JPH0568367A - Switching regulator - Google Patents

Abstract

PURPOSE:To reduce power loss and to realize stabilized driving by a constitution wherein a control switch circuit section is turned ON when the positive polarity charging voltage, outputted from a capacitor, exceeds a reference voltage and the charging voltage of the capacitor is applied on a switching element. CONSTITUTION:When a capacitor 34 is charged, a constant current supply 36 operates to charge a capacitor 38 with positive polarity. When the charging voltage of the capacitor 38 sufficiently exceeds the sum of a threshold voltage for actuating a FET 22 and a voltage of reverse polarity induced in an auxiliary winding 42, a voltage detecting section 46 detects the charging voltage and a control switch circuit section 40 is turned ON. Consequently, a voltage sufficiently higher than the threshold voltage is applied on the gate of the FET 22 regardless of the reverse polarity voltage outputted from the auxiliary winding 42, and the FET 22 is positively turned ON. According to the constitution, power loss is reduced at the time of starting the FET 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator, and more particularly to a switching regulator capable of reliably switching and outputting the output of a DC power supply using a switching element.

[0002]

2. Description of the Related Art Conventionally, switching regulators have been widely used in various fields. For example, in OA equipment using a battery or the like as a power source, it is used to convert and output a DC voltage of the battery into an arbitrary voltage. .. Such a switching regulator is required to have high conversion efficiency, which allows the battery power source to be used for a long time.

As one of the switching regulators used for such a purpose, for example, Japanese Patent Laid-Open No. 63-290 is known.
The invention relating to the FET self-excited oscillation converter according to No. 165 is known. In this conventional technique, a DC power supply, a switching element, and a transformer auxiliary winding are connected in series. A voltage is applied to the gate of the FET by using an FET as the switching element and connecting the auxiliary winding of the transformer in a positive feedback phase between the gate and the source of the FET via a capacitor. The passing time of the threshold voltage is shortened.

That is, in the self-excited oscillation converter,
As the charging voltage of the capacitor increases, the voltage applied to the gate of the FET also increases. Then, when the gate applied voltage exceeds a predetermined threshold voltage,
The FET is turned on. This FE
When T is turned on, a voltage is generated in the auxiliary winding due to the load current flowing in the main winding of the transformer, and the voltage of this auxiliary winding is applied between the gate and source of the FET in a positive feedback phase. As a result, the FET is formed so as to accelerate the transition from OFF to ON.

[0005]

As described above, in the conventional self-excited oscillation converter, when the charging voltage of the capacitor rises and the voltage applied to the gate of the FET exceeds the threshold voltage, the FET is turned off. I'm trying to control it on.

However, the turn-on state of the FET in the vicinity of the threshold voltage is extremely unstable,
In such an unstable state, the resistance between the drain and source of the FET has a relatively large value. Therefore, after the FET is turned on near the threshold voltage, it is turned on by the output voltage of the auxiliary winding until it is turned on.
There is a problem in that the switching loss generated in the converter is large, and this is a major factor in reducing the conversion efficiency of the converter.

Further, in the above self-excited oscillation converter, the output voltage of the capacitor is transferred to the FET via the transformer auxiliary winding.
Is applied to the gate of. Usually FET
During the turn-off period, the energy charged in the transformer outputs a voltage of opposite polarity from the auxiliary winding. Therefore, the charging voltage of the capacitor is F
When the total value of the threshold voltage of ET and the voltage of the opposite polarity is exceeded, the FET is turned on.

However, in this self-excited oscillation converter, when the load is light or no, the energy charged in the transformer becomes small, so that the reverse polarity voltage output from the auxiliary winding is short. Disappears in time. Therefore, in this case, the FET is turned on at the time when the charging voltage of the capacitor is charged to the threshold voltage of the FET, so that the time from the turning off of the FET to the turning on of the FET is gradually shortened.

For this reason, there is a problem that when the load operation or the no-load operation is performed, the oscillation output of the converter gradually shifts to the high frequency side and finally becomes uncontrollable.

The present invention has been made in view of such conventional problems, and an object thereof is to provide a switching regulator which has a small power loss and can be stably driven.

[0011]

In order to achieve the above object, the present invention provides a main winding that constitutes a transformer or a choke coil, a switching element that switches a DC input applied to the main winding, and the switching. A control circuit for controlling on / off of an element and controlling a load current flowing in the main winding, wherein the control circuit is charged in a positive polarity by an auxiliary winding of the main winding and a predetermined charging current; A capacitor that outputs the charging voltage, a control switch circuit unit that is turned on when the charging voltage exceeds a predetermined reference value, and is turned off when the switching element is turned off, and the load current exceeds a predetermined value. An OFF control unit for controlling OFF of the switching element, wherein the auxiliary winding, the capacitor and the control switch circuit unit are connected in series with the switching element. A continuous closed-loop circuit for controlling the switching element is constituted, and the switching element for control is turned on to control the switching element by using the charging voltage of the capacitor, and during the on-control period of the switching element, It is characterized in that the capacitor is charged with a reverse polarity by the output voltage of the auxiliary winding, and when the OFF control unit turns off the switching element, the charging voltage with the reverse polarity is reverse biased to the switching element.

[0012]

In the switching regulator of the present invention, the positive charging voltage output from the capacitor is the threshold voltage required to turn on the switching element and the auxiliary winding when the switching element is turned off. When the voltage exceeds a reference value voltage that is set to a sufficiently high value with respect to the total value of the output reverse polarity voltage, the control switch circuit unit is turned on and the charging voltage of the capacitor is applied to the switching element. It is characterized in that it is formed in. As a result, the switching element is not affected by the reverse polarity voltage output from the auxiliary winding and is always turned on at the optimum timing regardless of the normal load, light load, or no load, and the main winding The load current will be applied to the wires.

In particular, the present invention is configured to turn on when the charging voltage of the capacitor becomes sufficiently higher than the total value of the reverse polarity voltage output from the auxiliary winding and the threshold voltage of the switching element. There is. For this reason,
The switching element is surely turned on with a voltage sufficiently higher than the threshold voltage, whereby the power loss at the time of turning on the switching element can be significantly reduced, and a switching regulator with high power conversion efficiency can be formed.

When the switching element is turned on in this way, a positive voltage is output from the auxiliary winding and applied to the switching element, which acts to accelerate the turn-on operation of the switching element. To do.

Thus, while the switching element is on-controlled, the capacitor is charged in the opposite polarity by the voltage output from the auxiliary winding.

Then, when the load current exceeds a predetermined reference value, the off control unit turns off the switching element. At this time, since the charging voltage charged in the capacitor in the opposite polarity is biased in the opposite direction so as to cancel the input capacitance of the switching element,
The switching element is surely turned off within a short time after the turn-off control is started by the off control unit.

Moreover, the control switch circuit section is automatically turned off when the load current is turned off by the switching element. As a result, the capacitor starts charging of the positive polarity by the charging current immediately after the switching element is turned off, and when the charging voltage reaches a predetermined reference value, the control switch circuit unit is turned on again. Become.

At this time, in the conventional switching regulator, since the charging voltage of the capacitor is directly applied to the switching element via the auxiliary winding, there is a case where a voltage of opposite polarity is output from the auxiliary winding and a case where it is not. In the above, there is a problem that a large variation occurs in the time from when the switching element is turned off to when it is turned on, and the switching element oscillates at high frequency under light load and no load.

However, in the present invention, the reference value for turning on the control switch circuit portion is set to a value larger than the total value of the threshold voltage of the switching element and the reverse polarity voltage output from the auxiliary winding. Has been done. Therefore, even when the voltage of opposite polarity is output from the auxiliary winding for a relatively long time after the switching element is turned off, as in the case of the rated load, or when the auxiliary winding is used for light load. Even when the reverse polarity voltage output from the line disappears in a short time after the switching element is turned off, the switching element can be surely turned on at the optimum timing.

As described above, according to the present invention, when the load fluctuates as in the prior art, the time from when the switching element is turned off to when it is turned on next does not fluctuate significantly, and stable switching is achieved. The operation can be performed, and particularly in the case of light load and no load, the oscillation frequency is gradually increased unlike the conventional case, and the abnormal operation such as the loss of control is not generated.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the drawings.

First Embodiment FIG. 1 shows a preferred first embodiment of the switching regulator according to the present invention.

Switching regulator 20 of the embodiment
Is configured to step down the output voltage of the battery 10 and apply it to the load 12.

In this embodiment, the switching regulator 20 is an F switch used as a switching element.
It includes an ET 22 and a control circuit 30 for on / off controlling the FET 22.

The FET 22 has its drain side connected to the plus side of the battery 10 and its source side connected to a smoothing circuit constituted by a main winding 24 of a choke coil and a capacitor 26 via a resistor 23. There is. A commutation diode 28 is connected in parallel to the smoothing circuit.

As a result, the DC output of the battery 10 is controlled to be turned on / off by the switching element 22 and output to the main winding 24 of the choke coil, and further comprises the main winding 24 of the choke coil and the capacitor 26. Is converted into a reduced direct current voltage by the smoothing circuit and applied to the load 12.

Next, the control circuit 30 for controlling the ON / OFF of the FET 22 will be described.

The control circuit 30 of the embodiment is the battery 10
Is applied to the capacitor 34 via the diode 32, and the charging voltage of the capacitor 34 is changed to the control circuit 3
It is configured to be used as a zero power source.

The control circuit 30 of the embodiment includes a constant current source 36, a capacitor 38, a control switch circuit section 40, an auxiliary winding 42 of a choke coil, a resistor 44, and a voltage detecting section 4.
Including 6.

The capacitor 38, the control switch circuit section 40, the auxiliary winding 42, and the resistor 44 are connected in series between the gate and source of the FET 22 to form a closed loop circuit for controlling the switching element.

The constant current source 36 is the capacitor 3
The capacitor 38 is positively charged by using the charging voltage of No. 4 as a power source. The charging voltage of this capacitor 38 is
When the voltage detected by the voltage detection unit 46 exceeds a predetermined reference value, the control switch circuit unit 40 is turned on. As a result, the charging voltage of the capacitor 38 is controlled by the control switch circuit unit 40, the auxiliary winding 42, the resistor 4
4 is applied to the gate of the FET 22.

In the present embodiment, the reference value of the voltage detector 46 is the threshold voltage for driving the FET 22 and the reverse polarity voltage (F) output from the auxiliary winding 42.
It is set to a value sufficiently higher than the total value of (the voltage generated when the ET 22 is turned off) and the FET 22 is reliably turned on by the application of this charging voltage.

In this way, when the FET 22 is turned on and the load current _ID is applied, the main winding 24 and the auxiliary winding 42 of the choke coil are charged with energy by this load current. At the same time, a positive feedback voltage signal is output from the auxiliary winding 42 due to the mutual impedance with the main winding 24.
2 will be on-controlled in an accelerated manner.

In this way, the capacitor 38 is connected to the constant current source 36 by the output voltage of the auxiliary winding 42 applied via the resistor 44, the FET 22 and the resistor 23 while the FET 22 is on-controlled. Is charged in the opposite polarity.

When the FET 22 is on-controlled in this way, the load current I _D simultaneously increases.

In the present embodiment, such an increase in load current is detected as the voltage across the resistor 23, and the detected voltage is applied to the base of the transistor 52 via the resistor 50. Then, when this load current becomes a constant value, the transistor 52 is turned on to short-circuit the gate and source of the FET 22. As a result, the FET 22 is forcibly turned off.

At this time, the charging voltage reversely biased to the capacitor 38 is applied between the source and the gate of the FET 22 via the resistor 23, and the charge stored in the input capacitance of the FET 22 is forcibly discharged. Therefore, when the transistor 52 is turned on, the FET 22 is surely turned off in a short time.

In this way, when the FET 22 is turned off, the load current I _D flowing through the main winding 24 of the choke coil is cut off. As a result, a voltage of opposite polarity is generated in the main winding 24, and at the same time, a voltage of opposite polarity is also output from the auxiliary winding 42.

This reverse polarity voltage is applied to the off control circuit section 60.
The control switch circuit unit 40 is turned off.

In this way, when the FET 22 is controlled to be off, the capacitor 38 is charged to the positive polarity by the constant current source 36 after that, and when the charging voltage reaches the reference value of the voltage detecting section 46, the control switch is turned on again. The circuit section 40 is turned on.

At this time, the reference value of the voltage detecting section 46 is the threshold voltage of the FET 22 as described above.
It is set to a value larger than the total value of the reverse polarity voltage output from the auxiliary winding 42. Therefore, the auxiliary winding 42
When the control switch circuit unit 40 is turned on regardless of whether the reverse polarity voltage is output from
A voltage sufficiently higher than the threshold voltage is applied to the gate of the ET22, and the FET22 is surely turned on.

Therefore, for example, when the load 12 is the rated load and the voltage of opposite polarity is output from the auxiliary winding 42 for a long time, or when the load 12 is a light load, the auxiliary winding 42 is short-circuited. Even when the voltage of the opposite polarity is output only for the time, the FET 22 can always be turned on at the optimum timing without being affected by the state of the load 12.

As described above, the time from when the FET 22 is off-controlled to when it is on-controlled becomes a substantially constant value without being affected by the load, and the FET 22 is light-loaded or overloaded as in the conventional case. The time from being turned off to being turned on is gradually shortened, and abnormal operation such as high frequency oscillation can be prevented.

In the control circuit 30 of the embodiment, the load 1
In order to keep the output voltage applied to 2 constant,
0, 72, a shunt regulator 74, a light emitting diode 76 forming a photo coupler, and a light receiving transistor 7
8 are provided.

The resistors 70 and 72 divide the output voltage and input it to the shunt regulator 74. The shunt regulator 74 is configured to turn on when the divided voltage exceeds a predetermined reference voltage to energize the light emitting diode 76. The light emitting diode 76 is configured to turn on the phototransistor 78 which is optically connected by being energized. The phototransistor 78 has one end connected to the plus side of the consonator 34 and the other end connected to the base of the transistor 52, and is turned on to control the transistor 52 so that the FET 22 is turned on by the same operation as described above. It is configured to control off. Thus, in the switching regulator of the embodiment, the FET 22 is switching-controlled so that the output voltage becomes a predetermined constant voltage.

FIG. 2 shows a specific circuit configuration of this embodiment.

The constant current source 36 of this embodiment includes diodes D4 and D5, resistors R3 and R4, and a transistor Q3. Then, even if the voltage across the capacitor 34 changes,
To ensure that the voltage across resistor R4 is constant, transistor Q
3 is controlled so that a constant current is always supplied to the capacitor 38.

Further, the control switch circuit section 40 is
A pair of self-holding transistors Q4 and Q5
And diodes D6 and D10 connected in the opposite direction to the energization direction of the transistors Q4 and Q5. The pair of transistors Q4 and Q5 are connected so as to function like a thyristor.

Further, the voltage detecting section 46 divides the voltage across the capacitor 34 into a reference voltage and outputs the divided voltage as a resistor R.
5, a Zener diode Z2 is formed in series. Therefore, a constant reference voltage is always output from the anode side of the Zener diode Z2, and this is applied to the base of the transistor Q4 via the resistor R7. Therefore, the transistor Q4 turns on when the charging voltage of the capacitor 38 exceeds the reference voltage of the Zener diode Z2, and maintains the on state together with the transistor Q5.

In this embodiment, the reference voltage set by the Zener diode Z2 is more than the sum of the threshold voltage for turning on the FET 22 and the reverse polarity voltage output from the auxiliary winding 42. It is set to a large voltage.

Further, the control circuit 30 of the embodiment is provided with an OFF control circuit section 60 for surely performing OFF control of the control switch circuit section 40 even under a light load.

The off control circuit section 60 includes resistors R8 and R8.
9. The capacitor C4 and the diodes D7 and D8 are included. When the FET 22 is turned on and a positive voltage is output from the auxiliary winding 42, a current I _CON flows and charges the capacitor C.

When the FET 22 is turned off and the load current is cut off, a voltage of reverse polarity is output from the auxiliary winding 42, a current I _{C OFF} flows through the control circuit section 60, and the capacitor C ₄ is reversed. Charged to polarity. At this time,
The reverse voltage is also biased to the transistor Q5, and I
_Since part of the _{C OFF} current flows, transistor Q5
Is forcibly turned off. In this way, when the transistor Q5 is turned off, the transistor Q4 is also turned off at the same time, and the control switch circuit unit 40 is set to the off state.

In this way, when the FET 22 is turned off, the control switch circuit section 40 of the embodiment is forcibly controlled from the on state to the off state.

At the time of overload, since the energy charged in the main winding 24 of the choke coil is small, the energy of the reverse polarity voltage output from the auxiliary winding 42 is also small. Even in such a case, the charging voltage of the capacitor C ₄ is applied to the transistor Q5 as a voltage of the opposite polarity, so that the control switch circuit unit 40 can be surely off-controlled even during overload.

A series circuit composed of a diode D2 and a Zener diode Z1 is connected in parallel between the gate and source of the FET 22 so as to clamp the voltage applied between the gate and source of the FET 22. As a result, when the voltage output from the auxiliary winding 42 is higher than the voltage clamped in the series circuit of the diode D2 and the Zener diode Z1, the remaining voltage is charged in the capacitor 38 with the opposite polarity, and when the FET 22 is turned off. Will be used for the operation.

When a protective Zener diode is built in the FET 22, the diode Z2 and Zener diode Z1 as shown in FIG. 2 may not be used.

Further, in the constant current source 36, the diodes D4 and D5 may be replaced with one Zener diode. Further, as in this specific example, the charging current may be supplied to the capacitor 38 simply via a resistor without using the constant current source 36. In this case, it is necessary to consider that the off time varies depending on the input voltage.

In the above embodiment, a pair of transistors Q4 and Q5 is used as the control switch circuit section 40, but a PUT (programmable unijunction transistor) or a thyristor may be used if necessary. ..

Next, the operation of this embodiment will be described based on the circuit shown in FIG.

First, when the switching regulator 20 of this embodiment is operated, the output voltage of the battery 10 is charged in the capacitor 34 via the diode 32.

The control circuit 30 uses the capacitor 34 thus charged as a power source to control the switching of the FET 22 as follows.

First, when the capacitor 34 is charged, the constant current source 36 operates to charge the capacitor 38 in the positive polarity.

The charging voltage of the capacitor 38 is F
A threshold voltage for starting the ET22,
When the total value of the reverse polarity voltage generated in the auxiliary winding 42 is sufficiently exceeded, the voltage detection unit 46 detects this and the control switch circuit unit 40 is turned on. As a result, the auxiliary winding 4
Regardless of whether or not the voltage of 2 is output from the opposite polarity, a voltage sufficiently higher than the threshold voltage is applied to the gate of the FET 22, and the FET 22 is reliably turned on.

Therefore, as in the conventional case, the capacitor 38
The power loss at the time of starting the FET 22 can be significantly reduced as compared with the case where the charging voltage of 6 is directly applied to the gate of the FET 22.

That is, as in the conventional case, the capacitor 38
When the charging voltage of is directly applied to the gate of the FET 22, the charging voltage rises, and when the voltage applied to the gate of the FET 22 reaches the threshold voltage, the FET 22
Is turned on. However, the turn-on of the FET 22 in the vicinity of the threshold voltage is in an extremely unstable state, and the power loss thereof is also large. Therefore, in the conventional switching regulator, the power loss at the turn-on operation of the FET 22 is unavoidably increased.

On the other hand, in this embodiment, when the voltage applied to the gate of the FET 22 becomes sufficiently higher than the threshold voltage, the control switch circuit unit 4 is activated.
0 is turned on, and the charging voltage of the capacitor 38 is applied to the FET 22. Therefore, FET2
The 2 will be reliably turned on from the beginning with little power loss.

When the FET 22 is on-controlled in this way, the load current I _D output from the battery 10 becomes
It is supplied to the load 12 via the resistor 23 and the choke coil 24. In this way, when the load current _ID flows in the main winding 24 of the choke coil, the choke coil is charged with magnetic energy, and at the same time, a positive voltage is generated from the auxiliary winding 42. Output voltage is F
A positive feedback action that turns on the ET22 in an accelerated manner works.

In this way, when the FET 22 is on-controlled, the voltage output from the auxiliary winding 42 acts so as to charge the capacitor 38 in the opposite polarity.

Then, the load current I _D gradually increases, and when it exceeds a certain value, the transistor 52 turns on and the FET
22 is turned off. At this time, the capacitor 38 charged in the opposite polarity functions as a power supply for flowing a current that cancels the input capacitance between the source and the gate of the FET 22, and therefore, in a very short time after the transistor 52 is turned on,
The FET 22 is surely turned off.

In this way, when the FET 22 is turned off and the load current I _D is cut off, a voltage of opposite polarity is output from the auxiliary winding 42, whereby the off control circuit section 60 causes the control switch circuit section. 40 is turned off.

Then, the capacitor 3 by the constant current source 36
When the charging of No. 8 is started and this charging voltage exceeds a predetermined reference value, the control switch circuit unit 40 is turned on and the FET2
2 is turned on.

At this time, the reference value is set to a value that is sufficiently larger than the total value of the threshold voltage for turning on the FET 22 and the voltage of the opposite polarity output from the auxiliary winding 42. The time from when is turned off until the capacitor 38 is charged to a predetermined reference voltage is substantially constant regardless of the load state. Therefore, the switching control of the FET 22 can be stably performed even under light load, no load, overload, and the like, and the switching frequency shifts to the high frequency side during light load or overload as in the conventional case. It is possible to reliably prevent the occurrence of a situation such as shifting and loss of control.

As described above, according to the switching regulator of this embodiment, a voltage sufficiently higher than the threshold voltage can be applied to the gate of the FET 22 to turn it on reliably, so that the output of the battery 10 can be efficiently output. It becomes possible to convert into a DC voltage for the load 12, which makes it extremely suitable as a power supply circuit used in, for example, a battery-driven OA device. In addition to this, according to the switching regulator of the present embodiment,
Even if the load 12 is lightly loaded, unloaded, or overloaded, the FET 22 is not affected by this.
Can be driven on / off at a stable frequency.
It is possible to reliably prevent the occurrence of an abnormal situation in which the oscillation frequency for turning on / off the FET 22 increases and the control becomes impossible under no load.

3 to 7 show experimental data of the switching regulator of this embodiment. In this experiment, in the circuit shown in FIG. 2, the control switch circuit unit 40 was provided and the control switch circuit unit 40 was not provided. Then, we asked for data on how the characteristics change. In addition, the data measurement when the control switch circuit unit 40 is not used is shown in FIG.
The circuit shown in (1) except for the control switch circuit section 40, the voltage detection section 46, and the off control circuit section 60 was used.

Here, in FIGS. 3 to 6, the state of the load is changed and the drain and source voltages V _DS (F
The on / off state of the ET22) and the drain current I _D (representing the load current) of the FET 22 were measured.

First, FIG. 3 shows data when a 100% rated load is connected as the load 12. In this case,
The FET 22 reliably and stably switches whether the control switch circuit unit 40 is not used as shown in FIG. 7A or the control switch circuit unit 40 is used as shown in FIG. It was confirmed to operate.

On the other hand, FIGS. 4 and 5 show measured data when the 10% rated load is used as the load 12 and when the load 12 is unloaded.

As shown in FIG. 9A, when the control switch circuit section 40 is not used, the oscillation frequency of the FET 22 gradually increases as the load 12 becomes lighter, and eventually the control becomes uncontrollable. confirmed.

On the other hand, as shown in FIG. 7B, when the control switch circuit section 40 is used, the FET 22 is reliably switching-controlled even when the load 12 is light or no load. It was confirmed that the oscillation frequency became stable.

FIG. 6 shows measurement data when the load 12 is completely short-circuited. As shown in FIG. 7A, when the control switch circuit unit 40 is not used, abnormal operation indicated by arrow 100 was confirmed. That is, even when the FET 22 is off, an abnormal operation occurs in which the load current I _D flows through the FET 22, which causes thermal destruction of the FET 22 and also causes power loss.

On the other hand, as shown in FIG. 6B, when the control switch circuit section 40 is used, such an abnormal operation does not occur at all, and the FET 22 reliably performs switching control at a stable frequency. It was confirmed to be done.

As is clear from the experimental data shown in FIGS. 3 to 6, the switching regulator 2 of the present embodiment.
According to 0, a stable oscillation frequency can be secured under any load condition, and the FET 22
It is confirmed that the can be turned on and off surely.

Further, FIG. 7 is measurement data showing how the conversion efficiency of the switching regulator 20 changes when the load factor is changed.

As shown in the figure, the control switch circuit section 4
If there is no 0, the efficiency decreases as the load factor increases, but as in this embodiment, the control switch circuit unit 40
It was confirmed that the efficiency was almost constant in the case of using, and the efficiency was improved by 7% in the case of 100% rated load. This means that a power supply circuit having a larger output capacity can be realized by using the switching regulator 20 of this embodiment.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist of the present invention.

For example, the switching regulator of this embodiment can also be used as a DC-DC converter.

For example, as shown in FIG. 8, the load circuit of the FET 22 may be connected to the primary winding 80a of the transformer 80 and the load current may be output from the secondary winding 80b. In this case, the output of the secondary winding 80b may be formed so as to be output to the main winding 24 of the choke coil via the rectifying circuit including the diodes 82 and 84.

As a result, it is possible to form a highly efficient DC-DC converter whose oscillation operation is stable without being affected by the load condition.

In each of the above embodiments, the case where the auxiliary winding of the choke coil is used as the auxiliary winding 42 has been described as an example, but the present invention is not limited to this, and the auxiliary winding of the transformer may be used. Good.

FIG. 9 shows such an embodiment.

In the DC-DC converter of this embodiment, the transformer 80 is provided with the auxiliary winding 80c, and the auxiliary winding 80c is provided.
Is used as the auxiliary winding 42 shown in FIG.

With the above structure, it is possible to obtain a highly efficient DC-DC converter which performs stable oscillation operation.

In the above embodiment, the case where the FET 22 is used as the switching element has been described as an example.
The present invention is not limited to this, and for example, a bipolar transistor can be used as a switching element.

In the embodiment shown in FIGS. 8 and 9,
Although the forward type converter has been described as an example, the present invention is not limited to this and can be applied to a flyback type converter.

[0096]

As described above, according to the present invention,
It is possible to obtain a switching regulator that has a small power loss and can operate stably without being affected by a load.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a first preferred embodiment of a switching regulator of the present invention.

FIG. 2 is an electric circuit diagram showing a specific configuration of the switching regulator shown in FIG.

FIG. 3 is measurement data of switching operation at a rated load.

FIG. 4 is measurement data of switching operation at 10% load.

FIG. 5 is measurement data of switching operation under no load.

FIG. 6 is measurement data of switching operation at the time of complete short circuit.

FIG. 7 is a characteristic diagram showing a relationship between a load factor and efficiency.

FIG. 8 is a circuit diagram of a DC-DC converter to which the present invention is applied.

9 is an explanatory diagram of a modified example of the DC-DC converter shown in FIG.

[Explanation of symbols]

10 Battery 12 Load 20 Switching Regulator 22 FET 24 Main Winding 26 Capacitor 30 Control Circuit 34 Capacitor 36 Constant Current Source 38 Capacitor 40 Control Switch Circuit Section 42 Auxiliary Winding 44 Resistance 46 Voltage Detection Section 50 Resistance 52 Transistor
IK012401

Claims (3)

[Claims] 1. A main winding forming a transformer or a choke coil, a switching element for switching a DC input applied to the main winding, an ON / OFF control of the switching element, and a load current flowing in the main winding. And a control circuit for controlling the auxiliary winding of the main winding, a capacitor that is positively charged by a predetermined charging current and outputs the charging voltage, and the charging voltage is a predetermined reference. A control switch circuit unit that is turned on when the value exceeds a value and is turned off when the switching element is turned off; and an off control unit that turns off the switching element when the load current exceeds a predetermined value, The auxiliary winding, the capacitor, and the control switch circuit unit include a closed loop circuit for controlling a switching element connected in series with the switching element. And a switching element for controlling the switching element is turned on by using the charging voltage of the capacitor when the control switch circuit section is turned on.
During the ON control period of the switching element, the capacitor is charged in the opposite polarity by the output voltage of the auxiliary winding, and when the OFF control unit turns OFF the switching element, the charging voltage of the opposite polarity is applied to the switching element. A switching regulator characterized by reverse biasing. 2. The control switch circuit unit according to claim 1, wherein the control switch circuit unit has a value sufficiently larger than a total value of a threshold voltage for turning on the switching element and a reverse polarity voltage output from the auxiliary winding. A switching regulator characterized by setting a reference value. 3. The switching regulator according to claim 1, wherein an FET is used as the switching element.