JP2000152625A - Switching power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency by constituting a simple circuit where the number of parts is small, and also remove unnecessary converter loss, in a switching power unit which has a plurality of DC-DC converters. SOLUTION: AC from an AC power source 1 is rectified with a diode bridge 3, and the DC is supplied to the transformer 5b of a main converter and the transformer 5a of a subconverter. Then, the output is generated on the secondary side of a transformer, by turning on or turning off the main switching element 6b and the sub switching element 6a. Moreover, only the main converter is provided with an auxiliary power source 10 for a control circuit 11b, and the control circuit 11a of the subconverter is supplied with power via a switch circuit 12 from this auxiliary power source 10. The switching circuit 12 is controlled by the trigger circuit from the outside.

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 plurality of converters used for an image forming apparatus and the like, and more particularly to a switching power supply having energy saving measures.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram showing a configuration of a general switching power supply device having a plurality of (here, two) converters, and has a configuration in which energy saving measures are taken.

In FIG. 1, reference numeral 1 denotes an AC power supply, 2a, 2b
Is a noise filter, 3a and 3b are diode bridges for full-wave rectification of alternating current from the AC power supply 1, 4 is a harmonic current countermeasure circuit, and 5a and 5b are full-wave rectified DC supplied to the primary winding. In the transformer, a semiconductor sub-switching element 6a and a main switching element 6b are connected to each primary winding.

In FIG. 4, reference numeral 8 denotes a smoothing capacitor;
Reference numerals a, 9b and 9c denote rectifying and smoothing circuits for rectifying and smoothing the alternating current generated on the secondary side of the transformers 5a and 5b, and the respective outputs Vo1, Vo2 and Vo3 are supplied to the load. 10
a and 10b are auxiliary power supplies for the control circuits 11a and 11b;
Reference numeral 3 denotes a relay provided for energy saving. Its contact is interposed between the AC power supply 1 and the noise filter 2a, and a diode 14 for preventing backflow is connected to the coil.

[0005] The switching power supply having the above configuration has two DC-DC converters, and each converter is independently controlled by each of the control circuits 11a and 11b. Also, auxiliary power supplies 10a, 1 for control.
0b is also provided separately.

An apparatus using such a switching regulator has a so-called standby mode which is not in use, and is devised so as to consume as little power as possible. At present, energy conservation tends to be regulated by law in each country.

Here, important points for promoting the above energy saving are high efficiency, low cost, and a method of cutting an unused output system with small power (mainly 20 W or less).

In the circuit shown in FIG. 4, the relay 13 is controlled by a trigger signal, for example, by opening and closing the door of the apparatus. When the door is opened, the contacts of the relay 13 are opened to output the outputs Vo1 and V1.
The operation of the two-system converter is stopped. This is due to safety standards such as the presence of dangerous equipment inside the door or the system configuration.
The C input is controlled by opening and closing a switch.

[0009]

In a switching power supply device having a plurality of converters as described above, for example, when a door of the device is opened, a circuit for detecting the operation to stop the operation of the device, and The drive voltage is required, the circuit configuration is complicated, the device is large, the device is expensive, and there is a converter loss due to unnecessary output operation during standby, resulting in a problem that the efficiency is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a switching power supply device having a simple configuration, high efficiency, low cost, and no increase in size. It is an object.

[0011]

A switching power supply device according to the present invention is configured as follows.

(1) In a switching power supply device having a plurality of converters for switching an input on a primary side of a transformer and generating an output on a secondary side of the transformer, an auxiliary power supply for a control circuit is provided in an arbitrary converter. In addition, a switch circuit for supplying power from the auxiliary power supply to a control circuit of another converter is provided, and the switch circuit is controlled by an external signal.

(2) In the configuration of the above (1), the converter is a converter for performing DC-DC conversion.

(3) In the above configuration (1) or (2), the control circuit controls the output voltage.

(4) In any of the above constitutions (1) to (3), an auxiliary power supply is provided for another converter.

[0016]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention. The switching power supply of this embodiment has transformers 5a and 5b that insulate the primary side and the secondary side, switching elements 6a and 6b such as transistors, and control circuits 11a and 11b. Has two) DC-DC converters.

In the configuration shown in FIG. 1, the AC from the AC power supply 1 is passed through the noise filter 2 to the diode bridge 3.
, Where it is full-wave rectified and converted to direct current.
This direct current is supplied to the transformer 5b of the first (main) converter via the diode 7 and the smoothing capacitor 8, and the second direct current is passed through the harmonic current countermeasure circuit 4.
This is supplied to the transformer 5a of the (sub) converter. The alternating current generated on the secondary side of the transformers 5a, 5b by the driving of the switching elements 6a, 6b on (ON) and off (OFF) is converted into direct current by the rectifying and smoothing circuits 9a, 9b, 9c, and each output thereof is outputted. Vo1, Vo2, Vo3 are supplied to the load.

In the configuration shown in FIG. 1, an auxiliary power supply 10 for the control circuit 11b is provided only in the main converter as an arbitrary converter, and the auxiliary power supply 10 switches the control circuit 11a to the control circuit 11a of the sub-converter. The driving power is supplied via the circuit 12. The switch circuit 12 for supplying power from the auxiliary power supply 10 to another converter is controlled by an external trigger signal.

In the switching power supply device configured as described above, when the main converter starts to be activated by turning on the AC power supply 1, the control circuit 11b supplied with power from the auxiliary power supply 10 outputs the voltage of the output Vo3. It operates so as to have a constant voltage. At this time, the above-described power conversion is performed by the switching element 6b and the transformer 5b. This operation is the same as a general switching regulator.

When the switch circuit 12 is turned on by a trigger signal from the outside, the power of the auxiliary power supply 10 is also supplied to the control circuit 11a of the sub-converter, whereby the sub-converter also starts operating and the transformer 5a
, The voltages of the outputs Vo1 and Vo2 on the secondary side rise. Conversely, the switch circuit 12 is triggered by an external trigger signal.
Becomes non-conductive, the sub-converter stops operating.

As described above, in this embodiment, the auxiliary power supply 10 for control is provided in one converter, and power is supplied from the auxiliary power supply 10 to another converter, and the presence or absence of the power supply is determined by an external signal. Switch circuit 12
, A simple configuration with a small number of parts is provided, and a low-cost device can be realized without increasing the size of the device. In addition, the unused output system can be easily opened and closed by an external signal, and there is no converter loss due to unnecessary output operation during standby.
It is an efficient and energy-saving circuit.

In the circuit shown in FIG. 1, the harmonic current countermeasure circuit 4 is provided on the input side of the transformer 5a of the sub-converter. The diode 7 is used to prevent the backflow necessary when the harmonic current countermeasure circuit 4 is provided. It is provided as a diode.
When there is no harmonic current countermeasure circuit 4 and a capacitor input is provided, the diode 7 may not be provided.

Further, a configuration in which three or more converters, that is, a third converter, a fourth converter,..., And three or more converters are connected in parallel between AB in the circuit of FIG. In this case, power is supplied from the auxiliary power supply 10 of the first converter to the control circuits subsequent to the third converter similarly to the second converter, and whether or not the power is supplied is determined by an external signal by the switch circuit 12. This switch circuit 12 includes a relay,
A general configuration using a transistor, a three-terminal regulator with on / off terminals, or the like may be used.

FIG. 2 is a circuit diagram showing the configuration of another embodiment of the present invention. The same reference numerals as in FIG. 1 denote the same components. In this embodiment, the auxiliary power supply 106 of the main converter is used.
In addition, an auxiliary power supply 10a is provided in the sub-converter. Otherwise, the configuration is the same as that of the circuit of FIG.

As described above, by providing the auxiliary power supply 10a also in the sub-converter, the rise time of the output of both the main converter and the sub-converter can be further shortened. In the circuit of FIG. 1, the sub-switching element 6a
Although the capacity of the auxiliary power supply 10 is increased for the drive of, the start of the main converter may be delayed,
This is resolved in the circuit of FIG.

FIG. 3 shows how the output Vo1 of the sub-converter rises. The solid line shows the output of the circuit of FIG. 1, and the broken line shows the output of the circuit of FIG.
As shown, the circuit of FIG. 1 requires approximately 800 ms for the time t1 until the output Vo1 rises, but the circuit of FIG. 2 uses the synergistic effect of the auxiliary power supplies 10a and 10b to generate approximately 5 ms.
The time t0 is reduced by about 300 ms to 00 ms.

[0027]

As described above, according to the present invention, a simple structure with a small number of parts is provided, and the output system which is not used can be easily opened and closed with an external signal at a low cost without increasing the size of the apparatus. And eliminates converter loss due to unnecessary output operation during standby.
The effect that an efficient energy saving circuit can be obtained is obtained.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram showing a configuration of another embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a state of output rising.

FIG. 4 is a circuit diagram showing a configuration of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 3 Diode bridge 5a Transformer 5b Transformer 6a Sub-switching element 6b Main switching element 9a Rectifying smoothing circuit 9b Rectifying smoothing circuit 9c Rectifying smoothing circuit 10 Auxiliary power supply 10a Auxiliary power supply 10b Auxiliary power supply 11a Control circuit 11b Control circuit 12 Switch circuit

Continued on the front page F term (reference) 5G065 AA01 AA08 DA01 EA06 FA02 GA04 GA06 HA04 JA02 KA01 KA04 LA07 MA10 NA09 5H730 AA15 AA18 AS01 BB21 BB57 BB81 CC01 CC04 DD04 EE01 EE73 VV01 XC12

Claims (4)

[Claims] In a switching power supply device having a plurality of converters for switching an input on a primary side of a transformer to generate an output on a secondary side of the transformer, an arbitrary power supply is provided with an auxiliary power supply for a control circuit. A switching circuit for supplying power from the auxiliary power supply to a control circuit of another converter, wherein the switching circuit is controlled by an external signal. 2. The switching power supply according to claim 1, wherein the converter is a converter that performs DC-DC conversion. 3. The switching power supply according to claim 1, wherein the control circuit controls an output voltage. 4. The switching power supply according to claim 1, wherein an auxiliary power supply is provided in another converter.