JPH0951673A - Switching power supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching power supply circuit for efficiently supplying a DC voltage obtained from such DC power supply as a battery to a load. SOLUTION: A switching power supply circuit consists of a control transistor 9 which is connected to control the operation of a switching transistor 2 where a collector is connected to an inductance element 4, a diode 8 where an anode is grounded and at the same time a cathode is connected to the collector of the switching transistor 2, a comparison circuit 14 where a reference voltage is inputted to a first input terminal, at the same time a second input terminal is connected to the output side of the inductance element 4, and the output terminal is connected to the base of the control transistor 9, and a reference voltage generation circuit 13 where a DC voltage obtained from a DC power supply is converted to a specific voltage and is outputted and then is applied to the first input terminal of the comparison circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply circuit for efficiently supplying a DC voltage obtained from a DC power supply such as a battery to a load.

[0002]

2. Description of the Related Art An audio device called a disc player, which reads out a signal from a disc on which irregularities corresponding to a digital signal are engraved by using an optical pickup, is widely used. Among such audio devices, there are portable devices that are used by being carried, and such portable devices use a battery as a power source.

In a device that uses a battery as a power source, since the operating time is limited by the life of the battery, a technique for suppressing the amount of use of the battery has been developed. A power supply circuit called a switching power supply is generally known as a technique for efficiently supplying a power supply obtained from a battery to a load.

[0004]

A switching power supply circuit supplies a predetermined DC voltage to a load by using a DC voltage obtained from a battery or the like by utilizing a switching operation by a switching means and a voltage induced by an inductance element. Although it is configured, there is a problem that a circuit for performing voltage control is complicated.

The present invention is intended to provide a switching power supply circuit that solves such a problem.

[0006]

A switching power supply circuit of the present invention includes a switching transistor having an emitter connected to a DC voltage input terminal and a collector connected to a DC voltage output terminal via an inductance element, A control transistor whose collector is connected to its base through a resistor and whose emitter is grounded to control the operation of the switching transistor; and whose anode is grounded and whose cathode is connected to the collector of said switching transistor. And a comparison circuit in which a reference voltage is input to the first input terminal, a second input terminal is connected to the output side of the inductance element, and the output terminal is connected to the base of the control transistor, The DC voltage input terminal A DC voltage obtained by converting a predetermined voltage is more configuration as the reference voltage generating circuit for outputting.

[0007]

According to the present invention, a reference voltage generating circuit for converting a DC voltage obtained from the DC voltage input terminal into a predetermined voltage and outputting the same is provided, and the voltage output from the reference voltage generating circuit controls the operation of the switching transistor. The output voltage output to the DC voltage output terminal is set by applying it as the reference voltage of the comparison circuit that controls the operation of the control transistor connected accordingly.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The circuit shown in FIG. 1 is an embodiment of the switching power supply circuit of the present invention. In the figure, 1 is a DC voltage input terminal to which a DC voltage obtained from a battery or the like is applied,
Reference numeral 2 is a DC voltage output terminal, and a load (not shown) is connected between the terminal 2 and ground.

A switching transistor 6 has an emitter connected to the DC voltage input terminal 1 and a collector connected to the DC voltage output terminal 2 via a first inductance element 4 and a second inductance element 5. Is a first smoothing capacitor connected between the output-side terminal of the first inductance element 4 and ground,
A second smoothing capacitor 7 is connected between the output-side terminal of the second inductance element 5 and the ground, and constitutes a smoothing circuit together with the second inductance element 5.

Reference numeral 8 denotes a diode whose anode is grounded and whose cathode is connected to the collector of the switching transistor 3, and which is connected to the first inductance element 4 when the switching transistor 3 is inverted from the on state to the off state. It has a function of supplying the induced voltage to the DC voltage output terminal 2. Reference numeral 9 is a control transistor whose collector is connected to its base via a resistor 10 and whose emitter is grounded to control the operation of the switching transistor 3, and whose base is the direct current via a resistor 11 and a resistor 12. It is connected to the voltage input terminal 1.

Reference numeral 13 is a reference voltage generating circuit having an input terminal 13A connected to the DC voltage input terminal 1, and has an output terminal 13B for outputting a predetermined DC voltage. 1
Reference numeral 4 denotes a first input terminal that is a + side input terminal connected to the output terminal 13B of the reference voltage generation circuit 13 and a second input terminal connected to the output side of the first inductance element 4. 1 comparator circuit, the output terminal of which is connected to the base of the control transistor 9 via the resistor 11.

A voltage setting circuit 15 is provided between the DC voltage output terminal 2 and the ground and outputs a voltage according to the voltage output to the DC voltage output terminal 2.
It is composed of a diode 16, a resistor 17, and a resistor 18. Reference numeral 19 denotes a + side input terminal having a first input terminal connected to the output terminal 13B of the reference voltage generation circuit 13 and a second input terminal formed by the resistors 17 and 18 forming the voltage setting circuit 15. The second comparison circuit is connected to the voltage dividing point A, and its output terminal is connected to the base of the control transistor 9 via the resistor 11.

Reference numeral 20 is a diode whose anode is connected to the DC voltage input terminal 1 through a resistor 21 and whose cathode is connected to the voltage dividing point A of the voltage setting circuit 15, and 22 is a diode of the diode 20. It is a switch connected between the anode and the ground, and has a function of controlling operation / non-operation of the switching power supply circuit. 23
Is a capacitor connected between the output terminal 13B of the reference voltage generation circuit 13 and the ground, that is, between the first input terminals of the first comparison circuit 14 and the second comparison circuit 19 and the ground,
This serves to suppress the fluctuation of the reference voltage.

The switching power supply circuit of the present invention is configured as described above. Next, the operation of such a circuit will be described. When the DC voltage is applied to the DC voltage input terminal 1 when the switch 22 is in the closed state, the DC voltage is input to the input terminal 13A of the reference voltage generation circuit 13, so that the output terminal 13B thereof is A predetermined voltage is output, and the output voltage is applied to the first input terminals of the first comparison circuit 14 and the second comparison circuit 19 as a reference voltage.

Since the DC voltage from the DC voltage input terminal 1 is applied to the base of the control transistor 9 via the resistors 12 and 11, the control transistor 9 is controlled.
Is turned on, and the switching transistor 3 whose operation is controlled by the control transistor 9 is turned on. The switching transistor 3
When the switching transistor 3 is turned on, the first inductance element 4 and the second inductance element 4
A DC voltage is output to the DC voltage output terminal 2 through the inductance element 5.

When the switching transistor 3 is turned on, a DC voltage is applied from the collector of the switching transistor to the second input terminal of the first comparison circuit 14 through the first inductance element 4. As a result, the voltage output to the output terminal of the first comparison circuit 14 is inverted to L (low) level, and the base potential of the control transistor 9 is lowered, so that the control transistor 9 is turned off. The control transistor 9
Is turned off, the switching transistor 3 whose operation is controlled by the control transistor 9 is turned off.

When the switching transistor 3 is turned off, an induced voltage is generated in the first inductance element 4, and this induced voltage is supplied to the load connected to the DC voltage output terminal 2 through the diode 8. . When the induced voltage obtained from the first inductance element 4 decreases with the passage of time, the DC voltage input to the second input terminal of the first comparison circuit 14 decreases, so the output of the first comparison circuit 14 decreases. The voltage output to the terminal is inverted to H (high) level. As a result, the control transistor 9 is turned on, and the switching transistor 3 is turned on with the inversion operation. When the switching transistor 3 is turned on, a DC voltage is output from the collector of the switching transistor 3 to the DC voltage output terminal 2 through the first inductance element 4 and the second inductance element 5, as described above.

Thereafter, the on / off operation of the switching transistor 3 described above is repeatedly performed and the output operation of the voltage induced from the first inductance element is repeatedly performed, and the output voltage is the first smoothing capacitor 6 and the second smoothing capacitor. The DC voltage output terminal 2 is smoothed by the inductance element 5 and the second smoothing capacitor 7.
Is output to By such an operation, a DC voltage can be supplied to the load connected to the DC voltage output terminal 2, but such a voltage is the same as that of the first comparison circuit 14
Is determined by the comparison operation between the reference voltage input to the first input terminal and the voltage on the output side of the first inductance element 4, the reference voltage input to the first input terminal, that is, the reference voltage generation circuit 13 The voltage value output to the DC voltage output terminal 2 can be freely set by adjusting the voltage output to the output terminal 13B.

As described above, the power supply operation of the switching power supply circuit of the present invention is performed, but if a three-terminal regulator element is used as the reference voltage generation circuit 13, the circuit configuration becomes very simple and the stable output voltage is obtained. Can be obtained as a reference voltage, so that the output voltage of the DC voltage output terminal 2 can be set to an accurate value.

The power supply operation of the switching power supply circuit of the present invention is performed as described above. Next, the output voltage limiter operation will be described. When the output voltage of the DC voltage output terminal 2 is controlled to be equal to or lower than a predetermined voltage value, the voltage at the voltage dividing point A of the voltage setting circuit 15 is equal to or lower than the predetermined value. As a result, the voltage input to the second input terminal of the second comparison circuit 19 is below a predetermined value, and the output of the second comparison circuit 19 is at the H level. Therefore, in such a state, the operation of the control transistor 9 is in a state controlled by the output signal of the first comparison circuit 14, and the power supply control operation described above is performed.

In this state, when the output voltage of the DC voltage output terminal 2 rises above a predetermined voltage value, the voltage at the voltage dividing point A of the voltage setting circuit 15 rises above a predetermined voltage value. It will be. As a result, the second comparison circuit 19 performs the inverting operation, and the signal output to the output terminal thereof is inverted to the L level. Therefore, the first comparison circuit 14
Irrespective of the level of the output signal of the control transistor 9, the control transistor 9 is turned off. As described above, when the output voltage of the DC voltage output terminal 2 rises above a predetermined voltage value, the control transistor 9 is turned off, so that the output voltage of the DC voltage output terminal 2 rises above the set value. It can be prevented. Therefore, the second
The comparison circuit 19 and the voltage setting circuit 15 operate as a limiter circuit of the switching power supply circuit.

Next, the operation for controlling the non-operation of the switching power supply circuit of the present invention will be described. When the switch 22 is closed, the diode 2
Since the anode of 0 is grounded, the H level voltage is not applied to the second input terminal of the second comparison circuit 19, and the power supply operation and the limiter operation described above are performed.

In this state, when the switch 22 is opened, an H level voltage is applied to the second input terminal of the second comparison circuit 19 via the resistor 21 and the diode 20. H is applied to the second input terminal of the second comparison circuit 19.
When a level voltage is applied, the output signal of the second comparison circuit 19 is inverted to the L level, so that the first comparison circuit 1
Regardless of the level of the output signal of 4, the control transistor 9 is turned off. The operation of applying the H-level voltage to the second input terminal of the second comparison circuit 19 is performed when the switch 22 is in the open state. Therefore, if the switch 22 is held in the open state, The control transistor 9 and the switching transistor 3 can be held in the OFF state, and the switching power supply circuit can be made inoperative. Therefore, it becomes possible to control the power supply operation to the load of the switching power supply circuit by the opening / closing operation of the switch 22, and when the opening / closing operation of the switch 22 is electronically controlled, the power supply by the microcomputer is supplied. The control operation can be easily performed.

[0024]

The switching power supply circuit of the present invention is provided with a reference voltage generating circuit for converting a DC voltage obtained from a DC voltage input terminal into a predetermined voltage and outputting the same, and switching the voltage output from the reference voltage generating circuit. Since the output voltage output to the DC voltage output terminal is set by applying it as the reference voltage of the comparison circuit that controls the operation of the control transistor that is connected to control the operation of the transistor, the circuit configuration is simple. It is possible to provide a switching power supply circuit. Further, in the present invention, since the three-terminal regulator is used as the reference voltage generation circuit, the circuit configuration is further simplified and the DC voltage with high accuracy can be supplied to the load.

In the present invention, two first and second comparison circuits for controlling the operation of the control transistor for controlling the operation of the switching transistor are provided, and a voltage control operation is performed by the first comparison circuit. Since the limiter operation for suppressing the voltage rise is performed by the second comparison circuit, the switching power supply circuit in which an abnormal voltage is not output can be configured with a simple circuit configuration.

Further, since the operation / non-operation of the switching power supply circuit is controlled by controlling the level of the signal input to one of the input terminals provided in the second comparison circuit, the circuit configuration is simple. In addition, the present invention has an advantage that the power supply operation can be easily controlled by another circuit.

[Brief description of drawings]

FIG. 1 is an example of a switching power supply circuit of the present invention.

[Explanation of symbols]

 1 DC voltage input terminal 2 DC voltage output terminal 3 Switching transistor 4 First inductance element 5 Second inductance element 6 First smoothing capacitor 7 Second smoothing capacitor 9 Control transistor 13 Reference voltage generation circuit 14 First comparison circuit 15 Voltage Setting circuit 19 Second comparison circuit 22 Switch

Claims (4)

[Claims] 1. A switching transistor having an emitter connected to a DC voltage input terminal and a collector connected to a DC voltage output terminal via an inductance element, and a collector for controlling the operation of the switching transistor. A control transistor connected to its base via an emitter and grounded, a diode connected to the collector of the switching transistor with an anode grounded and a cathode connected to the collector of the switching transistor, and a reference voltage applied to the first input terminal. The DC voltage obtained from the DC voltage input terminal and the comparison circuit in which the second input terminal is connected to the output side of the inductance element and the output terminal is connected to the base of the control transistor Base for converting to voltage and outputting It becomes more voltage generating circuit, the voltage output from the reference voltage generating circuit of the comparison circuit 1
A switching power supply circuit, wherein an output voltage output to the DC voltage output terminal is set by applying the voltage as a reference voltage to an input terminal. 2. A switching transistor having an emitter connected to a DC voltage input terminal and a collector connected to a DC voltage output terminal via an inductance element, and a collector for controlling the operation of the switching transistor. A control transistor connected to its base via an emitter and grounded; a diode connected to the anode of the switching ground and a cathode connected to the collector of the switching transistor; and between the DC voltage output terminal and ground. And a voltage setting circuit for outputting a voltage according to the output voltage of the DC voltage output terminal, the reference voltage being input to the first input terminal, and the second input terminal being connected to the output side of the inductance element. Connected, and its output terminal A first comparator circuit connected to the base of the transistor, a reference voltage is input to a first input terminal, a second input terminal is connected to the voltage setting circuit, and an output terminal thereof is a base of the control transistor. A second comparison circuit connected to the second comparison circuit; and a reference voltage generation circuit that converts a direct current voltage obtained from the direct current voltage input terminal into a predetermined voltage and outputs the predetermined voltage. The reference voltage generation circuit outputs the voltage output from the reference voltage generation circuit. 1. A switching power supply characterized in that the output voltage output to the DC voltage output terminal is controlled by applying a reference voltage to the first input terminal of the first comparison circuit and the first input terminal of the second comparison circuit. circuit. 3. The switching power supply circuit according to claim 1, wherein the reference voltage generation circuit is composed of a three-terminal regulator. 4. The output operation of the DC voltage to the DC voltage output terminal is controlled by controlling the voltage applied to the second input terminal of the second comparison circuit. The switching power supply circuit described.