JPH0479769A - Double-voltage smoothing circuit - Google Patents

Abstract

PURPOSE:To facilitate a highly reliable double-voltage smoothing circuit having a reduced size structure by a method wherein rush current suppressing resistors which are connected to avalanche diodes in series and suppress currents applied to the avalanche diodes are provided. CONSTITUTION:Current suppressing resistors 6 are connected in series to two avalanche diodes 5 respectively. When a voltage outputted from a rectifying diode 2 exceeds a predetermined voltage and the avalanche diodes 5 start avalanche operation, currents applied to the avalanche diodes 5 are suppressed by the current suppressing resistors 6. Therefore, large current capacity avalanche diodes are not necessary. From the viewpoint of design, the values of the current suppressing resistors 6 are so determined as to have rush currents at the time of the start of the avalanche operation within a range of the rated current capacity of the avalanche diodes 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a voltage doubler smoothing circuit that rectifies and smoothes an alternating current voltage and outputs the same, and particularly relates to avalanche diode protection means that protects a smoothing capacitor from overvoltage.

[Prior Art] FIG. 2 shows the configuration of a voltage doubler smoothing circuit according to a conventional example.

The circuit shown in this figure includes a rectifier diode (2) that takes in AC voltage from an AC power supply (1), rectifies it, and outputs it, and a smoothing capacitor (4) that smoothes the voltage output from the rectifier diode (2). , is equipped with.

That is, the AC voltage output from the AC power supply (1) is
It is rectified by a rectifier diode (2) and further smoothed by a smoothing capacitor (4).

Furthermore, in this conventional example, two smoothing capacitors (4) are directly connected, and the connection part of this series connection is connected to the AC power supply (1) connection end of the rectifier diode (2) via a switch (3). connected. Switch (3) is called a voltage doubler switch. When this switch (3) is turned off, a full-wave rectified voltage is output from the rectifier diode (2), and when it is turned on, a doubled voltage is output.

For example, if the AC voltage output from the AC power supply (1) is 10
In the case of 0V, the voltage doubler switch (3) is turned on, and in the case of AC voltage or 200V, the voltage doubler switch (3) is turned off, either manually or automatically by a switching circuit.

Furthermore, in this conventional example, two smoothing capacitors (
An avalanche diode (5) is connected in parallel with 4).

This avalanche diode (5) starts a so-called avalanche operation when the applied voltage exceeds a predetermined voltage. That is, when the voltage of the smoothing capacitor (4) exceeds a predetermined voltage, the avalanche diode (5) becomes short-circuited.

Therefore, if a fuse is provided that blows out due to the reverse flow of the avalanche diode (5), it is possible to
) or overvoltage.

Therefore, if there is an error in the switching operation of the voltage doubler switch (3) or if the voltage doubler switch (3) is set to automatic switching, voltage breakdown of the smoothing capacitor (4) that may occur due to malfunction of the switching circuit that performs this automatic switching is prevented. Ru.

[Problems to be Solved by the Invention] However, in the conventional voltage doubler smoothing circuit, it is necessary to use an avalanche diode with a large rated current capacity.

That is, when the avalanche diode starts avalanche operation, if the current flowing into the avalanche diode with the start of this avalanche operation is large,
Self-heating occurs in the avalanche diode.

If this self-heating is large, the avalanche diode will be destroyed.

In order to prevent such destruction, it is necessary to increase the current capacity of the avalanche diode, and for this reason, it is necessary to use an avalanche diode with a large current capacity and therefore a large size.

The present invention has been made with the aim of solving these problems, and the current capacity of the avalanche diode can be small. The purpose is to provide a voltage doubler smoothing circuit.

[Means for Solving the Problems] In order to achieve such an object, the present invention is characterized by having an inrush current suppressing resistor connected in series to the avalanche diode and suppressing current flowing into the avalanche diode. do.

[Function] In the voltage doubler smoothing circuit of the present invention, when the anno-lanche diode starts an avalanche operation, the current flowing into the avalanche diode with the start of this avalanche operation is suppressed by the rush current suppression resistor. . As a result, destruction of the avalanche diode due to self-heating is prevented, and it becomes possible to use a small avalanche diode with a small current capacity.

[Examples] Hereinafter, preferred embodiments of the present invention will be described based on the drawings. Note that the same components as those of the conventional example shown in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 1 shows the configuration of a voltage doubler smoothing circuit according to an embodiment of the present invention.

The circuit shown in this figure has a configuration in which two current suppressing resistors (6) are added to the circuit shown in FIG. 2.

That is, a current suppression resistor (6) is connected in series to each of the two avalanche diodes (5). In this embodiment, when the voltage output from the rectifier diode (2) exceeds a predetermined voltage and the avalanche diode (5) starts an avalanche operation, the current flowing through the avalanche diode (5) or the current suppressing resistor ( 6)
suppressed by

Therefore, there is no need to use a large current capacity avalanche diode (5). In terms of design, the resistance value of the current suppression resistor (6) may be determined so that the inflow current (inrush current) at the start of the avalanche operation is within the rated current capacity of the avalanche diode (5).

Further, in this embodiment, the current suppressing resistor (6) is inserted on the quad side of the avalanche diode (5), or it may be provided on the anode side. Even with this configuration, similar effects can be obtained.

Further, in this embodiment, a linear resistance element is used as the current suppression resistor (6), but instead of this, a current suppression element having nonlinear resistance such as a thermistor may be used. Even in this case, the effect of suppressing the current flowing into the avalanche diode (5) can be similarly obtained.

The inventor of the present invention has conducted experiments on the effect of protecting the avalanche diode (5) by suppressing this inflow current. In this experiment, the AC voltage output from the AC power supply (1) was
The voltage was 70V, and an avalanche diode (5) with the worst variation was used.

As a result of this experiment, the avalanche diode (5) was not destroyed.Therefore, the result of this experiment indicates that the avalanche diode (5) is sufficiently protected by the current suppression resistor (6). Inru.

[Effects of the Invention] As explained above, according to the present invention, since the current flowing into the avalanche diode is suppressed by the current suppression resistor, it is possible to use a relatively small current capacity as the avalanche diode. It becomes possible. As a result, the avalanche diode is prevented from being destroyed by the inflow current, and a voltage doubler smoothing circuit that is inexpensive, compact, and highly reliable can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the structure of a voltage doubler smoothing circuit according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing the structure of a voltage doubler smoothing circuit according to a conventional example. In the figure, (1) is an AC power supply, (2) is a rectifier diode, (4) is a smoothing capacitor, (5) is an avalanche diode, and (6) is a current suppression resistor. Note that in the drawings, the same reference numerals indicate the same or equivalent configurations. Agent: Patent Attorney Yoshi 1) Kenji (2 others) Part ~ Densei TCP System Cool J Run 'tit Final Circuit I Anatomy Diagram 2 Procedural Amendment (Spontaneous) 5. Subject of Amendment 1991 Columns for the title of the invention, scope of claims, detailed description of the invention, and brief description of the drawings in the February 22nd specification.

Claims (1)

[Claims] A means for taking in AC voltage, rectifying it and outputting it, a smoothing capacitor for smoothing the rectified voltage, and a means connected in parallel to the smoothing capacitor, and shorting both ends of the smoothing capacitor when the applied voltage exceeds a predetermined voltage. A voltage doubler smoothing circuit comprising: an avalanche diode that protects a smoothing capacitor from overvoltage;