JPH10225103A - Power supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power loss in a switch circuit by arranging a switch in the power supply path to a power source part for a switching regulator to control the switching regulator. SOLUTION: This power supply circuit is provided with a power source part 40 for a switching regulator which supplies the constituent element of a switching regulator 50 with power, a switch circuit 10 which opens and closes the power supply path to supply this power source part 40 for a switching regulator with power, and a switch control circuit 20 which controls the operation of this switch circuit 10. The power supply path of the power source part 40 for a switching regulator to supply the constituent element of a switching regulator 50 with power is opened and closed by the switch circuit 10. This switch circuit 10 is controlled by a switch control circuit 20. Since the current required for the power source part 40 for a switching regulator is small enough, the power loss at the section of the switch circuit 10 to open and close the power supply path is extremely small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power switch circuit in a power circuit using a switching power circuit, and more particularly to a power switch circuit in which an electronic switch such as a semiconductor is operated with low loss.

[0002]

2. Description of the Related Art An example of a conventional power supply circuit using a switching power supply is shown in FIG. A DC power supply such as a dry battery is applied to the switching power supply circuit 3 via the switch circuit 1. The switching power supply circuit 3 converts DC power into DC power by a switching regulator and outputs the DC power. The switch circuit 1 is on / off controlled by a switch control circuit 2 to turn on / off power supply to a switching power supply circuit 3.
Turn off.

As the switch circuit 1, there are cases where a mechanical switch and a semiconductor switch are used. A mechanical switch has a contact resistance r of a switch contact and a flowing current I
Then, I ² × r becomes heat and causes loss. Contact resistance r
Is usually very small and thus has low loss as a switch, but on the other hand, has the disadvantage that it has a large shape, is not easy to control, has problems in chattering and life, and lacks reliability.

[0004]

In order to avoid this, there is a system using a transistor or FET as a switch. However, in this case, there are the following problems. In the case of a transistor, when the saturation voltage of the collector-emitter voltage V _CE is V _sat and the emitter current is I, the loss of the switch is V _sat × I. In the case of an FET, if the drain-on resistance is R _{DS (on)} and the flowing current is I, then I
² × R _{DS (on)} is a loss.

Usually, V _sat is about 1 V, and R _{DS (on)} is 1Ω.
When a large current I flows in either the transistor or the FET, a large loss occurs.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide a power supply circuit having a low-loss switch circuit. Another object of the present invention is to provide a power supply circuit using a switch circuit that is smaller and has a semi-permanent life.

[0007]

According to the present invention, there is provided a power supply circuit using a switching regulator, comprising: a power supply unit for a switching regulator for supplying power to constituent elements of the switching regulator; And a switch circuit for opening and closing a power supply path for supplying power to the switching regulator power supply unit, and a switch control circuit for controlling the operation of the switch circuit.

[0008]

The power supply path of the power supply for the switching regulator, which supplies power to the components of the switching regulator, is opened and closed by a switch circuit. This switch circuit is controlled by a switch control circuit. Since the current required for the power supply for the switching regulator is sufficiently small, the power loss at the switch for opening and closing the power supply path is extremely small. The power consumption of the switch control circuit is also extremely small. Thereby, a power supply circuit having a low-loss switch circuit can be realized.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a principle configuration diagram of a power supply circuit according to the present invention. In the figure, 10 is a switch circuit, 20 is a switch control circuit, and 30 is a switching power supply circuit. The switching power supply circuit 30 includes a switching regulator power supply unit 40 and a switching regulator 50.

FIG. 2 is a configuration diagram showing a specific configuration of each unit in FIG. The switch control circuit 20 is energized as long as there is a dry cell, but this circuit is configured by CMOS logic and consumes very little power. This circuit 20 detects a contact signal of the power switch 21 and
A bias is applied to the transistor 13 of the switch circuit 10 to turn on the FET 11.

The switch circuit 10 includes an FET 11 and a resistor 1
2 and a transistor 13. FET
The drain of the battery 11 is connected to a DC power source such as a dry battery (for example, a battery in which eight AA batteries are connected in series and has an output voltage of 7.2 to 12.8 V), and its gate is connected to a resistor 1
2 and the transistor 1
3 is connected to the collector. The transistor 13 has an emitter connected to the common line, and an output signal of the switch control circuit 20 applied to its base.

Power supply section 40 for switching regulator
Are the comparators 56 and 5 of the switching regulator 50.
And a three-terminal regulator 41 that regulates the output voltage of the switch circuit 10 (the power supply voltage from the dry battery supplied via the FET 11). In addition, U1, U shown in the frame of the switching regulator power supply unit 40
Reference numeral 2 corresponds to the comparators 56 and 58, and the figure shows power supply to these comparators.

In the switching regulator 50, 51 is an FET, 52 is a resistor inserted between the drain and the gate of the FET 51, 53 is a diode, 54 is an inductance, 55 is a capacitor, 56 and 58 are comparators,
57 is a reference voltage, 59 is a transistor, and 60 is a triangular wave generator.

The FET 51 has a drain connected to a DC power supply such as a dry battery, and has a transistor 59 turned on and off.
Turn on / off according to off. The output terminal (source) of the FET 51 is connected to a smoothing circuit including an inductance 54 and a capacitor 55. The output terminal of the smoothing circuit is connected to a power supply line 70 connected to a load. The diode 53 is for preventing a reverse voltage and is connected between the source of the FET 51 and the common line.

The comparator 56 outputs the output of the smoothing circuit and the reference voltage V
_ref (here, 5 V is used as V _ref in order to set the output voltage of the switching regulator 30 to 5 V). The comparison result (binary signal) is applied to a comparator 58 at the next stage.

The comparator 58 compares the output (triangular wave) of the triangular wave generator 60 with the comparison result. The comparison result is input to the base of the transistor 59. Transistor 59
Is connected to the gate of the FET 51, and the emitter is connected to the common line.

The operation in such a configuration will be described below. When power is turned on When the power switch 21 is turned on and a power-on signal is given to the switch control circuit 20, the transistor 10 of the switch circuit 10
Is turned on. When the transistor 10 is turned on, the FET 11 is biased and turned on, and power from the dry battery is supplied to the regulator 41 of the switching regulator power supply unit 40.

As a result, the switching regulator 50 starts operating and supplies power to the power supply line 70. Since the switching regulator 50 itself has a known configuration, the description of its operation will be omitted.

When the power is turned off When the power switch 21 is turned off and a power-off signal (Low level signal) is given to the switch control circuit 20, the output of the switch control circuit 20 causes the switch circuit 1 to output a signal.
The 0 transistor 10 is turned off. When the transistor 10 is turned off, the FET 11 is also turned off, and the power supply to the regulator 41 of the switching regulator power supply unit 40 is cut off.

As a result, the comparators 56 and 58 of the switching regulator 50 and the triangular wave generator 60 do not operate, and the transistor 59 is turned off. Therefore, the FET 51 is turned off, and the power supply to the power supply line 70 is cut off.

Power can be supplied and cut off as described above. Here, a comparison of the power loss of the switch unit between the conventional system and the power supply circuit of the present invention is as follows.

For example, a case where a silicon P-channel MOSFET having general specifications is used will be described as an example. The case where the conventional switch circuit shown in FIG. 3 is configured is as follows. The drain-on resistance R _{DS (on)} of this MOSFET is 0.7Ω, and when a switch current I of 1 A flows there, a loss of 0.7 × 1 = 700 (mW) occurs in the switch section.

In the present invention, the FET 1 of the switch circuit 10
1 flows through the regulator 41 and the comparators 56 and 5.
8 and the operating current of the triangular wave generator 60 only,
mA. Therefore, the power loss in the FET 11 is about 0.7 × 0.012 = 8.4 (mW).

It should be noted that the foregoing description has been directed to specific preferred embodiments for the purpose of illustration and illustration of the invention. Therefore, the present invention is not limited to the above-described embodiments, and includes many more modifications without departing from the spirit thereof.
This includes deformation.

For example, the signal to the switch control circuit 20 may be a logic signal instead of an on / off signal by a mechanical switch. In addition, F of the switch circuit 10
ET11 may be replaced by a PNP transistor.

[0026]

As described above, according to the present invention, the following effects can be obtained. According to the present invention, a power supply unit 4 for a switching regulator that controls a switching regulator, instead of arranging a power switch in a main power path.
A switch was placed in the power supply path to zero. This makes it possible to easily realize a switch circuit capable of reducing power loss, improving reliability, and reducing size.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle configuration of a power supply circuit according to the present invention.

FIG. 2 is a configuration diagram showing a specific example of a power supply circuit according to the present invention.

FIG. 3 is a configuration diagram illustrating an example of a conventional power supply circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 switch circuit 11, 51 FET 12, 52 resistor 13, 59 transistor 20 switch control circuit 21 power switch 30 switching power supply circuit 40 switching regulator power supply unit 50 switching regulator 60 triangular wave generator 70 power supply line

Claims (3)

[Claims] 1. A power supply circuit using a switching regulator, comprising: a power supply section for a switching regulator for supplying power to constituent elements of the switching regulator; and a power supply path for supplying power to the power supply section for the switching regulator. And a switch control circuit for controlling the operation of the switch circuit. 2. The power supply circuit according to claim 1, wherein said switch circuit is configured to open and close a power supply path by an FET. 3. The power supply circuit according to claim 1, wherein the switch control circuit uses a CMOS logic so as to reduce power consumption.