DC/DC converter

• US 4,685,039 A
• Filed: 06/04/1986
• Issued: 08/04/1987
• Est. Priority Date: 11/15/1983
• Status: Expired due to Term

• Current Assignee: Yokogawa Electric Corporation
• Original Assignee: Yokogawa Hokushin Electric Corp.
• Inventors: Saito, Hitoshi, Inou, Kiyoharu
• Primary Examiner(s): Wong, Peter S.
• Application Number:
  US06/873,091
• Time in Patent Office: 426 Days
• Field of Search: 363/16-17, 363/20-26, 363/55-58, 363/65, 363/68-69, 363/71, 363/131-134, 363/143, 323/267, 323/289
• US Class Current: 363/16
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33569 having several active switching elements H02M3/3353 takes precedence

Abstract

A DC/DC converter which may be used as a power supply of high capacity. The DC/DC converter comprises first and second converters having their primary terminals connected in series so as to insure high output power and high breakdwon voltage; a first diode for forming a closed circuit together with a transformer of the first converter and a capacitor of the second converter when a switching element of the first converter is turned "off"; and a second diode for forming a closed circuit together with a transformer of the second converter and a capacitor of the first converter when a switching element of the second converter is turned "off".

Claims

1. A DC/DC converter comprising

an AC voltage supply means comprising an AC voltage source, a bridge rectifying circuit for rectifying said AC supply voltage and a smoothing capacitor connected across said bridge rectifying circuit;

a first converter and a second converter, each comprising

a transformer comprising a primary coil and a secondary coil,

a switching element connected in series with said primary coil, and

a capacitor connected in parallel with said primary coil and said switching element and also connected to said bridge rectifying circuit, for generating DC voltages;

a first diode connected between one terminal of said primary coil of said transformer of said first converter and a minus terminal of DC input voltage, thereby to form a closed circuit together with said transformer of said first converter and said capacitor of

said converter when said switching element of said first converter is turned OFF;

a second diode connected between one terminal of said primary coil of said transformer of said converter and a plus terminal of DC input voltage, thereby to form a closed circuit together with said transformer of said second converter and said capacitor of said first converter when said switching element of said second converter is turned OFF;

output circuit means for rectifying and smoothing signals generated at respective said secondary coils of said transformers of said first and second converters, thereby to generate DC output voltages, wherein said output circuit means comprises a smoothing capacitor having a pair of terminals, one of said terminals being connected to one side of each of said secondary windings, a first output circuit, and a second output circuit, said first and second output circuits being separate from each other, each of said first and second output circuits comprising a third diode and a fourth diode, each having a negative terminal connected to a terminal of a respective secondary winding and a positive terminal connected to each other to form a node, and a choke coil connected between said node connecting said third and fourth diodes and the other terminal of said smoothing capacitor, such that said DC output voltages are produced at the pair of terminals of said smoothing capacitor with desired current allocation by said first and second converters;

a current transformer connected between a node of a series circuit comprising said first and second converters, and a node of said capacitors of said first and second converters for detecting therethrough total current at the primary side so that said switching elements are driven with suitable phase difference; and

control means connected to said other terminal of said smoothing capacitor of said output circuit means, said switching element of each of said first and second converters, said current transformer, and to said switching elements of said first and second converters for receiving signals from said current transformer and from said output circuit means and for applying signals to said switching elements thereby to control said suitable phase difference.

2. The converter of claim 1 wherein said primary coils of said transformers of said first and second converters, each have intermediate taps;

and wherein one end terminal of each of said switching elements of said first and second converters are connected to said intermediate taps, respectively.

3. The converter of claim 1, wherein said primary coils of said transformers of said first and second converters each have intermediate taps;

and wherein one terminal of said second diode and one terminal of said first diode are connected to said intermediate taps of said first and second converters, respectively.

4. The converter of claim 1, wherein a plurality of said first and second converters are further connected in series with a DC input power source.

5. The converter of claim 1, wherein a plurality of said first and second converters are connected in parallel with a DC input power supply.

6. The converter of claim 1, wherein said first and second converters are ON/ON converters, respectively.

7. The converter of claim 1, wherein said first and second converters are ON/OFF converters, respectively.

8. The converter of claim 1, wherein said switching elements of said first and second converters each comprises a transistor having base, emitter and collector electrodes, a pair of means for driving each respective transistor comprising a resistor, a series circuit comprising a capacitor and a fifth diode connected in parallel with said resistor, and a sixth diode connected between node of said capacitor and said third diode and said collector of said transistor.

9. The converter of claim 1, wherein said phase difference is 180°

.

10. A DC/DC converter comprising

a first converter and a second converter, each comprising

a transformer comprising a primary coil and a secondary coil,

a switching element connected in series with said primary coil, and

a capacitor connected in parallel with said primary coil and said switching element for generating a DC voltage;

a first diode connected between one terminal of said primary coil of said transformer of said first converter and a minus terminal of a DC input voltage, thereby to form a closed circuit together with said transformer of said first converter and said capacitor of said second converter when said switching element of said first converter is turned OFF;

a second diode connected between one terminal of said primary coil of said transformer of said second converter and a plus terminal of a DC input voltage, thereby to form a closed circuit together with said transformer of said second converter and said capacitor of said first converter when said switching element of said second converter is turned OFF; and

a pair of separate output circuit means for rectifying and smoothing signals generated at respective said secondary coils of said transformers of said first and second converters, thereby to generate first and second DC output voltages which are independent of each other;

a current transformer connected between a node of a series circuit comprising said primary coils of said first and second converters and a node of a series circuit comprising said capacitors of said first and second converters, said current transformer detecting therethrough total current at a primary side so that said switching elements of said first and second converters are driven with a phase difference of 180°

;

wherein said switching elements each comprises a transistor having base, emitter and collector electrodes, a pair of means for driving each respective said transistor comprising a resistor, a series circuit comprising a capacitor and a diode connected in parallel with said resistor, and another diode connected between nodes of said capacitor and said diode and said collector of said transistor such that in a steady state current is supplied to said transistor through said resistor with the two diodes being inactive, and in the case of a light load, said another diode operates to provide an overdrive which self balances the load;

an AC voltage supply source having a common line as a reference side;

rectifying circuit means for rectifying said AC supply voltage, comprising a bridge rectifying circuit;

smoothing circuit means comprising a pair of serially connected smoothing capacitors for smoothing output of said rectifying circuit means to generate a DC input voltage;

applying circuit means for applying said DC input voltage to said first and second converters;

a changeover switch connected between the middle point of said two sooothing capacitors and said common line at the reference side of said AC power supply, for conducting a voltage doubled rectification by turning ON said changeover switch and for conducting a bridge rectification by turning OFF said changeover switch; and

control means connected to said current transformer, to each of said pair of output circuit means and to each of said pair of means for driving, for receiving signals associated with output voltages of said first and second converters and signals from said current transformer and responsive thereto for applying signals to each of said means for driving to control the duty ratios of the respective transistors of said first and second converters of that said output voltages are target values, said control means receiving at least one signal corresponding to total current at respective primary coils of said first and second converters and signals corresponding to the respective output currents of said first and second converters and responsive thereto sending signals to effect protection against overcurrents by turning OFF said transsistors when said overcurrent exists.