JPH06276736A - Reverse-current preventive circuit of universal power supply device - Google Patents

Abstract

PURPOSE:To obtain a reverse-current preventive function under the state of the shutdown of a power supply circuit and the flowing function of main current under the state of the operation of the power supply circuit by composing a reverse-current preventive circuit of a transistor switch brought to an on state when the power supply circuit on the side, to which the transistor switch belongs, is operated. CONSTITUTION:The capacitor 82 of a delay timer switch 8 is not charged and a transistor switch 85 keeps an off state under the stopped state of a DC power supply circuit 2, a semiconductor switch 7 is turned off, the MOSFET 61 of a reverse-current preventive circuit 6 is brought to an off state, and reverse current to the DC power supply circuit 2 are obstructed. The MOSFET 61 is brought to a conductive state under the operated state of the DC power supply circuit 2, but the title reverse-current preventive circuit can be miniaturized because the loss of the conductive state is reduced. When the DC power supply circuit 2 is turned o erroneously during the operation of an AC power circuit, on the other hand, the MOSFET 61 is maintained under an off state by the delay timer switch 8 during discharge time of the stored charges of a capacitor 13B and the inflow of reverse current to the DC power supply circuit 2 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is generated by sharing a switching transformer in an AC / DC power supply device capable of generating DC power by arbitrarily selecting a commercial frequency AC power supply and a vehicle DC power supply. The present invention relates to a backflow prevention circuit that blocks a backflow of current.

[0002]

2. Description of the Related Art FIG. 2 is a connection diagram showing a conventional AC / DC dual-purpose power supply device. The AC / DC dual-purpose power supply device includes an AC power supply circuit side winding 5AC, a DC power supply circuit side winding 5DC, and an output circuit side winding. An insulation type switching transformer 5 having 5OUT,
Rectifying / smoothing circuit 3 including output circuit side winding 5OUT, half-wave rectifying circuit 33A and smoothing capacitor 33B connected to this
Output circuit 3 having 3. A first switching circuit 14 including a transistor switch 14A and a drive circuit 14B for the transistor switch 14A is provided between the rectifying / smoothing circuit 13 including the rectifying bridge 13A and the smoothing capacitor 13B connected to the AC power supply 11 and the AC power supply circuit side winding 5AC. AC power supply circuit 1 which has. A DC power supply circuit having a second switching circuit 24 composed of a transistor switch 24A and a driving circuit 24B between the smoothing circuit 23 connected to the DC power supply 21 such as a vehicle battery and the DC power supply circuit side winding 5DC. 2. Is provided as a main circuit. Further, the AC power supply circuit 1 and the DC power supply circuit 2 are provided with diodes 16 and 25 as a backflow prevention circuit in series with the windings, and the windings on the side of the power supply circuit operating by the electromagnetic induction action of the switching transformer 5. Is induced in the winding on the side of the power supply circuit that has stopped operating, and the current is prevented from flowing back to the stopped power supply circuit due to this induced voltage. The AC power supply circuit 1 includes a snubber circuit 15 including a diode 15A, a resistor 15B and a capacitor 15C.

When the AC power supply circuit 1 of the AC / DC dual-purpose power supply device configured as described above is connected to the AC power supply 11, the first switching circuit 14 performs a switching operation at a high frequency of several tens to several hundreds of kHz. , Functions as an AC / DC converter that supplies the DC power generated through the rectifying / smoothing circuit 33 of the output circuit 3 to the load 39, and outputs the output voltage through the feedback circuit 30 to the drive circuit 14.
By returning to A, the output power is controlled to a constant voltage. When the operation of the AC power supply circuit 1 is stopped and the DC power supply 21 is connected to the DC power supply circuit 2, the second switching circuit 24 performs the switching operation in the order of several tens to several hundreds of KHz, and the output circuit 3 A function as a DC / DC converter that supplies DC power to the load 39 via the rectifying / smoothing circuit 33 can be obtained.

On the other hand, in order to prevent the AC power supply circuit 1 and the DC power supply circuit 2 from operating simultaneously by mistake, a DC priority circuit 4 is provided between both power supply circuits. DC priority circuit 4
Is a transistor switch 42 connected to the DC power supply circuit side, and converts the voltage of the AC power supply 11 into a direct current through an insulating transformer 47 and rectifying / smoothing circuits 45 and 46, and applies it to a series circuit of a relay 48 and a transistor switch 44. And the resistors 43A and 4A when the AC power supply circuit operates.
Transistor switch 4 by the voltage divided by 3B
4 is turned on to excite the relay 48, and the relay contact 49 serially connected to the AC power supply circuit 1 is closed to apply the AC power supply voltage to the AC power supply circuit 1. When the voltage of the DC power supply 21 is applied to the DC power supply circuit 2 in this state, the transistor switch 42 is turned on by the voltage of the DC power supply 21 divided by the resistors 41A and 41B, and the transistor switch 44 is forcibly turned off. Therefore, the relay contact 49 is opened, and the AC power supply circuit 1 is forcibly opened to exert the function as the DC priority circuit 4 that gives priority to the operation of the DC power supply circuit 2, and both power supply circuits operate simultaneously. It is possible to reliably avoid the occurrence of the situation.

[0005]

In the AC / DC bidirectional power supply device in which the function of the AC / DC converter and the function of the DC / DC converter are shared by sharing the switching transformer 5 and the output circuit 3, the AC power supply is used. Diodes 16 and 25 as a backflow prevention circuit were provided in series with the windings in the circuit 1 and the DC power supply circuit 2, and the operation was stopped from the windings on the power supply circuit side operating by the electromagnetic induction action of the switching transformer 5. Voltage is induced in the winding on the power circuit side,
It is configured to prevent current from flowing back to the power supply circuit stopped by this induced voltage. However, since the backflow prevention diode of the operating power supply circuit is also the path of the main current, a loss occurs due to its forward voltage drop. In particular, in a DC power supply circuit having a lower voltage and a larger current than an AC power supply circuit, the loss generated in the backflow prevention diode is large, for example, the forward voltage drop is small and the reverse voltage recovery time is short. Even if SBD) is used, there is a problem that a loss that causes a decrease in power supply efficiency occurs and a cooling fin for preventing a temperature rise of the diode becomes large, which causes an increase in size of the device.

SUMMARY OF THE INVENTION An object of the present invention is to obtain an AC / DC dual-use type power supply device having a small generation loss, a small size, and a backflow prevention circuit having an excellent backflow prevention function against an erroneous operation such as simultaneous turning on of both AC / DC power supplies.

[0007]

In order to solve the above problems, according to the present invention, an insulation type switching transformer having an AC power supply circuit side winding, a DC power supply circuit side winding, and an output circuit side winding. And an output circuit having a rectifying and smoothing circuit connected to the output circuit side winding, and an AC power supply circuit having a first switching circuit between the rectifying and smoothing circuit connected to the AC power supply and the AC power supply circuit side winding. And a DC / DC power supply device having a smoothing circuit connected to a DC power supply and a DC power supply circuit having a second switching circuit between the windings on the DC power supply circuit side. Transistors that have a backflow prevention circuit that prevents the backflow of current due to winding induced voltage when the operation is stopped.The backflow prevention circuit is turned on when the power supply circuit to which it belongs operates. It is assumed that a switch.

Further, it is assumed that the drive terminal of the transistor switch is connected to the output circuit side winding or the auxiliary winding of the switching transformer through the semiconductor switch. Further, it is assumed that the transistor switch includes a delay timer switch between the power supply circuit to which it belongs and the semiconductor switch. Furthermore, the delay timer-switch has a time exceeding the operating time due to the discharge of the accumulated charge of the rectifying / smoothing circuit of the power supply circuit on the side not belonging thereto,
The delay time shall be included.

On the other hand, it is assumed that the AC / DC power supply device is provided with a DC priority circuit between the AC power supply circuit and the DC power supply circuit for giving priority to the operation of the DC power supply circuit.

[0010]

In the present invention, since the backflow prevention circuit is constituted by the transistor switch which is turned on when the power supply circuit to which the backflow prevention circuit belongs operates, the power supply circuit to which the backflow prevention circuit belongs does not operate. The backflow prevention function can be obtained by turning off the transistor switch, and the main current flow function can be obtained by turning on the transistor switch while the associated power supply circuit is operating. By utilizing the forward voltage drop lower than the diode of the effect transistor (FET), the low generated loss accompanying it, and its low temperature dependence, it is possible to obtain a backflow prevention circuit which is small in size with low loss. . Also, when an FET is used in the backflow prevention circuit, its built-in diode can be used as a main current path in the off state, and at the same time a backflow prevention function can be obtained. It is possible to configure a safety improving device against erroneous operation such as.

Further, if the drive terminal of the transistor switch is configured to be connected to the output circuit side winding or the auxiliary winding of the switching transformer via the semiconductor switch, the transistor switch can be stabilized without requiring a special additional power source. The function to operate is obtained. Further, the transistor switch is provided with a delay timer switch between the power supply circuit to which it belongs and the semiconductor switch, and the time exceeding the operating time due to discharge of accumulated charge of the rectifying and smoothing circuit of the power supply circuit to which it does not belong. , Is used as the delay time of the delay timer, the built-in diode can be used as a main current path in the off state, and at the same time, the reverse current preventing function can be obtained. It becomes possible to use it. For example, if the AC power supply circuit mistakenly utilizes the DC power supply circuit during operation, the operation of the DC priority circuit automatically switches to the DC power supply circuit, but the operation is accumulated in the rectifying and smoothing circuit of the AC power supply circuit. Due to the discharge of the electric charges, the AC / DC power supply circuits are simultaneously operated for a while. At this time, if the delay time of the delay timer-switch is set longer than the operating time of the AC power supply circuit due to the discharge of the accumulated charge, the FET is kept in the OFF state during that time, and its built-in diode serves as the main current path. The DC power supply circuit operates normally, and the function of blocking the flow of reverse current to surely avoid the generation of reverse current due to erroneous operation can be obtained.

On the other hand, if the AC / DC power supply device is provided with a DC priority circuit that prioritizes the operation of the DC power supply circuit between the AC power supply circuit and the DC power supply circuit, the reverse current caused by the erroneous operation is generated. And a function of preserving the operation of the DC power supply circuit with priority by compensating for the weak point of the FET that does not have the backflow prevention function in the ON state.

[0013]

EXAMPLES The present invention will be described below based on examples. FIG. 1 is a connection diagram showing an example in which a backflow prevention circuit of an AC / DC dual-purpose power supply device according to an embodiment of the present invention is provided on the DC power supply circuit side, and the same components as those of the prior art are designated by the same reference numerals. Therefore, duplicate description will be omitted. In the figure, the DC power supply circuit 2 is a DC power supply circuit side winding 5DC
MOSFET with drain and source side connected in series to
A backflow prevention circuit 6 using 61 as a transistor switch is provided, and a bias resistor 63 is provided between the gate of the MOSFET 61 and the DC power supply circuit, a bypass capacitor 62 for preventing malfunction, and overvoltage protection. The Zener diode 64 is connected, and its gate is a transistor switch 71, a diode 72, and a resistor 7.
It is connected to the output circuit 33 via the semiconductor switch 7 including 3,74,75.

Further, 8 is a delay timer-switch,
A CR delay timer including a series circuit of a resistor 81 and a capacitor 82 connected in parallel to the DC power supply circuit 2, a series circuit of a Zener diode 83 and a resistor 84 connected in parallel to the capacitor 82, and a bias of the resistor 84. Resistance,
The collector side is composed of a transistor switch 85 connected to the semiconductor switch 7 and a diode 86 forming a discharging circuit of the capacitor 82. The backflow prevention circuit 6 may be provided between the second switching circuit 24 and the DC power supply circuit side winding 5DC.

As described above, in the AC / DC power supply device including the backflow prevention circuit 6 having the semiconductor switch 7 and the delay timer-switch 8, the AC power supply circuit 1 operates and the DC power supply circuit 2 is stopped. , The first switching circuit 14 operates to generate constant-voltage-controlled output power in the output circuit 3, which is supplied to the load 39,
A voltage is induced in the DC power supply circuit side winding 5DC of the switching transformer 5. At this time, since the DC power supply circuit 2 has stopped operating, the delay timer-capacitor 8 of the switch 8 is
2 is uncharged and the transistor switch 85 remains off, so that the semiconductor switch 7 is turned off and the MOSF is turned off.
Since the ET 61 is turned off, the backflow prevention circuit 6 exerts its backflow prevention function and prevents a reverse current from flowing in the DC power supply circuit 2 due to the induced voltage of the DC power supply circuit side winding 5DC.

At the time when the AC power supply circuit 1 is stopped and the DC power supply circuit 2 starts operating, first, the DC power supply circuit side winding 5DC is charged through the built-in diode 61D of the MOSFET 61 as a backflow prevention circuit. A current flows, whereby the second switching circuit 24 operates and the output circuit 3
Is supplied to the load 39, and the output voltage of the output circuit 3 is applied to the transistor 71 of the semiconductor switch 6 via the diode 72. In parallel with this, a delay timer-a capacitor via a resistor 81 of the switch 8-
When the charging of 82 is started and the charging voltage exceeds the Zener voltage of the Zener diode 83, the transistor switch 85 is turned on, and accordingly, the transistor 71 is turned on to drive the gate of the MOSFET 61. When the voltage is applied, the backflow prevention circuit 6 becomes conductive, and the current of the DC power supply circuit side winding 5DC moves from the built-in diode 61D to the source and drain of the MOSFET.
At this time, the forward voltage drop of the MOSFET is lower than that of the Schottky barrier diode (SBD), and the generated loss can be reduced. Therefore, not only the conversion efficiency of the AC / DC dual power supply device can be improved, but also the Schottky The barrier diode (SBD) has a large leakage current at high temperature, whereas the MOSFET has a small leakage current and a small loss. Therefore, the cooling fin can be downsized, and the backflow prevention circuit can be downsized.

On the other hand, if the DC power supply circuit 2 is mistakenly utilized while the AC power supply circuit 1 is operating, the DC priority circuit 4
The operation automatically switches to the DC power supply circuit 2, but the AC / DC power supply circuit 1 simultaneously operates for a while due to the discharge of the charge accumulated in the capacitor 13B of the rectifying / smoothing circuit 13 on the AC power supply circuit side. It will be. At this time, if the delay time of the delay timer switch 8 is set longer than the operation time of the AC power supply circuit due to the discharge of the accumulated charge, the MOSFET 61 of the backflow prevention circuit 6 maintains the OFF state during that time, and the built-in diode thereof is maintained. The DC power supply circuit 2 operates normally with 61D as the main current path, and the reverse current flowing through the DC power supply circuit can be blocked by the induced voltage from the AC power supply circuit side. To further ensure the backflow prevention function of the prevention circuit 6,
The effect of increasing the reliability of the backflow prevention circuit is obtained.

[0018]

As described above, according to the present invention, the backflow prevention circuit is formed by using the transistor switch, for example, the field effect transistor, which is turned on when the power supply circuit to which it belongs is operated. As a result, compared to the diode of the field-effect transistor, the forward voltage drop is low, the resulting loss is low, and its low temperature dependence is utilized. A dual-purpose power supply device can be provided.

If the transistor switch is driven by the output circuit voltage and the direct current priority circuit and the delay timer switch are added, the switching operation error of the AC / DC power supply circuit can be made without the need for a special drive power supply. Since the function of blocking the reverse current generated by
The advantage of being able to provide an AC / DC bidirectional power supply device with a more reliable backflow prevention circuit is obtained.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an example in which a backflow prevention circuit of an AC / DC dual-purpose power supply according to an embodiment of the present invention is provided on a DC power supply circuit side.

FIG. 2 is a connection diagram showing a conventional AC / DC power supply device.

[Explanation of symbols]

 1 AC power supply circuit 2 DC power supply circuit 3 Output circuit 4 DC priority circuit 5 Isolation type switching transformer 5AC AC power supply circuit side winding 5DC DC power supply circuit side winding 5OUT Output circuit side winding 6 Backflow prevention circuit 7 Semiconductor switch 8 Delay timer -Switch 11 AC power supply 13 Rectifying and smoothing circuit 14 First switching circuit 15 Snubber circuit 16 Backflow prevention diode 21 DC power supply 23 Smoothing circuit 24 Second switching circuit 25 Backflow prevention diode 33 Rectification and smoothing circuit 39 Load 48 Relay -49 Relay contact 61 Transistor switch (MOSFET) 61D Built-in diode 71 Transistor switch 72 Diode 81 Charging resistor 82 Capacitor 83 Zener diode 85 Transistor switch 86 Discharge diode

Claims (5)

[Claims] 1. An insulating switching transformer having an AC power supply circuit side winding, a DC power supply circuit side winding, and an output circuit side winding, and an output circuit having a rectifying / smoothing circuit connected to the output circuit side winding. An AC power supply circuit having a first switching circuit between a rectifying and smoothing circuit connected to an AC power supply and an AC power supply circuit side winding; a smoothing circuit connected to a DC power supply and a DC power supply circuit side winding; An AC / DC dual-purpose power supply device including a DC power supply circuit having a second switching circuit between the DC power supply circuit and the DC power supply circuit includes a backflow prevention circuit for preventing backflow of current due to winding induced voltage when the AC power supply circuit or the DC power supply circuit stops operating. In the equipped one, the backflow prevention circuit
A backflow prevention circuit for an AC / DC bidirectional power supply device, comprising a transistor switch that is turned on when the power supply circuit to which it belongs is activated. 2. The alternating-current / direct-current type power supply device according to claim 1, wherein the drive terminal of the transistor switch is connected to the output circuit side winding or the auxiliary winding of the switching transformer through a semiconductor switch. Backflow prevention circuit. 3. The dual-mode power supply device according to claim 1, wherein the transistor switch is provided with a delay timer switch between the power supply circuit to which it belongs and the semiconductor switch. Backflow prevention circuit. 4. The delay timer switch has, as its delay time, a time that exceeds an operation time due to discharge of accumulated charges of a rectifying / smoothing circuit of a power supply circuit to which the delay timer does not belong. A backflow prevention circuit for an AC / DC power supply device according to Item 3. 5. The AC / DC power supply device according to claim 1, wherein the AC / DC power supply device includes a DC priority circuit between the AC power supply circuit and the DC power supply circuit for giving priority to the operation of the DC power supply circuit. Backflow prevention circuit of power supply unit.