JP2000312485A - Power unit and electrodeless discharge lamp operating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent break of the switching element of an output circuit when controlling the output power of the circuit, when power supply is turned on or according to an output control signal from the outside. SOLUTION: An output circuit 5 supplies high frequency generated from a high frequency generating circuit 1 to an electrodeless discharge lamp 20, after amplifying the frequency by means of a switching element Q5. During a fixed period of time after DC power supply E is turned on, the output of a timer circuit 9 becomes higher in level, and the switching element Q3 of a short-circuiting circuit 6 is turned on. Consequently, both ends of the primary winding n1 of a drive transformer CT1 and the gate and source of the switching elements Q5 are respectively short-circuited to each other. Therefore, no pulse-like high voltage is generated across both ends of the induction coil 8 of the discharge lamp 20, and the stress applied to the switching element Q5 is reduced at the start of the output circuit 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for supplying high-frequency power to a load, and to an electrodeless discharge lamp lighting device for lighting an electrodeless discharge lamp using the power supply.

[0002]

2. Description of the Related Art Conventionally, a power supply device as shown in FIG. 6 is known (see Japanese Patent Application Laid-Open No. 7-326483).
In this power supply device, a DC power supply E is supplied as a power supply, a high frequency generated by an oscillation circuit 1a is amplified by a preamplifier 1b, and an output of the preamplifier 1b is further amplified by an output circuit 5 to load the electrodeless discharge lamp 20 as a load. By supplying to
The electrodeless discharge lamp 20 is turned on.

The oscillation circuit 1a generates a high frequency using the crystal oscillator X and the transistor Q2, and is an unadjusted oscillation circuit in which a low-Q tuning circuit is formed by the inductor L6 and the capacitor C15. Preamplifier 1b
Uses the transistor Q4 to connect the output of the oscillation circuit 1a to C
The resistors R8 to R10 constitute an attenuator. The output circuit 5 amplifies the high frequency output from the preamplifier 1b by a switching element Q5 composed of a MOSFET.

[0006] A filter circuit 3 is inserted between the DC power supply E and the output circuit 5 to prevent a high frequency from the output circuit 5 from returning to the DC power supply E. A matching circuit 4 is inserted between the output circuit 5 and the electrodeless discharge lamp 20 to perform impedance matching between the output circuit 5 and the electrodeless discharge lamp 20 and eliminate reflection of high-frequency power to the electrodeless discharge lamp 20. Power supply efficiency.

The electrodeless discharge lamp 20 is a bulb 7 in which a discharge gas such as an inert gas or metal vapor is sealed in a glass bulb.
And an induction coil 8 consisting of a few turns of an air-core coil wound close to the outer periphery of the bulb 7. The induction coil 8 supplies high-frequency power to the discharge gas in the bulb 7.

Further, in the power supply device shown in FIG. 6, a short circuit 6 for dimming the base and emitter of the transistor Q4 and the gate and source of the switching element Q5 in accordance with an external output control signal is provided for dimming. I have.
The short circuit 6 is a switching element Q composed of a MOSFET.
3, and an external output control signal is input to the gate and source of the switching element Q3. The source of switching element Q3 is grounded, and the drain is connected to the base of transistor Q4 and the gate of switching element Q5 via two diodes D1 and D2, respectively.

When the DC power supply E is supplied by the above circuit,
High frequency power is supplied from the output circuit 5 to the induction coil 8,
A high frequency current of several MHz to several hundred MHz flows through the induction coil 8. At this time, the discharge gas in the bulb 7 is discharged by the high-frequency electromagnetic field generated around the induction coil 8, the electrodeless discharge lamp 20 is turned on, and the bulb 7 emits ultraviolet light or visible light.

As an output control signal input to the short circuit 6, a binary signal of H level or L level is used.
During the period when the output control signal to the short circuit 6 is at the L level, the switching element Q3 is in the off state, so that the short circuit 6 does not affect the preamplifier 1b and the output circuit 5, and the electrodeless discharge lamp 20 is turned on. I do. On the other hand, during the period when the output control signal to short circuit 6 is at the H level, switching element Q3 is on, and both the base and emitter of transistor Q4 and the gate and source of switching element Q5 are short-circuited. 5, no high-frequency power is output, and the electrodeless discharge lamp 20 is turned off.

As described above, in the power supply device shown in FIG. 6, the short circuit 6 causes the output circuit 5 to respond to the output control signal.
Can be controlled, and the electrodeless discharge lamp 20 can be turned on and off. Here, the electrodeless discharge lamp 20
Is blinked at a high repetition cycle that does not give a flicker to the eyes, and by adjusting the ratio of the H level period to the L level period of the output control signal, the light output of the electrodeless discharge lamp 20 can be adjusted. Light control can be performed. This type of control is sometimes referred to as time division control.

[0010]

As shown in FIG. 7, the gate of the switching element Q5 of the output circuit 5
In order to adjust the high frequency input between the sources to an appropriate amplitude, or to reduce the loss in the transistor Q4 of the preamplifier 1b, the preamplifier 1b and the output circuit 5
It is conceivable that a drive transformer CT1 is inserted between the two. The primary winding n1 of the driving transformer CT1 is connected between the collector and the emitter of the transistor Q4, and the secondary winding n2 is a gate (control terminal) of the switching element Q5.
And source.

The power supply device shown in FIG. 7 includes a short circuit 6 as in the configuration shown in FIG. Assuming that the switching element Q3 of the short circuit 6 is turned on and off in this circuit, the voltage across the induction coil 8 has a waveform as shown in FIG. At each time t) shown in the figure, a pulse-like high voltage P is generated. When such a pulsed high voltage P is generated,
Since stress is applied to the switching element Q5 of the output circuit 5, components having a high withstand voltage are required for the switching element Q5, and in some cases, the switching element Q5 may be destroyed.

The cause of the generation of the pulsed high voltage P is presumed as follows. That is, when the electrodeless discharge lamp 20 is started, in other words, at the moment when the switching element Q3 of the short circuit 6 is turned off, the base / emitter of the transistor Q4 and the gate / source of the switching element Q5 respectively shift from the short-circuit state to the non-short-circuit state. I do. Here, when the switching element Q5 is operated at a high frequency (for example, 0.5 to several hundred MHz) via the driving transformer CT1, the wiring capacitance from the preamplifier 1b to the output circuit 5 and the voltage between both ends of each winding of the driving transformer CT1 are obtained. It is presumed that a pulsed high voltage P is generated due to the influence of stray capacitance or the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to control the switching elements of an output circuit when power is turned on or when the output power of the output circuit is controlled in response to an external output control signal. An object of the present invention is to provide a power supply device that prevents destruction and an electrodeless discharge lamp lighting device that lights an electrodeless discharge lamp using the power supply device.

[0014]

According to a first aspect of the present invention, there is provided a high frequency generating circuit for generating a high frequency, an output circuit for outputting high frequency power to a load using a first switching element, and an output of the high frequency generating circuit. Is supplied to the primary winding and the first
A short-circuit state in which the control terminal of the switching element is short-circuited between both ends of the primary winding of the drive transformer connected to the secondary winding and the control terminal of the first switching element is grounded. And a short circuit that can be selected as a power supply. According to this configuration, both ends of the primary winding of the drive transformer are short-circuited by the short circuit and the control terminal of the first switching element of the output circuit is grounded, so that the wiring capacitance from the high frequency generation circuit to the output circuit is reduced. And the effect of stray capacitance between both ends of each winding of the drive transformer is reduced, so that a high-voltage pulse-like high voltage does not occur at both ends of the load when the output circuit is started, and the first switching element , The destruction of the first switching element can be prevented.

According to a second aspect of the present invention, in the first aspect of the present invention, the high-frequency generating circuit includes a second switching element connected between output terminals, and the short-circuiting circuit sets the second switching element to a short-circuit state. This includes a state where the control terminal of the element is grounded. According to this configuration, since the short-circuit circuit grounds the control terminal of the second switching element of the high-frequency generation circuit, the influence of the wiring capacitance and the like in the high-frequency generation circuit is reduced. Generation of a pulsed high voltage can be prevented.

According to a third aspect of the present invention, in the second aspect of the present invention, the high-frequency generating circuit has a resonance circuit including an inductor and a capacitor, and the capacitor is connected in parallel with the second switching element and is connected to the second switching element. 2 is arranged in the vicinity of the second switching element.
According to this configuration, since the capacitor of the resonance circuit is connected in parallel with the second switching element of the high-frequency generation circuit and is disposed near the second switching element, the connection between the second switching element and the capacitor is prevented. Since the inductance in the wiring between them becomes smaller and the waveform distortion in the second switching element becomes smaller, it is possible to prevent the generation of a pulse-like high voltage further than in the second aspect of the present invention.

According to a fourth aspect of the present invention, in the first or second aspect of the invention, the short circuit selects a short-circuit state at least for a preset period immediately after power-on. According to this configuration, the short circuit short-circuits both ends of the primary winding of the drive transformer and grounds the control terminal of the first switching element of the output circuit for a preset period immediately after power-on. The operation of the output circuit can be started after the power supply voltage is stabilized immediately after being turned on.

According to a fifth aspect of the present invention, in the first to third aspects of the present invention, the short circuit repeats selection / non-selection of a short-circuit state according to an output control signal from the outside, and the ratio thereof is controlled. Thus, the output power of the output circuit is controlled. According to this configuration, the output power can be adjusted using the output control signal.

According to a sixth aspect of the present invention, in the first to fifth aspects, the output frequency of the output circuit is 0.5
The frequency is set to several hundred MHz.

According to a seventh aspect of the present invention, in the first to sixth aspects of the present invention, a matching circuit is provided between the high-frequency generating circuit and the primary winding of the driving transformer for matching the impedance of the two. It is. According to this configuration, the impedance between the high-frequency generation circuit and the primary winding of the drive transformer can be matched by the matching circuit, so that the high frequency generated by the high-frequency generation circuit can be efficiently transmitted to the drive transformer. it can.

According to an eighth aspect of the present invention, in the first to seventh aspects, the high-frequency generating circuit has an oscillation circuit including a crystal oscillator. According to this configuration, the output frequency of the high-frequency generation circuit can be set by the crystal oscillator, and the output frequency of the high-frequency generation circuit can be stabilized.

According to a ninth aspect of the present invention, in the first to seventh aspects of the present invention, the high-frequency generating circuit is configured to allow a part of an oscillating current generated in the output circuit to flow to a primary winding of the driving transformer. It will return. According to this configuration, the high-frequency generation circuit feeds back a part of the oscillating current generated in the output circuit so as to flow to the primary winding of the drive transformer, so that the first switching element is self-excited and the first switching element is driven. The number of components is reduced and the circuit configuration is simplified as compared with a configuration in which the switching element is separately driven.

According to a tenth aspect of the present invention, in the first to ninth aspects of the present invention, the short circuit includes a plurality of diodes each having one end commonly connected to the other end of a third switching element having one end grounded. Wherein the plurality of diodes include a first diode having the other end connected to a control terminal of the first switching element, and one of the driving transformers.
And a second diode having the other end connected to the next winding. According to this configuration, the third circuit of the short circuit
Since one end of the plurality of diodes is commonly connected to the other end of the switching element, the plurality of places where the other ends of the plurality of diodes are connected by the third switching element can be simultaneously short-circuited. It is not necessary to provide a plurality of switching elements in order to short-circuit.

According to an eleventh aspect, in the tenth aspect, the series circuit of the third switching element and the first diode is arranged near a control terminal of the first switching element. Is what it is. According to this configuration, since the series circuit of the third switching element and the first diode of the short circuit is arranged near the first switching element of the output circuit, the first switching element is connected to the first switching element of the output circuit. Since the wiring capacitance to the first switching element via the diode is reduced and the waveform distortion in the first switching element is reduced, the generation of a pulse-like high voltage can also be suppressed.

According to a twelfth aspect of the present invention, there is provided a power supply device according to any one of the first to eleventh aspects, and an electrodeless discharge lamp as the load that is lit by high frequency power from the power supply device. It is an electrode discharge lamp lighting device.

According to a thirteenth aspect of the present invention, a high-frequency generating circuit for generating a high frequency of 0.5 to several hundreds of MHz having an oscillation circuit including a crystal oscillator, and outputting high-frequency power using the first switching element. An output circuit, a drive transformer in which the output of the high-frequency generation circuit is supplied to a primary winding and a control terminal of the first switching element is connected to a secondary winding, and illuminated by high-frequency power from the output circuit One end is commonly connected to the other end of a second switching element having one end grounded, and the other end is connected to a primary winding of the drive transformer and a control terminal of the first switching element, respectively. And a short-circuit having two diodes. The short-circuit short-circuits both ends of a primary winding of the drive transformer and connects a control terminal of the first switching element. It is an electrodeless discharge lamp lighting device being a state selectable for.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) In this embodiment, as shown in FIG. 1, in the power supply device shown in FIG.
diode D connected to the base of transistor Q4
1, a diode D is connected to the connection point between the primary winding n1 of the drive transformer CT1 and the drain of the switching element Q3.
3 are connected to each other.

In this embodiment, the high-frequency generation circuit 1 is constituted by the oscillation circuit 1a and the preamplifier 1b. Further, a timer circuit 9 is provided to prevent the output circuit 5 from starting during a preset period after the DC power supply E is turned on. Other configurations are the same as the conventional configuration shown in FIG.

The timer circuit 9 includes a series circuit of resistors R50 and R51, a series circuit of resistors R52 and R53, and a capacitor C
50, composed of a comparator IC1 and a resistor R5
The series circuit of 0 and R51 and the series circuit of resistors R52 and R53 are connected in parallel to the DC power supply E, respectively. Resistance R5
The non-inverting input terminal of the comparator IC1 is connected to the connection point of 0 and R51, the inverting input terminal of the comparator IC1 is connected to the connection point of the resistors R52 and R53, and the capacitor C50 is connected between both ends of the resistor R53. You. The output terminal of the comparator IC1 is connected to the gate of the switching element Q3 forming the short circuit 6.

In the timer circuit 9, when the DC power supply E is turned on, charging of the capacitor C50 starts via the resistor R52, and during a period when the voltage across the capacitor C50 is lower than the voltage across the resistor R51, the charge of the comparator IC1 is reduced. The output goes to H level. Thereafter, when the capacitor C50 is charged and the voltage across the capacitor C50 becomes higher than the voltage across the resistor R51, the output of the comparator IC1 becomes L level. Therefore, the output of the comparator IC1 is at the H level for a certain period of time after the power is turned on, and then shifts to the L level.

Next, the operation of the power supply device of this embodiment will be described. As shown in FIG. 2B, when the DC power supply E is turned on at time t0, the output of the timer circuit 9 goes to the H level as described above. At this time, the switching element Q3 of the short circuit 6 is turned on, and both ends of the primary winding n1 of the drive transformer CT1 and the gate and source of the switching element Q5 are short-circuited, so that the switching element Q5 is turned off. As a result, no high-frequency power is supplied from the output circuit 5 to the induction coil 8 of the electrodeless discharge lamp 20, and the electrodeless discharge lamp 20 is kept off. Here, the state when the switching element Q3 is turned on is referred to as a short-circuit state.

Thereafter, when the time set by the timer circuit 9 elapses and time t1 is reached, the output of the timer circuit 9 goes low. At this time, switching element Q3 is turned off, and both ends of primary winding n1 of drive transformer CT1 and the gate and source of switching element Q5 are no longer short-circuited, so that switching element Q5 starts operating. Thus, the high frequency power is supplied from the output circuit 5 to the induction coil 8, and the electrodeless discharge lamp 20 is turned on.

By the above-described operation, the voltage between both ends of the induction coil 8 has a waveform shown in FIG. That is, when the output circuit 5 is started (time t1), the pulse-like high voltage P shown in FIG. 8 is not generated. As a result, the stress applied to the switching element Q5 of the output circuit 5 can be reduced, and the destruction of the switching element Q5 can be prevented.

During the period set by the timer circuit 9 immediately after the DC power supply E is turned on, the short circuit 6 is in a short-circuit state and the operation of the output circuit 5 is stopped. An excessive current does not flow through the switching element Q5, and a large current can flow through the induction coil 8 from the start of energization, so that the electrodeless discharge lamp 20 is easily started.

(Embodiment 2) In this embodiment, as shown in FIG. 3, the preamplifier 1b includes a switching element Q53 composed of a MOSFET.
The short-circuit state can be selected by the short-circuit circuit 6 also for the gate and source of FIG. Also, the output circuit 5 has a MOS
Two switching elements Q51 and Q52 each composed of an FET
And the switching elements Q51 and Q52 are alternately turned on and off to output high-frequency power. Furthermore, since the output circuit 5 includes the two switching elements Q51 and Q52, the primary windings n21 and n2
Transformer C having two secondary windings n22 and n23
T2 is used. In the present embodiment, the commercial power supply A
C is converted to DC by a DC power supply circuit E1 to obtain a DC power supply.

The preamplifier 1b includes a switching element Q5
3 and a resonance circuit composed of a series circuit of an inductor L51 and a capacitor C51, and the oscillation circuit 1a
Is amplified by the switching element Q53 and output to the primary winding n21 of the drive transformer CT2. The capacitor C51 is connected in parallel with the switching element Q53, and is arranged near the switching element Q53.

The preamplifier 1b and the driving transformer CT2
The two capacitors C52, C
The matching circuit 10 constituted by 53 is inserted,
Preamplifier 1b and primary winding n21 of drive transformer CT2
And the impedance between them is matched.

The output circuit 5 includes a switching element Q51,
Q52 series circuit, inductor Ls and capacitor Cs
And a resonance circuit composed of a series circuit.
The output terminal of the DC power supply circuit E1 is connected to both ends of the series circuit of the switching elements Q51 and Q52. The secondary windings n22 and n23 of the drive transformer CT2 and the resistor R6 are connected between the gate and the source of each of the switching elements Q51 and Q52.
1 and R62 are connected to each other, and the induction coil 8 of the electrodeless discharge lamp 20 is connected between the drain and the source of the switching element Q52 via the resonance circuit including the inductor Ls and the capacitor Cs and the matching circuit 4.
Is connected. The matching circuit 4 is configured using three capacitors C30 to C32, and matches the impedance between the output circuit 5 and the induction coil 8.

The output of the preamplifier 1b is a driving transformer CT
2, the switching elements Q51, Q
52 are alternately turned on and off. That is, the preamplifier 1b
The high frequency output from is amplified by the output circuit 5 in class D,
It is supplied to the induction coil 8.

The short circuit 6 includes three diodes D2, D3, whose cathodes are commonly connected to the switching element Q3.
D4. The anodes of the diodes D2, D3, and D4 are connected to the gate of the switching element Q52, one end of the primary winding n21 of the driving transformer CT2, and the switching element Q5.
3 are connected to the respective gates.

Next, the operation of this embodiment will be described. When the commercial power supply AC is turned on, DC power is supplied from the DC power supply circuit E1.
Becomes H level. At this time, switching element Q3 is turned on, and both ends of primary winding n21 of drive transformer CT2 and the gates and sources of switching elements Q52 and Q53 are both short-circuited. No amplification is performed in 1b, and the switching elements Q51 and Q52 are also kept off. As a result, no high-frequency power is supplied from the output circuit 5 to the induction coil 8, and the electrodeless discharge lamp 20 is not turned on. Subsequent operations are the same as in the first embodiment.

In the present embodiment, the short circuit 6 causes not only the voltage between the both ends of the primary winding n21 of the drive transformer CT2 and the gate and source of the switching element Q52 of the output circuit 5, but also the high frequency generation circuit 1 (preamplifier 1b). By short-circuiting the gate and source of the switching element Q53, the influence of the wiring capacitance and the like in the high-frequency generation circuit 1 is reduced, so that the generation of the pulsed high voltage P can be prevented more reliably than in the first embodiment.

Further, by disposing the capacitor C51 of the first resonance circuit near the switching element Q53 of the high frequency generation circuit 1, the inductance in the wiring between the switching element Q53 and the capacitor C51 is reduced, and the switching element Q53 In this case, the waveform distortion is reduced, so that the generation of the pulse-like high voltage P can also be suppressed.

Further, a matching circuit 1 is provided between the high frequency generating circuit 1 and the primary winding n21 of the driving transformer CT2.
By inserting 0, the impedance of the high-frequency generation circuit 1 matches the impedance of the primary winding n21 of the drive transformer CT2, so that the high-frequency generated by the high-frequency generation circuit 1 can be efficiently transmitted to the drive transformer CT2. it can.

(Embodiment 3) In this embodiment, as shown in FIG. 4, in the configuration of Embodiment 2, a control circuit for providing an output control signal as a binary signal to the short circuit 6 instead of the timer circuit 9 11 is provided as an external circuit.

In this embodiment, the output power supplied from the output circuit 5 to the electrodeless discharge lamp 20 by the short circuit 6 can be controlled by the output control signal from the control circuit 11.
That is, when the electrodeless discharge lamp 20 is turned on and off at a high repetition cycle that does not give flicker to the eyes, and the duty ratio of the output control signal is changed by the control circuit 11, the brightness of the electrodeless discharge lamp 20 is changed. Dimming control can be performed.

In the present embodiment, when the dimming control of the electrodeless discharge lamp 20 is performed, the operation start and the operation stop of the output circuit 5 are repeated. Since both ends of the primary winding n21 and the gate and source of each of the switching elements Q52 and Q53 are short-circuited, a pulsed high voltage P may be generated at both ends of the induction coil 8 of the electrodeless discharge lamp 20. Absent.

(Embodiment 4) In this embodiment, as shown in FIG. 5, the output circuit 5 is composed of a series circuit of two switching elements Q54 and Q55 composed of MOSFETs and a series circuit of an inductor Ls and a capacitor Cs. A switching element Q5
4, Q55 is self-excitedly driven. Therefore, a circuit that feeds back a part of the high-frequency power generated by the output circuit 5 is used as the high-frequency generation circuit 1. This high-frequency power includes a primary winding n31 and two secondary windings n32,
n33 and is used for driving the switching elements Q54 and Q55 via the drive transformer CT3 having n33.

The output terminal of the DC power supply circuit E1 is connected to both ends of the series circuit of the switching elements Q54 and Q55.
The induction coil 8 of the electrodeless discharge lamp 20 is connected between the drain and the source of the switching element Q55 through the resonance circuit.
Is connected. The primary winding n31 of the driving transformer CT3,
A closed circuit is formed by the capacitor C54, the resonance circuit, and the induction coil 8, and each secondary winding n of the drive transformer CT3
Gates and sources of the switching elements Q54 and Q55 are connected to 32 and n33, respectively.

In the present embodiment, the starting circuit 12 for providing a starting pulse to the output circuit 5 immediately after the power is turned on is provided. This start pulse is applied to the gate and source of switching element Q55. A resistor R60 is connected between the drain and the source of the switching element Q54 to make the output circuit 5 easy to start.

The control circuit 11 and the short circuit 6 are provided similarly to the third embodiment. The short circuit 6 includes two diodes D5 and D6 whose cathodes are commonly connected to the drain of the switching element Q3. Each diode D5, D
6 is the primary winding n31 of the drive transformer CT3.
And the gate of the switching element Q55.

Next, the operation of the power supply device of this embodiment will be described. When the commercial power supply AC is turned on, DC power is supplied from the DC power supply circuit E1. And the starting circuit 1
2, a start pulse is applied to the gate and source of the switching element Q55 to turn on the switching element Q55,
An oscillating current is generated by the resonance action of the resonance circuit.
When this oscillating current flows through the primary winding n31 of the drive transformer CT3 via the capacitor C54, a high frequency is applied from each of the secondary windings n32 and n33 of the drive transformer CT3 to the gate and source of each of the switching elements Q54 and Q55. The switching elements Q54 and Q55 are alternately turned on and off. As a result, switching element Q5
High frequency power is supplied from the drain / source 5 to the induction coil 8 via the resonance circuit, and the electrodeless discharge lamp 20 is turned on. That is, the switching elements Q54 and Q55 are self-excited by flowing the oscillating current generated from the resonance circuit to the primary winding n31 of the drive transformer CT3.

In the present embodiment, when dimming control of the electrodeless discharge lamp 20 is performed, the driving transformer CT is controlled by the short circuit 6.
3 between the both ends of the primary winding n31 and the switching element Q
Since both the gate and the source of 55 are short-circuited, a pulse-like high voltage P is generated at both ends of the induction coil 8 of the electrodeless discharge lamp 20 while the switching elements Q54 and Q55 of the output circuit 5b are self-excited. Thus, the destruction of the switching elements Q54 and Q55 can be prevented. Other configurations and operations are the same as those of the third embodiment.

In each of the above-described embodiments, an example in which the output circuit is not started for a preset period immediately after the power is turned on by using the timer circuit 9, and an electrodeless discharge lamp 20 which is controlled by the control circuit 11. Although the example in which the dimming control is performed has been described above, the technical idea of the present invention is also applicable to a circuit that detects some abnormality at the time of no load or the like and interrupts the output of the output circuit. That is, what kind of circuit controls the output of the output circuit depending on whether the operation of short-circuiting both ends of the primary winding of the drive transformer and grounding the control terminal of the switching element of the output circuit is performed. It can also be applied to things.

[0056]

According to the first aspect of the present invention, there is provided a high frequency generating circuit for generating a high frequency, an output circuit for outputting a high frequency power to a load using a first switching element, and an output of the high frequency generating circuit being a primary winding. A drive transformer that is supplied to a wire and has a control terminal of the first switching element connected to a secondary winding, and a short circuit between both ends of a primary winding of the drive transformer and a control terminal of the first switching element. And a short-circuit that enables selection of a state in which the power supply is grounded as a short-circuit state. The short-circuit short-circuits both ends of the primary winding of the drive transformer and controls the first switching element of the output circuit. Grounding the terminals reduces the effects of wiring capacitance from the high-frequency generation circuit to the output circuit and stray capacitance between both ends of each winding of the drive transformer. Pulsed high voltage of the high voltage not occur across the load at the start of the circuit,
There is an effect that the stress applied to the first switching element can be reduced to prevent the destruction of the first switching element.

According to a second aspect of the present invention, in the first aspect of the present invention, the high-frequency generating circuit includes a second switching element connected between output terminals, and the short-circuit is in a short-circuit state when the second switching element is in a short-circuit state. This includes the state in which the control terminal of the element is grounded. Since the short circuit grounds the control terminal of the second switching element in the high frequency generation circuit, the influence of the wiring capacitance in the high frequency generation circuit is reduced. Thus, there is an effect that generation of a pulse-like high voltage can be prevented more reliably than in the first aspect of the present invention.

According to a third aspect of the present invention, in the second aspect of the present invention, the high-frequency generation circuit has a resonance circuit including an inductor and a capacitor, and the capacitor is connected in parallel with the second switching element. Since the second switching element is disposed near the second switching element, the inductance in the wiring between the second switching element and the capacitor is reduced, and the waveform distortion in the second switching element is reduced. There is an effect that the generation of a pulse-like high voltage can be prevented even more.

According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the short circuit selects a short-circuit state at least for a preset period immediately after the power is turned on. During a preset period, the short circuit short-circuits both ends of the primary winding of the drive transformer and grounds the control terminal of the first switching element of the output circuit. There is an advantage that the operation of the circuit can be started.

According to a fifth aspect of the present invention, in the first to third aspects of the present invention, the short circuit repeats selection / non-selection of a short circuit state according to an output control signal from the outside, and the ratio thereof is controlled. Accordingly, the output power of the output circuit is controlled, and there is an advantage that the output power can be adjusted using the output control signal.

According to a seventh aspect of the present invention, in the first to sixth aspects of the present invention, a matching circuit is provided between the high-frequency generating circuit and the primary winding of the drive transformer for matching the impedance of the two. Since the impedance between the high-frequency generation circuit and the primary winding of the driving transformer can be matched by the matching circuit,
There is an advantage that the high frequency generated by the high frequency generation circuit can be efficiently transmitted to the drive transformer.

According to an eighth aspect of the present invention, in the first to seventh aspects, the high-frequency generation circuit has an oscillation circuit including a crystal oscillator, and the output of the high-frequency generation circuit is controlled by the crystal oscillator. There is an advantage that the frequency can be set and the output frequency of the high-frequency generation circuit can be stabilized.

According to a ninth aspect of the present invention, in the first to seventh aspects of the present invention, the high-frequency generating circuit is configured to allow a part of an oscillating current generated in the output circuit to flow through a primary winding of the drive transformer. Since the feedback is provided, the first switching element is driven by self-excitation, which has the advantage that the number of components is reduced and the circuit configuration is simplified as compared with a configuration in which the first switching element is separately driven.

According to a tenth aspect of the present invention, in the first to ninth aspects, the short circuit comprises a plurality of diodes each having one end commonly connected to the other end of a third switching element having one end grounded. Wherein the plurality of diodes include a first diode having the other end connected to a control terminal of the first switching element, and one of the driving transformers.
The second winding includes a second diode having the other end connected thereto, and one end of the plurality of diodes is commonly connected to the other end of the third switching element of the short circuit. The third switching element can simultaneously short-circuit a plurality of locations where the other ends of the plurality of diodes are connected, and there is an advantage that it is not necessary to provide a plurality of switching elements to short-circuit the plurality of locations.

According to an eleventh aspect, in the tenth aspect, a series circuit of the third switching element and the first diode is disposed near a control terminal of the first switching element. Therefore, the wiring capacitance from the third switching element to the first switching element via the first diode is reduced, and the waveform distortion in the first switching element is reduced. There is an advantage in that generation of phenomena can be suppressed.

[Brief description of the drawings]

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

FIG. 2 is an operation waveform diagram of the above.

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

FIG. 4 is a circuit diagram according to a third embodiment of the present invention.

FIG. 5 is a circuit diagram according to a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram of a conventional example.

FIG. 7 is a circuit diagram of another conventional example.

FIG. 8 is an operation waveform diagram of the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High frequency generation circuit 1a Oscillation circuit 5 Output circuit 6 Short circuit 10 Matching circuit 20 Electrodeless discharge lamp C51 Capacitor CT1-CT3 Drive transformer D2-D6 Diode L51 Inductor n1, n21, n31 Primary winding Q3, Q5 Switching element Q51 Q55 Switching element X Quartz resonator

Claims (13)

[Claims] A high-frequency generating circuit for generating a high frequency; an output circuit for outputting high-frequency power to a load by using a first switching element; The control terminal of the switching element is 2
A drive transformer connected to the secondary winding, a short circuit that short-circuits both ends of the primary winding of the drive transformer and enables selection of a state in which the control terminal of the first switching element is grounded as a short-circuit state. A power supply device comprising: 2. The high frequency generating circuit includes a second switching element connected between output terminals, and the short circuit includes:
2. The short-circuit state includes a state in which a control terminal of the second switching element is grounded.
The power supply as described. 3. The high-frequency generation circuit has a resonance circuit including an inductor and a capacitor, and the capacitor is connected in parallel with the second switching element and is arranged near the second switching element. The power supply device according to claim 2, wherein: 4. The power supply device according to claim 1, wherein said short circuit selects a short-circuit state at least for a preset period immediately after power-on. 5. The output power of the output circuit is controlled by repeating selection / non-selection of a short-circuit state according to an output control signal from the outside and controlling a ratio thereof. The power supply device according to any one of claims 1 to 3, wherein 6. The power supply device according to claim 1, wherein an output frequency of said output circuit is set to 0.5 to several hundred MHz. 7. The circuit according to claim 1, further comprising a matching circuit provided between the high-frequency generating circuit and a primary winding of the driving transformer for matching impedances of the two. Power supply. 8. The power supply device according to claim 1, wherein the high-frequency generation circuit has an oscillation circuit including a crystal oscillator. 9. The high frequency generating circuit according to claim 1, wherein a part of the oscillating current generated in the output circuit is fed back to the primary winding of the driving transformer. A power supply according to any one of the above. 10. The short circuit includes a plurality of diodes having one end commonly connected to the other end of a third switching element having one end grounded, and the plurality of diodes includes the first diode. 3. A switching device comprising: a first diode having the other end connected to a control terminal of the switching element; and a second diode having the other end connected to a primary winding of the driving transformer. The power supply device according to any one of claims 1 to 9. 11. The power supply according to claim 10, wherein a series circuit of said third switching element and said first diode is arranged near a control terminal of said first switching element. apparatus. 12. An electrodeless electrode comprising: the power supply device according to claim 1; and an electrodeless discharge lamp as the load that is turned on by high-frequency power from the power supply device. Discharge lamp lighting device. 13. An oscillator having a crystal oscillator including a crystal oscillator.
A high-frequency generation circuit that generates a high frequency of 5 to several hundred MHz,
An output circuit for outputting high-frequency power using a first switching element, and a drive in which an output of the high-frequency generation circuit is supplied to a primary winding and a control terminal of the first switching element is connected to a secondary winding A transformer, an electrodeless discharge lamp that is lit by high-frequency power from the output circuit, and one end commonly connected to the other end of a second switching element having one end grounded, and the other end being a primary winding of the drive transformer. And the first
Connected to the control terminals of the switching elements of
A short circuit having a plurality of diodes, wherein the short circuit short-circuits both ends of the primary winding of the drive transformer and selects a state in which the control terminal of the first switching element is grounded. An electrodeless discharge lamp lighting device characterized in that: