Current limiting bilateral converter having a ground referenced current sensor

• US 5,233,287 A
• Filed: 05/05/1992
• Issued: 08/03/1993
• Est. Priority Date: 05/05/1992
• Status: Expired due to Fees

• Current Assignee: Space Systems/Loral Incorporated (Loral Space and Communications Incorporated)
• Original Assignee: Space Systems/Loral Incorporated (Loral Space and Communications Incorporated)
• Inventors: Lenk, Ronald J.
• Primary Examiner(s): Voeltz, Emanuel T.
• Application Number:
  US07/878,776
• Time in Patent Office: 455 Days
• Field of Search: 323/222, 323/225, 323/259, 323/268, 323/284, 323/350, 323/351, 323/906, 363/15, 363/16, 363/95, 363/55, 363/56, 363/50, 363/124, 361/18, 361/79, 361/86, 361/87, 361/93, 361/111
• US Class Current: 323/268
• CPC Class Codes: B60L 50/40 using propulsion power supplied by capacitors
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

A bilateral power conversion circuit (30) includes a current sensor that includes a resistance (R_s) coupled in series between a first terminal of a switch (SW2) and a ground potential. The current sensor has an output for providing an over-current signal to an input of a control circuit (24) during a time that the circuit is sinking current from a load and also during a time when the circuit is sourcing current to the load.

Claims

1. A power conversion circuit, comprising:

current source means having an output for coupling to a load;

first switch means having an input coupled to a source of energy and an output coupled to an input of said current source means for periodically providing current to said current source means;

second switch means having an input coupled to a common potential and an output coupled to said current source means for providing current to said current source means during a period of time when said first switch means is not providing current to said current source means; and

current sense means coupled in series between said input of said second switch means and said ground potential, said current sense means having an output for providing a signal that is indicative of a magnitude of the current provided to said current source means.

2. A power conversion circuit as set forth in claim 1 and further including control means for varying a duty cycle of said first switch means, and wherein said output of said current sense means is coupled to an input of said control means for modifying the duty cycle when the magnitude of the current exceeds a predetermined threshold.

3. A power conversion circuit as set forth in claim 1 wherein said current sense means includes a resistance having a first terminal connected to said input of said second switch means and a second terminal connected to said ground potential, and wherein said output of said current sense means is connected to said first terminal

4. A power conversion circuit as set forth in claim 1 wherein said current sense means includes a transformer having a primary winding with a first terminal connected to said input of said second switch means and a second terminal connected to said ground potential, said transformer having a secondary winding having a first terminal coupled to said ground potential and a second terminal coupled to a first terminal of a resistance, said resistance having a second terminal coupled to said ground potential, and wherein said output of said current sense means is connected to said first terminal of said resistance.

5. A power conversion circuit as set forth in claim 2 wherein said current sense means includes a resistance that is coupled to said output of said current sense means, wherein a current flow through said second switch means causes a negative polarity signal at said output of said current sense means, and further including amplifier means having an input coupled to said output of said current sense means and an output coupled to said input of said control means, said amplifier means inverting the negative polarity signal to a positive polarity signal.

6. A bilateral power conversion circuit, comprising:

an inductance having a first terminal for coupling to a load;

first switch means having a first terminal coupled to a source of energy and a second terminal coupled to a second terminal of said inductance;

second switch means having a first terminal coupled to a common potential and a second terminal coupled to said second terminal of said inductance;

control means having an output coupled to said first switch means and to said second switch means for repetitively opening and closing said first and said second switch means in such a manner so as to vary a magnitude or a direction of a flow of current through said inductance, through said first switch means, and through said second switch means for either sinking current from the load or for sourcing current to the load; and

current sense means coupled in series between said first terminal of said second switch means and said ground potential, said current sense means having an output for providing an over-current signal to an input of said control means during a time that the circuit is sinking current from the load and also during a time when the circuit is sourcing current to the load.

7. A bilateral power conversion circuit as set forth in claim 6 wherein said current sense means includes a resistance having a first terminal connected to said input of said second switch means and a second terminal connected to said ground potential, and wherein said output of said current sense means is connected to said first terminal of said resistance.

8. A bilateral power conversion circuit as set forth in claim 6 wherein said current sense means includes a transformer having a primary winding with a first terminal connected to said input of said second switch means and a second terminal connected to said ground potential, said transformer having a secondary winding having a first terminal coupled to said ground potential and a second terminal coupled to a first terminal of a resistance, said resistance having a second terminal coupled to said ground potential, and wherein said output of said current sense means is connected to said first terminal of said resistance.

9. A bilateral power conversion circuit as set forth in claim 6 wherein a first direction of current flow through said second switch means causes a negative polarity signal at said output of said current sense means, and further including first amplifier means having an input coupled to said output of said current sense means and an output coupled to said input of said control means, said first amplifier means inverting the negative polarity signal to a positive polarity signal and coupling the positive polarity signal to said input of said control means, and wherein a second direction of current flow through said second switch means causes a positive polarity signal at said output of said current sense means, and further including second amplifier means having an input coupled to said output of said current sense means and an output coupled to said input of said control means, said second amplifier means coupling the positive polarity signal to said input of said control means.

10. A bilateral power conversion circuit as set forth in claim 6 wherein said load includes a battery.

11. A bilateral power conversion circuit as set forth in claim 10 wherein said control means operates said first switch means and said second switch means, in a first mode of operation, to charge the battery, and wherein said control means operates said first switch means and said second switch means, in a second mode of operation, to discharge the battery.