Power supply control circuit and power source cut-off detection method

Patent metadata

Field	Value
Publication number	US-9537417-B2
Application number	US-201313765149-A
Country	US
Kind code	B2
Filing date	Feb 12, 2013
Priority date	Sep 10, 2010
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

A power supply control circuit arranged to prevent a steady power loss from occurring in an input filter connected to an alternating current power source. In order to detect that an AC input has been turned off, diodes are connected to AC lines, thus detecting a full-wave rectified waveform. This detected voltage is compared with a reference voltage by a comparator. An output signal of the comparator is input into the reset terminal of a timer circuit having a time measurement period longer than the power source frequency of an alternating current power source. A switch element of a discharging circuit is turned on by an output signal of the timer circuit.

First claim

What is claimed is:

1. A power supply control circuit connected to an alternating current power source via an input circuit having a capacitor, comprising:
a discharging circuit which discharges accumulated electric charge remaining in the capacitor when the alternating current power source is cut off;
a peak hold circuit which detects a voltage signal increasing and decreasing in accordance with an increase and decrease in a terminal voltage of the capacitor, and, during each cycle of a plurality of cycles of the alternating current power source, holds a peak voltage representing a peak voltage of the alternating current power source and discharges the held peak voltage in response to a reset signal;
a level comparison component which generates the reset signal by comparing the voltage signal with a reference voltage signal level supplied to the level comparison component based on the peak voltage representing the peak voltage of the alternating current power source held by the peak hold circuit; and
a timer circuit, connected to the level comparison component, whose timing operation is reset by the reset signal, the timer circuit configured to cause the discharging circuit to discharge the accumulated electric charge when the timer circuit detects that the timing operation has elapsed a predetermined time measurement period without being reset.

2. The power supply control circuit according to claim 1 , further comprising:
a level down circuit which generates the reference voltage signal level based on the peak voltage representing the peak voltage of the alternating current power source held by the peak hold circuit, the level down circuit provided between the peak hold circuit and level comparison component.

3. The power supply control circuit according to claim 1 , wherein the predetermined time measurement period is longer than the cycle duration of the alternating current power source.

4. The power supply control circuit according to claim 3 , wherein the discharging circuit includes a switch element which discharges the accumulated electric charge by both ends of the capacitor being connected to a ground potential.

5. The power supply control circuit according to claim 4 , wherein the timer circuit causes the switch element to conduct by outputting a pulse signal output from the timer circuit after the timing operation has elapsed the time measurement period without being reset.

6. The power supply control circuit according to claim 5 , wherein a delay circuit is provided between the timer circuit and the switch element.

7. The power supply control circuit according to claim 3 , wherein the discharging circuit discharges the accumulated electric charge by both ends of the capacitor being connected to the power source terminal of the power supply control circuit.

8. The power supply control circuit according to claim 1 , wherein the level comparison component includes a pair of diodes whose anodes are connected to either end of the capacitor and whose cathodes are connected to each other, a resistance circuit connected between the cathodes of the pair of diodes and the ground potential, and a comparator which compares a voltage divided by the resistance circuit with a reference signal voltage.

9. The power supply control circuit according to claim 1 , wherein the input circuit is a noise removal filter for removing noise emitted to the alternating current power source.

10. A power source cut-off detection method which discharges accumulated electric charge remaining in a capacitor configuring an input circuit connected to an alternating current power source, comprising:
detecting a voltage signal increasing and decreasing in accordance with an increase and decrease in a terminal voltage of the capacitor;
during each cycle of a plurality of cycles of the alternating current power source, carrying out a holding operation of holding a peak voltage representing a peak voltage of the voltage signal;
generating a reference voltage signal level from the peak voltage representing the peak voltage of the alternating current power source held by the holding operation;
generating a reset signal by comparing the voltage signal with the reference voltage signal level, the reset signal causing the holding operation to reset;
setting a predetermined time measurement period longer than the cycle duration of the alternating current power source, thus carrying out a timing operation that is reset by the reset signal; and
discharging the accumulated electric charge when the timing operation detects that the predetermined time measurement period has elapsed without the timing operation being reset.

11. The power supply control circuit according to claim 2 , wherein the level down circuit generates the reference voltage signal level using a voltage divider, included in the level down circuit, configured such that the voltage signal becomes lower than the reference a voltage signal level during each cycle of the plurality of cycles of the alternating current power source.

Assignees

• Fuji Electric Co Ltd

Inventors

• Shiroyama Hironobu
• Sugawara Takato

Classifications

• H02M7/02 Primary

  Conversion of AC power input into DC power output without possibility of reversal · CPC title

• G01R31/40 Primary

  Testing power supplies (testing photovoltaic devices H02S50/10) · CPC title

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title

• H02M7/217

  using semiconductor devices only · CPC title

• H02M2001/322

  Electricity · mapped topic