JPH11289757A - Power supply device and output control method in power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure safety and at the same time reduce costs and miniaturize a power supply device by providing a means for forcibly stopping the operation of a switching means when an output voltage at a secondary side exceeds a set voltage. SOLUTION: When an output voltage V at the secondary side of a switching regulator becomes excessive, a Zener diode ZD3 of an overvoltage detection circuit 4 conducts electricity, and the photodiode of a photocoupler PC1 of an output voltage detection circuit 2 is allowed to emit light with the maximum quantity of light accordingly, thus maximizing the collector current of the photo transistor of the photo coupler PC1, generating a voltage drop due to the flow of the collector current through a resistor R8 for detection of a primary side detection circuit 5, and turning on a transistor Q4 of the primary detection circuit 5, thus turning on a transistor Q6 of a latch circuit 6, activating latch when the transistor Q5 is turned on, and forcibly stopping the switching of a switching MOS-FET Q1.

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 and an output control method in the power supply device, and more particularly, to a power supply device and an output in the power supply device which are suitable when the overvoltage protection means is shared with existing electronic parts. It relates to a control method.

[0002]

2. Description of the Related Art Switching regulators have been widely used in various electronic devices. FIG. 2 is a circuit diagram showing a configuration example of a switching regulator according to a conventional example. The switching regulator according to the conventional example is an example using a self-excited and flyback method (that is, an RCC method), and includes a DC power supply (input voltage Vin), a transformer T1, an oscillation control circuit 21, and an output for constant voltage control. Voltage detection circuit 22, overvoltage detection circuit 23 for overvoltage protection, switching MOS-FET (MOS type field effect transistor) Q1, photocouplers PC1, PC2 connected to oscillation control circuit 21, diode D1, electrolytic capacitor C2
Etc. are provided.

In a conventional switching regulator, a switching MOS-FET Q1 which is an example of a switching element is connected in series to a primary winding T1a of a transformer T1, and an output of a control winding T1c of the transformer T1 is transmitted through an oscillation control circuit 21. The switching MOS-FET Q1 is fed back to the gate to oscillate, and the switching MOS-FE
When the TQ1 is turned off, the energy stored in the transformer T1 is configured to be DC-output from the secondary winding T1b via the diode D1 and extracted.

The oscillation control circuit 21 can take various known circuit configurations. In the illustrated example, a capacitor C1 inserted in series between one end of the control winding T1c of the transformer T1 and the gate of the switching MOSFET Q1 is used. , A resistor R2 and a control transistor Q2 connected to bias the gate of the switching MOS-FET Q1. Thus, the switching operation of the switching MOS-FET Q1 is controlled. R1 is a starting resistor.

[0005] In the illustrated example, a DC output circuit on the secondary side has:
An output voltage detection circuit 22 for constant voltage control and an overvoltage detection circuit 23 for overvoltage protection are connected. The output voltage detection circuit 22 includes a transistor Q3, a zener diode ZD1 for determining a reference voltage, and voltage dividing resistors R5 and R6 for dividing the output voltage V and supplying the divided voltage to the base of the transistor Q3. With this transistor Q3, a Zener diode Z
The reference voltage determined at D1 is compared with the output voltage V, and the photodiode of the photocoupler PC1 emits light according to the difference. The phototransistor side of the photocoupler PC1 is connected to an oscillation control circuit 21 in the illustrated example.
And the constant voltage control of the output voltage V is performed by the following operation.

That is, when the output voltage V rises above the reference voltage, the output of the transistor Q3 increases and is supplied to the base of the control transistor Q2 via the photocoupler PC1, so that the collector current of the control transistor Q2 increases. Accordingly, the switching MOS-FET Q1
Gate voltage is shunted and the switching MOS
-FET Q1 works in the off direction, so that the output voltage V
Is controlled.

The overvoltage detection circuit 23 includes a zener diode ZD2, a resistor R7, and a photocoupler PC2 connected in series with each other. In the illustrated example, the phototransistor side of the photocoupler PC2 is also connected to the base of the control transistor Q2 of the oscillation control circuit 21, and overvoltage protection on the secondary side is performed by the following operation.

That is, when the output voltage V becomes excessive, the Zener diode ZD2 conducts, thereby causing the photocoupler P
The photodiode of C2 is turned on, and thereafter the switching MOS is operated in the same manner as in the case of the above-described constant voltage control.
-The operation in which the ON period of the FET Q1 is shortened, and the output voltage V is reduced. With such an overvoltage protection means, it is possible to prevent, for example, a phenomenon in which a failure occurs in the electrolytic capacitor C2 and electronic equipment connected to the output terminal due to an excessive output voltage V.

[0009]

However, the above-described conventional switching regulator has the following problems. That is, paying attention to the overvoltage protection means, in the switching regulator shown in FIG. 2, the secondary side overvoltage detection signal is fed back to the primary side because of electrical insulation between the primary side and the secondary side. In addition, there is a problem that an expensive photocoupler must be used, and the cost increases.

In addition, a predetermined insulation distance or more must be set between the primary circuit and the overvoltage detection circuit around the photocoupler, and a correspondingly large space is required on the substrate of the switching regulator. However, there is a problem that the switching regulator becomes an obstacle to downsizing.

Further, when the output voltage is in an overvoltage state, that is, when the switching regulator is in a failure state, the output voltage only acts to suppress the rise of the output voltage. In practice, the switching regulator itself operates. I have. That is, when the output voltage is in an overvoltage state, the output voltage is reduced by the overvoltage protection means. However, when the output voltage decreases, the overvoltage protection means is released and the output voltage rises again. As a result of the repetition of being lowered, there was a problem in terms of ensuring safety.

On the other hand, for example, a switching regulator described in Japanese Patent Application Laid-Open No. 5-146148 has been proposed. However, the technology described in the above publication supplies a feedback signal for lowering the output voltage to the primary oscillation control circuit by causing the photodiode of the constant voltage control photocoupler to emit light when the output voltage on the secondary side becomes excessive. And
This control simply reduces the output voltage by shortening the on-period of the switching transistor connected in series to the primary winding of the transformer, and does not forcibly stop the switching of the switching transistor when an overvoltage occurs. . Therefore, as in the prior art shown in FIG. 2, there is a problem in securing safety.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and in the case where an overvoltage occurs in an output voltage due to some kind of failure, the operation of the switching means is forcibly stopped to ensure safety and reduce costs. An object of the present invention is to provide a power supply device and an output control method in the power supply device, which can reduce and reduce the size.

[0014]

According to a first aspect of the present invention, there is provided a switching device connected in series to a primary winding of a transformer, wherein a difference between an output voltage on a secondary side and a reference voltage is provided. In the power supply device that performs constant voltage control by feeding back a signal based on the primary side to the primary side, an overvoltage detection unit that detects that the output voltage on the secondary side exceeds the set voltage, and the output voltage on the secondary side And stopping means for forcibly stopping the operation of the switching means when the switching time is exceeded.

In order to achieve the above object, a second aspect of the present invention includes a primary side detection unit for detecting a detection signal of the overvoltage detection unit on a primary side, and the stop unit includes a primary side detection unit. The operation of the switching means is forcibly stopped based on a signal.

In order to achieve the above object, a third aspect of the present invention is characterized in that the overvoltage detecting means comprises a Zener diode.

In order to achieve the above object, a fourth aspect of the present invention is characterized in that the primary side detecting means comprises a resistor and a transistor.

In order to achieve the above object, a fifth aspect of the present invention is characterized in that the stopping means comprises a resistor and a transistor.

In order to achieve the above object, the invention according to claim 6 includes switching means connected in series to a primary winding of a transformer, and outputs a signal based on a difference between an output voltage on the secondary side and a reference voltage on the primary side. In the output control method in the power supply device that performs constant voltage control by feeding back to the overvoltage detection step of detecting that the output voltage on the secondary side has exceeded the set voltage, the output voltage on the secondary side has exceeded the set voltage. A stopping step for forcibly stopping the operation of the switching means in the case.

In order to achieve the above object, a seventh aspect of the present invention includes a primary side detecting step of detecting a detection signal of the overvoltage detecting step on a primary side, and in the stopping step, detecting the primary side detecting step. The operation of the switching means is forcibly stopped based on a signal.

In order to achieve the above object, the invention of claim 8 is characterized in that in the overvoltage detecting step, it is detected that the output voltage on the secondary side exceeds a set voltage by means constituted by a Zener diode. And

In order to achieve the above object, a ninth aspect of the present invention is characterized in that, in the primary side detecting step, a detection signal of the overvoltage detecting step is detected by means comprising a resistor and a transistor.

In order to achieve the above object, a tenth aspect of the present invention is characterized in that in the stopping step, the switching means is forcibly stopped by means comprising a resistor and a transistor.

[0024]

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

FIG. 1 is a circuit diagram showing a configuration example of a switching regulator according to an embodiment of the present invention. The switching regulator according to the embodiment of the present invention includes a DC power supply (input voltage Vin), a transformer T1, an oscillation control circuit 1, an output voltage detection circuit 2, an overvoltage detection circuit 4, a primary side detection circuit 5, a latch circuit 6, a switching circuit. MOS-FET
(MOS type field effect transistor) It is configured to include Q1 and the like. Note that, in FIG. 1 of the present embodiment, the same reference numerals are given to the same or corresponding circuit elements as those in FIG. 2 of the conventional example.

Further, the oscillation control circuit 1 includes a control transistor Q2, a resistor R2, and a capacitor C1. The output voltage detection circuit 2 is a photocoupler PC
1, a transistor Q3, a Zener diode ZD1, and resistors R3, R4, R5, R6. Further, the overvoltage detection circuit 4 includes a zener diode ZD3. The primary side detection circuit 5 includes a transistor Q4 and a resistor R8.
It has. The latch circuit 6 includes a transistor Q
5, a transistor Q6 and a resistor R9. The oscillation control circuit 1, the primary side detection circuit 5, and the latch circuit 6 are provided on the primary side, and the output voltage detection circuit 2 and the overvoltage detection circuit 4 are provided on the secondary side. Each of these circuits corresponds to a portion surrounded by a broken line in the figure.

First, a description will be given of the connection state of each of the above components.
The primary winding T1a of the transformer T1 is connected to a DC power supply (input voltage Vin) and the switching MOS-FET Q1, and the control winding T1c of the transformer T1 is connected to the oscillation control circuit 1 and the latch circuit 6. The oscillation control circuit 1 is connected to a control winding T1c of a transformer T1 via a capacitor C1, connected to an emitter of a transistor Q6 of a latch circuit 6, a diode D2, and a switching MOS-FET Q1 via a resistor R2.
Switching MOS-FET Q
1. Connected to the primary winding T1a of the transformer T1, connected to the emitter of the transistor Q4 of the primary side detection circuit 5 via the base of the transistor Q2, and connected to the emitter of the transistor Q5 of the latch circuit 6 via the emitter of the transistor Q2. It is connected.

In the primary side detection circuit 5, the base of the transistor Q4 is connected to the photocoupler PC1, the emitter of the transistor Q4 is connected to the oscillation control circuit 1, and the collector of the transistor Q4 is connected to the transistor Q5 of the latch circuit 6.
And the base of the transistor Q6. Photocoupler PC1 is connected to diode D2. In the latch circuit 6, the emitter of the transistor Q5 is connected to the control winding T1c of the transformer T1, the emitter of the transistor Q2 of the oscillation control circuit 1, and the transistor Q5.
5 is connected to the collector of the transistor Q6 and the resistor R7.

The secondary winding T1b of the transformer T1 is connected to the output voltage detection circuit 2 via the diode D1 and to the overvoltage detection circuit 4. Transformer T1
The electrolytic capacitor C2 is connected in parallel to the secondary winding T1b. The output voltage detection circuit 2 is a photocoupler PC
1, resistor R3, transistor Q3, zener diode Z
D1 are connected in series, the photocoupler PC1 is connected to the diode D1 and the + terminal of the output terminal, and the Zener diode ZD is the Zener diode Z of the overvoltage detection circuit 4.
D3, connected to the GND side of the output terminal, the transistor Q
The resistors R5 and R6 are connected to the base of the transistor 3, and the resistor R4 is connected to the emitter of the transistor Q3. In the overvoltage detection circuit 4, a Zener diode ZD3 is connected between the photocoupler PC1 of the output voltage detection circuit 2 and the resistor R3.

In the following, differences from the conventional example will be mainly described. In the embodiment of the present invention, instead of providing the overvoltage detection circuit 23 and the overvoltage detection photocoupler PC2 shown in FIG. 2 of the conventional example, the overvoltage detection circuit 4 is provided in the output circuit on the secondary side, Further, a primary side detection circuit 5 for detecting a signal from the overvoltage detection circuit 4 and a switching MOS-FE based on a signal from the primary side detection circuit 5
It is characterized in that the latch circuit 6 for forcibly stopping the switching operation of the TQ1 is connected to the oscillation control circuit 1 on the primary side.

Next, the operation of the switching regulator according to the embodiment of the present invention configured as described above will be described.

When the output voltage V on the secondary side of the switching regulator becomes excessive, the Zener diode ZD3 of the overvoltage detection circuit 4 conducts, and accordingly, the photodiode of the photocoupler PC1 of the output voltage detection circuit 2 emits light with the maximum light quantity. Let me do. Thereby, the photocoupler PC1
The collector current of the phototransistor becomes maximum, and the collector current flows through the detection resistor R8 of the primary side detection circuit 5, causing a voltage drop.
Transistor Q4 is turned on. As a result, the transistor Q6 of the latch circuit 6 is turned on, and when the transistor Q5 is turned on, the latch is activated and the switching MO is activated.
The switching of the S-FET Q1 is forcibly stopped. In this way, overvoltage protection is performed.

As described above, according to the switching regulator according to the embodiment of the present invention, the overvoltage detection circuit 4 for detecting that the output voltage on the secondary side has exceeded the set voltage, and the overvoltage detection circuit 4 Since it has a primary side detection circuit 5 for detecting the detection signal on the primary side and a latch circuit 6 for forcibly stopping the switching operation of the switching MOS-FET Q1 based on the detection signal of the primary side detection circuit 5,
The following effects are obtained.

According to the above configuration, when the output voltage on the secondary side of the switching regulator becomes excessive beyond the set voltage, the overvoltage detection circuit 4 detects that the output voltage on the secondary side becomes excessive. Along with this, the detection signal of the overvoltage detection circuit 4 is detected by the primary side detection circuit 5 via the photocoupler, and the latch circuit 6 which stops switching by the signal from the primary side detection circuit 5 operates. This allows
The output voltage of the switching regulator is no longer generated, and it is possible to avoid a phenomenon in which the output voltage becomes excessively high in the electronic device connected to the electrolytic capacitor C2 and the output terminal as in the related art. It becomes possible.

That is, in the switching regulator according to the embodiment of the present invention, when the switching regulator has a failure such as an overvoltage at the output terminal of the switching regulator, the overvoltage detection circuit 4 detects the failure. In order to stop the output voltage V by detecting the signal with the primary side detection circuit 5 and operating the latch circuit 6 by the signal to forcibly stop the switching of the switching MOS-FET Q1, the secondary side When the output voltage becomes excessive, it is fundamentally different from control that simply reduces the output voltage by shortening the on-period of the switching transistor connected in series with the primary winding of the transformer, and secures more safety than before Of providing an improved switching regulator A.

Further, since the existing photocoupler PC1 for constant voltage protection is also used for overvoltage protection, it is not necessary to use a high-priced photocoupler dedicated to overvoltage protection as in the prior art. Some transistors and resistors used in the primary side detection circuit 5 and the latch circuit 6 are inexpensive compared to the photocoupler.
There is an effect that it is possible to provide a switching regulator that realizes cost reduction as compared with the related art.

Further, as described above, since the photocoupler dedicated to overvoltage protection is not used, it is not necessary to set the insulation distance between the primary side circuit and the secondary side circuit around the photocoupler, and the space for the switching regulator board is eliminated. Therefore, there is an effect that it is possible to provide a switching regulator that is more compact than before.

It should be noted that the present invention is not limited to the above-described embodiment, but can be modified without departing from the gist of the present invention. In addition, the present invention can be applied to a system including a plurality of devices,
The present invention may be applied to an apparatus including one device.

[0039]

As described above, according to the power supply apparatus of the first aspect of the present invention, switching means connected in series to the primary winding of the transformer is provided, and the output voltage of the secondary side and the reference voltage are provided. In a power supply device that performs constant voltage control by feeding back a signal based on the difference to the primary side, an overvoltage detection unit that detects that the output voltage on the secondary side exceeds a set voltage, and the output voltage on the secondary side is set. Since there is provided a stopping means for forcibly stopping the operation of the switching means when the voltage is exceeded, the following effects are obtained.

In a state where some trouble has occurred in the power supply device, such as an overvoltage occurring at the output terminal of the power supply device, the signal detected by the overvoltage detection means is detected by the primary side detection means, and the signal is detected by the primary side detection means. In order to stop the output voltage by operating the stop means and forcibly stopping the operation of the switching means, as in the related art, when the output voltage on the secondary side becomes excessive, the output voltage is connected in series to the primary winding of the transformer. This is fundamentally different from control in which the on-period of the switching transistor is shortened and the output voltage is simply reduced, and there is an effect that it is possible to provide a power supply device that is more secure than before.

According to a second aspect of the present invention, the power supply apparatus further includes a primary side detecting unit for detecting a detection signal of the overvoltage detecting unit on a primary side, and the stopping unit includes a primary side detecting unit for detecting the detection signal of the primary side detecting unit. Since the operation of the switching means is forcibly stopped based on the signal, the following effects are obtained.

In the same manner as in the first aspect of the present invention, in a state where some trouble has occurred in the power supply such as an overvoltage occurring at the output terminal of the power supply, the signal detected by the overvoltage detecting means is output to the primary side. The output voltage is detected by the detection means, and the stop means is operated by the signal, and the operation of the switching means is forcibly stopped to stop the output voltage. To provide a power supply device that is fundamentally different from control that simply reduces the output voltage by shortening the on-period of a switching transistor connected in series to the primary winding of a transformer, and that is more secure than before. There is an effect that can be.

According to the power supply device of the third aspect of the present invention, since the overvoltage detecting means is constituted by a Zener diode, the following effects are obtained.

It is not necessary to use a high-priced photocoupler dedicated to overvoltage protection as in the past, and the cost of the Zener diode used in the overvoltage detecting means is lower than that of the photocoupler. There is an effect that it is possible to provide a power supply device that realizes cost reduction more than that.

Further, since a high-priced photocoupler dedicated to overvoltage protection is not used as in the prior art, it is not necessary to set the insulation distance between the primary circuit and the secondary circuit around the photocoupler. Therefore, there is an effect that a power supply device that is more compact than before can be provided.

According to the power supply device of the present invention, since the primary side detecting means is composed of the resistor and the transistor, the following effects are obtained.

It is not necessary to use a high-priced photocoupler dedicated to overvoltage protection as in the prior art, and the cost of the resistor and transistor used in the primary side detecting means is lower than that of the photocoupler. In addition, there is an effect that it is possible to provide a power supply device that realizes cost reduction as compared with the related art.

According to the power supply device of the present invention, since the stopping means is constituted by the resistor and the transistor, the following effects are obtained.

It is not necessary to use a high-priced photocoupler dedicated to overvoltage protection as in the prior art, and the cost of the resistor and transistor used in the stopping means is lower than that of the photocoupler. There is an effect that it is possible to provide a power supply device that realizes cost reduction more than that.

According to the output control method of the power supply device of the present invention, the switching means is provided in series with the primary winding of the transformer, and is based on the difference between the output voltage on the secondary side and the reference voltage. In an output control method in a power supply device that performs constant voltage control by feeding back a signal to a primary side, an overvoltage detection step of detecting that an output voltage on a secondary side exceeds a set voltage, and an output voltage on a secondary side is set. A stopping step of forcibly stopping the operation of the switching means when the voltage is exceeded, the following effects are obtained.

In a state where some trouble has occurred in the power supply such as an overvoltage occurring at the output terminal of the power supply, the signal detected in the overvoltage detection step is detected in the primary side detection step, and the signal is detected by the primary side detection step. In the stopping step, the output voltage is stopped by forcibly stopping the operation of the switching means, so that when the output voltage on the secondary side becomes excessive as in the related art, the switching connected in series with the primary winding of the transformer is performed. This is fundamentally different from control that simply reduces the output voltage by shortening the on-period of the transistor, and has the effect of providing a power supply device that is more secure than before.

According to a seventh aspect of the present invention, there is provided an output control method for a power supply apparatus, comprising: a primary side detection step of detecting a detection signal of the overvoltage detection step on a primary side; Since the operation of the switching means is forcibly stopped based on the detection signal of the detection step, the following effects are obtained.

In the same manner as in the sixth aspect of the present invention, in a state where some trouble has occurred in the power supply such as an overvoltage occurring at the output terminal of the power supply, the signal detected in the overvoltage detection step is output to the primary side. In the detection step, the output voltage is stopped by forcibly stopping the operation of the switching means in the stop step in accordance with the signal, so that when the output voltage on the secondary side becomes excessive, the transformer This is fundamentally different from control that simply reduces the output voltage by shortening the on-period of the switching transistor connected in series to the primary winding of the power supply device, and can provide a power supply device that is more secure than before. This has the effect.

According to the output control method of the power supply device of the present invention, the overvoltage detecting step includes:
Since it is detected that the output voltage on the secondary side has exceeded the set voltage by means constituted by a Zener diode, the following effects are obtained.

It is not necessary to use a high-priced photocoupler dedicated to overvoltage protection as in the related art, and the cost of the Zener diode used in the overvoltage detection step is lower than that of the photocoupler. There is an effect that it is possible to provide a power supply device that realizes cost reduction more than that.

Further, since a high-priced photocoupler dedicated to overvoltage protection is not used unlike the prior art, it is not necessary to set the insulation distance between the primary side circuit and the secondary side circuit around the photocoupler. Therefore, there is an effect that a power supply device that is more compact than before can be provided.

According to the ninth aspect of the present invention, in the power supply apparatus, the primary side detecting step includes:
Since the detection signal of the overvoltage detection step is detected by means including a resistor and a transistor, the following effects are obtained.

It is not necessary to use a high-priced photocoupler dedicated to overvoltage protection as in the prior art, and the cost of the resistor and transistor used in the primary detection step is lower than that of the photocoupler. In addition, there is an effect that it is possible to provide a power supply device that realizes cost reduction as compared with the related art.

According to the output control method of the power supply device of the present invention, in the stopping step, the switching means is forcibly stopped by means including a resistor and a transistor. It works.

It is not necessary to use a high-priced photocoupler dedicated to overvoltage protection as in the prior art, and the cost of the resistor and transistor used in the stopping step is lower than that of the photocoupler. There is an effect that it is possible to provide a power supply device that realizes cost reduction more than that.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram showing a configuration example of a switching regulator according to a conventional example.

[Explanation of symbols]

 Reference Signs List 1 oscillation control circuit 2 output voltage detection circuit 4 overvoltage detection circuit 5 primary side detection circuit 6 latch circuit T transformer Q1 switching MOS-FET Vin input voltage V output voltage

Claims (10)

[Claims] 1. A power supply device having switching means connected in series to a primary winding of a transformer and performing constant voltage control by feeding back a signal based on a difference between a secondary output voltage and a reference voltage to a primary side. An overvoltage detecting means for detecting that the output voltage on the secondary side has exceeded the set voltage, and a stop means for forcibly stopping the operation of the switching means when the output voltage on the secondary side has exceeded the set voltage. A power supply device comprising: 2. A primary detecting means for detecting a detection signal of the overvoltage detecting means on a primary side, wherein the stopping means forcibly stops the operation of the switching means based on the detection signal of the primary detecting means. 2. The power supply according to claim 1, wherein the power supply is stopped. 3. The over-voltage detecting means according to claim 1, wherein the over-voltage detecting means comprises a Zener diode.
The power supply as described. 4. The power supply device according to claim 1, wherein said primary side detection means comprises a resistor and a transistor. 5. The power supply device according to claim 1, wherein said stopping means comprises a resistor and a transistor. 6. A power supply device having switching means connected in series to a primary winding of a transformer and performing constant voltage control by feeding back a signal based on a difference between an output voltage on a secondary side and a reference voltage to a primary side. In the output control method, an overvoltage detection step of detecting that the output voltage on the secondary side has exceeded the set voltage, and forcibly stopping the operation of the switching means when the output voltage on the secondary side has exceeded the set voltage. And an output control method in the power supply device. 7. A primary side detection step of detecting a detection signal of the overvoltage detection step on a primary side, and in the stopping step, the operation of the switching means is forcibly performed based on the detection signal of the primary side detection step. The output control method in the power supply device according to claim 6, wherein the output is stopped. 8. The power supply device according to claim 6, wherein in the overvoltage detecting step, a means comprising a zener diode detects that the output voltage on the secondary side has exceeded a set voltage. Output control method. 9. The power supply device according to claim 6, wherein in the primary side detection step, a detection signal of the overvoltage detection step is detected by a unit including a resistor and a transistor. Output control method. 10. The method according to claim 6, wherein in the stopping step, the switching means is forcibly stopped by means including a resistor and a transistor.
An output control method in the power supply device according to any one of the above.