JPH07169583A - Discharge lamp lighting circuit - Google Patents

Abstract

PURPOSE:To properly control supply voltage to a discharge lamp before and after the discharge lamp is lighted as well as to attain downsizing or the like of a device. CONSTITUTION:A lighting circuit 1 has a starting circuit 16 to generate a starting pulse only in a certain polarity of rectangular wave shaped voltage by a DC-AC converting circuit 7. When a frequency of output voltage of the DC-AC converting circuit 7 is heightened when an unlighted condition of a discharge lamp 20 is discriminated by a lighting discriminating-frequency control part 26, resonance of an inductor 11 and a capacitor 14 arranged in the rear stage of the DC AC converting circuit 7 is caused. A capacitor 75 in the starting circuit 16 is charged with electricity by the resonance voltage, and the stating pulse is generated by yield of a self-yielding type switching element 73.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel discharge lamp lighting circuit. More specifically, the present invention provides a novel discharge lamp lighting circuit capable of appropriately controlling the supply voltage to the discharge lamp before and after lighting the discharge lamp, and enabling downsizing of the device. .

[0002]

2. Description of the Related Art Regarding AC lighting of a discharge lamp such as a metal halide lamp, a DC input voltage is boosted by a DC boosting circuit and then converted into an AC by a DC-AC converting circuit in a subsequent stage to supply this to the discharge lamp. Lighting circuits are known.

When starting the discharge lamp,
The starting circuit provided in the subsequent stage of the DC-AC conversion circuit is configured as an LC resonance circuit having an inductor and a capacitor, and the resonance boosts the output (several hundred volts) of the DC-AC conversion circuit to increase its high voltage (tens of volts). There is a circuit that turns on the discharge lamp in kilovolts.

However, in the above-mentioned lighting circuit, the output of the DC-AC conversion circuit is boosted to a voltage of several tens of times due to resonance, resulting in a large power loss and a large withstand voltage of the resonance capacitor, resulting in a large device. There is an inconvenience such as becoming a cause of deterioration.

Therefore, a circuit is known in which a starting pulse is generated at the time of starting the discharge lamp, and this pulse is superimposed on the output of the DC-AC conversion circuit and applied to the discharge lamp. For example, a capacitor charged by the output of the DC-AC converter circuit and a self-breakdown type switch element that breaks down when the terminal voltage of the capacitor exceeds a predetermined value are provided, and the capacitor is charged on the power supply line to the discharge lamp. A series circuit is formed by the primary winding of the transformer provided with the secondary winding, the capacitor and the self-breakdown type switch element, and the pulse generated by the breakdown of the self-breakdown type switch element is boosted by the transformer to generate a direct current. A lighting circuit configured to be superimposed on the output of the AC conversion circuit.

[0006]

However, in such a lighting circuit, there is a problem that it is difficult to obtain an appropriate output of the DC-AC conversion circuit before and after lighting the discharge lamp.

That is, in order to guide the discharge lamp to a stable lighting state so that the discharge lamp does not go out when the discharge lamp is changed from the glow discharge to the arc discharge, a direct current-
A relatively high voltage of several hundreds of volts is required as the output of the AC conversion circuit, but if the output of the DC-AC conversion circuit after starting the discharge lamp remains at this high voltage value, the discharge lamp will steadily light up. Occasionally, a voltage higher than necessary is applied to the discharge lamp, which has an adverse effect on the life of the discharge lamp, a reduction in circuit efficiency, and an increase in the size of the device due to high breakdown voltage of components.

[0008]

Therefore, in order to solve the above-mentioned problems, the lighting circuit of the discharge lamp according to the present invention converts the DC input voltage into the AC voltage and supplies it to the discharge lamp.
A discharge lamp lighting circuit including an AC conversion circuit and a starting circuit for generating a start pulse for the discharge lamp and applying the start pulse to the discharge lamp has the following configurations (a) to (e). It is a thing.

(A) An inductor is connected in series to the discharge lamp and a capacitor is connected in parallel to the discharge lamp in the subsequent stage of the DC / AC converting means.

(B) A frequency control means for changing the frequency of the output voltage of the DC-AC conversion circuit is provided.

(C) A lighting judging means for judging whether or not the discharge lamp is lit is provided.

(D) When the lighting judging means judges the non-lighting state of the discharge lamp, the frequency controlling means sets the frequency of the output voltage of the DC-AC converting means to a value sufficient to cause series resonance by the inductor and the capacitor. Higher again
When the lighting determination means determines the lighting state of the discharge lamp, the frequency control means lowers the frequency of the output voltage of the DC-AC conversion circuit.

(E) The starting circuit includes a capacitor charged by the resonance voltage of (d), and a self-breakdown switch for causing a start-up pulse by breaking down when the terminal voltage of the capacitor reaches a predetermined voltage. It has an element.

[0014]

According to the present invention, the frequency control means increases the frequency of the output voltage of the DC-AC conversion circuit when the lighting determination means determines the non-lighted state of the discharge lamp, whereby the DC-AC conversion circuit is operated. Inducing resonance of a resonance circuit consisting of an inductor and a capacitor provided in the latter stage,
Since the resonance voltage charges the capacitor of the starting circuit and the starting pulse can be generated by the breakdown of the self-breakdown type switch element, the high voltage necessary for starting the discharge lamp can be temporarily obtained by the resonance circuit. In addition, it is possible to smoothly shift the state of the discharge lamp from glow discharge to arc discharge by the resonance sustaining voltage, and lower the frequency of the output voltage of the DC-AC conversion circuit after lighting the discharge lamp. By this, it is possible to control so that an excessive voltage is not applied to the discharge lamp during steady lighting of the discharge lamp.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the lighting circuit of the discharge lamp of the present invention will be described below with reference to the illustrated embodiments. The illustrated embodiment is one in which the present invention is applied to the lighting circuit 1 of a metal halide lamp for automobiles.

FIG. 1 shows an outline of the lighting circuit 1, in which a battery 2 is connected between the DC voltage input terminals 3 and 3 '.

Reference numerals 4 and 4'represent DC power supply lines, and a lighting switch 5 is provided on one of the lines 4 and
A current detecting resistor 6 is provided on the other line 4 '.

Reference numeral 7 denotes a DC-AC conversion circuit, which is provided to convert the battery voltage into a rectangular wave AC voltage.

As shown in FIG. 2, the DC / AC converting circuit 7 has a push-pull type DC-AC converter, and is a semiconductor switch provided on the primary winding 8a side of the transformer 8. The element 9 (i) (i = 1, 2) is reciprocally switching-controlled by a signal from the drive control circuit 10.

The DC power supply line 4 is connected to the center tap of the primary winding 8a of the transformer 8, and the semiconductor switch elements 9 (1) and 9 (2) have N-channel MOSFETs.
In the case of using, the sources of both FETs are shared and connected to the DC power supply line 4 ', and these drains are connected to the respective terminals of the primary winding 8a of the transformer 8. Then, a control signal from the drive control circuit 10 is supplied to each gate of the FETs. The drive control circuit 1
The configuration of 0 will be described later.

Reference numeral 11 is an inductor, which is a transformer 2
One end of the secondary winding 8b and one of the AC output terminals 12 and 12 '
It is provided on a power supply line 13 that connects the two.

Reference numeral 14 denotes a capacitor that forms a resonance circuit together with the inductor 11, one end of which is connected to a terminal of the inductor 11 on the side opposite to the secondary winding 8b.
The other end is connected to a power supply line 13 'connecting one end of the secondary winding 8b of the transformer 8 and the AC output terminal 12'.

Reference numerals 15 and 15 are voltage dividing resistors, which are provided in parallel with the capacitor 14 between the power supply lines 13 and 13 '.

Reference numeral 16 is a starting circuit, which is composed of a transformer 17 and a starting pulse generator 18. One end of the secondary winding 17b of the transformer 17 is connected between the inductor 11 and the capacitor 14 via the capacitor 19, and the other end is connected to the AC output terminal 12, and the starting pulse generator 18 causes the transformer 17 to The pulse generated in the primary winding 17a of the No. 17 is boosted and superposed on the output of the DC-AC conversion circuit 7.

A metal halide lamp 20 is connected between the AC output terminals 12 and 12 '. DC-
The rectangular wave output from the AC conversion circuit 7 is the inductor 11,
By passing through the capacitor 14, the transformer 17, etc., a waveform similar to a sine wave is obtained and the metal halide lamp 20
Is supplied to.

Reference numeral 21 is a current transformer, which is provided on the power supply line 13 '.

Reference numeral 22 denotes a control circuit, which is a voltage detection unit 23,
The current detection unit 24, the error amplifier 25, the lighting determination / frequency control unit 26, and the frequency variable oscillation unit 27 are included.

The voltage detector 23 is provided to detect the battery voltage, and its detection point is the rear end of the lighting switch 5. Then, the output signal is sent to the error amplifier 25 in the subsequent stage.

The current detector 24 is provided for detecting the battery current, and the battery current is converted into a voltage by the current detection resistor 6 and input. Then, the output signal is sent to the error amplifier 25 in the subsequent stage.

The addition signal of the output signal of the voltage detection unit 23 and the output signal of the current detection unit 24 is input to the error amplifier 25, and the difference signal between this and a predetermined reference voltage is used as the variable frequency oscillation in the subsequent stage. It is sent to the unit 27. That is, the error amplifier 25 is provided to control the level of the addition signal to be a constant value.

The lighting determination / frequency control unit 26 determines whether the metal halide lamp 20 is in a lighting state or a non-lighting state, and when it is determined that the metal halide lamp 20 is in a non-lighting state, controls the variable frequency oscillating unit 27. It is provided to send a signal and temporarily increase the rectangular wave voltage output from the DC-AC conversion circuit 7. A detection signal from the current transformer 21 and the voltage dividing resistors 15 and 15 is input to the lighting determination / frequency control unit 26, and the metal halide lamp 20 is detected based on the detection signal from the current transformer 21.
The metal halide lamp 2 is discriminated whether or not is lit.
When 0 is in the non-lighting state, a signal for controlling the output voltage detected by the voltage dividing resistors 15 and 15 to have a predetermined value is sent to the frequency variable oscillator 27.

The variable frequency oscillating section 27 generates a signal having an oscillating frequency which changes according to the signals from the error amplifier 25 and the lighting discrimination / frequency controlling section 26 and sends it to the drive control circuit 10. Thus, the frequency of the rectangular wave output from the DC-AC conversion circuit 7 is controlled.

FIG. 3 shows a configuration example of the control circuit 22.

The voltage detecting section 23 has a structure of a voltage buffer using an operational amplifier 28.
The divided voltage value of the battery voltage is input to the non-inverting input terminal of the battery by the voltage dividing resistors 29 and 29 '. In addition, one end of the resistor 29 is connected to the DC power supply line 4, and the other end thereof is a resistor 29 '.
A zener diode 30 and a capacitor 31 are provided in parallel with the resistor 29 '.

The current detector 24 is a non-inverting amplifier circuit using an operational amplifier 32, and the voltage detected by the current detecting resistor 6 is applied to the non-inverting input terminal of the operational amplifier 32 by the voltage dividing resistors 33, 33 '. Be entered via. A resistor 34 is inserted between the output terminal and the inverting input terminal of the operational amplifier 32, and the inverting input terminal of the operational amplifier 32 is a resistor 3.
It is grounded through 5.

The error amplifier 25 is constructed by using an operational amplifier 36, the non-inverting input terminal of which has an operational amplifier 28,
The output of 32 is input through resistors 37 and 38, respectively. Further, the reference voltage Eref is supplied to the inverting input terminal of the operational amplifier 36, and the resistor 39 is inserted between the output terminal of the operational amplifier 36 and the inverting input terminal.

In the lighting discrimination / frequency control unit 26, the detection voltage by the voltage dividing resistors 15 and 15 is supplied to the inverting input terminal of the operational amplifier 40 which constitutes the inverting amplifier circuit, and is supplied to the non-inverting input terminal of the operational amplifier 40. The reference voltage is changed depending on the detected value of the lamp current by the current transformer 21.

That is, the anode of the diode 41 is connected between the voltage dividing resistors 15 and 15, and the cathode of the diode 41 is connected to the resistor 4.
It is connected to the inverting input terminal of the operational amplifier 40 via 2 and is grounded via the capacitor 43.

Further, one end of the secondary winding of the current transformer 21 is grounded via the Zener diode 44 and is also connected via a resistor 45 to the base of an NPN transistor 46 whose emitter is grounded.
Is connected between the voltage dividing resistors 47 and 48. A predetermined voltage Vcc is supplied to one end of the voltage dividing resistor 47, and the other end is grounded via the voltage dividing resistor 48 and connected to the non-inverting input terminal of the operational amplifier 40 via the resistor 49.

Reference numeral 50 denotes a diode, the anode of which is connected to the output terminal of the operational amplifier 40 and the cathode of which is connected to the inverting input terminal of the operational amplifier 40 via the resistor 51.

The variable frequency oscillating section 27 has a CR oscillating circuit using a variable capacitance diode, and by using a variable capacitance diode, the circuit configuration is different from that in the case of performing power control such as a pulse width control method. Is simplified.

Reference numeral 52 is a variable capacitance diode, the cathode of which is connected to the cathode of the diode 50 and the output terminal of the operational amplifier 36 through the resistor 53, and the anode of which is grounded.

Reference numeral 54 is a NOT Schmitt trigger, the input terminal of which is connected to the cathode of the variable capacitance diode 52 via the capacitor 55.

Reference numeral 56 is a resistor provided in parallel with the NOT Schmitt trigger 54.

Reference numeral 57 is a waveform shaping section provided after the NOT Schmitt trigger 54, and obtains a narrow rising differential waveform slightly delayed from the rising of the output of the NOT Schmitt trigger 54. As shown in FIG. 4, NO
The output of the T-Schmitt trigger 54 is branched into two, one of which is input to one input terminal of the 2-input NAND Schmitt trigger 58, and the other of which is the NOT Schmitt trigger 59,
It is input to the remaining input terminal of the NAND Schmitt trigger 58 via the integrating circuit 62 including the resistor 60 and the capacitor 61.

Reference numerals 63 and 64 denote NOT Schmitt triggers, one of which 63 is provided after the NAND Schmitt trigger 58, and the other 64 is of the NOT Schmitt trigger 6.
It is provided in the latter part of 3. The outputs of the NOT Schmitt triggers 63 and 64 are both sent to the drive control circuit 10 of the DC-AC conversion circuit 7.

The drive control circuit 10 has the role of accelerating the switching speed of the drive signal to the semiconductor switch elements 9 (1) and 9 (2), and shaping the waveform so that the drive signal includes a dead time.

As shown in the configuration example of FIG. 4, the drive control circuit 10 includes D-type flip-flops 65 and 66 and a 2-input NA.
It is composed of ND Schmitt triggers 67 and 68, NOT Schmitt triggers 69 and 70, and complementary pairs 71 and 72.

The output signal of the NOT Schmitt trigger 64 is input to the clock input terminal (CK) of the D flip-flop 65, and its Q output terminal is input to one of the input terminals of the NAND Schmitt trigger 67. Incidentally, D
The Q-bar output signal of the type flip-flop 65 is sent to the D input terminals of the D-type flip-flops 65 and 66, respectively, and to one of the input terminals of the NAND Schmitt trigger 68.

The output signal of the NOT Schmitt trigger 63 is input to the clock input terminal (CK) of the D-type flip-flop 66, and its Q output terminal is NAND.
It is input to the remaining input terminals of the Schmitt trigger 67.
The Q-bar output signal of the D-type flip-flop 65 is NA
It is sent to the remaining input terminals of the ND Schmitt trigger 68.

The output signals of the NAND Schmitt triggers 67 and 78 are sent to the complementary pairs 71 and 72 via the NOT Schmitt triggers 69 and 70 in the subsequent stages, respectively.

The outputs of the complementary pairs 71 and 72 are the semiconductor switch elements 9 of the DC-AC converter circuit 7.
They are sent as drive signals to (1) and 9 (2), respectively.

As shown in FIG. 2, the starting pulse generator 18 causes a pulse to be generated on the primary side of the transformer 17 due to the breakdown of the self-breakdown type switch element when the charging voltage of the capacitor reaches a predetermined voltage. Is configured.

One end of the primary winding 17a of the transformer 17 has 2
It is connected between the secondary winding 17b and the capacitor 19, and the other end is connected to one terminal of a self-breakdown type switch element 73 (indicated by a switch symbol in the figure) such as a spark gap.

74 is a diode, the anode of which is connected to the capacitor 19 and the transformer 17 via the capacitor 75.
Of the secondary winding 17b, and its cathode is connected to the power supply line 13 '.

In the control circuit 22, however, the battery voltage is divided by the voltage dividing resistors 29, 29 'and sent to the operational amplifier 28 of the voltage detecting section 23, and the battery current is changed to the current detecting resistor 6'. Is detected by and is sent to the operational amplifier 32 of the current detector 24 and amplified.

Then, the output of the operational amplifier 28 and the output of the operational amplifier 32 are added at a predetermined ratio, and this is sent to the error amplifier 25, where it is compared with the reference value Eref.

The error voltage is supplied to the variable capacitance diode 52 of the variable frequency oscillator 27 via the resistor 53, and the oscillation frequency changes accordingly. That is, when the error voltage is large, the reverse bias voltage of the variable capacitance diode 52 is large, so that the junction capacitance becomes small and the oscillation frequency becomes high.

The control voltage for the variable capacitance diode 52 is also given from the lighting discrimination / frequency control section 26.

At the time of starting the lamp, the operational amplifier 40 becomes the mainstream of control, leaving the power control system consisting of the voltage detector 23, the current detector 24, and the error amplifier 25.

When it is detected by the current transformer 21 that no lamp current is flowing, the transistor 4
6 is turned off, the operational amplifier 40 divides the voltage dividing resistor 15,
A control voltage such that the terminal voltage of the capacitor 14 detected by 15 becomes a predetermined voltage (defined by the divided value of Vcc by the voltage dividing resistors 47 and 48) is supplied to the variable capacitance diode 52. That is, the operational amplifier 40 is the error amplifier 25 that compares the lamp voltage with the reference voltage, and the variable capacitance diode 52 is controlled by the control voltage.
The junction capacitance of the variable frequency oscillator 2,
The oscillation frequency of 7 changes.

When the lamp voltage is low, the operational amplifier 4
Since the control voltage of 0 is large, the applied voltage to the varactor diode 52 is large and the junction capacitance of the varactor diode 52 is small, so that the oscillation frequency of the frequency variable oscillator 27 is substantially equal to the resonance frequency of the inductor 11 and the capacitor 14. Up to the value.

When the transistor 46 is turned on by the lamp current detected by the current transformer 21, the non-inverting input terminal of the operational amplifier 40 is fixed to the zero level and the diode 50 is not conducted, so that the power control is performed. As the lamp approaches a steady state, the oscillation frequency of the variable frequency oscillating unit 27 decreases and approaches a predetermined value.

The output signal of the variable frequency oscillating unit 27 is sent to the drive control circuit 10, where the output signal 2 including the dead time is included.
A rectangular wave signal having two almost opposite phase relations is obtained.

The output signal of the NOT Schmitt trigger 63 and the output signal of the NOT Schmitt trigger 64 are signals that are in antiphase with each other, and the Q output signals of the flip-flops 65 and 66 are frequency-divided signals of these signals. The Q output signal of 66 is slightly delayed from the Q output signal of the flip-flop 65. Then, by taking the logical product of the Q outputs of the output signals of these flip-flops 65 and 66 and the Q bar outputs, two signals having a dead time are obtained. Then, by these signals, the semiconductor switch element 9 of the DC-AC conversion circuit 7
(1) and 9 (2) are driven.

As described above, before the lamp is turned on, the oscillating frequency of the variable frequency oscillating unit 27 becomes high and the inductor 1
1 and the capacitor 14 cause resonance, which boosts the output voltage of the DC-AC conversion circuit 7 by several times. It should be noted that this temporary boosting does not cause a significant reduction in the efficiency of the circuit or the withstand voltage of the circuit component becoming extremely high.

The starting pulse generator 18 is driven by the resonance voltage.
The internal capacitor 75 is charged, and when its terminal voltage exceeds a predetermined voltage, the self-breakdown type switch element 73 breaks down and a pulse is generated on the primary side of the transformer 17, which is boosted by the transformer 17. A starting pulse of several tens of kilovolts is applied to the metal halide lamp 20 to start the lamp.

After the lamp is turned on, the variable frequency oscillator 2
Although the oscillating frequency of No. 7 becomes low, a relatively high voltage is supplied to the metal halide lamp 20 due to the continuation of the resonance shortly after the lamp is turned on (about 0.1 to 1 ms). To arc discharge is promoted.

Then, the frequency is controlled by the power control system, the resonance by the inductor 11 and the capacitor 14 is eliminated, and the constant power control of the lamp is finally performed to stabilize the lighting state.

[0070]

As is apparent from the above description, according to the lighting circuit of the discharge lamp of the present invention, the frequency of the output voltage of the DC-AC conversion circuit is determined when the non-lighting state of the discharge lamp is determined. By increasing it, it causes the resonance of the resonance circuit consisting of the inductor and the capacitor provided in the latter stage of the DC-AC conversion circuit, and the resonance voltage charges the capacitor of the startup circuit to start by the breakdown of the self-breakdown switch element. Because it can generate a pulse,
The high voltage necessary for starting the discharge lamp can be temporarily obtained by the resonance circuit, and the state of the discharge lamp can be smoothly changed from glow discharge to arc discharge by the continuous voltage of the resonance. By lowering the frequency of the output voltage of the DC-AC conversion circuit after lighting the lamp, the supply voltage to the discharge lamp can be appropriately controlled so that an excessive voltage is not applied to the discharge lamp during steady lighting of the discharge lamp. .

Therefore, it is possible to avoid inconveniences such as an influence on the life of the discharge lamp, a decrease in the efficiency of the circuit, and an increase in the size of the device due to the high breakdown voltage of the parts.

Further, if the frequency control means is composed of a CR oscillating section using a variable capacitance diode, the circuit structure can be simplified.

The specific circuit configurations shown in the above embodiments are merely examples for embodying the present invention, and the technical scope of the present invention is limitedly interpreted by these. Not something.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an outline of a lighting circuit of a discharge lamp according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a DC-AC conversion circuit and a starting circuit.

FIG. 3 is a circuit diagram showing a configuration of a control circuit.

FIG. 4 is a circuit diagram showing configurations of a variable frequency oscillator and a drive control circuit.

[Explanation of symbols]

 1 Discharge Lamp Lighting Circuit 7 DC-AC Converter Circuit 11 Inductor 14 Capacitor 16 Starting Circuit 20 Discharge Lamp (Metal Halide Lamp) 21, 26 Lighting Discrimination Means 26, 27 Frequency Control Means 73 Self-breakdown Switch Element 75 Capacitor

Claims (2)

[Claims] 1. A DC-AC conversion circuit for converting a DC input voltage into an AC voltage and supplying the AC voltage to a discharge lamp, and a starting circuit for generating a pulse for starting the discharge lamp and applying it to the discharge lamp. In the lighting circuit of the discharge lamp, (a) the inductor was connected in series to the discharge lamp and the capacitor was connected in parallel to the discharge lamp in the subsequent stage of the DC-AC conversion circuit, and (B) DC-AC. The frequency control means for changing the frequency of the output voltage of the conversion circuit is provided,
(C) A lighting determination means for determining whether or not the discharge lamp is turned on is provided, and (d) the frequency control means sets a direct current when the unlit state of the discharge lamp is determined by the lighting determination means.
The frequency of the output voltage of the AC converting means is increased to a value sufficient to cause series resonance by the inductor and the capacitor, and when the lighting judging means judges the lighting state of the discharge lamp, the frequency control means makes the DC-AC converter circuit. The frequency of the output voltage of the
Of a discharge lamp having a capacitor charged by the resonance voltage of 1) and a self-breakdown type switch element for generating a starting pulse by breaking down when the terminal voltage of the capacitor reaches a predetermined voltage. Lighting circuit. 2. The discharge lamp lighting circuit according to claim 1, wherein the frequency control means is a C using a variable capacitance diode.
A lighting circuit for a discharge lamp, comprising an R oscillating section, wherein the frequency of the output voltage of the DC-AC conversion circuit is changed by controlling the variable capacitance diode according to the signal from the lighting discrimination means.