JPH09215323A - Switching power source apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance power application coefficient of a voltage drop type or voltage booster type power source apparatus which requires a drive voltage higher than the input voltage Vi for the ON-OFF operation of a switching transistor 3. SOLUTION: When the power source apparatus is to be driven, a switching means 30 is turned ON to feed the power to a control means 10 from an auxiliary converter 20 and when the apparatus is driven, an input voltage Vi is superimposed to an operation voltage and is then fed to the control means 10 by making use of the charge pump effect of the capacitor 50 accompanied by the switching operation of a transistor 3 under the condition that the operation of the auxiliary converter 20 is stopped by turning off the switching means 30, using the auxiliary converter 20 for boosting the input voltage Vi of the power source apparatus to the voltage required for feeding the control means 10, the switch means 30 for controlling the feeding of this voltage to the control means 10, the means for giving an output voltage Vo as the operation voltage required for drive of the transistor 3 to the feeding point of the control means 10 and the capacitor connected between a current input side of a reactor 4 and the feeding point of the control means 10.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a step-down or step-up / step-down switching power supply.

[0002]

2. Description of the Related Art In the above-described step-down type or step-up / down type switching power supply device, the switching transistor often operates in a state in which the power supply voltage on the input side thereof is constantly applied to the switching transistor. A voltage higher than the input voltage is required to drive the gate in the case of the insulated gate type and the base in the case of the bipolar type. In order to generate this voltage in the device, it is customary to incorporate a boost converter to convert the input voltage into a higher voltage and supply the power to the control unit of the switching transistor.

FIG. 3 shows a conventional switching power supply device. The switching power supply shown is a DC power supply 1.
Input voltage Vi received from the output voltage of a constant value lower than that
In the example shown in the figure, which is a step-down type that outputs Vo to the load 2, and receives the input voltage Vi, a field effect type switching transistor 3 turns on / off the current flowing in the reactor 4 in a predetermined cycle, and when the transistor 3 is in the off state. While flowing the freewheeling current through the diode 5 to the reactor 4, the voltage on the current outflow side on the right side in the diagram of the reactor 4 is stabilized by the capacitor 6 and a constant output voltage Vo
Is configured to be taken out as.

The control unit 10 of the switching power supply device, which is shown by a block in the center of the figure, inputs the actual value of the output voltage Vo as usual and controls the switching transistor 3 so as to keep it constant. Since the input voltage Vi is applied to the transistor 3, a voltage higher than the input voltage Vi is required to drive its gate. The step-up type auxiliary converter 20 is for converting the input voltage Vi into this necessary voltage. While turning on / off the current flowing in the reactor 21 receiving the input voltage Vi by the transistor 22,
The pulsating voltage at the right end of the reactor 21 in the figure is taken out via the diode 23, smoothed and stabilized by the capacitor 24, and fed to the control unit 10. At startup, the capacitor 24 is first charged by the input voltage Vi, and then the control unit 10 receives the charging voltage to start ON / OFF control of the transistor 22, which causes the auxiliary converter 20 to enter the operating state and the control unit. Establish supply voltage for 10.

[0005]

In the conventional switching power supply device incorporating the auxiliary converter 20 as described above,
A voltage higher than the input voltage Vi is supplied to the control unit 10 so that the switching transistor 3 can be surely controlled to be opened / closed. However, since the auxiliary converter 20 must be operated during the operation, the switching power supply is consumed by the consumed power. There is a problem that the utilization efficiency of electric power of the entire device is lowered. The rate of this efficiency decrease becomes more remarkable as the output capacity of the power supply device becomes smaller, and if the power consumption of the auxiliary converter 20 is reduced, the physical size becomes large, and the power supply device as a whole also becomes large. Under such circumstances, it is an object of the present invention to improve the power utilization efficiency of a power supply device that requires a higher voltage than an input voltage for controlling a switching transistor.

[0006]

SUMMARY OF THE INVENTION According to the present invention, the above-mentioned problems are solved by a boosting type auxiliary converter for converting an input voltage of a power supply device into a power supply voltage for a control section of a transistor, and a supply voltage of the power supply voltage for the control section. A switch device for starting and stopping, a device for applying an operating voltage suitable for driving a transistor to the power supply point of the control unit, and a capacitor connected between the current inflow side of the reactor and the power supply point of the control unit. The problem is solved by turning on the switch means at the time of starting and feeding power from the auxiliary converter to the control unit, and turning off the switch means after starting to stop the feeding.

According to the present invention, the boosting auxiliary converter supplies power to the control part of the switching transistor only when the switching power supply device is started, and after the start, a power supply voltage is generated from the input voltage by a so-called charge pump system to supply power to the control part. Solves the intended problem. That is, while supplying power to the control unit from the auxiliary converter via the switch means having the above-mentioned configuration, the operating voltage is applied to the power supply point by the voltage applying means, and the power supply point and the current inflow side of the reactor are connected. A capacitor is connected in between for a charge pump, and when the power supply device is started up, the switch means is turned on to supply power from the auxiliary converter to the control section, but after the start-up, the switch means is turned off to operate voltage by the voltage application means. In addition, the charge pump action of the capacitor associated with the on / off operation of the switching transistor feeds the feed voltage obtained by superimposing the input voltage to the control unit.

The operation of the above charge pump will be described below. In the power supply device to which the present invention is applied, the switching transistor that receives the input voltage opens and closes the current that flows in the reactor.When the transistor is off, the freewheeling current flows through the diode to the reactor, but when the transistor is off, the diode Since the potential of the reactor on the current inflow side decreases, the capacitor is charged by the operating voltage applied to the feeding point, and when the transistor turns on, the diode becomes non-conductive and the potential on the current inflow side of the reactor changes. Since the voltage rises to almost the input voltage, the charging voltage of the capacitor cannot be further raised by the input voltage or is boosted to reach the feeding point. In the present invention, after the power supply device is activated, a power supply voltage higher than the input voltage created by the charge pump action is applied to the control unit to control the on / off of the switching transistor.

It is most preferable to use an ordinary mechanical switch or electronic switch as the switch means constituting the present invention, but more simply, only in the direction of giving a boosted output by the auxiliary converter to the control section. A diode that conducts can be used as this switch means, and may also be used if such a diode is included in the auxiliary converter. When using the diode for the switching means, it is possible to turn it off by simply stopping the operation of the auxiliary converter after starting the power supply.
That is, it can be placed in the off state.

Further, the output voltage of the power supply device is used as the operating voltage applied to the power feeding point of the control unit, and the voltage applying means is usually a diode conducting in the direction of applying the operating voltage to the power feeding point. It is advantageous in that the circuit configuration of the device of the invention can be simplified, or a simple stabilized power source such as a so-called series regulator that generates an operating voltage from an input voltage as a voltage applying means, and the operating voltage is applied to a feeding point of a control unit. You may make it provide with the diode which conducts in the direction.

Completion of the start-up of the power supply device can be detected from at least one of the start of the switching operation of the transistor and the rise of the output voltage, and preferably from both of them. As described above, the switch means is turned off to stop the power supply from the auxiliary converter to the control section, but at the same time, stopping the conversion operation itself of the auxiliary converter is advantageous in reducing the power consumption during operation as much as possible. is there.

The present invention is particularly suitable for a step-down or step-up / down type switching power supply device. In the latter case, an auxiliary converter, a switch means, a voltage applying means, and a capacitor are provided for controlling a switching transistor for step-down. To Further, the present invention uses an n-channel type insulated gate transistor or an np
It is particularly suitable when using n-type bipolar transistors.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. 1 and 2 are circuit diagrams showing embodiments in which the present invention is applied to a step-down type and a step-up / down type switching power supply device, respectively, and portions corresponding to those in FIG. The description of the part to be performed will be appropriately omitted.

The main circuit of the step-down switching power supply device of FIG. 1 is the same as that of FIG.
Including a reactor 4, a diode 5 and a capacitor 6,
Transistor 3 that receives input voltage Vi causes reactor 4
The current flowing to the reactor 4 is opened and closed, and when the transistor 3 is off, the output voltage Vo is taken out from the current outflow side of the reactor 4 while allowing the freewheeling current to flow through the reactor 4 through the diode 5. As the switching transistor 3, an n-channel type insulated gate transistor is used as in FIG.

Further, the input voltage Vi is set higher than that by using the step-up auxiliary converter 3 for controlling ON / OFF of the transistor 3 so as to keep the output voltage Vo constant by the control unit 10 and for supplying power to the control unit 10. The point of conversion to the power supply voltage is also the same as in FIG. 3, but the present invention differs from the prior art in that the auxiliary converter 3 is mainly used only when the power supply device is started up. It has a simpler circuit configuration in which the capacitor 24 is omitted from the circuit.

The switch means 30 used in the present invention starts and stops the supply of the power supply voltage generated by the auxiliary converter 20 to the control unit 10. For this purpose, a normal mechanical switch or a so-called electronic switch may be used. However, in order to simplify the circuit, a diode that conducts only in the direction in which the power supply voltage is applied to the control unit 10 may be used, and the diode 23 in the auxiliary converter 20 may also serve as that. When the diode of the switch means 30 is used, it is preferable to turn off the transistor 22 and stop the operation of the auxiliary converter 20 after the power supply device is activated.

In the present invention, the voltage applying means 40 and the capacitor 50 are used for supplying power to the control unit 10 after the power supply device is activated. The voltage applying means 40 applies an operating voltage suitable for driving the gate of the transistor 3 to the feeding point to the control unit 10. In the embodiment of FIG. 1, the output voltage Vo of the power supply device is used as the operating voltage. In addition, as the voltage applying means 40, a diode is used which conducts in the direction of applying the output voltage Vo to the feeding point of the control unit 10. The capacitor 50 is for a so-called charge pump that superimposes the input voltage Vi on the operating voltage, and is connected between the current inflow side on the left side of the reactor 4 in the figure and the feeding point for the control unit 10.

In the present invention, the switch means 30 is turned on at the time of starting the switching power supply device configured as described above, and power is supplied to the control unit 10 from the step-up type auxiliary converter 20. This power supply is stopped by turning it off, and instead, the voltage applying means 40 and the capacitor 50 are made to generate the power supply voltage to the control unit 10. The completion of the start can be detected from the start of switching of the transistor 3 and the rise of the output voltage Vo, but in the example shown in the figure, the potential of the current inflow side of the reactor 4 and the output voltage Vo are given to the control unit 10 to perform the switching operation from the former pulsation. Is detected, and after confirming that the latter has risen sufficiently, the switch means 30 is turned off.

When the transistor 3 starts switching, in its off state, the diode 5 conducts so that a freewheeling current flows through the reactor 4, and the potential on the current inflow side of the reactor 4 decreases, so that the capacitor 50 causes the control unit 10 to operate. When the transistor 3 is turned on next, the potential on the current inflow side of the reactor 4 rises to almost the input voltage Vi and the diode 5 becomes non-conducting state. Due to the pumping action, the charging voltage of the capacitor 50 is further raised by the input voltage Vi, and this is given to the feeding point of the control unit 10 as the feeding voltage after activation which is higher than the input voltage Vi.

After the power supply device is activated, the switch means 30 is turned off to switch the power supply to the control unit 10 from the auxiliary converter 10 side to the above-mentioned voltage supply means 40 and the power supply voltage by the capacitor 50. It is preferable that the auxiliary converter 10 consumes no electric power during normal operation of the power supply device by turning off the transistor 22 to stop the conversion operation. In the embodiment shown in FIG. 1, the completion of startup is detected from the switching operation of the transistor 3 and the rise of the output voltage Vo, so that the input voltage Vi is abnormally lowered due to an unexpected cause during the operation of the power supply device. When the transistor 3 is turned on 100% so as to keep the output voltage Vo at a predetermined value, it is considered as the start-up time, so the auxiliary converter 20 restarts the conversion operation,
The switch means 30 is also turned on. As a result, the normal operation of the power supply device can be continued even when the input voltage Vi drops abnormally.

In the embodiment shown in FIG. 2, the switching power supply device is a step-up / down type which produces the output voltage Vo by stepping up or stepping down the input voltage Vi, and its main circuit is similar to that shown in FIG. 1 by the switching transistor 3 receiving the input voltage Vi. The current flowing through the reactor 4 is opened and closed, but this reactor current can be opened and closed by another switching transistor 7, and the output voltage Vo is supplied from the current outflow side of the reactor 4 to the diode 8
Is taken out and stabilized by the capacitor 6. This power supply device is normally used by switching its operation between step-down and step-up. During step-down operation, the transistor 3 for step-down is turned on and off with the transistor 7 in the off state, and during step-up operation, the transistor 3 is kept in the on state for step-up. The transistor 7 is turned on and off. The diode 5 is for freewheeling the current during the step-down operation.

In this step-up / down power supply device, the auxiliary converter 20, the switch means 30, and the voltage applying means 40 are supplied to supply the control unit 10 with a voltage higher than the input voltage Vi required for opening and closing the step-down transistor 3. And a capacitor 50 is used. The auxiliary converter 20 is shown schematically by blocks in this FIG. 2, the switch means 30 and the capacitor 50 being the same as in FIG. 1, but in the embodiment shown the voltage applying means 40.
A simple stabilized power supply 41, which is, for example, a series regulator that generates an operating voltage from the input voltage Vi, and a diode 42 that applies this operating voltage to the power feeding point of the control unit 10 are used as the power source.

The boosting transistor 7 is of an n-channel type as shown in the drawing, for example, and is connected to the ground side, so that a voltage higher than the input voltage Vi is unnecessary for its operation. It is customary to always keep the step-down transistor 3 in the ON state as described above during the step-up operation for turning the transistor 7 on and off. However, in the present invention, the transistor 3 has a frequency lower than that of the transistor 7, for example, several to 10 minutes. It is possible to reduce the power consumption of the auxiliary converter 20 by causing the switch means 30 and the capacitor 50 to generate the power supply voltage for the control unit 10 by performing the switching operation at the frequency of 1.

Although the switching transistor 3 is an n-channel type insulated gate transistor in both the embodiments shown in FIGS. 1 and 2, the present invention is not limited to the case where an npn type bipolar transistor is used. Can also be applied.

[0025]

As described above, in the switching power supply device of the present invention, a step-up type auxiliary converter for converting an input voltage into a power supply voltage for the control section, a switch means for starting and stopping the supply of the power supply voltage to the control section, The switch means is turned on at the time of starting the device by using a means for applying an operating voltage suitable for driving the transistor to the feeding point of the control section and a capacitor connected between the current inflow side of the reactor and the feeding point of the control section. Then, the auxiliary converter supplies power to the control unit, and after the start-up, the switch means is turned off to stop the power supply. Therefore, when the power supply device is started up, the auxiliary converter supplies power to the control unit. Use the charge pump action that accompanies the switching transistor on / off to make the capacitor generate a power supply voltage higher than the input voltage, and By electricity, and reduce the power consumption of the auxiliary converter can be enhanced power efficiency of the power supply.

The embodiment of the present invention in which the switch means is a mechanical or electronic switch has the advantage that the auxiliary converter can be most reliably disconnected from the control unit after the power supply device is activated. The embodiment in which the diode that conducts in the direction of supplying power to the control unit is used, and further, the embodiment in which the diode in the auxiliary converter is used has the advantage that the circuit configuration of the power supply device can be simplified.

The embodiment in which the output voltage of the power supply device is used as the operating voltage applied to the feeding point of the control section has an advantage that no power is consumed when the operating voltage is generated, and this operating voltage is applied to the feeding point as voltage applying means. The embodiment using the diode conducting in the applying direction has an advantage that the circuit configuration is simple. Further, in the embodiment using a stabilized power supply that generates an operating voltage from the input voltage as the voltage applying means and a diode that conducts in the direction of applying the operating voltage to the power feeding point of the control unit, the voltage required for operating the switching transistor is This is advantageous when you want to set it accurately.

The embodiment in which the completion of the startup of the power supply device is detected from both the start of the operation of the switching transistor and the rise of the output voltage has the advantage that the auxiliary converter can be disconnected from the control unit at the optimum timing by the accurate detection of the completion of the startup. When the input voltage is abnormally lowered due to an unexpected cause, there is an advantage that the power supply from the auxiliary converter to the control unit can be restarted and the operation of the power supply device can be continued. The embodiment in which the switch means is turned off after the start-up is completed and the operation of the auxiliary converter is stopped at the same time is advantageous in reducing the power consumption during the normal operation of the power supply device as much as possible.

[Brief description of drawings]

FIG. 1 is a circuit diagram illustrating a specific circuit when the present invention is applied to a step-down type switching power supply device.

FIG. 2 is a circuit diagram showing a specific circuit example when the present invention is applied to a step-up / down type switching power supply device.

FIG. 3 is a circuit diagram showing an example of a conventional switching power supply device when it is a step-down type.

[Explanation of symbols]

 3 Switching transistor for step-down 4 Reactor 5 Diode for free wheeling 8 Switching transistor for step-up 10 Control unit 20 Auxiliary converter 30 Switch means 40 Diode as voltage applying means 41 Stabilized power supply as voltage applying means 50 Capacitor Vi switching Power supply input voltage Vo Switching power supply output voltage

Claims (9)

[Claims] 1. A switching power supply device for turning on / off a current flowing through a reactor by a switching transistor and taking out an output voltage from a current outflow side of the reactor while flowing a freewheeling current through the diode through the diode when the transistor is off. A boosting auxiliary converter that converts the input voltage of the power supply device into a power supply voltage for the control unit of the transistor, switch means for starting and stopping the supply of the power supply voltage to the control unit, and driving the transistor at the power supply point of the control unit. A means for applying a suitable operating voltage and a capacitor connected between the current inflow side of the reactor and the feeding point of the control unit, and when the device is started, the switch unit is turned on to feed power from the auxiliary converter to the control unit. ， The power supply was stopped by turning off the switch means after starting. Switching power supply device according to claim. 2. The switching power supply device according to claim 1, wherein the device is of a step-down type which produces an output voltage by stepping down an input voltage. 3. The device according to claim 1, wherein the device is a step-up / down type that produces an output voltage by stepping up and stepping down an input voltage, and an auxiliary converter, a switch means, and a voltage applying means for a step-down transistor. A switching power supply device characterized in that a capacitor is provided. 4. A switching power supply device according to claim 1, wherein an n-channel insulated gate transistor is used as the switching transistor. 5. The switching power supply device according to claim 1, wherein an npn-type bipolar transistor is used as the switching transistor. 6. The device according to claim 1, wherein an output voltage of a power supply device is used as an operating voltage for driving a transistor, and the operating voltage is applied as a voltage applying means to a feeding point of a control unit. A switching power supply device characterized in that a conducting diode is used. 7. The device according to claim 1, wherein the voltage applying means comprises a stabilized power source for generating an operating voltage from the input voltage and a diode for applying the operating voltage to the feeding point of the control section. Switching power supply. 8. The power supply from the auxiliary converter to the control unit according to claim 1, wherein completion of startup is detected from at least one of start of switching operation of transistor and rising of output voltage to turn off switch means. A switching power supply device characterized in that the power supply is stopped. 9. The switching power supply device according to claim 1, wherein the switch means is turned off and the conversion operation of the auxiliary converter is stopped after the power supply device is activated.