Transformer coupled up-down converter

• US 4,422,139 A
• Filed: 03/29/1982
• Issued: 12/20/1983
• Est. Priority Date: 03/29/1982
• Status: Expired due to Term

• Current Assignee: Rockwell International Corporation
• Original Assignee: Rockwell International Corporation
• Inventors: Burkhead, Lowell E.
• Primary Examiner(s): Beha, Jr., William H.
• Application Number:
  US06/362,730
• Time in Patent Office: 631 Days
• Field of Search: 363/20, 363/21, 363/26, 363/97, 363/131
• US Class Current: 363/21.04
• CPC Class Codes: H02M 3/335 using semiconductor devices only

Abstract

A transformer coupled DC-to-DC converter provides a regulated output with only one active switch. The converter includes a switch, a diode and an inductor coupled to the primary of a transformer in a way which provides symmetry to the transformer as the duty cycle of the switch changes for regulation. The circuit may be current-fed by supplying an input voltage higher than the transformer ratio would indicate, or may be voltage-fed by providing an input voltage lower than the transformer ratio would indicate. The circuit is operated to charge an inductor through the switch and half the primary of a transformer and discharge the inductor through the other half of the primary so that equal energy is provided through the transformer during charging and discharging, thereby providing a symmetrical signal without the need for more than one switch.

Claims

1. A power converting apparatus comprising:

input means for receiving DC power;

transformer means coupled to receive power from said input means and provide an output; and

conduction means coupled to said transformer means and said input means for conducting current from said input means and causing a charging current to flow from said input means through a first portion of said transformer means during a first time period to provide said output and for blocking current flow from said input means and causing a discharging current to flow through a second portion of said transformer means during a second time period to provide said output, said conduction means including;

switch means having a first conducting state and a second non-conducting state coupled to said input means for providing said charging current flow when said switch means is in said first conducting state and for blocking said current flow when said switch means is in said second non-conducting state;

inductor means coupled to receive current flow from said switch means and provide said charging current through said first portion of the transformer means during said first time period; and

rectifier means coupled for conducting said discharge current flow from said inductor means through said second portion of said transformer means during said second time period.

2. The apparatus of claim 1 further including control means coupled to said conduction means for controlling said conduction means to alternate said first and second time periods to cause equal current flow during each of said time periods.

3. The apparatus of claim 2 wherein said control means includes means responsive to the output of said transformer means for controlling said conduction means so that said alternate periods produce a regulated voltage at the output of said transformer means.

4. The apparatus of claim 1 further including means coupled to the output of said transformer means for providing a full wave rectified output.

5. The apparatus of claim 1 further including a capacitor coupled to said input means for storing and decoupling the input power and a capacitor coupled to the output of said transformer means for filtering said output.

6. A DC-to-DC converter comprising:

first and second input terminals for receiving power from a DC source;

a switch having first and second terminals controlled by a third terminal to conduct current between said first and second terminals during a first switch state and to interrupt current flow between said first and second terminals during a second switch state, said first switch terminal being coupled to said first input terminal;

a transformer having primary and secondary windings each including first and second end terminals and a center tap terminal;

a rectifier having first and second terminals, said first rectifier terminal being coupled to the first end terminal of said transformer primary and said second rectifier terminal being coupled to said second switch terminal; and

an inductor having first and second terminals, said first inductor terminal being coupled to said transformer primary center tap and said second inductor terminal being coupled to said second switch terminal, said second transformer end terminal being coupled to said second input terminal;

said rectifier being oriented to block current flow through said rectifier during said first switch state to cause a charging current flow through said inductor and a first portion of said transformer primary, and to conduct current from said inductor through a second portion of said transformer primary windings during said second switch state.

7. The apparatus of claim 6 further including rectifier means coupled to said secondary end terminals to provide a full wave rectified output.

8. The apparatus of claim 6 further including means coupled to the control terminal of said switch and responsive to output from said secondary end terminals for alternately causing said switch to change from said first switch state to said second switch state.

9. A DC power supply comprising:

a source of DC power having first and second terminals;

a switch means having first and second terminals and a control terminal for controlling said switch to be alternately conducting and non-conducting to current flow between said first and second terminals, said first switch terminal being coupled to said first DC power terminal;

a transformer means having a primary including first and second end terminals and a center tap terminal and a secondary for providing an output;

a rectifier having first and second terminals, said first rectifier terminal being coupled to said first end terminal and said second rectifier terminal being coupled to said second switch terminal, said second end terminal being coupled to said second DC power terminal; and

an inductor having first and second terminals, said first inductor terminal being coupled to said center tap terminal and said second inductor terminal being coupled to said second switch terminal;

said rectifier being oriented to cause charging current flow from said DC source through said inductor and a portion of the primary of said transformer means during conducting periods of said switch means and causing discharging current flow from said inductor through said rectifier and another portion of the primary of said transformer means during non-conducting periods of said switch means.

10. The apparatus of claim 9 further including means responsive to the output of the secondary of said transformer means and coupled to the control terminal of said switch means for alternately controlling the conducting and nonconducting periods of said switch means to provide a regulated voltage output.

11. The apparatus of claim 9 further including rectifier means coupled to the secondary output for providing a full wave rectified output.

12. A method of providing a regulated output voltage comprising:

providing a variable source of DC input power;

conducting current from said DC source through a switch to cause a charging current flow through an inductor and a first portion of a transformer means during a first time period;

blocking current flow from said DC source through said switch during a second time period to cause a discharge current flow from said inductor through another portion of said transformer means during a second time period;

providing an output from said transformer means during said first and second time periods; and

controlling said switch to conduct and block current flow for variable duty cycles of charging and discharging current flow so that the output of said transformer means is regulated.