JPH03230761A - rectifier - Google Patents

Abstract

PURPOSE:To do enough current limitation so as to decrease loss by connecting the middle point of a line, which is connected in series with an AC input terminal where a thermistor is inserted, through a second switch, and making this second switch after making of a first switch. CONSTITUTION:At the point of time when a power switch 5 is made, the switch IC 3 is off, and it becomes a full-wave rectifying circuit. Accordingly, rush currents are limited with a power thermistor 1b in the case where AC input voltage is positive phase, and with a power thermistor 1a in case of reverse phase so as to prevent rush currents. But when a switch IC 3 becomes ON after lapse of necessary delay time and it becomes a voltage multiplying rectifier, the stationary currents flowing at this time do not flow to the power thermistors 1a and 1b, so temperature rise during stationary operation does not occur, and it maintains approximately initial resistance value at all times. Hereby, the rush current limiting capacity by remaking the power switch during stationary operation can be maintained high.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rectifying device for a DC output power supply that can be used over a wide range of AC input voltages.

Conventional technology In recent years, the number of 200 volt devices has increased in the consumer electronics field, and inexpensive and compact AC input voltages of 100 to 200 volts/L have increased.
/) There is a growing demand for a universal power supply that can be used throughout the area. In order to achieve this, the input voltage range is wide, so the inrush current when the power is turned on may be large, so a power thermistor is generally used as an element to limit the inrush current that occurs when the power switch is turned on. .

As shown in Figure 3, a rectifier diode 2 which is a rectifier
2L, 2b, and 20.2d are bridge-connected so that full-wave rectification can be performed, and a power thermistor 16.3f is inserted into each of the input lines from both terminals of the AC power source 60 on the AC input side. A power switch 5 is arranged in the AC input circuit.

A smoothing capacitor 4 is installed at both ends of the full-wave rectified output of the bridge connection.
N, 4b are connected in series. The series connection point of the smoothing capacitors 4a and 4b is connected to one of the input terminals on the mu C side of the bridge connection via a switch IC3 composed of an IC.

Next, the related operations of each of these components will be explained.

Figure 4 shows the relationship between the resistance value and temperature of a power thermistor, where each diagonal straight line represents the characteristics of one thermistor, and the numbers on the straight lines are the numbers of the thermistors with each characteristic. .

As shown in the resistance-temperature characteristic curve in FIG. 4, it has a high resistance value at low temperatures and limits the rush current generated when the power switch 5 is turned on to 1'1ilI. However, when the power supply operates and the power thermistors 1 el and 1 f reach the commercial temperature, their resistance becomes even lower, and the current is no longer restricted so much.

However, when the power switch 5 is turned on again, the resistance values of the power thermistors 1e and 1f are small due to the high temperature caused by heat generation, so the flow limiting ability of the power thermistors 2b decreases.

In order to prevent this, if power thermistors 1e and 1f are selected, which have a large residual resistance at the temperature they reach, the power consumption of power thermistor 115.1f will increase and the temperature will rise extremely. In the conventional example, the power thermistor is divided into two, and each thermistor 11
This is an attempt to reduce the power consumption of 5°1f as much as possible and reduce the temperature rise. Here, switch I
C3 detects the AC input voltage after the power switch 5 is turned on, and is used to switch between full-wave rectification and voltage doubler rectification.

On the other hand, in another conventional example shown in FIG. 2, the power thermistors 1c and 1d are replaced by rectifier diodes 2a and 2b.

2c, placed after 2d, power thermistor 1C1
This method attempts to further reduce the power consumption of 1d and further reduce the temperature rise. In other words, the power consumption of the power thermistors 1c and 1d is reduced when the input voltage is low because the current consumption of the power supply is larger when the AC input pressure is low than when the AC input voltage is high. That is, in the case of steady operation at a low AC input voltage, the switch IC3 for switching the rectification method performs ONL voltage double rectification, so the steady current path when the AC input voltage is in positive phase is the power switch 6. Rectifier guioto 2 & power thermistor 10. Smoothing capacitor 48, Nu Inochi IC3,
When the AC input voltage is in reverse phase, the current path is the AC power source 6. Switch IC3, smoothing capacitor 4b, Huff thermistor 1a, rectifier diode 2C,
Power switch 5 becomes power thermistor IC, 1d
The only mixed current passing through is the schoolmates, and their temperature rise will be very small. L, 6 = L, but when the power switch 5 is turned on, it will turn on again. Brown I C3 is not ON yet, so full wave adjustment 1 soil In this method, two power thermistors 10 and 1d are inserted in series in the current path, and if the resistance of the power thermistors 1c and 1d is checked at low temperatures, the current limit at low temperatures is very good. τ1: There is a risk that it will be difficult to start the power source.

In addition, the rectification method when using a weak AC input voltage is also full-wave V:P[
In other words, two power thermistor ICs, 1d, are inserted in series in the steady current path, so the third ';;'
：”J) Even when compared to ℃, the temperature rise of the power thermistors 1c and 1d has not been improved at all.

Problems to be Solved by the Invention As mentioned above, in the conventional rectifier,
If a high-resistance thermistor with sufficient current limiting function is inserted when the power switch 5 is turned on, the loss of the thermistor during steady operation will be large. Since the temperature is high, there is a problem that sufficient current limiting function is lost.

There is also a method of dividing the thermistor to reduce the heat generated by one thermistor as much as possible, but this method is insufficient.

The present invention has been made with the above-mentioned problems in mind, and an object of the present invention is to provide a rectifier device that sufficiently limits the current when the power switch is turned on and has low loss during steady state.

Means for Solving the Problems In order to achieve the above object of the present invention, the present invention bridge-connects a plurality of rectifying elements so that full-wave rectification is performed, and the AC input circuit includes a first power input circuit. A switch is inserted, multiple smoothing capacitors for DC output smoothing are connected in series in the bridge-connected DC high-power circuit, and a thermistor is connected to each of the rectifying elements connected to either one of the bridge-connected AC input terminals. are inserted in series, and the intermediate point connected in series with the AC input terminal into which this thermistor is inserted is connected via a second switch.
The rectifier is configured such that the switch is turned on after the first switch is turned on.

Furthermore, the second switch is configured to be a rectifier that opens and closes depending on the AC input voltage and automatically switches the rectification method.

Function The rectifier of the present invention having the above configuration operates as a full-wave rectifier circuit when the first switch, which is a power switch, is turned on, and rectifies each half-wave of the positive phase and negative phase through the thermistor. Current flows and is smoothed by a smoothing capacitor to obtain a DC voltage. When the power switch is turned on, the thermistor does not generate much heat, so it functions as a sufficient current limiting resistor. Next, when the second switch is controlled and turned on with a delay, a voltage doubler current circuit is formed, and rectified current flows without passing through the thermistor for each half wave of the positive phase and negative phase, rectifying with no loss due to the thermistor. A DC voltage is obtained by smoothing the current with a smoothing capacitor.

However, in order to use this rectifier circuit for both low voltage input and high voltage input as the muC input voltage, it is necessary to provide an input voltage detection function and a means for opening and closing the second switch according to the detected voltage. When inputting a low voltage, the second switch is turned on as described above to configure it as a voltage doubler rectifier circuit, and when inputting a high voltage, the second switch is shut off to configure it as a full-wave rectifier circuit, and the output voltage is I try to keep them almost the same value. In this case, the low voltage input is the same as above, but in the case of high voltage input, a rectified current will flow through the thermistor, but a half-wave period of rectified current will flow through one thermistor. , and because of the high voltage input, the current is lower than that of low voltage input, and the thermistor loss and heat generation are extremely small. Therefore, the current limiting function is sufficiently maintained when the first switch is turned on again.

Embodiment FIG. 1 shows a rectifier circuit to which an inrush current limiting method is added according to a first embodiment of the present invention. As shown in FIG. 1, the power thermistor 1+L, 1b is a rectifier diode 2a,
2b and 20.2d, and a switch IC3 composed of an IC for automatically switching the rectification method is connected to the connection point of the smoothing capacitors 4a and 4b and the AC input terminal. 5 is a power switch, and 6 is a muC power supply.

Next, the mutually related operations of these components will be explained.

First, when the AC input voltage is low, this rectifier operates as a voltage doubler circuit, so it is necessary to turn on the SWIN $I C3, but it takes a long time after turning on the power switch 6 until the SUINOSENKO C3 turns on. Due to the delay time,
At the time when the power switch 5 is turned on, the switch 103 is OFF and becomes a full-wave rectifier circuit. Therefore, when the AC input voltage is in positive phase, the inrush current is
．． Rectifier diode 2a, smoothing capacitor 4J4b, rectifier f
It flows through the path of fi diode 2d, power thermistor 1b, and AC power source 6, and in the case of reverse phase, it flows through AC power source 6. Power thermistor 1N, rectifier diode 2b, smoothing capacitors 4a, 4b, rectifier "Io" 2C, power switch 6 because it flows through the path of power thermistor 1
a or power thermistor 1b to prevent inrush current. However, when the switch IC3 turns on after the required delay time and becomes a voltage doubler rectifier circuit, the steady current that flows at this time flows through the power switch 5I, the rectifier diode 2a, the smoothing capacitor 41. The current flows through the path of the switch IC 3 and the AC power source 6, and if the AC input voltage is in reverse phase, the AC power source 6. switch IC3,
Smoothing capacitor 4b.

The current flows through the rectifier diode 2C and the power switch 6. In other words, the steady current is the power thermistor 1 aL, 1
Since the current does not flow through b, there is no temperature rise during steady operation, and the resistance value is always maintained at almost the initial value, so that the ability to limit the inrush current by turning the power switch on again during steady operation is maintained at a high level.

Next, if the input voltage is high 50, switch the power switch 5
It becomes a full-wave rectifier circuit both when turned on and during steady operation, and the path through which the inrush current and steady current flow is the same as the path through which the inrush current flows in the case of the low AC input voltage. Therefore, in case of high AC input voltage, the temperature of the power thermistor increases because the steady state current also flows through the power thermistor 1a and then the power thermistor 1b. However, since the steady-state current is lower than in the case of a low MuC input terminal, the temperature rise is reduced, a power thermistor with high residual resistance can be used, and the ability to limit the inrush current when the power is turned on again can be improved. can.

Effects of the Invention As is clear from the above explanation, the present invention has a simple configuration that makes it possible to realize a rectifier that is inexpensive and has a high inrush current limiting ability, and also provides a highly efficient rectifier that can handle a wide range of input voltages. realizable.

[Brief Description of the Drawings] Fig. 1 is a circuit diagram of a rectifier according to an embodiment of the present invention, Figs. 2 and 3 are circuit diagrams of a conventional rectifier, and Fig. 4 is a circuit diagram of the rectifier according to an embodiment of the present invention. It is a characteristic diagram showing characteristics. 1a, 1b... Power thermistor, 2L, 2b. 20.2d... Rectifier diode, 3... Switch IC, 41L, 4b... Smoothing capacitor,
5...Power switch, 6...MuC power supply.

Claims (2)

[Claims] (1) A plurality of rectifying elements bridge-connected to perform full-wave rectification, a first switch disposed in the bridge-connected AC input circuit, and connected in series to the bridge-connected DC output circuit. a plurality of smoothing capacitors, a thermistor connected in series to each of the plurality of rectifying elements connected to one side of the AC input circuit among the plurality of rectifiers, and a side of the AC input circuit to which the thermistor is connected; A rectifying device comprising a second switch disposed between a midpoint of smoothing capacitors connected in series, and having means for turning on the second switch after the first switch is turned on. (2) After turning on the first switch, the AC input voltage is detected, and if the voltage is low, the second switch is turned on, and if the voltage is high, the second switch is opened. The rectifying device described.