JPH0251238B2 - - Google Patents

Description

Detailed Description of the Invention The present invention connects an AC control element such as a triax, a current limiting reactor such as a choke coil, and a discharge lamp such as a step-down mercury lamp in series to an AC power source, and adjusts the conduction phase angle of the AC control element. The present invention relates to an improvement in a discharge lamp lighting device configured to control a lamp current value every half cycle of an AC power source by appropriately adjusting it.

In the above-mentioned discharge lamp lighting device, part of the current control action by the current limiting reactor is performed by a semiconductor element such as an AC control element, so the entire device is small and lightweight, and the conduction phase of the AC control element is By adjusting the angle, the lamp current and lamp power of the discharge lamp can be appropriately controlled.
Recently, it is rapidly becoming popular as a lighting device for high-pressure discharge lamps such as high-pressure mercury lamps and high-pressure sodium lamps.

As an example of such a discharge lamp lighting device, as shown in FIG. Signals that change depending on the state, such as the voltage of the discharge lamp 4, the current limiting reactor 3
A reference voltage circuit 5 detects the voltage across the terminals of the AC control element 2 and the voltage at each terminal of the current limiting reactor 3, and rectifies the voltage to obtain a reference voltage.
and a timer circuit that charges a capacitor through a rectified voltage source every half cycle of the AC power supply voltage, and compares the charging voltage of the capacitor of the timer circuit 6 with the reference voltage of the reference voltage circuit 5 to find that both values match. A device has been proposed that includes a comparison pulse generation circuit 7 that generates a trigger pulse to make the AC control element 2 conductive when the AC control element 2 is activated. In such a lighting device, when the AC power supply 1 is turned on, the lighting circuit is connected to the second
When an AC voltage as shown in figure a is applied, figure 2 b
The circuit for detecting the terminal voltage of the AC control element 2 as shown in FIG.
As shown in Figure c, the capacitor of the timer circuit 6 begins to be charged. When this charging voltage matches the value of the reference voltage V _n obtained by step-down rectification of the voltage that is the sum of the terminal voltages of the AC control element 2 and the current limiting reactor 3 of the lighting circuit, the comparison pulse generation circuit 7 is activated. A trigger pulse as shown in FIG. 2d is generated and the AC control element 2 becomes conductive, so that a lamp current as shown in FIG. 2e flows.

Here, when the lamp power of the discharge lamp decreases due to a decrease in the power supply voltage, etc., the reference voltage V _n also decreases as shown by the broken line, so the trigger pulse generation point shifts forward and a large amount of lamp current flows, so the lamp power is kept constant.

Conventionally, in this type of lighting device, the capacitor of the timer circuit 6 is generally charged by means of step-down rectifying the AC power supply voltage and then charging the capacitor of the RC time constant circuit with a voltage source obtained through a constant voltage circuit. It is being FIG. 3 shows the change in the charging voltage of the capacitor when such a means is used. However, if the range of change in the reference voltage compared to the charging voltage is small, there is a drawback that sufficient current and power control cannot be achieved. That is, in FIG. 3, if the increase and decrease changes in the reference voltage V _n are V _n1 and V _n2 respectively, if the change in the charging voltage of the capacitor is sudden, the reference voltage V _n1 ,
The intersection with V _n2 , that is, the interval between the trigger pulse generation phase angles θ ₁ and θ ₂ also becomes narrower. Therefore, the generation phase angle of the trigger pulse does not change significantly, resulting in insufficient current control and power control.

In order to improve this, conventional methods have been used to amplify the change in the reference voltage to increase the change in the trigger pulse generation phase angle, or to start charging the capacitor from the zero potential of the power supply voltage and increase the time constant of the timer circuit. There has been a method of enlarging the capacitor and slowly charging the capacitor to magnify the change in the trigger pulse generation phase angle, but this method has the drawback of making the circuit complicated and increasing the cost economically.

The present invention was made in view of the above points, and when charging a capacitor of a timer circuit,
The capacitor is rapidly charged in the bypass circuit until the charging voltage reaches a certain value, and once the charging voltage reaches a certain value, the capacitor is slowly charged in the regular charging circuit. The drawbacks of the conventional device are eliminated by configuring the device so that the reference voltage of the reference voltage circuit matches the reference voltage of the reference voltage circuit.

FIG. 4 shows an example of a specific circuit of a discharge lamp lighting device embodying the present invention. In the figure, reference numeral 1 denotes an AC power source, to which a discharge lamp 2, a current limiting reactor 3, and an AC control element 4 are connected in series to form a lighting circuit. Reference numeral 5 denotes a high impedance element connected in parallel with the AC control element 4, which is connected for the purpose of preventing the discharge lamp from going out by passing a small amount of current through the lighting circuit even when the AC control element 4 is non-conducting. It is something.

An isolation transformer 6 is connected to both ends of the series circuit of the current limiting reactor 3 and the AC control element 4, and a rectifier circuit 7 is connected to the output side of the isolation transformer 6.
A programmable union transistor (hereinafter referred to as PCT) 11 is connected via voltage dividing resistors 8, 9, Zener diode 10, etc.
These constitute a reference voltage circuit. This reference voltage circuit detects the voltage obtained by adding the terminal voltages of the current limiting reactor 3 and the AC control element 4 of the lighting circuit, rectifies the voltage by step-down rectification, and outputs the reference voltage as a reference voltage.
It acts as a gate input for 11. Further, another isolation transformer 12 is connected to the AC power supply 1, and an RC time constant circuit of a resistor 16 and a capacitor 17 is connected to the output side of the isolation transformer 12 via a rectifier circuit 13, a resistor 14, and a zener diode 15. is connected to the capacitor 17, and both ends of the capacitor 17 are connected to the PUT 11, and these constitute a timer circuit. Furthermore, another isolation transformer 18 is connected to both ends of the AC control element 4 of the lighting circuit, and the zero potential point of the AC control element 4 is detected via a rectifier circuit 19 on the output side of the isolation transformer 18. A zero cross circuit 20 for sending out signals is connected. With this circuit configuration, the timer circuit steps down and rectifies the AC power supply voltage, charges the capacitor 17 from the zero potential point of the AC control element 4 of the lighting circuit with the voltage obtained through the constant voltage circuit, and adjusts the charging voltage. It acts as an input to the anode of PUT11. In addition to this circuit configuration, the voltage source of the timer circuit is connected via a constant voltage circuit consisting of a series circuit of a resistor 21 and a zener diode 22, and a capacitor charging bypass circuit consisting of a series circuit of a resistor 23 and a diode 24. is connected.

Next, the operation of the lighting device having such a circuit configuration will be explained. First, when the AC power supply 1 is turned on, the discharge lamp 2, the current limiting actuator 3, and the high impedance element 5 are turned on.
Voltage is applied to the discharge lamp 2 through the circuit, and the discharge lamp 2 starts. At the same time as the AC power supply 1 is turned on, voltage is applied to the timer circuit via the isolation transformer 12, and since the zero cross circuit 20 also operates, charging of the capacitor 17 starts from the zero potential point of the AC control element 4. In this case, the capacitor 17 is first rapidly charged through a bypass circuit consisting of a resistor 23 and a diode 24 to a constant voltage value set by a constant voltage circuit consisting of a resistor 21 and a zener diode 22. After reaching a certain voltage value, it is slowly charged through the resistor 16 by a regular circuit. Figure 5 shows capacitor 1 in this case.
7 shows the change in charging voltage. According to such means, the change in the charging voltage of the capacitor 17 rises sharply and linearly until it reaches a constant voltage value, but thereafter it draws a horizontal curve as shown in the figure. Therefore, if the reference voltage is set so that the reference voltage V _n and the charging voltage of the capacitor match in the region after reaching a certain voltage value, the reference voltage
Since the changes in the trigger pulse generation phases θ _{1 and θ 2 with respect to the changes in V n , V n1 and} V n2 also become large, sufficient current and power control is possible even if the change in the reference voltage is small.

Next, the operation of the discharge lamp lighting device according to the present invention during startup and stabilization of the discharge lamp will be described using voltage and current waveforms at the corners. Now, when the discharge lamp 2 is started by applying a power supply voltage as shown by the chain line in FIG. At this time, since the lamp voltage of the discharge lamp is approximately zero, the voltage obtained by adding the respective terminal voltages of the AC control element 4 and the current limiting reactor 3 becomes close to the power supply voltage, and the voltage on the gate side of the PUT 11 increases. Therefore, capacitor 17
is charged to a high voltage value and at that point PUT11
conducts and a trigger pulse is generated. This state is shown by the solid lines in Figure 6b and c. As is clear from this, the generation phase of the trigger pulse is quite late, so the lamp current at the time of starting also changes as shown by the solid line in Figure 6a. greatly controlled. In other words, the lamp current at startup can be reduced.

When the lamp voltage of the discharge lamp 2 gradually increases, the zero potential point of the AC control element 4 moves forward and at the same time, the voltage that is the sum of the terminal voltages of the AC control element 4 and the current limiting reactor 3 decreases. The charging voltage of No. 17 has the waveform shown by the broken line in FIG. 6b, and the phase angle at which the trigger pulse is generated moves forward as shown by the broken line in FIG.
The lamp current is limited as shown by the broken line in Figure a. Next, when the discharge lamp 2 reaches a stable state,
Since the lamp voltage is almost constant, if the power supply voltage increases, the AC control element 4 and the current limiting reactor 3
The voltage that is the sum of the terminal voltages increases again, and as shown by the solid lines in Figure 7b and c, the trigger pulse generation phase angle shifts backwards as shown by the broken lines, and the lamp current is limited by constant power. Characteristics are maintained.
On the other hand, when the power supply voltage decreases, the trigger pulse generation phase angle moves forward as shown by the dotted line due to the completely opposite operation to that described above, so that a large lamp current flows and constant power characteristics are always maintained.

In the circuit shown in Figure 4, a series circuit of a Zener diode 10 and a resistor 25 is inserted on the gate side of the PUT 11 to prevent excessive phase control against fluctuations in the positive power supply voltage and to maintain a good constant power. In addition, the reason why the pulse signal of PUT 11 is once amplified by transistor 26 is to ensure that a trigger signal can be obtained even in the event of a sudden voltage drop. . 27,
28 is a smoothing capacitor.

As is clear from the above description, the discharge lamp lighting device according to the present invention has the following advantages.

First, the capacitor of the timer circuit is rapidly charged through the bypass circuit until it reaches a certain voltage value, and thereafter it is slowly charged through the normal circuit.In this gradual charging region, the charging voltage of the capacitor becomes the standard. Since the reference voltage is set to match the voltage, reliable current and power control can be performed even if the amount of change in the reference voltage is small. For example, compared to the case where a capacitor of a timer circuit is charged only by a normal charging circuit, in the case of the present invention, the trigger pulse generation phase angle can be changed about twice as much, so a special amplification circuit is used. There is an advantage that you can do without it.

Next, since the voltage obtained by adding the terminal voltages of the AC control element of the lighting circuit and the current limiting reactor is step-down rectified and used as the reference voltage, it is possible to delay the generation phase angle of the trigger pulse at the time of starting the discharge lamp.
Excessive lamp current at startup can be reduced.

Furthermore, in configuring the circuit, in order to rapidly charge the capacitor of the timer circuit, it is only necessary to add a bypass circuit consisting of a series circuit of a resistor and a diode, so the configuration is simple, easy to adjust, and compact. It has great economic value as well as technical value such as being able to reduce costs, and has great industrial utility value.

[Brief explanation of the drawing]

Figure 1 is a basic circuit diagram of a conventional discharge lamp lighting device, Figure 2 is a current/voltage waveform diagram of each part during operation of the device, and Figure 3 is a change in capacitor charging voltage in the device's timer circuit. 4 is a specific circuit diagram of the discharge lamp lighting device according to the present invention, FIG. 5 is a curve diagram of changes in charging voltage of a capacitor in the timer circuit of the device, and FIG. 6 is a discharge lamp starting device of the same device. FIG. 7 is a current/voltage waveform diagram of each part of the device when the discharge lamp is stable. In FIG. 4, 1... AC power supply, 2... Discharge lamp, 3... Current limiting reactor, 4... AC control element, 6... Insulation transformer for reference voltage circuit, 11...
...PUT, 12...Isolation transformer for timer circuit,
17...Timer circuit capacitor, 20...Zero cross circuit, 23...Resistor, 24...Diode.

Claims (1)

[Claims] 1. A lighting circuit including an AC control element, a current limiting reactor, and a discharge lamp connected in series to an AC power supply, and a signal that changes depending on the operating state of the lighting circuit and a reference voltage. A reference voltage circuit that charges and discharges a capacitor through a rectified voltage source every half cycle of the AC power supply voltage, and a timer circuit that charges and discharges a capacitor through a rectified voltage source every half cycle of the AC power supply voltage, and compares the charging voltage of the capacitor of the timer circuit with the reference voltage and finds that the values match. and a comparison pulse generation circuit that generates a trigger pulse that makes an AC control element conductive at a certain point in time. A bypass charging circuit is connected to the capacitor of the RC time constant circuit via another constant voltage circuit, and the capacitor is charged through the bypass charging circuit until its charging voltage reaches a certain value. and a reference voltage is set so as to match a reference voltage of a reference voltage circuit in a region where the charging voltage exceeds the certain value. 2. In the discharge lamp lighting device according to claim 1, the reference voltage circuit detects a voltage that is the sum of the terminal voltages of the AC control element and the current limiting reactor of the lighting circuit, and rectifies the voltage to provide the reference voltage. A discharge lamp lighting device characterized in that it is configured to. 3 In the discharge lamp lighting device according to claim 1, the timer circuit steps down and rectifies the AC power supply voltage and then uses the voltage obtained through the constant voltage circuit to reduce the voltage to zero obtained from the terminal voltage of the AC control element of the lighting circuit. A discharge lamp lighting device characterized by being configured to charge a capacitor from a potential. 4. In the discharge lamp lighting device according to claim 1, the bypass charging circuit for charging the capacitor of the timer circuit has a constant voltage lower than the voltage obtained through the constant voltage circuit after step-down rectification of the AC power supply voltage. A discharge lamp lighting device characterized in that a capacitor is charged via a diode from another constant voltage circuit for setting a value.