JPH10164860A - Power supply, discharge lamp lighting unit and illuminator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting unit in which a high current flow due to simultaneous turn on of a pair of switching units is prevented. SOLUTION: When a current detected by a current detection circuit 14 is regarded as an overcurrent by a comparator 19, a switching control section 20 does not vary the frequency but enlarges the width of a rectangular pulse. Discharging time of a first capacitor C2 is prolonged by increasing the on duty of a first switching unit Q1 and the voltage to be induced in an insulating transformer Tr1 is lowered thus suppressing the overcurrent. DC voltage level is lowered as the on time at a driving section 17 is prolonged and when the voltage begins to oscillate due to resonance of a control inductor L2 and a control capacitor C5, oscillation is braked through a resistor R1. Consequently, the voltage to be induced in a control inductor L3 is prevented from increasing unnecessarily and both first and second switching units Q1, Q2 are turned on thus preventing short circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device, a discharge lamp lighting device, and a lighting device in which switching devices connected in series are prevented from being simultaneously turned on.

[0002]

2. Description of the Related Art Hitherto, as a lighting apparatus of this kind, for example, a structure described in Japanese Patent Application Laid-Open No. 7-99091 has been known.

In Japanese Patent Application Laid-Open No. Hei 7-99091, a rectifier is connected to a commercial AC power supply, a smoothing capacitor is connected between output terminals of the rectifier, and a pair of switching devices are connected in parallel with the capacitor. A series circuit of the device is connected, and a fluorescent lamp is connected in parallel to the switching device located on the low voltage side. In addition, a detection winding of a current transformer is connected in series with the fluorescent lamp, and a control winding of the current winding controls each switching device. A capacitor is connected.

The switching device is alternately switched at a high frequency to supply a high-frequency alternating current to the fluorescent lamp, and the high-frequency alternating current is detected by a detection winding, and each control winding is applied to each control winding according to the detected high frequency. The switching device is turned on and off alternately.

[0005]

However, for example, an overcurrent detecting means is connected to the configuration described in Japanese Patent Application Laid-Open No. 7-99091, and a control means is connected to one of the switching devices. If an overcurrent is detected and the on-duty of one switching device is suddenly changed to reduce the output,
Since a capacitor is connected to the control winding of this switching device, a large resonance occurs, and the control of the other switching device also causes a resonance. Both switching devices are turned on at the same time and short-circuited, and a large current may flow. I have a problem.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a power supply device, a discharge lamp lighting device, and a lighting device in which a pair of switching devices are simultaneously turned on to prevent a large current from flowing. And

[0007]

According to a first aspect of the present invention, there is provided a power supply device comprising: a pair of switching devices provided in series between output terminals of a DC power supply; and a switching device connected to each of the pair of switching devices. A pair of control inductors magnetically connected to alternately turn on and off; a pair of control capacitors connected to these control inductors and resonating with each other; an output circuit that outputs based on the operation of the switching device; And a switching control means for controlling one of the switching devices and reducing the output of the output circuit when an abnormality is detected by the abnormality detection means; and a switching device controlled by the switching control means. And a resistor connected to the control inductor and the control capacitor. It is. The switching control means controls one switching device, and the other switching device is turned on and off differently from the one switching device by a control inductor. And converts the DC voltage to AC to generate an AC voltage in the output circuit. When an abnormality is detected by the abnormality detection means, the output of the output circuit is reduced by the switching control means. Since it is connected, a DC component is added, and the resonance of the control inductor and the control capacitor is damped, so that the vibration does not increase and both switching devices are not turned on at the same time.

According to a second aspect of the present invention, there is provided a power supply device for rectifying an output voltage of an AC power supply and outputting a non-smoothed DC voltage; A pair of switching devices that alternately turn on and off at a frequency higher than the frequency; a pair of magnetically connected control inductors that are respectively connected to the pair of switching devices and that turn on and off the switching devices alternately; A pair of control capacitors connected to the control inductor and resonating with each other; a series circuit of a first capacitor and an inductor that smoothes the output frequency of the rectifier provided between both terminals of one switching device; ON of a pair of switching devices,
A second capacitor that resonates in cooperation with the inductor when turned off; an output circuit that turns on the discharge lamp based on the resonance of the inductor and the second capacitor; and an abnormality detection unit that detects an abnormality; Switching control means for controlling the switching device and reducing the output of the output circuit when an abnormality is detected by the abnormality detection means; connected to a control inductor and a control capacitor of the switching device controlled by the switching control means. And a resistor. Then, the first capacitor smoothes the unsmoothed DC voltage of the rectifier, and the second capacitor and the inductor generate a resonance voltage according to ON / OFF of the pair of switching devices.
This resonance voltage raises the valley of the unsmoothed DC voltage and smoothes the envelope of the high-frequency output voltage. The resonance voltage causes the voltage across the first capacitor and the second capacitor, or the voltage across the first capacitor, to be lower than the non-smoothing DC voltage of the rectifier during one cycle of switching of the pair of switching devices. Therefore, during one cycle of switching of the pair of switching devices, a charging current flows from the AC power supply to the first capacitor.
An input current is ensured even during a period in which the peak value of the rectified non-smoothed DC voltage is low, and an input power factor is increased, and a distortion of the input current is reduced to reduce a harmonic of the input current. Further, when an abnormality is detected by the abnormality detection unit, the output of the output circuit is reduced by the switching control unit. At this time, even if resonance occurs in the control inductor and the control capacitor of the switching device that is not directly controlled by the switching control unit, Since the resistor is connected, a DC component is added, and the resonance of the control inductor and the control capacitor is damped, so that the vibration does not increase and both switching devices are not turned on at the same time.

According to a third aspect of the present invention, there is provided a power supply device comprising: a pair of switching devices provided in series between output terminals of a DC power supply; and a switching device connected to each of the pair of switching devices and alternately turning on and off the switching devices. A pair of control inductors that are magnetically connected to each other; a pair of control capacitors that are connected to these control inductors and resonate with each other; an output circuit that outputs based on the operation of the switching device; And switching control means for shortening the output time of the drive signal for turning on the switching device after the start of the operation. The switching control means controls one switching device, and the other switching device is turned on and off differently from the one switching device by a control inductor. And converts the DC voltage to AC to generate an AC voltage in the output circuit. Then, after the operation is started, the output time of the drive signal for turning on the switching devices is shortened, so that both the switching devices are not turned on at the same time.

According to a fourth aspect of the present invention, there is provided a power supply device which rectifies an output voltage of an AC power supply and outputs a non-smoothed DC voltage; A pair of switching devices that alternately turn on and off at a frequency higher than the frequency; a pair of magnetically connected control inductors that are respectively connected to the pair of switching devices and that turn on and off the switching devices alternately; A pair of control capacitors connected to the control inductor and resonating with each other; a series circuit of a first capacitor and an inductor that smoothes the output frequency of the rectifier provided between both terminals of one switching device; ON of a pair of switching devices,
A second capacitor that resonates in cooperation with the inductor when turned off; an output circuit that turns on the discharge lamp based on resonance of the inductor and the second capacitor; and controls one of the switching devices and starts operation Later, switching control means for shortening the output time of the drive signal for turning on the switching device is provided. Then, the first capacitor smoothes the unsmoothed DC voltage of the rectifier, and the second capacitor and the inductor generate a resonance voltage in accordance with ON / OFF of the pair of switching devices. The valley of the voltage is raised, and the envelope of the high-frequency output voltage is smoothed.
The resonance voltage causes the voltage across the first capacitor and the second capacitor, or the voltage across the first capacitor, to be lower than the non-smoothing DC voltage of the rectifier during one cycle of switching of the pair of switching devices. Therefore, during one cycle of switching of the pair of switching devices, a charging current flows from the AC power supply to the first capacitor,
This charging current secures the input current even during the period in which the peak value of the rectified non-smooth DC voltage is low, increases the input power factor, and reduces the input current to reduce harmonics of the input current. Then, after the operation is started, the output time of the drive signal for turning on the switching devices is shortened, so that both the switching devices are not turned on at the same time.

According to a fifth aspect of the present invention, there is provided a power supply device comprising: a pair of switching devices provided in series between output terminals of a DC power source; and a switching device connected to each of the pair of switching devices to turn on and off the switching devices alternately. A pair of control inductors that are magnetically connected to each other; a pair of control capacitors that are connected to these control inductors and resonate with each other; an output circuit that outputs based on the operation of the switching device; And switching control means for delaying the rise of the switching device after the start of operation. The switching control means controls one switching device, and the other switching device is turned on and off differently from the one switching device by a control inductor. And converts the DC voltage to AC to generate an AC voltage in the output circuit. And
After the operation is started, both switching devices are not turned on at the same time by delaying the on rise of the switching devices.

According to a sixth aspect of the present invention, there is provided a power supply device that rectifies an output voltage of an AC power supply and outputs a non-smoothed DC voltage; A pair of switching devices that alternately turn on and off at a frequency higher than the frequency; a pair of magnetically connected control inductors that are respectively connected to the pair of switching devices and that turn on and off the switching devices alternately; A pair of control capacitors connected to the control inductor and resonating with each other; a series circuit of a first capacitor and an inductor that smoothes the output frequency of the rectifier provided between both terminals of one switching device; ON of a pair of switching devices,
A second capacitor that resonates in cooperation with the inductor when turned off; an output circuit that turns on the discharge lamp based on resonance of the inductor and the second capacitor; and controls one of the switching devices and starts operation It is provided with switching control means for delaying the on-rise of the switching device. Then, the first capacitor smoothes the unsmoothed DC voltage of the rectifier, and the second capacitor and the inductor generate a resonance voltage in accordance with ON / OFF of the pair of switching devices. The valley of the voltage is raised, and the envelope of the high-frequency output voltage is smoothed. The resonance voltage causes the voltage across the first capacitor and the second capacitor, or the voltage across the first capacitor, to be lower than the non-smoothing DC voltage of the rectifier during one cycle of switching of the pair of switching devices. Therefore, during one cycle of switching of the pair of switching devices, a charging current flows from the AC power supply to the first capacitor, and the charging current causes the input current to flow even during a period in which the peak value of the rectified non-smoothed DC voltage is low. While securing the input power factor, the input current is reduced to reduce the harmonics of the input current. Then, after the operation is started, both switching devices are not turned on at the same time by delaying the rising of the switching devices.

According to a seventh aspect of the present invention, there is provided a power supply device comprising: a pair of switching devices provided in series between output terminals of a DC power supply; and a switching device connected to each of the pair of switching devices to alternately turn on and off the switching devices. A pair of control inductors that are magnetically connected to each other; a pair of control capacitors that are connected to these control inductors and resonate with each other; an output circuit that outputs based on the operation of the switching device; Switching control means for controlling; detecting the polarity of a control inductor for controlling the other switching apparatus which is not one of the switching apparatuses controlled by the switching control means; Forcibly turn off the other switching device It is obtained by and a forced OFF means. Then, one switching device is controlled by the switching control means, and the other switching device is turned on and off differently from the one switching device by the control inductor, so that a pair of switching devices are turned on and off.
When turned off, the DC voltage of the DC power supply is converted into AC and an AC voltage is generated in the output circuit. Then, the polarity of the control inductor that controls the other switching device that is not one of the switching devices controlled by the switching control unit is detected, and when the polarity is not the one that turns on the other switching device, the other switching device is forcibly turned off by the forced off unit. The switching devices are forcibly turned off, and both switching devices are not turned on at the same time.

According to another aspect of the present invention, there is provided a power supply device that rectifies an output voltage of an AC power supply and outputs a non-smoothed DC voltage; A pair of switching devices that alternately turn on and off at a frequency higher than the frequency; a pair of magnetically connected control inductors that are respectively connected to the pair of switching devices and that turn on and off the switching devices alternately; A pair of control capacitors connected to the control inductor and resonating with each other; a series circuit of a first capacitor and an inductor that smoothes the output frequency of the rectifier provided between both terminals of one switching device; ON of a pair of switching devices,
A second capacitor that resonates in cooperation with the inductor when turned off; an output circuit that turns on the discharge lamp based on resonance of the inductor and the second capacitor; switching control means that controls one of the switching devices Detecting the polarity of a control inductor that controls the other switching device that is not one of the switching devices controlled by the switching control means, and switches the other switching device when the polarity is not the one that turns on the other switching device. Forcibly turning off the power. Then, the first capacitor smoothes the unsmoothed DC voltage of the rectifier, and the second capacitor and the inductor generate a resonance voltage in accordance with ON / OFF of the pair of switching devices. The valley of the voltage is raised, and the envelope of the high-frequency output voltage is smoothed. Depending on the resonance voltage, the voltage between the first capacitor and the second capacitor, or
Is made lower than the unsmoothed DC voltage of the rectifier during one cycle of switching of the pair of switching devices. Therefore, during one cycle of switching of the pair of switching devices, a charging current flows from the AC power supply to the first capacitor, and the charging current causes the input current to flow even during a period in which the peak value of the rectified non-smoothed DC voltage is low. While securing the input power factor, the input current is reduced to reduce the harmonics of the input current. Then, the polarity of the control inductor that controls the other switching device that is not one of the switching devices controlled by the switching control unit is detected, and when the polarity is not the one that turns on the other switching device, the other switching device is forcibly turned off by the forced off unit. The switching devices are forcibly turned off, and both switching devices are not turned on at the same time.

According to a ninth aspect of the present invention, there is provided a discharge lamp lighting device including the power supply device according to any one of the first to eighth aspects, wherein the discharge lamp is connected to the output circuit. Then, the respective functions are achieved.

A lighting device according to a tenth aspect of the present invention includes a discharge lamp lighting device according to the ninth aspect of the present invention; and a fixture body equipped with the discharge lamp lighting device and mounted with a discharge lamp.
Then, the respective functions are achieved.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a lighting device according to an embodiment of the present invention.

FIG. 1 is a circuit diagram showing a discharge lamp lighting device according to an embodiment, and FIG. 2 is a perspective view showing the appearance of the lighting device.

As shown in FIG. 2, reference numeral 1 denotes an instrument main body. The instrument main body 1 is a so-called trough type having a reflecting plate 2 formed on a surface thereof and attached to a ceiling surface (not shown) or the like. Further, a pair of lamp sockets 3 is disposed in the longitudinal direction at both ends of the reflecting plate 2 of the appliance body 1, respectively. A fluorescent lamp FL as a discharge lamp is mounted on these lamp sockets 3, and FIG. A discharge lamp lighting device 11 which is also a power supply device shown in FIG.

As shown in FIG. 1, in the discharge lamp lighting device 11, a filter circuit 12 having a choke coil L1 and a capacitor C1 is connected to a commercial AC power supply e. The input terminal of the configured full-wave rectifier 13 of the diode bridge is connected.

Between the output terminals of the full-wave rectifier 13, a first switching device Q1 as one switching device and a second switching device Q2 as the other switching device are connected in series. Each of the first switching device Q1 and the second switching device Q2 has a field-effect transistor using a parasitic diode for reverse current flow.

Further, between the output terminals of the full-wave rectifier 13, a first capacitor C2 for charging, which has a relatively large capacity, corresponds to the first switching device Q1 and the second switching device Q2, respectively. And the first capacitor C2
A second capacitor C3 for resonance having a much smaller capacity is connected in series. Further, a current detection circuit 14 as current detection means for detecting an overcurrent is connected in series with the first capacitor C2. As the current detection circuit 14, a resistor or a transformer is used to convert a current value to a voltage value.

The connection point between the first switching device Q1 and the second switching device Q2 and the connection point between the first capacitor C2 and the second capacitor C3 are shared with the second capacitor C3. A primary winding Tr1a of a leakage type insulation transformer Tr1 as an inductor that operates and oscillates is connected, and a secondary winding Tr1b as an output circuit of the insulation transformer Tr1 is connected to each filament of the fluorescent lamp FL.
One end of FLa, FLb is connected, and filaments FLa, FLb
Is connected to a starting capacitor C4.

The first switching device Q1 and the second switching device Q2 are driven by a first switch driving circuit 15 and a second switch driving circuit 16, respectively. The first switch drive circuit 15 has a drive unit 17 for driving the first switching device Q1, and the drive unit 17
17 is connected to a series circuit of a control inductor L2, a control capacitor C5, and a resistor R1, and a second switch driving circuit
16 has a drive unit 18 for driving the second switching device Q2, the drive unit 18 having a control inductor L3 and a control capacitor magnetically connected to the control inductor L2.
A series circuit of C6 is connected, and a diode D1 is connected in parallel to the series circuit.

Further, the current detecting circuit 14 compares the current detected by the current detecting circuit 14 with a reference current value, and when the current value is higher than the reference current value, a comparator 19 as abnormality detecting means for judging an overcurrent. The comparator 19 is connected to a switching control unit 20 as a switching control unit that sets an on-duty and the like of the driving unit 17 according to the output of the comparator 19, has an amplifier, and outputs a rectangular wave pulse signal. ing.

Next, the operation of the above embodiment will be described.

First, the voltage of the commercial AC power supply e is input to the full-wave rectifier 13 via the filter circuit 12, and the full-wave rectifier 13 performs full-wave rectification. On the other hand, the first switching device
Q1 and the second switching device Q2 are oscillated at a frequency higher than the power supply frequency of the commercial AC power supply e, several kHz or more, preferably 20 kHz or more which is higher than the audible frequency, and a high-frequency AC voltage is applied to the secondary winding Tr1b of the insulating transformer Tr1. And the fluorescent lamp FL is turned on. That is, the switching control unit 20 outputs a pulse, and the driving unit 17 turns on the first switching device Q1. When the first switching device Q1 is turned on in this way, the drive unit 18 turns off the second switching device Q2 by the control inductor L2 and the control inductor L3. Conversely, when the first switching device Q1 is turned on by the drive unit 17, the control inductor L2
The drive unit 18 turns on the second switching Q2 by the control inductor L3. As described above, when the first switching device Q1 is on, the second switching device Q2 is turned off, and when the first switching device Q1 is off, the second switching device Q2 is turned on, and the first switching device Q2 is turned on. Of the switching device Q1 and the second switching device Q2 are not turned on at the same time to prevent a large current from flowing due to a short circuit. When a voltage having a polarity that turns off the second switching device Q2 is induced in the control inductor L3,
The current is returned by the diode D1 to charge the control capacitor C6.

Then, a resonance voltage is generated by the second capacitor C3 and the insulating transformer Tr1, and the resonance voltage causes the current from the commercial AC power supply e to be supplied from the commercial AC power source e even when the peak value of the voltage rectified by the full-wave rectifier 13 is low. To increase the power factor and reduce distortion.

More specifically, first, in a state where the first capacitor C2 is charged, the first switching device
When Q1 is closed, the first capacitor C2, the isolation transformer Tr
1 forms a closed circuit of the primary winding Tr1a, the first switching device Q1 and the first capacitor C2,
C2 discharges.

Next, since the first switching device Q1 is turned off and the second switching device Q2 can conduct reverse current, the primary winding Tr1a of the insulating transformer Tr1, the second switching device Q2, the second switching device Q2, Capacitor C3 and isolation transformer Tr
1 is closed, and the isolation transformer Tr1
In addition, a series resonance occurs in the second capacitor C3, and a resonance current flows. Then, a resonance voltage appears in the second capacitor C3 and the primary winding Tr1a of the insulating transformer Tr1, and the resonance voltage is determined by the magnitude of the current that is cut off when the first switching device Q1 is turned off, It also appears at the voltage of the full-wave rectifier 13 equal to the sum of the voltage of the second capacitor C3 and the voltage of the first capacitor C2.

When the second switching device Q2 is turned on, the second capacitor C3 and the second switching device Q2 are turned on.
2. A closed circuit is formed between the primary winding Tr1a of the insulating transformer Tr1 and the second capacitor C3, the polarity of the resonance current is inverted, and a resonance current in the opposite direction flows, thereby generating a resonance voltage. In any case, the resonance voltage increases the pulsating voltage.

The primary winding Tr1a of the insulating transformer Tr1
When the resonance voltage due to the second capacitor C3 decreases, the voltage across the second capacitor C3 and the first capacitor C2 also decreases, so that the primary voltage of the full-wave rectifier 13, the second switching device Q2, and the isolation transformer Tr1 is reduced. Winding Tr1a, 1st
And the full-wave rectifier 13 is closed, and the first capacitor C2 is charged.

Further, since the second switching device Q2 is turned off and the reverse current of the first switching device Q1 can flow, the primary winding Tr1a of the isolation transformer Tr1, the first capacitor C2, the first switching device Device Q1 and isolation transformer Tr
1 is closed, and the isolation transformer Tr1
A current flows through the primary winding Tr1a.

Then, the second switching device Q2 is turned on again.

Of these operations, the full-wave rectifier
In the portion where the peak value of the voltage 13 is high, the on-period of the second switching device Q2 is relatively short, and in the portion where the peak value is low, the on-period of the second switching device Q2 is relatively long. The change in the ON period may be continuous or stepwise with respect to the peak value.

As described above, when the on-period of the second switching device Q2 is relatively lengthened in the portion where the peak value is low, the amplitude of the resonance voltage and the peak value are increased.
This is larger than when the on-period of Q2 is relatively short. That is, in a portion where the peak value of the unsmoothed DC voltage is low, the voltage charged in the second capacitor C3 decreases according to the peak value, and the initial current flowing into the second capacitor C3 increases. Therefore, in the period where the peak value of the non-smoothed DC voltage is low, the voltage can be boosted more than in the portion where the peak value is high.

In the period where the peak value is low, the current flowing through the first switching device Q1 is cut off at a relatively small stage, so that the initial resonance current value after the first switching device Q1 is turned off is reduced. Although the resonance voltage is increased due to the charging voltage of the second capacitor C3, the peak voltage of the non-smooth DC voltage is reduced without excessively increasing the voltage at the valleys, although the resonance voltage is increased. During the period,
The voltage can be boosted as desired, and the output voltage can be smoothed.

Further, since the current from the full-wave rectifier 13 flows over the entire period of the unsmoothed DC voltage, this current increases the input power factor and lowers the input current. The high frequency component of the input current is removed by the filter circuit 12.

In the current of the fluorescent lamp FL, low frequency ripple is reduced.

On the other hand, the current value detected by the current detection circuit 14 is compared with a reference voltage value by a comparator 19, and when it is determined that an overcurrent has occurred, the switching control unit 20 keeps changing the frequency without changing the frequency. The pulse width of the wave pulse is increased and the on-duty of the first switching device
The discharge time of the capacitor C2 of the
The voltage induced in the secondary winding Tr1b is reduced to reduce the output, thereby suppressing overcurrent. Since the control capacitor C5 is connected in series with the control inductor L2, the DC level of the voltage decreases when the on-time of the drive unit 17 increases, and resonance occurs in the control inductor L2 and the control capacitor C5. And the voltage tries to oscillate,
Since the resistor R1 is connected in series, the vibration is damped and the vibration is not increased, and the voltage induced in the control inductor L3 is prevented from becoming higher than necessary, so that the first switching device Q1 and the second To prevent the switching device Q2 from turning on and causing a short circuit state.

When the power is turned on, the first capacitor
The inrush current to C2 is that the primary winding Tr1a of the isolation transformer Tr1 is connected in series to the first capacitor C2, and that the second switching device Q2 is turned on and off at a high frequency. Thus, it is reduced.

With respect to the above embodiment, the same effect can be obtained even if the connection positions of the first switching device Q1 and the second switching device Q2 are reversed. In this case, the respective switching devices for controlling the ON period are also reversed.

In the above embodiment, the configuration using the field effect transistor has been described. However, a switching element having no parasitic diode, such as a bipolar transistor, can be similarly configured. When used, a diode whose conduction direction is reversed may be connected between the collector and the emitter, or when a diode is connected between the emitter and the base, this diode may be used.

Further, the same effect can be obtained by using not only an insulating transformer but also an autotransformer or a coil.

Further, the current detection circuit 14 is located on the low voltage side of the first capacitor C2, but is not limited to this position, and the current of the commercial AC power supply e rectified by the full-wave rectifier 13 flows. , Full-wave rectifier 13, second switching device
Q2, the primary winding Tr1a of the isolation transformer Tr1, the first capacitor C2, and the path of the full-wave rectifier 13 may be located. However, if the capacitor is located on the low voltage side of the first capacitor C2, the configuration can be simplified because the voltage swings in the positive direction in addition to the ground level.

Next, the experimental results will be described.

FIG. 3 is a circuit diagram showing the first switch drive circuit 15, and FIG. 4 is a waveform diagram using this circuit. In this experiment, the first switch drive circuit 15 having the configuration shown in FIG. 3 was used. The driving unit 17 includes a parallel circuit of a resistor R2 and a diode D2 connected between the resistor R1 and the gate of the first switching device Q1, and a gate of the first switching device Q1,
A parallel circuit of a resistor R3 and a capacitor C7 is connected between the sources, and a buffer 21 is connected. The fluorescent lamp FL uses two lamps of 40 W, the resistance value of the resistor R1 is 47Ω, the capacitance of the control capacitor C5 is 0.56 μF, and the inductance of the control inductor L2 is 3.75 mH.

When the overcurrent is detected by the comparator 19 and the output of the comparator 19 changes, as shown in FIG. 4, the pulse width of the rectangular wave pulse applied between the gate and the source of the first switching device Q1 Rapidly increases, but during the period in which the first switching device Q1 is on, the second switching device Q2 reliably keeps the off state, and both the first switching device Q1 and the second switching device Q2 Are not turned on at the same time, thereby preventing a short circuit from occurring and a large current from flowing.

FIG. 5 is a circuit diagram showing a second switch driving circuit 16. The second switch driving circuit 16 includes a driving section 18.
Is connected between a connection point of the diode D1 and the control capacitor C6 and the gate of the second switching device Q2, and an emitter of the transistor Q3 is connected between both ends of the resistor R4.
The base is connected and the source is the second switching device Q2
, And a parallel circuit of a resistor R5 and a capacitor C8 is connected between the drain and the source of the second switching device Q2.

When a voltage having a polarity for turning on the second switching device Q2 is induced in the control inductor L3, the voltage for turning on the second switching device Q2 is clamped by the forward voltage of the diode D1. Then, the second switching device Q2 is turned on. On the other hand, when a voltage having a polarity that turns off the second switching device Q2 is induced in the control inductor L3, the voltage is returned by the diode D1 and the transistor Q3 is turned on so that the second switching device Q2 is not turned on. To

FIGS. 6 to 8 are circuit diagrams showing a second switch driving circuit 16 according to another embodiment.

The second switch driving circuit 16 shown in FIG.
In the second switch driving circuit 16 shown in FIG. 5, a Zener diode ZD1 is connected instead of the diode D1. As described above, by using the Zener diode ZD1, the voltage for turning on the second switching device Q2 is clamped by the Zener voltage, the level of the entire driving voltage is reduced, and the polarity for turning off the second switching device Q2 is turned off. Therefore, when a voltage is induced in the control inductor L3, the second switching device Q2 is reliably turned off. Note that the zener voltage may be set to a voltage that drives the second switching device Q2.

The second switch driving circuit shown in FIG.
In the second switching drive circuit 16 shown in FIG. 6, a zener diode ZD2 having a polarity opposite to that of the zener diode ZD1 is connected in series with the zener diode ZD1, and a diode D3 is connected to the collector of the transistor Q3. It was done. Thus, Zener diode ZD2
Is connected, the voltage in the direction of turning off the second switching device Q2 is also clamped by the zener voltage, the level of the entire driving voltage is reduced, and the polarity for turning off the second switching device Q2 is applied to the control inductor L3. When a voltage is induced, the second switching device Q2 is reliably turned off. The diode D3 is connected to a transistor
This is because the diode existing between the collector and the base of the PNP of Q3, that is, the collector and the base eliminate the effect of the forward voltage in the forward direction. The zener voltage is 1/5 to 1 of the voltage for driving the second switching device Q2.
It may be set to about / 4.

Further, the second switch driving circuit 16 shown in FIG. 8 differs from the second switch driving circuit 16 shown in FIG. 7 in that the diode D3 is eliminated and the collector of the transistor Q3 is replaced by the zener diodes ZD1 and ZD2. Connected to a connection point. Thus, the diode
Even if D3 is omitted, the PN junction of the zener diode ZD2 functions as the diode D3, and the circuit configuration is simplified as compared with the case shown in FIG.

Next, a discharge lamp lighting device according to another embodiment will be described with reference to FIG.

FIG. 9 is a circuit diagram showing a discharge lamp lighting device according to another embodiment. In the discharge lamp lighting device 11 shown in FIG.
The first switching device Q1 was located on the high voltage side, the second switching device Q2 was located on the low voltage side, the first capacitor C1 was located on the high voltage side, and the second capacitor C2 was located on the low voltage side. Things. Switching control unit
Reference numeral 20 directly controls the second switching device Q2, and connects the diode D1 to the first switching device Q1. Further, the current detection circuit 14 is located on the low voltage side of the second switching device Q2. In this case, not only in this position, but also in the primary winding of the full-wave rectifier 13, the second switching device Q2, and the isolation transformer Tr1, through which the current of the commercial AC power supply e rectified by the full-wave rectifier 13 flows. It may be located in any of the paths of Tr1a, first capacitor C2, and full-wave rectifier 13. However, if the switching device is located on the low voltage side of the second switching device Q2, the configuration can be simplified because the voltage swings in the positive direction while being at the ground level.

Basically, the operation is the same as that of the discharge lamp lighting device shown in FIG. 1, but when the comparator 19 determines that an overcurrent has occurred, the switching control unit 20 operates in a state where the frequency is not changed. , Shorten the pulse width of the square wave pulse,
The on-duty of the second switching device Q2 is reduced to shorten the charging time of the first capacitor C2, reduce the voltage induced in the secondary winding Tr1b of the isolation transformer Tr1, and reduce the output by reducing the output. Suppress current. Further, as shown in FIG. 10 (e), the comparator 19 determines that an overcurrent has occurred, and as shown in FIG. 10 (a), the on-duty of the switching control unit 20 is reduced sharply to reduce the on-duty. 2
When the switching device Q2 is operated, as shown in FIG. 10B, the control capacitor C6 and the control inductor
The resonance of L3 swings to the positive side, and the voltage swinged to the negative side is induced in the control inductor L2, and the first switching device Q1
10D, a voltage applied to the negative electrode is applied as shown in FIG. 10D. Therefore, even if the control inductor L3 and the control capacitor C6 resonate due to a rapid change in on-duty, the first switching device Q1 and second switching device
Q2 does not turn on simultaneously and short-circuit current does not flow.

Further, the first switch driving circuit 16 is provided in the circuit shown in FIG.
Similar effects can be obtained by using any of the circuits shown in FIGS. 5 to 8 as in the embodiment shown in FIG.

Next, another embodiment will be described with reference to the drawings.

FIG. 11 is a circuit diagram showing a discharge lamp lighting device according to another embodiment, and FIG. 12 is a circuit diagram showing a switching control unit.

The embodiment shown in FIG. 11 is different from the embodiment shown in FIG. 1 in that the first switch driving circuit 15 for driving the first switching device Q1 comprises a resistor R1, a control inductor L2 and a control capacitor. C5 in series and the second
The second switch drive circuit 16 for driving the switching device Q2 is a series circuit of a resistor R6, a control inductor L3, and a control capacitor C6.

As shown in FIG. 12, the switching controller 20 has an oscillator 31 connected to a non-inverting input terminal of a comparator 32. On the other hand, a series circuit of a resistor R11 and a resistor R12 is connected between the voltage Vref and the ground, and a capacitor C11 is connected in parallel with the resistor R11.
The connection point of R11, resistor R12 and capacitor C11 is connected to the inverting input terminal of comparator 32, and this comparator
The buffer 33 is connected to the output terminal 32.

In this embodiment, FIG.
As shown in (a), the oscillator 31 outputs a saw-toothed output, and the switching controller 20 does not charge the capacitor C11 at the start of operation.
As shown in FIG. 13B, the comparator 32 outputs the first pulse width shorter than the second and subsequent pulses as shown in FIG. 13C. As shown in FIG. 14, the driving pulse for operating Q1 is set such that the width of the first pulse is, for example, about １ ／ narrower than the width of the second and subsequent pulses. Note that the frequency is constant. As described above, if the width of the first pulse is shortened, the amount of change of the transient phenomenon in the control inductor L2 and the control inductor L3 can be reduced, so that the first switching device Q1 and the second Switching devices Q2 are simultaneously turned on to cause a short circuit, thereby preventing a large current from flowing.

A switching control unit 20 according to another embodiment will be described with reference to FIG.

FIG. 15 is a circuit diagram showing a switching control unit according to another embodiment.

As shown in FIG. 15, the switch SW1 is connected to the under-voltage lock-out (UVLO) device 35.
The switch SW1 is connected to a capacitor C12 and a buffer 36 formed by transistors Q5 and Q6, and an operational amplifier 37 is connected to the transistors Q5 and Q6.

When the UVLO device 35 detects a voltage higher than a predetermined value, the switch SW1 is closed, and the capacitor C1 is closed.
2 is charged and the voltage for driving the first switching device Q1 is slowed down and activated as shown in FIG. 16 (b) due to the delay caused by the charging of the capacitor C12. Is set slightly longer than the oscillation cycle. Thus, if the width of the first pulse is reduced, the control inductor L2 and the control inductor
Since the amount of change in the transient phenomenon at L3 can be reduced, both the first switching device Q1 and the second switching device Q2 are simultaneously turned on to cause a short circuit, thereby preventing a large current from flowing.

The discharge lamp lighting device 11 shown in FIG.
Has a dimming function, and has a first switching device Q1
By increasing the on-duty and shortening the second on-duty, the output is reduced and the fluorescent lamp FL is darkened. Conversely, the on-duty of the first switching device Q1 is shortened and the second switching is reduced. By increasing the on-duty of device Q2, the output increases and the fluorescent lamp
FL becomes brighter.

Further, the discharge lamp lighting device 11 has a preheating mode, a starting mode, and a lighting mode, each of which outputs power optimum for the state of the fluorescent lamp FL.

Further, if the capacities of the first capacitor C2 and the second capacitor C3 are made substantially the same and the on-duties of the first switching device Q1 and the second switching device Q2 are made the same, a half-bridge type In this half-bridge type inverter circuit, the first switching device Q1 and the second switching device Q2 are simultaneously turned on by shortening the first pulse width or delaying the rising edge of the inverter circuit. As a result, a short circuit occurs and a large current can be prevented from flowing.

Next, a discharge lamp lighting device according to another embodiment will be described with reference to FIG.

FIG. 17 is a circuit diagram showing a discharge lamp lighting device according to another embodiment, and FIG. 18 is a circuit diagram showing a first drive circuit.

A smoothing capacitor C21 is connected to the commercial AC power supply e via the full-wave rectifier 13, and the smoothing capacitor C21 is connected to a half-bridge type inverter circuit 41.
The first switching device Q11 and the second switching device Q12 are connected in series.
Switching device Q11 and second switching device
During Q12, the overcurrent detection circuit 42
And a series circuit of a capacitor C22 and a capacitor C23 is connected to the smoothing capacitor C21. Further, an insulating transformer Tr1 is connected between a connection point between the first switching device Q11 and the second switching device Q12 via the overcurrent detection circuit 42 and a connection point between the capacitors C22 and C23. .

Further, a first drive circuit 43 is connected to the first switching device Q11, and the second switching device Q1
The second drive circuit 44 is connected to 2.

The first drive circuit 43 is connected to the gate of the first switching device Q11 via the overcurrent detection circuit 42,
A series circuit of a control capacitor C24 and a control inductor L11, a diode D11 and a resistor R21
Are connected in parallel, and a connection point between the control capacitor C24 and the control inductor L11 is connected to a polarity detection circuit 45. The polarity detection circuit 45 is connected to the first switching device Q11 via the overcurrent detection circuit 42. Gate and source are connected. Further, in the polarity detection circuit 45, when a voltage polarity in a direction for turning on the first switching device Q11 occurs in the control inductor L11, the switch 46 is opened to enable the first switching device Q11 to be turned on. When a voltage polarity in the direction for turning off the first switching device Q12 is generated in the application inductor L11, the switch 46 is closed to maintain the first switching device Q11 in the off state.

The second drive circuit 44 includes a resistor R22, a control capacitor C25, and a control inductor L12 magnetically connected to the control inductor L11 between the gate and the source of the second switching device Q12. The series circuit and the resistor R23 are connected. Further, a switching control unit 47 connected to the overcurrent detection circuit 42 is connected between the control capacitor C25 and the resistor R22.

Further, the polarity detection circuit 45 includes a diode D1
The collector and the emitter of the transistor Q14 are connected between both ends of the transistor Q14. The base of the transistor Q14 is connected to the gate of the first switching device Q11 via the resistor R24. The transistor Q15 is connected between the base and the emitter of the transistor Q14. The collector and the emitter of the transistor Q15 are connected, and a parallel circuit of a resistor R26 and a diode D12 is connected between the base and the emitter of the transistor Q15.The base of the transistor Q15 is connected to a connection point of the control capacitor C24 and the control inductor L11. Have been.

Next, the operation of the above embodiment will be described.

First, the direct current rectified by the full-wave rectifier 13 and smoothed by the capacitor C21 is supplied to the first switching device Q1.
The first and second switching devices Q12 are alternately turned on to turn on the fluorescent lamp FL with high-frequency AC.

When the overcurrent is detected by the overcurrent detection circuit 42, the on-duty for turning on the second switching device Q12 is increased by the switching control unit 47, and the control inductor L11 is inverted to the control inductor L12. A voltage is induced to control the first switching device Q11 and the second switching device Q12, respectively.

In the first drive circuit 43, as shown in FIG. 19, when a voltage polarity occurs in the direction for turning on the first switching device Q11, the transistor Q15 turns on, the transistor Q14 turns off, and the first driving circuit 43 turns off. 1 switching device Q11
Is turned on. Conversely, when a voltage polarity occurs in the direction of turning off the first switching device Q11, the transistor Q15 turns off, the transistor Q14 turns on, and the first switching device Q11 turns on.
Since the driving voltage is not generated in the switching device Q11 and is set to the zero level, the first switching device Q11 can be surely turned off.

Therefore, if the on-duty is changed abruptly, the drive signal of the first switching device Q11 does not drop to zero level, but the polarity detection circuit 45 forcibly turns off the first switching device Q11. Therefore, both the first switching device Q1 and the second switching device Q2 are turned on at the same time to cause a short circuit, thereby preventing a large current from flowing.

In the configuration shown in FIG. 17, the capacitance of the capacitor C23 is made larger than that of the capacitor C22, and the first switching device Q11 and the second switching device Q12 are driven in a non-smooth state, whereby the configuration shown in FIG. It is also possible to adopt the same configuration as shown in FIG.

Another embodiment will be described with reference to FIG.

FIG. 20 is a circuit diagram showing a discharge lamp lighting device according to another embodiment. The discharge lamp lighting device shown in FIG.
In the embodiment shown in FIG. 1, the first switching device Q11 and the second switching device Q12 are half-bridge type inverters 51, and a DC cut capacitor C3 is provided.
1 and a fluorescent lamp FL connected via a ballast choke L21.

As described above, even in the case of a half-bridge type inverter, by connecting the resistor R1 to the inverter of FIG.
As shown in FIG. 1, the first switching device Q1 and the second
Switching devices Q2 are simultaneously turned on to cause a short circuit, thereby preventing a large current from flowing.

In this embodiment, the second switch drive circuit 16 shown in FIGS. 5 to 9 can be applied.

As a power supply, a pre-regulator such as an AC / DC converter may be connected after rectifying the commercial AC power supply e, or a DC power supply may be simply connected.

[0089]

According to the first aspect of the present invention, when an abnormality is detected by the abnormality detecting means, the output of the output circuit is reduced by the switching control means. Even if resonance occurs in the control inductor and control capacitor, a DC component is added because the resistor is connected, and the resonance of the control inductor and control capacitor is damped. It is possible to prevent the devices from being turned on at the same time.

According to the second aspect of the present invention, when the abnormality is detected by the abnormality detecting means, the output of the output circuit is reduced by the switching control means. Even if resonance occurs in the inductor and the control capacitor, a DC component is added due to the connection of the resistor, and the resonance of the control inductor and the control capacitor is damped. It can be prevented that they are turned on at the same time.

According to the power supply device of the third aspect, since the output time of the drive signal for turning on the switching device after the operation is started is shortened, it is possible to prevent both switching devices from being simultaneously turned on.

According to the power supply device of the fourth aspect, since the output time of the drive signal for turning on the switching device after the start of operation is shortened, it is possible to prevent both switching devices from being simultaneously turned on.

According to the power supply device of the fifth aspect, it is possible to prevent both switching devices from being simultaneously turned on by delaying the rise of the switching device after the operation starts.

According to the power supply device of the sixth aspect, it is possible to prevent both switching devices from being simultaneously turned on by delaying the rising of the switching devices after the operation starts.

According to the power supply device of the seventh aspect, the polarity of the control inductor for controlling the other switching device which is not one of the switching devices controlled by the switching control means is detected, and the other switching device is turned on. When the polarity is not the same, the other switching device is forcibly turned off by the forced off means, and it is possible to prevent both switching devices from being simultaneously turned on.

According to the power supply device of the eighth aspect, the polarity of the control inductor for controlling the other switching device which is not one of the switching devices controlled by the switching control means is detected, and the other switching device is turned on. When the polarity is not the same, the other switching device is forcibly turned off by the forced off means, and it is possible to prevent both switching devices from being simultaneously turned on.

According to the discharge lamp lighting device of the ninth aspect,
Since the power supply device according to any one of claims 1 to 8 is provided with the discharge lamp connected to the output circuit, the respective effects are exhibited.

According to the illuminating device of the tenth aspect, since the apparatus main body to which the discharge lamp lighting device of the ninth aspect is provided and the discharge lamp is mounted is provided, the respective effects are exhibited.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing an appearance of the lighting device.

FIG. 3 is a circuit diagram showing a first switch driving circuit according to the first embodiment;

FIG. 4 is a waveform chart showing the same operation. (A) Gate and source voltage of the second switching device Q2 (b) Gate and source voltage of the first switching device Q1 (c) Output of the comparator 19

FIG. 5 is a circuit diagram showing a second switch driving circuit according to another embodiment of the present invention;

FIG. 6 is a circuit diagram showing a second switch driving circuit according to another embodiment of the present invention;

FIG. 7 is a circuit diagram showing a second switch driving circuit according to still another embodiment of the present invention.

FIG. 8 is a circuit diagram showing a second switch driving circuit according to still another embodiment of the present invention;

FIG. 9 is a circuit diagram showing a discharge lamp lighting device according to another embodiment of the present invention.

FIG. 10 is a waveform chart showing the same operation. (A) voltage of the second switching device Q2 (b) voltage of the control inductor L3 (c) voltage of the control inductor L3 (d) voltage of the first switching device Q1 (e) output of the comparator 19

FIG. 11 is a circuit diagram showing a discharge lamp lighting device according to another embodiment of the present invention.

FIG. 12 is a circuit diagram showing a switching control unit according to the third embodiment;

FIG. 13 is a waveform chart showing the same operation. (A) Non-inverted input of comparator 32 (b) Inverted input of comparator 32 (c) Output of comparator 32

FIG. 14 is a waveform chart showing the above operation. (A) Driving voltage of second switching device Q2 (b) Driving voltage of first switching device Q1

FIG. 15 is a circuit diagram showing a switching control unit according to another embodiment of the present invention;

FIG. 16 is a waveform chart showing the same operation. (A) Driving voltage of second switching device Q2 (b) Driving voltage of first switching device Q1

FIG. 17 is a circuit diagram showing a discharge lamp lighting device according to another embodiment of the present invention.

FIG. 18 is a circuit diagram showing a first drive circuit of the above.

FIG. 19 is a waveform chart showing the above operation. (A) Voltage V1 (b) Voltage VL11

FIG. 20 is a circuit diagram showing a discharge lamp lighting device according to another embodiment of the present invention.

FIG. 21 is a waveform chart showing the above operation. (A) Voltage of the switching control unit 20 (b) Voltage of the control inductor L2 (c) Voltage of the control inductor L3 (d) Voltage of the second switching device Q2

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Apparatus main body 11 Discharge lamp lighting device 13 Full-wave rectifier 20 Switching control part as switching control means 42 Overcurrent detection circuit as abnormality detection means C2 First capacitor C3 Second capacitor C5, C6 Control capacitor e Commercial AC power supply FL Fluorescent lamp as discharge lamp L2, L3 Control inductor Q1, Q2 Switching device Tr1 Insulation transformer Tr1b Inductor Secondary winding as output circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keiichi Shimizu 4-3-1 Higashi Shinagawa, Shinagawa-ku, Tokyo Toshiba Lighting & Technology Corporation

Claims (10)

[Claims] 1. A pair of switching devices provided in series between output terminals of a DC power supply; and magnetically connected to the pair of switching devices to turn on and off the switching devices alternately. A pair of control inductors; a pair of control capacitors connected to these control inductors and resonating with each other; an output circuit that outputs based on the operation of the switching device; an abnormality detection unit that detects abnormality; Switching control means for controlling the device and lowering the output of the output circuit when an abnormality is detected by the abnormality detection means; a resistor connected to a control inductor and a control capacitor of the switching device controlled by the switching control means And a power supply device comprising: 2. A rectifier for rectifying an output voltage of an AC power supply and outputting a non-smooth DC voltage; provided in series between output terminals of the rectifier, alternately at a frequency higher than an output frequency of the rectifier. A pair of switching devices that turn on and off; a pair of magnetically connected control inductors that are respectively connected to the pair of switching devices and that turn the switching devices on and off alternately; A pair of control capacitors that resonate; a series circuit of a first capacitor and an inductor that smoothes the output frequency of the rectifier provided between both terminals of one of the switching devices; A second capacitor that resonates in cooperation with the inductor when turned off; An output circuit for lighting a discharge lamp based on resonance; an abnormality detection means for detecting an abnormality; switching for controlling one of the switching devices and reducing the output of the output circuit when the abnormality detection means detects an abnormality. A power supply device comprising: a control unit; and a resistor connected to a control inductor and a control capacitor of the switching device controlled by the switching control unit. 3. A pair of switching devices provided in series with each other between output terminals of a DC power supply; and magnetically connected to the pair of switching devices, respectively, to turn on and off the switching devices alternately. A pair of control inductors; a pair of control capacitors connected to these control inductors and resonating with each other; an output circuit that outputs based on the operation of the switching device; and controls one of the switching devices and starts operation after the operation. A switching control means for shortening an output time of a drive signal for turning on the switching device. 4. A rectifier for rectifying an output voltage of an AC power supply and outputting a non-smooth DC voltage; provided in series between output terminals of the rectifier, alternately at a frequency higher than an output frequency of the rectifier. A pair of switching devices that turn on and off; a pair of magnetically connected control inductors that are respectively connected to the pair of switching devices and that turn the switching devices on and off alternately; A pair of control capacitors that resonate; a series circuit of a first capacitor and an inductor that smoothes the output frequency of the rectifier provided between both terminals of one of the switching devices; A second capacitor that resonates in cooperation with the inductor when turned off; An output circuit for lighting a discharge lamp based on resonance; and switching control means for controlling one of the switching devices and shortening an output time of a drive signal for turning on the switching device after the operation is started. A power supply device characterized by the above-mentioned. 5. A pair of switching devices provided in series between output terminals of a DC power supply; and magnetically connected to the pair of switching devices, respectively, for turning on and off the switching devices alternately. A pair of control inductors; a pair of control capacitors connected to these control inductors and resonating with each other; an output circuit that outputs based on the operation of the switching device; and controls one of the switching devices and starts operation after the operation. A switching control means for delaying the on-rise of the switching device; and a power supply device. 6. A rectifier for rectifying an output voltage of an AC power supply and outputting a non-smooth DC voltage; provided in series between output terminals of the rectifier, alternately at a frequency higher than an output frequency of the rectifier. A pair of switching devices that are turned on and off; a pair of magnetically connected control inductors that are respectively connected to the pair of switching devices and that turn the switching devices on and off alternately; A pair of control capacitors that resonate; a series circuit of a first capacitor and an inductor that smoothes the output frequency of the rectifier provided between both terminals of one of the switching devices; A second capacitor that resonates in cooperation with the inductor when turned off; An output circuit for lighting the discharge lamp based on the resonance; switching control means for controlling one of the switching devices and delaying the rise of the on-state of the switching device after the operation starts;
A power supply device comprising: 7. A pair of switching devices provided in series between output terminals of a DC power supply; and magnetically connected to the pair of switching devices, respectively, for turning on and off the switching devices alternately. A pair of control inductors; a pair of control capacitors connected to the control inductors and resonating with each other; an output circuit that outputs based on the operation of the switching device; a switching control unit that controls one of the switching devices; The polarity of the control inductor that controls the other switching device that is not one of the switching devices controlled by the switching control means is detected, and when the polarity is not the one that turns on the other switching device, the other switching device is forcibly turned on. Means for forcibly turning off the power supply; Power supply device characterized by the above-mentioned. 8. A rectifier for rectifying an output voltage of an AC power supply to output a non-smooth DC voltage; provided in series between output terminals of the rectifier, alternately at a frequency higher than an output frequency of the rectifier. A pair of switching devices that are turned on and off; a pair of magnetically connected control inductors that are respectively connected to the pair of switching devices and that turn the switching devices on and off alternately; A pair of control capacitors that resonate; a series circuit of a first capacitor and an inductor that smoothes the output frequency of the rectifier provided between both terminals of one of the switching devices; A second capacitor that resonates in cooperation with the inductor when turned off; An output circuit for lighting a discharge lamp based on resonance; switching control means for controlling one of the switching devices; and a control for controlling the other switching device which is not one of the switching devices controlled by the switching control means. And a forcible off means for detecting the polarity of the inductor and forcibly turning off the other switching device when the polarity is not the one for turning on the other switching device. 9. A discharge lamp lighting device comprising the power supply device according to claim 1, wherein a discharge lamp is connected to the output circuit. 10. An illuminating device comprising: the discharge lamp lighting device according to claim 9; and a fixture main body provided with the discharge lamp lighting device and to which a discharge lamp is mounted.