JP2001078448A - Multi-output power supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide power saving for a device and relax thermal design conditions by reducing the electric power loss of sub output easily and with a low-cost configuration. SOLUTION: This power supply unit is provided with a plurality of extension lines fitted on a transformer winding for sub output, a sub output switching part 1 formed with a switch on the extension line, an operating mode detection part 3, and a control part for controlling the sub output switching part 1, based on a signal from the operating mode detection part 3 and regulating the input voltage of a three-terminal regulator, thereby reducing the power loss of the sub output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-output power supply device using one transformer and using a three-terminal regulator for stabilizing the voltage on the sub-output side. A plurality of lead lines are provided in the transformer winding and switches are provided for each lead line. The input voltage on the sub output side is adjusted according to the change in the output current on the main side, thereby reducing power loss inside the power supply.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram of a conventional multi-output power supply device. 41 is a transformer, and one of the primary windings 411 is connected to an AC through a rectifier circuit not shown.
A is connected to a power supply, and the other is connected via a rectifier circuit, which is not described, to a switching element FET47.
Connected to C power supply. The control circuit 48 is connected to the drain terminal of the FET 47 and controls the duty of the drive pulse signal of the FET 47.

A secondary winding 412 of the transformer 41 is connected to a main output terminal Vcc via a diode 46. The secondary winding 413 of the transformer 41 is connected to the sub output terminal Vaa via a constant voltage circuit including a diode 42, a capacitor 44, a capacitor 45, and a three-terminal regulator 43.

In such a power supply device that obtains multiple outputs with one transformer, power proportional to the power supplied to the main output is supplied to the sub-output side.

On the sub output side, the power used in the device (the three-terminal regulator output voltage Vout × the output current Io)
Extra power other than ut) results in loss of the three-terminal regulator. Loss of three-terminal regulator = (input voltage Vin−output voltage Vout) × output current Iout

[0006]

SUMMARY OF THE INVENTION A multi-output power supply as described above, that is, a power supply that obtains multiple outputs with one transformer, and the sub-output current of the power supply regardless of the operation of the apparatus using the power supply. Is constant, if the operation of the device causes the main output current to increase (the main output power increases), the input power on the sub-output side also increases in proportion to the output of the sub-output three-terminal regulator. There is a problem that wasteful power loss increases rapidly and hinders power saving design and thermal design conditions.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and uses a single transformer and a three-terminal regulator for stabilizing the voltage on the sub output side. In a multi-output power supply device, multiple lead wires are provided on the transformer winding for sub output, and switches are provided for each lead wire, and the input voltage on the sub output side is adjusted according to changes in output current on the main side By doing so, the power loss inside the power supply is reduced.

[0008]

DETAILED DESCRIPTION OF THE INVENTION (1) Using one transformer,
In a multi-output power supply device using a three-terminal regulator for stabilizing the voltage on the sub-output side, a sub-output switching unit having a plurality of leads on a transformer winding for the sub-output and a switch on the leads is provided. An operation mode detection unit that detects an operation mode of a device to which a power supply device is connected, and a control unit that controls a sub output switching unit based on a signal from the operation mode detection unit and adjusts an input voltage of the three-terminal regulator. This makes it possible to reduce the power loss of the sub output with an easy and inexpensive configuration.

(2) In the multi-output power supply described in (1), an operation mode detection for detecting an operation mode of a device connected to the power supply by detecting a change in a switching current of a primary winding of a transformer. It has a unit. This makes it possible to adjust the input voltage of the three-terminal regulator on the sub output side with a simple configuration.

(3) In the multi-output power supply described in (1), an operation mode in which an operation mode of a device connected to the power supply is detected by detecting a change in an external signal from a device connected to the power supply. A detection unit is provided. This makes it possible to freely adjust the input voltage of the three-terminal regulator on the sub output side regardless of the load on the device side.

[0011]

FIG. 1 is a block diagram showing the configuration of the present invention. In the figure, reference numeral 1 denotes a plurality of lead wires for a transformer winding for a sub output of a multi-output power supply device using one transformer and using a three-terminal regulator for voltage stabilization on the sub output side, and This is a sub output switching unit in which a switch is provided on the lead line. Reference numeral 3 denotes an operation mode detection unit for detecting an operation mode of a device to which the power supply device is connected. It is a control unit for adjustment.

FIG. 2 shows a block diagram (1) of an embodiment of the present invention. In the figure, reference numeral 21 denotes a transformer, one of the primary windings 211 is connected to an AC power supply via a rectifier circuit not shown, and the other is an operation mode detecting unit 29 for detecting a change in switching current. And an AC power supply via a rectifier circuit not described as an FET 27 as a switching element. And FET2
7, a control circuit 28 is connected to the drain terminal,
The duty of the 27 drive pulse signals is controlled.

The secondary winding 212 of the transformer 21 is connected to a main output terminal Vcc via a diode 26. The secondary winding 213 of the transformer 21 is connected to the sub output terminal Vaa via a constant voltage circuit including a diode 22, a capacitor 24, a capacitor 25, and a three-terminal regulator 23.

The secondary winding 213 of the transformer 21 is provided with two lead wires and a sub output switching unit 1 having a switch such as a semiconductor switch on the lead wire.
The input voltage of the three-terminal regulator 23 can be adjusted. The sub output switching unit 1 includes a transformer 2
1 receives a signal from an operation mode detection unit 29 that detects an operation mode of a device connected to the power supply device by detecting a change in a switching current of the primary winding 211 and receives an input voltage of the three-terminal regulator 23. The control unit 2 controls the difference between the output voltage and the output voltage to a specified value.

With such a configuration, it is possible to adjust the input voltage of the three-terminal regulator on the sub output side with a simple configuration.

In this example, two lead wires are provided to the secondary winding 213 of the transformer 21 to switch the input voltage of the three-terminal regulator 23 to two values. Put out above, three-terminal regulator 2
The input voltage of No. 3 may be finely adjusted.

In this example, the number of sub-outputs is one. However, even when there are a plurality of sub-outputs,
Are provided on the respective secondary output secondary windings, and the control unit 2
May be used to control a plurality of sub-output switching units 1.

FIG. 3 shows a block diagram (2) of an embodiment of the present invention. In the figure, 1, 2, 21 to 28, 21
1, 212, and 213 correspond to 1, 2, 21 to 28, and 2 in FIG.
11, 212, and 213.

In this example, the sub-output switching unit 1 detects a change in an external signal of the CPU 31 that controls the device connected to the power supply device, thereby detecting a signal from the operation mode detecting unit 39 for detecting the operation mode of the device. In response, the control unit 2 controls the difference between the input voltage and the output voltage of the three-terminal regulator 23 to be a specified value.

With such a configuration, it is possible to freely adjust the input voltage of the three-terminal regulator 23 on the sub-output side regardless of the load on the apparatus side.

[0021]

The present invention is embodied in the form described above, and has the following effects.

The power loss of the sub output can be reduced with an easy and inexpensive configuration, and the thermal design conditions can be relaxed along with the power saving of the device. Further, it is possible to cope with a device having different main output conditions and sub output conditions by increasing the number of lead wires and switches.
When the sub-output is unnecessary in the operation of the device, all the switches are turned off, and the input voltage of the three-terminal regulator is cut, so that power saving of the device can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of the present invention.

FIG. 2 is a block diagram showing an example of the configuration of an embodiment of the present invention (1).
It is.

FIG. 3 is a configuration block diagram of an embodiment of the present invention (2).
It is.

FIG. 4 is an example of a conventional configuration block.

[Explanation of symbols]

 1 Sub output switching unit 2 Control unit 3, 29, 39 Operation mode detection unit

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Claims (3)

[Claims] 1. A multi-output power supply device using one transformer and using a three-terminal regulator for stabilizing a voltage on a sub-output side. A sub-output switching unit (1) having a switch on a lead line, an operation mode detection unit (3) for detecting an operation mode of a device to which a power supply device is connected, and a sub-output unit based on a signal from the operation mode detection unit (3). A multi-output power supply device comprising: a control unit (2) that controls an output switching unit (1) and adjusts an input voltage of a three-terminal regulator. 2. The operation mode detection unit according to claim 1, wherein an operation mode of a device connected to the power supply device is detected by detecting a change in a switching current of a primary winding of the transformer. A multiple output power supply device comprising (29). 3. The multi-output power supply device according to claim 1, wherein an operation mode of the device connected to the power supply device is detected by detecting a change in an external signal from the device connected to the power supply device. A multi-output power supply device comprising a unit (39).