JPH05219723A - 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:When a discharge lamp FL is dimmed, a switch SW1 is closed and a dimmer signal is outputted to an inverter control circuit 6 by a dimmer circuit 5. The ON-OFF period of the switching elements Q2, Q3 of an inverter circuit 4 is changed and the frequency of the inverter circuit 4 is raised so that the output of the inverter circuit 4 is lowered, and the discharge lamp FL is dimmed. The current of the discharge lamp FL lowers and the voltage across a resistance R1 also lowers so that power detected by a power-detecting means 7 lowers. An operational amplifier OP1 produces a non-inverted output and the non-inverted input to an operational amplifier OP2 increases so that the operational amplifier OP2 produces an inverted output, and the switching element Q1 of a booster chopper circuit 3 is controlled by a chopper control circuit 8 in the direction of lowering the output of the booster chopper circuit 3.

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 an object of the present invention is to provide a power supply device in which heat generation of elements, deterioration of switching elements, and the like 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 reducing the output of the step-up chopper means when the load power detected by the power detection means decreases.

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 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 load of the load is detected by the power detecting means. When the electric power is detected and the load electric power detected by the electric power detection means decreases, the output of the step-up chopper means is decreased by the control means, so that heat generation of the element of the step-up chopper means and deterioration of the element of the inverter means can be prevented.

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 element of the step-up chopper means and deterioration of the element of the inverter means.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to a discharge lamp lighting device shown in 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 via a resistor R1 for power detection. In this 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 via a resistor R1.

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 FL1, FL2 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 FL1, FL2.

Further, a dimming circuit 5 is connected from a commercial AC power source E through a dimming switch SW1, and an inverter control circuit 6 is connected to the dimming circuit 5, and the inverter control circuit 6 drives the inverter. The switching elements Q2 and Q3 of the circuit 4 are controlled to control the output of the inverter control circuit 6.

Further, a power detection circuit 7 as power detection means is connected to both ends of the resistor R1. This power detection circuit 7 is composed of a resistor R2, a resistor R3 and an operational amplifier OP1, and a diode D2 is connected to the output terminal of the operational amplifier OP1 of this power detection circuit 7. Further, a series circuit of a resistor R4, a resistor R5 and a resistor R6 is connected between the cathode of the diode D1 and the ground, and a resistor R5 and a resistor R6 are connected.
The cathode of the diode D2 is connected to the connection point of.
Further, the connection point of the resistors R4 and R5 is connected to the non-inverting input terminal of the operational amplifier OP2 via the resistor R7, and the reference voltage source E1 is connected to the non-inverting input terminal. In addition, a resistor R8 is placed between the inverting input terminal and the output terminal of the operational amplifier OP2.
Is connected, and the output terminal of the operational amplifier OP2 is connected to a chopper control circuit 8 as a control means. The chopper control circuit 8 controls 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 boost chopper circuit 3 is switched by the chopper control circuit 8 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.

Further, when dimming the discharge lamp FL, the switch SW1 is closed and the dimming circuit 5 outputs a dimming signal to the inverter control circuit 6 so that the switching elements Q2 and Q3 of the inverter circuit 4 are turned on. Change the on / off cycle,
Increasing the frequency of the inverter circuit 4
To reduce the output of the discharge lamp FL and turn on the dimming lamp. Then, in this case, the current of the discharge lamp FL decreases and the resistance R1
The voltage detected by the power detection circuit 7 decreases, and the operational amplifier OP1 inverts and outputs the
The non-inverting input of OP2 increases and the operational amplifier OP2 outputs an inverting output, and the chopper control circuit 8 controls the switching element Q1 of the step-up chopper circuit 3 to decrease the output of the step-up chopper circuit 3. By this control, the output of the boost chopper circuit 3 is reduced.

Therefore, the stress of the switching elements Q2, Q3 of the inverter circuit 4 at the time of low output is reduced as compared with the conventional case, and the deterioration of the switching elements Q2, Q3 can be prevented. Also, since the output of the boost chopper circuit 3 also decreases,
The current flowing through inductor L1 also decreases, and inductor L1
It is also possible to prevent heat generation.

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.

[0023]

According to the power supply device of the present invention, the output of the DC power supply is boosted by the boosting chopper means, the output of the boosting chopper means is inversely converted by the inverter means and supplied to the load, and the power detecting means is provided. The load power of the load is detected by, and when the load power detected by the power detection means decreases, the output of the boost chopper means is reduced by the control means. It can be prevented.

According to the discharge lamp lighting device of the second aspect, the power supply device of the first aspect is provided and the discharge lamp is turned on.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a power supply device of the present invention.

[Explanation of symbols]

 2 DC power supply 3 Boost chopper circuit as boost chopper means 4 Inverter circuit as inverter means 7 Power detection circuit as power detection means 8 Chopper control circuit as control means FL Discharge lamp as load

Claims (2)

[Claims] 1. A step-up chopper means for boosting 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 power detection means for detecting the load power of the load, and this power. A power supply device comprising: a control unit that reduces the output of the boost chopper unit when the load power detected by the detection unit decreases. 2. A discharge lamp lighting device, comprising the power supply device according to claim 1, and lighting a discharge lamp.