Switching power supply

• US 4,933,830 A
• Filed: 04/27/1989
• Issued: 06/12/1990
• Est. Priority Date: 04/28/1988
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Amano, Hisao, Sato, Masayoshi, Tokunaga, Norikazu, Matsuda, Yasuo
• Primary Examiner(s): Salce, Patrick R.
• Assistant Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US07/343,748
• Time in Patent Office: 411 Days
• Field of Search: 363/20, 363/21, 363/131, 219/10.55 B, 336/184
• US Class Current: 363/131
• CPC Class Codes: H01F 30/10 Single-phase transformers H01F30/16 takes precedence
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters
• CPC Class Codes: H05B 2206/043 Methods or circuits intended to extend the life of the magnetron
• CPC Class Codes: H05B 6/662 Aspects related to the boost transformer of the microwave heating apparatus
• CPC Class Codes: H05B 6/666 Safety circuits emergency protective circuits in general H02H

Abstract

A switching power supply using a step-up transformer whose impedance viewed from its primary side is different from the impedance viewed from its secondary side whereby the inductance of its primary and secondary windings are settable independently of each other.

Claims

1. A switching power supply comprising:

a D.C. power source;

a step-up transformer having a primary winding and a secondary winding, the primary winding being supplied with electric power from the D.C. power source, the secondary winding being connected to a load, an inductance value of the transformer viewed from the primary side being different from a converted secondary inductance value of the transformer, the converted secondary inductance value being obtained by converting an inductance value of the transformer viewed from the secondary side into an inductance value on the primary side;

a switching element connected in series with the primary winding for repeating an ON-OFF operation in accordance with a control signal;

a capacitor connected in parallel with at least one of the switching element, the primary winding and the secondary winding, for forming an oscillation circuit in cooperation with one of the primary and secondary windings; and

a control device for periodically generating an ON-pulse which makes the switching element conductive for a predetermined period, to supply a series of ON-pulses to the switching element, the ON-pulse being applied as the control signal to the switching element.

2. A switching power supply comprising:

a D.C. power source;

a step-up transformer having a primary winding and a secondary winding, the primary winding being supplied with electric power from the D.C. power source, the secondary winding being connected to a load, and inductance value of the transformer viewed from the primary side being different from a product of a² and an inductance value of the transformer viewed from the secondary side, where a indicates a turn ratio;

a switching element connected in series with the primary winding for repeating an ON-OFF operation in accordance with a control signal;

a capacitor connected in parallel to at least one of the switching element, the primary winding and the secondary winding, for forming an oscillation circuit in cooperation with one of the primary and secondary windings; and

a control device for periodically generating an ON-pulse which makes the switching element conductive for a predetermined period, to supply a series of ON-pulses to the switching element, the ON-pulses being applied as the control signal to the switching element.

3. A switching power supply for driving a magnetron, comprising:

a D.C. power source;

a step-up transformer having an iron core, a primary winding and a secondary winding, the primary winding being supplied with electric power from the D.C. power source, the secondary winding being connected to the magnetron the iron core having two legs, the secondary winding being wound around each of two legs, the primary winding being wound around only one of two legs;

a switching element connected in series with the primary winding for repeating an ON-OFF operation in accordance with a control signal;

a capacitor connected in parallel to at least one of the switching element, the primary winding and the secondary winding, for forming an oscillation circuit in cooperation with one of the primary and secondary windings; and

a control device for periodically generating an ON-pulse which makes the switching element conductive for a predetermined period, to supply a series of ON-pulses to the switching element, the ON-pulses being applied as the control signal to the switching element.

4. A switching power supply comprising:

a D.C. power source;

a step-up transformer having a primary winding and a secondary winding, the primary winding being supplied with electric power from the D.C. power source, the secondary winding being connected to a load, an inductance value of the transformer viewed from the primary side being different from a converted secondary inductance value of the transformer, the converted secondary inductance value being obtained by converting an inductance value of the transformer viewed from the secondary side into an inductance value on the primary side;

a switching element connected in series with the primary winding for repeating an ON-OFF operation in accordance with a control signal;

a capacitor connected in parallel with the switching element for forming an oscillation circuit in cooperation with the primary winding; and

a control device for periodically generating an ON-pulse which makes the switching element conductive for a predetermined period, to supply a series of ON-pulses to the switching element, the ON-pulses being applied as the control signal to the switching element.

5. A switching power supply comprising:

a D.C. power source;

a step-up transformer having a primary winding and a secondary winding, the primary winding being supplied with electric power from the D.C. power source, the secondary winding being connected to a load, one of the primary and secondary windings being divided with first and second portions, the magnetic coupling between the first portion and the other winding being made close, the magnetic coupling between the second portion and the other winding being made loose;

a switching element connected in series with the primary winding for repeating an ON-OFF operation in accordance with a control signal;

a capacitor connected in parallel to the switching element for forming an oscillation circuit in cooperation with the primary winding; and

a control device for periodically generating an ON-pulse which makes the switching element conductive for a predetermined period, to supply a series of ON-pulses to the switching element, the ON-pulses being applied as the control signal to the switching element.

6. A switching power supply for driving a magnetron comprising:

a D.C. power source;

a step-up transformer having a primary winding and a secondary winding, the primary winding being supplied with electric power from the D.C. power source, the secondary winding being connected to the magnetron, an inductance value of the transformer viewed from the primary side being different from a converted secondary inductance value of the transformer, the converted secondary inductance value being obtained by converting an inductance value of the transformer viewed from the secondary side into an inductance value on the primary side;

a switching element connected in series with the primary winding for repeating an ON-OFF operation in accordance with a control signal;

a capacitor connected in parallel to the switching element for forming an oscillation circuit in cooperation with the primary winding; and

a control device for periodically generating an ON-pulse which makes the switching element conductive for a predetermined period, to supply a series of ON-pulses to the switching element, the ON-pulses being applied as the control signal to the switching element.

7. A switching power supply for driving a magnetron, comprising:

a D.C. power source;

a step-up transformer having an iron core, a primary winding and a secondary winding, the primary winding being supplied with electric power from the D.C. power source, the secondary winding being connected to the magnetron, the iron core having two legs, the secondary winding being wound around each of two legs, the primary winding being wound around only one of two legs;

a switching element connected in series with the primary winding for repeating an ON-OFF operation in accordance with a control signal;

a capacitor connected in parallel to the switching element for forming an oscillation circuit in cooperation with the primary winding; and

a control device for periodically generating an ON-pulse which makes the switching element conductive for a predetermined period, to supply a series of ON-pulses to the switching element, the ON-pulses being applied as the control signal to the switching element.

8. A microwave oven range comprising:

rectifier means for obtaining a D.C. voltage by rectifying a commercial A.C. voltage;

a magnetron for supplying microwave power to a microwave heating device;

a step-up transformer having a primary winding and a secondary winding, the primary winding being supplied with electric power from the rectifier means, the secondary winding being connected to the magnetron, an inductance value of the transformer viewed from the primary wide being different from a converted secondary inductance value of the transformer, the converted secondary inductance value being obtained by converting an inductance value of the transformer viewed from the secondary side into an inductance value on the primary side;

a switching element connected in series with the primary winding for repeating an ON-OFF operation in accordance with a control signal;

a capacitor connected in parallel to at least one of the switching element, the primary winding and the secondary winding, for forming an oscillation circuit in cooperation with one of the primary and secondary windings; and

a control device for periodically generating an ON-pulse which makes the switching element conductive for a predetermined period, to supply a series of ON-pulses to the switching element, the ON-pulse being applied as the control signal to the switching element.

9. A high-voltage switching power supply comprising:

a D.C. power source;

a step-up transformer having a primary winding and a pair of secondary windings connected in series to each other, one of the secondary windings being loosely coupled to the primary winding and the other secondary winding being tightly coupled to the primary winding, the primary winding being supplied with electric power from the D.C. power source, the secondary windings being connected to a load, an inductance value of the transformer viewed from the primary side when measured in a state that the secondary side of the transformer is open being different from a converted secondary inductance value of the transformer, the converted secondary inductance value being obtained by converting an inductance value of the transformer viewed from the secondary side when measured in a state that the primary side of the transformer is open into an inductance value on the primary side;

a switching element connected in series with the primary winding for repeating an ON-OFF operation in accordance with a control signal;

a capacitor connected in parallel with at least one of the switching element, the primary winding and the secondary winding, for forming an oscillation circuit in cooperation with one of the primary and secondary windings; and

a control device for periodically generating an ON-pulse which makes the switching element conductive for a predetermined period, to supply a series of ON-pulses to the switching element, the ON-pulses being applied as the control signal to the switching element.

10. A high-voltage switching power supply comprising:

a D.C. power source;

a step-up transformer having a pair of primary windings connected in series to each other and a secondary winding, one of the primary windings being loosely coupled to the secondary winding and the other primary winding being tightly coupled to the secondary winding, the primary winding being supplied with electric power from the D.C. power source, the secondary windings being connected to a load, an inductance value of the transformer viewed from the primary side when measured in a state that the secondary side of the transformer is open being different from a converted secondary inductance of the transformer, the converted secondary inductance value being obtained by converting an inductance value of the transformer viewed from the secondary side when measured in a state that the primary side of the transformer is open, into an inductance value on the primary side;

a switching element connected in series with the primary winding for repeating an ON-OFF operation in accordance with a control signal;

a capacitor connected in parallel with at least one of the switching element, the primary winding and the secondary winding, for forming an oscillation circuit in cooperation with one of the primary and second windings; and

a control device for periodically generating an ON-pulse which makes the switching element conductive for a predetermined period, to supply a series of ON-pulses to the switching element, the ON-pulses being applied as the control signal to the switching element.