JPS5831424A - Switching regulator - Google Patents

Abstract

PURPOSE:To reduce the dielectric strength load of transistors (TRs) for an inverter by reducing the voltage to be applied to TRs for an inverter in an auxiliary inverter circuit. CONSTITUTION:In an auxiliary inverter circuit 30 in a switching regulator circuit, the collector of a TRQ2 is connected to the DC low electric potential side, the emitter is connected to the emitter of a TRQ1 and the collector of the TRQ1 is connected to the DC high electric potential side through a coil L2 of a TRT3. The voltage divided by two resistors R4, R5 connected to the DC high potential side and the DC low potential side respectively is applied to the base of the TRQ2. Consequently the voltage to be applied between the emitter and collector of the TRQ1 is reduced by the emitter voltage of the TRQ1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching regulator, and more particularly to a switching regulator that reduces the withstand voltage burden of inverter transistors used in an auxiliary inverter circuit.

Generally, in a power supply device with a relatively large power capacity, 1
Various means have been proposed from the viewpoint of suppressing as much as possible the rush current that occurs when the power is turned on next time.

For example, one method is to not drive the inverter on the main output circuit side, which has a large output, when the primary power is first turned on, but instead drive the main output circuit with an auxiliary inverter, and after that drive, the main output circuit In this method, the inverter of the main output circuit is driven by the output of the main output circuit.

However, the voltage applied to the inverter transistor used for oscillation of the auxiliary inverter circuit is generally a DC high voltage obtained by direct full-wave rectification of the primary side AC power supply. It is required to have pressure resistance.

Furthermore, the primary AC power supply is 100V, such as in Japan and the United States.
In the case of a system, it is possible to use a transistor with a relatively low withstand voltage, but in a 200-inch power supply such as in Europe, a transistor with a high withstand voltage is required due to the withstand voltage requirement of the transistor, which increases the cost of the regulator. The drawback was that it was expensive.

The present invention has been made in view of the above circumstances, and regardless of whether the primary AC power supply voltage is 100V or 200V, the above-mentioned high voltage transistor is not required, and the same and extremely simple circuit can be used. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a switching regulator according to the present invention. In other words, this switching regulator uses a so-called line operation method in which the primary AC input is directly rectified to operate the circuit. As shown, the isolation transformer T1. The primary circuit r6 and the secondary circuit 20 are insulated and separated by 'Th and 'Ts.

1. After the input AC is full-wave rectified by a full-wave rectifier circuit DS consisting of a capacitor, a rectifying element, and a noise filter, it charges two capacitors CI and C2 connected in series with DS. 1 is a known inverter circuit. A high frequency current of about 25 KH2 is output from the inverter circuit 1, inputted to the main output circuit 2 via the transformer Tl, and converted into a DC output voltage by the main output circuit 2. Further, this DC output is led to the control circuit 3 via the diode D1, and the control pulse output from the control circuit 3 enters the transformer T2, and then passes through the transformer T2 to the inverter circuit 1.
will be driven. The control circuit 3 has a built-in driver circuit and a known IC element including a pulse oscillation circuit that compares the DC output with an internally provided reference voltage and determines the pulse width based on the comparison result.

Next, the configuration and operation of the auxiliary inverter circuit 30 will be explained.

First, the transformer T3 insulates and separates the primary circuit 1o and the secondary circuit as described above, and the primary winding is the coil L1.
, Ll, the secondary winding consists of coil L3.

One end of Ll is connected to the emitter of the inverter transistor Ql and the emitter of the series regulator transistor Q2, and the other end is connected to the cathode of the diode D2. On the other hand, one end of L2 is a transistor QI
The other end is connected to the collector of
A collector voltage is supplied to the transistor Ql.

As shown in the figure, Ll and Ll are connected in opposite phases to each other so that the inverter transistor QI can oscillate. Note that a series circuit of resistor R7 and capacitor C3 is connected in parallel to both ends of Ll, and a diode D4 is connected to both ends of Ll. and capacitor C7
series circuits are connected in parallel, and a resistor R8 is connected to both ends of the capacitor C7. Also Ll
A capacitor C4 and a resistor R1 are connected between the other end and the base of Ql.
are connected in series, a Zener diode ZD+ is connected between the anode of the diode D2 and the base of Q+, and a Zener diode ZD+ is connected between the anode of the diode D2 and the base of Q+.
A resistor R2 is connected between the emitters, and a capacitor C5 is connected between the anode of the diode D2 and the emitter of Q1.

Further, a resistor R3 is connected to the base of the transistor Q1 and the other end of the coil L2. On the other hand, the base of the series regulator transistor Q2 is connected to the connection point of two resistors R4 and R5 connected in parallel to the full-wave rectifier output circuit, and the collector of Q2 is connected to the low potential side of the full-wave rectifier circuit DS. has been done.

Also, a resistor R is connected between the base and collector of transistor Q3.
6, a series circuit of capacitor C6 and Zener diode 2D2 are connected in parallel, the collector of Q3 is connected to the cathode of diode D3, and the anode of DS is connected to coil L.
Connected to one end of 3. Further, the emitter of Q3 is connected to the primary coil side of the transformer T2.

However, in this auxiliary inverter circuit, immediately after power is turned on, the oscillation transistor Q oscillates instead of the control circuit 3.
This circuit aims to separately excite the inverter circuit with its oscillation output, and also to provide the switching regulator with a relatively tJJ capacity DC power supply that does not require strict control. be.

That is, immediately after the power is turned on, the voltage smoothed by CI and C2 reaches a value of about 8096, and then the transistor Q1 of the auxiliary inverter circuit starts oscillating. Note that the oscillation frequency in this case is 25KH2 to 3QKH2, which is determined mainly by L, C4, Rs, etc. of the transformer T3.

When Ql starts to oscillate, a high frequency voltage of the above frequency is generated in the coil L2 of the transformer T3, and this high frequency voltage is transmitted to the coil L3 via the transformer. Note that the diode D4, capacitor C7, resistor R8, R7, and C3 connected to the coil L2 form a so-called snubber circuit, and have the role of absorbing the spike voltage generated across R2. Further, the Zener diode ZD+ is used to control on/off of Ql and stabilize the output. The high frequency voltage transmitted to the coil I, 81 is smoothed into direct current by D3 and C6, and stabilized by transistor Q3. However, in the switching regulator circuit of the present invention, the collector of transistor Q2 is connected to the DC low potential side as described above,
The emitter is connected to the emitter of the transistor Ql, and its collector is connected to the coil L! of the transformer T3. Connected to the DC high potential side via. The base of C2 is connected to the DC high potential side and the DC low potential side.
A voltage divided by the resistors R4 and Rs is applied. Therefore, a voltage equal to the road distribution voltage is applied to the output side, that is, the emitter, of transistor Q2, so the voltage applied between the main emitter and collector of inverter transistor Q is reduced by the emitter voltage of Ql.

Q, in other words, may have a small emitter and collector breakdown voltage Vceo, and is therefore very advantageous in terms of the insulation breakdown voltage of the transformer. Furthermore, even when the primary power supply voltage is 100 V or 200 V, there is a distinct advantage that the same circuit configuration can be used regardless of whether resistors R4, R6, and C2 are used.

As another embodiment, by using a Zener diode instead of the resistor R4, the same effect as above can be obtained, and at the same time, the voltage applied to a part of the inverter can be stabilized, and the cathode voltage of the diode D3 can be made constant. , it is possible to use this cathode voltage as a constant voltage power source.

As described above, the present invention can be summarized by connecting an inverter transistor, a transistor Q1, and a series regulator transistor Qf in series between a DC high potential and a DC low potential, and connecting the primary side DC voltage to two series resistors. (or one resistor and one Zener diode), and the divided voltage is applied to the base of the series regulator transistor, so the voltage is applied to the inverter transistor. It is possible to obtain a switching regulator equipped with an auxiliary inverter circuit having a shallow voltage, and having the same circuit configuration with or without a bias circuit, regardless of whether the AC power supply is 100V or 200V.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention. Patent applicant Koji Onishi, patent attorney representing Tabuchi Electric Co., Ltd.

Claims (2)

[Claims] (1) Connect an inverter transistor and a series regulator transistor in series between a DC high potential and a DC low potential, divide the primary DC voltage with two series resistors, and apply the divided voltage to the series regulator. A switching regulator comprising: an auxiliary inverter circuit that reduces the voltage applied to the inverter transistor by applying the voltage to the base of the regulator transistor. (2) An inverter transistor and a series regulator transistor are connected in series between a DC high potential and a DC low potential, and the primary DC voltage is divided by a resistor and a Zener diode, and the divided voltage is applied to the series regulator. A switching regulator comprising: an auxiliary inverter circuit that reduces the voltage applied to the inverter transistor by applying it to the base of the inverter transistor.