US 4,777,575 A · Switching power supply

Abstract

A switching power supply, in which a series circuit consisting of a primary winding of a transformer and a controllable switch is connected with a DC power source and a secondary winding of the transformer is connected with a first voltage source outputting the voltage developed across the secondary winding during the on-period of the controllable switch and a second voltage source storing the exciting energy of the transformer during the off-period of the controllable switch by using the exciting inductance of the transformer as a current source, a series circuit consisting of the first and the second voltage sources being connected with a load. Owing to this construction, even if voltage-current characteristic of a load having constant voltage characteristic, such as a magnetron, vary due to variations in the temperature, etc., the output voltage is automatically compensated and a stable electric power can be supplied to the load.

Claims29

Dependent claims

A switching power supply for supplying DC output power to a load operable below a predetermined operating temperature comprising:

first rectifier means to be connected with an AC power source, for rectifying a first AC voltage supplied by said AC power source into a DC input voltage;
electric power converting means to be connected with said first rectifier means, for converting said input DC voltage into a desired DC output power, said electric power converting means including a DC-to-AC converting means for converting controllably said DC input voltage into a second AC voltage, transformer means for stepping up said second AC voltage to a third AC voltage, and second rectifier means for rectifying said third AC voltage and producing said AC output power to be supplied to said load;
and
first control means for controlling said DC-to-AC converting means so that said second rectifier means outputs a preset value of DC output power, said first control means including means for detecting a temperature of said load and, only when said detected temperature is higher than a predetermined operating temperature, for controlling the switching means to reduce the present value of DC output power, thereby keeping the load temperature below said predetermined operating temperature.

1 more element

A switching power supply for supplying a constant DC power to a non-linear load comprising:

a transformer having a primary winding to be connected with a DC power source and at least a secondary winding magnetically coupled with said primary winding;
switching means connected in series with said primary winding for controllably connecting during an on-period and disconnecting during an off-period said primary winding repeatedly with and from said DC power source;
a first voltage source connected with said secondary winding, to which electric power produced in said secondary winding during the on-period when said primary winding is connected with said DC power source, is supplied;
a second voltage source connected with said transformer, to which the energy stored in the exciting inductance of said transformer during said on-period is supplied during the off-period, when said primary winding is disconnected from said DC power source;
said first and said second voltage source being connected in series and forming an output circuit for said switching power supply, an output power of said output circuit being supplied to the load;
and
control means for controlling said switching means on the basis of a voltage of said DC power source so that said output power of said output circuit is constant irrespective of a fluctuation in the voltage of said DC power source.

4 more elements

A switching power supply comprising:

a transformer having a primary winding to be connected with a DC power supply and at least a secondary winding magnetically coupled with said primary winding;
switching means connected in series with said primary winding in series controllably connecting during an on-period, and for disconnecting during an off-period said primary winding repeatedly with and from said DC power source;
a capacitor connected in parallel with said switching means;
secondary circuit means connected with said secondary winding, for transforming an AC electric power developed across said secondary winding into an output DC power;
drive means for driving said switching means;
and
control means including means for detecting an artibrary one of a plurality of valley points of an oscillating voltage developed across said switching means during the off-period when said primary winding is disconnected from said DC power source, for controlling said driving means,
said drive means being responsive to said detection means for driving said switching means at a point of time corresponding to the detected valley point.

5 more elements

Dependencies are inferred from the claim text.

Switching power supply

Life of this patent

Switching power supply

Life of this patent

Abstract

Claims29