JP7636717B2 - Lighting devices and lighting fixtures - Google Patents

Description

Embodiments of the present invention relate to lighting devices and lighting fixtures.

There is known a lighting fixture that includes a light-emitting element such as an LED, and a lighting device that supplies a direct current to the light-emitting element to light the light-emitting element. The lighting device monitors the average current or average voltage of the light-emitting element and compares it with a reference value, thereby performing feedback control so that a substantially constant direct current corresponding to the reference value flows through the light-emitting element.

In this case, if the average current and average voltage of the light-emitting element are small, it may be difficult to monitor the average current and average voltage, making it difficult to perform appropriate feedback control.

For this reason, it is desirable for lighting devices and lighting fixtures to be able to perform feedback control more appropriately even when the average current and average voltage of the light-emitting element are small.

JP 2008-310963 A

Embodiments of the present invention provide a lighting device and a lighting fixture that can perform feedback control more appropriately even when the average current and average voltage of the light-emitting element are small.

According to an embodiment, the present invention includes a power conversion unit that converts a first DC power into a second DC power and supplies the second DC power to a light-emitting element to light the light-emitting element, a control circuit that controls conversion from the first DC power to the second DC power by the power conversion unit, a first voltage detection circuit that detects a DC input voltage value of the first DC power supplied to the power conversion unit, and a second voltage detection circuit that detects a load voltage value of the second DC power supplied from the power conversion unit to the light-emitting element , the power conversion unit having a switching element, an inductor, and an output capacitor, The first DC power is converted into the second DC power by switching an element, and the control circuit calculates a calculated value of a load current based on the DC input voltage value detected by the first voltage detection circuit and the load voltage value detected by the second voltage detection circuit, compares the calculated value of the load current obtained by calculation with a reference value, and performs feedback control to control the switching of the switching element so that the load current of a magnitude corresponding to the reference value flows to the light-emitting element based on the comparison result of the calculated value of the load current with the reference value.

To provide a lighting device and lighting fixture that can perform more appropriate feedback control even when the average current and average voltage of the light-emitting element are small.

1 is a block diagram illustrating a lighting device and a lighting fixture according to an embodiment.

Each embodiment will be described below with reference to the drawings.
In addition, the drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as those in reality. Even when the same part is shown, the dimensions and ratios of each part may be different depending on the drawing.
In this specification and each drawing, elements similar to those described above with reference to the previous drawings are given the same reference numerals and detailed descriptions thereof will be omitted as appropriate.

FIG. 1 is a block diagram illustrating a lighting device and a lighting fixture according to an embodiment.
1, the lighting fixture 2 includes a light-emitting element 4 and a lighting device 10. The lighting device 10 is electrically connected to a power source PS. The lighting device 10 converts the power supplied from the power source PS into DC power suitable for the light-emitting element 4, and supplies the converted DC power to the light-emitting element 4, thereby lighting the light-emitting element 4.

The lighting device 10 is supplied with AC power from, for example, a power source PS. The power source PS is, for example, a commercial power source. The AC voltage of the AC power supplied from the power source PS is, for example, 100 V to 242 V (effective value). The power source PS may be, for example, a private generator. The lighting device 10 converts the AC power supplied from the power source PS into DC power corresponding to the light-emitting element 4. Note that the power supplied to the lighting device 10 is not limited to AC power, and may be DC power, etc. The following description will be given taking as an example a case where AC power is supplied to the lighting device 10.

For example, a light emitting diode (LED) is used as the light emitting element 4. The light emitting element 4 may be, for example, an organic light emitting diode (OLED), an inorganic electroluminescence light emitting element, an organic electroluminescence light emitting element, or other electroluminescence type light emitting element. In the following, the light emitting element 4 will be described as an LED. Note that the light emitting element 4 is not limited to a single element, and may be, for example, a plurality of elements connected in series.

The lighting device 10 includes a power conversion unit 12 and a control circuit 14. The power conversion unit 12 converts a first DC power into a second DC power, and supplies the converted second DC power to the light-emitting element 4. The control circuit 14 controls the conversion from the first DC power to the second DC power by the power conversion unit 12. The control circuit 14 is, for example, formed as a chip. The control circuit 14 is, for example, a control IC (Integrated Circuit) formed as a single chip. However, the control circuit 14 is not limited to this, and may be formed by combining multiple elements.

The lighting device 10 further includes, for example, a rectifier circuit 20, a high-frequency removal capacitor 22, a power factor correction circuit 24, and a smoothing capacitor 26. The rectifier circuit 20, the high-frequency removal capacitor 22, the power factor correction circuit 24, and the smoothing capacitor 26 can be omitted, for example, when DC power (first DC power) is supplied to the lighting device 10 from the power source PS. Each of these components is provided in the lighting device 10 as necessary and can be omitted.

The rectifier circuit 20 rectifies the AC power input from the power source PS and converts it into rectified power. For example, a diode bridge combining four rectifier elements is used for the rectifier circuit 20. In other words, the rectifier circuit 20 is a full-wave rectifier. The rectified power is, for example, pulsating power.

The rectifier circuit 20 has a pair of input terminals 20a, 20b, a high potential output terminal 20c, and a low potential output terminal 20d. The input terminals 20a, 20b are electrically connected to a power source PS. The rectifier circuit 20 converts AC power input via the input terminals 20a, 20b into rectified power, and outputs it from the high potential output terminal 20c and the low potential output terminal 20d. The potential of the low potential output terminal 20d is set to a reference potential (e.g., ground potential). The potential of the high potential output terminal 20c is set to a potential higher than the potential of the low potential output terminal 20d.

The rectifier circuit 20 may be a half-wave rectifier or the like. The rectified voltage may be a full-wave rectified pulsating current or a half-wave rectified pulsating current. For example, a Schottky barrier diode is used for the rectifier circuit 20. This makes it possible to obtain, for example, good responsiveness.

The high-frequency removal capacitor 22 smoothes the rectified high-frequency power, converting it into pulsating power.

The power factor correction circuit 24 suppresses the generation of harmonics that are integer multiples of the power supply frequency in the input current of the rectifier circuit 20. In this way, the power factor correction circuit 24 improves the power factor of the input power.

The power factor correction circuit 24 includes, for example, a switching element 31, an inductor 32, and a diode 33. The switching element 31 has electrodes 31a to 31c. One end of the inductor 32 is electrically connected to the high potential output terminal 20c. The other end of the inductor 32 is electrically connected to the electrode 31a. The electrode 31b is electrically connected to the low potential output terminal 20d. The anode of the diode 33 is electrically connected to the electrode 31a. The cathode of the diode 33 is electrically connected to one end of the smoothing capacitor 26. The other end of the smoothing capacitor 26 is electrically connected to the low potential output terminal 20d.

That is, in this example, the power factor correction circuit 24 is a boost chopper circuit. The power factor correction circuit 24 converts, for example, the AC voltage of the power source PS of 100 V to 242 V (effective value) into a DC voltage of 420 V. The power factor correction circuit 24 is not limited to this, and may be any circuit that can improve the power factor of the input power.

The electrode 31c is electrically connected to the control circuit 14. The electrode 31c is a so-called control electrode. The switching element 31 switches in response to a signal from the control circuit 14. The power factor correction circuit 24 improves the power factor, for example, by switching the switching element 31 and bringing the input current closer to a half-sine wave.

The switching element 31 is, for example, an n-channel FET. For example, the electrode 31a is the drain, the electrode 31b is the source, and the electrode 31c is the gate. The switching element 31 may be, for example, a p-channel FET or a bipolar transistor.

The smoothing capacitor 26 converts the power factor corrected power into a first DC power by smoothing the output voltage after the power factor correction. The smoothing capacitor 26 supplies the first DC power to the power conversion unit 12.

The power conversion unit 12 has a first input terminal 12a, a second input terminal 12b, a first output terminal 12c, and a second output terminal 12d. The first input terminal 12a is electrically connected to one end of the high potential side of the smoothing capacitor 26. The second input terminal 12b is electrically connected to the low potential output terminal 20d. This allows the power conversion unit 12 to be supplied with the first DC power.

The power conversion unit 12 has, for example, a switching element 35, a diode 36, an inductor 37, and an output capacitor 38. The switching element 35 has electrodes 35a to 35c. The electrode 35a is electrically connected to the first input terminal 12a. The electrode 35b is electrically connected to the cathode of the diode 36. The anode of the diode 36 is electrically connected to the low-potential output terminal 20d. One end of the inductor 37 is electrically connected to the electrode 35b. The other end of the inductor 37 is electrically connected to the first output terminal 12c. The second output terminal 12d is electrically connected to the low-potential output terminal 20d (second input terminal 12b).

The output capacitor 38 has a first electrode 38a and a second electrode 38b. The first electrode 38a is electrically connected to the first output terminal 12c. The second electrode 38b is electrically connected to the second output terminal 12d. The output capacitor 38 is connected in parallel between the first output terminal 12c and the second output terminal 12d. The output capacitor 38 smoothes the current flowing between the electrodes 35a, 35b of the switching element 35 by switching the switching element 35. As a result, the second DC power is output from the first output terminal 12c and the second output terminal 12d.

In this example, the power conversion unit 12 is a step-down chopper circuit. The power conversion unit 12 converts the first DC power into the second DC power by stepping down the voltage of the input power. The power conversion unit 12 converts, for example, the DC voltage of the power factor correction circuit 24 of 420 V into a DC voltage of 50 V to 300 V. The power conversion unit 12 is, for example, a constant current circuit. The power conversion unit 12 supplies, for example, a substantially constant DC current to the light-emitting element 4.

The first output terminal 12c is a high-potential output terminal, and the second output terminal 12d is a low-potential output terminal. The potential of the first output terminal 12c is higher than the potential of the second output terminal 12d. The potential of the first electrode 38a is set higher than the potential of the second electrode 38b. The first electrode 38a is, for example, an anode, and the second electrode 38b is, for example, a cathode. Conversely, the potential of the second output terminal 12d may be higher than the potential of the first output terminal 12c.

The switching element 35 is, for example, an n-channel FET. For example, the electrode 35a is the drain, the electrode 35b is the source, and the electrode 35c is the gate. The switching element 35 may be, for example, a p-channel FET or a bipolar transistor.

The configuration of the power conversion unit 12 is not limited to the above circuit. The power conversion unit 12 may be any circuit that has at least one switching element, an inductor, and an output capacitor, and is capable of converting the first DC power into the second DC power by switching the switching element.

The control circuit 14 is electrically connected to the electrode 31c of the switching element 31. The electrode 31c is a so-called control electrode. The control circuit 14 controls the switching of the switching element 31. That is, the control circuit 14 switches the switching element 31 on and off. The control circuit 14 switches the switching element 31 on and off by a voltage (control signal) input to the electrode 31c. The control circuit 14 controls the improvement of the power factor of the input power by the power factor improvement circuit 24, for example, by switching the switching element 31.

The control circuit 14 is electrically connected to the electrode 35c of the switching element 35. The electrode 35c is a so-called control electrode. The control circuit 14 controls the switching of the switching element 35. That is, the control circuit 14 switches the switching element 35 on and off. The control circuit 14 switches the switching element 35 on and off by a voltage (control signal) input to the electrode 35c. The control circuit 14 generates a DC voltage between the electrodes 38a, 38b of the output capacitor 38, for example, by switching the switching element 35. As a result, the second DC power is supplied from the power conversion unit 12 to the light-emitting element 4.

The control circuit 14 stops the supply of the second DC power from the power conversion unit 12 to the light-emitting element 4, for example, by turning off the switching element 35. The control circuit 14 also changes the voltage value and current value of the second DC power supplied to the light-emitting element 4, for example, by changing the on/off cycle (duty ratio) of the switching element 35.

The off state of the switching element 31 is, for example, a state in which substantially no current flows between the electrodes 31a and 31b, which are the main electrodes. In the off state, for example, a weak current that does not affect the operation of the power factor correction circuit 24 may flow between the electrodes 31a and 31b. In other words, the on state of the switching element 31 is a first state in which a current flows between the electrodes 31a and 31b, and the off state is a second state in which the current flowing between the electrodes 31a and 31b is smaller than that in the first state. The on and off states of the switching element 35 are similar to those of the switching element 31.

The lighting device 10 further includes a current detection circuit 40, a first voltage detection circuit 42, and a second voltage detection circuit 44. The current detection circuit 40 is electrically connected between the second input terminal 12b and the second electrode 38b of the output capacitor 38. In other words, the current detection circuit 40 is electrically connected between the anode of the diode 36 and the second electrode 38b of the output capacitor 38. The second output terminal 13d is electrically connected to the low potential output terminal 20d via the current detection circuit 40.

The current detection circuit 40 detects the winding current flowing through the inductor 37. In other words, the current detection circuit 40 detects the unsmoothed current flowing through the switching element 35 and the inductor 37. The current detection circuit 40 is connected to the control circuit 14. The current detection circuit 40 inputs the detection result of the winding current flowing through the inductor 37 to the control circuit 14. As a result, the control circuit 14 detects the winding current flowing through the inductor 37 based on the detection result of the current detection circuit 40. In addition, the control circuit 14 detects the load current flowing through the light-emitting element 4 based on the average current of the winding current flowing through the inductor 37. In other words, the current detection circuit 40 detects the winding current flowing through the inductor 37 and the load current flowing through the light-emitting element 4.

The first voltage detection circuit 42 is electrically connected to one end of the smoothing capacitor 26. As a result, the first voltage detection circuit 42 detects the DC input voltage value of the first DC power supplied to the power conversion unit 12. The first voltage detection circuit 42 is connected to the control circuit 14. The first voltage detection circuit 42 inputs the detection result of the DC input voltage value to the control circuit 14.

The second voltage detection circuit 44 is electrically connected to the first electrode 38a of the output capacitor 38. As a result, the second voltage detection circuit 44 detects the load voltage value of the second DC power supplied from the power conversion unit 12 to the light-emitting element 4. The second voltage detection circuit 44 is connected to the control circuit 14. The second voltage detection circuit 44 inputs the detection result of the load voltage value to the control circuit 14.

The control circuit 14 compares the load current detection value detected by the current detection circuit 40 with a reference value. Based on the comparison result between the load current detection value and the reference value, the control circuit 14 generates a control signal for controlling the switching of the switching element 35 so that a load current of a magnitude corresponding to the reference value flows through the light-emitting element 4, and inputs the control signal to the electrode 35c of the switching element 35.

In this way, the control circuit 14 feedback controls the operation of the power conversion unit 12 based on the load current detection value detected by the current detection circuit 40. As a result, the control circuit 14 controls the operation of the power conversion unit 12 so that the magnitude of the load current flowing through the light-emitting element 4 is substantially constant according to the reference value.

The control circuit 14 also receives a dimming signal representing the dimming degree of the light-emitting element 4, for example, from an external wall switch. The control circuit 14 receives an input of a dimming signal representing the dimming degree of the light-emitting element 4. The dimming signal representing the dimming degree is, for example, a PWM signal with a duty ratio according to the dimming degree. The dimming signal may be, for example, an AC voltage whose conduction angle is controlled by a dimmer or the like. The dimming signal may be input to the control circuit 14 in response to the operation of an operation unit provided in the lighting device 10.

The control circuit 14 changes the reference value of the feedback control based on the input dimming signal. The control circuit 14 sets the reference value corresponding to the dimming degree by, for example, multiplying the reference value of 100% dimming degree by a coefficient corresponding to the dimming degree. For example, when the dimming degree is set to 70% in the dimming signal, the control circuit 14 sets the reference value corresponding to 70% dimming degree by multiplying the reference value of 100% dimming degree by 0.7. As a result, the light-emitting element 4 is dimmed at a dimming degree according to the dimming signal. The brightness of the light-emitting element 4 is controlled according to the dimming signal. In this way, the control circuit 14 changes the load current value of the second DC power supplied from the power conversion unit 12 to the light-emitting element 4 according to the dimming signal input from the outside.

When the dimming level indicated by the dimming signal is equal to or greater than a predetermined value, the control circuit 14 compares the load current detection value detected by the current detection circuit 40 with a reference value as described above, and based on the comparison result between the load current detection value and the reference value, generates a control signal for controlling the switching of the switching element 35 so that a load current of a magnitude corresponding to the reference value flows through the light-emitting element 4, and inputs the control signal to the electrode 35c of the switching element 35.

On the other hand, when the dimming level indicated by the dimming signal is less than a predetermined value, the control circuit 14 calculates the load current flowing through the light-emitting element 4. The control circuit 14 then compares the calculated load current value with a reference value, and based on the comparison result between the calculated load current value and the reference value, generates a control signal for controlling the switching of the switching element 35 so that a load current of a magnitude corresponding to the reference value flows through the light-emitting element 4, and inputs the control signal to the electrode 35c of the switching element 35.

For example, when the dimming level indicated by the dimming signal is 5% or more, the control circuit 14 controls the switching of the switching element 35 based on the result of comparing the detected value of the load current with a reference value, and when the dimming level indicated by the dimming signal is less than 5%, the control circuit 14 controls the switching of the switching element 35 based on the result of comparing the calculated value of the load current with a reference value. However, the predetermined value is not limited to 5% and may be any dimming level.

The control circuit 14 calculates the load current value based on, for example, the DC input voltage value detected by the first voltage detection circuit 42 and the load voltage value detected by the second voltage detection circuit 44.

The control circuit 14 may further include, for example, at least one of the inductance value of the inductor 37, the winding current value of the inductor 37 detected by the current detection circuit 40, the switching frequency of the switching element 35, and the on/off duty ratio of the switching element 35 in the calculation of the calculated value of the load current. Note that information on the inductance value of the inductor 37 may be stored in advance in the control circuit 14.

The control circuit 14 uses the DC input voltage value and the load voltage value, and further uses at least one of the inductance value of the inductor 37, the winding current value of the inductor 37, the switching frequency of the switching element 35, and the duty ratio of the switching element 35 to calculate the load current. This allows the load current to be calculated more appropriately.

For example, the load current is calculated using the DC input voltage value, the load voltage value, the inductance value of the inductor 37, the winding current value of the inductor 37, the switching frequency of the switching element 35, and the duty ratio of the switching element 35. This allows the load current to be calculated more appropriately.

As described above, in the lighting device 10 according to this embodiment, the control circuit 14 compares the load current calculated by calculation to flow through the light-emitting element 4 with a reference value, and based on the comparison result between the load current calculation value and the reference value, performs feedback control to control the switching of the switching element 35 so that a load current of a magnitude corresponding to the reference value flows through the light-emitting element 4. In addition, a dimming signal representing the dimming level of the light-emitting element 4 is input, and the feedback control reference value is changed based on the input dimming signal, thereby lighting the light-emitting element 4 at a brightness corresponding to the dimming level represented by the dimming signal.

This allows for more appropriate feedback control even when the average current and average voltage of the light-emitting element 4 become small and it becomes difficult for the current detection circuit 40 to detect the load current flowing through the light-emitting element 4. For example, feedback control can be performed more appropriately even on the lower limit side of dimming. In this way, by controlling through calculations, feedback control can be performed more appropriately even in the microcurrent region.

In addition, in the lighting device 10, the control circuit 14 controls the switching of the switching element 35 based on the result of comparing the detected value of the load current with a reference value when the dimming level represented by the dimming signal is equal to or greater than a predetermined value, and controls the switching of the switching element 35 based on the result of comparing the calculated value of the load current with a reference value when the dimming level represented by the dimming signal is less than the predetermined value.

In this way, in parts where the load current amount is relatively large and the magnitude of the load current can be properly detected by the current detection circuit 40, feedback control is performed based on the detection value of the load current detected by the current detection circuit 40, thereby making it possible to reduce the error with the magnitude of the load current actually flowing through the light-emitting element 4 and perform more appropriate feedback control.

In addition, for example, in areas where the load current is relatively large, the computational load of the control circuit 14 can be reduced by performing feedback control based on the load current detection value detected by the current detection circuit 40. For example, in areas where the load current is relatively large, the increase in power consumption can be suppressed.

The control circuit 14 may perform feedback control based on the calculated value of the load current, for example, in the entire dimming range from 0% to 100%. In this case, the current detection circuit 40 may be omitted. The lighting device 10 does not necessarily have to perform dimming control. For example, when a substantially constant current is supplied to the light-emitting element 4 to light the light-emitting element 4 at a substantially constant brightness, if the average current and average voltage of the light-emitting element 4 are small and it is difficult to perform appropriate feedback control, feedback control based on the calculated value of the load current may be performed.

In addition, in the lighting device 10, the control circuit 14 is a control IC integrated into one chip. In this way, by integrating the control circuit 14, which performs complex calculations, into a chip, it is possible to prevent the lighting device 10 from becoming larger.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

2...Lighting fixture, 4...Light-emitting element, 10...Lighting device, 12...Power conversion section, 14...Control circuit, 20...Rectifier circuit, 22...High frequency removal capacitor, 24...Power factor improvement circuit, 26...Smoothing capacitor, 31...Switching element, 32...Inductor, 33...Diode, 35...Switching element, 36...Diode, 37...Inductor, 38...Output capacitor, 40...Current detection circuit, 42...First voltage detection circuit, 44...Second voltage detection circuit, PS...Power supply

Claims (6)

a power conversion unit that converts a first DC power into a second DC power and supplies the second DC power to a light-emitting element to light up the light-emitting element;
a control circuit that controls conversion from the first DC power to the second DC power by the power conversion unit;
a first voltage detection circuit that detects a DC input voltage value of the first DC power supplied to the power conversion unit;
a second voltage detection circuit that detects a load voltage value of the second DC power supplied from the power conversion unit to the light emitting element;
Equipped with
the power conversion unit includes a switching element, an inductor, and an output capacitor, and converts the first DC power into the second DC power by switching the switching element;
The control circuit calculates a load current value based on the DC input voltage value detected by the first voltage detection circuit and the load voltage value detected by the second voltage detection circuit, compares the calculated load current value obtained by the calculation with a reference value, and performs feedback control to control the switching of the switching element so that the load current of a magnitude corresponding to the reference value flows to the light-emitting element based on the comparison result between the calculated load current value and the reference value. 2. The lighting device according to claim 1, wherein the control circuit further includes at least one of an inductance value of the inductor, a winding current value of the inductor, a switching frequency of the switching element, and an on/off duty ratio of the switching element in the calculation of the calculated value of the load current. The lighting device according to claim 1 or 2, wherein the control circuit receives an input of a dimming signal representing a dimming degree of the light-emitting element, and changes the reference value of the feedback control based on the input dimming signal, thereby lighting the light- emitting element at a brightness corresponding to the dimming degree represented by the dimming signal. a current detection circuit for detecting the load current flowing through the light emitting element;
The lighting device according to claim 3, wherein, when the dimming degree represented by the dimming signal is equal to or greater than a predetermined value, the control circuit compares the detection value of the load current detected by the current detection circuit with the reference value, and controls the switching of the switching element based on the comparison result between the detection value of the load current and the reference value so that the load current of a magnitude corresponding to the reference value flows to the light-emitting element; and, when the dimming degree represented by the dimming signal is less than the predetermined value, the control circuit compares the calculated value of the load current obtained by calculation with the reference value, and controls the switching of the switching element based on the comparison result between the calculated value of the load current and the reference value so that the load current of a magnitude corresponding to the reference value flows to the light-emitting element. 5. The lighting device according to claim 1 , wherein the control circuit is a control IC formed on a single chip. A light-emitting element;
A lighting device according to any one of claims 1 to 5 ,
Lighting fixtures equipped with.

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