JPH06261537A - Power unit - Google Patents

Abstract

PURPOSE:To reduce the impedance of a capacitor without increasing the capacitance of the capacitor so as to increase the load current of a power unit which lowers the output voltage of commercial power supply by using the capacitor and making an electric current having a frequency higher than that of the commercial power supply to flow to the capacitor by providing an oscillator. CONSTITUTION:An oscillator 4 controls a transistor 2 by outputting a signal having a frequency higher than that of commercial power supply 102. When the transistor 2 is repeatedly turned on and off, a voltage which is obtained by dividing the voltage of the commercial power supply 102 rectified by means of a rectifier circuit 103 by the impedance of the capacitor 1 and resistance of a resistor 3 is generated across the section B. At the same time, the impedance of the capacitor 1 changes depending upon the oscillation frequency of the oscillator 4 and the voltage across the section B also changed. The voltage across the section B is supplied to a load 107 through a constant-voltage circuit 106 after smoothing the voltage by means of the capacitor 106. Therefore, the capacitor 1 allows a large load current to flow even when the capacitor has a small size.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit for general consumer and industrial electric equipment.

[0002]

2. Description of the Related Art In recent years, electric appliances in the home have become multifunctional, and many electronic appliances equipped with microcomputers have been introduced. Electric equipment uses A as its power source
Most of the power is taken from a C100V commercial power supply, but most control circuits such as microcomputers operate at a low voltage of about 5V.
100V must be converted to DC5V.

Various voltage conversion methods include a method using a transformer, a method using a resistor, and a method using a capacitor.

FIG. 5 shows a method of reducing the output voltage by using a capacitor. In the figure, the capacitor 101
Has an impedance that is determined by its capacity and the frequency of the commercial power supply 102 (50 Hz or 60 Hz in Japan), so the rectifier circuit 103 generated at both ends of the capacitor 105.
The voltage that is full-wave rectified by is lower than the voltage of the commercial power supply.

The capacitor 105 is for smoothing the full-wave rectified voltage, and 106 is a constant voltage circuit for the load 1.
This is a circuit for keeping the voltage applied to 07 constant.

The resistor 108 is connected to the commercial power source.
It is for discharging the electric charge remaining in 101 when the circuit is removed, and the resistor 109 is for suppressing the inrush current due to the charging of the capacitor flowing when the power supply circuit is connected to the commercial power supply.

[0007]

Since the voltage drop from the commercial power supply is almost determined by the impedance of the capacitor, the impedance of the capacitor must be set low in order to apply a large current to the load at a low voltage.

However, in the above conventional technique, in order to reduce the impedance of the capacitor, the capacitance of the capacitor must be increased, and therefore the power supply circuit must increase the area of the printed wiring board and the like, and in general, As the capacity of the capacitor increases, its price also increases.

The present invention solves the above problems.
The purpose of this invention is to increase the current that can be passed through the load by lowering the impedance without increasing the capacitance of the capacitor by flowing a power source with a frequency higher than the frequency of the commercial power source into the capacitor using an oscillator.

[0010]

In order to achieve the above object, the power supply device of the present invention is configured as follows.

1. A capacitor for dropping the voltage of a commercial power source, a transistor controlled by an oscillator signal, and a resistor are connected in series, and a rectifying circuit, a smoothing circuit, and a constant voltage circuit are provided. .

2. A plurality of capacitors for dropping the voltage of the commercial power source and a transistor controlled by a signal of an oscillator are connected in series, and a rectifying circuit, a smoothing circuit, and a constant voltage circuit are provided.

3. A plurality of capacitors for dropping the voltage of the commercial power source and a transistor controlled by the signal of the oscillator determined by the frequency control unit are connected in series, and a rectifying circuit, a smoothing circuit, and a constant voltage are provided. It has a circuit.

[0014]

In this configuration, the oscillator controls the current flowing through the capacitor, so that a relatively large load current of low voltage can be taken out from the commercial power supply even with a capacitor having a low capacity.

2. In this configuration, since the oscillator controls the current flowing through the two capacitors, a relatively large load current with a low voltage can be taken out from the commercial power source even with a capacitor having a low capacitance, and a large resistor is required. Since no current flows, heat generation from the power supply device can be suppressed.

3. With this configuration, since the current flowing through the capacitor is controlled by the oscillator, a relatively large load current of low voltage can be taken out from the commercial power source even with a capacitor having a low capacity, and the load voltage can be detected. By changing the oscillation frequency, the load impedance can be controlled and the voltage applied to the load can be kept constant regardless of the load current.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the drawings. Hereinafter, components having the same function will be denoted by the same reference symbols, and description thereof will be omitted.

As shown in the circuit diagram of FIG. 1, the present embodiment has a structure in which the voltage of the commercial power source 102 is generated by the impedance of the capacitor 1 to generate a voltage of about 5 V to 20 V at the point A, as in the conventional example.

Next, the operation will be described. The commercial power source 102 is rectified by the rectifier circuit 103.

Reference numeral 4 denotes an oscillator, which outputs a signal having a frequency higher than that of the commercial power supply, as shown in FIG. 2, and controls the transistor 2 at that frequency.

When the transistor 2 is turned on, the rectifier circuit 1
The current rectified by 03 instantly converts the capacitor 1, the resistor 3, the transistor 2, the resistor 109, and the rectifier 10.
It flows to 3.

Here, the resistor 109 is for limiting the charging current of the capacitor, and the resistor 108 is for discharging the capacitor.

When the transistor is repeatedly turned on / off, a voltage obtained by dividing the rectified commercial power supply voltage by the impedance of the capacitor 1 and the resistance value of the resistor 3 is generated at B. At this time, when the oscillation frequency of the oscillator 4 is low, the impedance of the capacitor 1 is high, so the voltage of B is low, and conversely, when the oscillation frequency is high, the voltage of B is low.

Since the voltage of B contains a large amount of alternating current,
After smoothing with the smoothing circuit (condenser) 105, 106
It is supplied to the load through the constant voltage circuit.

The diode 104 is for preventing reverse flow of the discharge current of the smoothing circuit 105 so that the voltage division of the capacitor 1 and the resistor 3 can be performed well.

Next, a second embodiment of the present invention will be described with reference to the drawings. Hereinafter, components having the same functions as those of the first and second embodiments will be designated by the same reference numerals and the description thereof will be omitted.

This embodiment is constructed as shown in the circuit diagram of FIG. In the present invention, similarly to the conventional example, the voltage of the commercial power source 102 is set to 5 V at the point A by the impedance of the capacitor 1.
Is a configuration for generating a voltage of about 20V from 20V.

Next, the operation will be described. When the transistor 2 is turned on, the current rectified by the rectifier circuit 103 instantly receives the capacitor 1, the capacitor 6, the transistor 2,
It flows to the resistor 109 and then to the rectifier 103.

Here, the resistor 109 is for limiting the charging current of the capacitor, and the resistor 108 is for discharging the capacitor.

When the transistor is repeatedly turned on and off, a voltage obtained by dividing the rectified commercial power supply voltage by the impedance of the capacitor 1 and the impedance of the capacitor 6 is generated at B.

At this time, when the oscillation frequency of the oscillator 4 is low, the impedance of the capacitor 1 increases, so that the load 1
The current that can be passed through 07 decreases, and conversely, when the oscillation frequency increases, the impedance of the capacitor 1 decreases, so the current that can flow through the load 107 increases.

Next, a third embodiment of the present invention will be described with reference to the drawings. Hereinafter, those having the same function will be denoted by the same reference numerals, and the description thereof will be omitted.

The present embodiment is constructed as shown in the circuit diagram of FIG. In the present invention, similarly to the conventional example, the voltage of the commercial power source 102 is set to 5 V at the point A by the impedance of the capacitor 1.
Is a configuration for generating a voltage of about 20V from 20V.

Next, the operation will be described. When the transistor 2 is turned on, the current rectified by the rectifier circuit 103 instantly receives the capacitor 1, the capacitor 6, the transistor 2,
It flows to the resistor 109 and then to the rectifier 103.

When the transistor is repeatedly turned on and off, a voltage obtained by dividing the rectified voltage of the commercial power source by the impedance of the capacitor 1 and the impedance of the capacitor 6 is generated at B, smoothed at 105, and then at a constant voltage. It is supplied to the load 107 via the circuit 106.

A voltage detector 10 detects the voltage applied to the load, and a frequency controller 9 determines the oscillation frequency of the oscillator 8 according to the load voltage and controls the oscillator 8.

That is, when a large amount of current flows through the load 107, the current supplied through the impedance of the capacitor 1 becomes insufficient and the voltage applied to the load 107 drops. Therefore, the oscillation frequency of the oscillator 8 is increased and the capacitor is increased. The impedance of 1 is reduced to increase the current that can flow in the load 107.

On the contrary, when the load current is small, the oscillation frequency of the oscillator 9 is lowered and the impedance of the capacitor 1 is increased to cut unnecessary current.

[0039]

As is apparent from the above description of the embodiments, each invention has the following effects.

1. Since the oscillator can control the current flowing through the capacitor to lower the impedance of the capacitor, a relatively large load current can flow even with a capacitor having a small capacitance.

2. The oscillator controls the current flowing through the capacitor to lower the impedance of the capacitor, and the voltage is divided by the capacitor to drop the voltage.
There is no heat generation as when using a resistor, and a relatively large load current can flow with a capacitor having a small capacity.

3. The oscillator can control the current flowing through the capacitor to lower the impedance of the capacitor, detect the load voltage, and change the frequency of the oscillator when the load voltage drops to lower the impedance of the capacitor. Therefore, a constant load voltage can be supplied even when the load current changes.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power supply device according to a first embodiment of the present invention.

FIG. 2 is a timing chart of the commercial power supply and oscillator output.

FIG. 3 is a circuit diagram of a power supply device according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a power supply device according to a third embodiment of the present invention.

FIG. 5 is a circuit diagram of a conventional power supply device.

[Explanation of reference numerals] 5 resistor 102 commercial power supply 103 rectifier circuit (diode bridge) 106 constant voltage circuit 107 load

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiji Yamaguchi 1006 Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. (72) Mitsuhide Sugibayashi 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A capacitor for dropping the voltage of a commercial power source, a transistor controlled by a signal of an oscillator,
A power supply device in which resistors are connected in series and which has a rectifying circuit, a smoothing circuit, and a constant voltage circuit. 2. A power supply device having a rectifier circuit, a smoothing circuit, and a constant voltage circuit in which a plurality of capacitors for dropping the voltage of a commercial power supply and a transistor controlled by a signal of an oscillator are connected in series. 3. An oscillator controlled by a frequency control unit, a plurality of capacitors for dropping the voltage of a commercial power supply,
A power supply device in which transistors controlled by a signal of the oscillator are connected in series, a rectifier circuit, a smoothing circuit, and a constant voltage circuit are provided, and an oscillation frequency of the oscillator is controlled by a frequency control unit and a voltage detection unit.