JPH10144490A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device having a step-up chopper circuit and an inverter circuit and reducing a burden of the inverter circuit. SOLUTION: In the case of full lighting a fluorescent lamp PL, divided voltage of resistors R4, R11, R5 is input to a control circuit 4. Because of ordinary voltage of the fluorescent lamp FL, voltage of a resistor R14 is also relatively low, a Zener diode ZD1 is not turned on and light is not emitted in a light emitting diode LED1. A phototransistor Q11 is maintained in an off-condition, and voltage input to a terminal FB of the control circuit 4 is left as ordinary. In the case of reducing an output of an inverter circuit 5, voltage of the fluorescent lamp FL rises, voltage divided by the resistor R14 is increased, the Zener diode ZD1 is turned on, the light emitting diode LED1 emits light, the phototransistor Q11 is placed in an on-condition, the resistor R11 is short-circuited, apparent high divided voltage of the resistor R4, R5 is input to the terminal FB of the control circuit 4 and an output of a step-up chopper circuit 3 is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a discharge lamp lighting device having a chopper circuit and an inverter circuit.

[0002]

2. Description of the Related Art Conventionally, as a discharge lamp lighting device of this type, for example, a configuration shown in FIG. 3 is known. This figure 3
In the discharge lamp lighting device shown in FIG. 1, a noise filter circuit 1 is connected to a commercial AC power supply e, and the noise filter circuit 1 has a capacitor C1, a common mode choke Tr1, and a capacitor C2. An input terminal of the full-wave rectifier circuit 2 such as a diode bridge is connected to the output terminal of the full-wave rectifier circuit 2, and a boost chopper circuit 3 as a DC converter is connected to the input terminal.

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 as shown in FIG. According to the boost chopper circuit 3, the full-wave rectifier circuit 2
Output voltage is directly chopped by the field-effect transistor Q1 and smoothed by the diode D1 and the capacitor C3, so that the impedance seen from the commercial AC power supply e side is increased, the power factor is improved, and the ripple can be reduced. The flicker of the 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]

According to the prior art shown in FIG. 3, when the output of the inverter circuit 5 is reduced and the fluorescent lamp FL is used for dimming, the inverter circuit viewed from the boost chopper circuit 3 side is used. The impedance on the 5 side is reduced, the output voltage of the boost chopper circuit 3 increases, the output of the inverter circuit 5 must be further reduced, and the control range of the inverter circuit 5 needs to be widened.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a discharge lamp lighting device having a boost chopper circuit and an inverter circuit and reducing the load on the inverter circuit.

[0010]

According to the present invention, there is provided a discharge lamp lighting device comprising: a chopper circuit for increasing a voltage by varying an output voltage; an inverter circuit for converting an output of the chopper circuit into an alternating current and lighting the discharge lamp with a variable output; A voltage detection circuit that detects the voltage of the discharge lamp and varies the output of the chopper circuit according to the detected voltage. Since the output of the chopper circuit is varied according to the detected voltage and detected by the detection circuit, the dimming of the discharge lamp is performed without increasing the control range of the inverter circuit.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the discharge lamp lighting device according to the present invention will be described 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 resistors R4, R11 and R5 is connected in parallel with the capacitor C3. The connection point of these resistors R4, R11 and R5 is connected to the 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.

Furthermore, the filament FLa of the fluorescent lamp FL
, FLb, a voltage detection circuit 11 is connected between the resistors R12, R13 and R14.
Are connected in parallel with the resistor R14, the Zener diode ZD1, the light-emitting diode LED1 and the resistor R15.
And a phototransistor Q11 photo-coupled to the light-emitting diode LED1 in parallel with the resistor R11.

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. Further, the control circuit 4 chops the field effect transistor Q1 and the full-wave rectified DC voltage is supplied to the transformer Tr2 when the field effect transistor Q1 is turned on.
And discharges the energy of the transformer Tr2 when the field effect transistor Q1 is turned off. 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,
Because it is smoothed by diode D1 and capacitor C3,
The impedance as viewed from the commercial AC power supply e side increases,
Since the power factor can be improved and the ripple can be reduced, the flicker of the fluorescent lamp FL can be reduced.

When the inverter circuit 5 has an output corresponding to normal all-light lighting, the divided voltage of the resistors R4, R11 and R5 is fed back to the control circuit 4, and the booster chopper circuit is controlled by the control circuit 4. The output of 3 is kept constant. That is, when the output voltage of the inverter circuit 5 is high, since the impedance of the inverter circuit 5 as viewed from the boost chopper circuit 3 is high, the voltage of the fluorescent lamp FL can be suppressed, and the voltage divided by the resistor R14 is also compared. The zener diode ZD1 does not turn on and the light emitting diode LED1 does not emit light, so that the phototransistor Q11 maintains the off state. Therefore, the voltage VFB input to the FB terminal of the control circuit 4 is obtained by setting the resistance value of the resistor R4 to R4,
The resistance of R5 R5, the resistance value R11 of the resistor R11, the voltage value of the capacitor C3 and VC3, the _{VFB h = {(R4 + R11} + R5) / R5} × VC3 h.

On the other hand, when the control circuit 6 changes the switching frequency of the transistor Q3 and the transistor Q4 to change the resonance and narrow the output of the inverter circuit 5 to dimm the fluorescent lamp FL, the inverter circuit 5
, The voltage of the fluorescent lamp FL increases, the voltage divided by the resistor R14 increases, and the Zener diode ZD1 turns on. Light emitting diode
LED1 emits light, and phototransistor Q11 is turned on. Therefore, the voltage VFB is input to the FB terminal of the control circuit _{4, VFB l = {(R4 +} R5) / R5} × VC3 l becomes, the voltage value of the capacitor C3 is input to apparently increase, even if the same, The step-up chopper circuit 3 is controlled so as to suppress the output as compared with the case of all-light dimming.

[0020] That is, {(R4 + R11 + R5 ) / R5} × VC3 h = {(R4 +
R5) / R5} for the × VC3 _l, as compared to when the output of the inverter circuit 5 is high output, when the output of the inverter circuit 5 is low, the output of the boost chopper circuit 3 is reduced.

Therefore, when the output of the inverter circuit 5 is reduced, the output of the boost chopper circuit 3 is also reduced. Therefore, even if the control range of the inverter circuit 5 is not large, the input voltage is reduced, so that the fluorescent lamp FL is reduced. The input output can be reduced, and the fluorescent lamp FL can be easily dimmed.

[0022]

According to the discharge lamp lighting apparatus of the present invention, the voltage detection circuit detects that the output of the inverter circuit is reduced and the voltage of the discharge lamp changes, and the output of the chopper circuit is determined in accordance with the detected voltage. , The discharge lamp can be dimmed without increasing the control range of the inverter circuit.

[Brief description of the drawings]

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

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

FIG. 3 is a circuit diagram showing a conventional discharge lamp lighting device.

[Explanation of symbols]

 3 Chopper circuit 5 Inverter circuit 11 Voltage detection circuit FL Fluorescent lamp as discharge lamp

Claims (1)

[Claims] 1. A chopper circuit that boosts the output voltage with a variable output voltage, an inverter circuit that converts the output of the chopper circuit into an alternating current and turns on a discharge lamp with a variable output voltage, and detects the voltage of the discharge lamp and detects the detected voltage. And a voltage detecting circuit for varying the output of the chopper circuit according to the following.