Switching power supply
First Claim
1. A switching power supply receiving a voltage from a DC power supply and generating an isolated DC voltage for a load, the switching power supply having a power saving mode initiated by a received power saving signal, the switching power supply comprising:
- a transformer including a primary winding, a secondary winding and a tertiary winding;
a semiconductor switch connected to the DC power supply through said primary winding;
a control circuit for controlling said semiconductor switch;
a rectifier circuit, said rectifier circuit being operatively coupled to said secondary winding, whereby the isolated DC voltage is generated;
a voltage regulator circuit, said voltage regulator circuit being operatively coupled to said rectifier circuit and selectively reducing the isolated DC voltage in response to a received power saving signal;
a power supply circuit, said power supply circuit being responsive to a voltage output of said tertiary winding and providing a voltage output to said control circuit; and
a voltage detector circuit, said voltage detector circuit being responsive to said power supply circuit and providing an output signal when the voltage output is less than a predetermined value, said control circuit receiving said voltage detector circuit output signal and reducing the operating frequency of said semiconductor switch in response thereto, whereby a power saving mode of operation is provided in response to the received power saving signal.
3 Assignments
0 Petitions
Accused Products
Abstract
A switching power supply for outputting an isolated DC voltage includes a transformer TR1 having a secondary winding N21 and a tertiary winding N3; a semiconductor switch Q1; a DC voltage source (capacitor) C1 connected to the transformer TR1 and the semiconductor switch Q1; a rectifier D1 connected to the secondary winding N21; a power IC, the power supply voltage for which is obtained by rectifying the output of the tertiary winding N3 of the transformer TR1; and a comparator IC5 for detecting the voltage of the control power supply that is lower than a predetermined value, by which to shift to the power saving mode of operation. The above configuration eliminates the photo-coupler for transmitting the power saving signal and reduces the number of terminals of the power IC.
37 Citations
2 Claims
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1. A switching power supply receiving a voltage from a DC power supply and generating an isolated DC voltage for a load, the switching power supply having a power saving mode initiated by a received power saving signal, the switching power supply comprising:
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a transformer including a primary winding, a secondary winding and a tertiary winding; a semiconductor switch connected to the DC power supply through said primary winding; a control circuit for controlling said semiconductor switch; a rectifier circuit, said rectifier circuit being operatively coupled to said secondary winding, whereby the isolated DC voltage is generated; a voltage regulator circuit, said voltage regulator circuit being operatively coupled to said rectifier circuit and selectively reducing the isolated DC voltage in response to a received power saving signal; a power supply circuit, said power supply circuit being responsive to a voltage output of said tertiary winding and providing a voltage output to said control circuit; and a voltage detector circuit, said voltage detector circuit being responsive to said power supply circuit and providing an output signal when the voltage output is less than a predetermined value, said control circuit receiving said voltage detector circuit output signal and reducing the operating frequency of said semiconductor switch in response thereto, whereby a power saving mode of operation is provided in response to the received power saving signal.
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2. A switching power supply receiving a voltage from a DC power supply and generating an isolated DC voltage for a load, the switching power supply having a power saving mode initiated by a received power saving signal, the switching power supply comprising:
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a transformer including a primary winding, a secondary winding, a tertiary winding and a quaternary winding; a semiconductor switch connected to said DC power supply through said primary winding; a rectifier circuit, said rectifier circuit being operatively coupled to said secondary winding, whereby the isolated DC voltage is generated; a voltage regulator circuit, said voltage regulator circuit being operatively coupled to said rectifier circuit and selectively reducing the isolated DC voltage in response to a received power saving signal; a control circuit for controlling said semiconductor switch; a first power supply circuit for rectifying the output of said tertiary winding and providing power to said control circuit in an ordinary mode of operation; a second power supply circuit for rectifying the output of said quaternary winding and providing power to said control circuit in a power saving mode of operation; and a voltage detector circuit for monitoring the power fed to said control circuit from said first and second power supply circuits and providing an output signal when voltage is detected at a value lower than a predetermined value, for said control circuit to reduce the operating frequency of said semiconductor switch in response to the output signal from said voltage detector circuit, thereby providing a power saving mode of operation.
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Specification