terminals 101A and 101B.

The filter circuit 111 is a filter that blocks unnecessary components such as noise contained in the AC voltage input from the terminals 101A and 101B. The filter circuit 111 has a capacitor 111A and a filter 111B. The capacitor 111A is connected between the power transmission lines 102H and 102L, and the filter 111B is connected in a manner that is inserted into the power transmission lines 102H and 102L.

The rectifier circuit 112 has a bridge circuit in which four diodes are connected in a bridge shape, and full-wave rectifies the AC voltage input from the filter circuit 111 and outputs it. The PFC circuit 114 is connected to the output side of the rectifier circuit 112.

The voltage divider circuit 113 is connected by branching off from the power transmission line 102H on the high potential side between the rectifier circuit 112 and the PFC circuit 114. The voltage divider circuit 113 has, as an example, two voltage divider resistors, and the connection point 113A of the two voltage divider resistors is connected to the control device 130. The voltage divider circuit 113 obtains the rectified voltage rectified by the rectifier circuit 112.

The PFC circuit 114 is a power factor correction circuit, and is provided to reduce and output harmonic currents that may be contained in the power input from the rectifier circuit 112, as well as to reduce harmonic currents generated in the power supply unit 50, which will be described later. On the output side of the PFC circuit 114, a smoothing capacitor 114A is connected between the power transmission lines 102H and 102L, and smoothes the voltage output from the PFC circuit 114. As an example of the PFC circuit 114, a flyback boost circuit can be used.

The FET 115 is connected between the PFC circuit 114 and the primary coil 116P of the transformer 116 so that its drain-source is inserted in series with the low-potential side power transmission line 102L. The gate of the FET 115 is connected to the first driver 120 and is driven by a drive signal input from the first driver 120.

The transformer 116 has a primary coil 116P and a secondary coil 116S. The primary coil 116P is connected between the power transmission lines 102H and 102L on the output side of the PFC circuit 114 and the smoothing capacitor 114A. The secondary coil 116S is connected between the two power transmission lines 103H and 103L.

The rectifier circuit 117 is connected to the output side of the secondary coil 116S of the transformer 116, and has a diode inserted in series with the power transmission line 103H, and a smoothing capacitor connected between the power transmission lines 103H and 103L.

The output voltage detection unit 117A is connected by branching off from the power transmission line 103H on the high potential side between the rectifier circuit 117 and the current control element 118. As with the voltage divider circuit 113, the output voltage detection unit 117A has, as an example, two voltage divider resistors, and the connection point 117AA of the two voltage divider resistors is connected to the first driver 120. The output voltage detection unit 117A detects the voltage between both terminals of the smoothing capacitor of the rectifier circuit 117.

The smoothing capacitor 114A, the FET 115, the transformer 116, the rectifier circuit 117, the output voltage detector 117A, and the first driver 120 constitute the power supply unit 50. The configuration used as the power supply unit 50 is not limited to the flyback type circuit configuration shown in FIG. 1, but may be, for example, a synchronous rectifier type using a switch instead of the diode of the rectifier circuit 117. The power supply unit may also be realized with other isolated or non-isolated circuit configurations such as a forward type or pseudo-resonant type. The smoothing capacitor 114A may be regarded as part of the PFC circuit 114, rather than as part of the power supply unit 50.

The current control element 118 is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) whose gate and source are connected in series to the power transmission line 103H on the output side of the output voltage detection unit 117A. The gate of the current control element 118 is connected to the second driver 140. The current control element 118 is PWM (Pulse Width Modulation) driven by a drive control signal input to the gate from the second driver 140, and outputs a drive current from the drain. Note that a bipolar transistor may be used as the current control element 118.

Capacitor 118A is connected between power transmission lines 103H and 103L on the output side of current control element 118. Capacitor 118A is a smoothing capacitor.

Output terminals 119A and 119B are connected to power transmission lines 103H and 103L, respectively, inside dimming control device 100A, and are connected to two terminals (anode and cathode) of LED 20 outside dimming control device 100A. Output terminal 119A is connected to the anode, and output terminal 119B is connected to the cathode. Output terminals 119A and 119B are terminals that supply drive current to LED 20. The voltages at output terminals 119A and 119B are forward output voltages that dimming control device 100A applies to LED 20.

The first driver 120 is connected between the connection point 117AA of the output voltage detection unit 117A and the gate of the FET 115. The first driver 120 drives the FET 115 so that the current flowing through the primary coil 116P of the transformer 116 is constant according to the voltage detected by the output voltage detection unit 117A. The first driver 120 is a driver IC (Integrated Circuit) of the power supply unit 50, and controls the voltage between both terminals of the smoothing capacitor of the rectifier circuit 117 according to the voltage detected by the output voltage detection unit 117A.

The control device 130 has an input terminal 130IN, an output terminal 130OUT, an ADC (Analog to Digital Converter) 130A, and a drive control unit 130B.

The input terminal 130IN is connected to the connection point 113A of the voltage divider circuit 113, and is a terminal to which the voltage detected by the voltage divider circuit 113 is input. The output terminal 130OUT is connected to the second driver 140, and is a terminal that outputs a drive control signal to the second driver 140. The ADC 130A is connected between the input terminal 130IN and the drive control unit 130B, and converts the voltage input from the input terminal 130IN into a digital value and outputs it to the drive control unit 130B.

The drive control unit 130B is configured with an MCU (Micro Controller Unit). The drive control unit 130B configured with an MCU is realized by a computer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and an internal bus.

The drive control unit 130B has a drive control signal generation unit 131, a falling edge detection unit 132, a switching control unit 133, a signal correction unit 134, an increase processing unit 135, an interpolation processing unit 136, and a memory 137, and controls the drive of the current control element 118.

The drive control signal generating unit 131, the falling edge detecting unit 132, the switching control unit 133, the signal correcting unit 134, the increase processing unit 135, and the interpolation processing unit 136 are functional blocks that represent the functions of the program executed by the drive control unit 130B realized by the MCU. Also, the memory 137 is a functional representation of the memory of the drive control unit 130B.

The drive control signal generating unit 131 samples the voltage acquired by the voltage divider circuit 113 and converted to a digital value by the ADC 130A at a predetermined sampling period, and generates a waveform by arranging the sampled voltages (sampling voltages) in a time series. The sampling period is, for example, 30 μs. The drive control signal generating unit 131 sets a duty ratio in the pulse width modulation (PWM) of the drive control signal that drives the current control element 118 according to the sampling voltage, and generates a drive control signal having the duty ratio. The drive control signal is output from the output terminal 130OUT to the second driver 140.

When the sampling voltage is in positive phase, the drive control signal generating unit 131 sets the duty ratio to the point at which the sampling voltage becomes equal to or greater than the on threshold as the start point of the on period of the pulse width modulation.

When the sampling voltage is in opposite phase, the drive control signal generating unit 131 sets the duty ratio by setting the time when the falling edge is detected by the falling edge detecting unit 132 as the end time of the on period of the pulse width modulation. The drive control signal generating unit 131 also performs various processes to set the duty ratio of the drive control signal, but details will be described later.

The falling edge detection unit 132 detects the falling edge of the absolute value of the voltage when the sampling voltage of the drive control signal generation unit 131 is in opposite phase. The detection of the falling edge by the falling edge detection unit 132 will be described later with reference to Figures 3 and 4.

The switching control unit 133 switches the discharge circuit 150 to the connected state when a period obtained by subtracting a predetermined margin time from a half cycle of the AC voltage has elapsed since the falling edge is detected by the falling edge detection unit 132. The margin time is a time allowance.

The signal correction unit 134 corrects the duty ratio of the drive control signal so as to correct the change in the drive current caused by the change in temperature detected by the temperature detection unit 160. The process executed by the signal correction unit 134 will be described later with reference to Figures 9 and 10.

When the LED 20 starts emitting light, if the output voltage detected by the output voltage detection unit 170 is equal to or lower than a predetermined voltage, the increase processing unit 135 increases the duty ratio of the drive control signal so that the drive current increases. The process executed by the increase processing unit 135 will be described later with reference to FIG. 11.

The interpolation processing unit 136 performs an interpolation process using a first duty ratio of the drive control signal when the output voltage applied to the LED 20 is a first voltage and the drive current is a predetermined current, and a second duty ratio of the drive control signal when the output voltage applied to the LED 20 is a second voltage and the drive current is a predetermined current. The interpolation processing unit 136 uses the interpolation process to determine the duty ratio of the drive control signal when the drive current is a predetermined current at the output voltage detected by the output voltage detection unit 170. Details of the interpolation process performed by the interpolation processing unit 136 will be described later with reference to FIG. 12.

The memory 137 stores programs, data, etc. used by the drive control signal generation unit 131, the falling edge detection unit 132, the switching control unit 133, the signal correction unit 134, the increase processing unit 135, and the interpolation processing unit 136 of the drive control unit 130B when performing processing.

The second driver 140 is connected between the output terminal 130OUT of the control device 130 and the gate of the current control element 118. The second driver 140 converts the drive control signal input from the output terminal 130OUT of the drive control unit 130B into a format for driving the current control element 118, and outputs the converted drive control signal to the gate of the current control element 118. The second driver 140 is a driver IC.

The discharge circuit 150 has a first end 151 connected between the rectifier circuit 112 and the voltage divider circuit 113, and a second end 152 connected to a ground potential point serving as a voltage reference point. The discharge circuit 150 is a switch that can switch the first end 151 and the second end 152 between a connected state and a disconnected state by being controlled by the switching control unit 133.

The temperature detection unit 160 has a constant voltage regulator 160R, a thermistor 161, and a resistor 162. The constant voltage regulator 160R converts the power supplied from a power source (not shown) into a constant voltage and outputs it. The constant voltage regulator 160R is provided in a voltage divider circuit including the thermistor 161 and resistor 162 to keep the voltage value at the high potential terminal of the thermistor 161 constant.

The thermistor 161 is connected between the constant voltage regulator 160R and the resistor 162, and forms a voltage divider circuit together with the resistor 162. The thermistor 161 is, for example, an NTC (Negative Temperature Coefficient) thermistor, which has the property that its resistance value decreases as the temperature increases and increases as the temperature decreases. The resistor 162 is a resistor with a constant resistance value.

The connection point 160A between the thermistor 161 and resistor 162 is a connection point of the voltage divider circuit, and is connected to the control device 130. The potential at the connection point 160A increases as the temperature of the thermistor 161 increases. The temperature detected by the temperature detection unit 160 is the internal temperature of the package (housing) of the dimming device 100 and the dimming control device 100A, and is an example of the environmental temperature.

The output voltage detection unit 170 is connected by branching off from the power transmission line 103H on the high potential side between the capacitor 118A and the output terminal 119A. As with the voltage divider circuit 113, the output voltage detection unit 170 has, as an example, two voltage dividing resistors, and the connection point 170A of the two voltage dividing resistors is connected to the control device 130. The output voltage detection unit 170 detects the forward output voltage applied to the LED 20 from the output terminals 119A and 119B by the dimming control device 100A.

<Operation of the dimming control device 100A>
<Operation 1>
FIG. 3 is a waveform diagram for explaining operation 1 of the dimming control device 100A. FIG. 3(A) shows the operation in the case of a positive phase, and FIG. 3(B) shows the operation in the case of an opposite phase. In FIG. 3(A) and FIG. 3(B), the horizontal axis represents time, the vertical axis represents amplitude (voltage value), and the black circle represents the sampling voltage. The time between adjacent sampling voltages is the sampling period. Here, the number of samples in one period is shown to be small in order to make the drawing easier to see, but the number of samples is actually much larger. The sampling voltage is a value obtained by converting the voltage that has been full-wave rectified by the rectifier circuit 112 and divided by the voltage divider circuit 113 into a digital value, so the amplitude of the waveform formed by the sampling voltages arranged in time series is 0V or more.

The waveforms shown in Figures 3(A) and 3(B) are formed by a full-wave rectified sampling voltage, so the operation is repeated every half cycle of the AC voltage. Below, the sampling voltage is described using a unit period TU that corresponds to half the period T of the AC voltage. The unit period TU is equal to T/2. The duty ratio of the drive control signal is the ratio of the on period to the unit period TU.

When generating the drive control signal, the drive control signal generating unit 131 uses an on-threshold and an off-threshold. The on-threshold is, for example, 1.0 V, and the off-threshold is, for example, 0.8 V. The drive control signal generating unit 131 sets the on-period by setting the point at which the sampling voltage becomes equal to or greater than the on-threshold as the start point of the on-period of the duty ratio, and the point at which the sampling voltage becomes equal to or less than the off-threshold as the end point of the on-period of the duty ratio. The period other than the on-period of the unit period TU is the off-period. The duty ratio of the drive control signal is expressed as a percentage of the on-period of the unit period TU. The duty ratio is synonymous with the conduction angle. The off-threshold (0.8 V), which is smaller than the on-threshold (1.0 V), is used in order to provide hysteresis so that the start and end of the on-period can be stably determined. The values of the on-threshold (1.0 V) and the off-threshold (0.8 V) are examples, and can be changed according to the operating conditions of the dimming control device 100A.

Figure 3 (A) shows the theoretical values of the unit period TU and the on-period Ton. The theoretical value of the unit period TU is the period from the rising edge of the positive phase waveform to the next rising edge, and corresponds to the theoretical value of a half-cycle T/2. The theoretical value of the on-period Ton is the period from the rising edge of the positive phase waveform until the amplitude becomes 0V. The rising edge of the positive phase waveform is the end of the period T1 during which the waveform is cut.

In FIG. 3A, since the phase is positive, the waveform is cut from time t0 to period T1. The sampling voltage from time t0 to period T1 is 0V. At time t1A after period T1 has elapsed, the sampling voltage becomes equal to or greater than the on threshold, so the drive control signal generating unit 131 determines the time t1A when the sampling voltage becomes equal to or greater than the on threshold as the start of the on period Ton. When the sampling voltage becomes equal to or less than the off threshold at time t2A, the drive control signal generating unit 131 determines the time when the sampling voltage becomes equal to or less than the off threshold as the end of the on period Ton. The on period Ton is from time t1A to time t2A.

In addition, as an example, the drive control signal generating unit 131 can obtain the period from time t1A when the sampling voltage becomes equal to or greater than the on threshold to time t3A when the sampling voltage next becomes equal to or greater than the on threshold as the unit period TU. In the case of a positive phase, the drive control signal generating unit 131 sets a duty ratio using the on period Ton and unit period TU determined as described above, and generates a drive control signal having the duty ratio.

Figure 3 (B) shows the theoretical values of the unit period TU and on-period Ton in the case of opposite phase. The theoretical value of the unit period TU is the period from the start of the opposite phase waveform (time t0) to the start of the next, and corresponds to the theoretical value of a half cycle T/2. The theoretical value of the on-period Ton is the period from the start of the opposite phase waveform (time t0) to the point at which the waveform begins to be cut.

Since the sampling voltage becomes equal to or greater than the on-threshold at time t1B, the drive control signal generating unit 131 determines that the start time of the on-period Ton is time t1B, when the sampling voltage becomes equal to or greater than the on-threshold.

After determining the start point of the on-period Ton, the drive control signal generating unit 131 determines whether the decrease in the current sampling voltage relative to the sampling voltage of the previous sampling period (hereinafter referred to as the previous sampling voltage) is equal to or greater than a predetermined threshold each time the sampling voltage is acquired. This is because it is determined that a falling edge has occurred when the decrease in the sampling voltage in one sampling period is equal to or greater than a predetermined threshold. Note that the current sampling voltage is the voltage sampled in the latest sampling period.

At time t2B, when the decrease in the current sampled voltage relative to the previous sampled voltage becomes equal to or exceeds a predetermined threshold, the drive control signal generator 131 determines that the time t2B at which the fall occurs is the end point of the on-period Ton. The on-period Ton is from time t1B to time t2B.

As an example, the drive control signal generating unit 131 obtains the period from time t1B when the sampling voltage becomes equal to or greater than the on threshold to time t3B when the sampling voltage next becomes equal to or greater than the on threshold as the unit period TU. In the case of an opposite phase, the drive control signal generating unit 131 sets a duty ratio using the on period Ton and unit period TU determined as described above, and generates a drive control signal having the duty ratio.

<Flowchart for implementing operation 1>
4 is a diagram showing a flowchart showing the process for realizing operation 1. This process is executed by the drive control signal generating unit 131 and the falling edge detecting unit 132. The drive control signal generating unit 131 continues to acquire sampled voltages at a predetermined sampling period, and performs the following process on the latest sampled voltage (currently sampled voltage).

When the drive control signal generating unit 131 starts processing, it determines whether the dimmer 10 performs phase control in the opposite phase (step S1). Whether the dimmer 10 performs phase control in the opposite phase can be determined, for example, when a state in which the sampling voltage is 0 V continues multiple times, as in the period T1 shown in FIG. 3(A). Alternatively, for example, it may be possible to first observe the waveform formed by the sampling voltage over the unit period TU and determine whether the period T1 is at the beginning or end of the unit period TU.

When the drive control signal generating unit 131 determines that they are in opposite phase (S1: YES), it determines whether the sampling voltage is equal to or greater than the ON threshold (step S2A). This is to determine the start point of the ON period Ton. When the drive control signal generating unit 131 determines that the sampling voltage is not equal to or greater than the ON threshold (S2A: NO), it repeats the process of step S2A.

When the drive control signal generating unit 131 determines that the sampling voltage is equal to or greater than the on threshold (S2A: YES), it determines the start point of the on period Ton and determines the unit period TU (step S3A). The determination of the unit period TU is not limited to the timing when the sampling voltage becomes equal to or greater than the on threshold, and may be determined at other timings. However, as an example, here, the unit period TU is determined at the timing when the sampling voltage becomes equal to or greater than the on threshold, as in FIG. 3B.

The drive control signal generator 131 determines the decrease in the current sampled voltage relative to the previous sampled voltage (step S4A).

The falling edge detection unit 132 determines whether the decrease in the sampling voltage calculated by the drive control signal generation unit 131 in step S4A is equal to or greater than a predetermined threshold (step S5A). This is to detect a falling edge.

When the falling edge detection unit 132 determines that the decrease in the sampling voltage is not equal to or greater than the predetermined threshold (S5A: NO), the drive control signal generation unit 131 returns the flow to step S4A. This is to obtain a new sampling voltage and determine the decrease in the sampling voltage again.

When the falling edge detection unit 132 determines that the decrease in the sampling voltage is equal to or greater than the predetermined threshold (S5A: YES), it detects a falling edge (step S6A).

The drive control signal generator 131 determines the end of the on-period Ton when the falling edge is detected by the falling edge detector 132 (step S7A). This determines the on-period Ton.

The drive control signal generating unit 131 sets a duty ratio using the on-period Ton determined in step S7A and the unit period TU established in step S3A, and generates a drive control signal having the duty ratio (step S8A).

The drive control signal generating unit 131 determines whether to end the process (step S9A). One example of when the process ends is when the power supply to the dimmer 10 is turned off. When the drive control signal generating unit 131 determines not to end the process (S9A: NO), the flow returns to step S2A. This is to make a determination regarding the next unit period TU. When the drive control signal generating unit 131 determines to end the process (S9A: YES), the series of processes ends (end). Note that when the series of processes ends and the process is restarted, it may start from step S2A. This is because it is known that the dimmer 10 performs phase control in the opposite phase.

If the drive control signal generating unit 131 determines in step S1 that the sampling voltage is not in opposite phase (S1: NO), it determines whether the sampling voltage is equal to or greater than the on threshold (step S2B). This is because the dimmer 10 is in positive phase, and the on period Ton starts when the sampling voltage is equal to or greater than the on threshold. If the drive control signal generating unit 131 determines that the sampling voltage is not equal to or greater than the on threshold (S2B: NO), it repeatedly executes the process of step S2B until the sampling voltage is equal to or greater than the on threshold.

When the drive control signal generating unit 131 determines in step S2B that the sampling voltage is equal to or greater than the on threshold (S2B: YES), it determines the start point of the on period Ton and determines the unit period TU (step S3B). The determination of the unit period TU is not limited to the timing when the sampling voltage becomes equal to or greater than the on threshold, and may be determined at other timings. However, as an example, here, the unit period TU is determined at the timing when the sampling voltage becomes equal to or greater than the on threshold, as in FIG. 3(A).

The drive control signal generating unit 131 determines whether the sampled voltage is equal to or lower than the OFF threshold (step S4B). This is to detect the end point of the ON period Ton. If the drive control signal generating unit 131 determines that the sampled voltage is not equal to or lower than the OFF threshold (S4B: NO), it repeats the process of step S4B for the next sampled voltage.

When the drive control signal generator 131 determines that the sampling voltage is equal to or lower than the off threshold (S4B: YES), it determines the point at which the sampling voltage becomes equal to or lower than the off threshold as the end point of the on period Ton (step S5B).

The drive control signal generating unit 131 sets a duty ratio using the on-period Ton and unit period TU determined in step S3B, and generates a drive control signal having the duty ratio (step S6B).

The drive control signal generating unit 131 determines whether to end the process (step S7B). One example of ending the process is when the power supply to the dimmer 10 is turned off. If the drive control signal generating unit 131 determines not to end the process (S7B: NO), the flow returns to step S2B. This is to make a determination about the next unit period TU. If the drive control signal generating unit 131 determines to end the process (S7B: YES), the series of processes ends (end). Note that when restarting the process after ending the series of processes, it may start from step S2B. This is because it is known that the dimmer 10 performs phase control in the positive phase.

In operation 1, when the dimmer 10 performs phase control in a positive phase, the on-period Ton is determined using the on-threshold and off-threshold, and the unit period TU is determined using the start point of the on-period Ton.

On the other hand, when the dimmer 10 performs phase control in the opposite phase, the waveform may become blunted at the start of period T1 when the waveform starts to be cut due to the effects of the capacitance and inductance of the dimming control device 100A, and the end point of the on-period Ton may not be detected accurately. Therefore, the dimming control device 100A detects the falling edge of the waveform by determining whether the decrease in the current sampling voltage compared to the previous sampling voltage is equal to or greater than a predetermined threshold value, thereby enabling the end point of the on-period Ton and the unit period TU to be detected accurately.

Note that in operation 1, a case was described in which the falling edge of the waveform can be detected even if the waveform becomes blunt due to the effects of the capacitance, inductance, etc. of the dimming control device 100A at the start of period T1 when the waveform starts to be cut when the dimmer 10 performs phase control in the opposite phase. However, if the effects of the capacitance, inductance, etc. of the dimming control device 100A are greater, it may be difficult to detect the falling edge of the waveform. For example, if the waveform is blunted so much that the drop in the current sampling voltage relative to the previous sampling voltage does not exceed a predetermined threshold, it is possible to modify the waveform to have a falling edge by using the discharge circuit 150. The case in which the discharge circuit 150 is used in this way will be described next as operation 2.

<Operation 2>
Fig. 5 is a waveform diagram for explaining operation 2 of the dimming control device 100A. Fig. 5(A) and Fig. 5(B) show the operation in the case of the opposite phase. In Fig. 5(A) and Fig. 5(B), similarly to Fig. 3(A) and Fig. 3(B), the horizontal axis represents time, the vertical axis represents amplitude (voltage value), and the black circle represents the sampling voltage. The time between adjacent sampling voltages is the sampling period. Since the sampling voltage is based on the voltage full-wave rectified by the rectifier circuit 112, the amplitude of the waveform formed by the sampling voltages arranged in time series is 0V or more.

Figure 5 (A) shows the waveform when the discharge circuit 150 is off (disconnected state), and Figure 5 (B) shows the waveform when the discharge circuit 150 is on (connected state). In Figure 5 (A), the sine wave is shown by a dashed line within period T1, and the waveform obtained from the actual sampling voltage is shown by a solid line. In addition, the ideal waveform when the waveform is cut in the opposite phase is shown by a dashed line.

Due to the greater influence of the capacitance, inductance, etc. of the dimming control device 100A, the amplitude of the waveform shown by the solid line in period T1 as shown in FIG. 5(A) decreases more gradually than the waveform in operation 1.

In such a case, when the discharge circuit 150 is turned on within the period T1, the discharge circuit 150 connected to the power transmission line 102H on the output side of the rectifier circuit 112 is brought into a connected state, and the power transmission line 102H is connected to the ground potential point, so that a falling edge can be provided in the waveform of the sampling voltage within the period T1 as shown in FIG. 5(B).

Here, the timing to turn on the discharge circuit 150 is set as follows. The timing to turn on the discharge circuit 150 is when the time (TU-Tm) obtained by subtracting the margin time Tm from the unit period TU has elapsed since the point at which the drop in the current sampled voltage relative to the previous sampled voltage becomes equal to or exceeds a predetermined threshold and a falling edge is detected, as shown at time t2B in FIG. 5(B). Since the unit period TU is equal to the half period T/2, the time (TU-Tm) is equal to the time (T/2-Tm) obtained by subtracting the margin time Tm from the half period T/2.

If the duty ratio of the waveform of the sampled voltage has not changed from the previous unit period TU, it is considered that the waveform will be cut at the same timing in the current unit period TU. For this reason, the time (TU-Tm) is calculated by subtracting the margin time Tm from the unit period TU, and the discharge circuit 150 is turned on when the time (TU-Tm) has elapsed since the falling edge was detected.

The timing for turning off the discharge circuit 150 is when the sampling voltage becomes equal to or greater than the on threshold, because this is a timing that can be reliably determined.

When setting the timing to initially turn on the discharge circuit 150, for example, the discharge circuit 150 is always kept on during the first (first) unit period TU to obtain the time t1B at which the sampling voltage becomes equal to or greater than the on threshold, and during the second and subsequent unit periods TU, the timing to turn on the discharge circuit 150 can be set to the point in time at which a time (TU-Tm) has elapsed since the time t1B obtained during the previous unit period TU.

In addition, although the embodiment has been described in which the discharge circuit 150 is turned on when the time (TU-Tm) has elapsed since the falling edge was detected, if it is not necessary to provide a margin time, the discharge circuit 150 may be turned on when the unit period (TU) has elapsed since the falling edge was detected.

<Flowchart for implementing operation 2>
6 is a diagram showing a flowchart showing the process for realizing operation 2. This process is executed by the drive control signal generating unit 131, the falling edge detecting unit 132, and the switching control unit 133. The drive control signal generating unit 131 continues to acquire sampled voltages at a predetermined sampling period, and performs the following process on the latest sampled voltage (the current sampled voltage).

When the drive control signal generating unit 131 starts processing, it calculates the decrease in the current sampling voltage relative to the previous sampling voltage (step S11).

The falling edge detection unit 132 determines whether the decrease in the sampling voltage calculated by the drive control signal generation unit 131 in step S11 is equal to or greater than a predetermined threshold (step S12). This is to detect a falling edge.

When the falling edge detection unit 132 determines that the decrease in the sampling voltage is not equal to or greater than the predetermined threshold (S12: NO), the drive control signal generation unit 131 returns the flow to step S11. This is to obtain a new sampling voltage and determine the decrease in the sampling voltage again.

When the falling edge detection unit 132 determines that the decrease in the sampling voltage is equal to or greater than a predetermined threshold (S12: YES), the falling edge detection unit 132 detects a falling edge, and the drive control signal generation unit 131 starts counting the time (TU-Tm) obtained by subtracting the margin time Tm from the unit period TU (step S13).

The drive control signal generating unit 131 determines whether the time (TU-Tm) has elapsed (step S14). The drive control signal generating unit 131 repeatedly executes the process of step S14 until it determines that the time (TU-Tm) has elapsed.

When the drive control signal generating unit 131 determines that the time (TU-Tm) has elapsed (S14: YES), the switching control unit 133 turns on the discharge circuit 150 (step S15).

The drive control signal generating unit 131 determines whether the sampling voltage is equal to or greater than the on threshold (step S16). This is to determine the start point of the on period Ton. If the drive control signal generating unit 131 determines that the sampling voltage is not equal to or greater than the on threshold (S16: NO), it repeats the process of step S16.

When the drive control signal generating unit 131 determines that the sampling voltage is equal to or greater than the on-threshold voltage (S16: YES), the drive control signal generating unit 131 determines the start point of the on-period Ton, and the switching control unit 133 turns off the discharge circuit 150 (step S17).

The drive control signal generation unit 131 completes the series of processes (end).

As described above, the switching control unit 133 turns on the discharge circuit 150 when the time (TU-Tm) has elapsed since the waveform of the sampling voltage fell. The time (TU-Tm) has elapsed since the falling edge is immediately before the timing at which a falling edge occurs in the next unit period TU, so the waveform shown by the solid line in FIG. 5(A) can be changed to the waveform shown by the solid line in FIG. 5(B), resulting in a waveform in which the falling edge is easy to detect.

For this reason, even if the influence of the capacitance, inductance, etc. of the dimming control device 100A is greater and the waveform falls gradually during period T1 as shown by the solid line in Figure 5 (A), turning on the discharge circuit 150 makes it easier to detect the fall.

When the discharge circuit 150 is turned on and a waveform like that shown in FIG. 5(B) is obtained, the process described for operation 1 using FIG. 4 can be performed to detect the falling edge, set the duty ratio, and generate a drive control signal.

<Operation 3>
Fig. 7 is a diagram for explaining operation 3 of the dimming control device 100A. In Fig. 7, the horizontal axis represents time, which is expressed in unit periods in Fig. 7. The vertical axis represents the duty ratio of the drive control signal. Moreover, white circles represent the duty ratio for each unit period TU.

In digital control, the duty ratio may fluctuate (oscillate) slightly due to errors caused by deviations in each unit period TU of the measurement timing when the sampling voltage becomes equal to or greater than the on threshold, or other deviations. Fluctuations in the duty ratio cause fluctuations in the brightness of the LED 20. In operation 3, the fluctuations in the duty ratio are eliminated, and the duty ratio is updated when it should be updated.

The drive control signal generating unit 131 determines whether to update the duty ratio using a first threshold value (1%) and a second threshold value (0.5%). As another example, if the absolute value of the change in the duty ratio calculated in the current unit period TU from the duty ratio calculated in the previous unit period TU is equal to or greater than the first threshold value (1%), the drive control signal generating unit 131 updates the duty ratio to the value calculated in the current unit period TU. This is because if the absolute value of the change in the duty ratio is 1% or more, it is considered that this is not a fluctuation in the duty ratio, but rather a change of a magnitude that requires updating.

Furthermore, if the absolute values of the changes in the duty ratios calculated in three consecutive unit periods TU relative to the duty ratio calculated in the fourth unit period TU are all equal to or greater than the second threshold (0.5%), the drive control signal generating unit 131 updates the duty ratio to the value calculated in the current unit period TU. For small changes that are difficult to determine as a fluctuation in the duty ratio from a single fluctuation, the duty ratio is updated when it becomes equal to or greater than the second threshold (0.5%), which is smaller than the first threshold (1%), three consecutive times. In this way, hysteresis is provided using the second threshold (0.5%), which is different from the first threshold (1%), and the number of times that must be met to execute the update is also differentiated, eliminating fluctuations in the duty ratio and updating the duty ratio when it should be updated.

As an example, the second threshold (0.5%) is determined based on the duty ratios calculated over three consecutive unit periods TU, but this is not limited to three. If the absolute values of the changes in the duty ratios calculated over N (N is an integer of 2 or more) unit periods TU compared to the duty ratio calculated over the N+1 unit period TU are all equal to or greater than the second threshold (0.5%), the duty ratios may be updated to the value calculated over the current unit period TU. The value of N over the N unit periods TU can be changed depending on conditions, etc. Furthermore, the first threshold is not limited to 1%, and the second threshold is not limited to 0.5%. The first threshold and the second threshold can be changed depending on conditions, etc.

As shown in FIG. 7, for example, assume that the duty ratio increases from D1 to D2 from unit period TU1 to the next unit period TU2. In this case, the drive control signal generating unit 131 determines whether the change in the duty ratio D2-D1 is equal to or greater than the first threshold value (1%). If it is equal to or greater than the first threshold value (1%), the drive control signal generating unit 131 updates the duty ratio to D2 in unit period TU2. Thereafter, the duty ratio continues to increase, becoming D3 in unit period TU3 and D4 in unit period TU4. Since the changes in the duty ratio D3-D2 and D4-D3 are equal to or greater than the first threshold value (1%), the drive control signal generating unit 131 updates the duty ratio to D3 in unit period TU3 and to D4 in unit period TU4.

In addition, because the three consecutive duty ratios D5 to D7 in the unit periods TU5 to TU7 are equal to or greater than the second threshold value with respect to the duty ratio D4 in the unit period TU4, the drive control signal generating unit 131 updates the duty ratio to D7 in the unit period TU7. In this case, the drive control signal generating unit 131 may update the duty ratio to the average value of the three duty ratios D5 to D7.

In addition, from unit period TU11 to unit period TU14, the change in the duty ratio of unit period TU10 does not exceed the second threshold. In such a case, the drive control signal generation unit 131 does not update the duty ratio. By not updating the duty ratio even if the duty ratio fluctuates in this way, the drive control signal drives the current control element 118 stably.

In addition, in unit periods TU21 to TU24, the change in the duty ratio of unit period TU20 becomes equal to or greater than the second threshold in unit periods TU21 and TU23, but the duty ratio does not become equal to or greater than the second threshold for three consecutive unit periods TU, so the drive control signal generation unit 131 does not update the duty ratio. Even if the duty ratio fluctuates to the extent that it becomes equal to or greater than the second threshold in this manner, the duty ratio is not updated immediately, so that the current control element 118 can be driven stably.

Note that FIG. 7 describes a form in which, when the change in the duty ratio is positive, the drive control signal generating unit 131 determines whether to update (increase) the duty ratio using the first threshold (1%) and second threshold (0.5%), which are positive values. However, when the change in the duty ratio is negative, the drive control signal generating unit 131 may determine whether to update (decrease) the duty ratio using the first threshold (-1%) and second threshold (-0.5%), which are negative values.

<Flowchart for implementing operation 3>
8 is a diagram showing a flowchart showing the process for realizing operation 3. This process is executed by the drive control signal generating unit 131. The drive control signal generating unit 131 continues to acquire sampled voltages at a predetermined sampling period, and performs the following process on the latest sampled voltage (currently sampled voltage).

When the drive control signal generating unit 131 starts processing, it calculates the absolute value of the change in the duty ratio of the current unit period TU relative to the duty ratio of the previous unit period TU (step S21). This change is an example of the first change.

The drive control signal generator 131 determines whether the absolute value of the change calculated in step S21 is greater than or equal to the first threshold (step S22).

When the drive control signal generating unit 131 determines that the absolute value of the change is equal to or greater than the first threshold (S22: YES), it updates the duty ratio to the duty ratio calculated for the current unit period TU and generates a drive control signal (step S23).

When the drive control signal generating unit 131 finishes the process of step S23, it ends the series of processes (END). The drive control signal generating unit 131 repeatedly executes the flowchart shown in FIG. 8.

When the drive control signal generating unit 131 determines in step S22 that the absolute value of the change is not equal to or greater than the first threshold value (S22: NO), it determines whether the absolute values of the changes in the duty ratios calculated in the three consecutive unit periods TU up to the current unit period TU relative to the duty ratio calculated in the four unit periods TU prior thereto are all equal to or greater than the second threshold value (step S24). This change is an example of the second change.

When the drive control signal generating unit 131 determines that all of the duty ratios are equal to or greater than the second threshold (S24: YES), it advances the flow to step S23, updates the duty ratio to the duty ratio determined for the current unit period TU, and generates a drive control signal (step S23).

If the drive control signal generating unit 131 determines in step S24 that none of the signals are equal to or greater than the second threshold (S24: NO), the drive control signal generating unit 131 ends the series of processes (END). The drive control signal generating unit 131 repeatedly executes the flowchart shown in FIG. 8.

Therefore, for example, if the change in the duty ratio of the current unit period TU relative to the duty ratio of the previous unit period TU is less than the first threshold value once or twice consecutively, the duty ratio is not updated. Also, if the change in the duty ratio of the current unit period TU relative to the duty ratio of the previous unit period TU is less than the second threshold value, the duty ratio is not updated. In this case, no matter how many times in a row the duty ratio remains less than the second threshold value, the duty ratio is not updated.

As described above, in operation 3, if the absolute value of the change in the duty ratio is equal to or greater than the first threshold (1%), it is considered that this is not a fluctuation in the duty ratio, and the duty ratio is updated to the value determined for the current unit period TU. Also, if the absolute value of the change in the duty ratio is equal to or greater than the second threshold (0.5%) and it becomes equal to or greater than the second threshold (0.5%) three times in a row, the duty ratio is updated to eliminate the fluctuation in the duty ratio, and a drive control signal capable of stably driving the current control element 118 can be generated. As a result, fluctuations in the brightness of the LED 20 are suppressed, enabling stable illumination.

<Operation 4>
FIG. 9 is a diagram for explaining operation 4 of the dimming control device 100A. In FIG. 9, the horizontal axis represents temperature (° C.), and the vertical axis represents the current value (A) of the drive current output by the current control element 118. When the duty ratio is constant, it is desirable for the current control element 118 of the dimming device 100 to have a constant current value of the drive current at a target value by constant current control. However, in reality, the current value of the drive current changes depending on the temperature. More specifically, as an example, as shown by the dashed line in FIG. 9, the current value of the drive current decreases as the temperature increases. When the current value of the drive current decreases, the LED 20 becomes darker.

In operation 4, in order to correct such a decrease in the current value of the drive current to the target value, the signal correction unit 134 corrects the duty ratio of the drive control signal according to the temperature detected by the temperature detection unit 160, thereby correcting the current value of the drive current to the target value. As a result, the current control element 118 is subjected to constant current control when the duty ratio is constant.

Figure 10 is a diagram showing a correction table that indicates the correction value of the duty ratio. Figure 10 shows the input voltage, resistance value, temperature, and correction value. The input voltage is the voltage value of connection point 160A, and is input to the control device 130. The resistance value is the resistance value of thermistor 161 that corresponds to the input voltage. The temperature is the temperature that corresponds to the resistance value. The correction value is the correction value (%) of the duty ratio of the drive control signal that corresponds to the temperature.

For example, if the input voltage is 0.072V, the resistance value is 68.2367Ω, and if the resistance value is 68.2367Ω, the temperature is -20°C, and if the temperature is -20°C, the correction value is -4(%). Also, if the input voltage is 0.969V, the resistance value is 4.1609Ω, and if the resistance value is 4.1609Ω, the temperature is 50°C, and if the temperature is 50°C, the correction value is 3(%). If the correction value is -4(%), a correction value of -4(%) is added to the duty ratio of the drive control signal. If the correction value is 4(%), a correction value of 4(%) is added to the duty ratio of the drive control signal. The same applies for other input voltages. In this way, the duty ratio is corrected and the current value of the drive current is corrected to the target value.

In operation 4, even if the current value of the drive current output by the current control element 118 changes depending on the temperature, the current value of the drive current can be corrected to the target value by correcting the duty ratio of the drive control signal using the correction table in FIG. 10. Therefore, the current value of the drive current can be held at the target value (constant value) regardless of temperature changes, and the current control element 118 can be driven stably. As a result, the brightness of the LED 20 can be held constant, enabling stable illumination. Note that the temperature values and correction values shown in FIG. 10 are examples and can be changed depending on conditions, etc. Also, the input voltage and resistance values shown in FIG. 10 are examples. The correction table may include temperature values and correction values corresponding to various input voltages and resistance values.

<Operation 5>
11 is a diagram for explaining operation 5 of the dimming control device 100A. When starting to emit light of the LED 20 at a low output, since a sufficient amount of charge is not stored in the capacitor 118A, it takes time to charge the capacitor 118A, and the time required to emit the LED 20 may become long.

In operation 5, in such a case, in order to enable the LED 20 to emit light early, the increase processing unit 135 increases the duty ratio of the drive control signal so that the drive current increases when the output voltage detected by the output voltage detection unit 170 is equal to or lower than a predetermined voltage when the LED 20 starts to emit light.

In FIG. 11, the horizontal axis represents time (s), and the vertical axis represents the output voltage (V) detected by the output voltage detection unit 170. For example, if the duty ratio increase process according to operation 5 is not performed, when the output of the drive control signal starts at time t20, the output voltage increases gradually over time as shown by the dashed line, and it is at time t23 that the output voltage reaches the light-emitting voltage and the LED 20 emits light.

When the LED 20 starts to emit light, if the output voltage detected by the output voltage detection unit 170 is equal to or lower than a predetermined threshold voltage VTH, the increase processing unit 135 increases the duty ratio of the drive control signal so that the drive current increases. As a result, the output voltage increases rapidly from time t20 as shown by the solid line, and exceeds the threshold voltage VTH at time t21. When the output voltage exceeds the threshold voltage VTH, the increase processing unit 135 ends the increase processing, so that the output voltage increases with the same slope as the characteristic of the dashed line. When the emission voltage is reached at time t22, the LED 20 emits light.

In this way, according to operation 5, when the LED 20 starts emitting light at a low output, the increase processing unit 135 performs an increase process to increase the duty ratio of the drive control signal, thereby enabling the output voltage to be increased early and the LED 20 to emit light early.

<Operation 6>
Fig. 12 is a diagram for explaining operation 6 of the dimming control device 100A. In Fig. 12, the horizontal axis represents the output voltage (V) detected by the output voltage detection unit 170, and the vertical axis represents the duty ratio (%) of the drive control signal.

Operation 6 relates to a method for easily determining the duty ratio by suppressing deviations in the duty ratio that occur when the forward voltage applied to the LED 20 is changed when the LED 20 can emit light at multiple voltage values within the rated voltage range.

In operation 6, as an example, data is stored in memory 137 representing the duty ratio D11 of the drive control signal when the LED 20 is at the minimum voltage V1 at which it can emit light, and the duty ratio D12 of the drive control signal when the LED 20 is at the maximum voltage V2 at which it can emit light.

The data for the combination of the minimum voltage V1 and the duty ratio D11, and the combination of the maximum voltage V2 and the duty ratio D12 may be acquired during the manufacturing process of the dimming control device 100A and stored in the memory 137. The minimum voltage V1 and the duty ratio D11 are an example of a first voltage and a first duty ratio, and the maximum voltage V2 and the duty ratio D12 are an example of a second voltage and a second duty ratio.

As shown in FIG. 12, the output voltage and duty ratio are proportional between the minimum voltage V1 and duty ratio D1 and the maximum voltage V2 and duty ratio D12. Therefore, if the ratio ΔD/ΔV of the difference ΔD between the duty ratio D1 and duty ratio D12 to the difference ΔV between the minimum voltage V1 and the maximum voltage V2 is used as a correction coefficient, the duty ratio D13 at any output voltage V3 between the minimum voltage V1 and the maximum voltage V2 can be found by interpolation.

The interpolation processing unit 136 determines the duty ratio D13 of the drive control signal at the output voltage V3 detected by the output voltage detection unit 170 through an interpolation process using the ratio ΔD/ΔV as a correction coefficient. The drive control signal generation unit 131 generates the drive control signal using the duty ratio D13 determined by the interpolation processing unit 136.

This makes it possible to easily and quickly determine the duty ratio of the drive control signal at any output voltage V3, and to make the LED 20 emit light at various output voltages. For example, when multiple LEDs 20 are connected in series, the forward voltage for making the multiple LEDs 20 emit light differs from the forward voltage for making one LED 20 emit light, and the number of types of forward voltage increases. This is particularly useful when there are many types of forward voltages, as it is possible to make the LED 20 emit light at various output voltages.

Here, we have described a form in which data representing a combination of a minimum voltage V1 and a duty ratio D11, and a combination of a maximum voltage V2 and a duty ratio D12 is stored in memory 137. However, the combination is not limited to the combination of a minimum voltage V1 and a duty ratio D11, and the combination of a maximum voltage V2 and a duty ratio D12. If two duty ratios for two output voltages that give a slope equal to the slope obtained by the combination of the minimum voltage V1 and the duty ratio D11, and the combination of the maximum voltage V2 and the duty ratio D12 are stored in memory 137, the interpolation process can be performed in a similar manner.

＜Effects＞
As described above, in operation 1, when the dimmer 10 performs phase control in the opposite phase, the dimming control device 100A detects the falling edge of the waveform of the sampling voltage, and detects the end point of the on-period Ton and the unit period TU. When the dimmer 10 performs phase control in the normal phase, the dimming control device 100A determines the on-period Ton using the on-threshold value and the off-threshold value, and determines the unit period TU using the start point of the on-period Ton.

Therefore, it is possible to provide a dimming control device 100A and a dimming device 100 that are compatible with different types of dimmers 10.

In addition, in operation 1, when the dimmer 10 performs phase control in the opposite phase, the dimming control device 100A detects the falling edge of the waveform when the drop in the current sampling voltage relative to the previous sampling voltage is equal to or greater than a predetermined threshold, so that the falling edge can be detected more accurately based on the drop in the sampling voltage in the sampling period. Therefore, it is possible to provide a dimming control device 100A and a dimming device 100 that are compatible with different types of dimmers 10 and can more accurately detect the falling edge of the waveform when the dimmer 10 is in the opposite phase.

In addition, when the voltage acquired by the voltage divider circuit 113 is in positive phase, the drive control unit 130B sets the duty ratio by taking the point at which the sampling voltage becomes equal to or greater than the on threshold as the start point of the on period, so that the duty ratio can be set accurately even when the dimmer 10 performs phase control in positive phase.

The switching control unit 133 also includes a discharge circuit 150, and switches the discharge circuit 150 on when a unit period TU has elapsed since the falling edge is detected by the falling edge detection unit 132. Therefore, even when the influence of the capacitance, inductance, etc. of the dimming control device 100A is large, turning on the discharge circuit 150 makes it easier to detect the falling edge, and the duty ratio can be set accurately.

The switching control unit 133 also switches the discharge circuit 150 on when the time (TU-Tm) obtained by subtracting the margin time Tm from the unit period TU has elapsed since the falling edge was detected by the falling edge detection unit 132. Because the sampling voltage is acquired every sampling period, the start and end points of the unit period TU may deviate from the theoretical value. For this reason, by setting the timing at which the discharge circuit 150 is switched on earlier than the measured unit period TU by the margin time Tm, the discharge circuit 150 can be reliably turned on at the timing of the falling edge. As a result, the falling edge can be detected more reliably, and the duty ratio can be set more accurately.

The drive control signal generating unit 131 also updates the duty ratio when the absolute value of the change in the duty ratio of the current unit period TU relative to the duty ratio of the previous unit period TU is equal to or greater than the first threshold value. Therefore, when the change in the duty ratio is greater than the fluctuation in the duty ratio, the duty ratio can be reliably updated, and a drive control signal that more accurately reflects the fluctuation in the duty ratio can be generated.

The drive control signal generating unit 131 also updates the duty ratio when the absolute value of the change in the duty ratio of N consecutive unit periods TU (N is an integer equal to or greater than 2) relative to the duty ratio of the N+1 unit period TU prior thereto is equal to or greater than a second threshold value. Therefore, when the change in the duty ratio is equivalent to the fluctuation in the duty ratio, the duty ratio can be reliably updated, and a drive control signal that more accurately reflects the fluctuation in the duty ratio can be generated.

In addition, the drive control signal generating unit 131 does not update the duty ratio when the absolute value of the change in the duty ratio is less than the second threshold value. Therefore, when the change in the duty ratio is equivalent to the fluctuation in the duty ratio, the influence of the fluctuation in the duty ratio can be eliminated and the duty ratio can be kept constant, and the current control element 118 can be driven stably.

In addition, since the second threshold is smaller than the first threshold, providing hysteresis between the first and second thresholds makes it easier to eliminate fluctuations in the duty ratio, and allows the duty ratio to be updated when an update is required.

Furthermore, the drive control signal generating unit 131 does not update the duty ratio if the absolute value of the change in the duty ratio of the current unit period TU relative to the duty ratio of the previous unit period TU is less than the first threshold value, and the absolute value of the change in the duty ratio of N (N is an integer equal to or greater than 2) consecutive unit periods TU relative to the duty ratio of the N+1 unit period TU is not equal to or greater than the second threshold value. In other words, even if the duty ratio fluctuates once or twice consecutively, the duty ratio is not updated if the absolute value of the change is less than the first threshold value. Therefore, the duty ratio is updated when it should be updated, and the duty ratio can be maintained without updating when it should not be updated, and the current control element 118 can be driven stably.

The signal correction unit 134 also includes a temperature detection unit 160, and corrects the duty ratio of the drive control signal so as to correct the change in the drive current due to the change in temperature detected by the temperature detection unit 160. Therefore, even if the current value of the drive current output by the current control element 118 changes due to temperature, the current value of the drive current can be corrected to a target value, and the current control element 118 can be driven stably regardless of temperature changes.

The output voltage detection unit 170 is also included, and the increase processing unit 135 increases the duty ratio so that the drive current increases when the output voltage detected by the output voltage detection unit 170 is equal to or lower than the threshold voltage VTH when the LED 20 starts to emit light. Therefore, even when the LED 20 starts to emit light at a low output, the LED 20 can be made to emit light early.

The output voltage detection unit 170 is also included, and the interpolation processing unit 136 determines the duty ratio D13 at the output voltage V3 detected by the output voltage detection unit 170 through an interpolation process using the ratio ΔD/ΔV of the difference ΔD between the duty ratio D1 and the duty ratio D12 to the difference ΔV between the minimum voltage V1 and the maximum voltage V2 as a correction coefficient. This makes it possible to easily and quickly determine the duty ratio of the drive control signal at any output voltage V3, and to cause the LED 20 to emit light at various output voltages.

In the above, the embodiment in which the light emitter is an LED 20 has been described, but the light emitters that can be controlled by the dimming control device 100A and the dimming device 100 are not limited to LED 20. The dimming control device 100A and the dimming device 100 can also control light emitters other than LED 20 as long as they are current-controllable light emitters.

The above describes the dimming control device and dimming device as exemplary embodiments of the present invention, but the present invention is not limited to the specifically disclosed embodiments, and various modifications and variations are possible without departing from the scope of the claims.

10 Dimmer 20 LED
REFERENCE SIGNS LIST 100 Dimming device 100A Dimming control device 101A, 101B Terminal 111 Filter circuit 112 Rectifier circuit 113 Voltage divider circuit 114 PFC circuit 114A Smoothing capacitor 115 FET
116 Transformer 117 Rectifier circuit 118 Current control element 118A Capacitor 119A, 119B Output terminal 120 First driver 130 Control device 130IN Input terminal 130OUT Output terminal 130A ADC
130B Drive control section 131 Drive control signal generation section 132 Falling edge detection section 133 Switching control section 134 Signal correction section 135 Increase processing section 136 Interpolation processing section 137 Memory 140 Second driver 150 Discharge circuit 160 Temperature detection section 170 Output voltage detection section

Claims (13)

a voltage acquisition unit that acquires a rectified voltage obtained by rectifying an output of a dimmer that controls an AC voltage in a positive phase or a negative phase in a rectifier circuit;
A current control element for controlling a drive current supplied to the light emitter;
a drive control unit that controls the drive of the current control element in response to the voltage acquired by the voltage acquisition unit,
The drive control unit is
a drive control signal generation unit that sets a duty ratio in pulse width modulation of a drive control signal that drives the current control element in response to the voltage acquired by the voltage acquisition unit, and generates a drive control signal having the duty ratio;
a falling edge detection unit that detects a falling edge of the voltage when the voltage acquired by the voltage acquisition unit is in an opposite phase;
the drive control signal generation unit sets the duty ratio by setting a time point at which the falling edge is detected by the falling edge detection unit as an end time point of an ON period of the pulse width modulation;
the drive control unit samples the voltage acquired by the voltage acquisition unit at a predetermined sampling period;
The dimming control device , wherein the falling edge detection unit detects the falling edge when a decrease in the voltage during one sampling period becomes equal to or greater than a predetermined threshold value . 2 . The dimming control device according to claim 1 , wherein, when the voltage acquired by the voltage acquisition unit is in a positive phase , the drive control unit sets the duty ratio to a point at which the voltage becomes equal to or greater than an on-threshold value as a start point of an on-period of the pulse width modulation. a discharge circuit having a first terminal connected between the rectifier circuit and the voltage acquisition unit and a second terminal connected to a voltage reference point, the discharge circuit being capable of switching the first terminal and the second terminal between a connected state and a disconnected state;
3. The dimming control device according to claim 1, wherein the drive control unit further includes a switching control unit that switches the discharge circuit to the connected state when a period of a half cycle of the AC voltage has elapsed since the falling edge is detected by the falling edge detection unit. 4. The dimming control device according to claim 3, wherein the switching control unit switches the discharge circuit to the connected state when a period obtained by subtracting a predetermined margin time from a half cycle of the AC voltage has elapsed since the falling edge is detected by the falling edge detection unit. When a half cycle of the AC voltage is taken as a unit period, the drive control signal generation unit sets a ratio of the on-period in the unit period as the duty ratio,
5. The dimming control device according to claim 1, wherein when setting the duty ratio, the drive control signal generating unit updates the duty ratio when an absolute value of a first change in the duty ratio of the current unit period relative to the duty ratio of the unit period one before the drive control signal is equal to or greater than a first threshold value. 6. The dimming control device according to claim 5, wherein when setting the duty ratio of the drive control signal, the drive control signal generation unit updates the duty ratio when an absolute value of a second change in the duty ratio in N consecutive unit periods of the drive control signal (N is an integer equal to or greater than 2 ) relative to the duty ratio of the N+1 unit period previous thereto is equal to or greater than a second threshold value. The dimming control device according to claim 6 , wherein the drive control signal generation unit does not update the duty ratio when setting the duty ratio of the drive control signal if the second change in the drive control signal is less than a second threshold value. The dimming control device according to claim 6 , wherein the second threshold value is smaller than the first threshold value. The dimming control device according to claim 5 , wherein the drive control signal generating unit does not update the duty ratio when the first change is less than a first threshold. Further including a temperature detection unit for detecting an environmental temperature,
The dimming control device according to claim 1 , wherein the drive control unit further includes a signal correction unit that corrects a duty ratio of the drive control signal so as to correct a change in the drive current due to a change in the environmental temperature detected by the temperature detection unit. Further comprising an output voltage detection unit for detecting an output voltage applied to the light emitter,
The dimming control device according to any one of claims 1 to 10, wherein the drive control unit further has an increase processing unit that increases the duty ratio of the drive control signal so that the drive current increases when the output voltage detected by the output voltage detection unit is equal to or lower than a predetermined voltage when the light emitter starts to emit light. Further comprising an output voltage detection unit for detecting an output voltage applied to the light emitter,
The dimming control device according to any one of claims 1 to 10, further comprising an interpolation processing unit that calculates a duty ratio of the drive control signal when the drive current is the specified current at the output voltage detected by the output voltage detection unit by interpolation processing using a first duty ratio of the drive control signal when the output voltage applied to the light-emitting element is a first voltage and the drive current is a specified current, and a second duty ratio of the drive control signal when the output voltage applied to the light-emitting element is a second voltage and the drive current is the specified current. A dimming control device according to any one of claims 1 to 12 ,
The light emitter;
A dimming device comprising the dimmer.

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