JPH0327358Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention This invention relates to a discharge lamp lighting device that dims a discharge lamp by controlling the phase of a commercial AC power supply voltage.

Prior Art FIG. 1 shows a conventional DC power supply circuit diagram disclosed in Utility Model Application Publication No. 57-130542, in which a plurality of smoothing capacitors 3, 4 are connected between the output terminals of a rectifier 2 that rectifies a commercial AC power supply 1. , 5 (in this case, the number of capacitors is three) and the smoothing capacitors 3, 4, and 5 are connected in series with diodes 6, 7 in the charging direction and a charging current limiting coil 8. In this case, diode 6 is connected between smoothing capacitors 3 and 4, and diode 7 is connected between smoothing capacitors 4 and 5, respectively. Then, a diode 11 in the discharge direction is connected to the terminal of the smoothing capacitor 3 that is not directly connected to the output terminal of the rectifier 2, and similarly a diode 9 in the discharge direction is connected to one terminal of the smoothing capacitor 5. Since both ends of the smoothing capacitor 4 are not directly connected to the rectifier 2, the terminals on both sides are connected to the output terminal of the rectifier 2 via diodes 10 and 12 in the discharge direction, respectively. The polarities of the smoothing capacitors 3, 4, and 5 connected to the output terminal of the rectifier 2 are all connected to have the same polarity. Further, 14 is an inverter circuit connected between the output terminals of the rectifier 2. Next, the operation of this circuit will be explained using the waveform diagram of FIG. 2. In FIG. 2, a is the AC voltage waveform of the commercial AC power supply 1, and b is the smoothing circuit 13.
This is the output voltage waveform of the rectifier 2 when it is not connected, and vp indicates the peak value of this voltage waveform.
Smoothing capacitors 3, 4, 5 are diodes 6,
7. When charged via the charging current limiting current coil 8 and the capacitance of the smoothing capacitors 3, 4, and 5 is sufficiently large, approximately 1/3 of the peak voltage value vp.
voltage value. Then, during a period when the output voltage of the rectifier 2 is lower than the voltage of the smoothing capacitors 3, 4, and 5, power is supplied from each smoothing capacitor 3, 4, and 5 to the inverter circuit 14 via the diodes 9 to 12. . Therefore, the input voltage waveform of the inverter circuit 14 in FIG. 1 becomes as shown in FIG. 2c. By the way, in this conventional DC power supply circuit, when the input voltage of the rectifier 2 is a voltage obtained by controlling the phase of the commercial AC power supply 1, the input power factor can be adjusted by appropriately increasing the inductance of the charging current limiting chiyoke coil 8. This has the advantage that it has a high power factor and that the effective value of the input current of the power supply can be made smaller than the value without phase control.

However, in the phase where the voltage rises in each half cycle of the phase-controlled commercial AC voltage waveform, if the inverter circuit 14 includes inductance and capacitance, the LC resonance will cause the input voltage of the inverter circuit 14 to change. There was a problem with high surge voltage.

Summary of the Invention The present invention reduces the surge voltage generated at the input of the inverter circuit by simply adding a capacitor to the smoothing circuit, while retaining the advantages of the prior art.

Embodiments of the invention Examples of the invention will be described below with reference to the drawings.
FIG. 3 shows a dimming discharge lamp lighting device. In the figure, the inverter circuit 14 operates the discharge lamp 23 at approximately 20KHz.
It is a self-oscillating push-pull type transistor inverter for lighting at a high frequency of ~50KHz, and is configured as follows.

That is, the positive output end of the rectifier 2 is connected to the leakage type output transformer 19 via the harmonic choke coil 18.
The rectifier 2 is connected between a pair of primary windings 19a and 19b, and the negative output terminal of the rectifier 2 is connected to the emitters of a pair of transistors 20a and 20b. The bases of the transistors 20a and 20b are connected to both ends of the base winding 19c of the output transformer 19 and to the positive output terminal of the rectifier 2 via base resistors 21a and 21b, respectively. The collectors of the transistors 21a and 21b are connected to one end of the primary windings 19a and 19b, respectively, and a resonance capacitor 22 is connected between the collectors. In addition, the output transformer 19 has a primary winding 19
a, 19b, and has an output winding 19d as a secondary winding outside the base winding 19c, and the output winding 19
Both ends of d are connected to the discharge lamp 23. Also,
Reference numeral 15 denotes a phase control circuit for controlling the phase of the voltage of the commercial AC power supply 1, which is composed of a triax 16 and a control circuit 17 as is well known. The structure of the smoothing circuit 13 is the same as the conventional circuit except that a surge voltage reducing capacitor 24 whose capacitance is smaller than that of the smoothing capacitors 3, 4, and 5 is added to both ends of the charging current limiting choke coil 8.

Next, the operation of the discharge lamp lighting device configured as described above will be explained. When the smoothed DC voltage without phase control shown in FIG. At the same time, a base current is supplied from the positive output terminal of the rectifier 2 to the transistors 20a and 20b via the base resistors 21a and 21b. At this time, due to a slight imbalance in the circuit, a collector current begins to flow to either one of the transistors 20a and 20b, and the inverter circuit 14 performs self-oscillation operation due to the action of the base winding 19c, and each winding of the output transformer 19 For example, the line
A high frequency voltage of about 20KHz to 50KHz is generated, and the discharge lamp 23 is fully lit. Further, as is well known, the discharge lamp 23 can be dimmed by the phase control circuit 15.

By the way, FIG. 4 shows waveform diagrams of various parts when the discharge lamp 23 is dimmed by the phase control circuit 15. In the figure, a shows the phase-controlled input voltage waveform of the rectifier 2, and b shows the waveform of the input voltage of the inverter circuit 14. input voltage waveform,
In FIG. 3, c is the input voltage waveform of the inverter circuit 14 when the surge voltage reduction capacitor 24 is not provided. As can be seen from these waveform diagrams, when the discharge lamp 23 is dimmed, the inductance of the harmonic chain 18 of the inverter circuit 14 and the output transformer 19 at the voltage rising phase φ ₁ in each half cycle of the input voltage of the rectifier 2 The inverter circuit 1 is
Surge voltages V _s1 and V _s2 are generated at the input voltage of 4.
In this case, the surge voltage V _s1 can be reduced by inserting the surge voltage reduction capacitor 24 in parallel with the charge current limiting choke coil as in the present invention.
It can be kept lower than V _s2 . As the capacitance of the surge voltage reduction capacitor 24 increases, the surge voltage V _s1 can be lowered, but the input current of the discharge lamp lighting device increases in proportion to this.

The size of the capacitance of the surge voltage reduction capacitor 24 is within a range where the effective value of the input current of the discharge lamp lighting device when the discharge lamp 23 is dimmed is not different from the case without the surge voltage reduction capacitor 24. It is preferable to set the maximum value to . By the way, in Fig. 3, the capacitance of smoothing capacitors 3, 4, and 5 is 47μF, the inductance of charging current limiting coil 8 is 7mH, and the discharge lamp 23 is 110W.
In the case of fluorescent lights, surge voltage reduction capacitor 24
The capacitance of is approximately 0.1μF.

Note that the inverter circuit 14 is not limited to the one shown in FIG. 3, and when the discharge lamp is dimmed, the inverter circuit 14
This is effective if the inverter circuit generates the above-mentioned surge voltage at the input voltage. In addition, smoothing circuit 1
The number of smoothing capacitors in No. 3 is not limited to three.

Effects of the invention As described above, the dimming discharge lamp lighting device of the invention uses a simple method of connecting a capacitor in parallel to the charging current control coil of the smoothing circuit that smooths the input voltage of the inverter circuit. Even when the discharge lamp is dimmed by inserting a capacitor, the input current value of the device hardly increases compared to when a capacitor is inserted, and the surge voltage generated in the inverter input voltage can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a conventional device, Fig. 2 is a waveform diagram for explaining the operation of the device shown in Fig. 1, and Fig. 3 is a diagram showing a conventional device.
This figure shows a dimming discharge lamp lighting device of the present invention, and FIG. 4 is a waveform diagram for explaining the operation of the device shown in FIG. 3. In the figure, 1... Commercial AC power supply, 2... Rectifier circuit, 3, 4, 5... Smoothing capacitor, 8...
Charging current limiting chiyoke coil, 13... Smoothing circuit, 14... Inverter circuit, 15... Phase control circuit, 18... Harmonic chiyoke coil, 19...
Output transformer, 23...Discharge lamp, 24...Surge voltage reduction capacitor. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims for Utility Model Registration] (1) A phase control circuit that controls the phase of an AC power supply, a rectifier that rectifies the output voltage of this phase control circuit, a charging current limiting coil between the output terminals of this rectifier, and the rectifier. A plurality of smoothing capacitors for smoothing the output voltage of the rectifier are connected in series, and a charging diode is connected in series between all adjacent smoothing capacitors, and the output terminal of the rectifier is connected directly to the output terminal of the rectifier. A smoothing circuit in which a diode in the discharging direction is connected to the terminal of each of the smoothing capacitors on the side that is not connected to the terminal, and all the smoothing capacitors are connected with the same polarity, and the DC voltage that is the output of the rectifier is converted to a high frequency. In a discharge lamp lighting device for dimming, which includes an inverter circuit that operates, and a discharge lamp that lights by inputting a high-frequency voltage that is the output of the inverter circuit, the charging current limiting coil has a capacitance smaller than that of the smoothing capacitor. A dimming discharge lamp lighting device characterized by connecting capacitors for reducing surge voltage in parallel. (2) There is no difference in the capacitance of the surge voltage reduction capacitor in the input current of the lighting device when the discharge lamp is dimmed by phase control compared to when there is no surge voltage reduction capacitor. The dimming discharge lamp lighting device according to claim 1, wherein the lighting device is set to the maximum value within the range.