JPH07184316A - Open phase detecting circuit - Google Patents

Abstract

PURPOSE:To detect open-circuit of input voltage to a DC stabilized power supply receiving AC three-phase voltage. CONSTITUTION:A three-phase DC stabilized power supply comprises a section 21 for detecting the input current, a section 13 for detecting the input current to a DC-DC converter, and a section 14 for deciding the open-phase based on the outputs from the detecting sections 21, 13. Upon open-phase of any one of phase R or S, output voltage from the detecting section 21 increases and the output from a comparator 17, and thereby the output from the detecting section 14, goes H thus notifying an open-phase state. In case of open-phase of phase T, output from a comparator 18 goes H and the output from the detecting section 13 goes L so long as the input current to section 2 has a predetermined level or below and thereby the output from the detecting section 14 goes L thus feeding current normally. When the input current to the section 2 exceeds the predetermined level, output from the section 13 goes H and thereby the output from the section 14 goes H thus notifying the open-phase state to the section 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an open phase detection circuit in a stabilized direct current power supply for inputting a three-phase AC voltage.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 3-11925 discloses a power supply detector 5 for detecting whether or not a power failure has occurred in a power supply input to a device based on a state of an input line voltage before AC rectification.
And a determination circuit for detecting the open phase state from the output of the power supply detector 5.

[0003]

This technique can detect abnormalities such as input phase loss and power failure, but does not disclose a technique for stabilizing the power supply. Therefore, there is a drawback that the reliability for stabilizing the power source cannot be improved.

[0004]

SUMMARY OF THE INVENTION The circuit of the present invention comprises a rectifying / smoothing section for converting an alternating current of a three-phase AC power supply into a direct current, and a DC for converting a voltage supplied from the rectifying / smoothing section into a stable voltage.
A DC converter section, a power supply on / off control section for controlling the turning on and off of the DC-DC converter section, and an input current detecting section for monitoring the input current of the three-phase AC power supply,
When the output voltage of the input current detection unit is higher than the reference voltage, it is judged as an open phase, and when the input current is lower than the rated current, it is judged as abnormal and the open phase detection unit for supplying a detection signal to the power-on / off control unit is provided. Including.

[0005]

An embodiment of the present invention will now be described in detail with reference to the drawings.

Referring to FIG. 1, one embodiment of the present invention is
R-phase and S-phase are started on the same core, the same number of turns is applied, the T-phase is turned in the opposite direction, the same number of turns, and the current transformer 25 is wound with cotton for current detection. In order to do so, the rectifying / smoothing unit 1 including the diode 6-11 and the smoothing capacitor 12,
A DC-DC converter unit 2 which receives the output of the rectifying / smoothing unit 1 and outputs a stabilized DC voltage, and between one output of the rectifying / smoothing unit 1 and one corresponding input of the DC-DC converter unit 2. An input current detection circuit 13 arranged to detect an input current to the DC-DC converter unit 2, a resistor 24 for converting another current of the current transformer 25 to detect an input current into a voltage, a rectifying capacitor 23, and a smoothing. An input current detection unit 21 having a contenter 22, comparators 17 and 18 for comparing an output voltage of the input current detection unit 21 with a reference voltage, an output of one of the comparators 18 and an output of the input current detection circuit 13 are provided. An AND circuit 16 that takes a logical product, and an open-phase detector 14 that has an OR circuit 15 that takes a logical sum of the output of the AND circuit 16 and the output of the other comparator 17, and Inputs the output of the phase failure detector 14 includes a power-off control unit 4 for controlling the charged disconnection of the DC-DC converter unit 2.

Next, the operation of one embodiment of the present invention will be described in detail with reference to the drawings.

Referring to FIGS. 1 and 2, in a normal state, the input currents of the R, S, and T phases are as shown in FIG. 2, and the output voltage of the input current detector 21 is lower than the reference voltage of the comparator 17. The output of the comparator 17 is at L level and is higher than the reference voltage 20 of the comparator 18, so the output of the comparator 18 is also L level.
The output of the open-phase detector 14 is at a level indicating a normal state.

When the R phase is open, the voltage across the resistor 22 becomes a pulsed voltage with a large peak as shown in FIG. 2, and the output of the input current detector 21 is higher than in the normal state. The output of the comparator 17 becomes H level, and the open-phase detection section 14 sends the open-phase detection signal to the power-on / off control section 4. The power-on / off control unit 4 issues a disconnection instruction to the DC-DC converter unit or warns that the phase is in the open phase state. The case of the S phase open phase is the same as that of the R phase.

When the T phase is out of phase, the output of the input current detector becomes lower than the reference voltage of the comparator 18 and the output of the comparator 18 becomes H level as shown in FIG. DC-D
When the input current of the C converter is flowing DC-DC
The output of the converter input current detection unit 13 is at H level, and the output of the AND circuit 16 is at H level.
The output of the signal is sent to the power-off / on control unit 4 and the power-on / off control unit 4 instructs the DC-DC converter unit 2 to disconnect or warns that the phase is off. If there is no input current to the DC-D converter, D
The output of the C-DC converter input current detection unit 13 becomes L. At this time, the output of the comparator 18 is H, but the output of the AND circuit 16 is L. Therefore, the output of the open-phase detector is
The L level indicating a normal state is output.

Further, in the above detection method, since the input current is detected and the open phase is detected, if the input current is lower than the rated current, it is not judged as abnormal even in the open phase state. It is possible to increase the sex.

[0012]

The present invention improves the reliability of the rectifying / smoothing section by monitoring the input current of the three-phase power supply and detecting the open phase.
If the input current is below a certain value even if the phase is lost, D
Since the C-DC converter unit is not stopped, there is an effect that the reliability as the DC stabilized power supply device is enhanced.

[Brief description of drawings]

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

FIG. 2 is a diagram showing the operation of one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rectification smoothing part 2 DC-DC converter part 3 load 4 power supply on / off control part 5 undervoltage detection part 6-11 diode 12 smoothing capacitor 13 DC-DC converter input current detection part 14 open phase detection part 15 OR circuit 16 AND Circuits 17 and 18 Comparators 19 and 20 Reference voltage 21 Input current detector 22 Smoothing capacitor 23 Diode 24 Resistor 25 Current transformer

Claims (1)

[Claims] 1. A smoothing rectification unit for converting AC of a three-phase AC power supply into DC, a DC-DC converter unit for converting a voltage supplied from this smoothing rectification unit into a stable voltage, and this DC-DC converter unit.
A power-on / off control unit that controls turning on and off of the DC converter unit, an input current detection unit that monitors an input current of the three-phase AC power supply, and a DC-DC converter that detects an input current of the DC-DC converter unit. An input current detection unit, an input current detection unit, and a phase loss detection unit for inputting the outputs of the DC-DC converter input power supply detection unit to detect a phase loss and output it to the power-on / off control unit. Open-phase detection circuit for DC stabilized power supply.