JPS644312Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a power supply device used, for example, as a discharge lamp device.

[Technical background of the invention and its problems]

BACKGROUND ART Conventionally, power supply devices such as discharge lamp lighting devices using a blocking type single-stone self-excited inverter are known in the following forms, for example. That is, after rectifying a low-frequency AC power source, it is converted into a high-frequency current by a blocking type single-stone self-excited inverter having a transistor for turning on and off the DC current and an output transformer, which is then used to light the discharge lamp. Therefore, it is possible to efficiently light a discharge lamp at high frequency with a small size.

However, in this type of power supply device, the turn-off characteristics of the transistor are poor, so the subsequent turn-off time is delayed, and the oscillation frequency of the inverter cannot be increased.

Therefore, in order to eliminate this drawback, it is possible to insert an inductor to improve the turn-off characteristics in the base of the transistor, or to insert an inductor to improve the turn-off characteristics and to provide a transistor to shorten the reset time of the transistor. ,
Various improvements have been attempted.

However, in the case of the former power supply device, although the turn-off characteristics of the transistor are improved,
There is a possibility that the transistor may become insufficiently driven and exhibit unstable oscillation. In addition, although the latter power supply device can eliminate the drawbacks of the former, it requires a transistor to shorten the reset time and a drive circuit to drive it at a predetermined timing, so the circuit components are large. The disadvantage is that there are too many.

[Purpose of invention]

The present invention has been made in order to eliminate the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide a power supply device with a simple structure and excellent switching characteristics.

[Summary of the idea]

In order to achieve the above object, the present invention includes a transistor, and a feedback winding provided between the base and emitter of the transistor to generate a voltage based on whether the transistor is turned on or off to control the transistor by positive feedback; A series resonant circuit of a capacitor and an inductor is provided between the feedback winding and the base of the transistor, and a series resonant circuit of a capacitor and an inductor is connected in parallel between the base and emitter of the transistor, and after the transistor is turned off by the resonant circuit, the capacitor is turned off. The present invention is characterized by comprising a constant voltage element that discharges the charged charge to the inductor.

[Example of idea]

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a circuit diagram of a power supply device previously proposed by the applicant. In the figure, 1 is a full-wave rectifier circuit, which converts an AC power source such as a commercial power source into a DC voltage, and then converts it into an L-type low-pass (high-frequency blocking) filter consisting of an inductor 2 and a capacitor 3, and a power storage capacitor. The DC voltage is applied to a single-stone transistor inverter 6 via a power storage means consisting of an isolation diode 5 and an isolation diode 5. here,
The rectified output has its high frequency component removed by a capacitor 3 and is applied to a capacitor 4. The capacitor 4 stores power from the L-type filter via the inverter 6, and supplies power to the inverter 6 while the output of the L-type filter is lower than a predetermined voltage. The inverter 6 also includes an output transformer 7, an output transistor that switches the primary winding ₇₁ current of the output transformer 7 at high frequency,
A drive circuit 9 for driving this transistor 8 is provided. The drive circuit 9 includes a drive capacitor 10 connected between the base winding (feedback winding) ₇₃ of the output transformer 7 and the base side of the transistor 8, and a capacitor 10 connected between the base and emitter of the transistor 8. It is composed of a series circuit of a resistor 11 and a diode 12 for discharging the charged charge. In this drive circuit 9, the electromotive force induced in the base winding ₇₃ of the output transformer 7 is fed back to the base of the transistor 8 via the capacitor 10 to turn the transistor 8 on and off at high frequency, and the waveform shaping capacitor A high frequency voltage is applied to a load 100 such as a discharge lamp through a resonant circuit constituted by a primary winding 7 ₁ and a secondary winding 7 ₂ .
In FIG. 1, an inductor 14 connected in series with the capacitor 4 limits the charging current of the capacitor 4 flowing through the capacitor 4 and the diode 15 to adjust the power stored in the capacitor 4. Further, a bias resistor 16 is connected between the (+) side of the capacitor 4 and the base side of the transistor 8, and a diode 17 is connected in the forward direction to the emitter of the transistor 8, so that a reverse voltage between the emitter and base of the transistor is connected. protect

For the power supply device configured as above,
When an AC voltage Vin is input, this AC voltage Vin is full-wave rectified by a full-wave rectifier circuit 1 and is applied to an L-type filter and a power storage means. The power storage capacitor 4 is charged in a predetermined direction by a current flowing in a closed loop of the rectifier circuit 1 → L-type filter → capacitor 4 → inductor 14 → diode 15 → transistor 8 every time the transistor 8 of the inverter 6 is turned on. The capacitor 4 is discharged via the isolation diode 5 when the rectified output given through the L-type filter becomes less than a predetermined voltage (that is, the charging voltage of the capacitor 4) every half cycle, and this discharge output is sent to the inverter 6. give. When the voltage across the power storage means is applied to the inverter 6, the base potential of the transistor 8 increases due to the current flowing in the closed loop of the resistor 16 → capacitor 10 → base winding ₇₃ , and the base current flows through the transistor 8. It flows and turns on. When the transistor 8 is turned on, a collector current flows, which is induced in the primary winding 7 ₁ to generate an electromotive force in the direction of the solid arrow in the base winding 7 ₃ , which charges the capacitor 10 . Then, transistor 8 is reverse biased and turned off, and
The charge in the capacitor 10 flows through the resistor 11 and the diode 12, and the capacitor 10 is reset. In this way, the transistor 8 is turned on and off, and the load 10 is passed through the output transformer 7.
A high frequency voltage Vout is applied to Vout.

In such a power supply device, since the rectifier circuit 1 is non-smooth, the input power factor is high, and in an area where the output voltage of the rectifier circuit 1 is lower than a predetermined voltage, DC voltage is supplied from the power storage capacitor 4 to the inverter 6. Therefore, even though a non-smooth current output is used, there is no rest period and a high frequency output with little ripple is generated. In addition, the power storage means and the inverter 6
Since the rectified output is supplied through an L-type filter, the load 100
When the terminal voltage of the capacitor 4 is low when dimming the discharge lamp, the primary winding 7 ₁
Also, the rush current flowing to the collector of the transistor 8 can be reduced. That is, since the current to the capacitor 4 is mainly supplied from the capacitor 3, even if an inrush current attempts to flow into the capacitor 4 at startup, for example, the voltage across the capacitor 3 decreases, thereby suppressing the inrush current. Therefore, the output transistor 8 with a small rated current can be used. Furthermore, since the high frequency component of the input current of the power supply device is removed by the L-type filter, there is an advantage that the high frequency current flowing to the capacitor 4 can be prevented from having an adverse effect on the AC power supply, and the input power factor of the power supply device is also improved. Therefore, if a discharge lamp is lit using the high frequency output of this power supply device, it will be lit with good luminous efficiency, and by rectifying the high frequency output, it will be possible to obtain a DC output with less ripple.

However, in the power supply device described above, the transistor 8 is turned off by applying a reverse bias to the transistor 8 using the charge stored in the capacitor 10, so that the turn-off characteristic of the transistor 8 is poor. Therefore, an inductor 18 is inserted into the base of the transistor 8. In this case, when the transistor 8 is turned on, a base current flows through the transistor 8 in the direction opposite to the forward bias due to the resonance of the inductor 18 and the capacitor 10, and the transistor 8 is turned off.
The turn-off characteristics of However, the charge stored in the capacitor 10 is transferred to the resistor 11 and the diode 12.
Since the capacitor 10 is immediately discharged through the capacitor 10, the charge in the capacitor 10 cannot be reset sufficiently, and the transistor 8 may become insufficiently driven and exhibit unstable oscillation.

Therefore, as shown in FIG. 2, a constant voltage element 20 is connected in series with the resistor 11 and diode 12. Here, the breakdown voltage of the constant voltage element 20 is selected so that it becomes conductive after the reverse bias voltage is applied to the transistor 8 and the transistor 8 is turned on.

In the power supply device configured as described above, when the AC voltage Vin is input, the transistor 8 is turned on, and the capacitor 13 and the primary winding 7 are thereby turned on.
A collector current flows between the resonant circuit ₁ and the emitter and collector of the transistor 8. Then, an electromotive force is induced in the base winding ₇₃ in the direction of the solid arrow in FIG. 2, and the capacitor 10 is charged by this electromotive force. Then, due to the resonance of the inductor 18 and the capacitor 10, a base current in the direction opposite to the forward bias flows through the transistor 8 through the diode 17, turning the transistor 8 off, and then the charge in the capacitor 10 is transferred to the base winding 7 ₃ → Resistor 11 → Diode 12 → Constant voltage element 20 → Inductor 18 is discharged and reset. In this way, since the transistor 8 is turned off by the resonance of the inductor 18 and the capacitor 10, the turn-off time is shortened and the capacitor 10 is turned off after the transistor 8 is turned off.
Since the charge charged in the capacitor 10 is rapidly discharged through the resistor 11, the diode 12, and the voltage element 20, the charge charged in the capacitor 10 can be reset accurately, thereby eliminating unstable oscillations caused by insufficient drive of the transistor 8. It is possible to perform an oscillation operation that is stable and has excellent turn-off and turn-off characteristics. Moreover, since it is only necessary to insert the constant voltage element 20 into the discharge loop of the capacitor 10, the circuit configuration becomes simple.

[Effect of idea]

As explained above, according to the present invention, the constant voltage element connected in parallel between the base and emitter of the transistor discharges the charge in the drive capacitor after the transistor is turned off. It is quickly reset during the off-period of the circuit, improving switching characteristics, and since it has a simple circuit configuration using constant voltage elements, it is possible to reduce the cost by reducing the number of circuit components.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram for explaining a power supply device of the present invention, and FIG. 2 is a circuit diagram of a power supply device according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Rectifier circuit, 6... Inverter, 7... Output transformer, 7 ₁ ... Primary winding, 7 ₂ ... Secondary winding, 7 ₃ ... Base winding (feedback winding), 8... ...transistor, 9...drive circuit, 10...drive capacitor, 11...resistor, 12...diode, 18...inductor, 20...constant voltage element.

Claims (1)

[Scope of utility model registration request] transistor and the base of this transistor
a feedback winding provided between the emitters and controlling the transistor by positive feedback by generating a voltage based on whether the transistor is turned on or off; and a capacitor and an inductor provided between the feedback winding and the base of the transistor. The device is characterized by comprising a series resonant circuit and a constant voltage element that is connected in parallel between the base and emitter of the transistor and discharges the charge in the capacitor to the inductor after the transistor is turned off by the resonant circuit. power supply.