JP2002101662A - Power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently and inexpensively shut off voltage supply in a switching power supply device generating a plurality of voltages with one transformer having a plurality of secondary windings. SOLUTION: A P channel MOSFET is used as an element to shut off the output of the maximum voltage, an N channel MOSFET is used for control circuit drive as an element to shut off the output of the voltage except for the maximum voltage, the drain of the P channel MOSFET is connected to a load side and the gate of the N channel MOSFET, and the source of the N channel MOSFET is connected to the load side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a power supply device,
In particular, the present invention relates to a power supply device capable of outputting a plurality of voltages.

[0002]

2. Description of the Related Art [First Prior Art] Conventionally, a power supply device mounted on an image recording apparatus is configured to be capable of outputting a plurality of voltages. That is, this type of power supply, for example,
2. for driving a control circuit or the like constituted by a CPU or the like;
A low voltage such as 3 V, a medium voltage such as 5 V for driving various drivers such as a laser and a motor, and a high voltage such as 24 V for driving a load with a large power consumption such as a motor and a solenoid are output. It is configured.

[0003] The image recording apparatus drives the load with all of the above output voltages when performing image recording, but various drivers that are driven at a medium voltage such as 5 V when not performing image recording. Motors, solenoids, and the like that are driven by a large voltage such as 24 V are not driven.

However, these loads consume a small amount of power including peripheral load circuits even if they are not driven. Therefore, due to recent demands for energy saving of electric devices, it is considered that supply of a medium voltage such as 5 V or a large voltage such as 24 V is cut off when image recording is not performed.

FIG. 18 shows a conventional power supply circuit having a voltage supply cutoff function. This power supply device is a flyback switching power supply device having a 3.3 V, 5 V
V and 24V can be output.

In FIG. 18, T301 is an insulating transformer, and a current is intermittently supplied by an N-channel MOSFET Q301. When the MOSFET Q301 is turned on / off by a power supply control circuit (not shown), the output voltage becomes a predetermined value (here, 3.3V, 5V,
24V).

[0007] The insulating transformer T301 can output three voltages. The rectifying element D301 and the capacitor C301, respectively, and the rectifying element D302 and the capacitor C30.
2. Rectification and smoothing are performed by the rectifying element D303 and the capacitor C303, and an output voltage of 24V, 5V, and 3.3V is obtained.

The 24 V load shedding circuit is a P-channel MO
The 5V load cutoff circuit, which is constituted by the SFET Q302, the resistors R301 and R302, and the transistor Q304,
P-channel MOSFET Q303, resistors R303, R3
04, a transistor Q305. A load shedding signal controlled by a control circuit (not shown) operating at 3.3 V is input to the bases of the transistors Q304 and Q305. If the load shedding signal is high, the transistors Q304 and Q305 are turned on. The MOSFETs Q302 and Q303 conduct, and the load
A voltage of 4V and 5V is supplied. On the other hand, if the load shedding signal is Low, the transistors Q304 and Q305
As an FF, the MOSFETs Q302 and Q303 are cut off, and the 24V and 5V voltage supply is cut off.

[Second Prior Art] FIG. 19 is a circuit diagram of a conventional two-converter power supply device, in which a converter for 24 V output constitutes a main power supply, and a converter for 3.3 V output constitutes a sub power supply. . Both the main power supply and the sub power supply are flyback power supplies that control output voltage by a PWM method.

In a main power supply for 24V output, AC
The input voltage from the input unit is full-wave rectified by the diode bridge 301 and smoothed by the smoothing capacitor 302. 30
Reference numeral 3 denotes a power control IC, which is activated by start resistors 304 and 305 for the power control IC. After power on,
The power control IC 303 turns ON / OFF the FET 306
Perform control. When the FET 306 is ON, the transformer 307
The excitation current flows through the primary winding 307a of the first and second magnetic fields to generate magnetic flux, thereby storing energy in the transformer 307.

Since the auxiliary winding 307b has the same polarity as the primary winding 307a, the voltage generated at this time is
08 and a voltage rectified and smoothed by the capacitor 309 is supplied as a power supply voltage. Since the polarity of the secondary winding 307s of the transformer 307 is reversed in the secondary-side diode 310, energy is not transmitted to the secondary side.

When the FET 306 is turned off, the secondary winding 3
Since the voltage of 07s is inverted, the diode 310 is turned on.
Then, energy is taken out to the secondary side by supplying current to the capacitor 311.

Reference numeral 312 denotes a shunt regulator, and a current flows from the cathode to the anode so that the voltage divided by the feedback resistors 313 and 314 is equal to the reference voltage of the shunt regulator 312. 315 is a current limiting resistor, and 316 is a photocoupler. When a current flows from the cathode to the anode of the shunt regulator 312 and the current flows to the light emitting unit of the photocoupler 316, the light receiving unit is turned on, and the power control IC 30
A current flows out of the feedback terminal (FB) 3.
In response to this current, the power control IC 303
And stabilizes the output voltage. A relay 317 is arranged between the AC input section of the main power supply and the diode bridge 301.

The sub-power supply for 3.3 V operates on the same principle as that of the main power supply, and a description thereof will be omitted.

The CPU 318 is supplied with power from a 3.3V output sub power supply, and the voltage divided by the resistors 319 and 320 is applied to the base of the transistor 321. The collector of the transistor 321 is connected to one end of the relay 317. The other end of the relay 317 is connected to the 3.3V output of the sub power supply.

When the output of the CPU 318 is High,
The voltage divided into the resistors 319 and 320 is applied to the base of the transistor 321, and the transistor 321 is turned on by supplying the current, the relay 317 is turned on, and the main electric wire operates.

On the other hand, when the output of the CPU 318 is Low, no current is supplied to the base of the transistor 321, so that the transistor 321 is not turned on and the relay 317 is not turned on.
, The main power supply stops operating.

[Third Prior Art] In a power supply device having a plurality of output voltages, as described in the first prior art, an undriven load also consumes some power.

In the case where a plurality of outputs are output by one insulating transformer, the output of a large voltage such as 24 V and a low voltage such as 3.3 V depends on the specification of the winding and the type of power supply. Depending on the load balance, for example, a dummy resistor for supplying a dummy current to an output stage of a large voltage such as 24 V is provided, and a required minimum load current is not consumed by the dummy resistor to satisfy a desired output voltage cross regulation. There are many cases where it is not possible.

These states cause an increase in power consumption in the power saving mode of the apparatus. Therefore, due to recent demands for energy saving of electric equipment, when image recording is not performed, medium voltage such as 5V, 24
A power supply device as shown in FIG. 20 that cuts off output including a large voltage such as V and a dummy resistor has been considered.

The power supply shown in FIG. 20 is a flyback type switching power supply, and is 3.3 V, 5 V, and 24 V.
Can be output.

In FIG. 20, reference numeral T401 denotes an insulating transformer, which is a power supply system in which an N-channel MOSFET Q401 is used as a switch element to control the on / off ratio of the switch element to adjust the flow of electric power.

When the switching element Q401 is turned on, a current flows on the primary side (S1) of the insulating transformer T401, and energy is stored in the insulating transformer T401. Next, when the switching element Q401 is turned off, no current flows on the primary side (S1) of the insulating transformer T401. At this time, the secondary side (S2, S3, S4) releases energy to the load side. The switch element Q401 is driven by a power supply control circuit (not shown), and is controlled so that the output voltage becomes a predetermined value (here, 3.3V, 5V, 24V).

The insulating transformer T401 can output three voltages. The rectifying element D401 and the capacitor C401, and the rectifying element D402 and the capacitor C40, respectively.
2. Rectification and smoothing are performed by the rectifying element D403 and the capacitor C403, and an output voltage of 24V, 5V, and 3.3V is obtained.

The 24 V load shedding circuit is a P-channel MO
The 5V load cutoff circuit, which is constituted by the SFET Q402, the resistors R401 and R402, and the transistor Q404,
P-channel MOSFET Q403, resistors R403, R4
04, a transistor Q405. Note that a dummy resistor R405 is provided in the 24V output stage.

A load cutoff signal controlled by a control circuit (not shown) operating at 3.3 V is input to the bases of the transistors Q404 and Q405. If the load cutoff signal is high, the transistors Q404 and Q40 are turned off.
5 is turned on to turn on the P-channel MOSFETs Q402 and Q402.
403 conducts, and a voltage of 24 V and 5 V is supplied to the load. On the other hand, if the load shedding signal is low, the transistors Q404 and Q405 are turned off and the P-channel MO
SFETs Q402 and Q403 are cut off, 24V, 5V
Is shut off.

[Fourth conventional example] Conventionally, there has been known a power supply device having a plurality of switching regulators as shown in FIG. 22 in order to save power in a standby mode of a device.

The power supply shown in FIG. 22 has an output of 3.3 V for operating the CPU of the IC 131 during standby of the device.
And a second switching regulator with an output of 24 V for driving a load required only during operation of the device.

The first switching regulator is a general RCC type flyback power supply, and drives the insulating transformer T111 by using the switching element FETQ111. The output voltage is divided by the resistors R115 and R116, compared by the error amplifier A111, and fed back to the primary side by the photocoupler PC111.
It is stabilized at 3V.

The second switching regulator is a PWM flyback power supply using an IC 121 as a power supply control IC. T121 is an isolation transformer, Q121
Is a switching element FET, and the output voltage is R12
5, divided by R126, compared by error amplifier A121, fed back to primary side by photocoupler PC121, and stabilized at 24V.

As a power source for driving the IC 121, an auxiliary winding of the insulating transformer T121 is connected to a diode D1.
21, a rectified and smoothed one is provided by a capacitor C121. When the operation of the present switching regulator is started, power is supplied from a commercial power supply via a resistor R121.

The pros and cons of the operation of the second switching regulator during the operation of the device and during standby are determined by the CPU in the IC 131.
And the photocoupler P is determined by the SLEEP signal.
Switching is performed by C131 depending on whether a power supply is connected to the power supply control IC 121 from the auxiliary power supply. That is, SL
If the EEP signal is High, the photocoupler PC13
1 is turned on, and the power control IC 1
Power is supplied to 21 and the second switching regulator operates. If the SLEEP signal is Low,
Phototransistor of photocoupler PC131 is OFF
And the power supply to the power supply control IC 121 is cut off.
The second switching regulator stops.

[Fifth conventional example] A power supply device having a plurality of output voltages, as described in the first and third prior arts,
Undriven loads also consume some power.

When a plurality of outputs are output by one insulating transformer, the output of a large voltage such as 24 V and a low voltage such as 3.3 V depends on the specifications of the winding and the type of power supply. Depending on the load balance, for example, a dummy resistor for supplying a dummy current to an output stage of a large voltage such as 24 V is provided, and a required minimum load current is not consumed by the dummy resistor to satisfy a desired output voltage cross regulation. There are many cases where it is not possible.

These states cause an increase in power consumption in the power saving mode of the apparatus. Therefore, due to recent demands for energy saving of electric equipment, when image recording is not performed, medium voltage such as 5V, 24
A power supply device as shown in FIG. 23 which cuts off output including a large voltage such as V and a dummy resistor has been considered.

The power supply shown in FIG. 23 is a flyback type switching power supply, and is 3.3 V, 5 V, and 24 V.
Can be output.

In FIG. 23, reference numeral T301 denotes an insulating transformer, which is a power supply system in which an N-channel MOSFET Q301 is used as a switching element to control the on / off ratio of the switching element to adjust the flow of electric power.

When the switching element Q301 is turned on, a current flows on the primary side (S1) of the insulating transformer T301, and energy is stored in the insulating transformer T301. Next, when the switch element Q301 is turned off, no current flows on the primary side (S1) of the insulating transformer T301. At this time, the secondary side (S2, S3, S4) releases energy to the load side. The switch element Q301 is driven by a power supply control circuit (not shown), and is controlled so that the output voltage becomes a predetermined value (here, 3.3V, 5V, 24V).

The insulating transformer T301 can output three voltages. The rectifying element D301 and the capacitor C301, and the rectifying element D302 and the capacitor C30, respectively.
2. Rectification and smoothing are performed by the rectifying element D303 and the capacitor C303, and an output voltage of 24V, 5V, and 3.3V is obtained.

The 24 V load shedding circuit is a P-channel MO
The 5V load cutoff circuit, which is constituted by the SFET Q302, the resistors R301 and R302, and the transistor Q304,
P-channel MOSFET Q303, resistors R303, R3
04, a transistor Q305. The 24V and 5V output stages have dummy resistors R3
10, R320.

A load cutoff signal controlled by a control circuit (not shown) operating at 3.3 V is input to the bases of the transistors Q304 and Q305. If the load cutoff signal is high, the transistors Q304 and Q30
5 turns ON, and the P-channel MOSFETs Q302, Q302
303 conducts, and a voltage of 24 V and 5 V is supplied to the load. On the other hand, if the load shedding signal is Low, the transistors Q304 and Q305 are turned off and the P-channel MO
SFET Q302, Q303 are cut off, 24V, 5V
Is shut off.

[Sixth conventional example] In a printer, a power supply voltage such as 24 V for driving an engine and a power supply voltage for controlling an engine are used.
Since a power supply voltage of 3 or the like is required, a power supply device having two converters (hereinafter, referred to as a composite power supply device) is known.

FIG. 24 is a circuit diagram of a conventional composite power supply device, which has a 3.3 V power supply (main power supply) and a 24 V power supply (sub power supply).

In FIG. 24, reference numeral 1 denotes an AC power supply, which is full-wave rectified by a diode bridge 2 and smoothed by a smoothing capacitor 3. Reference numeral 4 denotes a main power control IC, which is 3.3.
This is control 1C for generating a power supply voltage of V, and is activated by the IC start resistors 5 and 6.

When activated, the main power supply control IC 4 controls ON / OFF of the FET 7. FET7 is ON
At this time, a voltage is applied to the main winding 10 and electric power is stored in the main transformer. When the FET 7 is turned off, the energy stored in the main transformer is released through the auxiliary winding 12 and the secondary winding 11. The energy released from the auxiliary winding 12 of the main transformer is smoothed by the diode 9 and the capacitor 8, and is used as an auxiliary power supply for the main power supply control IC 4 after the main power supply is started. The energy emitted from the secondary winding 11 of the main transformer is smoothed by the diode 16, the capacitor 17, the coil 18, and the capacitor 19.

34 is a shunt regulator;
A current flows from the cathode to the anode such that the value obtained by dividing the 3V voltage by the feedback resistors 31 and 32 becomes equal to the reference voltage of the shunt regulator 34.

Reference numeral 33 denotes a current limiting resistor, and reference numeral 14 denotes a photocoupler. When a current flows through the light-emitting portion of the photocoupler 14, the light-receiving portion is turned on and the F.C. A current flows out of the portion B. The power supply control IC 4 controls the duty according to the current to stabilize the power supply.

Reference numeral 20 denotes a detection resistor for detecting a current of 3.3 V. The electromotive voltage generated by the detection resistor 20 is divided by resistors 21 to 24 and compared by a comparator 25. When the voltage is equal to or higher than a predetermined value, the transistor 28 is turned on to cause the photocoupler 29 to emit light.
Then, the voltage of the SD terminal of the power control IC 4 increases,
The oscillation of the power control 1C4 is stopped.

The 24V power supply (sub-power supply) is configured in substantially the same manner as the main power supply. However, since the sub-power supply IC 104 is supplied with power from the auxiliary power supply of the main power supply,
The sub-transformer 110 has no auxiliary winding.

Reference numeral 200 denotes an engine controller, which is driven by a main power supply and controls a printer or the like equipped with the composite power supply device, and stops the photocoupler 201 when the standby state continues for a long time. By stopping the supply of the auxiliary power to the sub power supply, the sub power supply is stopped.

[0051]

However, in the first conventional example, 3.3 V supplied to a control circuit such as a CPU is used.
N-channel MOSFET to cut off supply of medium voltage such as 5V and high voltage such as 24V to load at low voltage such as
Cannot be driven, and P-channel MOSF
ET had to be used.

In general, a P-channel MOSFET has a high on-resistance, so that a loss during load conduction becomes large, causing problems such as heat generation, reduction in efficiency, and reduction in output voltage accuracy.

Also, the P ground MOSFET is disadvantageous in cost because of its high price.

In the second conventional example, it is necessary to use a relay and two AC input units are required, so that it has been difficult to reduce the size of the device.

In the third conventional example, switching means for turning on / off unnecessary output voltages in a power saving mode among a plurality of output voltages at a stage preceding all loads including a secondary-side dummy resistor is provided. When the output voltage that was turned off during the power saving mode is turned on during the operation of the device, the energy stored in the transformer T401 when the load is cut off is released as a voltage and current to the control circuit at the same time that the cutoff circuit is turned on. At the start, the control circuit for the output voltage and the dummy resistor are still in a cut-off state, and as shown in FIG. 21, the control voltage becomes normal due to the feedback operation from the output voltage control circuit or the consumption of energy by the dummy resistor. By the time, a voltage higher than the target voltage may be generated.

Applying a voltage higher than the target voltage to the control circuit components on the secondary side as it is not only impairs the reliability of the control circuit components but also may damage the control circuit components. In order to cope with this, conventionally, expensive parts having high withstand voltage were used, so that the cost was increased.

In the fourth conventional example, it was not possible to cope with a wide range of commercial power supply voltage. For example, the commercial power supply voltages in Japan, North America, and Mexico are 100 V and 12 V, respectively.
0V and 127V, and it is necessary to correspond to about 90V to 140V in consideration of the fluctuation of the commercial power supply voltage. However, in the fourth conventional example, the resistors R121 and R121 shown in FIG.
Since the drive voltage of the power supply control IC at the start of operation is determined by the voltage division of R128, it was not possible to cope with a commercial power supply voltage of about 90V to 140V.

The fifth conventional example has the same problem as the third conventional example.

In the sixth conventional example, the number of elements is large, so that the cost is increased and it is difficult to reduce the size.

The present invention has been made under such a background, and a first object of the present invention is to provide a switching power supply device that generates a plurality of voltages by using a single transformer having a plurality of secondary windings. An object of the present invention is to make it possible to cut off voltage supply efficiently and inexpensively.

A second object is to reduce the size of a multi-output power supply device including a plurality of converters for generating a DC voltage from a commercial power supply.

A third problem is that, in a switching power supply device that generates a plurality of voltages by one transformer having a plurality of secondary windings, the instantaneous output voltage when the interruption of the voltage supply is released. It is to make it possible to suppress a significant rise.

A fourth object of the present invention is to provide a multi-output power supply device including a plurality of converters for generating a DC voltage from a commercial power supply, which can cope with a plurality of commercial power supply voltages.

[0064]

In order to solve the above-mentioned first problem, the present invention provides a switching power supply that generates a plurality of voltages by using a single transformer having a plurality of secondary windings. A P-channel MOSFET is used as an element for cutting off the output, and an N-channel MOSFET is used as an element for driving the control circuit and for cutting off the output of a voltage other than the maximum voltage. The drain of the P-channel MOSFET is connected to the load side and the N-channel MOSFET. The source of the N-channel MOSFET is connected to the load side.

In order to solve the second problem, the present invention relates to a multi-output power supply device comprising a plurality of converters for generating a DC voltage from a commercial power supply, wherein the multi-output power supply stops operating during standby. It has a first switching power supply and a second switching power supply that does not stop operating in a standby state. The transformer of the second switching power supply has a primary winding and a secondary winding for obtaining a desired output voltage. An auxiliary winding, and supplies a voltage of the auxiliary winding to each drive control circuit that drives and controls each switching element of the first and second switching power supplies.

According to another aspect of the present invention, there is provided a switching power supply for generating a DC voltage from a commercial power supply, the switching circuit including a switching element for individually interrupting the output of the plurality of voltages to a load. And a filter is provided downstream of the switching element of the shutoff circuit.

According to a fourth aspect of the present invention, there is provided a multi-output power supply apparatus comprising a plurality of switching regulators for generating a DC voltage from a commercial power supply, wherein the multi-output power supply stops operating during standby. And a second switching regulator that does not stop operating during standby. A rectifying / smoothing including a Zener diode in addition to the primary winding is provided on the input side of the transformer of the second switching regulator. A circuit is provided with an auxiliary winding, and a voltage from the auxiliary winding and the rectifying / smoothing circuit is supplied to a drive control circuit that drives and controls each switching element of the first switching regulator.

According to a fourth aspect of the present invention, there is provided a multi-output power supply apparatus comprising a plurality of switching regulators for generating a DC voltage from a commercial power supply, wherein the multi-output power supply stops operating during standby. A first switching regulator and a second switching regulator that does not stop operating during standby, and a rectifying / smoothing including a Zener diode in addition to a primary winding on an input side of a transformer of the first switching regulator. A circuit is provided with an auxiliary winding, and a voltage from the auxiliary winding and the rectifying / smoothing circuit is supplied to each drive control circuit that drives and controls each switching element of the first and second switching regulators. ing.

According to a third aspect of the present invention, there is provided a switching power supply for generating a plurality of voltages by using a single transformer having a plurality of secondary windings. Of the switching circuit of the switching circuit, and a capacitive element is added between the control input of the switching element and the ground.

In order to solve the second problem, the present invention relates to a multi-output power supply device comprising a plurality of converters for generating a DC voltage from a commercial power supply, wherein the multi-output power supply stops operating during standby. It has a first switching power supply and a second switching power supply that does not stop operating during standby, wherein the second switching power supply is generated by the second switching power supply, and the first and second switching power supplies are An auxiliary power supply for driving each drive control circuit for driving and controlling each switching element;
And a stop circuit for stopping supply of the auxiliary power to each of the drive control circuits when an abnormality occurs in the switching power supply.

In order to solve the second problem, the present invention relates to a multi-output power supply device comprising a plurality of converters for generating a DC voltage from a commercial power supply, wherein the multi-output power supply stops operating during standby. It has a first switching power supply and a second switching power supply that does not stop operating during standby, wherein the second switching power supply is generated by the second switching power supply, and the first and second switching power supplies are An auxiliary power supply for driving each drive control circuit for driving and controlling each switching element;
When an abnormality occurs in the switching power supply of
And a stop circuit for stopping the supply of the auxiliary power to a drive control circuit that drives and controls the switching element of the switching power supply.

[0072]

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

[First Embodiment] FIG. 1 is a circuit diagram of a power supply device according to a first embodiment of the present invention. This power supply device is constituted by a flyback type switching power supply device.

In FIG. 1, T101 is an insulating transformer, and a current intermittently flows through the N-channel MOSFET Q101. The N-channel MOSFET Q101 is driven by a power supply control circuit (not shown), and is controlled so that the output voltage becomes a predetermined value (here, 3.3V, 5V, 24V).

The right side of the insulating transformer T101 is the output side, and there are three outputs. Rectifier D101, capacitor C101, rectifier D102, capacitor C10
2. Rectification is performed by the rectifying element D103 and the capacitor C103 to obtain a predetermined output voltage.

The load interruption circuit is a P-channel MOSFET
Q102, N-channel MOSFET Q103, resistor R1
01, R102, and transistor Q104. The gate of the N-channel MOSFET Q103 is P
Connected to the drain of channel MOSFET Q102,
A load cutoff signal is connected to the base of the transistor Q104 and is controlled by a control circuit (not shown) operating at 3.3V.

If the load shedding signal is high, the transistor Q104 is turned on, and the P-channel MOSFET
Q102 conducts and N-channel MOSFET
Since a voltage is supplied to the gate of Q103, N-channel MOSFET Q103 also conducts, and power is supplied to the load.

If the load shedding signal is low, the transistor Q104 is turned off and the P-channel MOSFET
Q102 is shut off and P-channel MOSFET
Since no voltage is supplied to the drain of the TQ102, the N-channel MOSFET Q103 is also turned off,
Power to the 4V load is shut off.

Although the flyback type switching power supply has been described in the present embodiment, a similar configuration can be used in a forward type and other types of switching power supplies.

As described above, in the present embodiment, the P-channel MOSFET is used only for cutting off the load having the highest output voltage, and the N-channel MOSFET is used for cutting off loads other than those for supplying power to the control circuit.
N-channel MOSFET using channel MOSFET
Is driven by the drain output of a P-channel MOSFET, so that not only conventional problems such as heat generation, reduction in efficiency, and reduction in output voltage accuracy can be solved, but also a low-cost load shedding circuit can be realized. be able to.

[Modification of First Embodiment] FIG. 2 is a circuit diagram showing a modification of the first embodiment.
3, R204.

In FIG. 2, T201 is an insulating transformer, and a current flows intermittently by N-channel MOSFET Q201. The N-channel MOSFET Q201 is driven by a power supply control circuit (not shown), and is controlled so that the output voltage becomes a predetermined value (here, 3.3V, 5V, 24V).

The right side of the insulating transformer T201 is the output side, and there are three outputs. Rectifier D201, capacitor C201, rectifier D202, capacitor C20
2. Rectification is performed by the rectifying element D203 and the capacitor C203 to obtain a predetermined output voltage.

The load interruption circuit is a P-channel MOSFET
Q202, N-channel MOSFET Q203, resistor R2
01, R202, and transistor Q204. The gate of the N-channel MOSFET Q203 is P
Connected to the drain of channel MOSFET Q202,
A load cutoff signal is connected to the base of the transistor Q204, and is controlled by a control circuit (not shown) operating at 3.3V.

When the load shedding signal is high, the transistor Q204 is turned on, and the P-channel MOSFET
Q202 conducts and N-channel MOSFET
The voltage at the drain terminal of Q203 is connected to resistors R203 and R204.
N-channel MOSFET by voltage divided by
Q203 also conducts, and power is supplied to the load.

If the load shedding signal is low, the transistor Q204 is turned off and the P-channel MOSFET
Q202 is shut off and P-channel MOSFE
Since no voltage is supplied to the drain of the TQ 202, the N-channel MOSFET Q 203 is also turned off,
Power to the 4V load is shut off.

In this modification, the flyback type switching power supply has been described. However, a similar configuration can be used in a forward type and other types of switching power supplies.

As described above, in this modification, the P-channel MOSFET is used only for cutting off the load having the highest output voltage, the N-channel MOSFET is used for cutting off loads other than those for supplying power to the control circuit. Since the gate of the MOSFET is driven by a voltage obtained by dividing the drain output of the P-channel MOSFET by resistance, in addition to the above-described effect of the first embodiment, the output having the highest output voltage cut off by the P-channel MOSFET and the N Channel MOSFE
The difference with the output voltage cut off at T is large,
When the gate breakdown voltage of the OSFET is exceeded, the N-channel MOSFET can be driven at a gate breakdown voltage or less.

[Second Embodiment] FIG. 3 is a circuit diagram of a two-converter power supply to which a second embodiment of the present invention is applied.
The power supply for +24 V output indicates the main power supply, and the power supply for +3.3 V output indicates the sub power supply. It should be noted that both the main power supply and the sub power supply are configured by a flyback type power supply that controls the output voltage by the PWM method.

In the sub power supply for 3.3V output,
The input voltage from the input unit is full-wave rectified by the diode bridge 101 and smoothed by the smoothing capacitor 102. 10
Reference numeral 3 denotes a power control IC, which includes an IC start resistor 104,
Activated by 105.

After the power is turned on, the power control IC 103
The ON / OFF control of T106 is performed. FET106 is O
At N, an exciting current flows through the primary winding 107a of the transformer 107 to generate a magnetic flux, thereby accumulating energy in the transformer 107. Since the auxiliary winding 107b has the same polarity as the primary winding 7a, the voltage generated at this time is rectified and smoothed by the diode 108 and the capacitor 109, and supplied as the power supply voltage.

The diode 110 on the secondary side is connected to the transformer 10
No energy is transmitted to the secondary side because the secondary winding 107s of No. 7 has the opposite polarity. FET106 is O
When FF is performed, the voltage of the secondary winding 107s is inverted.
When the diode 110 is turned on and a current is supplied to the capacitor 111, energy is extracted to the secondary side.

Reference numeral 112 denotes a shunt regulator, and a current flows from the cathode to the anode so that the voltage divided by the feedback resistors 113 and 114 and the reference voltage of the shunt regulator 112 become equal.
115 is a current limiting resistor, and 116 is a photocoupler.

When a current flows from the cathode to the anode of the shunt regulator 112 and the current flows to the light emitting portion of the photocoupler 116, the light receiving portion is turned on, and the current flows out from the feedback terminal (FB) of the power supply control IC 103. The power supply control IC 103 controls the ON duty of the FET 106 in accordance with the current to stabilize the output voltage.

On the other hand, there is no auxiliary winding in the transformer 117 of the main power supply for 24V output, and power is supplied to the power supply control IC 118 from the auxiliary winding 107b of the sub power supply to the transistor 119, the resistor 120, the zener diode 121, and the capacitor. The operation is performed via a photocoupler 123 after passing through a constant voltage circuit formed by the circuit 122.

The operation of the constant voltage circuit is as follows. The constant voltage operation of the Zener diode 121 connected to the base of the transistor 119 via the resistor 120 causes the transistor 11 to operate.
Since a constant current always flows through the base of transistor 9, a constant collector current always flows through transistor 119 even when the voltage at the collector terminal of transistor 119 fluctuates, and capacitor 122 is charged with the collector current. A voltage is output.

The CPU 124 is supplied with power from a sub power supply for 3.3 V output. By setting a terminal connected to one end of the photocoupler 123 on the diode side to Low, a current is supplied to the diode side of the photocoupler 124. flow,
The transistor side of the photocoupler 123 conducts, the constant voltage generated by the constant voltage circuit is supplied to the power supply control IC 118, and the main power supply operates.

Further, by setting the terminal to High, the transistor side of the photocoupler 123 is cut off, the supply of power to the power supply control IC 118 is cut off, and the main power supply is stopped. The resistor 125 has a function of limiting a current flowing through the diode of the photocoupler 123.

In the first embodiment, the constant voltage circuit is a transistor,
Although the configuration is made up of a zener diode, a resistor, and a capacitor, other configurations may be used. Further, the system of the main power supply and the sub power supply is not limited to the flyback system, but may be a forward system or another system.

As described above, in the second embodiment, regarding the ON / OFF control of the main power supply having a plurality of converters and operating only the sub power supply during the standby operation, the auxiliary winding voltage of the sub power supply is controlled by the main power supply. Supply to the control unit, there is no need to have a plurality of AC input units,
Since it is not necessary to use a large element such as a relay for N / OFF, it is possible to reduce the number of parts and reduce the size of the device.

Further, when the auxiliary winding has the same polarity as the primary winding, the voltage of the auxiliary winding is prevented from fluctuating due to the fluctuation of the AC input voltage. When the withstand voltage of the main power supply control element is lower than that of the sub power supply control element, it is possible to avoid applying an excessive voltage to the power supply control element of the main power supply.

[Modification of Second Embodiment] FIG. 4 is a circuit diagram of a two-converter power supply showing a modification of the second embodiment of the present invention, wherein a power supply for +24 V output is a main power supply, and +3.
The power supply for 3V output indicates the sub power supply. It should be noted that both the main power supply and the sub power supply are configured by a flyback type power supply that controls the output voltage by the PWM method.

In a power supply for 3.3 V output, the input voltage from the AC input section is full-wave rectified by a diode bridge 201 and smoothed by a smoothing capacitor 202. A power control IC 203 is activated by start resistors 204 and 205. After the power is turned on, the power control IC 203 performs ON / OFF control of the FET 206. When the FET 206 is ON, an exciting current flows through the primary winding 207a of the transformer 207 to generate magnetic flux, thereby storing energy in the transformer 207. At this time 2
The secondary-side diode 210 does not transmit energy to the secondary side because the polarity of the secondary winding 207s of the transformer 207 is opposite. The auxiliary winding 207b is the secondary winding 2
Since the polarity is the same as 07s, a voltage proportional to the number of turns of the voltage generated in the secondary winding 207s is generated, and a voltage obtained by rectifying and smoothing the generated voltage by the diode 208 and the capacitor 209 is supplied as a power supply voltage. .

When the FET 206 is turned off, the secondary winding 20
Since the voltage of 7 s is inverted, the diode 210 is turned on.
Then, by supplying a current to the capacitor 211, energy is taken out to the secondary side.

Reference numeral 212 denotes a shunt regulator, and a current flows from the cathode to the anode so that the voltage divided by the feedback resistors 213 and 214 and the reference voltage of the shunt regulator 212 become equal.
215 is a current limiting resistor, and 216 is a photocoupler.

The current flows from the cathode to the anode of the shunt regulator 212 so that the photocoupler 2
When a current flows through the 16 light emitting units, the light receiving unit is turned on, and the current flows out from the feedback terminal (FB) of the power supply control IC 203. According to this current, the power control IC 203
The ON duty of the ET 206 is controlled to stabilize the output voltage.

On the other hand, the transformer 217 of the main power supply for 24V output has no auxiliary winding, and power is supplied to the power supply control IC 218 from the auxiliary winding 207b of the sub power supply via the photocoupler 219. CPU 220:
Power is supplied from a 3V output sub-power supply, and by setting a terminal connected to one end of the photocoupler 219 on the diode side to Low, a current flows to the diode side of the photocoupler 219 and the transistor of the photocoupler 219 The side becomes conductive, the voltage from the auxiliary winding 207b is supplied to the power supply control IC 218, and the main power supply operates.

Further, by setting the terminal to High, the transistor side of the photocoupler 219 is cut off, and the power supply control I
The power supply to C218 is cut off, and the main power supply stops. The resistor 221 has a function of limiting the current flowing through the diode of the photocoupler 219.

In this modification, the main power supply and the sub power supply are described as a flyback method. However, a forward power supply method or another power supply method may be used.

As described above, by making the auxiliary winding the same polarity as the secondary winding, the secondary winding is made to have a constant voltage by the feedback circuit. Since it occurs in the winding, the constant voltage circuit can be deleted,
The number of parts can be reduced.

[Third Embodiment] FIG. 5 shows a third embodiment of the present invention.
1 is a circuit diagram of a power supply device according to an embodiment of the present invention. The present power supply device is configured by a flyback switching power supply.

In FIG. 5, T401 is an insulating transformer, and a current flows intermittently by the N-channel MOSFET Q401. The N-channel MOSFET Q401 is driven ON / OFF by a power supply control circuit (not shown), and has an output voltage of a predetermined value (in the present embodiment, 3.3V,
5V, 24V).

The output side (secondary side) is on the right side of the transformer T401. In this embodiment, there are three types of output voltages.
Rectifier D401, capacitor C401, rectifier D402, capacitor C402, rectifier D40
3. Rectified and smoothed by the capacitor C403 to obtain a predetermined output voltage.

The load interruption circuit is a P-channel MOSFET
Q402 and Q403, resistors R401 to R404, and transistors Q404 and Q405. A load cutoff signal is connected to the base terminals of the transistors Q402 and Q403.
Control is performed by a control circuit operating at a voltage of 3.3 V such as U.

If the load shedding signal is low, the transistors Q404 and Q405 are turned off,
When the channel MOSFETs Q402 and Q403 are cut off, power supply to the 5V and 24V loads is cut off.

On the other hand, if the load cutoff signal is at the high level, the transistors Q404 and Q405 are turned on, and the P-channel MOSFETs Q402 and Q403 are turned on to supply power to the 5V and 24V loads.

The P-channel MOSFETs Q402, Q402
The state of the output voltage waveform at the time of power supply immediately after the conduction of 403 is shown in FIG.

When the load cutoff signal goes high and the cutoff state is released, the energy stored in the secondary windings S2 and S3 and the capacitors C201 and C202 at the time of the load cutoff state is transferred to the secondary side. It is transmitted to the control circuit and the load.

In normal operation, the output voltage is adjusted to a target value by the operation of a not-shown secondary-side constant voltage control circuit, or a dummy current is supplied to the dummy resistor 405 during a light load such as in a power saving mode. The energy is adjusted to the target voltage by releasing the energy. However, during the period until the output voltage reaches the target voltage by the feedback of the circuit operation, the secondary winding S2 of the transformer T401 is in the load cutoff state. Only the charging operation works in the circuit including S3, the diodes D401 and D402, and the capacitors C401 and C402, and as a result, the winding voltage, that is, the voltage higher than the target voltage is increased. This high voltage is applied to the control circuit and load on the secondary side.

However, before the load on the secondary side including the dummy resistor, the coils 1101 and 1102 and the capacitor C10
1, by arranging C102, they operate as a filter, and become a circuit that cannot follow the change in the period in which the target voltage shifts from the high state to the target voltage, to the control circuit and the load on the secondary side. Of the excessive voltage is suppressed.

[Fourth Embodiment] FIG. 7 is a circuit diagram of a power supply device according to a fourth embodiment. The switching regulator on the upper side of FIG. 7 is configured by a general RCC type flyback type switching regulator, and operates both during the operation of the device and in the standby mode.
A voltage of 3.3 V is supplied to 131.

The lower switching regulator in FIG. 7 is constituted by a PWM type switching regulator using a power supply control IC 121. The operation is almost the same as that of the conventional example shown in FIG.
The circuit configuration for supplying power to the power supply is different. This switching regulator uses SLEE from IC131.
Pros and cons of operation can be controlled by the P signal. During device operation,
The present switching regulator also operates, and controls the supply of power to the power supply control IC 121 via the photocoupler PC131 such that the switching regulator stops when the device is on standby.

The power supply control IC 121 has a drive voltage range of 9
V to 20 V, and the drive voltage required at startup is 15 V or more. Zener diode ZD121
If the Zener voltage is 18 V, the device is in a standby state. If the phototransistor of the photocoupler PC131 is OFF, the switching regulator stops operating, and the IC 121 is generating a potential of 18V.

Here, when the device starts to operate,
SLEEP is released by the IC 131, and the phototransistor of the photocoupler PC131 is turned on. Thus, the power supply control IC 121 is initially supplied with a potential of 18 V generated in the IC 121. When the IC 121 starts operating, the potential of the capacitor C121 decreases because the IC 121 consumes power.
As the power starts to be supplied from the auxiliary winding, the voltage starts rising without lowering to 8 V or less, and then converges to a predetermined voltage.

The number of turns of the auxiliary winding is set so that the converged voltage is between 8 V and 18 V. Therefore, the present switching regulator continues to operate, and no current flows into the Zener diode ZD121.

As shown in FIG. 8, instead of the photocoupler PC131 of FIG. 7, a photocoupler PC231 and a transistor Q222 connected in Darlington can be used. Such a configuration is particularly useful when the current transfer rate of the photocoupler is insufficient or when the drive current of the power supply control IC is large and exceeds the allowable current of the photocoupler.

Further, as shown in FIG. 9, the starting resistor R121 in FIG. 7 may be replaced with a resistor R321 so that an operation starting current of the power supply control IC obtained after rectification is obtained before rectification. It is possible. In this case, there is an advantage that the loss of the starting resistance is reduced and the efficiency is increased, but there is a disadvantage that the terminal noise is increased.

[Modification of Fourth Embodiment] FIG. 10 is a circuit diagram of a power supply device according to a modification of the fourth embodiment.
The upper switching regulator is a power control IC 42
1 is a PWM type flyback switching regulator. The element on the left side of the diode D423 connected to the auxiliary winding of the transformer T411 is
Power supply control IC 121 of lower switching regulator
Of the driving power supply.

The lower switching regulator is a PWM flyback switching regulator using the power supply control IC 121. As described above, the drive voltage of the power supply control IC 121 is obtained by smoothing and rectifying the auxiliary winding of the transformer T411 of the upper switching regulator by the diode D423 and the capacitor C425. The number of turns of the auxiliary winding of the transformer T411 is determined so that the driving voltage changes from 8V to 18V.

The drive voltage of the power supply control IC 121 is
It is obtained in the same manner as the power supply device of FIG. It is also assumed that the Zener voltage of Zener diode ZD421 is 18V.

When the device is on standby, the IC 131
Is low and the photocoupler P
Since the phototransistor of C431 is turned off, no driving power is supplied to the power control IC 121, and the lower switching regulator is stopped. At this time, the voltage of the capacitor C425 is changed to the Zener diode ZD42.
It is fixed at 18 V determined by a zener voltage of 1.

When the device starts to operate, the IC 13
1 indicates that the phototransistor of the photocoupler PC431 is O
Then, 18V is initially supplied to the IC 121 as a drive voltage. Then, the voltage applied to the IC 121 decreases in accordance with the current consumption of the IC 121, and becomes a voltage obtained by smoothing rectifying the auxiliary winding of the transformer T411 with the diode D423 and the capacitor C425. Since this voltage is set to be between 8 V and 18 V, the operation of the present switching regulator continues, and no current flows into Zener diode ZD421.

Although not shown, the present system can also be realized by adding a transistor to the photocoupler PC431 by Darlington connection as shown in FIG. Also, the present invention can be realized by connecting the starting resistor R421 before rectification, not after rectification of the commercial power supply.

[Another Modification of the Fourth Embodiment] FIG.
FIG. 14 is a circuit diagram of a power supply device according to a modified example of the fourth embodiment.
This is a PWM flyback switching regulator using C421. The lower switching regulator is a PWM flyback switching regulator using the power supply control IC 121.

The rectifying / smoothing circuit composed of the diode D523 and the capacitor C525 connected to the auxiliary winding of the transformer T411 is a drive power source for the power control IC 421 and also a drive power source for the power control IC 121.
Also, a Zener diode ZD521, a capacitor C52
7 is for supplying power at the start of operation, and has a diode D52.
6 serves to prevent backflow from the capacitor C527 to the capacitor 525.

It is assumed that the Zener voltage of Zener diode ZD521 is 18V.

Further, the transformer T4 is controlled so that the drive voltage of the power supply control ICs 421 and IC121 obtained by smoothing and rectifying the auxiliary winding of the transformer T411 with the diode D523 and the capacitor C525 becomes 8V to 18V.
The number of turns of the eleven auxiliary windings is determined.

When the device is on standby, the IC 131
Is low and the photocoupler P
Since the phototransistor of C431 is turned off, no driving power is supplied to the power control IC 121, and the lower switching regulator is stopped. At this time, the voltage of the capacitor C527 is changed to the Zener diode ZD52.
It is fixed at 18 V determined by a zener voltage of 1.

When the device starts to operate, the IC 13
1 indicates that the phototransistor of the photocoupler PC431 is O
Then, 18V is initially supplied to the IC 121 as a drive voltage. Then, the voltage applied to the IC 121 decreases in accordance with the current consumption of the IC 121, and becomes a voltage obtained by smooth rectifying the auxiliary winding of the transformer T411 with the diode D523 and the capacitor C525. Since this voltage is set to be between 8 V and 18 V, the operation of the present switching regulator continues, and no current flows into Zener diode ZD521.

With such a configuration, the capacitor C527 charged by the resistor R421 can be changed from a smoothing capacitor requiring a relatively large capacity to a small capacitor having only a function of supplying a current at startup. Therefore, it is possible to shorten the time until the voltage of the capacitor can be started to be started, or to improve the efficiency by increasing the resistance value of the starting resistor.

Although not shown, the present method can also be realized by adding a transistor to the photocoupler PC431 by Darlington connection as shown in FIG. Also, the present invention can be realized by connecting the starting resistor R421 not before the rectification of the commercial power supply but before the light flow.

[Fifth Embodiment] FIG. 12 is a circuit diagram of a power supply device according to a fifth embodiment. This power supply device comprises a flyback switching power supply.

In FIG. 12, T101 is an insulating transformer, and a current flows intermittently by the N-channel MOSFET Q101. The N-channel MOSFET Q101 is driven by a power supply control circuit (not shown), and is controlled so that the output voltage becomes a predetermined value (here, 3.3V, 5V, 24V).

The output side (secondary side) is on the right side of the insulating transformer T101. In the present embodiment, there are three output voltages. Rectifier D101, capacitor C10
1. Rectification is performed by the rectifier D102, the capacitor C102, the rectifier D103, and the capacitor C103 to obtain a predetermined output voltage.

The load interruption circuit is a P-channel MOSFET
Q102, resistors R101 to R102, transistor Q1
04. A load cutoff signal is connected to the base terminal of the transistor Q104, and is controlled by a control circuit that operates at a voltage of 3.3 V such as a device control CPU (not shown).

When the load shedding signal is at the low level, the transistor Q104 is turned off, and the P-channel M
The power supply to the 24V load is cut off by turning off the OSFET Q102.

On the other hand, when the load shedding signal is at the high level, the transistor Q104 is turned on, and the P-channel MOSFET Q102 is turned on.
Power is supplied to V and 24 V loads.

When the load cutoff circuit operates and the power supply to the 24V load is cut off, the low voltage 3.3V load current used in the control circuit and the like increases. Due to the structure of the insulating transformer T101, the winding voltage rises to 24 V, that is, a voltage higher than the target voltage. When the load shedding signal goes high in this state, the dummy resistor R110
Until the function is performed, a high voltage is applied to the control circuit and the load on the secondary side even momentarily (see FIG. 13).

However, the P-channel MOSFET Q
By connecting the capacitor C110 to the gate of the transistor 102, the rise of the voltage of the gate of the P-channel MOSFET Q102 becomes gentle, and it becomes impossible to suppress the application of the excessive voltage to the 24V load (see FIG. 14).

Although this embodiment is applied to a flyback type switching power supply, it is also possible to apply to a forward type and other types of switching power supply.

[Modification of Fifth Embodiment] FIG. 15 is a circuit diagram of a power supply device according to a modification of the fifth embodiment.
The difference from the fifth embodiment shown in FIG. 12 is that a load cutoff circuit is also provided for the 5 V output.

That is, in FIG. 15, the load cutoff circuit includes P-channel MOSFETs Q102 and Q201, resistors R101 to R102, R201 to 202, and transistors Q104 and Q202. A load cutoff signal is connected to the base terminals of the transistors Q104 and Q202, and is controlled by a control circuit that operates at a voltage of 3.3 V such as a device control CPU (not shown).

If the load shedding signal is low, the transistors Q104 and Q202 are turned off,
By shutting off the channel MOSFETs Q102 and Q201, power supply to the 24V and 5V loads is shut off.

On the other hand, when the load cutoff signal is at the high level, the transistors Q104 and Q202 are turned on, and the P-channel MOSFETs Q102 and Q201 are turned on to supply power to the 5V and 24V loads.

Further, the load interrupting circuit operates, and the 24 V, 5
In a state where power supply to the V load is cut off, when the low-voltage 3.3 V load current used in the control circuit or the like increases, the structure of the insulating transformer T101 is accordingly increased. , 24V, 5V, ie, higher than the target voltage. In this state, when the load shedding signal becomes High level, a high voltage is momentarily applied to the control circuit and the load on the secondary side until the dummy resistors R110 and R210 function (FIG. 13).

However, the P-channel MOSFET Q
Capacitors C110 and C2 are connected to the gates of 102 and Q201.
10 is connected to the P-channel MOSFET Q
The rise of the voltage of the gates of 102 and Q201 becomes gentle, and it becomes impossible to suppress the application of the excessive voltage to the 24V load and the 5V load (see FIG. 14).

Although the present embodiment is applied to a flyback type switching power supply, it is also applicable to a forward type switching power supply and other types of switching power supply.

As described above, in the fourth embodiment, in the switching power supply for supplying a plurality of output voltages to the load by one transformer, the capacitive element is connected between the gate of the FET, which is the switching element, and the ground. By doing so, the instantaneous output voltage overshoot that occurs when the load interrupting circuit is turned off is eliminated, and it is possible to avoid applying an excessive voltage to the control IC and the like.

[Sixth Embodiment] FIG. 16 is a circuit diagram of a power supply device according to a sixth embodiment of the present invention. This power supply device has a configuration substantially the same as that of the sixth conventional example shown in FIG. 24, except that a circuit (such as the transistor 129 in FIG. 24) for exclusively cutting off the 24 V output is omitted, and one cutoff circuit is used. The difference is that both the 24V output and the 3.3V output are cut off.

When the 24V power supply is overcurrent, an electromotive force is generated in the resistor 120 as in the conventional case, and the electromotive voltage is detected by the comparator 125. And comparator 1
Reference numeral 25 turns on the transistor 29 for stopping the 3.3 V power supply, and causes the photocoupler 15 to emit light. Then I
The voltage of the SD terminal of C4 rises, and the oscillation of 1C4 stops. When 1C4 stops, the supply of the auxiliary power from the auxiliary winding 12 to the 24V power supply also stops.
104 can be similarly stopped, and the 24V output can be stopped.

In this embodiment, the present invention is applied to a flyback type power supply. However, the present invention is applied to a power supply other than the flyback type, such as a forward power supply, a resonance power supply, a series dropper, and a ringing choke converter. Is also possible.

Although the description has been given of the example of the overcurrent protection function, the overvoltage protection function, the heating protection function, and the like can be similarly realized.

[Modification of Sixth Embodiment] FIG. 17 is a circuit diagram of a power supply device according to a modification of the sixth embodiment of the present invention. In the sixth embodiment, when the 24V power supply is abnormal, the 3.3V power supply is also stopped.
Only the 4V power supply is stopped.

In FIG. 17, reference numeral 200 denotes an engine controller which operates at 3.3V. When the 24V power supply is overcurrent, an electromotive voltage is generated in the resistor 120. The engine controller 200 detects this electromotive voltage via the A / D input terminal and detects the 24V power supply of the photocoupler 20.
1 to stop supplying auxiliary power to the sub-power supply (24V power supply).

At the same time, the engine controller 200
Display the 24V power supply abnormality on the operation panel,
Make the user aware of that.

In this modification, the abnormality of the 24V power supply is detected using the A / D input terminal of the engine controller 200. However, a comparator may be used as in the sixth embodiment.

The power supply device according to each of the first to sixth embodiments is assumed to be a power supply device mounted on an image forming apparatus such as a copying machine. Is also possible.

[0168]

As described above, according to the present invention,
In a switching power supply that generates a plurality of voltages by one transformer having a plurality of secondary windings, it is possible to cut off the voltage supply efficiently and inexpensively.

Further, according to the present invention, it is possible to reduce the size of a multi-output power supply device including a plurality of converters for generating a DC voltage from a commercial power supply.

Further, according to the present invention, in a switching power supply device that generates a plurality of voltages by one transformer having a plurality of secondary windings, the instantaneous output voltage when the interruption of the voltage supply is released. It is possible to suppress a significant rise.

Further, according to the present invention, a multiple output power supply device including a plurality of converters for generating a DC voltage from a commercial power supply can support a plurality of commercial power supply voltages.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram of a power supply device according to a modification of the first embodiment of the present invention.

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

FIG. 4 is a circuit diagram of a power supply device according to a modification of the second embodiment of the present invention.

FIG. 5 is a circuit diagram of a power supply device according to a third embodiment of the present invention.

FIG. 6 is a diagram illustrating an output voltage waveform of a cutoff circuit of a power supply device according to a third embodiment of the present invention.

FIG. 7 is a circuit diagram of a power supply device according to a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram showing a modification of the signal transmission system of the circuit of FIG. 7;

9 is a circuit diagram showing a modified example of a source for obtaining an operation start current of the power supply control IC of the circuit of FIG. 7;

FIG. 10 is a circuit diagram of a power supply device according to a modification of the fourth embodiment of the present invention.

FIG. 11 is a circuit diagram of a power supply device according to another modification of the fourth embodiment of the present invention.

FIG. 12 is a circuit diagram of a power supply device according to a fifth embodiment of the present invention.

FIG. 13 is a diagram showing an output voltage waveform in a case where the power supply device according to the fifth embodiment of the present invention does not have a high-voltage application prevention function in the shutoff circuit.

FIG. 14 is a diagram showing an output voltage waveform in a case where a high voltage application prevention function is not provided in a shutoff circuit of a power supply device according to a fifth embodiment of the present invention.

FIG. 15 is a circuit diagram of a power supply device according to a modification of the fifth embodiment of the present invention.

FIG. 16 is a circuit diagram of a power supply device according to a sixth embodiment of the present invention.

FIG. 17 is a circuit diagram of a power supply device according to a modification of the sixth embodiment of the present invention.

FIG. 18 is a circuit diagram of a power supply device according to a first conventional example.

FIG. 19 is a circuit diagram of a power supply device according to a second conventional example.

FIG. 20 is a circuit diagram of a power supply device according to a third conventional example.

FIG. 21 is a waveform chart for explaining a problem of the third conventional example.

FIG. 22 is a circuit diagram of a power supply device according to a fourth conventional example.

FIG. 23 is a circuit diagram of a power supply device according to a fifth conventional example.

FIG. 24 is a circuit diagram of a power supply device according to a sixth conventional example.

[Explanation of symbols]

T101, T201 Transformer Q102, Q202 P-channel MOSFET Q103, Q203 N-channel MOSFET R203, R204 Voltage dividing resistor 217 Power transformer 118, 218 Main power control IC 103, 203 Sub power control IC 107b, 207b Auxiliary winding 121 Zener diode 123, 219 Photocoupler L101, L102 Coil C101, C102 Capacitor T401 Isolation transformer Q402, Q403 P-channel MOSFET C121, C523, C526 Capacitor D121, D523, D526 Diode ZD121, ZD523, ZD526: Zener diode IC121: Power supply control IC Q111, Q121: FET C110, C210: Capacitor 1: AC power 4 ... The main power supply controlling IC 12 ... auxiliary winding 104 ... sub power supply control IC 201 ... photocoupler

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuma Yamamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yasuhiro Nakata 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo Within non-corporation (72) Inventor ▲ Taka ▼ Hiroshi Sawa 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term within Canon Inc. (reference) 5H730 AA14 AA15 BB43 BB55 BB57 BB81 CC01 DD04 EE02 EE07 EE51 EE73 FD01 FD31 FF09 FF19 FG05 VV01 XX03 XX15 XX23 XX35 XX44

Claims (20)

[Claims] 1. A switching power supply for generating a plurality of voltages by a single transformer having a plurality of secondary windings, wherein a P-channel MOS is used as an element for cutting off the output of the maximum voltage.
An N-channel MOSFET as an element that uses an FET to drive the control circuit and to cut off the output of voltages other than the maximum voltage.
Wherein the drain of the P-channel MOSFET is connected to the load side and the gate of the N-channel MOSFET, and the source of the N-channel MOSFET is connected to the load side. 2. The power supply device according to claim 1, wherein a gate of said P-channel MOSFET is controlled by said control circuit. 3. The power supply device according to claim 1, wherein a gate of said N-channel MOSFET is connected to a drain of said P-channel MOSFET via a voltage dividing resistor. 4. A multi-output power supply comprising a plurality of converters for generating a DC voltage from a commercial power supply, wherein the multi-output power supply stops operating during standby and does not stop operating during standby. A second switching power supply, wherein the transformer of the second switching power supply has a primary winding, a secondary winding for obtaining a desired output voltage, and an auxiliary winding; A power supply device for supplying a voltage of the auxiliary winding to each drive control circuit that drives and controls each switching element of a second switching power supply. 5. The auxiliary winding of the transformer of the second switching power supply has the same polarity as the primary winding of the transformer, and the voltage of the auxiliary winding is supplied via a low-voltage circuit and a switch. 5. The control circuit according to claim 4, wherein the first switching power supply is supplied to a drive control circuit that drives and controls a switching element of the first switching power supply, and the switching operation of the switch starts and stops the first switching power supply. Power supply. 6. An auxiliary winding of a transformer of the second switching power supply has a polarity opposite to that of a primary winding of the transformer, and a voltage of the auxiliary winding is supplied to the first winding via a switch. 5. The power supply device according to claim 4, wherein the power supply device is supplied to a drive control circuit that drives and controls a switching element of the switching power supply, and starts and stops the first switching power supply by opening and closing the switch. 6. 7. A switching power supply device for generating a plurality of voltages by a single transformer having a plurality of secondary windings, comprising: a blocking circuit including a switching element for individually blocking output of the plurality of voltages to a load. A power supply device comprising: a filter provided at a stage subsequent to a switching element of the cutoff circuit. 8. The power supply device according to claim 7, wherein the filter includes a coil and a capacitor. 9. The power supply device according to claim 7, wherein the cutoff circuit includes a dummy resistor for flowing a dummy current. 10. A multi-output power supply device comprising a plurality of switching regulators for generating a DC voltage from a commercial power supply, wherein the multi-output power supply stops operating during standby and stops operating during standby. Not second
The second switching regulator has, on the input side of the transformer, an auxiliary winding to which a rectifying and smoothing circuit including a zener diode is added in addition to the primary winding, A power supply device for supplying a voltage from the auxiliary winding and a rectifying / smoothing circuit to a drive control circuit that drives and controls each switching element of the switching regulator. 11. A multi-output power supply apparatus comprising a plurality of switching regulators for generating a DC voltage from a commercial power supply, wherein the multi-output power supply stops operating during standby and stops operating during standby. Not second
A switching regulator of the first switching regulator, further comprising, on the input side of the transformer, an auxiliary winding to which a rectifying and smoothing circuit including a zener diode is added in addition to the primary winding. A power supply device for supplying a voltage from the auxiliary winding and the rectifying / smoothing circuit to each drive control circuit for driving and controlling each switching element of the second switching regulator. 12. The power supply device according to claim 10, wherein a Zener voltage of the Zener diode is higher than an output voltage of the rectifying / smoothing circuit. 13. The power supply device according to claim 10, wherein the rectifying and smoothing circuit has two sets of rectifying and smoothing circuits each including a diode and a capacitor. 14. A switching power supply device for generating a plurality of voltages by a single transformer having a plurality of secondary windings, comprising: a switching circuit including a switching element for individually cutting off outputs of the plurality of voltages to a load. A power supply device, characterized in that a capacitive element is added between a control input of a switching element of the cutoff circuit and ground. 15. The switching element of the cutoff circuit,
P-channel MOSFET with drain connected to load side
The power supply device according to claim 14, comprising: 16. The interruption circuit according to claim 14, wherein the interruption circuit includes a resistance element for flowing a dummy current.
The power supply device according to 5. 17. A multi-output power supply device comprising a plurality of converters for generating a DC voltage from a commercial power supply, wherein the multi-output power supply stops operating during standby and does not stop operating during standby. And a second switching power supply, wherein the second switching power supply comprises:
An auxiliary power supply generated by the second switching power supply for driving each drive control circuit for driving and controlling each switching element of the first and second switching power supplies, and an abnormality in the first switching power supply. And a stop circuit for stopping the supply of the auxiliary power to each of the drive control circuits when the power is generated. 18. A multi-output power supply device comprising a plurality of converters for generating a DC voltage from a commercial power supply, wherein the multi-output power supply stops operating during standby and does not stop operating during standby. And a second switching power supply, wherein the second switching power supply comprises:
An auxiliary power supply generated by the second switching power supply for driving each drive control circuit for driving and controlling each switching element of the first and second switching power supplies, and an abnormality in the first switching power supply. And a stop circuit for stopping the supply of the auxiliary power to a drive control circuit that drives and controls a switching element of the first switching power supply when the power is generated. 19. The power supply device according to claim 17, wherein the auxiliary power supply includes an auxiliary winding formed on an input side of a transformer of the second switching power supply. 20. The power supply device according to claim 1, wherein the power supply device is mounted on the image forming apparatus.