JP3506216B2 - Switching power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to a so-called AC-D
Suitable as C converter or DC-DC converter
The present invention relates to a switching power supply device to be implemented. [0002] 2. Description of the Related Art Used in portable small electronic devices and the like,
DC current or battery current obtained by rectifying and smoothing AC
DC current from the terry, for example, a high
Frequency switching, and the desired voltage with a small transformer
Switching power supply that converts to high efficiency
Widely used. A typical example of such a switching power supply is
Configuration, the secondary output voltage is detected by the voltage detection circuit
The control circuit responds to the detection result
Control the switching pulse width of the element
Pulse width modulation (PWM) method to obtain side output voltage
A switching power supply of the type is widely used. Another typical switching power supply device is
As a simple configuration, the transformer is
The excitation energy stored in the chamber is changed to the secondary side during the off period.
Output to the control circuit
Generated ringing pulse through a DC cut capacitor
Feedback to the control terminal of the main switching element
Therefore, the main switching element is turned on again.
Ringing choke converter (RCC)
Switching power supply devices are also widely used. The switching power supply of the RCC system
Automatically turns off as the load increases, and
On period is long, that is, the switching frequency decreases
Therefore, since the secondary side output voltage is maintained at a predetermined constant voltage, P
Complex control circuits such as WM switching power supplies
Path is unnecessary and the control circuit is operated.
Power supply circuit to generate the voltage that is the pulse width reference.
Since a path is not required, it is suitable for a low-cost power supply device. FIG. 3 shows a typical example of such an RCC system.
FIG. 2 is an electric circuit diagram of a switching power supply device 1 according to the related art.
You. Rectifying commercial AC by main power circuit (not shown)
The obtained DC current is input between input terminals p1 and p2.
You. This DC current is smoothed by the smoothing capacitor c1.
From the smoothing capacitor c1 to the high level side.
Of the main power supply line 2 of the low-level side
Meanwhile, the main power supply voltage is output. A transformer n is connected between the main power supply lines 2 and 3.
Series circuit of the primary winding n1 and the main switching element q
Is connected. The main switching element q is
For example, bipolar transistors and field-effect transistors
In the example shown in FIG.
This is indicated by a resistor. Between the main power lines 2 and 3
A starting circuit 4 composed of voltage dividing resistors r1 and r2 is connected.
ing. When power is turned on, that is, between input terminals p1 and p2
When the power supply voltage is applied to the
As the voltage, that is, the main power supply voltage rises,
The partial pressure value by the anti-r1 and r2 is
When the threshold voltage, for example, 3 V or more,
The switching element q is turned on, and the primary winding n1 is turned upward in FIG.
Voltage is applied, and the excitation energy is stored.
You. As described later, the main switching element q
ff, the excitation energy causes the secondary winding n2
An upward voltage is induced. At the time of this off,
Leakage inductance between primary winding n1 and other windings n2, n3
The vibration generated by the reactance is the main switching element.
q is provided in parallel between the drain and source of
In the snubber circuit 5 composed of a series circuit with the capacitor c2
Therefore, it is absorbed and removed. DC current induced in the secondary winding n2
Is applied to the smoothing capacitor c3 via the diode d1.
After being smoothed by the smoothing capacitor c3.
Shown from output terminals p3 and p4 via source lines 6 and 7
Output to the load circuit. The output power line 6,
7, a voltage detection circuit 8 is interposed. This voltage
The detection circuit 8 includes a voltage dividing resistor, a photocoupler pc, and the like.
And a light emitting diode of the photocoupler pc.
Mode d2 is turned on at a luminance corresponding to the output voltage.
And the value of the output voltage is fed back to the primary side.
You. The control winding n3 includes a main switching element q
Is on, the voltage is in the same upward direction as the primary winding n1.
Induced and the induced current is a DC cut capacitor c.
4 and the main switching element via a bias resistor r4.
To the gate of child q, whereby the main switch
The gate potential of the switching element q is further raised, and the main switch
Element q is maintained in the on state. Further, when the main switching element q is turned on.
The current induced in the control winding n3 is
4 and the bias resistor r4, the photocoupler pc
Of the capacitor c5 through the phototransistor tr2
To one terminal. The other side of this capacitor c5
Terminal is connected to the low-level main power supply line 3.
Therefore, the higher the secondary output voltage, the higher the charging
The current increases, and the terminal voltage of the capacitor c5 increases.
Rise up. The charging voltage of the capacitor c5 is determined by the main switch.
Control transistor interposed between the gate and source of the
The output voltage is given to the base of the transistor tr1.
The threshold voltage of the control transistor tr1, for example, 0.6V
Then, the control transistor tr1 becomes conductive,
As a result, the gate potential of the main switching element q rapidly increases.
The main switching element q is driven off. Therefore, the secondary output voltage increases.
The output power of the capacitor c5
The pressure rises quickly and the main switching element q turns off quickly.
Be moved. The capacitor c5 also has a control winding n3.
Is induced via the resistor r5.
As a result, a secondary short circuit occurs between the output terminals p3 and p4.
Even if the output voltage of the smoothing capacitor c3 on the
The on period of the switching element q is limited to a predetermined period,
The switching element q is protected. The control winding n3 has the control winding
n3 and the number of turns of the secondary winding n2 are indicated by the same reference numerals.
When the secondary side output voltage is vo, the main switching element
When the child q is turned off, (n3 / n
2) a voltage of vo is induced, which causes the capacitor c
5 is extracted, and the next o of the main switching element q is removed.
A reset operation for n operation is performed. After the main switching element q is turned off, 1
Of the excitation energy stored in the secondary winding n1 to the secondary side.
When the output is completed, mainly the parasitic capacitance of the control winding n3
Ringing occurs between c6 and the control winding n3,
The voltage (n3 / n2) vo is stored in the parasitic capacitance c6.
Electrostatic energy is released, and after 1/4 cycle of vibration
It is converted into the excitation energy of the control winding n3, and then
In order to charge the parasitic capacitance c6, a voltage is applied to the control winding n3.
An upward electromotive voltage of (n3 / n2) vo is generated. Rin
The electromotive voltage, which is a ging pulse, is applied to the main switching element.
Is set to be equal to or higher than the threshold voltage of the
The main switching element q is turned on again by the voltage.
In this way, the switching frequency corresponding to the load is automatically
Number, the main switching element q is continuously turned on / off.
Driven to output a desired secondary output voltage.
Has been established. [0015] SUMMARY OF THE INVENTION Switching power supply device
In most cases, most of the loss
For extracting the charge stored in the parasitic capacitance between the in-source
Required power consumption and transformer iron loss.
Generally, the higher the switching frequency, the higher the switching frequency.
Therefore, as described above, the switching power supply 1
Is that the switching frequency increases as the load becomes lighter.
And the lighter the load, the greater the share of the converted power
Increase the power conversion efficiency and decrease the power conversion efficiency.
is there. On the other hand, in order to solve such a problem,
As another prior art, for example, Japanese Patent Application Laid-Open No. 9-47023
Gazette and Utility Model Registration No. 3039391
Can be The prior art disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 9-47023.
In operation, the control transistor that drives the main switching element off
Another control transistor is provided in parallel with the transistor,
At the time of load, it occurred when the main switching element was turned off.
The induced voltage of the control winding is interlocked with the main switching element.
To a capacitor via a transistor that turns off
The other control transistor by its capacitor.
Turn on the transistor and turn off the main switching element.
Configured to maintain state and reduce switching frequency
are doing. Therefore, a configuration for reducing power consumption is required.
Complicated, cost increases, and the advantages of the RCC method are thin
There is a problem that it becomes. Further, the utility model registration No. 3039391
In the prior art disclosed in Japanese Patent Application Publication No.
In parallel with the resistor, a delay to slow down the ringing pulse
It is configured so that a delay capacitor is interposed. Therefore, in paragraph 0025 of this publication,
Ringing, as described in lines 7-8
The switching cycle only during the period when
Switching frequency at light load
Significantly lower than the switching frequency during loading
There is a problem that you can not. An object of the present invention is to provide a power conversion system with a simple configuration.
Provide switching power supply that can increase efficiency
It is to be. [0021] [Means for Solving the Problems]BookSwitchon according to the invention
The power supply unit transforms during the on period of the main switching element.
The excitation energy stored in the chamber is turned off on the secondary side during the off period.
Output to the output circuit and output to the control winding of the transformer after output is completed.
Generate a ringing pulse with a DC cut capacitor
To the control terminal of the main switching element via
Ringing choke that drives the main switching element on
In a converter type switching power supply device,
Between the control terminal of the main switching element and the primary side power supply line
To bypass the ringing pulse.
A control switching element, said main switch
Of the control switching element at the off timing of the switching element
A sub-control winding for storing electric charge in the control terminal, a diode
Charge accumulation means comprising a resistor and a resistor;
Operation switching means for activating the charge storage means.
The charge accumulated at the off timing causes the main
Even when the switching element turns on, the control switch
The switching element is maintained in the on state, and the ringing pulse is
To prevent on-drive of the main switching element
DoThe operation switching means is a photocoupler.
On the primary side, a phototransistor is connected to the control switch.
Series between the control terminal of the switching element and the charge storage means
When the main power is turned on, the photocoupler
The light emitting diode of is turned off and the phototransistor is turned off.
The power is turned on in the off stateSpecially
To sign. According to the above configuration, the heavy load, which is the normal load,
At loading, charge switching means cannot be operated by operation switching means
The control switching element
off and affected by the control switching element
No, the ringing pulse is a DC cut capacitor
To the control terminal of the main switching element via
The main switching element is turned on, and the switch is
A ching operation is performed. On the other hand, when the load is light, the charge storage
Means are activated to turn off the main switching element.
When the control switching element is turned on,
An electric charge is accumulated at the control terminal, and the electric charge
Even if the switching element is turned on,
The switching element is on for a predetermined time continuously from the off period.
State, bypassing the ringing pulse and
The on driving of the switching element is prevented. Therefore, at light load, the main switching element
Once the child performs the switching operation, the next switching
The operation is performed in the same manner as when the power is turned on. Sand
That is, the startup power obtained by dividing the main power supply voltage by resistance, etc.
The voltage at the control terminal of the main switching element
It gradually changes and the main switching element turns on.
When the threshold voltage reaches a certain threshold voltage, the main switching element is turned on.
You. In this way, under light load, under heavy load
Of the main switching element by the ringing pulse
Stop the restart and restart gently in the same way as when turning on the power.
The switching frequency at light load
The number can be reduced. This allows the main switch
Stored in the floating capacitance between the drain and source of the
Switching frequency such as power required for extracting electric charge
Suppresses proportionally increasing loss and increases light load
Power conversion efficiency can be obtained. In addition, such switching at light load
The frequency drop is controlled by the control switching element
Charge storage means consisting of wires, diodes and resistors;
It can be realized with a simple configuration with the operation switching means. [0027] [0028] [0029] [0030] [0031]Also,According to the above configuration, the main power is turned on.
When the secondary side output voltage is low level,
The light emitting diode of the coupler turns off and the phototransistor
Is turned off, and the power supply rises in a heavy load state. Therefore, the required power amount of the load circuit is large.
The power supply quickly rises,
It is suitable for the use where is required. [0033] DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
FIG.And FIG.The following is a description based on
You. FIG. 1 shows an embodiment of the present invention.Explain
As a reference exampleRCC switching power supply
FIG. 2 is an electric circuit diagram of the device 11. For main power circuit not shown
Therefore, the DC current obtained by rectifying the commercial AC
It is input between the children P1 and P2. This DC current is
This smoothing capacitor is smoothed by the capacitor C1.
From C1, the main power supply line 12 on the high level side
The main power supply voltage is output between the main power supply line 13 on the bell side.
Is done. Voltage is applied between the main power supply lines 12 and 13.
Of the primary main winding N1 of the switch N and the main switching element Q
A column circuit is connected. The main switching element Q
Are, for example, bipolar transistors and field-effect
In the example shown in FIG. 1, the electric field effect
This is indicated by a type transistor. The main power supply line 12,
13, a starter circuit composed of voltage dividing resistors R1 and R2.
14 are connected. Power supply, that is, between input terminals P1 and P2
When the power supply voltage is applied to the output of the smoothing capacitor C1,
As the voltage, that is, the main power supply voltage rises,
The value of the voltage division between the voltage dividing resistors R1 and R2 of the path 14 is determined by the main switch.
Threshold voltage Vth of the switching element Q, for example, 3 V or more.
And the main switching element Q is turned on and the primary of the transformer N
An upward voltage in FIG. 1 is applied to the winding N1.
As a result, the excitation energy is accumulated. As described below,
When the main switching element Q is turned off, the excitation energy
An upward voltage is induced in the secondary winding N2 by the lugi.
It is. At the time of this off, the primary winding N1 and the transformer N
Leakage between the other windings N2, N3 and N4 described later.
The vibration generated by the conductance is the main switching element.
The resistor R3 is provided in parallel between the drain and source of the
Snubber circuit 1 consisting of a series circuit of a capacitor and a capacitor C2
5 to be absorbed and removed. DC current induced in the secondary winding N2
Is applied to the smoothing capacitor C3 via the diode D1.
After being smoothed by the smoothing capacitor C3.
From output terminals P3 and P4 via source lines 16 and 17,
It is output to a load circuit (not shown). The output power line
A voltage detection circuit 18 is interposed between 16 and 17.
You. The voltage detection circuit 18 includes a voltage dividing resistor and a photocoupler.
PC1 and the like, the photocoupler
The light emitting diode D2 of PC1 corresponds to the output voltage.
It is driven to be lit at the luminance and the value of the output voltage is filtered to the primary side.
Back. The control winding N3 includes a main switching element Q
Is on, the voltage is in the same upward direction as the primary winding N1.
Induced, and the induced current is a DC cut capacitor C
4 and the main switching element via a bias resistor R4.
To the gate of child Q, whereby the main switch
The gate potential of the switching element Q is further raised, and the main switch
Element Q is maintained in the on state. When the main switching element Q is on,
The current induced in the control winding N3 is
4 and the bias resistor R4, the photocoupler PC
1 through the phototransistor TR2 and the capacitor C
5 is applied to one terminal. Other than this capacitor C5
Is connected to the low-level main power supply line 13
Therefore, the secondary side output voltage is
The higher the charging pressure, the higher the charging current and the
The terminal voltage of the sensor C5 rises quickly. The capacitor
The charging voltage of C5 is equal to the gate-source voltage of main switching element Q.
To the base of the control transistor TR1
And the output voltage of the control transistor TR1
When the threshold voltage becomes equal to or higher than 0.6 V, for example, the control
The transistor TR1 conducts, thereby causing the main switch
The gate potential of the switching element Q drops rapidly,
The switching element Q is driven off. Therefore, the secondary side output voltage is
The higher the pressure, that is, the lighter the load,
The charging voltage of the sensor C5 rises quickly and the main switching element
Q is quickly turned off and becomes lower than the set voltage
, Ie, the heavier the load, the more the capacitor C5 is charged.
And the ON time of the main switching element Q is longer
Become. The capacitor C5 is also induced by a control winding N3.
The generated current is given via the resistor R5. this
Of the secondary side due to a short circuit between the output terminals P3 and P4
Even if the output voltage of the smoothing capacitor C3 is low,
The ON period of the switching element Q is limited to a predetermined period, and the main switch is turned off.
The protection of the switching element Q is achieved. The control winding N3 includes the control winding
N3 and the number of turns of the secondary winding N2 are indicated by the same reference numerals.
When the secondary output voltage is Vo, the main switching element
When the child Q is turned off, (N3 / N
2) A voltage of Vo is induced, which causes the capacitor C
5 is extracted, and the next o of the main switching element Q is removed.
A reset operation for n operation is performed. After the main switching element Q is turned off, 1
Of the excitation energy stored in the secondary winding N1 to the secondary side.
When the output is completed, the parasitic capacitance mainly included in the control winding N3
Ringing occurs between C6 and the control winding N3.
The voltage (N3 / N2) Vo is stored in the parasitic capacitance C6.
Electrostatic energy is released, and after 1/4 cycle of vibration
It is converted into the excitation energy of the control winding N3, and then again
In order to charge the parasitic capacitance C6, a voltage is applied to the control winding N3.
An upward electromotive voltage of the pressure (N3 / N2) Vo is generated. Re
The electromotive voltage, which is a ringing pulse,
It is set to be equal to or higher than the threshold voltage Vth of the element Q.
The main switching element Q is turned on again by the electromotive voltage.
Is done. In this way, the switch corresponding to the load automatically
At the switching frequency, the main switching element Q is continuously turned on /
is driven off, and a desired secondary output voltage is output.
You. [0043]As a reference exampleSwitching power supply 1
1 is a device on which the switching power supply device 11 is mounted.
Is in the non-standby state during heavy load,
On-board equipment is on standby with the configuration to perform normal RCC operation
In the light load condition, the switching frequency
In order to reduce the temperature, the following configuration is provided.
From the device side, a control signal is given to a control terminal P5.
You. The control terminal P5 and the low-level output power supply
Light emitting diode of the photocoupler PC2
A series circuit of a node D3 and a resistor R6 is connected. I
Therefore, the control signal becomes a high level at the time of non-standby.
And that the light-emitting diode D3 is lit and the load is heavy.
Are output to the primary side. On the other hand, on the primary side, the control transistor
In parallel with TR1, that is, the collector is the main switching element
The emitter of the main switching element Q is connected to the gate of the
Transistor TR3 connected to the
The sub-control winding is connected to the base of the transistor TR3.
The induced voltage of N4 is passed through diode D4 and resistor R7.
Given. A base of the transistor TR3;
The low-level main power supply line 13 is also
The phototransistor TR4 of the photocoupler PC2 is connected.
Have been. Therefore, when a heavy load is not on standby, the
By turning on the light emitting diode D3 of the optocoupler PC2,
The phototransistor TR4 turns on and the transistor TR
3 is turned off and the effect of the transistor TR3 occurs.
However, the control transformer based on the charging voltage of the capacitor C5
From turning on of transistor TR1 to turning on of main switching element Q
f and o of the main switching element Q due to ringing
n, a normal RCC operation as described above is performed. On the other hand, when the standby state is light load,
The light emitting diode D3 of the photocoupler PC2 is turned off,
The transistor TR4 is turned off, and the control transistor
The transistor TR3 is interposed in parallel with the transistor TR1.
become. When the light load is on standby, the main switch
To primary winding N1 of transformer N when switching element Q is on
During the period when energy is accumulated, the sub-control winding N4
Induced voltage in the direction in which the anode of the diode D4 becomes a negative voltage
Voltage is generated and base current does not flow through the transistor TR3.
The transistor TR3 is turned off,
The operation is similar. Further, during the standby for the light load, the main switch is
When the switching element Q is turned off, the sub control winding N4 is induced.
The direction of the electromotive voltage is reversed, and the diode D4
And the base current is supplied to the transistor TR3.
As a result, the transistor TR3 is turned on. At this time,
As described above, since the main switching element Q is already off,
The gate voltage of the main switching element Q is at a low level.
And the collector current of the transistor TR3 hardly flows,
A part of the supplied base current is charged to the base as electric charge.
Stored. On the other hand, the main switching element Q is turned off.
And the primary winding N1 of the transformer N as in the non-standby state.
The stored excitation energy is released to the secondary side, and the
When the release is completed, a ringing pulse is applied to the control winding N3.
Occurs, and at the same time, a ringing pulse is also applied to the sub control winding N4.
appear. The ringing pattern generated in the sub control winding N4
Lus is the reverse bias of diode D4 as described above.
And the base current to the transistor TR3 becomes zero.
However, due to the influence of the above-described base accumulated charge, the transistor
The star TR3 remains for a while after the main switching element Q is turned off.
Keep on. As a result, a voltage generated in the control winding N3 is generated.
Ringing pulse bypassed, main switching element
On activation of Q is prevented. Thus, the main switching element Q is turned on.
During the rest, no voltage is induced in the sub control winding N4.
And no base current is supplied to the transistor TR3
As a result, it is possible to collect
Depending on the current supplied to the
It was gradually consumed, and the accumulated charge on the base became zero
At this point, the transistor TR3 is turned off and the main switch
The switching element Q can be turned on. As a result, the above-described prior art switch is
For the power supply 1As a reference exampleSwitching
In the power supply device 11, a transformer serving as a control switching element is used.
A transistor TR3 and a photocoupler P as an operation switching means
C2 and resistor R6, and a sub-control winding serving as charge storage means
Simple configuration with N4, diode D4 and resistor R7
By simply adding, at the time of non-standby, for example, about 80 kHz
The switching frequency of the
In the power supply unit 1, the frequency rises to 400 to 500 kHz.
The switching power supply 11 of the present invention.
Can be reduced to about several kHz,
The power conversion efficiency can be greatly increased. In addition,
The conventional technique disclosed in Japanese Patent Application Laid-Open No. 9-47023
A transistor TR3, which is a switching element, is provided.
The operation switching circuit of the prior art.
Photocoupler PC2 and resistor R6 corresponding to
Diode D4 and resistor R corresponding to frequency suppression circuit
7 clearly shows that the configuration is greatly simplified.
You. In particular, use the base accumulated charge of transistor TR3
To simplify the configuration for suppressing the oscillation frequency
Notable. The operation is switched between the light load state and the heavy load state.
Instead, the phototransistor PC2 is used.
The transistor TR4 is a transistor that is a control switching element
Between the base, which is the control terminal of TR3, and the main power supply line 13.
The light emitting diode of the photocoupler PC2
The mode D3 is driven to be lit only when the load is heavy. Therefore, the standby state is shorter than the operation state.
Overwhelmingly long, suitable for applications requiring extremely low loss
You. Implementation of the present inventiononeAbout form, in Figure 2
The description is based on the following. FIG. 2 shows an embodiment of the present invention.oneForm switch
FIG. 2 is an electric circuit diagram of a ching power supply device 21. This switch
The switching power supply 21 is the switching power supply 11 described above.
, And corresponding parts are denoted by the same reference numerals,
The description is omitted. Note that this switching
In the power supply device 21, the phototransistor of the photocoupler PC2 is used.
The connection method of the transistor TR4 has been changed.
The transistor TR4 is the control switching element.
The base which is the control terminal of the transistor TR3 and the charge storage
And a resistor R7 which is an output stage of the product means.
ing. Therefore, the light emitting device of the photocoupler PC2 is
The diode D3 will be driven to light at light load.
As a result, the lamp is turned off under heavy load. This gives 2
When the main power is turned on when the secondary output voltage is low,
The diode D3 is turned off, and the phototransistor TR4 is turned off.
off, the power supply will start up under heavy load conditions.
You. For this reason, a fast response is required at the rise of the power supply.
And applications that require a large amount of power at startup.
Suitable. [0057] 【The invention's effect】BookThe switching power supply according to the present invention,
As described above, the ringing choke converter type switch
Switching operation at heavy load in the switching power supply
Means to deactivate the charge storage means.
To turn off the control switching element,
The ringing pulse is not affected by the
Main switching element via DC cut capacitor
To turn on the main switching element
Perform normal switching operation, and at light load
Activates the charge storage means and activates the main switching element.
Control of the control switching element at the off timing of the child
The charge is stored in the terminal and the main switch
Even when the switching element turns on, the control switch
Ringing pulse
To prevent on-drive of the main switching element
ToThe operation switching means is a photocoupler.
On the primary side, a phototransistor is connected to the control switch.
Series between the control terminal of the switching element and the charge storage means
When the main power is turned on, the photocoupler
The light emitting diode of is turned off and the phototransistor is turned off.
Make the power supply start up in the off state. Therefore, when the load is light, it is as if the load is heavy.
Restart of the main switching element by a simple ringing pulse
Is stopped, and the main switching element switches once during the light load.
When switching operation is performed, the next switching operation is
So that it is performed as gently as at
The switching frequency of the switching element can be reduced.
This causes the stray capacitance between the drain and source to accumulate.
Switching frequency, such as the power required to extract
Suppress the loss that increases in proportion to the number
Also, high power conversion efficiency can be obtained. In addition, switching at such a light load
The frequency drop is controlled by the control switching element
Charge storage means consisting of wires, diodes and resistors;
It can be realized with a simple configuration with the operation switching means. [0060] [0061] [0062] [0063]AlsoWhen the required power of the load circuit is large
Power supply rises quickly and high-speed response is required.
It is suitable for various uses.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electric circuit diagram of an RCC type switching power supply according to an embodiment of the present invention. FIG. 2 is an electric circuit diagram of an RCC switching power supply according to another embodiment of the present invention. FIG. 3 is an electrical circuit diagram of a typical prior art switching power supply of the RCC type. [Description of Signs] 11, 21 Switching power supply devices 12, 13 Main power supply line 14 Starter circuit 15 Snubber circuit 16, 17 Output power supply line 18 Voltage detection circuit C1, C3 Smoothing capacitors C2, C4, C5 Capacitor C6 Parasitic capacitance D1 Diode D2 , D3 Light emitting diode D4 Diode (charge storage means) N Transformer N1 Primary winding N2 Secondary winding N3 Control winding N4 Sub-control winding (charge storage means) PC1 Photocoupler PC2 Photocoupler (operation switching means) Q Main switching elements R1, R2 Voltage dividing resistors R3, R5 Resistance R4 Bias resistance R6 Resistance (operation switching means) R7 Resistance (charge storage means) TR1 Control transistor TR2, TR4 Transistor TR3 Transistor (Control switching element)

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-9-47023 (JP, A) JP-A-62-114470 (JP, A) JP-A-3-74190 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) H02M 3/00-3/44

Claims (1)

(57) [Claim 1] The exciting energy stored in the transformer during the on-period of the main switching element is output to the secondary side output circuit during the off-period, and after the output is completed, the transformer is turned off. A ringing pulse generated in the control winding of the switching power supply is fed back to a control terminal of the main switching element via a DC cut capacitor, and the main switching element is turned on. A control switching element interposed between a control terminal of the element and a primary-side power supply line and capable of bypassing the ringing pulse; and storing an electric charge in a control terminal of the control switching element at an off timing of the main switching element. Storage means consisting of a sub-control winding, a diode and a resistor for Operation switching means for activating the charge storage means, wherein the charge stored at the off timing keeps the control switching element in an on state even when the main switching element is turned on, and the ringing pulse is generated. bypass with blocking on driving the main switching element, said operation switching means is a photo coupler, contact the primary side
Wherein the phototransistor is the control switching element
Between the control terminal of
When the main power is turned on , the light emitting diode of the photocoupler
Turns off and the phototransistor is turned off.
A switching power supply characterized in that a power source is started up .