JPS6139864A - Multioutput switching regulator - Google Patents

Abstract

PURPOSE:To reduce the size of a power source by operating only the controller of the first switching regulator by an external power source, and feeding back from the first output to the controller of the second switching regulator. CONSTITUTION:A multioutput switching regulator has the first switching regulator A for controlling by a controller 1 a DC rectified and smoothed from an AC input via a diode bridge DB1 to generate outputs 1, 2, and the second switching regulator B for generating outputs 3, 4 in parallel. In this case, power is supplied from a transformer T5 separately provided to the controller 1, and from the output 2 to the controller 2. Thus, when a main switch is closed, the output 2 rises before the outputs 3, 4, and it is detected by a resistor R8 at the overload time of the output 2 to stop the oscillation of the controller 1, and outputs 3, 4 are turned OFF as the output 2 is turned OFF.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a multi-mount switching regulator in which a plurality of converter transformers are each provided with a plurality of output sections.

(Prior art) Although it is most economical to obtain multiple outputs from one converter transformer, multi-output switching regulators using multiple converter transformers are often used due to reasons such as output accuracy and power supply shape. . FIG. 2 shows a conventional example.

AC input is diode bridge DB, , DB,
.

It is rectified and smoothed by capacitors c, , C, and smoothed into direct current. In this example, converter transformer ′T
8. Switching transistor Q1. Pulse transformer T
a 9 Output 1 from control unit 1, etc. Generates output 2. A first switching regulator.

Converter transformer 3. Switching transistor Q
t t pulse transformer 4. A second switching regulator that generates outputs 3 and 4 from the control section 2 and the like is connected in parallel.

Power to the control section 1 and the control section 2 is supplied from an auxiliary power supply consisting of a transformer Tlft, a diode bridge DB, and a capacitor C6. The other configurations are the same as those of a general switching regulator, so explanations will be omitted.

The auxiliary power source is the first one mentioned above. Since power is supplied to both of the second switching regulators, the size of the switching regulator becomes large, which is an obstacle to making the switching regulator smaller and more efficient. By the way, the eleventh and second switching regulators are
Because they operate completely independently, even if one side stops outputting for some reason, the other side will continue outputting. Furthermore, the way the switch (not shown) starts up after being turned on is also irregular.

For example, when using such a power source in a device such as an electronic copying machine,
Output 1 of the first switching regulator is connected to an analog circuit such as an OP amplifier, output 2 is connected to a digital circuit such as a microcomputer, output 3 of the second switching regulator is connected to a drive circuit such as a motor or solenoid, and output 4 is connected to a high voltage Let us consider the case where it is used for tS circulation.

Immediately after the main switch is turned on, the first and second switching regulators start up independently. in this case,
There is no problem if the first switching regulator starts up first, but if for some reason the second switching regulator starts up first, the digital control circuit supplied with power from output 2 may become unstable. Since output 3 rises in this state, problems such as malfunction of the talk counter occur. Also, if output 2 becomes overloaded (short-circuited) for some reason, the digital control circuit (copier control circuit) will not be able to control the power supply to the drive circuit and high-voltage generation circuit, as in the case of startup described above. It will continue to be supplied. In such a case, the motor of the optical scanning system may continue to rotate,
This causes the inconvenience that the high-voltage power source for charged transfer continues to be turned on.

(Objective) An object of the present invention is to improve the above-mentioned drawbacks and to provide a switching power supply that is compact and operates stably.

(Structure) For this purpose, in the present invention, power is supplied from a separately provided transformer to the control section of the first switching regulator formed from the first converter transformer.

Further, the present invention is characterized in that the output DC voltage of the first switching regulator is used in the control section of the second switching regulator including the second converter transformer.

An embodiment of the present invention will be described below based on the embodiment shown in FIG.

In FIG. 1, the auxiliary power supply consisting of T, , DB, , C, is connected to the first switching regulator A.
Supplies power only to The difference from the conventional example shown in FIG. 2 is that the control section 2 of the second switching regulator B is configured to be supplied with power from the output 2 of the first switching regulator A. The auxiliary power source is
Since power is only supplied to the switching regulator A, its output capacity can be halved, and miniaturization is possible. When the main switch is turned on, the first switching regulator A is operated by the auxiliary power supply, and after it starts up, power is supplied to the control section of the second switching regulator B based on its output, and the second switching regulator A is turned on. The switching regulator starts up.

Therefore, output 2 always rises earlier than outputs 3 and 4, and the above-mentioned problem +X does not occur.

Also, when the output 2 becomes overloaded for some reason, the abnormality is detected by the load current detection resistor B, the control section 1 stops oscillation, and the output of the first switching regulator A becomes
It turns off. Therefore, both outputs 3 and 4 of the second switching regulator B, which receives power supply from the first switching regulator A to the control unit 2, are turned off.
This will avoid the problems mentioned above.

(Effects) The present invention is as described above.According to the present invention, it is possible to set a rising order among the respective outputs, and if it is conveniently connected to various loads according to this order, No trouble will occur during operation of the equipment.

In addition, only the control section of the first switching regulator is operated by an external power supply, and the control section of the second switching regulator receives feedback from the output of the first switching regulator, so it has priority. A high degree of output can turn off the output of an abnormal Shisen.

Furthermore, there is an effect that the power supply section can be made smaller.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a multi-output switching regulator according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional multi-output switching regulator.

Claims (1)

[Claims] The AC power supply voltage is rectified and smoothed, the resulting DC voltage is applied to the primary windings of multiple converter transformers, and the switching transistors connected in series to the primary windings of these converter transformers are turned on by a signal from the control unit. In a multi-output switching regulator that performs off control, rectifies and smoothes the output obtained at the secondary winding of the converter transformer, and obtains a plurality of DC output voltages, a control unit of a first switching regulator comprising a first converter transformer. As a power source for the control section of the second switching regulator consisting of the second converter transformer, use an AC input that has been step-down rectified and smoothed, or a step-down DC voltage that has been rectified and smoothed the AC input. A multi-output switching regulator characterized in that it uses the output DC voltage of a switching regulator comprising a first converter transformer.