JP2555686Y2 - Switching power supply - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply having a remote sensing terminal for correcting a voltage drop between an output terminal and a load, and more particularly to a switching power supply having a parallel operation function.

[0002]

2. Description of the Related Art Generally, in a power supply device, remote sensing for detecting a voltage between output voltage lines in order to prevent a voltage fluctuation and a power loss caused by a voltage drop of a wire connected between an output terminal and a load. A terminal is provided and this remote sensing terminal is connected to a load by a very thin remote sensing line shown by a broken line in FIG. 3 so that the voltage drop can be corrected. FIG.
Shows a circuit diagram of a conventional switching power supply device having a remote sensing terminal, wherein a DC input voltage Vi is applied to a primary winding of a transformer 1 that insulates a primary side and a secondary side,
Switching element 2 composed of a transistor in the primary winding
Are connected in series to form an inverter. The voltage induced in the secondary winding of the transformer 1 is rectified and smoothed by a rectifier circuit 3 composed of a diode or the like and a smoothing capacitor 4, and a constant DC output voltage Vo is applied to a load 5 connected between output terminals + V and -V. Supply. The output voltage detection circuit 6 has remote sensing terminals + S and -S for detecting a voltage between output voltage lines. The remote sensing terminal + S is connected to the load 5 by a remote sensing line indicated by a broken line, or is connected by a solid line. The output terminal + V is connected by the short-circuit line shown, and the remote sensing terminal -S is similarly connected to the load 5 or the output terminal -V. The remote sensing terminal -S is connected to a ground terminal COM that shares the ground of each signal terminal of the power supply device, and resistors 7 and 8 for voltage division are connected in series between the remote sensing terminals + S and -S. The voltage between the remote sensing terminals + S and -S is divided by the resistors 7 and 8, and this voltage is applied as a detection voltage to the operational amplifier 9 and compared with the reference voltage E. When the detected voltage becomes higher than the reference voltage E in accordance with the rise of the DC output voltage Vo, the output of the operational amplifier 9 becomes H level, and based on this signal, the pulse width control circuit 10 shortens the on-time of the switching element 2, When the detection voltage becomes lower than the reference voltage E in accordance with the decrease in the DC output voltage Vo, the output of the operational amplifier 9 becomes L level, and based on this signal, the pulse width control circuit 10 makes the ON time of the switching element 2 longer. It acts to keep the DC output voltage Vo constant.

When the voltage drop from the output terminals + V, -V to the load 5 is almost negligible due to a short wiring or the like, to simplify the wiring between the power supply device and the load,
The remote sensing terminals + S, -S are connected to respective output terminals + V, -V. However, in this state, if the voltage drop between the output terminals + V, -V and the load 5 becomes longer due to a longer wiring, etc., the output voltage fluctuates due to the load current and the operation becomes unstable. In such a case, the remote sensing terminals + S, -S are connected to the load 5
, The switching element 2 is controlled so as to keep the voltage across the load 5 constant, so that the output terminals + V, -V to the remote sensing terminals + S,-.
It is possible to correct a voltage drop occurring between the load 5 and the connection point of S.

A conventional switching power supply device having such a remote sensing terminal requires a main power supply and a sub power supply to perform a master / slave operation and to add a current balance function for monitoring the sharing of the output current of the power supply. Thereby, parallel operation by a plurality of power supplies is possible. This is, for example, as shown in FIG.
A, 11B remote sensing terminals + S, -S are connected to output terminals + V, -V, and power supply devices 11A, 11B are connected to output terminals + V, -V and load 5 to output DC output voltage Vo.
And a ground terminal COM sharing the ground of various circuits for parallel operation of the power supply units 11A and 11B and a current balance terminal C having a current balance function.
B and so on.

[0005]

In the above prior art, the remote sensing terminals + S, -S of each power supply 11A, 11B are connected to output terminals in order to simplify wiring between the power supply and the load during parallel operation. When directly connected to + V and -V, the resistance RA corresponding to the voltage drop generated between the output terminal -V of the power supply 11A and the load 5 and the power supply 11A
When the value of the resistor RB corresponding to the voltage drop generated between the output terminal -V of B and the load 5 differs from that of the power supply device 11A,
Unnecessary current is generated between the output terminal and V of 11B. For example, when the current generated from the power supply device 11A is larger than the current generated from the power supply device 11B, a current flows from the output terminal -V of one power supply device 11A to the output terminal -V of the other power supply device 11B. Flows into the ground terminal COM short-circuited with the output terminal −V of the power supply 11B.
The potentials of the ground terminals COM of the terminals 11A and 11B do not match, and the output balance between the power supply devices 11A and 11B is impaired, causing a problem that stable control cannot be performed.
This problem can be solved by connecting the remote sensing terminals + S, -S and the load 5 with a remote sensing line. However, the remote sensing line is very thin, and there is a high possibility of disconnection. During operation, there is a problem that the wiring connecting the power supply devices is complicated and the wiring is more likely to be disconnected. Therefore, it is desired to solve the above-described problem that occurs during parallel operation without using a remote sensing line.

Therefore, the present invention prevents the output balance from being impaired due to the difference in voltage drop between the output terminal of each power supply device and the load during parallel operation without using a remote sensing line, thereby achieving stable control. It is an object of the present invention to provide a switching power supply device capable of performing the following.

[0007]

The present invention has a remote sensing terminal for correcting a voltage drop of a line between an output terminal and a load as a feedback circuit for stabilizing a DC output voltage. A switching power supply device that includes an output voltage detection circuit that detects a voltage of a remote sensing terminal, compares the voltage with a reference voltage, and controls an on / off operation of the switching element based on a result of the comparison; In the parallel operation, the resistance limiting the current flowing due to the difference of the voltage drop generated between the output terminal and the load of each of the power supply devices during the parallel operation of the minus remote sensing terminal and each signal terminal of the power supply device It is configured to be connected between a ground terminal and a common ground.

[0008]

According to the above configuration, a DC output voltage is supplied to the load from the output terminal of each power supply device during the parallel operation, and a difference in voltage drop between the output terminal of each power supply device and the load causes a certain power supply device. When a current flows from the output terminal to the output terminal of another power supply device, this current is limited by a resistor connected between the negative output terminal and the ground terminal and does not flow to the ground terminal side.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a circuit diagram of a switching power supply showing one embodiment of the present invention. The same parts as those in FIG. 3 are denoted by the same reference numerals, and the description of the same parts will be omitted.

In FIG. 1, a remote sensing terminal +
S and -S are connected to output terminals + V and -V, and the output voltage detection circuit 6A connects resistors 12 and 13 for voltage division between the remote sensing terminal + S and the ground terminal COM. The connection point 13 is connected to the non-inverting input terminal of the operational amplifier 14. On the other hand, the remote sensing terminal -S and the ground terminal
COM, a resistor 15 for current limiting is connected, and a resistor 16 is connected between the remote sensing terminal -S and the inverting input terminal of the operational amplifier 14, and the inverting input terminal of the operational amplifier 14 A feedback resistor 17 is connected between the output terminal. Voltage dividing resistors 18 and 19 are connected between the output terminal of the operational amplifier 14 and the ground terminal COM. The connection point of the resistors 18 and 19 is connected to the inverting input terminal of the operational amplifier 20. 3 except that the reference voltage E is supplied to the non-inverting input terminal and the output terminal is connected to the pulse width control circuit 10.

FIG. 2 shows a connection diagram between the respective power supplies in the parallel operation. As shown in FIG. 4, the output terminals + V, -V of the respective power supplies 21A and 21B are connected to the load 5, and the power supply is connected. The ground terminals COM of the terminals 21A and 21B and the current balance terminal CB having a current balance function are connected to each other.

Next, the operation of the above configuration will be described.
When the DC input voltage Vi is applied to the primary winding of the transformer 1, the voltage induced in the secondary winding of the transformer 1 by the switching of the switching element 2 is rectified and smoothed by the rectifying circuit 3 and the smoothing capacitor 4, and the output terminal + V, A constant DC output voltage Vo is supplied to the load 5 between -V. In the output detection circuit 6A, the voltage between the output terminal + V connected to the remote sensing terminal + S and the ground terminal COM of the power supply device is divided by the voltage dividing resistors 12 and 13 and supplied to the non-inverting input terminal of the operational amplifier 14. . The operational amplifier 14 is connected to the resistors 12, 13
Amplifies the potential difference between the voltage divided by the above and the voltage of the remote sensing terminal -S by the amplification degree determined by the resistors 16 and 17, and the output signal from the operational amplifier 14 is
The voltage is divided by 19 and supplied to the operational amplifier 20 as a detection voltage, and the operational amplifier 20 compares the detection voltage with the reference voltage E. Then, a pulse having a conduction width based on the comparison result of the operational amplifier 20 is output from the pulse width control circuit 10,
The switching element 2 is turned on and off.

During the parallel operation, the power supply 21
The value of the resistor RA corresponding to the voltage drop between the output terminal -V of A and the load 5 and the value of the resistor RB corresponding to the voltage drop between the output terminal -V of the power supply 21B and the load 5 are different. When the current generated from the power supply 21A becomes larger than the current generated from the power supply 21B, the output terminal of the power supply 21A
Current flows from V to the output terminal −V of the power supply 21B,
An attempt is made to flow from the output terminal -V of the power supply 21B to the ground terminal COM through the remote sensing terminal -S. However, this current is generated by the resistor 15 connected between the remote sensing terminal -S of the power supply 21B and the ground terminal COM.
Therefore, the parallel operation of the power supply devices 21A and 21B is controlled while the ground terminals COM of the power supply devices 21A and 21B are kept at the same potential.

As described above, in the present embodiment, for example, the power supply unit 21A, 21B is controlled by the difference in voltage drop between the output terminals + V, -V and the load 5 during the parallel operation.
Even if an unnecessary current is generated from the output terminal -V of the power supply 21B from the output terminal -V of the power supply 21B, this current is supplied to the current limiting resistor 15V.
Ground terminal COM, which shares the ground of each terminal such as the current balance terminal.
The potential of M is kept equal in each of the power supply devices 21A and 21B, and stable control can be performed without impairing the output balance between the power supply devices 21A and 21B. In addition, since it is not necessary to use the remote sensing line, the disconnection of the remote sensing line releases the connection between the remote sensing terminal and the output terminal, and the problem that the power supply device may be broken due to an increase in the output voltage can be solved.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention. For example, a MOS-type FET or the like may be used as the switching element instead of the transistor. Also, the output voltage detection circuit is shown to compare the detection voltage with the reference voltage using an operational amplifier.However, a shunt regulator with a built-in reference voltage is used.The detection voltage is applied to the reference of this shunt regulator, and the photocoupler is connected. The present invention can be similarly applied to a type in which a detection signal is sent to a pulse width control circuit via the same.

[0016]

According to the present invention, a remote sensing terminal for correcting a voltage drop of a line between an output terminal and a load is provided as a feedback circuit for stabilizing a DC output voltage. An output voltage detection circuit that detects a voltage, compares the detected voltage with a reference voltage, and controls an on / off operation of the switching element based on the comparison result;
In a switching power supply device capable of parallel operation by a plurality of power supply devices, a resistance that limits a current flowing due to a difference in the voltage drop generated between the output terminal and the load of each of the power supply devices during the parallel operation is reduced by the minus. It is configured to be connected between the side remote sensing terminal and the ground terminal that shares the ground of each signal terminal of the power supply, so that, during parallel operation, between the output terminal of each power supply and the load It is possible to provide a switching power supply device capable of preventing output balance from being impaired due to a difference in generated voltage drop without using a remote sensing line and performing stable control.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a wiring state when the power supplies according to the embodiment of the present invention are operated in parallel.

FIG. 3 is a circuit configuration diagram of a conventional switching power supply device.

FIG. 4 is an explanatory diagram showing a wiring state when a conventional switching power supply device is operated in parallel.

[Explanation of symbols]

 2 Transistor (switching element) 5 Load 6A Output voltage detection circuit 15 Resistance 21A, 21B Power supply + V, -V Output terminal + S, -S Remote sensing terminal COM Ground terminal

Claims (1)

(57) [Scope of request for utility model registration] A feedback circuit for stabilizing a DC output voltage has a remote sensing terminal for correcting a voltage drop of a line between an output terminal and a load, and detects a voltage of the remote sensing terminal. An output voltage detection circuit that controls the on / off operation of the switching element based on the comparison result. The switching power supply device that can be operated in parallel by a plurality of power supply devices. A ground terminal that shares the ground of the negative side remote sensing terminal and the ground of each signal terminal of the power supply device with a resistor that limits a current flowing due to a difference in the voltage drop generated between the output terminal and the load of the power supply device. A switching power supply device configured to be connected between the switching power supply devices.