JP2595520B2 - AC input power supply - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC input power supply, and more particularly, to an automatic startup AC input power supply.

[Conventional technology]

Conventionally, as a relatively small power supply device for electronic equipment such as computers, it rectifies AC input power and performs DC-DC conversion, and automatically starts and stops DC output immediately when AC input is present. An AC input power supply device referred to as is often used. Generally, in this type of AC input power supply, a rectifier circuit for rectifying the AC input and a DC-DC
A main power supply circuit composed of a DC-DC conversion circuit for conversion,
A drive circuit that drives the output of the DC-DC conversion circuit of the main power supply circuit to be kept constant; a start / stop control circuit that detects the presence or absence of an AC input to start and stop the drive circuit;
The power supply circuit has a control circuit power supply circuit that rectifies the AC input and supplies DC power to the drive circuit and the start / stop control circuit.

With the above configuration, when an AC input is applied, the power supply circuit for the control circuit immediately sends out a DC output, and the start / stop control circuit detects the application of the AC input and causes the drive circuit to start driving. Also, the rectifier circuit of the main power supply circuit
The DC output is transmitted, the drive output from the drive circuit is obtained by the DC-DC conversion circuit, and the output is transmitted. On the other hand, when the application of the AC input is stopped, the power supply circuit for the control circuit maintains the output for a while due to the charged internal capacitor. Give a stop signal. Then the drive output disappeared and DC-D
The C conversion circuit stops its operation, and no output is sent.

[Problems to be solved by the invention]

However, when the AC input power supply of the above-described automatic start-up type stops applying AC input and stopping output,
The start / stop control circuit detects the disconnection of the AC input and gives a drive stop signal to the drive circuit, temporarily stops the drive of the DC-DC conversion circuit, and then the voltage of the power supply circuit for the control circuit drops and starts up -The stop signal given to the drive circuit from the stop control circuit may be restored, the drive circuit may be restarted, and the DC-DC conversion circuit may operate and output. This transmission time is a short time until either the power stored in the rectifier circuit of the main power supply circuit or the power stored in the control circuit power supply circuit disappears, but once the output is cut off, the output is output again. Since it is transmitted, it has a problem that it is greatly affected by the load.

An object of the present invention is to provide a self-starting AC input power supply.
An object of the present invention is to provide an AC input power supply device that does not see re-output as described above when output is stopped due to AC input disconnection.

[Means for solving the problem]

The AC input power supply of the present invention detects the presence or absence of an AC input voltage, and detects a DC-DC power supply of a main power supply circuit including a rectifier circuit and a DC-DC conversion circuit.
Start and stop the drive circuit that drives the DC conversion circuit
In a self-starting AC input power supply that sends and stops DC output, before the rectified output for the internal circuit of this power supply falls below the minimum controllable voltage of this internal control circuit when the AC input voltage drops And a voltage disconnection circuit for disconnecting the power supply to the drive circuit.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention, in which a DC-DC conversion circuit in a main power supply circuit is of a dual-forward type, and an ON drive pulse that makes a transistor of the DC-DC conversion circuit conductive from a driving circuit. And an OFF drive pulse for causing the transistor to be in a nonconductive state sharply when the ON drive pallet falls alternately.

FIG. 1 shows a main power supply circuit 1, a control circuit power supply circuit 2,
It has a start / stop control circuit 3, a drive circuit 4, and a disconnection circuit 5. The main power supply circuit 1 includes a rectifier circuit that rectifies an AC input power supply to generate DC power, and a DC-DC conversion circuit that receives the DC power and outputs a DC output (E ₀ ). The control circuit power supply circuit 2 is a circuit that rectifies the AC input power and supplies a DC output (E ₁ ) to the start / stop circuit 3 and the drive circuit 4. After the AC input is cut off by the power charged in the capacitor. also interim pleasure e.g. 20ms between, are made to be able to maintain the output voltage E _1. The start / stop control circuit 3 has an input power monitor circuit and a delay output circuit connected to the AC input. When the AC input is applied, a start signal is sent to the drive circuit 4 immediately after the application is detected. For disconnection of input, instantaneous interruption tolerance time after detection of disconnection, for example, 10 ms
Is a circuit that stops sending the start signal to the drive circuit 4 after elapse of Drive circuit 4 and variable pulse width oscillator circuit for generating pulses of controlled width from this voltage and the reference voltage by receiving the DC output voltage E _0, reverse phase OFF to ON drive pulse and ON driving pulse from the pulse And a drive circuit for transmitting a drive pulse and a drive circuit for transmitting a drive pulse. The variable pulse width oscillation circuit performs oscillation and oscillation stop according to the presence or absence of a start signal from the start / stop control circuit 3.
The ON drive pulse is sent out via transistors Q ₁ and Q ₂ , and the OFF drive pulse is sent out via transistors Q ₁ , Q ₃ and Q ₄ . The cutting circuit 5 is a power supply circuit 2 for a control circuit.
A circuit provided between the DC output (E ₁ ) of the drive circuit 4 and the collector of the transistor Q ₁ of the drive circuit 4 to cut off conduction when the DC output voltage E ₁ drops below a certain value. ₁ ) Connect the collector to the transistor of drive circuit 4
The transistor Q ₅ of the PNP type which is connected to the collector of Q _1, DC
Connection of a Zener diode ZD connected between the resistor connected to the outside (E ₁ ) and the earth, and two resistors connected in series between the DC output (E ₁ ) and the Zener diode ZD and it has a configuration that connects the base of the point and the transistor Q _5.
A Zener voltage VZ _Z of the Zener diode ZD in this circuit,
The sum of the base-emitter voltage V _BE of the transistor Q ₅ is constant value described above.

FIG. 2 is a time chart at a main point when the AC input is cut off in FIG. 1. Referring to FIG. 2, the operation when the AC input is cut off in FIG. 1 will be described. When the AC input of the AC input power supply device of FIG. 1 during operation is cut off (FIG. 2 (a)), the start / stop control circuit 3 outputs the start signal 10 ms after the instantaneous interruption tolerance time is set. since stopping the delivery, variable pulse oscillating circuit included in the driving circuit 4 is a pulse delivery to the transistor Q ₁ is being stopped immediately stops oscillating. Therefore, transistor Q ₂ is not the output of the ON drive pulse in an open state. On the other hand, at this time, the transistor Q ₃ performing the same operation as the transistor Q ₂
Becomes an open state, the base of the transistor Q ₄ are given the current from the DC output (E ₁₎ sends the OFF drive pulses. Therefore, as shown in FIG. 2 (b), the DC output (E ₀ ) of the main power supply circuit 1 is switched to the instantaneous interruption tolerance time t ₀ after the AC input is cut off.
Through to reduce. However, the DC of the control circuit power supply circuit 2
Output (E _1), begins to fall as shown in the through the 20ms is a self-interruption Strength time t ₁ from the AC input cleavage FIG. 2 (c). Then, the voltage of the DC output (E ₁ ) is controlled by the start / stop control circuit 3
Dividing the minimum operating voltage V _X of, it becomes impossible to control that has been stopped the delivery of the activation signal, and sends the erroneous activation signal when. For this reason, the DC output (E ₁ ) that is not yet low enough
Variable pulse oscillating circuit of the drive circuit 4 is operated by, pulsing the base of the transistor to Q ₁ drive circuit. Therefore, in a conventional circuit, the drive circuit may operate to generate a short-time output as shown by a dotted line in FIG. 2B. However, in the present invention, the disconnecting circuit 5 provided between the collector of the transistor Q ₁ and the DC output (E ₁ )
When the voltage reaches slightly higher constant value than the minimum operating voltage V _X decreases the DC output (E _1), that the drive circuit is operated so that by cutting the current supply to the collector of the transistor Q ₁ Therefore, no erroneous DC output is sent from the main power supply circuit 1.

In the embodiment described above, the DC-DC of the two-stone forward type is connected to the main power supply circuit of the automatic start-up type AC input power supply.
Although the conversion circuit is provided, it is apparent that any circuit having a DC-DC conversion circuit for providing a drive input from the outside is effective. The disconnection circuit is not limited to this embodiment, and any other configuration may be used as long as it disconnects the current when the voltage falls below a certain value.

〔The invention's effect〕

As described above, according to the present invention, in the automatic start-up type AC input power supply device, this voltage divided the minimum operating voltage of the control circuit with the voltage drop of the control circuit power supply circuit when the AC input was cut off. Even if the control circuit sends out an erroneous output at the time, there is an effect that the main power supply circuit does not generate an erroneous output.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
It is a time chart in the main point at the time of AC input disconnection of a figure. 1 ... Main power supply circuit, 2 ... Power supply circuit for control circuit, 3 ...
Start / stop circuit, 4 ... Drive circuit, 5 ... Disconnect circuit.

Claims (1)

(57) [Claims] 1. A rectifier circuit for detecting the presence or absence of an AC input voltage.
An automatic start-up type AC input power supply that starts and stops a drive circuit that drives a DC-DC conversion circuit of a main power supply circuit including a -DC conversion circuit and sends and stops a DC output.
A voltage disconnecting circuit for disconnecting power supply to the drive circuit before the rectified output for the internal control circuit of the power supply device falls below the minimum controllable voltage of the internal control circuit when the AC input voltage drops. Features AC input power supply.