JPH0746835A - Switching power supply and electronic circuit device equipped with the same - Google Patents

Abstract

PURPOSE:To always make a DC output voltage and a DC source voltage of a control circuit identically practically by a method wherein an inductor element equivalent to the inductor element for eliminating high-frequency spike noise connected to a rectifier part of an output of a secondary winding of a transformer is connected to a rectifier part of a primary winding for a control circuit. CONSTITUTION:A ferrite bead 39 of an L value being about the same as the one of a ferrite bead 32 inserted into a secondary-side rectifier part 31 of a switching regulator 24 is inserted into a rectifier part 35 on the power source side of a control circuit 34. Due to a voltage drop by this ferrite bead 39, a source voltage VC of the control circuit 34 becomes equal substantially to a DC output voltage Vo of a secondary-side output and, as the result, the source voltage VC of the control circuit 34 becomes about 0 when the output voltage Vo approaches 0. In the case when a short-circuiting accident of a load 23 occurs, accordingly, the source voltage VC of the control circuit 34 becomes an operation stop voltage or below. Therefore, a switching control operation of the control circuit 34 is stopped and an overcurrent protection of the switching regulator 24 is executed reliably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device having an insulating switching regulator and an electronic circuit device having the switching power supply device.

[0002]

2. Description of the Related Art Conventionally, a switching power supply device having an insulating switching regulator and an electronic circuit device having the switching power supply device have a circuit configuration as shown in FIG. That is, the power MO is connected in series to the main winding 3 on the primary side of the insulation transformer 2 which constitutes the insulation type switching regulator 1.
The SFET 4 is connected as a switching element, and the secondary winding 5 of the insulating transformer 2 is connected to a rectifying unit 8 including a diode 6 as a rectifying element and a smoothing capacitor 7. Ferrite beads 9 are inserted in the rectifying unit 8 as inductor elements having a relatively low L value in order to suppress high frequency spike noise.

A primary winding 10 for a control circuit is provided on the primary side of the insulating transformer 2 in a phase opposite to that of the main winding 3 and with a winding number substantially equal to that of the secondary winding 5, and a primary winding 10 for a power MOSFET 4 as a switching element is provided. A control circuit 11 for performing switching control is connected to the control circuit primary winding 10 via a rectifying unit 12, and feeds back a detection voltage of a voltage detection circuit 13 for detecting a DC output voltage of the isolated switching regulator 1. The switching duty ratio of the power MOSFET 4 is controlled by comparison with the comparison voltage.

The rectifying section 12 on the side of the control circuit 11 has a diode 1 equivalent to the rectifying section 8 on the secondary side of the insulating transformer 2.
4 and the smoothing capacitor 15.

In such a conventional switching power supply device, the DC power input from the DC power supply circuit 16 is supplied to the main winding 3 of the insulating transformer 2, and the power MOSFET 4 is switched at the duty ratio controlled by the control circuit 11. To generate high-frequency pulsed power in the main winding 3
To induce a pulse current of the same frequency in the secondary winding 5 of the insulation transformer 2, which is rectified by the rectifying unit 8,
A direct current with a constant voltage Vo is taken out from the output terminal.

In order to control the DC voltage Vo at a constant level, the voltage detected by the voltage detection circuit 13 is fed back to the control circuit 11, compared with a comparison voltage, and the switching duty ratio of the power MOSFET 4 is controlled based on the deviation. To do.

Then, in order to provide the operating voltage of the control circuit 11, the primary winding 1 for the control circuit on the primary side of the insulating transformer 2 is provided.
A high frequency pulse current having a phase opposite to that of the high frequency pulse current flowing in the main winding 3 is induced at 0, and is rectified by the rectification unit 12 to be a direct current of a predetermined voltage Vc ′ to control the control circuit 1.
Supply to 1.

[0008]

However, the conventional switching power supply device and the electronic circuit device including the conventional switching power supply device have the following problems. That is, when a short circuit occurs in the load 17 connected to the output terminal of the isolated switching regulator 1, the output impedance becomes 0, so that the voltage detection circuit 13 outputs 0 as the output voltage Vo.
Is detected and the detected voltage is fed back to the control circuit 11. Therefore, the control circuit 11 performs control to increase the on-duty ratio of the power MOSFET 4 to its maximum specified value in order to further increase the output voltage Vo so as to match the comparison reference voltage. An electric current will flow. As a result, the current of the secondary winding 5 of the insulation transformer 2 also rapidly increases, and the output voltage Vo rapidly increases. At the same time, almost the same current as flowing through the secondary winding 5 also flows through the primary winding 10 for the control circuit on the primary side of the insulating transformer 2, and the DC voltage Vc 'on the control circuit 11 side also rises.

Therefore, normally, when such an operation occurs, the control circuit 11 detects that the DC voltage Vc 'becomes an overvoltage, and the control circuit 11 causes the power MOS.
The FET 4 is opened to perform the protective operation to set the secondary voltage Vo to 0. In the case of the above-mentioned conventional example, however, the load 17 is short-circuited and the voltage detection circuit 13 outputs the output voltage Vo = 0.
Even when detecting and feeding back, the inductor element 9 for eliminating high-frequency spike noise is inserted in the rectifying section 8 of the secondary winding 5 of the insulating transformer 2, so that the voltage drop due to this inductor element 9 Therefore, the output voltage Vo can be controlled to be 0 even when a constant current flows in the secondary winding 5.

As a result, a current also flows through the primary winding 10 for the control circuit on the primary side, which has almost the same number of turns as the secondary winding 5, and the rectifying section 12 on the side of the control circuit 11 is similar to the secondary side. Voltage Vc 'because no inductor element is inserted
Does not become 0, and depending on the capacitance of the inductor element 9, a voltage higher than the operation stop voltage may be continuously applied to the control circuit 11 and the overcurrent protection operation may not be applied.

The present invention has been made in view of such conventional problems, and provides a switching power supply device capable of reliably operating a protective operation function in the event of a load short-circuit accident, and an electronic circuit device including the same. With the goal.

[0012]

According to a first aspect of the present invention, in a switching power supply device having an insulation type switching regulator, a switching element is connected to a primary side main winding of a transformer of the insulation type switching regulator, and a primary side of the transformer is connected. The control circuit is connected to the primary winding for the control circuit, which has a phase opposite to that of the main winding, via the rectifier, and the number of turns is almost the same as the primary winding for the control circuit on the secondary side of the transformer. Secondary winding is inserted, the inductor element for high frequency spike noise elimination is connected to the rectification section for the output of the secondary winding, and the inductor element for high frequency spike noise elimination is connected to the rectification section of the primary winding for the control circuit. An almost equivalent inductor element is inserted, the output voltage of the rectification section of the secondary winding of the transformer is detected and fed back to the control circuit, and the switching element It is obtained so as to control the Ti ratios.

According to a second aspect of the present invention, in the switching power supply device according to the first aspect, as the inductor element provided in the primary winding for the control circuit on the primary side, the capacitance thereof causes a short circuit accident on the secondary output side. At this time, the voltage induced in the control circuit primary winding can be reduced to a voltage at which the control circuit does not operate.

According to a third aspect of the invention, in the switching power supply device according to the first or second aspect, ferrite beads are used as the inductor element.

According to a fourth aspect of the present invention, a switching power supply device having an insulating switching regulator, a DC power supply circuit connected to the primary side of a transformer of the insulating switching regulator, and a secondary side of the insulating switching regulator are connected. A primary winding for a control circuit having a phase opposite to that of the main winding, in which a switching element is connected to the primary winding of the transformer, and the switching element is connected to the primary winding of the transformer. The control circuit is connected to the transformer via the rectification section, and the secondary winding of the same number of turns as the control circuit primary winding is inserted in the secondary side of the transformer.
An inductor element for high frequency spike noise elimination is connected to the rectification section for the output of the secondary winding, and an inductor element almost equivalent to the inductor element for high frequency spike noise elimination is inserted in the rectification section of the primary winding for the control circuit. The output voltage of the rectifying section of the secondary winding of the transformer is detected and fed back to the control circuit to control the duty ratio of the switching element.

According to a fifth aspect of the present invention, in the electronic circuit device according to the fourth aspect, as an inductor element provided in the primary winding for a control circuit on the primary side of the switching power supply device, its capacitance is short-circuited to the secondary output side. When an accident occurs, the voltage induced in the primary winding for the control circuit and generated in the rectifier can be reduced to a voltage at which the control circuit does not operate.

According to a sixth aspect of the present invention, in the electronic circuit device according to the fourth or fifth aspect, ferrite beads are used as the inductor element.

[0018]

In the switching power supply device according to the invention of claim 1,
By controlling the duty ratio of the switching element of the isolated switching regulator by the control circuit so that the specified output voltage can be obtained, the high frequency spike noise of the high frequency pulse current of the secondary winding generated by the switching operation of the switching element is suppressed. It is erased by the inductor element to prevent the generation of high frequency ripple.

Then, a voltage drop almost equal to the voltage drop caused by the inductor element inserted in the secondary side rectification section of the insulation transformer is generated in the rectification section connected to the primary winding for the control circuit on the primary side of the insulation transformer. The DC output voltage of the isolated switching regulator and the DC power supply voltage of the control circuit can be made almost always the same by generating them by substantially the same inductor element and using the output of this rectification unit as the power supply of the control circuit. Therefore, it is possible to assemble the circuit by using a circuit element of the control circuit that has a withstand voltage band equivalent to that of the load circuit and is easy to handle.

According to the invention of claim 2, in the switching power supply device of claim 1, as the inductor element provided in the primary winding for the control circuit on the primary side, the capacitance thereof causes a short circuit accident on the secondary output side. Sometimes, the voltage induced in the control circuit primary winding can be reduced to a voltage at which the control circuit does not operate, so that the DC power supply voltage of the control circuit becomes almost zero when the DC output voltage becomes almost zero. Also becomes almost 0, and even when the DC output voltage is lost due to an electrical load short-circuit accident, it is possible to reliably lower the power supply voltage of the control circuit to stop the switching control operation and protect the circuit from overcurrent. it can.

According to the invention of claim 3, in the switching power supply device according to claim 1 or 2, the use of ferrite beads as the inductor element facilitates the adjustment of the L value of the inductor element and improves the reliability of the circuit. Can be achieved.

In the electronic circuit device according to the invention of claim 4, the switching power supply device of claim 1 is provided, and by supplying the DC output to the load, the DC output of a stable voltage can be supplied to the load.

According to a fifth aspect of the present invention, in the electronic circuit device according to the fourth aspect, as an inductor element provided in the primary winding for the control circuit on the primary side of the switching power supply device, its capacitance is short-circuited to the secondary output side. When an accident occurs, the voltage induced in the control circuit primary winding can be reduced to a voltage at which the control circuit does not operate, so that overcurrent protection is provided in the event of a load short-circuit accident. According to the electronic circuit device of the invention of claim 6, which can surely operate, in the electronic circuit device of claim 4 or 5, the secondary winding side of the switching power supply device and the primary winding for the control circuit of the primary side. By using ferrite beads for the inductor element of each rectifier on the wire side, the L value of the inductor element can be adjusted easily, and DC power of stable voltage is supplied to the load. Rukoto can, thereby improving the reliability of the circuit operation.

[0024]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a circuit diagram of a common embodiment of the switching power supply device according to the invention of claims 1 to 3, and FIG.
It is a circuit diagram of a common Example of the electronic circuit device of the invention of claim 6. In FIG. 1, reference numeral 21 indicates a switching power supply device, and this switching power supply device 21
The DC power supply circuit 22 and the electrical load 23 are connected together to form an electronic circuit device.

First, the configuration of the switching power supply device 21 will be described. The switching power supply device 21 includes an insulating type switching regulator 24. The insulating type switching regulator 24 has a power MOSFET 27 connected as a switching element in series with a main winding 26 on the primary side of an insulating transformer 25. A rectifying unit 31 including a diode 29 as a rectifying element and a smoothing capacitor 30 is connected to the secondary winding 28. Ferrite beads 32 are inserted in the rectifying unit 31 as inductor elements having a relatively low L value in order to suppress high frequency spike noise.

Further, the main winding 2 is provided on the primary side of the insulating transformer 25.
6, a control circuit primary winding 33 having a number of turns substantially the same as that of the secondary winding 28 and having a number of turns substantially equal to that of the secondary winding 28 is provided to control the switching of the power MOSFET 27 as a switching element at a high frequency of 50 to 100 kHz. 34
Is connected to the primary winding 33 for the control circuit via the rectification unit 35, feeds back the detection voltage of the voltage detection circuit 36 that detects the DC output voltage of the isolated switching regulator 24, and compares it with the comparison voltage to determine the power. MO
The switching duty ratio of the SFET 27 is controlled.

The rectifying section 35 on the control circuit 34 side is composed of a diode 37 and a smoothing capacitor 38, which are equivalent to the rectifying section 31 on the secondary side of the insulating transformer 25, and ferrite beads 39 are inserted as inductor elements. . As the ferrite beads 39, when the short-circuit accident occurs in the electrical load 23, the L value of the ferrite beads 39 causes almost the same voltage drop as the voltage drop by the ferrite beads 32 of the secondary side rectifying section 31 on the control circuit 34 side. It is generated in the section 35, and as a result, the DC output voltage of the rectification section 35 is selected to be equal to or lower than the operating voltage of the control circuit 34.

The switching power supply device 2 having such a configuration
The DC power supply circuit 22 connected to the input terminal of 1 is usually
The commercial load of 100V or 200V is converted into DC power, and the electric load 23 connected to the output terminal of the switching power supply device 21 is normally driven by 24V DC, such as a digital circuit of an OA device, a lighting device, or the like. It is what is done.

Next, the operation of the switching power supply device having the above configuration and the electronic circuit device having the same will be described. Normally, the DC power supply circuit 22 is AC 100V or 20
0V is converted into 140V or 280V direct current and supplied to the switching power supply device 21. Then, in the switching power supply device 21, the voltage is stepped down by the insulating transformer 25, a control DC power supply of 24V is produced through the rectification unit 31, and this is output to the electric load 23.

Therefore, in the switching power supply device 21, the primary side main winding 26 of the insulation type switching regulator 24 is provided.
Is switched to a high frequency pulsed direct current by the power MOSFET 27 to induce a pulsed direct current of the same frequency in the secondary winding 28 of the insulating transformer 25, which is rectified by the diode 29 of the rectifying unit 31. Smoothed by the smoothing capacitor 30,
It functions to convert a DC input of V or 280V into a DC of 24V and output it.

In the control circuit 34, the high frequency pulsed direct current induced by the control circuit primary winding 33 having substantially the same number of turns as the secondary winding 28 of the insulating transformer 25 is rectified by the diode 37 of the rectifying unit 35. , Smoothing capacitor 38
DC of 24V to 20V smoothed by is supplied as a power source.

The control circuit 34 includes a voltage detection circuit 36.
Monitor the output voltage Vo, and compare this output voltage Vo with a reference voltage that is always set to a predetermined value, that is, normally 24 V, and if the output voltage becomes low, the on-duty ratio of the power MOSFET 27 , And conversely, if the output voltage rises, a switching signal that lowers the on-duty ratio of the power MOSFET 27 is generated,
This controls the switching of the power MOSFET 27 so that the output DC voltage Vo is always constant.

In the DC / DC conversion operation by such switching control, the ferrite beads 32 provided in the secondary side rectification section 31 of the insulation type switching regulator 24 have a high-frequency pulsed DC induced in the secondary winding 28. It eliminates the high frequency spike noise that occurs in the high frequency and suppresses the high frequency ripple, but it has a certain impedance to the high frequency pulse current and reduces the DC pulse voltage. Similarly, the ferrite beads 39 provided in the power supply rectification unit 35 of the control circuit 34 eliminate high frequency spike noise generated in the high frequency pulsed direct current induced in the primary side control circuit primary winding 33, The ferrite beads 3 of the above-mentioned secondary side rectifying unit 31 have a function of suppressing a high frequency ripple component, but with respect to a high frequency pulse current.
It produces as much voltage drop as 2.

Therefore, when a short-circuit accident occurs in the electric load 23, the output impedance becomes 0, and an overcurrent tends to flow to the secondary output side of the switching regulator 24, but a voltage drop occurs in the rectifier 31. If the ferrite beads 32 are not inserted, the secondary winding 2
8, the voltage Vo of the control circuit primary winding 33 also decreases, and the power supply voltage supplied to the control circuit 34 through the rectifying unit 35 decreases to the operating voltage or less to stop the switching operation. , Power MOSFET 27
Protective action should be taken to open.

However, since the ferrite beads 32 are inserted in the secondary side rectification section 32, a voltage drop occurs due to the impedance of the ferrite beads 32, and the voltage drop occurs in the secondary winding 28 accordingly. As a result, the same voltage is generated in the control circuit primary winding 33, and the direct current of the Vc voltage is continuously supplied as a power source to the control circuit 34 directly through the rectifying unit 35.
If the ferrite beads 39 are not inserted in the rectifying section 35, the voltage Vc '(voltage of the conventional example) generated in the control circuit primary winding 33 is directly controlled as shown by the curve A in FIG. Since the voltage is applied as the power supply voltage of the circuit 34, it may continue to be maintained at a voltage higher than the operation stop voltage of the control circuit 34. In that case, the voltage Vo detected by the voltage detection circuit 36 is close to zero. The control circuit 34 is connected to the power MOSFET 27
The control is performed to raise the on-duty ratio to the maximum specified value, and a larger current flows through the main winding 26, which may cause damage to the circuit.

However, in this embodiment, the ferrite beads 39 having the same L value as the ferrite beads 32 inserted in the secondary side rectification section 31 of the switching regulator 24 are also inserted in the rectification section 35 on the control circuit 34 side. Therefore, a voltage drop occurs due to the ferrite beads 39, and as shown by B in FIG. 2, the voltage of the voltage Vc that is substantially equal to the secondary side DC output voltage Vo of the switching regulator 24 is used as the power source of the control circuit 34. Is generated, and as a result, when the output voltage Vo approaches 0, the power supply voltage Vc of the control circuit 34 also becomes almost 0. Therefore, when a short-circuit accident of the electrical load 23 occurs, the power supply voltage Vc of the control circuit 34 can easily fall below the operation stop voltage, the switching control operation of the control circuit 34 is stopped, and the switching regulator 24 is stopped. The overcurrent protection can be surely performed.

Further, in the switching power supply device of this embodiment and the electronic circuit device provided with the switching power supply device, an inductor element such as a ferrite bead is used for eliminating high frequency spike noise, and a voltage corresponding to the voltage drop of the ferrite bead is used. By using the same inductor element such as a ferrite bead to generate a drop in the rectification section on the control circuit side, unlike a voltage drop element such as a resistor, power loss can be suppressed and the circuit characteristics greatly change. It is possible to generate a voltage drop without causing it.

Further, by inserting the inductor element into the rectification section on the control circuit side, it is possible to prevent a large inrush current from flowing through the diode, and it is possible to use a diode having a lower rating as the diode. The circuit cost can be reduced. Also, noise that jumps into the power supply current of the control circuit can be removed, and malfunctions can be prevented.

It should be noted that the present invention is not limited to the above-described embodiment, and the inductor element to be inserted into the rectifying portion of the control circuit is not particularly limited to ferrite beads, and may be another type of inductor element. Good. However, by using ferrite beads, it is easy to construct an inductor element having an effective L value while minimizing circuit loss.

[0040]

As described above, according to the switching power supply device of the first aspect of the present invention, the high frequency spike noise generated on the high frequency pulse current of the secondary winding of the insulating transformer due to the switching operation of the switching element causes the high frequency spike noise. The primary winding for the control circuit on the primary side of the insulation transformer has a voltage drop that is erased by the inductor element inserted in the rectification section and that is almost equal to the voltage drop caused by the inductor element inserted in the secondary side rectification section of the insulation transformer. It is generated by an inductor element that is almost the same as the rectifier connected to the line, and the output of this rectifier is used as the power supply for the switching element control circuit.
Since the switching control of the switching element is performed, the DC output voltage of the isolated switching regulator and the DC power supply voltage of the control circuit can always be made almost the same, and the control circuit normally has the same level as the output load circuit. It is possible to assemble a circuit by using circuit elements in a withstand voltage band that is easy to handle, and the circuit configuration is easy.

According to the invention of claim 2, in the switching power supply device of claim 1, as the inductor element provided in the primary winding for the control circuit on the primary side, the capacitance thereof has a short circuit accident on the secondary output side. The voltage induced in the primary winding for the control circuit when it occurs is set to a level that can be reduced to a voltage at which the control circuit does not operate.
Even when the DC output voltage is lost due to a short circuit of an electric load, the power supply voltage of the control circuit can be surely lowered to surely stop the switching control operation, and the circuit can be protected from an overcurrent.

According to the invention of claim 3, in the switching power supply device of claim 1 or 2, since the ferrite beads are used as the inductor element, the L value of the inductor element can be easily adjusted and the reliability of the circuit is improved. Can be improved.

According to the electronic circuit device of the invention of claim 4,
Since the DC power supply circuit is connected to the switching power supply and the load is connected to the DC output, the DC output of a stable voltage can be supplied to the load. The DC output voltage of the isolated switching regulator and the DC power supply voltage of the control circuit can be made almost always the same, and the control circuit should be constructed using circuit elements in the withstand voltage band that is as easy to handle as the output load circuit. And the circuit configuration is easy.

According to the invention of claim 5, in the electronic circuit device of claim 4, as the inductor element provided in the primary winding for the control circuit on the primary side of the switching power supply device,
The capacity is set so that the voltage induced in the primary winding for the control circuit can be reduced to a voltage at which the control circuit does not operate when a short-circuit accident occurs on the secondary output side. In the case of an accident, the switching power supply device side can surely perform the overcurrent protection operation, and it is possible to surely prevent the overcurrent from continuously flowing to the load and destroying the circuit.

According to a sixth aspect of the present invention, in the electronic circuit device according to the fourth or fifth aspect, the rectifying section of each of the secondary winding side and the primary winding side for the primary side control circuit of the switching power supply device is provided. Since the ferrite beads are used for the inductor element, the L value of the inductor element can be easily adjusted, the DC power having a stable voltage can be supplied to the load, and the reliability of the circuit operation can be improved.

[Brief description of drawings]

FIG. 1 is an electronic circuit diagram of a common embodiment of a switching power supply device according to claims 1 to 6 and an electronic circuit device including the same.

FIG. 2 is a graph showing a relationship between an output voltage and a control power supply voltage of an insulation type switching regulator in the switching power supply device of the above embodiment and an electronic circuit device including the same.

FIG. 3 is a circuit diagram of a conventional switching power supply device and an electronic circuit device including the same.

[Explanation of symbols]

 21 Switching Power Supply Device 22 DC Power Supply Circuit 23 Load 24 Insulation Switching Regulator 25 Insulation Transformer 26 Main Winding 27 Power MOSFET 28 Secondary Winding 29 Diode 30 Smoothing Capacitor 31 Rectifier 32 Ferrite Bead 33 Control Circuit Primary Winding 34 Control Circuit 35 Rectifier 36 Voltage detection circuit 37 Diode 38 Smoothing capacitor 39 Ferrite beads

Claims (6)

[Claims] 1. A switching power supply device having an isolated switching regulator, wherein a switching element is connected to a primary side main winding of a transformer of the isolated switching regulator, and the main winding is provided on the primary side of the transformer. The control circuit is connected to the primary winding for the control circuit of the opposite phase through the rectification unit, and the secondary winding of the same phase and the same number of turns as the primary winding for the control circuit is provided on the secondary side of the transformer. The inductor element for high-frequency spike noise elimination is connected to the rectification unit for the output of the secondary winding, and the inductor element for high-frequency spike noise elimination is almost equivalent to the rectification unit of the primary winding for the control circuit. An inductor element is inserted, the output voltage of the rectification unit of the secondary winding of the transformer is detected and fed back to the control circuit, and A switching power supply device configured to control the duty ratio of a ching element. 2. The switching power supply device according to claim 1, wherein the inductor element provided in the primary winding for the control circuit on the primary side has a capacitance, and when the short-circuit accident occurs on the secondary output side. A switching power supply device characterized in that the voltage induced in the primary winding for the control circuit can be reduced to a voltage at which the control circuit does not operate. 3. A ferrite bead is used as the inductor element, according to claim 1 or 2.
The switching power supply device according to any one of 1. 4. A switching power supply device having an insulating switching regulator, a DC power supply circuit connected to the primary side of a transformer of the insulating switching regulator, and an electrical circuit connected to the secondary side of the insulating switching regulator. In an electronic circuit device including a load, a switching element is connected to a primary side main winding of the transformer, and a primary winding for a control circuit is provided on the primary side of the transformer and has a phase opposite to the main winding. A control circuit is connected to the secondary side of the transformer, and a secondary winding having substantially the same number of turns and the same phase as the primary winding for the control circuit is inserted on the secondary side of the transformer. Is connected to the rectification section for eliminating high frequency spike noise, and the rectification section of the control circuit primary winding for eliminating high frequency spike noise. An electronic device in which an inductor element substantially equivalent to the inductor element is inserted, the output voltage of the rectifying section of the secondary winding of the transformer is detected and fed back to the control circuit, and the duty ratio of the switching element is controlled. Circuit device. 5. The electronic circuit device according to claim 4, wherein as the inductor element provided in the primary winding for the control circuit on the primary side of the switching power supply device, the capacitance thereof causes a short circuit to the secondary output side. The electronic circuit is characterized in that it is induced to the primary winding for the control circuit when the above occurs, and can reduce the voltage generated in the rectification section to a voltage at which the control circuit does not operate. apparatus. 6. The ferrite bead is used as the inductor element, as claimed in claim 4 or claim 5.
The electronic circuit device according to any one of 1.