JPH11307295A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device capable of reducing an effective value of a voltage applied to a discharge lamp when no load is applied, and also capable of smoothly transferring from a grow discharge to an arc discharge. SOLUTION: This discharge lamp lighting device is equipped with an inverter circuit part 3 to supply a rectangular wave AC power to a discharge lamp 4 from a direct current power source 2, and when starting, a high voltage pulse is applied to the discharge lamp 4 by a high voltage pulse generating means 32, in order to start the discharge lamp 4. In this case, a direct current voltage with its peak voltage value pulsing is supplied to the discharge lamp 4 when no load is applied, and at least one high voltage pulse is superimposed on a part having the highest voltage peak. The inverter circuit part 3 consists of a pressure lowering chopper circuit part 30 to lower the output voltage of the direct current power source 2, for instance, and a polarity reversing circuit part 31 with a bridge structure to convert the output voltage of the voltage lowering chopper circuit part 30 to a low frequency AC current voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-pressure discharge lamp lighting device for lighting a high-pressure discharge lamp, such as a mercury lamp or a metal halide lamp, which needs to apply a high-pressure pulse at the time of starting.

[0002]

2. Description of the Related Art Conventionally, a copper-iron type ballast has been mainly used as a lighting device for lighting a high pressure discharge lamp. However, in recent years,
Electronic ballasts using many electronic components for the purpose of reducing the weight, size, and function of ballasts are becoming mainstream. This electronic ballast will be briefly described below.

FIG. 12 shows a block diagram of an electronic ballast. A DC power supply circuit section 2 including a rectifier circuit is connected to an AC power supply 1, and an inverter circuit section 3 that can adjust and control power supplied to the lamp 4 at an output terminal of the DC power supply circuit section 2.
Are connected, and a lamp 4 is connected to an output terminal of the inverter circuit unit 3.

FIG. 13 shows an example of a specific circuit of an electronic ballast. The DC power supply circuit unit 2 includes a rectifier circuit DB, an inductor L0, a switching element Q0, and a diode D0.
And a step-up chopper circuit including a capacitor C0,
The control circuit 5 has a function of converting an AC voltage of the AC power supply 1 into a desired DC voltage. The inverter circuit section 3 includes a step-down chopper circuit section 30, a polarity inversion circuit section 31, an igniter circuit section 32, and a control circuit 6.
The step-down chopper circuit section 30 includes a switching element Q1.
, A diode D1, an inductor L1, and a capacitor C1. The input DC voltage is reduced and output. here,
The operation of the step-down chopper circuit is a general technique, and a description thereof will be omitted. Next, the polarity reversing circuit unit 31 includes switching elements Q2 to Q5, and forms a full bridge circuit. In the polarity inversion circuit section 31, the switching elements Q2 to Q5 perform the operation shown in FIG. Next, the igniter circuit unit 32
It comprises a capacitor T2, a capacitor C2, a switching element Q6 (for example, a voltage responsive element such as Sidac), and a resistor R2.

The operation of the igniter circuit section 32 will be briefly described with reference to FIG. The polarity inversion circuit section 3
1 generated from the square wave voltage Va− shown in FIG.
b, the voltage Vc2 of the capacitor C2 is gradually charged as shown in FIG. 15B by the time constant of the resistor R2 and the capacitor C2. When the voltage Vc2 of the capacitor C2 reaches the breakover voltage Vbo of the switching element Q6, the switching element Q6 is turned on, and the charge accumulated in the capacitor C2 is transferred to the capacitor C2 and the switching element Q6.
6. Discharge through the primary winding of the pulse transformer PT. At this time, the pulse voltage generated in the pulse transformer PT is boosted, and a high-voltage pulse voltage (several kV) is generated in the secondary winding of the pulse transformer PT. Then, the discharge lamp 4 starts discharging by the high voltage pulse voltage, and shifts to a lighting state.

Further, the control circuit 6 detects the lamp voltage Vla of the lamp 4 (current or power may be used), controls ON / OFF of the switching element Q1 according to the lamp voltage, and adjusts the power supplied to the lamp. ing.

In the above-described discharge lamp lighting device,
Since a rectangular wave AC voltage is supplied to the lamp 4 even when there is no load, the lamp 4 is starting to light up after dielectric breakdown due to a high voltage pulse. , The discharge is difficult to maintain, the transition to the steady lighting cannot be smoothly performed, and the starting performance deteriorates.

In order to solve such a problem, Japanese Patent Application Laid-Open No. 3-283393 is disclosed. In the present invention, when no load is applied, the voltage Vla applied to the lamp 4 is fixed to a DC voltage as shown in FIG. Although this method could slightly improve the starting performance of the lamp, it also has the following problems.

In general, a high-pressure discharge lamp that is started by a high-voltage pulse immediately after the dielectric breakdown is caused by the high-voltage pulse, unless the supply of energy is sufficient to maintain the discharge, the discharge stops, and the lamp is quickly started. It is difficult to shift from the state to the lighting state. That is, it is necessary to supply a sufficient no-load secondary voltage to the lamp 4 for a certain period immediately after the superposition of the high-voltage pulse. For this purpose, in the discharge lamp lighting device, the secondary voltage at the time of no load may be increased and supplied to the lamp 4. However, the effective value of the voltage generated between the output lines at the time of no load becomes high. It is not good for safety.

In order to solve such a problem, Japanese Patent Laid-Open No. 4-33296 has been proposed. According to the present invention, when no load is applied, the voltage Vla applied to the lamp 4 is set higher in the first half of the rectangular wave than in the second half as shown in FIG. Is secured. However, in this method, since the rectangular wave AC voltage is supplied to the lamp even when there is no load, it is difficult to maintain the discharge at the time of the polarity reversal described above, and it is not possible to smoothly shift to steady lighting, and the starting performance is deteriorated. Contains the problem.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to reduce the effective value of the voltage applied to a discharge lamp when there is no load. Another object of the present invention is to provide a discharge lamp lighting device capable of smoothly shifting from glow discharge to arc discharge.

[0012]

According to the present invention, in order to solve the above-mentioned problems, as shown in FIG.
Discharge lamp lighting, comprising an inverter circuit section 3 for supplying a rectangular wave AC power to the discharge lamp 4 from above, and applying a high-voltage pulse to the discharge lamp 4 at the time of starting by the high-voltage pulse generating means 32 to start the discharge lamp 4 The apparatus is characterized in that a pulsating DC voltage having a voltage peak value is supplied to the discharge lamp 4 when there is no load, and at least one high-voltage pulse is superimposed on a portion having a high voltage peak value.

[0013]

(Embodiment 1) FIG. 1 shows a main circuit of Embodiment 1 of the present invention. Further, the first and second embodiments of the present embodiment
2 and 3 are shown in FIGS. FIG. 4 is an operation waveform diagram of the present embodiment. In this embodiment, when no load is applied, a high-level pulse is applied to the lamp 4 at least at a position where the secondary voltage is high, with the no-load secondary voltage having a height. Hereinafter, details of the present embodiment will be described. The configuration of the main circuit shown in FIG. 1 is substantially the same as that of the conventional example (FIG. 13), except that the control circuit 6 sends the lighting determination signal A and the low frequency reference signal B to the control circuit 5.

FIG. 2 shows a detailed configuration of the control circuit 6. The lighting determination circuit 60 compares the lamp voltage Vla with a preset lighting determination voltage V1, and outputs a High-level signal as the output signal A when Vla> V1 (no load). Next, each of the oscillators 61 and 62 has a DC frequency at no load and a rectangular wave frequency at lighting (several tens to
It oscillates a low-frequency reference signal B of several hundred Hz).
Next, the frequency changeover switch 63 is turned on by the previous lighting determination circuit 60.
Is connected to the oscillator 61 when the output signal A is at a high level, and is connected to the oscillator 62 when the output signal A is at a low level. Lastly, the low-frequency drive circuit 64 divides the frequency of the signal from the oscillators 61 and 62,
1 to generate a signal for turning on / off the switching elements Q2 to Q5.

FIG. 3 shows a detailed configuration of the control circuit 5. The error amplifier 50 compares the output voltage Vc0 of the chopper circuit with the reference voltage V2 or V3 or V4, and outputs a voltage according to the difference. In response to this output, the duty setting circuit 51 calculates an appropriate ON duty and performs ON / OFF control of the switching element Q0.

Next, when the lighting determination signal A is at a low level (during lighting), the reference voltage switch 52 switches the reference voltage V
2, and when the lighting determination signal A is at the High level (when no load is applied), it is connected to the other (reference voltage switch 53). At this time, the reference voltage V2 means an output voltage of the chopper circuit required when the lamp 4 is turned on. Next, the timer circuit 54 is triggered by the rising portion of the low frequency reference signal B, and outputs a High level signal for a predetermined time T1 as shown in FIG. The low level signal is output to the section.

Next, the reference voltage switch 53 is connected to V4 when the output of the timer circuit 54 is at the high level, and V3 when the output of the timer circuit 54 is at the low level.
Connect to. At this time, the magnitude relationship between V3 and V4 is V4> V3.

With the above circuit, as shown in FIG. 4, when a high voltage and a low voltage are alternately applied to the lamp when there is no load and a high-voltage pulse is applied to the lamp when at least the secondary voltage is high, Good starting performance can be ensured while reducing the effective value of the secondary voltage.

(Embodiment 2) FIG. 5 shows a detailed configuration of a second control circuit according to Embodiment 2 of the present invention. Other configurations are the same as those of the first embodiment. This embodiment is characterized in that the voltage is gradually reduced during the low voltage period of the first embodiment when there is no load.

The details of this embodiment will be described below. FIG. 5 is a detailed diagram of the control circuit 5. The control power supply Vcc is divided by the resistors R8 and R9, and the same reference voltage V4 as in the previous embodiment is used.
Generate When the output of the timer circuit 54 is at the high level, the switching element Q7 is off, and the reference voltage is V4. When the output of the timer circuit 54 goes low, the switching element Q7 turns on and the resistance R
9 is connected in parallel with another resistor R7, so that the reference voltage gradually decreases from V4. The rate of decrease can be set by the capacitance of the capacitor C3 and the values of the resistors R7 to R9.

With the above circuit, as shown in FIG. 6, a substantially sawtooth DC voltage is applied to the lamp when no load is applied, and a high voltage pulse is applied to the lamp when at least the secondary voltage is high. , And good starting performance can be secured.

(Embodiment 3) FIG. 7 shows Embodiment 3 of the present invention. In this embodiment, the step-down chopper circuit section 30 and the polarity inversion circuit section 31 of the first or second embodiment are configured by a full bridge circuit 33 as shown in the figure. FIG. 8 shows ON / OFF operations of the switching elements Q2 to Q5 and lamp currents. Hereinafter, this circuit will be described. As shown in FIG. 8, the switching elements Q2 and Q5, and Q3 and Q4 are paired and repeat high-frequency switching. That is, the switching element Q1 in the circuit of FIG.
To Q5. In a cycle in which the switching elements Q2 and Q5 perform high-frequency switching, the energy of the inductor L2 when the switching element is OFF is fed back to the power supply via the diodes D3 and D4. In a cycle in which the switching elements Q3 and Q4 perform high-frequency switching, the energy of the inductor L2 when the switching element is OFF is fed back to the power supply via the diodes D2 and D5. That is, the diodes D2 to D5 function as the diode D1 in the circuit of FIG. With the above operation, the same rectangular wave AC power as in the first and second embodiments can be supplied to the lamp 4, and the same effect as in the first and second embodiments can be obtained.

In this embodiment, the switching element Q2
For example, if an element having a built-in diode such as an FET is used as Q5 to Q5, the diodes D2 to D5 can also be used as the diodes, and the number of switching elements and diodes used is 4 compared to 6 in the first embodiment. This is advantageous in terms of cost reduction and miniaturization.

The same applies to the operation of the switching elements Q3 and Q5 as shown in FIG. The operation in this case will be described below. The switching element Q2 repeats high-frequency switching while the switching element Q5 is ON, and the switching element Q4 repeats high-frequency switching while the switching element Q3 is ON, as shown in FIG. That is, the switching element Q1 in the circuit of FIG. 1 is also used as the switching elements Q2 to Q5 of the bridge circuit. In a cycle in which the switching element Q2 performs high-frequency switching, energy of the inductor L2 when the switching element is OFF is consumed in the lower loop of the bridge circuit via the switching element Q5 and the diode D3. In a cycle in which the switching element Q4 performs high-frequency switching, the energy of the inductor L2 when the switching element is OFF is consumed in the lower loop of the bridge circuit via the switching element Q3 and the diode D5. That is, the diodes D3 and D5 are connected to the diode D1 in the circuit of FIG.
It is acting as. In the case of this switching mode, the diodes D2 and D4 in FIG. 7 become unnecessary.

(Embodiment 4) FIG. 10 shows the configuration of Embodiment 4 of the present invention. In this embodiment, the step-down chopper circuit section 30 and the polarity inversion circuit section 31 of the first embodiment are configured by a half bridge circuit 34 as shown in the figure. FIG. 11 shows the ON / OFF operation of the switching elements Q2 and Q3 and the lamp current. Hereinafter, the operation of this circuit will be described. The switching elements Q2 and Q3 repeat high-frequency switching as shown in FIG. 11, respectively.
That is, the switching elements Q2 and Q3 of the present embodiment also serve as the switching elements Q1, Q2 to Q5 in the circuit of FIG. In a cycle in which the switching element Q2 performs high-frequency switching, the energy of the inductor L1 when the switching element is OFF is fed back to the capacitor C02 via the diode D3. In a cycle in which the switching element Q3 performs high-frequency switching, the energy of the inductor L1 when the switching element is OFF is fed back to the capacitor C01 via the diode D2. That is, the diodes D2 and D3 substitute the diode D1 in the circuit of FIG. By the above operation, the same alternating current as in the first embodiment can be applied to the lamp 4, and the same control as in the first embodiment can be performed.

In this embodiment, the switching element Q
For example, if an element with a built-in diode such as an FET is used for Q2 and Q3, the diodes D2 and D3 can be shared by these diodes, and the number of switching elements and diodes used is 2 and 6 in the first embodiment. This is advantageous in terms of cost reduction and miniaturization.

[0027]

According to the present invention, in a discharge lamp lighting device having a DC power supply circuit section and an inverter circuit section, when no load is applied, a pulsating DC voltage having a voltage peak value is supplied to the lamp, and the voltage peak value is increased. Since at least one high-voltage pulse is superimposed on the portion, the starting performance of the lamp can be improved while reducing the effective value of the voltage applied to the lamp when there is no load.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a main circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating a first control circuit according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram illustrating a second control circuit according to the first embodiment of the present invention.

FIG. 4 is an operation waveform diagram according to the first embodiment of the present invention.

FIG. 5 is a circuit diagram showing a second control circuit according to a second embodiment of the present invention.

FIG. 6 is an operation waveform diagram according to the second embodiment of the present invention.

FIG. 7 is a circuit diagram illustrating a main circuit according to a third embodiment of the present invention.

FIG. 8 is an operation waveform diagram according to the third embodiment of the present invention.

FIG. 9 is an operation waveform diagram in another control mode according to the third embodiment of the present invention.

FIG. 10 is a circuit diagram illustrating a main circuit according to a fourth embodiment of the present invention.

FIG. 11 is an operation waveform diagram according to the fourth embodiment of the present invention.

FIG. 12 is a block diagram showing a schematic configuration of a conventional example.

FIG. 13 is a circuit diagram showing a specific circuit configuration of a conventional example.

FIG. 14 is an explanatory diagram showing a switching operation of a conventional example.

FIG. 15 is an operation waveform diagram for explaining a conventional high-voltage pulse generation operation.

FIG. 16 is an operation waveform diagram of the second conventional example.

FIG. 17 is an operation waveform diagram of the third conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 DC power supply circuit part 3 Inverter circuit part 4 Lamp 5 Control circuit 6 Control circuit 30 Step-down chopper circuit part 31 Polarity inversion circuit part 32 Igniter circuit part

Claims (6)

[Claims] An inverter circuit for supplying a rectangular wave AC power from a DC power supply to a discharge lamp is provided, wherein a high-voltage pulse is applied to the discharge lamp by a high-voltage pulse generating means to start the discharge lamp. A discharge lamp lighting device characterized by supplying a pulsating DC voltage having a voltage peak value to a discharge lamp when no load is applied and superimposing at least one high-voltage pulse on a portion having a high voltage peak value. 2. The discharge lamp lighting device according to claim 1, wherein the DC voltage supplied to the discharge lamp when there is no load is a substantially sawtooth voltage. 3. The step-down chopper circuit section according to claim 1, wherein the inverter circuit section drops the output voltage of the DC power supply, and a full bridge that converts the output voltage of the step-down chopper circuit section into a low-frequency AC voltage. A discharge lamp lighting device, comprising: a polarity inversion circuit unit having a configuration. 4. The discharge lamp according to claim 1, wherein the inverter circuit section is configured by a full-bridge circuit that operates as a step-down chopper circuit by turning a switching element on and off at a high frequency. Lighting device. 5. The discharge lamp according to claim 1, wherein the inverter circuit section includes a half-bridge circuit that operates as a step-down chopper circuit by turning on / off a switching element at a high frequency. Lighting device. 6. The method according to claim 1, wherein
A discharge lamp lighting device, wherein the DC power supply is constituted by a chopper circuit including at least one switching element, a diode, and an inductance.