JP2000354375A - Power unit, electronic equipment, and method for controlling the power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching power unit which can reduce losses during standby, and at the same time, can significantly reduce unnecessary power consumption during the standby on a system main body side. SOLUTION: A system controller 7 discriminates standby actual operation of a system main body and switches the oscillation frequency of a switching power unit. When the system main body is actually operated, the controller 7 impresses an 'L' level frequency switching signal CH upon an input terminal 12. When the signal CH is impressed upon the terminal 12, an output on/off circuit 18 is turned on and supplies a power Vo1 to a main body-side DC-DC converter 6. When the system main body is actually operated, the oscillating state by means of a triangular wave generating circuit OSC 3 becomes a high-frequency state. During the standby of the system main body, the controller 7 impresses an 'H' level signal upon the input terminal 12. When the 'H' level signal is impressed upon the terminal 12, the output on/off circuit 18 is turned off and the power supply to the system main body-side DC-DC converter 6 is interrupted. During this standby, the oscillating state by means of the OSC 3 becomes a low-frequency state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a power supply used for a facsimile or a printer having a standby mode, a control method thereof, and an electronic apparatus using the power supply.

[0002]

2. Description of the Related Art Conventionally, there has been a power supply device used in a system that has a long standby state with respect to actual operation, for example, a facsimile or a printer as shown in FIG.

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

This switching power supply device has a primary winding P
1. Transformer 1 having control winding P2 and secondary winding S1
It has. Further, a switching element Q1 connected to one of the primary windings P1 of the transformer 1 for switching a DC input voltage, and a PWM control formed between the control winding P2 of the transformer 1 and the switching element Q1. The circuit includes a circuit 2 and a triangular wave generation circuit (OSC) 3 for applying a pulse signal having a substantially constant frequency to the PWM control circuit 2.

The secondary winding S1 of the transformer 1 is connected to the diode D2 of the rectifying and smoothing circuit 11 and the capacitor C1. The output voltage after rectifying and smoothing is supplied to the PWM control circuit via the error detecting circuit 4 and the photocoupler 5. 2 is supplied. Then, the PWM control circuit 2 generates a pulse signal whose duty is controlled based on the signal output from the triangular wave generation circuit 3. This pulse signal is supplied to the switching element Q1.
To realize a constant output voltage Vo.

The output voltage V of such a switching power supply device
o is supplied to a system controller 7 and a load 8 (a plurality of driving portions of the system main body) of the system main body via a DC / DC converter 6 of the system main body such as a printer.

[0007] The switching power supply device is characterized by frequency switching means 13 for switching the repetition frequency of the pulse signal applied to the switching element Q1 in at least two steps; A signal input terminal 12 to which a frequency switching signal CH for instructing frequency switching from the controller 7 is applied.

Next, the operation of the circuit will be described.

When power is supplied from the DC power supply 9, power is supplied to the PWM control circuit 2 and the triangular wave generation circuit 3 by the starting circuit 10, and the operation starts. The PWM control circuit 2 generates a pulse signal having a constant repetition frequency based on the triangular wave output from the triangular wave generation circuit 3.

The switching element Q1 is continuously turned on / off by a pulse signal output from the PWM control circuit 2. When the switching element Q1 is in the ON state,
A current flows from the DC power supply 9 to the primary winding P1 of the transformer 1 via the switching element Q1, and energy is stored in the transformer 1.

Next, when the switching element Q1 is turned off,
Due to the energy stored in the transformer 1, a voltage is induced in the secondary winding S1 of the transformer 1. This voltage is rectified through the rectifying and smoothing circuit 11, and the DC voltage on the system body side is
/ DC converter 6. And DC / DC
The power is supplied to the system controller 7 of the system main body by the converter 6, and the voltage is increased or decreased to a desired voltage at a plurality of driving points and supplied to the load 8.

The error detection and amplification circuit 4 includes a rectifying and smoothing circuit 11
, And outputs it to the P
This is fed back to the WM control circuit 2. By this feedback, the duty of the pulse signal from the PWM control circuit 2 is automatically adjusted so that the output voltage Vo approaches a predetermined target value. This stabilizes the output voltage Vo of the power supply.

In the circuit shown in FIG.
Is provided in order to reduce a surge voltage generated in the primary winding P1 of the transformer 1 at the moment when the switching element Q1 changes from on to off. Another snubber circuit 15 is provided to reduce switching noise generated by the diode D2 of the rectifying and smoothing circuit 11.

Here, assuming that the voltage of the DC power supply 9 and the magnitude of the load 8 are constant, both the snubber circuits 14 and 15 generate an energy loss that is substantially proportional to the frequency of the switching element Q1. Also, the switching element Q1
Also during switching operation (on / off, off / on)
With an energy loss roughly proportional to the switching frequency. In order to reduce this loss, the present switching power supply has a function of lowering the switching frequency.

That is, in the circuit of FIG. 3, the system controller 7 applies the "H" level of the frequency switching signal CH to the signal input terminal 12 during a standby time when the system body does not require power. Thus, the frequency switching circuit 13 is controlled via the photocoupler 16, the switching frequency is reduced, the loss of the switching power supply is reduced, and the conversion efficiency is increased (see FIG. 4).

As described above, in the above conventional example, the system controller 7 controls the frequency switching signal CH on / off to lower the switching frequency during system standby and reduce the power loss inside the power supply during system standby. I have.

Japanese Patent Application Laid-Open No. 7-170729 discloses a circuit substantially similar to the switching power supply device shown in FIG.

[0018]

However, in the above-mentioned conventional switching power supply device, the switching frequency is reduced during standby of the system, the switching loss per unit time of the power supply device is reduced, and the conversion efficiency is increased.
DC / DC converter 6 on the actual machine connected as a system
Has not been able to reduce the loss of the entire system, including

The present invention has been made in view of the above-mentioned conventional problems, and in addition to reducing power loss during standby, unnecessary power consumption of the system body during standby can be significantly reduced, and a control method therefor. The purpose is to provide.
Another object is to provide an electronic device using the power supply device.

[0020]

In order to achieve the above object, in the power supply device according to the present invention, the first power for the actual operation mode of the electronic device is supplied to the first load of the electronic device. A power supply unit having a first power output unit that supplies a second power for a standby mode of the electronic device to a second load unit of the electronic device; In the standby mode, there is provided a power cutoff unit for cutting off the first power supplied to the first load.

In the power supply according to the second aspect of the present invention,
A transformer having a primary winding and first and second secondary windings; switching means for switching power input to the primary winding of the transformer; and a frequency substantially constant based on an output of the transformer. A power supply device comprising: a control circuit that oscillates a pulse signal and controls a switching operation of the switching unit by the pulse signal; and a frequency switching unit that switches a frequency of the pulse signal in at least two stages according to an external control signal. In addition, a power cutoff means for cutting off the power output from the first secondary winding in accordance with the external control signal is provided.

In the power supply according to the third aspect of the present invention,
3. The power supply device according to claim 2, wherein the first secondary winding supplies first power for an actual operation mode of the electronic device to a first load, and the second secondary winding includes: A second power for standby mode of the electronic device is supplied to a second load, and the external control signal is a control signal input from the second load.

In the power supply according to the fourth aspect of the present invention,
4. The power supply device according to claim 3, wherein the external control signal is a signal for identifying a standby mode / actual operation mode of the electronic device, and wherein the power cutoff unit is configured to switch the electronic device during a standby mode of the electronic device. The first power supplied to the first load is shut off.

According to a fifth aspect of the present invention, there is provided a power supply device comprising:
5. The power supply device according to claim 4, wherein the frequency switching means switches the frequency of the pulse signal to a lower one in a standby mode of the electronic device.

In the electronic device according to the present invention,
A power supply device having a first power output unit for outputting the first power, and a second power output unit for outputting the second power, and a first power supply to which the first power is supplied in an actual operation mode In an electronic device including a load and a second load to which the second power is supplied in a standby mode, a power supply that cuts off the first power supplied to the first load in the standby mode It is characterized in that a blocking means is provided.

In the electronic device according to the present invention,
A transformer having a primary winding and first and second secondary windings; switching means for switching power input to the primary winding of the transformer; and a frequency substantially constant based on an output of the transformer. A power supply device that oscillates a pulse signal and controls a switching operation of the switching unit by the pulse signal, and a frequency switching unit that switches a frequency of the pulse signal in at least two stages according to the control signal, An electronic apparatus having first and second loads to which first and second powers are respectively supplied from the first and second secondary windings of the power supply device, wherein the first and second loads are provided. Power supply shutoff means for interrupting power output from the next winding to the first load in accordance with the control signal is provided.

In the electronic device according to the present invention,
8. The electronic device according to claim 7, wherein the control signal is a control signal generated by the second load.

In the electronic device according to the ninth aspect,
9. The electronic device according to claim 8, wherein the control signal is a signal for identifying a standby mode / actual operation mode, and the power cutoff unit is supplied to the first load in a pre-standby mode. The first power supply is shut off.

According to a tenth aspect of the present invention, in the electronic device according to the ninth aspect, the frequency switching means switches the frequency of the pulse signal to a lower frequency in the standby mode. Features.

[0030] In the power supply device control method according to the eleventh aspect of the present invention, a first power output unit that supplies a first power to a first load unit of the electronic device when the electronic device is in an actual operation mode; A second power output unit that supplies a second power to the second load unit of the electronic device in a standby mode of the electronic device. And shutting off the first power supplied to the first load in the standby mode.

[0031]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a configuration of a switching power supply according to an embodiment of the present invention. In FIG. 1, components common to those in the conventional example shown in FIG. The differences from the example will be mainly described.

In this embodiment, the conventional circuit shown in FIG. 3 is provided with an output terminal 19 for supplying power Vo2 for the system controller 7, and for supplying power Vo1 for DC / DC6 of the system main body (for example, a printer). An output on / off circuit 18 is added to the output terminal 17 line.

The output terminal 19 is an output terminal for driving only the system controller 7 on the main body side. Therefore, a rectifying / smoothing circuit including a diode D3 and a capacitor C2 is connected to the secondary winding S2 of the transformer 1. I have. Further, the output terminal 17 is connected to the DC / DC converter 6 on the main body side. The DC / DC converter 6 converts the output voltage Vo1 of the switching power supply into a desired voltage to be supplied to the load 8 (a drive circuit other than the system controller 7).

Further, a signal input terminal 12 is connected to the system controller 7. The signal input terminal 12
A frequency switching signal CH supplied from the system controller 7 to the frequency switching circuit 13 is applied.

The output on / off circuit 18 connected to the DC / DC converter output terminal 17 is a P-type MOS-FE
TQ2 (hereinafter simply referred to as transistor Q2), resistor R
1, R2, R3, and a PNP transistor Q3. The source of the transistor Q2 is a rectifying and smoothing circuit 1.
1, the drain is connected to the DC / DC converter output terminal 17 on the main body side, the resistor R1 is connected between the gate and the source of the transistor Q2, and the resistor R2 is connected to the gate of the transistor Q2 and the collector of the transistor Q3. Have been. The base of the transistor Q3 is connected to the photocoupler 16, is connected to the signal input terminal 12 via the base current limiting resistor R3, and the emitter is connected to the ground.

Next, the circuit operation of this embodiment will be described.

In this embodiment, for example, it is assumed that the "H" level is a 5V signal and the "L" level is a 0V signal.

The system controller 7 determines whether the system body is in standby or in actual operation, and switches the oscillation frequency of the switching power supply. That is, as shown in FIG. 2, during the actual operation of the system body, the system controller 7 applies an “L” level frequency switching signal CH to the signal input terminal 12 as a signal indicating the actual operation. Then, the transistor Q3 of the output on / off circuit 18 has:
A base bias is applied via the resistor R3, and as a result, the transistor Q3 is turned on, and the gate of the transistor Q2 is biased by the voltage division of the resistors R1 and R2. As a result, the transistor Q2 is turned on, and Vo is supplied to the main body side DC / DC converter 6 via the output terminal 17.
1 power.

In this operation, since the frequency switching signal CH is at the "L" level, the oscillation state of the OSC 3 is in a high frequency state, and the switching frequency of the switching power supply is high (see FIG. 2).

On the other hand, when the system main unit is on standby, the system controller 7 applies an "H" level signal to the signal input terminal 12 as a signal indicating the standby state. Then, the base bias is not applied to the transistor Q3, the transistor Q3 is turned off, and the gate bias of the transistor Q2 is not applied, so that the transistor Q2 is turned off. As a result, DC / DC on the system body side
Power supply to converter 6 is cut off. This allows
Since the power loss of the DC / DC converter 6 during standby becomes zero, the power loss of the entire system is reduced.

Since the frequency switching signal CH is at the "H" level during this standby, the oscillation state of the OSC 3 is in a low frequency state, and the switching frequency of the switching power supply is reduced (see FIG. 2).

As described above, in the present embodiment, the switching frequency of the switching power supply is switched by the system controller 7 as necessary, so that the power loss of the switching power supply is reduced. The power to the DC / DC converter 6 that supplies power to the load 8 on the
It can be shut off by the OFF circuit 18. Thereby, the power loss of the switching power supply device and the DC / DC converter 6 on the main body side can be reduced, and the power consumption of the entire system can be reduced.

[0044]

As described in detail above, according to the present invention,
Since the power loss of the power supply device and the electronic device body during the standby mode can be reduced, the power consumption of the entire electronic device can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a switching power supply according to an embodiment of the present invention.

FIG. 2 is a time chart showing signals of the switching power supply device of the embodiment.

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

FIG. 4 is a time chart showing signals of a conventional switching power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transformer 2 PWM control circuit 3 Triangular wave generator 4 Error detection amplifier circuit 5, 16 Photocoupler 5 DC / DC converter 6 System controller 7 Load 8 DC power supply 9 Start-up resistor 10 Rectifying smoothing circuit 11 Signal input terminal 12 Frequency switching circuit 14, Reference Signs List 15 snubber circuit 13 output terminal for DC / DC converter 14 output on / off circuit 15 output terminal for system controller P1 primary winding P2 control winding S1, S2 secondary winding Q1 switching element Q2 P-type MOS-FFT Q3 PNP Transistor

Claims (11)

[Claims] 1. A first power output unit for supplying a first power for an actual operation mode of an electronic device to a first load unit of the electronic device, and a second power for a standby mode of the electronic device. And a second power output unit that supplies the first load to the second load unit of the electronic device, wherein in the standby mode, the first power supplied to the first load is shut off. A power supply device comprising means. 2. A transformer having a primary winding and first and second secondary windings, switching means for switching power input to the primary winding of the transformer, and an output of the transformer. A control circuit that oscillates a pulse signal having a substantially constant frequency, controls the switching operation of the switching means by the pulse signal, and frequency switching means that switches the frequency of the pulse signal in at least two stages according to an external control signal. A power supply device comprising: a power supply cutoff unit that cuts off power output from the first secondary winding in accordance with the external control signal. 3. The first secondary winding supplies a first power for a real operation mode of an electronic device to a first load, and the second secondary winding supplies a first power to the electronic device. The power supply device according to claim 2, wherein the second power for standby mode is supplied to a second load, and the external control signal is a control signal input from the second load. 4. The external control signal is a signal for identifying a standby mode / actual operation mode of the electronic device, and the power cut-off means applies a signal to the first load when the electronic device is in a standby mode. The power supply device according to claim 3, wherein the supplied first power is cut off. 5. The power supply device according to claim 4, wherein the frequency switching unit switches the frequency of the pulse signal to a lower frequency in a standby mode of the electronic device. 6. A power supply device having a first power output unit for outputting a first power, and a second power output unit for outputting a second power, and the first power is supplied in an actual operation mode. An electronic device including a first load to be supplied and a second load to which the second power is supplied in a standby mode, wherein the first load supplied to the first load in the standby mode An electronic device comprising a power cutoff unit for cutting off power. 7. A transformer having a primary winding and first and second secondary windings, switching means for switching electric power input to the primary winding of the transformer, and an output of the transformer. A control circuit that oscillates a pulse signal having a substantially constant frequency and controls the switching operation of the switching means with the pulse signal; and frequency switching means for switching the frequency of the pulse signal in at least two stages according to the control signal. An electronic device having a power supply device, and first and second loads to which first and second powers are respectively supplied from the first and second secondary windings of the power supply device, An electronic apparatus, further comprising: a power cutoff unit that cuts off power output from the first secondary winding to the first load in accordance with the control signal. 8. The electronic device according to claim 7, wherein the control signal is a control signal generated by the second load. 9. The control signal is a signal for identifying a standby mode / actual operation mode, and the power cutoff unit includes
9. The system according to claim 8, wherein the first power supplied to the first load is cut off in the pre-standby mode.
Electronic device as described. 10. The electronic device according to claim 9, wherein the frequency switching means switches the frequency of the pulse signal to a lower frequency in the standby mode. 11. A first power output unit that supplies a first power to a first load unit of the electronic device when the electronic device is in an actual operation mode, and supplies a second power when the electronic device is in a standby mode. For a power supply device having a second power output unit for supplying to a second load unit of the electronic device, the electronic device determines whether the electronic device is in an actual operation mode / standby mode. A method for controlling a power supply device, comprising shutting off the first power supplied to a load.