JPH0951674A - 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 13 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 12 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.

Further, in such a switching power supply circuit, as a method of varying the DC voltage supplied to the load, a method of varying the reference voltage generated by the means for generating the reference voltage is generally used. Such a configuration has a problem that the circuit configuration becomes complicated.

The present invention is intended to provide a switching power supply circuit which solves the above problems.

[0007]

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 reference voltage is input to the first input terminal of the diode and the second input terminal is connected to the output side of the inductance element via a resistor, and the output terminal is connected to the base of the control transistor. The comparison circuit and the direct current The DC voltage obtained from the input terminal is converted into a predetermined voltage is more configuration as the reference voltage generating circuit for outputting.

[0008]

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. An output output to a DC voltage output terminal by applying a reference voltage to a first input terminal of a comparator circuit for controlling the operation of a control transistor connected in a suitable manner and switching the reference voltage applied to the first input terminal. The voltage is switched.

[0009]

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 3 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 DC voltage input terminal via a resistor 11. Connected to 1.

The input terminal 12 is the DC voltage input terminal 1
Is a reference voltage generation circuit connected to the output terminal and is configured to output a predetermined DC voltage to the output terminal. Thirteen
Is connected to the output terminal of the reference voltage generation circuit 12 via the resistor 14 and the second input terminal is connected to the output side of the first inductance element 4 with the resistor 15 The output terminal of the comparison circuit is connected to the base of the control transistor 9.

Reference numeral 16 is a first voltage switching circuit provided between the first input terminal of the comparison circuit 13 and the ground, and is composed of a series circuit of a switch 17 and a resistor 18.
Reference numeral 19 is a second voltage switching circuit provided between the second input terminal of the comparison circuit 13 and the ground, and is composed of a series circuit of a switch 20 and a resistor 21.

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 a direct current voltage is applied to the direct current voltage input terminal 1, the direct current voltage is input to the input terminal of the reference voltage generation circuit 12, so a predetermined voltage is output to the output terminal,
The output voltage is applied as a reference voltage to the first input terminal of the comparison circuit 13 via the resistor 14.

Further, since the DC voltage from the DC voltage input terminal 1 is applied to the base of the control transistor 9 via the resistor 11, the control transistor 9 is turned on, and the operation is controlled by the control transistor 9. The switching transistor 3 is turned on. 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.

When the switching transistor 3 is turned on, a DC voltage is applied from the collector of the switching transistor 3 to the second input terminal of the comparison circuit 13 through the first inductance element 4. As a result, the voltage output to the output terminal of the comparison circuit 13 is inverted to the L (low) level, and the control transistor 9
In order to lower the base potential of the control transistor 9, the control transistor 9 is turned off. When 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 time, the comparison circuit 13
Since the DC voltage input to the second input terminal of
The voltage output to the output terminal of the comparison circuit 13 is inverted to the 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,
As described above, the 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.

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 the reference voltage input to the first input terminal of the comparison circuit 13. Since it is determined by the comparison operation with the voltage on the output side of the first inductance element 4, the voltage value output to the DC voltage output terminal 2 can be freely adjusted by adjusting the reference voltage input to the first input terminal. Can be set to

Although the power supply operation of the switching power supply circuit of the present invention is performed as described above, the use of a three-terminal regulator element as the reference voltage generation circuit 12 greatly simplifies the circuit configuration and stabilizes the output voltage. 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 switching operation will be described. A DC voltage of a predetermined voltage is output to the DC voltage output terminal 2 by the switching operation described above, but the output voltage switching operation is performed by the first voltage switching circuit 16
Is performed by closing the switch 17 constituting When the switch 17 is closed, the voltage output from the reference voltage generation circuit 12 is divided by the resistors 14 and 18 and input to the first input terminal of the comparison circuit 13. Therefore, the comparison circuit 1
Since the reference voltage input to the first input terminal of No. 3 decreases, the DC voltage output to the DC voltage output terminal 2 decreases.

By such an operation, the value of the DC voltage output to the DC voltage output terminal 2 can be switched, but the first voltage switching circuit 16 is provided between the first input terminal of the comparison circuit 13 and the ground. By providing them in parallel, the value of the DC voltage output to the DC voltage output terminal 2 can be variously changed.

The DC voltage output to the DC voltage output terminal 2 can be reduced by closing the switch 17 which constitutes the first voltage switching circuit 16. Next, the second voltage switching circuit 19 is used. The operation when the switch 20 constituting the above is closed will be described. When the switch 20 is closed, the voltage obtained from the output side of the first inductance element 4 is divided by the resistors 15 and 21 and input to the second input terminal of the comparison circuit 13. Become. Therefore, the comparison circuit 13
Since the voltage input to the second input terminal of 1 decreases, the DC voltage output to the DC voltage output terminal 2 increases.

With such an operation, the value of the DC voltage output to the DC voltage output terminal 2 can be switched. However, the second voltage switching circuit 19 is provided between the second input terminal of the comparison circuit 13 and the ground. By providing them in parallel, the value of the DC voltage output to the DC voltage output terminal 2 can be variously changed.

As described above, since the output voltage of the switching power supply circuit can be switched by opening / closing the switch 17 or the switch 20, the switch 17
Alternatively, when the opening / closing operation of the switch 20 is electronically controlled, the power supply voltage switching operation by the microcomputer can be easily performed.

[0025]

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. DC voltage output by applying a reference voltage to the first input terminal of a comparator circuit that controls the operation of a control transistor connected to control the operation of the transistor and switching the reference voltage applied to the first input terminal Since the output voltage output to the terminal is switched, it is possible to provide a switching power supply circuit having a simple circuit configuration.

Further, the switching power supply circuit of the present invention is
A control transistor provided with a reference voltage generation circuit for converting a DC voltage obtained from the DC voltage input terminal into a predetermined voltage and outputting the voltage, and connecting the voltage output from the reference voltage generation circuit to control the operation of the switching transistor. Is applied as a reference voltage to the first input terminal of the comparator circuit for controlling the operation of the comparator circuit and is switched to the DC voltage output terminal by switching the voltage obtained from the output side of the inductance element and applied to the second input terminal of the comparator circuit. Since the output voltage to be output is switched, it is possible to provide a switching power supply circuit having a simple circuit configuration.

Further, according to the present invention, a plurality of first voltage switching circuits connected between the first input terminal and the ground are provided in parallel in order to switch the reference voltage input to the first input terminal of the comparison circuit. Therefore, various output voltage values can be obtained. Further, since a plurality of second voltage switching circuits connected between the second input terminal and the ground are provided in parallel in order to switch the voltage input to the second input terminal of the comparison circuit, it is possible to output various values. The voltage can be obtained.

Further, the switching power supply circuit of the present invention is
Since the voltage input to the first input terminal and the second input terminal of the comparison circuit that controls the operation of the control transistor that is connected to control the operation of the switching transistor is configured to be switched, the number of combinations depends on the switching operation. Different output voltages can be easily obtained.

Further, in the present invention, since the three-terminal regulator is used as the reference voltage generating circuit, the circuit structure is further simplified and the accurate DC voltage can be supplied to the load.

[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 12 Reference voltage generation circuit 13 Comparison circuit 16 First voltage Switching circuit 19 Second voltage switching circuit

Claims (9)

[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 at the first input terminal It is obtained from the DC voltage input terminal and a comparison circuit in which the second input terminal is connected to the output side of the inductance element via a resistor and the output terminal is connected to the base of the control transistor Converts DC voltage to specified voltage A reference voltage generation circuit for outputting, applying a voltage output from the reference voltage generation circuit to the first input terminal of the comparison circuit as a reference voltage, and switching the reference voltage applied to the first input terminal. The switching power supply circuit is characterized in that the output voltage output to the DC voltage output terminal is switched by the. 2. The switching power supply circuit according to claim 1, further comprising a voltage switching circuit including a switch for switching a reference voltage and a resistor between the first input terminal of the comparison circuit and ground. 3. The switching power supply circuit according to claim 2, wherein a plurality of voltage switching circuits are provided in parallel. 4. 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, the collector forms a resistor. 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. It is obtained from the DC voltage input terminal and a comparison circuit in which the second input terminal is connected to the output side of the inductance element via a resistor and the output terminal is connected to the base of the control transistor. Converts DC voltage to specified voltage A reference voltage generation circuit for outputting, by applying the voltage output from the reference voltage generation circuit to the first input terminal of the comparison circuit as a reference voltage and switching the voltage applied to the second input terminal. A switching power supply circuit, wherein an output voltage output to the DC voltage output terminal is switched. 5. The switching power supply circuit according to claim 4, further comprising a voltage switching circuit including a switch for switching an input voltage and a resistor between the second input terminal of the comparison circuit and the ground. 6. The switching power supply circuit according to claim 5, wherein a plurality of voltage switching circuits are provided in parallel. 7. The switching power supply circuit according to claim 1, wherein a 3-terminal regulator element is used as the reference voltage generation circuit. 8. 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, the collector forms a resistor. 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. It is obtained from the DC voltage input terminal and a comparison circuit in which the second input terminal is connected to the output side of the inductance element via a resistor and the output terminal is connected to the base of the control transistor. Converts DC voltage to specified voltage And a reference voltage generating circuit for outputting, wherein the voltage output from the reference voltage generating circuit is applied as a reference voltage to the first input terminal of the comparison circuit and is applied to the first input terminal and the second input terminal. A switching power supply circuit, wherein the output voltage output to the DC voltage output terminal is switched by switching the voltage. 9. A switch for switching a reference voltage between a first input terminal of a comparison circuit and ground, and a first voltage switching circuit including a resistor, and a switch for switching an input voltage between a second input terminal of the comparison circuit and ground. 9. The switching power supply circuit according to claim 8, further comprising a second voltage switching circuit including a resistor and a resistor.