JPS60134768A - Voltage doubler rectifier circuit - Google Patents

Abstract

PURPOSE:To protect a smoothing capacitor for a defect of a rectifying diode by connecting diodes in parallel in a direction for conducting smoothing electrolytic condensers in positive and negative half-wave rectifiers at reverse voltage applying time. CONSTITUTION:Protecting diodes 7, 8 are connected in parallel in a direction for conducting when a reverse voltage is applied to electrolytic condensers 4, 5 of positive and negative half-wave rectifiers. When rectifying diodes 2, 3 are normal, they do not affect any influence to the circuit operation, but if any of the diodes 2, 3 is shortcircuited, the voltage applied to the condensers 4, 5 is suppressed to approx. 0.4V by the diodes 7. 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a voltage doubler rectifier circuit, and more particularly to a voltage doubler rectifier circuit equipped with a reverse voltage prevention diode for protecting a capacitor.

[Technical Background] FIG. 1 shows the configuration of a conventional voltage doubler rectifier circuit to which the present invention is directed. In the figure, 1 is an AC power supply, 2 and 3 are rectifying diodes, 4 and 5 are smoothing electrolytic capacitors,
6 is a load resistance. - Here, the diode 2 and the electrolytic capacitor 4 constitute a positive half-wave rectifier circuit, and the diode 3 and the electrolytic capacitor 5 constitute a negative half-wave rectifier circuit.

FIG. 2 shows the operating waveforms of the circuit shown in FIG.
in is the AC input voltage +VC (is the voltage waveform generated by diode 2 across capacitor 4 for a positive half cycle of Vin, ■C2I is the voltage waveform generated by diode 2, which is half-wave rectified by diode 3 for half-wave rectification of Vin for a negative half cycle) The voltage waveform generated across the electrolytic capacitor 50, and Vout, is a composite waveform of ■C1 and ■c2 appearing across the load resistor 60.In addition, the positive and negative half cycles of Vin are caused by terminal A being connected to terminal B, respectively. It refers to the period when the value is positive or negative.

Now, let us consider a case in which a fault occurs in one of the diodes 2 or 3 in the circuit shown in FIG. 1, resulting in a short circuit or an open state. FIG. 3 shows a case where the diode 2 is in a short-circuited state, and FIG. 4 shows a case where the diode 3 is in an open state.

In the case of a short circuit failure of diode 2 shown in Fig. 3,
The AC input voltage Vin is applied directly to both ends of the electrolytic capacitor 40. Because electrolytic capacitors have extremely low reverse impedance due to their structure, a large reverse current flows during the negative half cycle, causing them to be destroyed in a short period of time.

On the other hand, in the case of an open circuit failure of the diode 3 shown in FIG. flows. The magnitude of the reverse current in this case depends on the value of the load resistor 6, but the electrolytic capacitor 5 deteriorates to a greater or lesser degree and is eventually destroyed if the reverse current is large.

In this way, in voltage doubler rectifier circuits, if one of the rectifier diodes is short-circuited or open-circuited, the problem will spread to the smoothing capacitor, greatly increasing the effort and cost required for recovery. there were.

[Object and structure of the invention]

The purpose of the present invention is to protect a smoothing capacitor from failure of a rectifier diode in a 9-fold voltage rectifier circuit, and as a construction for this purpose.

A positive half-wave rectifier circuit and a negative half-wave rectifier circuit, each consisting of a rectifier diode and a smoothing electrolytic capacitor, are connected in parallel to an AC power supply, and the circuit is connected across the output terminals of both the positive and negative half-wave rectifier circuits. In the voltage doubler rectifier circuit to which a load is connected, diodes are connected in parallel to each smoothing electrolytic capacitor in the positive and negative half-wave rectifier circuits in a direction that conducts when a reverse voltage is applied. .

[Embodiments of the invention]

The details of the present invention will be explained below based on two examples.

Fig. 5 shows an embodiment of a voltage doubler rectifier circuit according to the present invention. 7 and 8 indicate protection diodes.

The protective diodes 7 and 8 are connected in parallel in such a direction that they become conductive when a reverse voltage is applied to the electrolytic capacitors 4 and 5, respectively. Therefore, if the rectifying diodes 2 and 3 are normal, they will not affect the operation of the nine circuits in any way.

“If either rectifier diode 2 or 3 is short-circuited, the reverse voltage applied to the smoothing electrolytic capacitor connected to the short-circuited diode will be approximately equal to 0.4V
Reverse current is suppressed to a certain degree.

Most of it can be released into the protective diode.

Therefore, the protective fuse or circuit breaker normally provided in the power supply circuit can be activated by excessive current due to a fault and protect the electrolytic capacitor from being destroyed until the power supply input is disconnected.

FIG. 6 shows a case where the rectifying diode 3 becomes open due to a fault, and corresponds to the conventional example shown in FIG. 4. In this case, from the electrolytic capacitor 4 side to the load resistor 6
The load current flowing into the electrolytic capacitor 5 through , that is, the reverse current ■r toward the electrolytic capacitor 5 is bypassed by the protective diode 8 . Therefore, the amount of reverse current flowing through the electrolytic capacitor 5 is significantly suppressed, and its deterioration or destruction can be prevented.

〔Effect of the invention〕

As described above, the present invention can protect smoothing electrolytic capacitors from faults in rectifier diodes in voltage doubler rectifier circuits by simple means, reducing maintenance costs and shortening the time required for recovery. can be made possible.

[Brief explanation of the drawings] Figure 1 is a circuit diagram of a conventional voltage doubler rectifier circuit, Figure 2 is its operating waveform diagram, and Figure 3 is an explanation of the operation when one of the rectifier diodes is short-circuited. figure. Fig. 4 is an explanatory diagram of the operation when one of the rectifying diodes is open, Fig. 5 is a circuit diagram of one embodiment of the present invention, and Fig. 6 is a diagram explaining the operation when one of the rectifying diodes is open in this embodiment. It is an explanatory diagram of operation I when it becomes an open state. In the figure, 1 is an AC power supply, 2 and 3 are rectifying diodes, and 4 and 5 are smoothing electrolytic capacitors. 6 is a load resistance, and 7 and 8 are protection diodes. Patent Applicant: Fujitsu Limited, Representative Patent Attorney (Long Axis) Written by (1 other person) Figure 2

Claims (1)

[Claims] A positive half-wave rectifier circuit and a negative half-wave rectifier circuit, each consisting of a rectifier diode and a smoothing electrolytic capacitor, are connected in parallel to an AC power supply, and the circuit is connected across the output terminals of both the positive and negative half-wave rectifier circuits. A voltage doubler rectifier circuit to which a load is connected, characterized in that diodes are connected in parallel to each smoothing electrolytic capacitor in the positive and negative half-wave rectifier circuits in a direction that conducts when a reverse voltage is applied. circuit.