JP2001045752A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply that is low-cost, that saves space and capable of reducing power consumption. SOLUTION: An FET 51 is a P-channel FET, and its source is connected to the cathode of a diode 16 and its drain to an electrolytic capacitor 20 respectively. By turning on a transistor 54 in accordance with a 24V-interrupting signal from an engine controller, a current is caused to flow into are a resistor 53, so that the FET 51 goes into a conducting state. Conversely, by turning off the transistor 54 in accordance with the 24V-interrupting signal, the current flow into the resistor 53 is shut, so that the FET 51 is put into a non-conducting state via a resistor 52. As a result, low-cost electrolytic capacitors can be used, because no excessive voltage is impressed on the electrolytic capacitors 20 and 35, at this interruption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for supplying a plurality of different output voltages to a load, and more particularly to a power supply device having a function of interrupting power supply to a load for saving energy.

[0002]

2. Description of the Related Art Conventionally, a power supply device applied to, for example, a printer generally has two different power supplies, a power supply voltage for driving an engine such as a motor (for example, 24 V) and a power supply voltage for controlling an engine (for example, 5 V). It is configured to generate a voltage.

Recently, it has been recommended to reduce the power consumption of the printer when it is not operating (at the time of standby). This power supply device is designed to reduce the power consumption at the time of standby.
It has a function to cut off the supply of power supply voltage to unnecessary loads during standby.

FIG. 4 is an electric circuit diagram showing an example of an electric circuit of the conventional power supply device.

In FIG. 1, a power supply voltage supplied from an AC (AC) power supply 1 is full-wave rectified by a diode bridge circuit 2 and smoothed by a smoothing capacitor 3.

The power control IC 4 is started by the start resistors 5 and 6 of the power control IC 4, and after the start, controls on / off of an FET (field effect transistor) 7.

When the FET 7 is on, the main winding 2
7 is supplied to the auxiliary winding 29 when the FET 7 is turned off, and a voltage is applied to the auxiliary winding 29. The applied voltage is released by the diode 9 and the capacitor 8, and becomes an auxiliary power supply for the power supply control IC 4 after the power supply is started.

When the FET 7 is off,
A winding for outputting a power supply voltage of 24 V (hereinafter, referred to as a winding)
The capacitor 20 is charged by the voltage applied to the “24V winding” 28 via the diode 16 and smoothed by the filter circuit including the coil 34 and the capacitor 35.

Further, when the FET 7 is off,
A winding for outputting a power supply voltage of 5 V (hereinafter referred to as “5
The capacitor 21 is charged by the voltage applied to the “V winding” 29 via the diode 18 and is smoothed by the filter circuit including the coil 36 and the capacitor 37.

The shunt regulator 24 divides the voltage of 5 V by feedback resistors 25 and 26 and a reference voltage (re
A current is passed from the cathode to the anode such that f) is equal.

A voltage limiting resistor 23 is connected to the light emitting portion of the photocoupler 24. When a current flows through the light emitting portion of the photocoupler 24, the light receiving portion is turned on, and the power control IC
Current flows out of the feedback (FB) terminal 12. In response to this current, the power supply control IC 12
The duty of the on / off time is controlled to stabilize the power supply.

The P-channel FET 51 is for cutting off the supply of the power supply voltage to the 24 V system load.

By turning on the transistor 54 in accordance with a 24 V cutoff signal from an engine controller (not shown), a current flows through the resistor 53 and the FET 51 is turned on. On the other hand, according to the 24V cutoff signal, the transistor 54
Is turned off, the current flowing through the resistor 53 is cut off, and the FET 51 is turned off via the resistor 52.

[0014]

However, in the above-mentioned conventional power supply device, by setting the FET 51 to a non-conductive state, the two
If the supply of the power supply voltage to the 4V system load is cut off, the power supply voltage rises out of the control range, so that the electrolytic capacitor 2
There is a possibility that 0 and 35 may be destroyed.

To cope with this, (1) the electrolytic capacitors 20 and 35 and the like must have a high withstand voltage;
(2) There are two methods of adding a dummy load 60 (see FIG. 4) that does not cause the power supply voltage to deviate from the control range.

However, in the above method (1), it is necessary to use an expensive and large-sized electrolytic capacitor or the like having a high withstand voltage. There were adverse effects such as an increase in the substrate area.

Further, the method (2) has a disadvantage that the original power consumption cannot be reduced due to power consumption by the dummy load.

The present invention has been made in view of this point, and it is an object of the present invention to provide a power supply device which can reduce power consumption at low cost and space.

[0019]

According to a first aspect of the present invention, there is provided a power supply device for outputting at least a low voltage output terminal for outputting a low voltage and a high voltage to a secondary side of a transformer. A plurality of output terminals including a high voltage output terminal for intermittently supplying current to the primary side of the transformer, thereby supplying power to each load from the low voltage output terminal and the high voltage output terminal. In a power supply device for supplying a voltage, a plurality of rectifiers for respectively rectifying the voltage applied to each of the output terminals, a smoothing unit including at least a smoothing capacitor for smoothing each of the rectified voltages, Of the multiple output terminals,
Interrupting means for interrupting at least supply of a voltage applied to the high-voltage output terminal to a load, wherein the interrupting means is disposed in front of the smoothing means, and when the power supply voltage is interrupted to the load, An excessive voltage is prevented from being applied to the smoothing capacitor of the smoothing means.

According to a second aspect of the present invention, there is provided a power supply device comprising a plurality of low-voltage output terminals for outputting at least a low voltage and a high-voltage output terminal for outputting a high voltage on a secondary side of the transformer. By providing an output terminal and intermittently supplying current to the primary side of the transformer, a power supply voltage is directly supplied to the load from the low voltage output terminal, and the power supply voltage applied to the high voltage output terminal is In a power supply device that supplies a load after a predetermined base potential is added, a plurality of rectifiers for rectifying the voltages applied to the respective output terminals, and for smoothing the rectified voltages, A smoothing means including at least a smoothing capacitor; and a shutoff means for interrupting supply of a voltage applied to at least the high-voltage output terminal to a load among the plurality of output terminals, Stage, the disposed between the transformer and the base potential, during interruption of the load of the power supply voltage, wherein the excessive voltage to the smoothing capacitor of the smoothing means was not applied.

[0021] Preferably, the base potential is generated based on a voltage applied to the low voltage output terminal.

Further, preferably, the shut-off means includes any one of a field-effect transistor, a transistor, a relay, and a switch.

[0023]

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

FIG. 1 is an electric circuit diagram of the power supply device according to the first embodiment of the present invention. 4, the same components as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

The power supply device of the present embodiment is different from the conventional power supply device mainly in that an FET 51 is arranged between the rectifier diode 16 and the electrolytic capacitor 20.

That is, in FIG.
The source is connected to the cathode of the diode 16, and the drain is connected to the electrolytic capacitor 20.

Then, 24 from the engine controller
By turning on the transistor 54 in accordance with the V cutoff signal, a current flows through the resistor 53 and the FET 51 is turned on. On the other hand, by turning off the transistor 54 in accordance with the 24V cutoff signal, the current flowing through the resistor 53 is cut off, and the FET 51 is turned off via the resistor 52. At the time of the cutoff, an excessive voltage is not applied to the electrolytic capacitors 20 and 35, so that an inexpensive electrolytic capacitor can be used.

In order to operate the FET 51 more stably, a small-capacity ceramic capacitor 61 may be added between its source and ground (GND).

Further, in the present embodiment, a P-channel FET has been described as an example of an element for interrupting supply of a power supply voltage to a 24 V system load, but the present invention is not limited to this.
The present invention can be realized by a circuit using a channel FET.

FIG. 2 is an electric circuit diagram showing an example of a power supply device using this N-channel FET.

Referring to FIG.
By using a PNP transistor and applying or not applying a 5V voltage to the gate, the FET 6
Turn 3 on / off.

In addition, a device other than an FET, for example, a transistor, a relay, a switch, or the like may be used as the blocking element.

Next, a power supply device according to a second embodiment of the present invention will be described.

FIG. 3 is an electric circuit diagram of the power supply device of the present embodiment. 4, the same components as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

The power supply device of the present embodiment is different from the power supply device of the first embodiment in that a power supply voltage of 5 V is added to generate a power supply voltage of 24 V.

In FIG. 3, a P-channel FET 51 is
The source is set to a potential of 5V, and the drain is set to the transformer 28.
These 5 V potentials are opened and closed to make them conductive or non-conductive.

With this configuration, similarly to the first embodiment, since an excessive voltage is not applied to the electrolytic capacitors 20 and 35, an inexpensive electrolytic capacitor can be used.

The blocking element is a P-channel FE
In addition to T, N-channel FETs, transistors, relays,
A switch or the like can be used.

[0039]

As described above, according to the first aspect of the present invention, of the plurality of output terminals provided in the transformer, at least the voltage applied to the high voltage output terminal is supplied to the load. The interrupting means for interrupting is arranged in front of the smoothing means including at least a smoothing capacitor, in order to respectively smooth each voltage rectified by the plurality of rectifying means for rectifying the voltage applied to each of the output terminals,
When the power supply voltage is cut off to the load, an excessive voltage is not applied to the smoothing capacitor of the smoothing means, so that an inexpensive smoothing capacitor can be used.
Power consumption can be reduced with low cost and space saving.

According to the second aspect of the present invention, of the plurality of output terminals provided on the transformer, at least the interruption means for interrupting the supply of the voltage applied to the high voltage output terminal to the load is provided. It is arranged between the transformer and the base potential, and when a power supply voltage is cut off to a load, an excessive voltage is not applied to the smoothing capacitor of the smoothing means. it can.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a power supply device according to a first embodiment of the present invention.

FIG. 2 is an electric circuit diagram of a modified example of the power supply device of FIG.

FIG. 3 is an electric circuit diagram of a power supply device according to a second embodiment of the present invention.

FIG. 4 is an electric circuit diagram of a conventional power supply device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 AC power supply 2 Rectifier diode 4 Power supply control IC 20 Electrolytic capacitor 35 Electrolytic capacitor 51 FET 54 Transistor 59 Photocoupler

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayasu Toyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Takazawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Akihiro Shibata 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term (reference) 5H730 AA20 AS01 AS23 BB43 BB57 CC01 DD04 DD26 EE07 EE08 EE19 EE73 FD01 FF19 VV03 VV06 XC20

Claims (4)

[Claims] 1. A secondary side of a transformer is provided with a plurality of output terminals including at least a low voltage output terminal for outputting a low voltage and a high voltage output terminal for outputting a high voltage,
A power supply device for supplying a power supply voltage to each load from the low-voltage output terminal and the high-voltage output terminal by intermittently supplying a current to the primary side of the transformer; A plurality of rectifiers for rectifying the respective voltages; a smoother including at least a smoothing capacitor for smoothing each of the rectified voltages; applied to at least the high-voltage output terminal among the plurality of output terminals; Interrupting means for interrupting the supply of the voltage to the load, wherein the interrupting means is arranged before the smoothing means, and when the power supply voltage is interrupted to the load, an excessive voltage is applied to the smoothing capacitor of the smoothing means. A power supply device, wherein a voltage is not applied. 2. A plurality of output terminals including a low voltage output terminal for outputting at least a low voltage and a high voltage output terminal for outputting a high voltage are provided on a secondary side of the transformer,
By supplying current intermittently to the primary side of the transformer, a power supply voltage is directly supplied from the low voltage output terminal to the load, and a power supply voltage applied to the high voltage output terminal is supplied with a predetermined base potential. And a plurality of rectifying means for rectifying the voltage applied to each of the output terminals, and at least a smoothing capacitor for smoothing each of the rectified voltages. A smoothing unit; and a cutoff unit that cuts off supply of a voltage applied to at least the high-voltage output terminal to a load among the plurality of output terminals, wherein the cutoff unit includes the transformer and the base potential. A power supply device, wherein an excessive voltage is not applied to the smoothing capacitor of the smoothing means when the power supply voltage is cut off to the load. 3. The power supply device according to claim 2, wherein the base potential is generated based on a voltage applied to the low voltage output terminal. 4. The power supply device according to claim 1, wherein said cut-off means includes any one of a field-effect transistor, a transistor, a relay, and a switch.