JPH05219724A - Power supply and discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To provide a discharge lamp lighting device, in which the heat generation of element, deterioration of switching element, etc., are difficult to occur. CONSTITUTION:After a discharge lamp FL is lighted, the voltage of the discharge lamp FL lowers so that the potential of the connection of resistors R8 and R9 lowers and an operational amplifier OP2 produces a non-inverted output. A chopper control circuit 9 controls the switching element Q1 of a booster chopper circuit 3, lowers the output of the booster chopper circuit 3 and lowers the output of an inverter circuit 4. After the discharge lamp FL is lighted, a lighting detector circuit 7 produces on output, turns ON a transistor Q4 and bypasses a current flowing through a voltage detector circuit 8. Even if the output of the voltage detector circuit 8 is lowered and the voltage of the discharge lamp FL rises, the current of the resistor R10 is not bypassed and the booster chopper circuit 3 is prevented from increasing output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device and a discharge lamp lighting device which reversely convert electric power boosted by boosting chopper means by an inverter means to supply it to a load.

[0002]

2. Description of the Related Art In recent years, as a countermeasure against harmonics generated from an inverter circuit, a
A configuration is adopted in which a step-up chopper circuit is connected and the harmonics generated from the inverter circuit are not returned to the DC power supply circuit.

A step-up chopper circuit and an inverter circuit are connected in series from a DC power source, and the output of the inverter circuit supplies high-frequency power to a load such as a discharge lamp.

When adjusting the power supplied to the load, the output of the inverter circuit is changed.

[0005]

However, when controlling the output of the inverter circuit, since the output of the boost chopper circuit is not controlled, stress is applied to the inductor of the boost chopper circuit and heat is generated in the inductor. However, there is a problem that the switching element of the inverter circuit is overloaded and the switching element deteriorates.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a power supply device and a discharge lamp lighting device in which heat generation of elements and deterioration of switching elements are less likely to occur.

[0007]

According to a first aspect of the present invention, there is provided a power supply device, a step-up chopper means for stepping up an output of a DC power source, an inverter means for inversely converting the output of the step-up chopper means and supplying the load, and the load. And a control means for controlling the output of the step-up chopper means according to the voltage of the load detected by the voltage detection means.

According to a second aspect of the present invention, there is provided a discharge lamp lighting device including the power supply device according to the first aspect, for lighting a discharge lamp.

[0009]

In the power supply device according to the present invention, the output of the DC power source is boosted by the boost chopper means, the output of the boost chopper means is inversely converted by the inverter means and supplied to the load, and the voltage of the load is detected by the voltage detecting means. The output of the step-up chopper means is controlled by the control means in accordance with the fluctuation of the voltage detected by the voltage detection means.
It is possible to prevent deterioration of the elements of the inverter means.

Since the discharge lamp lighting device according to the second aspect comprises the power supply device according to the first aspect, it is possible to prevent heat generation of the elements of the step-up chopper means and deterioration of the elements of the inverter means, and to start the discharge lamp. Sometimes the starting voltage is easily obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A discharge lamp lighting device according to an embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, E is a commercial AC power supply, and the input terminal of the rectifier circuit 1 is connected to the commercial AC power supply E.
The commercial AC power supply E and the rectifier circuit 1 constitute a DC power supply 2. A boost chopper circuit 3 as boost chopper means is connected to the output terminal of the DC power supply 2.

In the boost chopper circuit 3, an inductor L1 and a diode D1 are connected to the positive side of the rectifier circuit 1,
Rectifier circuit 1 and connection point of inductor L1 and diode D1
The switching element Q1 is connected between the cathode of the diode D1 and the cathode of the rectifier circuit 1, and the capacitor C1 is connected between the cathode of the diode D1 and the anode of the rectifier circuit 1.

Further, the booster chopper circuit 3 is connected to an inverter circuit 4 as a half-bridge type inverter means. In the inverter circuit 4, a switching element Q2 and a switching element Q3 are connected in series between the output terminals of the boost chopper circuit 3.

Further, the inverter circuit 4 is connected to a series circuit of a voltage dividing capacitor C2 and a capacitor C3, and between the connection point of the switching elements Q1 and Q2 and the connection point of the capacitors C2 and C3. , The filaments FLa, FLb of the discharge lamp FL as a load are connected via the choke coil L2, and the starting capacitor C4 is connected between these filaments FLa, FL2.

A lamp voltage detection circuit 5 is connected to the discharge lamp FL, and an inverter control circuit 6 for controlling the switching elements Q1 and Q2 of the inverter circuit 4 and a lighting detection circuit 7 are connected to the lamp voltage detection circuit 5. Has been done.

A series circuit of resistors R1 and R2 is connected between the output terminal of the lighting detection circuit 7 and ground, and the base of the transistor Q4 is connected to the connection point of the resistors R1 and R2. The collector of the transistor Q4 is connected between the output terminals of the lighting detection circuit 7, and the emitter is grounded.

Further, the output terminal of the lighting detection circuit 7 is connected to a voltage detection circuit 8 as a voltage detection means.
This voltage detection circuit 8 is used for the filament FL of the discharge lamp FL.
A series circuit of a resistor R3 and a resistor R4 is connected between a and ground, and a diode D2, a resistor R5, and a capacitor C5 are connected to a connection point of the resistor R3 and the resistor R4.

The voltage detection circuit 8 is connected to the inverting input terminal of the operational amplifier OP1 via the resistor R6, and the reference voltage source E1 is connected to the non-inverting input terminal of the operational amplifier OP1.
A resistor R7 is connected between the inverting input terminal and the output terminal. In addition, a series circuit of resistor R8, resistor R9 and resistor R10 is connected between the cathode of diode D1 and ground, and diode D3 is connected between resistor R9 and resistor R10 and the output terminal of operational amplifier OP1. There is. Also, the resistor R8
And the connection point of the resistor R9 is connected to the operational amplifier via the resistor R11.
It is connected to the inverting input terminal of OP2, and resistor R12 is connected between the inverting input terminal and the output terminal of this operational amplifier OP2. Further, the output terminal of the operational amplifier OP2 is connected to a chopper control circuit 9 as a control means, and this chopper control circuit 9 is connected to the switching element Q1 of the boost chopper circuit 3.

Next, the operation of the above embodiment will be described.

First, the power of the commercial AC power source E is rectified by the rectifier circuit 1.
The switching device Q1 of the step-up chopper circuit 3 is switched by the chopper control circuit 9 to boost the voltage. In the inverter circuit 4, the inverter control circuit 6 performs switching control of the switching elements Q2 and Q3 to inversely convert the power boosted by the boost chopper circuit 3. Then, the discharge lamp FL is turned on by the inversely converted high frequency. When the discharge lamp FL is started, the lighting of the discharge lamp FL is detected by the decrease in the lamp voltage detected by the lamp voltage detection circuit 5. At the time of starting the discharge lamp FL, as shown in FIG. 2, the output of the inverter circuit 4 is suppressed to a low level by soft start, and the output after the soft start is increased until the discharge lamp FL lights up. Let When the discharge lamp FL is turned on, the voltage of the discharge lamp FL decreases.

That is, until the discharge lamp FL is lit, as shown in FIG. 2, the lighting detection circuit 7 does not output, the transistor Q4 is turned off, and the voltage detection circuit 8 is operated. Since the voltage of the discharge lamp FL is high, the voltage of the output of the voltage detection circuit 8 rises,
The operational amplifier OP1 outputs an inverted output, bypasses the current of the resistor R10, causes the operational amplifier OP2 to output an inverted output, and outputs the inverted output to the chopper control circuit 9.
The switching element Q1 is controlled to increase the output of the boost chopper circuit 3 and also increase the output of the inverter circuit 4 to facilitate lighting of the discharge lamp FL. Further, even if the voltage of the discharge lamp FL is lowered before the discharge lamp FL is turned on and the operational amplifier OP1 outputs the inverted output, the diode D3 performs an inverse element to prevent the output of the boost chopper circuit 3 from being lowered. ..

On the other hand, in a steady state after the discharge lamp FL is lit, the voltage of the discharge lamp FL decreases, and the resistance R8
And the potential of the connection point of the resistor R9 drops, and the operational amplifier OP2
Outputs a non-inverted output to the chopper control circuit 9, controls the switching element Q1 of the boost chopper circuit 3, lowers the output of the boost chopper circuit 3, and also lowers the output of the inverter circuit 4.

After the discharge lamp FL is lit, the lighting detection circuit 7 outputs and turns on the transistor Q4.
Bypassing the current flowing through the voltage detection circuit 8, reducing the output of the voltage detection circuit 8 and increasing the voltage of the discharge lamp FL, the current of the resistor R10 is not bypassed and the output of the boost chopper circuit 3 increases. Prevent.

According to the above embodiment, since the output of the boost chopper circuit 3 is reduced when the voltage of the discharge lamp FL is reduced,
The stress of the switching elements Q2, Q3 of the inverter circuit 4 is reduced, and deterioration of the switching elements Q2, Q3 can be prevented. Further, since the output of the boost chopper circuit 3 also decreases, the current flowing through the inductor L1 also decreases, and the heat generation of the inductor L1 can be prevented.

The inverter circuit is not limited to the half-bridge type, and the same effect can be obtained with a single-stone type or any other type.

The lighting detection circuit 7 is not limited to the one operated by the voltage of the discharge lamp FL, but may be a simple timer circuit.

[0028]

According to the power supply device of the first aspect, the output of the DC power supply is boosted by the boost chopper means, the output of the boost chopper means is inversely converted by the inverter means and supplied to the load, and the voltage detecting means is used. Since the output of the boost chopper means is controlled by the control means that detects the voltage of the load and the voltage detected by the voltage detection means fluctuates, heat generation of the elements of the boost chopper means and deterioration of the elements of the inverter means can be prevented. ..

According to the discharge lamp lighting device of the second aspect, it is possible to prevent heat generation of the element of the boost chopper means and deterioration of the element of the inverter means. Further, the starting voltage can be easily obtained when starting the discharge lamp.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a discharge lamp lighting device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing the same operation. (A) DC power supply output voltage waveform diagram (b) Discharge lamp voltage waveform diagram (c) Lighting detection circuit output voltage waveform diagram (d) Capacitor C1 voltage waveform diagram

[Explanation of symbols]

 2 DC power supply 3 Boosting chopper circuit as boosting chopper means 4 Inverter circuit as inverter means 8 Voltage detecting circuit as voltage detecting means 9 Chopper control circuit as controlling means FL discharge lamp

Claims (2)

[Claims] 1. A step-up chopper means for stepping up the output of a DC power source, an inverter means for inversely converting the output of the step-up chopper means and supplying it to a load, a voltage detection means for detecting the voltage of the load, and this voltage detection. Control means for controlling the output of the boost chopper means according to the voltage of the load detected by the means. 2. A discharge lamp lighting device, comprising the power supply device according to claim 1, and lighting a discharge lamp.