JPH0389862A - Switching power source - Google Patents

Abstract

PURPOSE:To prevent circuit components from damaging by providing converting means for full-wave rectifying an input voltage when the input voltage is a predetermined value or less and for half-wave rectifying it when it is the predetermined value or larger, and stopping the rectifying operation when it is converted to the full-wave rectification for a voltage of a predetermined value or larger. CONSTITUTION:When a voltage of a predetermined value or less such as AC100V is input from an input power source 7, a switch 18 is closed, and it is full-wave rectified by a rectifying bridge 9 having thyristors 10-13, smoothed by capacitors 15, 16, and supplied to a DC/DC converter 17. When a predetermined value or larger such as AC200V is input, the switch 18 is opened, and it is half-wave rectified by the bridge 9, smoothed by the 15, 16, and supplied to the converter 17. In this case, when the switch 18 remains closed, a Zener diode 22 of a voltage detector 19 is turned ON, a photocoupler 23 is operated, it is input to a thyristor converter 14, and the thyristors 10-13 are turned OFF. Thus, it can prevent circuit components from damaging the to an overvoltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a switching power supply employed as a constant voltage power supply in electronic equipment related to office automation (OA), for example.

(Prior Art) In recent years, for example, with the spread of office automation volume-related electronic equipment, switching power supplies that are small, lightweight, and highly efficient have been adopted as constant voltage power supplies.

Figure 2 shows such a switching power supply.
Code 1 is, for example, AC100V/AC200V/DC
An input power source that inputs different voltages of 280V, 2 is an inrush current blocking resistor that blocks inrush current, 3 is a rectifier bridge circuit consisting of diodes 3a to 3d, and 4 is a rectifier bridge circuit 3 for full-wave or half-wave rectification. Reference numeral 5 indicates an input capacitor, and reference numeral 6 indicates a DC/DC converter.

For example, when ACIO (It) is input from the input power supply l, the changeover switch 4 is closed, and as a result, the AClooV is full-wave rectified by the rectifier bridge circuit 3, smoothed by the input capacitor 5, and then converted to DC/DC.
It is supplied to converter 6.

On the other hand, for example, from input power supply 1 to AC200V or DC2
When 80■ is input, the changeover switch 4 is opened,
As a result, the AC200V or DC280V is half-wave rectified by the rectifier bridge circuit 3, and the input capacitor 5
After being smoothed by the DC/DC converter 6, it is supplied to the DC/DC converter 6.

As a result, AC100V input from input power supply 1/
After passing through the rectifier bridge circuit 3 and the input capacitor 5, each of the voltages ^C200v/DC280V are made into almost the same voltage and supplied to the DC/DC converter 6.

By the way, in such a circuit configuration, if the changeover switch 4 is accidentally closed when AC 200V or DC 280V is input from the input power source 1, the rectifier bridge circuit 3 will close the input capacitor 5 in order to perform full-wave rectification. A voltage twice the normal voltage will be applied to the DC/DC converter 6, and a voltage twice the normal voltage will also be supplied to the DC/DC converter 6.

Therefore, by applying or supplying a voltage twice the normal voltage, the input capacitor 5 and the DC/DC
DC converter 6 will be damaged.

(Problems to be Solved by the Invention) As described above, in the conventional switching power supply described above, if the changeover switch 4 is accidentally closed when, for example, 200V AC or 280V DC is input from the input power supply 1, the rectifier bridge circuit 3 performs full-wave rectification, so twice the normal voltage is supplied to the input capacitor 5 and the DC/DC converter 6, resulting in damage to the input capacitor 5 and DC/DC converter 6. There was a problem.

The present invention was developed in response to these circumstances.
It is an object of the present invention to provide a switching power supply that can prevent damage to each component constituting a circuit due to voltages exceeding the allowable range.

[Configuration of the Invention (Means for Solving the Problems) In order to achieve the above object, the switching power supply of the present invention intermittents different voltages supplied from an input power supply, transforms the intermittent voltages, and then transforms the intermittent voltages. , in a switching power supply that obtains a constant voltage by smoothing, a rectifier for full-wave or half-wave rectification of different voltages supplied from an input power supply; a rectification operation control means for continuing or stopping the rectification operation of the rectification means; A switching means for switching the rectifying operation by the means so that, among different voltages supplied from an input power source, voltages below a predetermined value are subjected to full-wave rectification, and voltages exceeding the predetermined value are subjected to half-wave rectification, and a switching state of the switching means. switching state detection means for detecting the voltage and transmitting a signal prompting the rectification operation control means to stop the rectification operation when the switching means switches the rectification operation to full wave for a voltage exceeding a predetermined value; It is equipped with the following.

(Function) In the switching power supply of the present invention, when the switching means switches the rectification operation of the rectification means to full-wave rectification for a voltage exceeding a predetermined value from the input power supply, the switching state detection means Since a signal is sent to the rectifying operation control means to urge the rectifying operation to stop, and the rectifying operation of the rectifying means is stopped, it is possible to prevent each component constituting the circuit from being damaged by a voltage that exceeds the permissible voltage.

(Example) Hereinafter, details of an example of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing an embodiment of a switching power supply of the present invention.

As shown in the same figure, code 7 AC100V/AC2
An input power supply that inputs different voltages of 00V/DC280V, 8 is an inrush current blocking resistor that blocks inrush current, and 9 is a thyristor 1 that rectifies the input voltage from the input power supply 7.
14 is a thyristor drive circuit that controls the operation of each thyristor IO to 13, 15 and 16 are input capacitors that smooth the voltage rectified by the rectifier bridge circuit 9, and 17 is a DC /
A DC converter, reference numeral 18, is a changeover switch which is switched when the rectification bridge circuit 9 performs full-wave or half-wave rectification operation.The DC converter, reference numeral 19, detects the on/off state of the changeover switch 18, and converts the signal input from the input terminal #t7. voltage (A
(C200V/DC280V) j: On the other hand, when the switching switch 18 is turned on, a signal that prompts the Cyrisk drive circuit 14 to stop the rectification operation (input overvoltage signal)
The voltage detection circuits that send out the voltage are shown in each figure.

Note that one voltage detection circuit includes a dividing resistor 20.degree. 21, a Zener diode 22, a photocoupler 23 for sending out an input overvoltage signal, and a rectifier bridge circuit 24.

A switching power supply having such a configuration operates as follows.

In the following description, it is assumed that the thyristor drive circuit 14 does not send a drive signal to the gates of the thyristors 10 to 13 of the rectifier bridge circuit 9 immediately after the voltage input from the input power source 7 starts.

The stop time of this drive signal depends on the characteristics of the input power source 7, but if there is no need to take into account the distortion of the input terminal waveform with a 50/60Hz commercial power source, the input end source 7 will stop at least once at the maximum waveform. This is a time when the price can be high, for example, 10m5 is required. This is because this delay time is necessary to guarantee the operation of one voltage detection circuit, which will be described later.

First, when AClooV among the different voltages is input from the input power supply 7, the changeover switch 18 is closed, so that AClooV is full-wave rectified by the rectifier bridge circuit 9, smoothed by the input capacitor 15, 16, and then It is supplied to the DC/DC converter 17.

At this time, since the changeover switch 18 is in the on state,
A loop connecting points a and b in the figure is formed, and the voltage between the points a and b, in other words, the closed state of the changeover switch 18 is detected.

Here, the resistance value of the dividing resistor 20.21 and the Zener voltage of the Zener diode 22 are such that when ^ctoov is applied to the AC input terminal side of the rectifier bridge circuit 24, the divided voltage by the dividing resistor 20.21 is are set so as not to exceed the Zener voltage of

On the other hand, from input power supply 7, AC200V or DC280V
When input, the changeover switch 18 is opened, and the AC 200V or DC 280V is thereby half-wave rectified by the rectifier bridge circuit 9, smoothed by the input capacitor 5, and then supplied to the DC/DC converter 6.

At this time, since the changeover switch 18 is in the off state,
Since a loop connecting points a and b in the figure is not formed,
, b, in other words, the open state of the changeover switch 18 is detected.

Then, from the input power supply 7, AC200V or t-1Dc2
When the changeover switch 18 is turned on when 80V is input, a loop connecting points a and b in the figure is formed, and the input voltage from the input power source 7 is transferred to the AC input terminal of the rectifier bridge circuit 24. applied to the side.

Next, since the voltage divided by the dividing resistors 20 and 21 exceeds the Zener voltage of the Zener diode 22, the photocoupler 23 operates, and an input overvoltage signal is output from the photocoupler 23 to the thyristor drive circuit 14.

Upon receiving this input overvoltage signal, the thyristor drive circuit 14 stops sending drive signals to the gates of the thyristors 10 to 13 of the rectifier bridge circuit 9. As a result, each thyristor 10 to 13 is turned off, so the rectification operation by the rectifier bridge circuit 9 is stopped, and the input capacitor 15.
16 and DC/DC converter 17 is prevented from being applied.

In this way, in this embodiment, when the changeover switch is turned on for a voltage exceeding a predetermined value supplied from the input power source, a signal (input overvoltage signal ) to stop the rectification operation of the rectifier bridge circuit, so
Damage to each component constituting the switching power supply can be prevented.

[Effects of the Invention] As explained above, according to the switching power supply of the present invention, it is possible to prevent each component constituting the circuit from being damaged by a voltage higher than the allowable voltage.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the switching power supply of the present invention, and FIG. 2 is a circuit diagram showing a conventional switching power supply. 7...Input power supply, 8...Inrush current blocking resistance, 9゜2
4... Rectifier bridge circuit, 10-13... Thyristor, 14... Thyristor drive circuit, 15.16...
Input capacitor, 17...DC/DC converter,
18... Selector switch, one... Voltage detection circuit,
20゜21...Division resistor, 22...Zener diode, 23...Photocoupler.

Claims (1)

[Claims] (1) In a switching power supply that intermittents different voltages supplied from an input power source, transforms the intermittent voltages, and then smoothes them to obtain a constant voltage, the different voltages supplied from the input power source are converted into full waves or half waves. rectifying means for rectifying waves; rectifying operation control means for continuing or stopping the rectifying operation of the rectifying means; a switching means for switching to wave rectification and half-wave rectification for voltages exceeding a predetermined value; 1. A switching power supply comprising switching state detection means for sending a signal to the rectification operation control means to urge the rectification operation to stop when the rectification operation is switched to a waveform.