JPH1064688A - High brightness discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high brightness discharge lamp lighting device which does not use any inverter circuit of full bridge system, has a simple and low-cost circuit configuration, avoids occurrence of acoustic resonance phenomenon to establish stable lighting of a metal halide lamp, quickens the rising of a light flux after the start of the metal halide lamp, and can restrict the power supplied to the lamp so that it does not exceed the rated value. SOLUTION: In this device, there is provided with a warm-up circuit 13 which makes frequency modulation of the output of an inverter control circuit operating with a high frequency, avoids the occurrence of acoustic resonance phenomenon, and attenuates the sensitivity of a lamp current sensing circuit 12 with a prescribed ratio. Thereby the lamp start can be made certainly in a short time and at a high speed with the lamp current at starting held over the rating. A power limiting circuit 7 is furnished so as to have a rated operation even in the final period of lamp lifetime by adding the rated power during the steady operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-intensity discharge lamp lighting device for lighting a metal halide lamp at a high frequency.

[0002]

2. Description of the Related Art FIG. 14 is a circuit diagram of a conventional high-intensity discharge lamp lighting device. The commercial AC power supply AC is rectified by diodes D101 to D104, and its output is input to a boost chopper type sine wave converter circuit including a choke coil L101, a switching element SW101, a diode D105, a capacitor C101 and a capacitor C102. The inverter INV is connected to this converter circuit as its load.

[0003] A sine wave converter circuit of the boost chopper type will be briefly described. To make the waveform of the input voltage ei of the commercial AC power supply AC similar to the waveform of the input current Ii,
First, the voltage ei 'is detected by the resistors R101 and R102,
The signal is input to the terminal 1 of the multiplier MP1. At the same time, in order to stabilize the lamp current IL, the lamp current IL, that is, the output current of the inverter INV is changed to the lamp current detection resistor R10.
5 to obtain a variation ΔIL of the lamp current IL by a constant current circuit and input it to the terminal 2 of the multiplier MP1. Therefore, the output of MP1 becomes a current command value Ii * having a waveform similar to ei ', and its amplitude decreases as the lamp current IL increases. On the other hand, the current I
i ′ is detected, and Ii * and I
i ′ are compared. A PWM signal proportional to the difference between the two is generated by the drive circuit, and the switching element SW1 of the sine wave converter is driven. Therefore, since the average current for each switching is proportional to the input voltage, the high-frequency component of the switching waveform is removed by a low-pass filter using LF and CF, and as shown in FIG. The waveform becomes similar to the waveform of ei, and the suppression of harmonics of the power supply current and the high power factor of the power supply are achieved. At the same time, the lamp current IL is stabilized by the constant current control.

[0004] An inverter INV, which is a full-bridge type inverter circuit, is connected as a load to the boost chopper type sine wave converter. Note that TR
1 to TR4 are switching transistors constituting the inverter INV. The output of the inverter INV includes the secondary coil of the transformer T101 and the metal halide lamp ML.
Are connected in series. In FIG. 14, when power is supplied to the circuit, the timer circuit TM operates and outputs a start pulse trigger signal of 100 Hz to the start pulse generation circuit PG. The starting pulse generating circuit PG outputs a starting pulse for about 5 seconds. The starting pulse is boosted by the transformer T101 to generate a high voltage of 3 to 5 KV, and the high voltage starts the metal halide lamp ML. Further, the timer circuit TM outputs an inverter operation start signal to the oscillation circuit OSC, whereby the oscillation circuit OSC operates, and this output operates the drive circuit DCC. Drive circuit DCC
Drives the transistors TR1 to TR4 and drives the inverter I
NV operates. When the inverter INV operates, the metal halide lamp ML shifts from glow discharge to arc discharge and turns on.

[0005]

When a metal halide lamp is lit by an electronic lighting circuit, when the lamp is lit by a sine wave having a frequency of several hundred kHz or less, a characteristic characteristic of a high-intensity discharge lamp such as a metal halide lamp is given. The lighting state becomes unstable due to the acoustic resonance phenomenon, and the metal halide lamp may go out. This is a phenomenon in which the lighting state becomes unstable because a standing wave is generated in the discharge arc inside the arc tube, and the lamp lighting frequency is generated at a certain frequency within the range of several kHz to several hundred kHz. There are many. Therefore, in order to stably turn on the metal halide lamp, it is necessary to turn on the lamp at a high frequency of several hundred kHz or higher, or to turn on a rectangular wave or a direct current in which no acoustic resonance phenomenon occurs.

In the above-described conventional lighting device, the metal halide lamp ML is lit in a rectangular wave to avoid an acoustic resonance phenomenon. In the above-described full-bridge type inverter circuit, the switching frequency is usually lower than 400 Hz due to restrictions such as the switching speed of the switching element. Therefore, the size of the transformer T101 cannot be reduced. Further, there is a problem that the control circuit and the drive circuit of the full-bridge type inverter circuit are complicated and expensive. Therefore, it is difficult to reduce the size and cost.
In the above lighting device, the metal halide lamp ML
Is turned on with a constant lamp current, so it takes several minutes from the start of the lamp until the luminous flux reaches the rated value. Furthermore, since the lighting voltage of the metal halide lamp ML increases at the end of its life, excessive power is supplied to the metal halide lamp ML when the lamp current is controlled to be constant as in the lighting device described above. There is a problem that.

Therefore, the present invention does not use a full-bridge type inverter circuit, has a simple circuit configuration, is inexpensive, and can stably turn on a metal halide lamp by avoiding an acoustic resonance phenomenon. Starting a metal halide lamp It is an object of the present invention to provide a high-intensity discharge lamp lighting device capable of speeding up the subsequent light flux and limiting the power supplied to the metal halide lamp so as not to exceed a rated value.

[0008]

A rectifying / smoothing circuit of a commercial AC power supply, a power factor improving circuit connected to an output of the rectifying / smoothing circuit for outputting DC power and simultaneously improving a power factor of input AC power, An inverter connected to the output of the improvement circuit for supplying a high-frequency current to the metal halide lamp and lighting the lamp; a lamp current detection circuit for outputting a lamp current detection signal proportional to the magnitude of the lamp current; A high-intensity discharge lamp lighting device including an inverter control circuit that controls the intermittent interval of the power switch element of the inverter so as to be maintained at a value, connected to the inverter control circuit to reduce the ON interval of the power switch element of the inverter. Connected to a frequency modulation circuit that changes the determined time constant at a predetermined cycle and a lamp current detection circuit to start the metal halide lamp The power supply apparatus further includes a warm-up circuit that attenuates the lamp current detection sensitivity of the lamp current detection circuit in a predetermined period at a predetermined ratio, and has a power limiting circuit that limits the output power of the power factor correction circuit to a predetermined value or less. To provide a high-intensity discharge lamp lighting device.

[0009]

FIG. 1 shows a first embodiment of the present invention.
An outline of the circuit configuration and operation will be described. In FIG.
Power terminals 1 and 2 are connected to a commercial AC power source (for example, an effective voltage
100 V). The AC power input from the power supply terminals 1 and 2 is full-wave rectified by the diode bridge 3 including four diodes, and is input to the power factor correction circuit 4. The power factor improvement circuit 4 is a step-up chopper type circuit using a single power switch element. The power factor improving circuit 4 includes a power factor improving circuit control IC 6, and a power limiting circuit 7 is connected to the power factor improving circuit control IC 6. The power factor improvement circuit 4 operates so that the current waveform flowing through the power supply terminals 1 and 2 becomes a sine wave, and a high power supply power factor is obtained.
The output of the power factor correction circuit 4 outputs a DC output voltage Vdc (normally, 200 V), which is input to an inverter 8 connected to the output of the power factor correction circuit 4.

[0010] The inverter 8 is connected to an inverter control circuit 9 including an inverter control IC 10, and a frequency modulation circuit 11 is connected to the inverter control circuit 9. The power switch element (power MOSFET 51) constituting the inverter 8 is driven by the switching control signal output from the output terminal 11B of the inverter control IC, and the inverter 8 operates. An inductor 14 and a capacitor 15 are connected in series to the output of the inverter 8. In parallel with the capacitor 15, a metal halide lamp 16
(For example, rated power 70 W) and the lamp current detection circuit 12
Are connected in series.

When the metal halide lamp 16 is started, the switching frequency of the inverter 8 is changed to near the resonance frequency of the series resonance circuit composed of the inductor 14 and the capacitor 15, so that the peak value of the capacitor 15 is about 2 kVo-p. And the metal halide lamp 16 is started. After the lamp is started, the inverter 8 is operated at a switching frequency of about 300 kHz, and the lamp is supplied with the high-frequency current to perform high-frequency lighting. Note that the inductor 14 is for sharing the difference between the output voltage of the inverter 8 and the discharge sustaining voltage (about 100 V) of the metal halide lamp 16 during steady lighting.

The switching frequency of the inverter 8 is controlled by the frequency modulation circuit 11 connected to the inverter control circuit 9.
That is, the lighting frequency of the metal halide lamp 16 (hereinafter, referred to as
The lamp lighting frequency) is frequency-modulated with a modulation frequency of about 40 Hz and a frequency shift of about 15 kHz, so that the generation of a standing wave of the discharge arc that causes the acoustic resonance phenomenon is suppressed, and the acoustic resonance phenomenon is suppressed. By avoiding this, the metal halide lamp can be stably turned on at a high frequency.

The lamp current detection circuit 12 detects the lamp current and outputs a lamp current detection signal proportional to the magnitude of the lamp current to an output terminal 12A. The lamp current detection signal is input to the detection terminal 10A of the inverter control IC 10, and the inverter control IC 10 controls the operation of the inverter 8 by changing the switching control signal so that the voltage of the detection terminal 10A becomes constant. It is controlled below the set value.

A warm-up circuit 13 is connected to the output terminal 12A of the lamp current detection circuit 12, and a metal halide lamp 16
The lamp current detection sensitivity of the lamp current detection circuit 12 at the time of starting is set to about 0.7 times the steady state, and then the lamp current detection sensitivity is gradually increased so that the lamp current detection sensitivity becomes a steady value about 1 minute after starting. I have to. For this reason, the lamp current for about one minute after the start-up becomes larger than the rated value (about 0.7 A), and the start-up of the luminous flux of the metal halide lamp 16 is shortened by about one minute as compared with the case where there is no warm-up circuit. Can be.

The power limiting circuit 7 limits the input power of the inverter 8, that is, the output power of the power factor improving circuit 4 to a predetermined value or less, and limits the lamp power supplied to the metal halide lamp 16 to a rated value or less. . For this reason, when the lamp voltage rises at the end of the life of the lamp, it is possible to prevent the lamp from being supplied with lamp power exceeding the rated value.

Next, the operation of this embodiment will be described.
The operation of the inverter 8 and the inverter control IC 10 will be described with reference to FIGS. In FIG. 1, the power MOSFET 51 of the inverter 8 turns on when the switching control signal, that is, the gate-source voltage Vgs of the power MOSFET 51 is at a high level, and turns off when it is at 0V. Inverter 8 which is a voltage resonance type inverter circuit
Then, the waveform of the voltage (Vds) between the drain and the source during the off-time Toff of the power MOSFET 51 is the same as that of the transformer 52.
Due to the series resonance generated by the inductance of the secondary winding 52p and the capacitance between the resonance capacitor 53 and the drain-source of the power MOSFET 51, a half-wave sine wave as shown in FIG. 2 is obtained. After Vds reaches zero volts, the power MO
A zero volt switching operation is performed in which the SFET 51 is turned on.

For this reason, as shown in FIG. 2, the inverter control IC 10 outputs a switching control signal that makes the off time Toff of the power MOSFET 51 constant and makes the on time Ton variable. That is, pulse frequency control for changing the switching frequency is performed. The longer the on-time Ton of the power MOSFET 51, the greater the lamp current.
The shorter on is, the smaller the lamp current is.

Next, the configurations and operations of the inverter control circuit 9, the inverter control IC 10, and the frequency modulation circuit 11 will be described with reference to FIGS. 1, 3, and 4. FIG. As shown in FIG. 1, the inverter control IC 10 includes a reference voltage generating circuit SVG1, an error amplifier EA1, a voltage controlled oscillator VCO1, a one-shot multivibrator M
B, a driver DB, and a transistor Q. When the inverter 8 is started, the power supply V
When the inverter 8 operates, the transformer
The voltage generated in the auxiliary winding 52f of the 52 is rectified and smoothed by the diode 72 and the capacitor 73, and the power supply Vcc is supplied.

The reference voltage generation circuit SVG1 outputs a constant reference voltage Vref (5V). The reference voltage Vref is supplied to the non-inverting input terminal of the error amplifier EA1 by a resistor 59 and a resistor 60.
The bias voltage divided by is input. The inverting input terminal of the error amplifier EA1, that is, the detection terminal 10A
Is supplied with a lamp current detection signal via a gain setting resistor 56 of the error amplifier EA1. Therefore, the output voltage EA1out of the error amplifier EA1 increases as the lamp current detection signal decreases. The output of the error amplifier EA1 is connected to the input terminal A of the voltage controlled oscillator VCO1. On the other hand, a capacitor 58 is connected to the input terminal B of the voltage controlled oscillator VCO1.
A reference voltage Vref is applied via 57.

When the output of the one-shot multivibrator MB is at a low level, the capacitor 58 is charged because the transistor Q is off, and the terminal voltage of the capacitor 58 gradually increases as shown in FIG. The voltage controlled oscillator VCO1 is configured such that the voltage of the input terminal B, that is, the terminal voltage of the capacitor 58 is the voltage of the input terminal A, that is, the error amplifier E
When the output voltage EA1out of A1 is reached, a trigger signal appears at the output of the voltage controlled oscillator VCO1. Voltage controlled oscillator V
The output of CO1 is connected to the input of one-shot multivibrator MB, and one-shot multivibrator MB
Is inverted by a driver DB comprising an inverting buffer amplifier, and is output as an output terminal 10 as a switching control signal.
Output from B.

The one-shot multivibrator MB
As shown in FIG. 3, when a trigger signal is input, the output changes to a high level, and the switching control signal at the output terminal 10B of the inverter control circuit changes to a low level to change the power level.
MOSFET 51 turns off. At this time, since the transistor Q is turned on, the capacitor 58 is discharged and its terminal voltage becomes zero. This state is maintained until a certain time elapses in proportion to the product of the capacitance value of the capacitor connected to the MB and the resistance value of the resistor connected to the one-shot multivibrator.
Thereafter, as shown in FIG. 3, the output of the one-shot multivibrator MB changes to a low level, and this state is maintained until a trigger signal is input again. At this time, since the switching control signal is at the high level, the power MOSF
ET51 turns on. Therefore, the ON time Ton of the power MOSFET 51 becomes shorter as the lamp current detection signal becomes larger. The off time Toff is determined by the product of the capacitance value of the capacitor connected to the one-shot multivibrator MB and the resistance value of the resistor.

The frequency modulation circuit 11 includes an oscillator 63, a transistor 64, and resistors 65 and 66, and is connected in parallel to the resistor 62 of the inverter control circuit 9. Oscillator 63
Outputs a square wave with a frequency of about 40 Hz (period of about 25 ms) as shown in FIG.
Input to 64 base terminals. Since the transistor 64 is off while the output of the oscillator 63 is at the low level, the impedance of the frequency modulation circuit 11 is very high and does not affect the operation of the inverter control circuit 9. Therefore, the off time Toff is proportional to the product of the capacitance of the capacitor 61 and the resistance of the resistor 62. On the other hand, while the output of the oscillator 63 is at the high level, the transistor 64 is turned on, which is equivalent to connecting the resistor 65 in parallel with the resistor 62. Therefore, when compared with the period when the output of the oscillator 63 is at the low level,
This is equivalent to a decrease in the resistance value of the resistor connected to the one-shot multivibrator MB, and the OFF time Toff
Is shorter than the period when the output of the oscillator 63 is at the low level.

When the metal halide lamp 16 is lit normally, the impedance of the lamp is substantially constant, and the output voltage Vdc of the power factor improving circuit, that is, the input voltage of the inverter 8 is constant, so that the on-time Ton is substantially constant. Will be kept. Therefore, the switching frequency of the inverter 8, that is, the lamp lighting frequency of the metal halide lamp 16 is frequency-modulated by changing the off time Toff by the frequency modulation circuit 11. Its frequency shift is about
It is 15kHz.

Next, control of the lamp current will be described. In FIG. 1, the lamp current detection circuit 12 converts the lamp current into a voltage
2. Rectified and smoothed by a resistor 83, diodes 84 and 85, and a capacitor 86. This voltage is divided by the variable resistor 87, and a lamp current detection signal proportional to the lamp current at a certain ratio (hereinafter referred to as lamp current detection sensitivity) is generated at the output terminal 12A. The lamp current detection sensitivity can be set by the variable resistor 87. The lamp current detection signal is supplied to the detection terminal of the inverter control IC 10 via the resistor 56.
10A, and also to the warm-up circuit 13.

The inverter control IC 10 varies the switching control signal so that the voltage of the detection terminal 10A is maintained at a predetermined value. When the lamp current detection signal increases, detection terminal 10
The voltage of A increases and the switching control signal changes to the power MOSF
It changes so as to shorten the ON time Ton of the ET51. As a result, the lamp current decreases, and the lamp current detection signal and the voltage of the detection terminal 10A decrease. Conversely, when the lamp current detection signal decreases, the voltage at the detection terminal 10A decreases, and the switching control signal changes so as to lengthen the on-time Ton of the power MOSFET 51. Therefore, the lamp current detection signal and the voltage of the detection terminal 10A decrease. By the above control, the lamp current detection signal is kept constant, and the lamp current is kept constant if the lamp current detection sensitivity is constant.

Next, the operation of the warm-up circuit 13 will be described with reference to FIGS. In FIG.
When the power is turned on, the capacitor 93 of the warm-up circuit 13 is discharged through the diode 92.
The terminal voltage of 93 is zero, and the transistor 91 is on. Therefore, current flows from the input of the warm-up circuit 13 to the resistor 94 via the transistor 91, and the impedance of the warm-up circuit 13 is low. At this time, a current flows from the output terminal 12A of the lamp current detection circuit 12 to the warm-up circuit 13, so that the lamp current detection sensitivity is low as shown in FIG.

When a current flows through the warm-up circuit 13,
The base current of the transistor 91 charges the capacitor 93 via the resistor 95, and the terminal voltage of the capacitor 93, that is, the voltage of the base terminal of the transistor 91 gradually increases. Therefore, the current flowing through the transistor 91 gradually decreases, and the impedance of the warm-up circuit gradually increases.
As shown in FIG. 5, the lamp current detection sensitivity gradually increases. When a predetermined time (hereinafter, a warm-up period) elapses after the current starts to flow through the warm-up circuit 13, the terminal voltage of the capacitor 93 becomes equal to the voltage of the emitter terminal of the transistor 91, so that the transistor 91 is turned off. No current flows through the circuit 13. That is, the impedance of the warm-up circuit 13 becomes almost infinite. At this time, warm-up circuit from terminal 12A
Since no current flows through 13, the lamp current detection sensitivity is larger than that during the warm-up period, as shown in FIG.

The lamp current detection sensitivity is set so that the lamp current after the elapse of the warm-up period (1 minute) becomes the rated value (0.7 A). The lamp current detection sensitivity at the start of the metal halide lamp 16 is set to be 0.7 times the value after the elapse of the warm-up period. Therefore, as shown in FIG.
When the lamp starts, a lamp current of 1.4 times the rated value flows. Then, the lamp current decreases with the passage of time, and after a warm-up period of one minute, the lamp current becomes the rated value. As described above, since the lamp current larger than the rated value flows for a certain period immediately after the start of the metal halide lamp 16, the rise of the luminous flux of the metal halide lamp 16 is advanced by about one minute as compared with the case where the lamp current is always set to the rated value. be able to.

Next, the configuration and operation of a circuit for limiting the lamp power of the metal halide lamp 16 to a rated value or less will be described with reference to FIGS. The lamp power is equal to the difference between the input power of the inverter 8 and the power loss. Since the power loss of the inverter 8 is almost constant, the input power of the inverter 8, that is, the output power of the power factor improvement circuit 4, is required to limit the lamp power to the rated value or less.
What is necessary is just to limit to less than the sum of the rated lamp power and the loss power of the inverter 8.

In FIG. 1, the power factor correction circuit control IC 6 is provided with a detection terminal 6A, and the output voltage Vdc of the power factor correction circuit 4 decreases as the voltage of the detection terminal 6A increases. A voltage detection signal obtained by dividing the output voltage Vdc of the power factor correction circuit 4 by the resistors 31 and 32 is input to the detection terminal 6A. The power limiting circuit 7 is connected to the detection terminal 6A. In the power limiting circuit 7, the power factor improving circuit 4
The output current Idc is converted into a voltage by the resistor 33 and the bypass capacitor 34, is divided by the variable resistor 35, and is input to the non-inverting input terminal of the operational amplifier 37 via the resistor 36. The operational amplifier 37, the resistors 36, 38, 40 and the capacitor 39 constitute a non-inverting amplifier. The output of the operational amplifier 37 is connected to the detection terminal 6A of the power factor correction circuit control IC 6 via the resistor 41 and the diode 42.

If the constants of the elements of the power limiting circuit 7 are set so that the output voltage of the operational amplifier 37 becomes smaller than the voltage detection signal when the lamp power is equal to or less than the rated value (70 W), the diode 42 becomes non-active. Since it is in the conductive state, a voltage detection signal is input to the voltage detection terminal 6A of the power factor correction circuit control IC 6. Therefore, when the lamp power is equal to or less than the rated value, the output voltage Vdc of the power factor correction circuit 4 is controlled to a constant value (200 V) as shown in FIG. On the other hand, if the lamp power is going to exceed the rated value, the output voltage of the operational amplifier 37 will be larger than the voltage detection signal.
42 conducts, and the output of the operational amplifier 37 is input to the detection terminal 6A. At this time, as the output current Idc of the power factor correction circuit 4 increases, the output voltage of the operational amplifier 37, that is, the detection terminal 6A
, The output voltage Vdc of the power factor correction circuit 4 decreases as shown in FIG. For this reason, the output power of the power factor correction circuit 4 which is the product of the output voltage Vdc of the power factor correction circuit 4 and the output current Idc, that is, the input power of the inverter 8 is limited to a certain power or less, and therefore the lamp power is less than the rated value. Is limited to

Next, a second embodiment of the present invention will be described. 7, the same parts as those in FIG. 1 showing the first embodiment are denoted by the same reference numerals, and the detailed configuration and illustration of those parts will be omitted. Inverter 21
Is a half-bridge inverter circuit composed of two power switch elements (power MOSFETs 101 and 102). The inverter 21 is connected to an inverter control circuit 22 including an inverter control IC 23, and the frequency modulation circuit 11 is connected to the inverter control circuit 22.
In the inverter 21 shown in FIG.
And a power MOSFET 102 are connected in series to the output of the power factor correction circuit 4. An inductor 14 and a capacitor 15 are connected in series between a connection point between the source terminal of the power MOSFET 101 and the drain terminal of the power MOSFET 102, that is, between the output terminal 21A of the inverter 21 and the source terminal of the power MOSFET 102. Also, in parallel with the capacitor 15, the capacitor 17, the metal halide lamp 16 (for example, rated power 70
W) and the lamp current detection circuit 12 are connected in series.

When the metal halide lamp 16 is started, the switching frequency of the inverter 21 is changed to near the resonance frequency of the series resonance circuit composed of the inductor 14 and the capacitor 15, so that the lamp 15 has a lamp starting voltage having a peak voltage of about 2 kV. Occurs, and the metal halide lamp 16 starts. After starting the lamp, the inverter 21 is operated at a switching frequency of about 300 kHz,
The high frequency current is supplied to the lamp to perform high frequency lighting. Note that the inductor 14 is for sharing the difference between the voltage at the output terminal 21A of the inverter 21 and the discharge sustaining voltage (about 100 V) of the metal halide lamp 16 during steady lighting. Further, the capacitor 17 is for cutting the DC component of the lamp current.

The gate terminals of the power MOSFETs 101 and 102 are connected to the first output terminal 23 of the inverter control IC 23, respectively.
B and the second output terminal 23C, and the power MOSFET 101 and the power MOSFET 102 are driven by the switching control signal output from these output terminals,
The inverter 21 operates. The first output terminal 23B and the second output terminal 23C output signals whose phases are different by 180 °.
The power MOSFET 101 and the power MOSFET 102 are turned on when the switching control signal, that is, the gate-source voltage of the power MOSFET is at a high level, and turned off when the gate-source voltage is 0V. The power MOSFET 101
Excessive current flows through the two power MOSFETs when there is a period in which both are turned on. In order to prevent this phenomenon, a period (hereinafter, referred to as a dead time) Td during which the power MOSFETs 101 and 102 are simultaneously turned off is provided.

Next, the operation of the inverter 21 will be described with reference to FIGS. FIG. 8 shows waveforms of gate-source voltages Vgs1 and Vgs2, drain-source voltages Vds1 and Vds2, drain currents Id1 and Id2, and lamp currents of the power MOSFETs 101 and 102 when the metal halide lamp 16 is turned on. is there. FIG. 9 shows a part of FIG. 7, and the current path in a part of the period shown in FIG. 8 is indicated by an arrow. When the metal halide lamp 16 is turned on, its impedance is
Since the impedance of the capacitor 15 is sufficiently smaller than the impedance of the capacitor 15 and the effect of the capacitor 15 can be almost ignored, FIG.
Is omitted.

In the period T1 shown in FIG.
The SFET 101 is on, the power MOSFET 102 is off, and the current flows in the direction of the arrow shown in FIG. When the gate-source voltage Vgs1 of the power MOSFET 101 becomes 0 V at the dead time Td shown in FIG.
101 turns off. At this time, since the direction of the current flowing through the inductor 14 does not change immediately, the body diode of the power MOSFET 102 conducts as shown in FIG. 9B, and the current flows through the path indicated by the arrow. At this time, as shown in FIG. 8, the voltage Vds2 between the drain and the source of the power MOSFET 102 becomes 0.7 V, and thereafter Vgs2 becomes high level to turn on the power MOSFET 102, so that a soft switching operation with a small switching loss is performed. .

When the power MOSFET 102 is turned on,
In the period T2 shown in FIG. 8, current flows in the direction of the arrow shown in FIG. 9C, but since the magnitude of the current gradually decreases, the power MOSFET 102 is turned on during the ON period of the power MOSFET 102.
The terminal voltage of the body diode 102 becomes 0.7 V or less, and the body diode becomes non-conductive. As a result, the current flows through the channel of the power MOSFET 102, so that the current flowing direction is reversed. In the period T3 shown in FIG. 8, the current flows in the direction of the arrow shown in FIG. 9D. After that, when the power MOSFET 102 is turned off and the power MOSFET 101 is turned on, the same operation as described above is performed.

For controlling the switching operation, the dead time Td is fixed, and the power MOSFETs 101 and 102 are controlled.
To make the ON time Ton variable, that is, pulse frequency control to make the switching frequency variable.
As shown in FIGS. 10A and 10B, the on-time To
The longer the n is, the larger the lamp current is, while the shorter the on-time Ton is, the smaller the lamp current is. As in the first embodiment, the lamp current detection circuit 12 detects the lamp current and outputs a lamp current detection signal proportional to the magnitude of the lamp current. The lamp current detection signal is input to the detection terminal 23A of the inverter control IC 23, and the inverter control IC 23 controls the operation of the inverter 21 by varying the on-time Ton so that the voltage of the detection terminal 23A becomes constant. The current is controlled.

Next, the configurations and operations of the inverter control circuit 22 and the inverter control IC 23 will be described with reference to FIGS.
1 and FIG. Inverter control I
C23 is a reference voltage generation circuit SVG2, as shown in FIG.
Error amplifier EA2, voltage controlled oscillator VCO2, T-flip-flop FF, two NOR gates NOR1, N
OR2, and drivers DB1 and DB2. The reference voltage generation circuit SVG2 outputs a constant reference voltage Vre
f (5V) is output. A bias voltage obtained by dividing the reference voltage Vref by resistors 111 and 112 is input to the non-inverting input terminal of the error amplifier EA2. A lamp current detection signal is input to the inverting input terminal of the error amplifier EA2, that is, the detection terminal 23A via the gain setting resistor 113 of the error amplifier EA2. Therefore, the output voltage EA2out of the error amplifier EA2 increases as the lamp current detection signal decreases. The output terminal of the error amplifier EA2 is connected to the input terminal a of the voltage controlled oscillator VCO2.

FIG. 11 shows a part of the inverter control circuit 22 including the internal circuit configuration of the voltage controlled oscillator VCO2. An input terminal a of the voltage controlled oscillator VCO2 is connected to a reference voltage generating circuit SVG2 via a resistor 115, and a frequency modulation circuit 11 is connected to the input terminal a. Isc is a current source controlled by a current Irc flowing through the resistor 115, and flows a current obtained by multiplying the current Irc by a constant value. Isd is a current source controlled by a current Ird flowing through a resistor 116 connected to the DC constant voltage source Vrd, and flows a current obtained by multiplying the current Ird by a constant value. COMP is a comparator having hysteresis characteristics, and operates by detecting the terminal voltage of the capacitor 117 connected to the non-inverting input terminal. The output terminal of the comparator COMP is connected to the output terminal b of the voltage controlled oscillator VCO2. Further, the switch SW1 is output by the output of the comparator COMP.
And a circuit configured to control the operation of SW2, and when the output of the comparator COMP is at a low level,
The switch SW1 turns off and the switch SW2 turns on.
Conversely, when the output of the comparator COMP is at a high level, the switch SW1 turns off and the switch SW2 turns on.

The operation of the voltage controlled oscillator VCO2 will be described with reference to FIGS. First, the comparator CO
During the period when the output of MP, that is, the output of the voltage controlled oscillator VCO2 is at a low level, as shown in FIG.
Since the switch 1 is turned on and the switch SW2 is turned off, the capacitor 117 is charged by the current source Isc, and the terminal voltage gradually increases as shown in FIG. When the terminal voltage of the capacitor 117 reaches the first threshold voltage Vth1 of the comparator COMP, the output of the comparator COMP, that is, the output of the voltage controlled oscillator VCO2 changes to a high level as shown in FIG. Turns off and the switch SW2 turns on. Therefore, the current source I
The capacitor 117 is discharged by sd, and its terminal voltage gradually decreases as shown in FIG. And the capacitor
When the terminal voltage of the comparator 117 reaches the second threshold voltage Vth2 of the comparator COMP, the output of the comparator COMP,
That is, the output of the voltage controlled oscillator VCO2 changes to a low level as shown in FIG.

Referring to FIG. 7 and FIG. 12, the output terminal b of the voltage controlled oscillator VCO2 is connected to the input terminal T of the T-flip-flop FF, and as shown in FIG. When the output of the oscillator VCO2 changes from low level to high level, T
The outputs Q and Q of the flip-flop FF are inverted;
One input terminal of each of the two NOR gates NOR1 and NOR2 is connected to the output terminal b of the voltage controlled oscillator VCO2. The other terminals of the NOR gates NOR1 and NOR2 have a T-flip-flop F
The outputs Q and Q of F are connected respectively. Accordingly, as shown in FIG. 12, the output of the NOR gate NOR1 is at the high level when the output of the voltage controlled oscillator VCO2 and the output Q of the T-flip-flop FF are both at the low level, and is at the low level during the other periods. . Similarly,
As shown in FIG. 12, the output of the NOR gate NOR2 is the output of the voltage controlled oscillator VCO2 and the T-flip-flop F
The output Q of F is at a high level while both are at a low level, and is at a low level during other periods. Outputs of the NOR gates NOR1 and NOR2 are output as switching control signals as shown in FIG. 12 from output terminals 23B and 23C via drivers DB1 and DB2, each of which is a non-inverting buffer amplifier, and drive the power MOSFETs 101 and 102.

Therefore, for example, when the lamp current detection signal increases, the voltage at the detection terminal 23A increases, the output voltage EA2out of the error amplifier EA2, ie, the voltage at the input terminal a of the voltage controlled oscillator VCO2 decreases, and the current flowing through the resistor 115 decreases. Since Irc increases, the capacitor 11 is removed from the current source Isc.
The current flowing to 7 increases. Therefore, the capacitor 11
7, the rate of rise of the terminal voltage increases, and the on-time Ton shown in FIG. 12 decreases. On the other hand, since the current Ird flowing through the resistor 116 is always constant,
The current flowing from the capacitor 117 to the current source Isd is also constant. For this reason, since the discharge speed of the capacitor 117 is always constant, the dead time Td is always constant.

Regarding the frequency modulation of the lamp lighting frequency,
This will be described with reference to FIGS. Frequency modulation circuit
The configuration and operation of the eleventh embodiment are the same as those of the first embodiment. FIG.
In FIG. 1, while the output of the oscillator 63 is at the low level, the transistor 64 is off, so that the impedance of the frequency modulation circuit 11 is very high and does not affect the operation of the inverter control circuit 22. On the other hand, while the output of the oscillator 63 is at a high level, the transistor 64 is turned on.
1, a current flows from the reference voltage generating circuit SVG2 to the transistor 64 and the resistor 65 of the frequency modulation circuit 11 via the resistor 115. Therefore, compared to the period when the output of the oscillator 63 is at the low level, the current Irc flowing through the resistor 115 increases, the current flowing from the current source Isc to the capacitor 117 increases, and the charging speed of the capacitor 117 increases.
Is shorter, but the dead time Td is always constant, so that the ON time T
When on changes, the switching frequency of the inverter 21, that is, the lamp lighting frequency of the metal halide lamp 16 is frequency-modulated. Therefore, similarly to the first embodiment, the metal halide lamp 16 can be stably turned on at a high frequency while avoiding the acoustic resonance phenomenon.

[0045]

According to the present invention, by modulating the lamp operating frequency, the occurrence of an acoustic resonance phenomenon during high-frequency operation of the metal halide lamp can be avoided, and the switching frequency of the inverter can be relatively reduced. Therefore, the efficiency of the inverter circuit can be increased, and the generated high-frequency noise can be reduced. Further, since the lamp current larger than the rated value flows for a certain period from the start of the metal halide lamp, the time required to reach the rated light output is short. Further, since the lamp current can be controlled to be constant and the power supplied to the metal halide lamp can be limited after a certain period of time at the time of starting, the fluctuation of the light output is small until the life of the metal halide lamp reaches its end.
Since the power factor improving circuit is provided, harmonic components of the power current can be suppressed, and a high power factor can be obtained.

[Brief description of the drawings]

FIG. 1 is a first embodiment of a high-intensity discharge lamp lighting circuit according to the present invention.

FIG. 2 is a diagram showing an operation state of a power MOSFET of an inverter when a lamp current is large and small in a first embodiment.

FIG. 3 is a diagram illustrating an operation state of the inverter control circuit according to the first embodiment.

FIG. 4 is a diagram illustrating a change in lamp current due to an operation of the frequency modulation circuit in the first embodiment.

FIG. 5 is a diagram showing changes in lamp current detection sensitivity and lamp current magnitude due to the operation of the warm-up circuit in the first embodiment.

FIG. 6 is a diagram illustrating a relationship between output current and voltage and output power of the power factor correction circuit according to the first embodiment.

FIG. 7 is a second embodiment of the high-intensity discharge lamp lighting circuit according to the present invention.

FIG. 8 is a diagram showing a relationship between an operation state of an inverter and a lamp current in a second embodiment.

FIG. 9 shows the power MOSF of the inverter according to the second embodiment.
FIG. 4 is a diagram illustrating an operation of the ET for each operation period.

FIG. 10 is a diagram showing an operation state of the power MOSFET of the inverter when the lamp current is large and small in the second embodiment.

FIG. 11 is a diagram illustrating an operation state inside the inverter control circuit according to the second embodiment.

FIG. 12 is an operation relation diagram of an inverter control circuit and a power MOSFET in a second embodiment.

FIG. 13 is a diagram showing a change in lamp current due to the operation of the frequency modulation circuit in the second embodiment.

FIG. 14 shows a conventional high-intensity discharge lamp lighting circuit.

FIG. 15 is a diagram illustrating a relationship between an input voltage and an input current of the power factor correction circuit.

[Explanation of symbols]

 1, 2... AC input terminal 3... Input rectifier 4... Power factor improvement circuit 6... Power factor improvement control circuit 7. ····· Power limiting circuit 8 ································································································ ... Frequency modulation circuit 12 Lamp current detection circuit 13 Warm-up circuit 21 Two-piece inverter circuit 22 Two pieces Type inverter control circuit 23 ・ ・ ・ ・ ・ ・ Two-stone type inverter control circuit IC

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masashi Hozuki 173-1 Asana-cho, Iwata-gun, Shizuoka Prefecture Inside Minebea Development Technology Center (72) Inventor Manabu Kodama Asana, Asaba-cho, Iwata-gun, Shizuoka Prefecture 1743-1 Inside Minebea Development Technology Center

Claims (4)

[Claims] A high frequency current is supplied to a rectifying / smoothing means of a commercial AC power supply, a power factor improving means connected to an output of the rectifying / smoothing means for outputting DC power, and a metal halide lamp connected to an output of the power factor improving means. An inverter for supplying and lighting, a lamp current detection means for outputting a lamp current detection signal proportional to a magnitude of a lamp current flowing through the metal halide lamp, and an inverter for maintaining the lamp current detection signal at a predetermined value. A high-intensity discharge lamp lighting device including an inverter control means for controlling an intermittent interval of the power switch element, wherein a time constant for determining an ON interval of the power switch element of the inverter connected to the inverter control means is determined at a predetermined cycle. Equipped with frequency modulation means for changing and warm-up means for surely starting the metal halide lamp to improve power factor A high-intensity discharge lamp lighting device comprising a power limiting means for limiting the output power of the means to a predetermined value or less. 2. The frequency modulating means comprises a low-frequency square wave oscillator, and inputs a square wave output to a control circuit of an inverter to frequency-modulate an intermittent operation frequency of the inverter. Item 2. A high-intensity discharge lamp lighting device according to Item 1. 3. The warm-up means attenuates the sensitivity of the lamp current detecting means for a certain period of time at the time of initial startup of the discharge lamp lighting device and before starting of the metal halide lamp, so that the inverter output becomes larger than a steady value. 2. The high-intensity discharge lamp lighting device according to claim 1, wherein the lighting of the metal halide lamp is ensured at high speed. 4. The power limiting unit detects an output current and an output voltage of the power factor improving unit, inputs a control signal to the power factor improving unit, and controls an output power of the power factor improving unit to a set value or less. The high-intensity discharge lamp lighting device according to claim 1, wherein