Voltage reduction detection circuit and switching power supply system
AssigneeFunai Electric Co., Ltd.
InventorKazuhiko UDAGAWA
Life of this patent
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Abstract
A voltage reduction detection circuit for a switching power supply includes a first rectifier diode having an anode connected to the output terminal of a secondary winding; a second rectifier diode connected in parallel with the first rectifier diode and having a cathode connected to the output terminal; and resistors arranged to divide the voltage between the cathode side of the first rectifier diode and the anode side of the second rectifier diode. The circuit detects a voltage reduction in an AC power supply (feeding AC power to the switching power supply) based on variation in a voltage resulting from voltage division by the resistors.
Claims11
A voltage reduction detection circuit that detects a voltage reduction in an AC power supply for a switching power supply, the switching power supply converting AC power fed from the AC power supply into DC power, then switching the DC power passing across a primary winding of a switching transformer to generate AC power in a secondary winding of the switching transformer, and then rectifying and smoothing the AC power to output a predetermined DC voltage,
- the voltage reduction detection circuit comprising:
- a first rectifier diode having an anode connected to an output terminal of the secondary winding;
- a second rectifier diode connected in parallel with the first rectifier diode and having a cathode connected to the output terminal;
- and
- resistors arranged to divide a voltage between a cathode side of the first rectifier diode and an anode side of the second rectifier diode,
- wherein the voltage reduction in the AC power supply is detected based on variation in a voltage resulting from voltage division by the resistors.
A switching power supply system comprising:
- an AC power supply;
- a switching power supply converting AC power fed from the AC power supply into DC power, then switching the DC power passing across a primary winding of a switching transformer to generate AC power in a secondary winding of the switching transformer, and then rectifying and smoothing the AC power to output a predetermined DC voltage;
- an on/off portion turning on and off electric power supplied from the AC power supply to the switching power supply;
- a voltage reduction detection circuit detecting a voltage reduction in the AC power supply by use of a positive voltage and a negative voltage generated in the secondary winding;
- a control portion performing control such that the on/off portion switches off when the voltage reduction detection circuit detects that the voltage of the AC power supply has fallen below a predetermined voltage level;
- and
- a control portion power supply driving the control portion.
Dependencies are inferred from the claim text.