JPH10215579A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply in which the output current can be prevented from increasing, even if it is connected to a power supply of different voltage. SOLUTION: A voltage is stepped up by means of a step-up chopper circuit 3 and converted through an inverter circuit 5 into a high-frequency voltage for lighting a fluorescent lamp FL. When an AC commercial power supply (e) has a rated voltage of 200V, a Zener diode ZD1 is turned, a transistor Q11 is turned on, a resistor R11 is bypasses, a normal feedback value being set by voltage division through resistors R4, R5 is employed for control, and the step-up chopper circuit 3 produces a normal output. In the case being 100V lower than the rated voltage, the Zener diode ZD1 sustains an off state, and the resistor R11 is connected. Consequently, a voltage higher than the actual output voltage is inputted to the feedback terminal FB of a control circuit 4, and the current level is lowered thus controlling the lighting of the fluorescent lamp FL.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power supply having a chopper circuit and an inverter circuit.

[0002]

2. Description of the Related Art Conventionally, as a power supply device of this type, for example, a configuration shown in FIG. 3 is known. In the power supply device shown in FIG. 3, a noise filter circuit 1 is connected to a commercial AC power supply e. The noise filter circuit 1 has a capacitor C1, a common mode choke Tr1, and a capacitor C2. Is connected to an input terminal of a full-wave rectifier circuit 2 such as a diode bridge, and an output terminal of the full-wave rectifier circuit 2 is connected to a step-up chopper circuit 3 which is a DC conversion circuit.

The boost chopper circuit 3 includes a primary winding Tr of a transformer Tr2 between output terminals of the full-wave rectifier circuit 2.
2a, a series circuit of a field effect transistor Q1 and a resistor R1 is connected, and a diode D1 and a smoothing capacitor C3 are connected in parallel with the field effect transistor Q1 and the resistor R1.
Are connected in series. Note that a series resonance circuit is configured by the primary winding Tr2a of the transformer Tr2 and the capacitor C3. A resistor is provided between the output terminals of the full-wave rectifier circuit 2.
A series circuit of R2 and R3 is connected, and the connection point of these resistors R2 and R3 is connected to the multiplier M of the control circuit 4.
ULT terminal, and a series circuit of resistors R4 and R5 is connected in parallel with the capacitor C3.
The connection point of the resistor R5 is connected to the feedback FB terminal of the control circuit 4, and the connection point of the field effect transistor Q1 and the resistor R1 is connected to the CS terminal of the current sense amount of the control circuit via the resistor R6. Circuit 4 is further connected to the gate terminal of field effect transistor Q1. An error amplifier is connected to the FB terminal.
The field effect transistor Q1 of the boost chopper circuit 3 is controlled so that the voltage input to the B terminal is always constant.

The boost chopper circuit 3 is connected to a high frequency series resonance type half-bridge type inverter circuit 5 which is a frequency converter. The inverter circuit 5 includes a field-effect transistor Q2 and a field-effect transistor Q3 connected in series.
The control circuit 6 is connected to the gates of Q2 and the field effect transistor Q3. In addition, field effect transistors
A fluorescent lamp as a discharge lamp is connected to both ends of Q3 via a ballast choke L1 and a capacitor C4 for DC cut.
One ends of the filaments FLa and FLb of the FL are connected, and a starting capacitor C5 is connected between the other ends of the filaments FLa and FLb.

[0005] First, the AC voltage of the commercial AC power supply e is full-wave rectified by the full-wave rectifier circuit 2 via the noise filter circuit 1. The control circuit 4 chops the field effect transistor Q1, stores the DC voltage full-wave rectified by the full-wave rectifier circuit 2 in the transformer Tr2 when the field-effect transistor Q1 is on, and stores the energy in the transformer Tr2 when the field-effect transistor Q1 is off. The energy of the transformer Tr2 is released. further,
Capacitor smoothed by diode D1 and capacitor C3
The voltage of C3 is a DC voltage. According to the boost chopper circuit 3, the output voltage of the full-wave rectifier circuit 2 is directly chopped by the field effect transistor Q1 and smoothed by the diode D1 and the capacitor C3. As a result, the power factor is improved and the ripple can be reduced, so that the flicker of the fluorescent lamp FL can be reduced.

Further, the divided voltage of the resistors R4 and R5 is fed back to the control circuit 4 so that the output of the step-up chopper circuit 3 is kept constant by the control circuit 4.

Further, when the output of the fluorescent lamp FL is used while changing the brightness depending on the use condition, the control circuit 6 changes the switching frequency of the field effect transistor Q3 and the field effect transistor Q4 to change the resonance. Dimming the brightness of the fluorescent lamp FL.

[0008]

However, in the conventional example shown in FIG. 3, when the input voltage is 200 V, for example, the output voltage is rated when it is connected to a 100 V commercial AC power supply e. Since the output power of the boost chopper circuit 3 is kept constant by the control circuit 4, the output voltage becomes twice the rated value, which has a problem that the circuit may be adversely affected. .

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a power supply device capable of preventing an increase in output current even when connected to power supplies of different voltages.

[0010]

A power supply device according to the present invention includes a chopper circuit that boosts a power supply voltage and outputs the output power while keeping the output power substantially constant, and an inverter circuit that converts the output of the chopper circuit into an alternating current and outputs a variable output. Power supply voltage detection means for detecting the power supply voltage, and output control means for at least reducing the output of the chopper circuit when the voltage detected by the power supply voltage detection means is equal to or less than a predetermined value, comprising: When the detection means detects that the power supply voltage is equal to or lower than a predetermined value,
Since the output of the chopper circuit is reduced at least by the output control means, the output current is prevented from increasing.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the power supply device of the present invention will be described below with reference to the drawings. The parts corresponding to the conventional example shown in FIG.

As shown in FIG. 1, a noise filter circuit 1 is connected to a commercial AC power supply e. The noise filter circuit 1 has a capacitor C1, a common mode choke Tr1, and a capacitor C2. Is connected to an input terminal of a full-wave rectifier circuit 2 such as a diode bridge, and an output terminal of the full-wave rectifier circuit 2 is connected to a boost chopper circuit 3 which is a DC conversion circuit.

The boost chopper circuit 3 includes a primary winding Tr of a transformer Tr2 between output terminals of the full-wave rectifier circuit 2.
2a, a series circuit of a field effect transistor Q1 and a resistor R1 is connected, and a diode D1 and a smoothing capacitor C3 are connected in parallel with the field effect transistor Q1 and the resistor R1.
Are connected in series. Note that a series resonance circuit is configured by the primary winding Tr2a of the transformer Tr2 and the capacitor C3. A resistor is provided between the output terminals of the full-wave rectifier circuit 2.
A series circuit of R2 and R3 is connected, and the connection point of these resistors R2 and R3 is connected to the multiplier M of the control circuit 4.
Connected to the ULT terminal, a series circuit of a resistor R4, a resistor R5 and a resistor R11 is connected in parallel with the capacitor C3, and a connection point of the resistors R4 and R5 is connected to a feedback FB terminal of the control circuit 4. The connection point between the field effect transistor Q1 and the resistor R1 is connected to the CS terminal of the current sense amount of the control circuit via the resistor R6, and the control circuit 4 is further connected to the gate terminal of the field effect transistor Q1. An error amplifier is connected within the FB terminal, and controls the field effect transistor Q1 of the boost chopper circuit 3 so that the voltage input to the FB terminal is always constant.

The boost chopper circuit 3 is connected to a high frequency series resonance half-bridge type inverter circuit 5 which is a frequency converter. The inverter circuit 5 includes a field-effect transistor Q2 and a field-effect transistor Q3 connected in series.
The control circuit 6 is connected to the gates of Q2 and the field effect transistor Q3. In addition, field effect transistors
A fluorescent lamp as a discharge lamp is connected to both ends of Q3 via a ballast choke L1 and a capacitor C4 for DC cut.
One ends of the filaments FLa and FLb of the FL are connected, and a starting capacitor C5 is connected between the other ends of the filaments FLa and FLb.

Further, a power supply voltage detecting circuit 11 as a power supply voltage detecting means is connected between the output terminals of the full-wave rectifier circuit 2. In the power supply voltage detecting circuit 11, a series circuit of a resistor R15 and a resistor R16 is connected between the output terminals of the full-wave rectifier circuit 2, and a capacitor C1 is connected in parallel with the resistor R16.
1 is connected, and the connection point between the resistors R15 and R16 is connected via a Zener diode ZD1 to the base of a transistor Q11 as output control means. The collector and the emitter of the transistor Q11 are connected between both ends of the resistor R11.

The Zener diode ZD1 is set to turn on when the power supply voltage of the commercial AC power supply e is 200V, and to turn off when the power supply voltage is 100V.
Further, the resistance R1 and the resistance R2 are equal to 4
It is set to output 00V.

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

First, the AC voltage of the commercial AC power supply e is full-wave rectified by the full-wave rectifier circuit 2 via the noise filter circuit 1,
The waveform shown in FIG. 2A is output. The control circuit 4
The DC voltage that is chopped by the field effect transistor Q1 and full-wave rectified by the full-wave rectifier circuit 2 is stored in the transformer Tr2 when the field-effect transistor Q1 is turned on.
When the field effect transistor Q1 is turned off, the energy of the transformer Tr2 is released, and the waveform shown in FIG. 2C is output. Further, after smoothing by the diode D1 and the capacitor C3, the voltage of the capacitor C3 becomes a DC voltage as shown in FIG. According to the boost chopper circuit 3, the output voltage of the full-wave rectifier circuit 2 is directly chopped by the field effect transistor Q1 and smoothed by the diode D1 and the capacitor C3. As a result, the power factor is improved and the ripple can be reduced, so that the flicker of the fluorescent lamp FL can be reduced.

Then, the control circuit 6 turns on the field effect transistors Q2 and Q3 alternately.
By turning off, the high frequency AC voltage shown in FIG. 2E is applied to the fluorescent lamp FL, and the fluorescent lamp FL is turned on at high frequency.

When the commercial AC power supply e has a rated voltage of 200
In the case of V, the zener diode ZD1 of the power supply voltage detection circuit 11 is turned on, and the transistor Q11 is turned on, thereby bypassing the resistor R11, and a normal feedback value set by the voltage division of the resistor R4 and the resistor R5. The control circuit 4 performs control, and the boost chopper circuit 3 has a normal output.

On the other hand, when the commercial AC power supply e is 100 V lower than the rated voltage, the Zener diode ZD1 of the power supply voltage detection circuit 11 keeps the off state, and the transistor Q11
Is turned off, the control circuit 4 controls with a feedback value set by the voltage division of the resistors R4, R5 and R11, and the boost chopper circuit 3 has an output lower than the normal output. That is, by connecting the resistor R11, a voltage higher than the actual output voltage is input to the feedback terminal FB of the control circuit 4, so that the current value is reduced and the output current value of the chopper circuit 3 becomes abnormally high. And the fluorescent lamp FL is lit in a dimmed state.

When the power supply voltage of the commercial AC power supply e is low and the transistor Q11 is not turned on, the control circuit 4 stops the chopping of the transistor Q1 and outputs a value smoothed to the peak voltage of the input voltage. You may. Further, the fluorescent lamp FL may be turned off.

When the fluorescent lamp FL is dimmed or turned off, it is understood that the fluorescent lamp FL is connected to the commercial AC power supply e having the wrong voltage.

[0024]

According to the power supply device of the present invention, the power supply voltage is detected by the power supply voltage detection means, and if the power supply voltage is equal to or less than a predetermined value, the output control means reduces at least the output of the chopper circuit. An increase in current can be prevented.

[Brief description of the drawings]

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

FIG. 2 is a waveform chart showing the same operation.

FIG. 3 is a circuit diagram showing a conventional power supply device.

[Explanation of symbols]

 3 Boost chopper circuit 5 Inverter circuit 11 Power supply voltage detection circuit as power supply voltage detection means Q11 Transistor as output control means

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI H05B 41/29 H05B 41/29 C

Claims (1)

[Claims] 1. A chopper circuit that boosts a power supply voltage and outputs the output power while keeping the output power substantially constant, an inverter circuit that converts an output of the chopper circuit into an alternating current and outputs variable, and a power supply voltage detection unit that detects the power supply voltage And a power control unit for reducing at least the output of the chopper circuit when the voltage detected by the power supply voltage detection unit is equal to or less than a predetermined value.