JPH0898551A - Power supply device - Google Patents

Abstract

PURPOSE: To provide a small and low-cost power supply device by which a low-frequency inverter circuit can be driven with high efficiency by using a small pulse transformer. CONSTITUTION: As the drive circuit of switching elements Q1 to Q4 for polarity inversion in an inverter circuit 2 which is operated at a low frequency, the primary side of a pulse transformer is excited by a switching element, for drive, which is ON/OFF-driven at a high frequency which is 1000 times or higher the low frequency of at least the inverter circuit 2, and the high frequency transmitted to the secondary side is rectified by a rectifier element to supply respectively to the switching elements Q1 to Q4 driven at a low frequency. During a period in which the switching element for drive is operated at the high frequency, a time constant is set in such a way that the switching elements, for polarity inversion, corresponding to the switching element for drive maintain an ON-state.

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 for supplying a voltage of a substantially rectangular wave to a load, and is used, for example, in a lighting device for a high pressure discharge lamp.

[0002]

2. Description of the Related Art Conventionally, as a drive circuit of an inverter circuit for supplying a low-frequency rectangular wave voltage to a load, as disclosed in, for example, Japanese Utility Model Application Laid-Open No. 2-113300, a self-excited oscillation circuit is used for low-frequency drive. A circuit system is known in which a drive signal is created and the signal is supplied to a switching element for polarity reversal of an inverter circuit by using a photocoupler. However, in this conventional example, there is a problem that the circuit is complicated, photocouplers for signal transmission are required for the number of driven elements, the number of parts is large, and it is difficult to reduce the cost. In addition, there is a drawback that a large area is required for mounting the components, and miniaturization is difficult. In addition, when a low frequency (for example, several tens Hz to several hundreds Hz) inverter circuit is configured only by the driving pulse transformer without using a photocoupler, there is a drawback that the transformer becomes large.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to efficiently drive a low frequency inverter circuit using a small pulse transformer. An object is to provide a small-sized and inexpensive power supply device.

[0004]

In order to solve the above-mentioned problems, in the power supply device of the present invention, as shown in FIG. 1, a direct current power source E and the direct current power source E are switched at high frequencies. A DC voltage conversion circuit (DC / DC converter circuit) 1 for controlling the supply voltage to the load LP, and at least two polarity inversion switching elements Q _{1 to} Q ₄ for the polarity of the output voltage of the DC voltage conversion circuit 1. A polarity reversing circuit (inverter circuit) 2 that alternates at a low frequency by using a load circuit connected to the output terminal of the polarity reversing circuit 2, and the polarity reversing switching elements Q ₁ to As shown in FIG. 2, the drive circuit of Q ₄ includes two drive switching elements Qa and Qb that switch at a high frequency modulated with a low frequency for polarity reversal, and the drive switching elements. A pulse transformer PT having a primary winding connected to a driving DC power source Ed via Qa and Qb and a number of secondary windings corresponding to switching elements Q _{1 to} Q ₄ for polarity reversal, and this pulse Transformer PT 2
Driving switching elements Qa (, Qb), which are composed of rectifying elements D _{1 to} D ₄ respectively connected to the next winding side.
As shown in FIG. 3, the polarity inversion switching elements Q ₁ and Q ₄ (Q ₂ and Q ₃ ) corresponding to the driving switching element Qa (and Qb) are in the ON state during the period when the In order to maintain the above condition, the time constant of the drive circuit for the polarity reversing switching elements Q _{1 to} Q ₄ is set. Note that, as shown in FIG. 10, if the transformer T of the DC voltage conversion circuit is also used as the pulse transformer of the drive circuit, further downsizing can be achieved, which is convenient.

[0005]

According to the present invention, the polarity inverting switching elements Q _{1 to} Q ₄ in the inverter circuit 2 operating at a low frequency are used.
As a drive circuit of the pulse transformer PT, the primary side of the pulse transformer PT is excited by the drive switching elements Qa and Qb which are driven on / off at a high frequency of at least 1000 times the low frequency of the inverter circuit 2 and transmitted to the secondary side. high frequency and then rectified by the rectifier elements D ₁ to D _4, and supplies each of the switching elements Q ₁ to Q ₄ to be driven at a low frequency. If the time constant is set so that the polarity inversion switching element corresponding to the driving switching element operates at a high frequency during the period of operating at a high frequency, the low frequency will be reduced via the high frequency pulse transformer. It is possible to transmit a drive signal of a frequency, and thus a drive circuit can be inexpensively configured using a small pulse transformer.

[0006]

1 is a circuit diagram of a first embodiment of a power supply device of the present invention, and FIG. 2 is a circuit diagram of a drive circuit used in this embodiment. The circuit configuration will be described below. 1 is DC
The DC / DC converter includes a transformer T, a switching element Q ₀ , a diode D _0, and a smoothing capacitor C ₀ . A DC power source E is connected to the primary winding of the transformer T via a switching element Q ₀ . The DC power source E may be a battery or a rectified AC power source such as a commercial power source. A smoothing capacitor C ₀ is connected to the secondary winding of the transformer T via a diode D ₀ . Although a flyback converter is used in the embodiment, a forward type converter may be used without any particular limitation. Reference numeral 2 is an inverter circuit, and a load LP is formed by a full bridge circuit including switching elements Q _{1 to} Q _4.
The polarity of the voltage applied to is alternated at a low frequency.
The switching element Q ₁ to Q _4, using a voltage control type power element (e.g., MOSFET, MCT, etc.). Reference numeral 3 is a filter circuit, which cuts off high-frequency ripples contained in the voltage applied to the load LP.
This circuit may be omitted. Reference numeral 4 denotes an igniter circuit, which includes a pulse generator PG and a pulse transformer PTo. For example, when the load LP is a high pressure discharge lamp, a high voltage pulse is applied to start the load LP. LP is a load, and is composed of, for example, a high-pressure discharge lamp or a motor.

Next, the drive circuit shown in FIG.
Switching element Q in inverter circuit 2₁~ Q_FourTo
This is a circuit for driving at a low frequency. This drive circuit
The pulse transformer PT and the switching elements Qa, Qb,
Rectifying element D₁~ D_Four, Resistance R ₁~ R₈And DC power for driving
It consists of source Ed. In the primary winding of the pulse transformer PT,
A center tap is provided, and this center tap
Is connected to the positive electrode of the driving DC power source Ed. pulse
Both ends of the primary winding of the transformer PT are switched
Negative electrode of the driving DC power supply Ed via the switching elements Qa and Qb
It is connected to the. The pulse transformer PT is the first to the fourth
First to fourth rectifying elements each having a secondary winding
D₁~ D_FourIs connected. First rectifying element D₁By
The voltage rectified by half-wave is resistance R₁, R₂Is divided by
Switching element Q₁Gate voltage V₁Becomes Well
The second rectifying element D₂The voltage half-wave rectified by
Anti-R₃, R_FourIs divided by the switching element Q_Four
Gate voltage V_FourBecomes Where the first and second quadratic
The windings are wound so that they have the same polarity, and the gate voltage
V₁And V_FourHave the same waveform. Next, the third rectifying element D
₃Voltage half-wave rectified by the resistor R_Five, R₆By minutes
Pressed, switching element Q₂Gate voltage V₂Tona
It In addition, the fourth rectifying element D_FourHalf-wave rectified by
Pressure is resistance R₇, R₈Is divided by the switching element
Child Q₃Gate voltage V₃Becomes Where the third and fourth
The secondary winding has a polarity opposite to that of the first and second secondary windings.
It is wound on the sea and has a gate voltage V₂And V₃Is the gate voltage
V₁And V_FourThe waveform has a phase opposite to that of Each switch
Element Q₁~ Q_FourOf the gate capacitance Ci of the resistor R₂，
R_Four, R₆, R₈Are respectively connected in parallel.

The operation of this embodiment is shown in the time chart of FIG.
It demonstrates using. Switching elements Qa and Qb are several hundreds k
It is turned on / off at a high frequency of Hz and low frequency of several tens to several hundreds Hz.
The waves are modulated and switched. First, switchon
If the switching element Qa is on / off at high frequency,
The ching element Qb is off. At this time, the first and second
Rectifying element D₁, D₂Is conducting, switching element
Q₁, Q_FourGate voltage V ₁, V_FourIs below the threshold Vth
Boosted to the high level by the gate capacitance Ci
Holds the switching element Q₁, Q_FourIs on
It At this time, the switching element Q₂, Q₃Is off
It

Next, when the switching element Qa is off and the switching element Qb is also off, the charges accumulated in the gate capacitances Ci of the switching elements Q ₁ and Q ₄ are discharged by the discharge resistors R ₂ and R ₄ to generate the gate voltage. When V ₁ and V ₄ decrease and become lower than the threshold value Vth, the switching elements Q ₁ and Q ₄ are turned off.

Similarly, when the switching element Qb is on / off at a high frequency, the switching element Qa is off. The gate capacitance Ci of the switching elements Q ₂ and Q ₃
Is accumulated in the gate voltage, and the gate voltages V ₂ and V ₃ reach the threshold value V.
When the voltage is boosted above th, the switching elements Q ₂ , Q ₃
Turns on. Thereafter, the same operation is performed.

As described above, in the drive circuit for the power elements (switching elements Q _{1 to} Q ₄ ) of the inverter circuit, the drive power and the signal transmission are performed by one pulse transformer, and the pulse transformer is used by the inverter circuit. By driving at a frequency higher than the frequency, the pulse transformer can be easily miniaturized. Further, the circuit on the secondary side can be greatly simplified as compared with the conventional example. The power control to the load is performed by the switching element Q ₀ of the DC / DC converter 1.
Is PWM controlled to supply electric power according to the state of the load.

FIG. 4 is a circuit diagram of a second embodiment of the power supply device of the present invention.
5 is a circuit diagram of a drive circuit used in this embodiment.
Is. The circuit configuration will be described below. 1 is D
C / DC converter, forward converter
Yes, transformer T and switching element Q₀And diode
D₁₁, D₁₂, Inductor L₀And smoothing capacitor C ₀
Is equipped with a switching element Q₀PWM control of
Control the electric power supplied to the load LP. 2 is Inver
Switching circuit Q₁~ Q_FourConsists of
The bridge circuit reduces the polarity of the voltage applied to the load LP.
It is an alternating frequency. Switching element Q₁，
Q₃Is a voltage control type power element (MOSFET, MC
T etc.). Switching element Q₂, Q_FourIs MO
SFET, bipolar transistor, etc.
It is not limited to the voltage control type. High potential switching
Element Q₁, Q₃Is the gate voltage from the drive circuit shown in FIG.
V ₁, V₃Has been supplied. The configuration of the drive circuit is shown in Figure 2.
As described, the switching element Q₂, Q_Fourof
The circuit portion that creates the gate voltage is omitted. Low power
Switching element Q₂, Q_FourThe gate voltage of
Itching element Q₁Or Q₃When these conduct
Smoothing capacitor C via₀Supplied from Switch
Holding element Q_FourThe voltage across the₁₃And diode D
₁₃Through Zener diode ZD₁Applied to the
Nar diode ZD₁The voltage across both ends of the resistor R₁₁, R₁₂By
Is divided and the switching element Q₂The gate voltage of
It In addition, the switching element Q₂The voltage across the
₁₄And diode D₁₄Through Zener diode ZD₂
Applied to the Zener diode ZD₂The voltage across
Anti-R₁₅, R₁₆Is divided by the switching element Q_Four
Gate voltage.

The operation of this embodiment will be described with reference to the time chart of FIG. Switching elements Qa and Qb are several hundreds k
It is turned on / off at a high frequency of Hz, is modulated at a low frequency of several tens to several hundreds Hz, and is switched. First, when the switching element Qa is turned on / off at a high frequency, the switching element Qb is turned off. At this time, the rectifying element D ₁ of the drive circuit becomes conductive, current flows through the resistors R ₁ and R _2, and the gate voltage V ₁ of the switching element Q ₁ rises. When the gate voltages V ₁ exceeds the threshold Vth of the switching element Q _1, the switching element Q ₁ is turned on. As a result, a current flows from the capacitor C ₀ through the switching element Q ₁ , the resistor R ₁₄ , and the diode D _14, and the voltage across the Zener diode ZD ₂ rises.
This voltage is divided by the resistors R ₁₅ and R ₁₆ to charge the gate capacitance of the switching element Q ₄ and
₄ turns on.

Next, when the switching element Qa is off and the switching element Qb is off, the charge accumulated in the gate capacitance Ci of the switching element Q ₁ is discharged by the discharge resistor R _2.
Are discharged, the gate voltage V ₁ drops, and the switching element Q ₁ is turned off. As a result, the gate voltage of the switching element Q ₄ drops and the switching element Q ₄ is also turned off.

Next, the switching element Qb turns on at a high frequency.
ON / OFF and the switching element Qa is OFF
Is the rectifying element D of the drive circuit_FourConducts and the resistance R₇, R₈
Current flows to the switching element Q₃Gate voltage V
₃Rises. Gate voltage V ₃Is the switching element Q₃
Exceeds the threshold value Vth of the switching element Q₃But
It turns on. As a result, the capacitor C₀From
Holding element Q₃, Resistance R₁₃, Diode D₁₃Through electricity
Current flows, Zener diode ZD₁Voltage across
Rise. This voltage is applied to the resistor R₁₁, R₁₂Partial pressure with
Itching element Q₂Charge the gate capacity of
Element Q₂Turns on. Hereinafter, the same operation is performed.

FIG. 7 is a circuit diagram of a third embodiment of the power supply device of the present invention.
FIG. 8 is a circuit diagram of a drive circuit used in this embodiment.
Is. The circuit configuration will be described below. 1 is D
It is a C / DC converter, and switches T and
Element Q₀And rectifying element D_{twenty one}, D _{twenty two}Equipped with a switch
Element Q₀Power supply to the load LP by PWM control of
Force control. Switching element Q₀Is a bipolar
Anything, such as a transistor or MOSFET, is not particularly limited.
Absent. The transformer T has a center tap on the secondary side.
Rectifier element D_{twenty one}, D_{twenty two}Has opposite polarity
Connected by. 2 is an inverter circuit,
Holding element Q₁, Q₂Alternating on / off at low frequencies
Voltage polarity applied to the load LP by alternating
To alter the Switching element Q₁, Q₂
Is a voltage-controlled semiconductor switching device such as MOSFET
It is made of an element and is not particularly limited. Switching element
Q₁, Q₂The series circuit of is the output of the DC / DC converter 1.
It is connected to the force end. Switching element Q₁, Q₂of
Between the connection point and the center tap of the secondary winding of the transformer T
Is the same as when the capacitor C for high frequency bypass is connected.
Is connected to the load LP via the igniter 4.
The igniter 4 includes a pulse generator PG and a high voltage pulse transformer.
Equipped with a PTo, high pressure load LP consisting of a discharge lamp
Apply pulse to cause dielectric breakdown and transfer to main discharge
It is a starting circuit. The pulse generator PG is a high voltage pulse transformer.
High-voltage pulse transformer connected to the primary winding
The secondary winding of the resistance PTo is connected in series with the load LP.
A closed circuit with a capacitor C for high frequency bypass.
Is made. Capacitor C sends high voltage pulse at startup.
Acts as a bypass capacitor that bypasses the steady point
At the time of lighting, the current supplied from the DC / DC converter 1
To smooth and supply a low ripple current to the load LP
Acts as a smoothing capacitor.

Next, the drive circuit shown in FIG.
Switching element Q in inverter circuit 2₁, Q₂To
This is a circuit for driving at a low frequency. This drive circuit
The pulse transformer PT and the switching elements Qa, Qb,
Rectifying element D₁, D₃, Resistance R ₁, R₂, Resistance R_Five，
R₆, Zener diode ZD₁₁, ZD₁₂And direct drive
The current source Ed. The switching elements Qa and Qb are
It consists of bipolar transistor, MOSFET, etc.
Not limited to. The primary winding of the pulse transformer PT is
Center tap is provided, and this center tap
It is connected to the positive electrode of the driving DC power source Ed. Palust
Both ends of the primary winding of the lance PT are switched respectively.
To the negative electrode of the driving DC power source Ed via the elements Qa and Qb.
It is connected. The pulse transformer PT has two secondary windings
Rectifying element D₁And D₃Is connected
ing. Rectifying element D₁The voltage half-rectified by the resistor
R₁, R₂Is divided by the switching element Q₁of
Gate voltage V₁Becomes Zener diode ZD₁₁Is over
It is provided to prevent a large gate voltage. Well
Rectifier element D₃The voltage half-rectified by the resistor
R_Five, R₆Is divided by the switching element Q₂of
Gate voltage V₂Becomes Where the two secondary windings are
And the gate voltage V₁When
V₂Has an opposite phase waveform. Each switching element Q₁，
Q₂Of the gate capacitance Ci of the resistor R₂, R₆Each average
Column connected.

The operation of this embodiment will be described with reference to the time chart of FIG. The difference between this embodiment and the above-described first and second embodiments will be briefly described. It gives a section in which the switching elements Q ₁ and Q ₂ are simultaneously turned on and D
The point is that the C / DC converter 1 is driven so as to always secure a path for the current supplied thereto and prevent an excessive surge voltage from occurring in the secondary winding of the transformer T.

First, when the switching element Q ₁ is turned on and the switching element Q ₂ is turned off, the switching element Qa is caused to perform a switching operation to switch the switching element Qa.
The gate input capacitance Ci of ₁ is charged. As a result, the switching element Q ₁ is turned on. At this time, the switching element Qb is off.

Next, at the time of polarity reversal, that is, when both the switching elements Q ₁ and Q ₂ are turned on, the switching elements Qa and Qb are alternately turned on / off, and the gates of the switching elements Q ₁ and Q ₂ are turned on. The input capacitance Ci is charged together. At this time, unbalanced PWM control is performed to make the on-duty of the switching element Qb larger than the on-duty of the switching element Qa.

Next, when the switching element Q ₁ is turned off and the switching element Q ₂ is turned on, the switching element Qb is caused to perform a switching operation to switch the switching element Q.
The gate input capacitance Ci of ₂ is charged. As a result, the switching element Q ₂ is turned on. At this time, the switching element Qa is off.

Next, at the time of polarity reversal, that is, when the switching elements Q ₁ and Q ₂ are both turned on, as described above, the switching elements Qa and Qb are alternately turned on / off and the switching element Q ₁ is turned on / off. , Q ₂ gate input capacitance Ci
Charge together. However, unbalanced PWM control is performed to make the on-duty of the switching element Qa larger than the on-duty of the switching element Qb.

The switching elements Qa and Qb are turned on / off at a high frequency of several hundreds of kHz, and the switching element Qa
The alternating frequency of ₁ and Q ₂ is a low frequency of several tens to several hundreds Hz. Further, the switching element Q ₀ operates asynchronously with the switching elements Q ₁ and Q ₂ and the switching elements Qa and Qb, and although not shown in FIG. 7, a circuit for detecting a load current or a load voltage. The PWM control is performed according to the output of the above, and the discharge lamp, which is the load, is turned on.

A circuit example in which the drive circuit of the above-mentioned third embodiment is further simplified is shown in FIG. 10 as a fourth embodiment.
In this embodiment, the pulse transformer PT in the drive circuit of FIG. 8 described in the third embodiment is also used as the transformer T of the DC / DC converter, and the circuit configuration is suitable for further miniaturization. The configuration of this embodiment will be described below.
E is a DC power supply, which may be a battery or the like, or may be a rectified AC power supply such as a commercial power supply. The switching elements Qa and Qb are high frequency switching elements,
It is composed of a MOSFET, a bipolar transistor, etc., and is not particularly limited. T is a transformer, which supplies power to the drive circuit in addition to the primary windings N ₁ and N ₂ connected to the switching elements Qa and Qb and the secondary winding N ₃ for supplying power to the load circuit 5. It is provided with tertiary windings N ₄ and N ₅ for supply. The switching elements Q ₁ and Q ₂ are low-frequency switching elements and are preferably composed of voltage-controlled switching elements such as MOSFET, MCT, SIT, etc., but may be bipolar transistors and are not particularly limited. D ₂₁ and D ₂₂ are rectifying elements, which are diodes in this embodiment, but are synchronous rectifying MOSFETs.
But good. Further, D ₁ and D ₃ are rectifying elements, R ₁ and R ₂ ,
R ₅ and R ₆ are resistors, and ZD ₂₁ and ZD ₂₂ are zener diodes, which form a drive circuit. C ₀ is a smoothing capacitor that removes ripples to the load circuit 5.

FIG. 11 is a time chart for explaining the operation of the fourth embodiment. Hereinafter, using this time chart, the switching elements Q ₁ , Q ₂ and Q of FIG.
The operation of a and Qb will be described. Switching element Qa, Q
b switches at a high frequency of several kHz to several hundred kHz. By modulating the switching of the switching elements Qa, Qb at a low frequency, the switching elements Q ₁ , Q ₂
Controls the timing of low frequency polarity reversal by.

First, the switching element Qa is turned on at a high frequency.
ON / OFF and the switching element Qb is OFF
Will be described. When the switching element Qa is on
The third winding N of the transformer T_FiveFrom the rectifying element D₁,
Anti-R₁Through the switching element Q₁Input capacitance Ci of
When charged and the gate voltage is above the threshold, the switch
Element Q₁Turns on. Switching element Qa is on
Then, after storing energy in the transformer T, switch
And the secondary winding N of the transformer T is turned off. ₃Through
And discharge current. At this time, the secondary winding of the transformer T
N₃From the smoothing capacitor C₀And load circuit 5, adjustment
Flow element D_{twenty one}, Switching element Q₁The current through the path through
Flowing. At this time, the switching element Q₂Is off
It In this way, the switching element Qa turns on at high frequency.
Switching element Q₁Is low frequency
Is turned on, and switching elements Qa and Q₁Is low frequency
Work synchronously. Next, the switching element Qb
Switching element Qa is turned off by turning on / off at high frequency
And the switching element Q₂
Is on, switching element Q₁Turns off. That's all
As shown in the figure, the pulse transformer of the driving power supply is the main circuit transformer.
By also using as T, control of the drive circuit is also simplified.
be able to.

[0027]

According to the first aspect of the present invention, the drive circuit of the polarity reversing switching element in the polarity reversing circuit operating at a low frequency switches between two high frequencies modulated at a low frequency for polarity reversing. A switching element for driving,
A pulse transformer having a primary winding connected to a driving DC power source through the driving switching element and a number of secondary windings corresponding to the switching elements for polarity reversal, and a secondary winding of the pulse transformer. It is composed of a rectifying element connected to each line side, and the polarity reversing switching element corresponding to the driving switching element is maintained in the ON state while the driving switching element is operating at high frequency. Since the time constant of the drive circuit for the polarity reversing switching element is set, the drive signal for the polarity reversing switching element in the polarity reversing circuit operating at a low frequency can be transmitted by using the high frequency pulse transformer. As compared with the case where a low-frequency drive signal is transmitted by a transformer, the pulse transformer can be downsized. Further, by using the multi-output type pulse transformer, even if there are four switching elements for polarity reversal of the inverter circuit, only two switching elements on the primary side of the pulse transformer of the drive circuit are needed. Compared with a low-frequency signal transmission method using a photocoupler, there is an effect that the number of switching elements in the drive circuit can be reduced and the circuit configuration can be simplified.

According to the second aspect of the invention, the circuit configuration can be simplified by using the pulse transformer of the drive circuit also as the transformer of the DC voltage conversion circuit. As described above, by reducing the number of components of the drive circuit, the power supply device can be downsized and the cost can be reduced.
There is an effect that an inexpensive power supply device can be provided.

[Brief description of drawings]

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

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

FIG. 3 is a waveform diagram for explaining the operation of the first embodiment of the present invention.

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

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

FIG. 6 is a waveform diagram for explaining the operation of the second embodiment of the present invention.

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

FIG. 8 is a circuit diagram of a control circuit according to a third embodiment of the present invention.

FIG. 9 is a waveform diagram for explaining the operation of the third embodiment of the present invention.

FIG. 10 is a circuit diagram of a fourth embodiment of the present invention.

FIG. 11 is a waveform chart for explaining the operation of the fourth embodiment of the present invention.

[Explanation of symbols]

1 DC / DC converter 2 inverter 3 filter circuit 4 igniter circuit PT pulse transformer Q _{0 to} Q ₄ switching element Qa, Qb switching element D _{1 to} D ₄ rectifying element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Kambara 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (3)

[Claims] 1. A DC power supply, a DC voltage conversion circuit for switching the DC power supply at high frequency to control a voltage supplied to a load, and at least two polarity inversions of the output voltage of the DC voltage conversion circuit. In a power supply device composed of a polarity inversion circuit that alternates at a low frequency using a switching element for switching, and a load circuit connected to the output terminal of this polarity inversion circuit, the drive circuit of the switching element for polarity inversion has a polarity Two driving switching elements that switch at a high frequency modulated with a low frequency for inversion, a primary winding connected to a driving DC power source through the driving switching element, and a switching element for polarity reversal And a rectifying element connected to the secondary winding side of the pulse transformer, respectively. During the period when the drive switching element operates at high frequency, the time constant of the drive circuit of the polarity inversion switching element is set so that the polarity inversion switching element corresponding to the drive switching element maintains the ON state. A power supply device characterized by being set. 2. The DC voltage conversion circuit includes a transformer, which is also used as a pulse transformer of the drive circuit, and the primary winding of the transformer has a center tap,
2. The power supply device according to claim 1, further comprising two drive switching elements connected at both ends, the two drive switching elements switching at a high frequency for polarity reversal and modulated at a low frequency. 3. The power supply device according to claim 1, wherein the load includes a high-pressure discharge lamp.