JPH06267679A - High frequency discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To enhance reliability by coping with counter measures against rush current at the time of restoration from momentary disconnection on the part of a commercial AC power supply. CONSTITUTION:The device is equipped with a rectification means 2 rectifying AC voltage, and with booster chopper circuits 3 through 7 boosting the output of the rectification means 2. The device is also equipped with an inverter lighting circuit 20 which lights a discharge lamp 19 with high frequencies applied using the output of the booster chopper circuits 3 through 7 as a DC power supply, a booster chopper control circuit 6 controlling the switching element 5 of the booster chopper circuits 3 through 7, and also equipped with an inverter control circuit 13 controlling the switching elements 14 and 15 of the inverter lighting circuit 20. In the high frequency discharge lamp lighting device as mentioned above, a means 23 and the like are provided, which detect that the output voltage of the booster chopper circuits 3 through 7 becomes lower than the peak value of AC input voltage 1, and a means 24 is also provided, which suspends the oscillation of the inverter lighting circuit 20 based on the aforesaid detected output.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency discharge lamp lighting device provided with a step-up chopper circuit and an inverter lighting circuit which operates by a DC output thereof.

2. Description of the Related Art A conventional high-frequency discharge lamp lighting device shown in FIG. 2 will be described. The commercial AC power supply 1 of FIG. 2 is connected to the AC input terminal of the full-wave rectifier 2, the (+) side terminal of the full-wave rectifier 2 is connected to the anode of the diode 4 via the choke 3, and the cathode of the diode 4 is a capacitor. It is connected to the (−) side terminal of the full-wave rectifier 2 via 7. Further, the collector of the transistor 5 is connected to the anode side of the diode 4, the emitter is connected to the (−) terminal of the full-wave rectifier 2, and the control circuit 6 is connected to the base to form a boost chopper circuit. Further, a secondary winding is provided on the choke 3 as a power source for the control circuit, rectified by the diode 9, smoothed by the capacitor 11, and the power source is supplied to the control circuit 6. Further, the cathode of the diode 4 is connected to the cathode of the diode 9 through the resistor 8 to form an auxiliary power supply at the time of starting. An inverter lighting circuit 20 is connected to both ends of the capacitor 7 which is the output of the boost chopper circuit, and the switching transistor 14 of the inverter lighting circuit 20 is
The control circuit 13 for controlling 15 is supplied with a power source which rectifies the output of the secondary winding provided in the choke 3 with the diode 10 and smoothes it with the capacitor 12. In such a device, when the commercial AC power supply 1 is turned on, an inrush current for charging the capacitor 7 flows and the choke 3 is saturated. For this reason, if the transistor 5 is turned on while the rush current to the capacitor 7 is flowing, an excessive current flows to the transistor 5 and destroys the transistor 5. Therefore, the control circuit 6 is provided with a soft start function and the capacitor 7 It is known to control the transistor 5 to be turned on and off after the rush current period has passed.

In the high frequency discharge lamp lighting device, the capacity of the capacitor 7 in the output stage of the boost chopper circuit cannot be increased more than necessary due to the demand for downsizing the device. Further, the discharge lamp 17, which is the final load, continues to take the load as the filament preheating current even after the output voltage of the inverter lighting circuit 20 drops and the lamp goes out. Therefore, when the commercial AC power supply 1 is momentarily cut off, the voltage of the capacitor 7 at the output stage of the boost chopper circuit drops below the peak value of the commercial AC power supply 1. In such a momentary interruption of the commercial AC power supply 1, the control circuit 6 of the step-up chopper circuit continues the ON / OFF control of the transistor 5 by the charge of the capacitor 11 which is the driving power supply and the auxiliary power supply via the resistor 8. Therefore, when the commercial AC power supply 1 recovers from the momentary interruption, an inrush current flows to the capacitor 7, and the transistor 5 cannot be protected from the inrush current by the soft start function of the above-described conventional technology. An object of the present invention is to provide a high-frequency discharge lamp lighting device that solves the above-mentioned problems and improves reliability.

In order to achieve the above object, when the commercial AC power supply is momentarily cut off, the output voltage of the boost chopper circuit is detected, and the output voltage of the boost chopper circuit is lower than the peak value of the commercial AC power supply. The oscillation of the inverter part was stopped when it became low.

[Operation] When the commercial AC power supply is momentarily disconnected and the output voltage of the boost chopper circuit falls below the peak value of the commercial AC power supply,
By the detection circuit that detects the output of the boost chopper circuit,
Stop the oscillation of the inverter section. Therefore, the voltage of the capacitor at the output stage of the boost chopper is maintained at the peak value of the commercial AC power supply, and no rush current flows into the capacitor when the momentary interruption is restored. Therefore, an excessive current does not flow in the transistor that is the switching element of the boost chopper.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, the same reference numerals as those in FIG. 2 of the related art indicate the same elements. In this embodiment, the basic circuit configuration of the full-wave rectifier circuit 2, the boost chopper circuit, the inverter lighting circuit 20, etc. is the same as that of FIG. 2, so other points will be mainly described. In the present embodiment, resistors 25 and 26 are connected in series to both ends of the capacitor 7 as a detection circuit of the output voltage of the boost chopper circuit, and the voltage dividing points of the resistors 25 and 26 are connected to the (−) terminal of the comparator 23. To do. Capacitor 11 that is the power supply for the control circuit of the boost chopper circuit
A resistor 21 and a Zener diode 22 are connected in series at both ends of the, and the cathode of the Zener diode 22 is connected to the (+) terminal of the comparator 23 as a reference voltage. The power source of the inverter unit 20 is (+) of the capacitor 12.
The side is the emitter of the transistor 24 which is a switching element,
The output terminal of the comparator is connected to the base of the transistor 24. In the above circuit configuration, the voltage division ratio of the resistors 25 and 26 is set to be equal to the reference voltage of the Zener diode 22 when the output voltage of the boost chopper circuit drops to the peak value of the commercial AC power supply 1. When the commercial AC power supply 1 is turned on and the output of the boost chopper circuit becomes higher than the peak value of the commercial AC power supply 1, the input of the (−) terminal of the comparator 23 becomes higher than the (+) terminal to which the reference voltage is input, The output of the comparator 23 becomes low level and the transistor 24
Is turned on, power is supplied to the control circuit 13 of the inverter unit 20, the transistors 14 and 15 are alternately turned on and off, and the inverter unit oscillates. Here, commercial AC power supply 1
Momentary interruption, the output of the boost chopper circuit decreases, and when it becomes lower than the peak value of the commercial AC power supply 1, the comparator 2
The input of the (-) terminal of 3 becomes lower than the (+) terminal to which the reference voltage is input, and the output of the comparator 23 is H.
i. Therefore, the transistor 24 is turned off, the power source of the control circuit 13 of the inverter lighting circuit 20 is cut off,
Oscillation of the inverter section stops. When the oscillation of the inverter unit 20 is stopped, the load of the boost chopper circuit is the resistance 8
Since there is only a small amount of discharge current through the auxiliary power supply of the control circuit of the step-up chopper circuit and the resistances 25 and 26 of the detection circuit, the voltage of the capacitor 7 is almost kept at the peak value of the commercial AC power supply 1. Be drunk Therefore, when the commercial AC power supply 1 recovers from the momentary interruption, no inrush current flows into the capacitor 7 and the choke 3 does not saturate, so that an excessive current does not flow into the transistor 5 of the step-up chopper circuit, and it is destroyed. There is no. In this embodiment, in order to stop the oscillation of the inverter lighting circuit 20, the power supply of the control circuit is cut off.
Other means for stopping the oscillation of 0 may be used.

According to the present invention, since the output of the step-up chopper circuit is maintained at the peak value of the commercial AC power source when the commercial AC power source is momentarily cut off, the inrush current flows into the step-up chopper circuit after the commercial AC power source is instantaneously restored. Does not flow. Therefore, excessive current does not flow in the switching element of the boost chopper circuit,
The switching element is not destroyed, and the reliability of the device can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a device of the present invention.

FIG. 2 is a circuit diagram of a conventional device.

[Explanation of symbols]

1: Commercial AC power supply, 2: Full wave rectifier, 3: Choke, 4
・ 9/10: diode, 5/24: transistor,
6: boost chopper control circuit, 7/11/12: capacitor, 8 / 21.25 / 26: resistor, 13: inverter control circuit, 20: inverter lighting circuit, 23: comparator

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[Procedure amendment]

[Submission date] May 14, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

Claims (1)

[Claims] 1. A rectifier for rectifying an AC voltage, a boost chopper circuit for boosting the output of the rectifier, an inverter lighting circuit for lighting a discharge lamp at a high frequency using the output of the boost chopper circuit as a DC power source, and the booster. Step-up chopper control circuit that controls the switching element of the chopper circuit, an inverter control circuit that controls the switch element of the inverter lighting circuit, and detect that the output voltage of the step-up chopper circuit becomes lower than the peak value of the AC input voltage. A high-frequency discharge lamp lighting device, comprising: a detection unit that operates to stop the oscillation of the inverter lighting circuit by the detection output of the detection circuit.