JP3266968B2 - Power supply - Google Patents

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 consumer and industrial electric equipment.

[0002]

2. Description of the Related Art In recent years, electronic devices in homes have become more multifunctional, and many electronic devices equipped with microcomputers have been introduced. Electrical equipment uses A
Most of the power comes from a commercial power supply of C100V, but most control circuits such as microcomputers operate at a low voltage of about 5V.
100V must be converted to 5V DC.

There are various methods of converting the voltage, such as a method using a transformer, a method using a resistor, and a method using a capacitor.

FIG. 5 shows a method for lowering the output voltage using a capacitor. In FIG.
Has an impedance determined by its capacity and the frequency of the commercial power supply 102 (50 Hz or 60 Hz in Japan).
The voltage that has been full-wave rectified at this time drops below the voltage of the commercial power supply.

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

The resistor 108 is connected to a commercial power source.
The resistor 109 is for discharging the charge remaining in the capacitor 101 when the circuit is disconnected, and the resistor 109 is for suppressing the rush 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 to apply a low voltage and a large current to the load.

However, in the above-mentioned conventional technology, 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 generally, As the capacity of the capacitor increases, its price also increases.

The present invention solves the above problems,
An object of the present invention is to reduce the impedance without increasing the capacity of the capacitor and increase the current that can be passed to the load by supplying a power supply having a frequency higher than the frequency of the commercial power supply to the capacitor using an oscillator.

[0010]

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

1. Rectifier circuit for rectifying commercial power, and rectifier
Connected in series with the rectifier circuit to reduce the voltage
And the other end of the capacitor via a resistor.
Switching element, and the switching element
Oscillator that controls oscillation at a frequency higher than the frequency of the power supply
And a rectifier on the connection side of the capacitor and the resistor
It has a connected smoothing circuit and a constant voltage circuit.

2. Rectifier circuit for rectifying commercial power, and rectifier
Small in series with the rectifier circuit to reduce the
At least two capacitors and the other end of the capacitor
Connected switching element and this switching element
Oscillation control at a frequency higher than the frequency of the commercial power supply
Where there is a connection between the vibrator and the plurality of capacitors
And a constant voltage circuit connected via a rectifier .

3. The oscillation frequency of the oscillator is varied according to the control content of the frequency control unit for controlling the frequency based on the detection result of the voltage detection unit for detecting the load voltage.

[0014]

1. In this configuration, since the current flowing through the capacitor is controlled by the oscillator, a relatively large load current of a low voltage can be taken out of the commercial power supply even with a capacitor having a low capacitance.

2. In this configuration, since the current flowing through the two or more capacitors is controlled by the oscillator, a relatively large load current of a low voltage can be taken out from the commercial power supply even with a capacitor having a low capacitance, and the resistor can be used. Since a large current does not flow through the power supply device, heat generation from the power supply device can be suppressed.

3. In this configuration, since the current flowing through the capacitor is controlled by the oscillator, a relatively large load current of a low voltage can be taken out from a commercial power supply even with a capacitor having a low capacitance, and the load voltage is detected. The load impedance can be controlled by changing the oscillation frequency, 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 are denoted by the same reference numerals, and description thereof is omitted.

In this embodiment, as shown in the circuit diagram of FIG. 1, similarly to the conventional example, the voltage of the commercial power supply 102 is generated at the point A by the impedance of the capacitor 1 from about 5 V to about 20 V.

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

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

When the transistor 2 is turned on, the rectifier circuit 1
The current rectified at 03 is instantaneously applied to the capacitor 1, the resistor 3, the transistor 2, the resistor 109, and the rectifier 10
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 repeats ON / OFF, a voltage obtained by dividing the rectified voltage of the commercial power supply by the impedance of the capacitor 1 and the resistance value of the resistor 3 is generated at B. Since the oscillation frequency at this time oscillator 4 increases lower the impedance of the capacitor 1, the voltage of the B becomes low and conversely the oscillation frequency increases, the voltage of B is high <br/> Kunar.

Since the voltage of B contains a large amount of alternating current,
After smoothing by the smoothing circuit (capacitor) 105, 106
Is supplied to the load via the constant voltage circuit.

The diode 104 is for preventing the discharge current of the smoothing circuit 105 from flowing backward, so that the voltage division between 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 are denoted by the same reference numerals, and the description thereof will be omitted.

[0027] The present embodiment is configured as shown in the circuit diagram of FIG. According to the present invention, the voltage of the commercial power
From about 20V.

Next, the operation will be described. When the transistor 2 is turned on, the current rectified by the rectifier circuit 103 is instantaneously applied to the capacitor 1, the capacitor 6, the transistor 2,
The current flows to the resistor 109 and 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 is generated at B by dividing the rectified voltage of the commercial power supply by the impedance of the capacitor 1 and the impedance of the capacitor 6.

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

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

[0033] The present embodiment is configured as shown in the circuit diagram of FIG. According to the present invention, the voltage of the commercial power
From about 20V.

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

When the transistor is repeatedly turned ON / OFF, a voltage obtained by dividing the rectified voltage of the commercial power supply by the impedance of the capacitor 1 and the impedance of the capacitor 6 is generated at B, smoothed at 105, and then changed to a constant voltage. The current is supplied to the load 107 via the circuit 106.

A voltage detector 10 detects a voltage applied to the load, and a frequency controller 9 determines an 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. 1 is decreased, and the current that can flow through the load 107 is increased.

Conversely, when the load current is small, the oscillation frequency of the oscillator 9 is reduced and the impedance of the capacitor 1 is increased, so that unnecessary current can be cut.

[0039]

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

1. Since the impedance of the capacitor can be reduced by controlling the current flowing through the capacitor by the oscillator, a relatively large load current can flow even with a capacitor having a small capacity.

2. In order to lower the impedance of the capacitor by controlling the current flowing through the capacitor by the oscillator and to divide the voltage by the capacitor to lower the voltage,
A relatively large load current can be passed through a capacitor having a small capacity without generating heat as in the case of using a resistor.

3. The oscillator controls the current flowing through the capacitor to lower the impedance of the capacitor, detects the load voltage, and changes the frequency of the oscillator when the load voltage drops, thereby lowering the impedance of the capacitor. Therefore, a constant load voltage can be supplied even when the load current fluctuates.

[Brief description of the 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 the output of the oscillator.

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 symbols]

 5 resistor 102 commercial power supply 103 rectifier circuit (diode bridge) 106 constant voltage circuit 107 load

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Seiji Yamaguchi 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-2-79769 (JP, A) JP-A-4-258 (JP, A) Jikken 49-71734 (JP, Y1) Jikgyo 4-80289 (JP, Y2) (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 3/07

Claims (3)

(57) [Claims] A rectifier circuit for rectifying a commercial power supply;
Connected in series with the rectifier circuit to reduce the voltage
Connected to the other end of the capacitor via a resistor
A switching element, and the switching element
An oscillator that controls oscillation at a frequency higher than the frequency of the power supply;
Connected to the connection side of the capacitor and resistor via a rectifier
Power supply device having a smoothing circuit and a constant voltage circuit. 2. A rectifier circuit for rectifying a commercial power supply,
Small in series with the rectifier circuit to reduce the voltage
Connect at least two capacitors to the other end of the capacitor.
Connected switching element and this switching element
Oscillation that controls oscillation at a frequency higher than the frequency of the commercial power supply
And a place where there is a connection point between the plurality of capacitors.
A power supply device having a smoothing circuit connected via a rectifier and a constant voltage circuit. 3. An oscillator according to claim 1, wherein an oscillating frequency of the oscillator is varied according to a control result of a frequency control unit that controls the frequency based on a detection result of a voltage detection unit that detects a load voltage.
The power supply as described.