JPH10214694A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device having a voltage rising chopper circuit and an inverter circuit to reduce the load of the inverter circuit. SOLUTION: When a fluorescent lamp FL is fully lighted, a large lamp current is conducted to increase a voltage drop of a resistor R12, and a transistor Q11 is turned on to maintain a constant output of a voltage rising chopper circuit 3. When the fluorescent lamp FL is partially lighted, a small lamp current is conducted to decrease the voltage drop of the resistor R12. Hence, an apparent resistance value between an emitter and a collector of the transistor Q11 is increased to produce an apparently high input even when a voltage value of a capacitor C3 is not changed. For this reason, the voltage rising chopper circuit 3 is controlled to suppress its output as compared with the case of full lighting. In the case of a high output of an inverter circuit 5 as compared with the case of a low output of the inverter circuit 5, an output of the voltage rising chopper circuit 3 is lowered.

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. 4 is known. This figure 4
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. 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]

According to the conventional example shown in FIG. 4, 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 a first aspect of the present invention, there is provided a discharge lamp lighting device, comprising: a chopper circuit for boosting the output voltage by varying the output voltage; An inverter circuit, and a current detection circuit that detects the current of the discharge lamp and varies the output of the chopper circuit according to the detected current. When the current is detected, the current detection circuit detects the change in the lamp current, and the output of the chopper circuit is varied according to the detected current. By using a lamp current with a small change, the discharge lamp is appropriately dimmed.

According to a second aspect of the present invention, there is provided the discharge lamp lighting device according to the first aspect, wherein the inverter circuit comprises:
It is capable of continuous dimming, and the output of the chopper circuit changes in response to continuous dimming.

According to a third aspect of the present invention, there is provided the discharge lamp lighting device according to the first aspect, wherein the inverter circuit comprises:
Stepwise dimming is possible, and the output of the chopper circuit changes according to the stepwise dimming.

[0013]

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. Parts corresponding to those of 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.
The ULT terminal is connected in parallel with the capacitor C3, and a series circuit of a resistor R4, a resistor R5 and a resistor R11 is connected. A connection point of the resistors R4, R5 and R11 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 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.

Further, the filament FLb of the fluorescent lamp FL
A current detecting circuit 11 for detecting a lamp current is provided between one end of the full-wave rectifier circuit 2 and one end of the filament FLb of the fluorescent lamp FL. A resistor R12 is connected between the negative electrode and the base of a transistor Q11 via a resistor R13 to a connection point between one end of the filament FLb and the resistor R12.The transistor Q11 is connected to both ends of the resistor R11 via a resistor R14. It is connected.

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, since a large lamp current flows through the fluorescent lamp FL, the voltage drop of the resistor R12 becomes large and the transistor Q11 is turned on. And the resistor R14
Connected in parallel to R11. And resistance R4, resistance
The divided voltage of R5, resistor R11 and resistor R14 is fed back to control circuit 4 and boosted chopper circuit 3
Keep the output constant. That is, when the output voltage of the inverter circuit 5 is high, the impedance of the inverter circuit 5 as viewed from the boost chopper circuit 3 is high, so that the voltage of the fluorescent lamp FL can be suppressed.

On the other hand, when the control circuit 6 changes the switching frequency of the transistors Q3 and Q4 to change the resonance, thereby narrowing the output of the inverter circuit 5 and dimming the fluorescent lamp FL, the inverter circuit 5
And the impedance of the inverter circuit 5 as viewed from the boost chopper circuit 3 is low, so that the voltage of the fluorescent lamp FL increases. In addition, since the voltage drop of the resistor R12 is small, the apparent resistance value between the emitter and the collector of the transistor Q11 increases, and in some cases, the transistor Q11 is turned off, and the input becomes apparently higher even when the voltage value of the capacitor C3 is the same. For this reason, the boost chopper circuit 3 is controlled so as to suppress the output as compared with the case of all-light dimming. Then, compared with the case where the output of the inverter circuit 5 is a high output,
Is low, the output of the boost chopper circuit 3 decreases. Since the transistor Q11 performs the class A operation, the output of the boosting chopper circuit 3 changes continuously, and the brightness of the fluorescent lamp FL can be continuously adjusted from dimming to full light.

Therefore, when the output of the inverter circuit 5 is reduced, the output of the boosting 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 and the fluorescent lamp FL is reduced. The input output can be reduced, and the fluorescent lamp FL can be easily dimmed.

Next, another embodiment will be described with reference to FIG.

The embodiment shown in FIG. 3 is different from the embodiment shown in FIG. 1 in that the output is switched between all stages and dimming. The current detection circuit 11 is connected to the base of the transistor Q12 via the resistor R13 and the Zener diode ZD1, and the collector and the emitter of the transistor Q12 are connected to both ends of the resistor R11.

The embodiment shown in FIG. 3 also corresponds to FIG.
However, in the all-lights-on state, the lamp current is large, the voltage of the resistor R12 increases, the Zener diode ZD1 turns on, and the transistor Q11 turns on. By bypassing the resistor R11, the output of the boost chopper circuit 3 is controlled by the voltage division of the resistors R4 and R5, so that the boost chopper circuit 3 outputs a large output.

On the other hand, in the dimming lighting state, since the lamp current is small, the voltage of the resistor R12 decreases, the Zener diode ZD1 becomes lower than the Zener voltage, the transistor Q11 is turned off, and the resistors R4, R5 and R11 are turned off. The boost chopper circuit 3 is controlled by the divided voltage, and the input becomes apparently higher even when the voltage value of the capacitor C3 is the same. Therefore, the boost chopper circuit 3 is controlled to suppress the output as compared with the case of all-light lighting.

[0027]

According to the discharge lamp lighting device of the present invention, when the output of the inverter circuit is reduced to dimm the discharge lamp, a change in the lamp current is detected by the current detection circuit. Since the output of the chopper circuit is varied in accordance with the supplied current, the discharge lamp can be appropriately dimmed by using a lamp current whose change due to temperature is smaller than the lamp voltage without increasing the control range of the inverter circuit.

According to the discharge lamp lighting device of the second aspect,
In addition to the discharge lamp lighting device according to the first aspect, since the inverter circuit is capable of continuous dimming, the output of the chopper circuit can be changed in accordance with the continuous dimming.

According to the discharge lamp lighting device of the third aspect,
In addition to the discharge lamp lighting device according to the first aspect, since the inverter circuit can perform stepwise dimming, the output of the chopper circuit can also be changed in accordance with the stepwise dimming.

[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 discharge lamp lighting device according to another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a conventional discharge lamp lighting device.

[Explanation of symbols]

 3 Boost chopper circuit 5 Inverter circuit 11 Current detection circuit FL Fluorescent lamp as discharge lamp

Claims (3)

[Claims] 1. A chopper circuit for boosting the output voltage with a variable output, an inverter circuit capable of converting the output of the chopper circuit into an alternating current and capable of dimming and lighting a discharge lamp with a variable output, and detecting the current of the discharge lamp and detecting the current. And a current detection circuit for varying the output of the chopper circuit according to the applied current. 2. The discharge lamp lighting device according to claim 1, wherein the inverter circuit is capable of continuous dimming. 3. The discharge lamp lighting device according to claim 1, wherein the inverter circuit can perform stepwise dimming.