JPH05300738A - Dc power-supply apparatus - Google Patents

Abstract

PURPOSE:To obtain the DC power supply apparatus of small size and high reliability, in which each output voltage can be controlled without requiring an element increasing a loss and the whole heat generation is reduced, in a DC power supply apparatus used as the power supply of various electronic equipments. CONSTITUTION:The series circuit of a switching element 22 and the primary winding N1 of a transformer 23 is connected with a DC power supply 21, a master output circuit composed of the rectifier and smoothing circuit of a diode 24 and capacitor 25 is connected with the secondary winding N2 of the transformer 23, and one or more auxiliary output circuits each composed of a rectifier and smoothing circuit for switching a diode 26, capacitor 27 and switching element 30 by the charge and discharge of a charge and discharge capacitor 39 are connected with the secondary winding or other winding N3. Further, when the title apparatus is constituted so that the switching element 22 on the primary side is controlled by a voltage detection circuit composed of the reference voltage source 31 and error amplifier 32 of the master output circuit, it is possible to control the voltage across the loads 35 and 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply device used as a power supply for various electronic devices.

[0002]

2. Description of the Related Art As a conventional technique, for example, as shown in the circuit diagram of FIG. 2, a switching element 2 is turned on and off to supply electric power to each output from each winding of a switching transformer 4 and is not controlled. The output voltage fluctuates greatly depending on the load current, and a dropper circuit is needed to suppress the fluctuation of the output voltage.

The operation of the circuit shown in FIG. 2 will be described below. When the switching element 2 is turned on by the output of the drive circuit 1, energy is stored in the switching transformer 4 from the DC power supply 3, and when the switching element 2 is turned off, the energy stored in the switching transformer 4 is output by each output of the switching transformer 4. Are discharged from the secondary windings of the above and are smoothed by the diodes 5 and 10 and the capacitors 6 and 11 to become a DC voltage.

Further, the output voltage of the load 7 is detected and compared with the reference voltage 8 by the error amplifier 9 to be amplified and fed back to the drive circuit 1. The feedback signal controls the ON period of the switching element 2 to keep the voltage applied to the load 7 constant. The transformer winding voltage of the load 12 is determined by the winding ratio with the transformer winding of the load 7. However, in reality, a magnetic flux leaks to the switching transformer 4, so that fluctuations due to the load current change the transformer winding voltage of the load 12. It appears as a fluctuation of.

Therefore, the transformer winding voltage of the load 12 is made higher than the set voltage and is stepped down by the transistor 13 to reduce the load 1.
Supply DC voltage to 2. Further, the output voltage of the load 12 is detected and compared with the reference voltage 15 by the error amplifier 14, the base current of the transistor 13 is controlled, and the voltage applied to the load 12 is always kept constant to improve the fluctuation of each output voltage. . Incidentally, reference numeral 16 in the drawing denotes a capacitor connected in parallel to the load 12.

[0006]

In the conventional circuit as described above, the transformer winding voltage of the load 12 is set higher than the voltage applied to the load 12, and the voltage is reduced by the transistor 13. 13 has a drawback that the circuit loss is large, large and expensive.

The present invention has been made in view of the above points, and an object thereof is to provide a high-efficiency, small-sized, inexpensive DC power supply device.

[0008]

In order to solve the above-mentioned problems, the present invention is to connect a series circuit of a switching element and a primary winding of a transformer to a DC power supply, and to connect a diode and a capacitor to the secondary winding of the transformer. A basic output circuit consisting of a rectifying / smoothing circuit, a secondary winding or another winding, a rectifying / smoothing circuit of a diode, a capacitor, and a switching element, a charging circuit consisting of a reference voltage source, an error amplifier, and a charging / discharging capacitor, and the winding of the transformer. One or more auxiliary output circuits connected to a discharge circuit consisting of a line and a resistor and a drive circuit for driving the switching element of the rectifying / smoothing circuit by the voltage across the charging / discharging capacitor are connected, and a reference voltage source is connected to the basic output circuit. A voltage detection circuit consisting of an error amplifier is connected, and the voltage detection circuit is configured to control the switching element on the primary side. When the ON period of the switching element in the auxiliary output circuit exceeds a certain period, the output of the drive circuit that turns off the switching element and the error amplifier of the voltage detection circuit of the auxiliary output circuit is out of the control range of the auxiliary output voltage. When the voltage becomes, the voltage signal is output by the detection circuit including the reference voltage and the comparator.

[0009]

With the circuit configuration described above, the auxiliary voltage detection circuit performs the ON / OFF switching operation in synchronization with the primary side switching element and the switching element of the auxiliary output circuit to turn on the switching element of the auxiliary output circuit. By dividing the energy stored in the switching transformer from the primary side to each output by turning off and using one switching transformer for each output in a time division manner, the voltage of each output can be controlled to an arbitrary value.

Further, when the output of the auxiliary output circuit is overloaded, the output of the auxiliary output circuit is put into a shutdown operation and a voltage signal is output to enable a protection operation.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is an electrical circuit diagram of the DC power supply device of the present invention. In the circuit of the present invention, a DC power supply 21 is connected to a series circuit of a switching element 22 and a primary winding N1 of a transformer 23. A diode 26 in the circuit and in the secondary or other winding N3
A charging circuit including a reference voltage source 28, an error amplifier 29, a charging / discharging capacitor 39, a discharging circuit including the winding N3 of the transformer and a resistor 38, and a charging / discharging capacitor 39 of the charging / discharging capacitor 39. One or more auxiliary output circuits connected to the drive circuit 34 for driving the switching element 30 of the rectifying / smoothing circuit according to the voltage between both ends are connected, and the basic output circuit is connected to the voltage detection circuit including the reference voltage source 31 and the error amplifier 32. A drive circuit configured to control the switching element 22 on the primary side by the voltage detection circuit, and when the ON period of the switching element 30 in the auxiliary output circuit exceeds a certain period, the switching element 30 is turned off. 34,
When the output of the error amplifier 29 of the voltage detection circuit of the auxiliary output circuit becomes a voltage outside the control range of the auxiliary output voltage, the detection circuit including the reference voltage 41 and the comparator 42 outputs a voltage signal. is there.

In FIG. 1, 33 is a drive circuit, and 35, 3
6 is a load, 37 is a diode, and 40 and 43 are resistors. The voltage applied to the load 36 is set to be lower than the transformer turns ratio (N3 / N2) times the voltage applied to the load 35.

Electric power is stored in the switching transformer 23 when the switching element 22 is on, the charging / discharging capacitor 39 is discharged through the diode 37 and the resistor 38, the switching element 30 is turned on, and when the switching element 22 is turned off. Since the winding voltage of the secondary winding N2 is lower than the voltage applied to the load 35, the diode 24 becomes non-conductive and the electric power stored in the switching transformer 23 is smoothed by the capacitor 27 and supplied to the load 36. 39 is charged from the error amplifier 29 through the resistor 40, the switching element 30 is turned off by the drive circuit 34, and the electric power stored in the switching transformer 23 is smoothed by the capacitor 25 and supplied to the load 35 to eliminate the electric power stored in the switching transformer 23. Comprising the switching element 22 is turned on repeating the same operation.

The output voltage applied to the load 36 is kept constant by turning on and off the switching element 30 by the above operation. The output voltage applied to the load 35 is kept constant by controlling the ON period of the switching element 22 by a signal that is compared with the detected voltage and the reference voltage source 31 and amplified and fed back to the drive circuit 33.

When the load 36 is short-circuited, the switching element 30 operates to extend the ON period, and when the load 36 exceeds a certain ON period, the drive circuit 34 operates so that the switching element 30 turns OFF. When the fluctuation of the output voltage becomes large and the voltage exceeds the reference voltage source 41, the voltage signal is output by the comparator 41,
Protective action. At this time, other outputs are not affected and only the output that is in the short-circuited state becomes the protection operation, and the voltage signal outputs that the protection operation has been performed.

[0017]

As described above, according to the present invention, each output voltage can be controlled without the need for an element for stepping down a voltage that causes a large loss, and the secondary winding of the switching transformer can be controlled based on the number of outputs. Since the number of wires can be reduced, the structure of the switching transformer can be simplified, the overall heat generation can be reduced, the size can be reduced, and the reliability of the DC power supply device can be improved, which is extremely useful.

[Brief description of drawings]

FIG. 1 is an electrical circuit diagram of a DC power supply device according to an embodiment of the present invention.

FIG. 2 is an electrical circuit diagram of a conventional DC power supply device.

[Explanation of symbols]

 21 DC power supply 22 Switching element 23 Switching transformer 24 Diode 25 Capacitor 26 Diode 27 Capacitor 28 Reference voltage source 29 Error amplifier 30 Switching element 31 Reference voltage source 32 Error amplifier 33 Drive circuit 34 Drive circuit 35 Load 36 Load 37 Diode 38 Resistance 39 Charge Discharge capacitor 40 Resistance 41 Reference voltage source 42 Comparator

Claims (2)

[Claims] 1. A basic output circuit comprising a rectifying / smoothing circuit of a diode and a capacitor, wherein a series circuit of a switching element and a primary winding of a switching transformer is connected to a DC power source, and a secondary winding of the switching transformer, and a secondary winding. A rectifying / smoothing circuit of a diode and a capacitor and a switching element on a wire or another winding, a charging circuit consisting of a reference voltage source, an error amplifier and a charging / discharging capacitor, a discharging circuit consisting of the winding of the transformer and a resistor, and this charging / discharging capacitor. One or more auxiliary output circuits connected to a drive circuit for driving the switching element of the rectifying / smoothing circuit according to the voltage across both ends are connected, and a voltage detection circuit consisting of a reference voltage source and an error amplifier is connected to the basic output circuit to detect this voltage. A DC power supply device configured to control the switching element on the primary side by a circuit. 2. A drive circuit in which the switching element is turned off when the ON period of the switching element in the auxiliary output circuit exceeds a certain period and the output of the error amplifier of the voltage detection circuit of the auxiliary output circuit is the auxiliary output voltage. 2. The DC power supply device according to claim 1, wherein the voltage signal is output by a detection circuit including a reference voltage and a comparator when the voltage is out of the control range.