Extended range boost converter circuit

• US 6,191,957 B1
• Filed: 01/31/2000
• Issued: 02/20/2001
• Est. Priority Date: 01/31/2000
• Status: Expired due to Term

• Current Assignee: BAE Systems Controls Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems Controls Incorporated (BAE Systems Plc)
• Inventors: Peterson, William Anders
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US09/494,641
• Time in Patent Office: 386 Days
• Field of Search: 363/17, 363/37, 363/40, 363/57, 363/60, 363/95, 363/98, 363/131, 363/132
• US Class Current: 363/17
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 3/33573 Full-bridge at primary side of an isolation transformer

Abstract

A power converter comprises a power transformer having a primary winding and a secondary winding flux coupled to the primary winding, input terminals for receiving an input voltage, and output terminals for providing an output voltage. A power switching arrangement comprising two pairs of switching devices arranged in a bridge configuration has a corresponding duty cycle which is selectable so as to cause the power converter to manifest different input output transfer characteristics corresponding to buck and boost modes of operation. An inductor having a single winding is coupled between the input terminals and the primary winding through the switching devices. Secondary winding rectification and filtering provides the power supply output. A reset circuit coupled to the output terminal of the single winding inductor and connected to the input terminals provides a current path for discharging the inductor during a predetermined time interval corresponding to that portion of the duty cycle when all of the switching devices are off to enable operation of the power supply in a buck mode of operation.

Claims

1. A power converter comprising:

a power transformer having a primary winding and a secondary winding of a given turns ratio;

input means for receiving an input voltage;

output means for providing an output voltage;

an inductor coupled between the input means and the primary winding of said transformer;

first and second power switching means coupled between said inductor and said transformer and operative in an on and off state according to a given duty cycle for controllably causing a flow of current from the primary winding;

unidirectional conduction means coupled to the transformer secondary winding for rectifying flux-coupled energy to provide an output voltage Vo to the output means;

means for controlling said duty cycle of said first and second power switching means to maintain the output voltage Vo at a preselected level; and

means coupled to an output terminal of the inductor for providing a current path for discharging the inductor during a predetermined time interval according to the duty cycle of said power switching means.

2. The apparatus according to claim 1, wherein said inductor is a single winding inductor.

3. The apparatus according to claim 1, wherein said controlling means receives a feedback sample of said output voltage Vo for controlling the duty cycle of said switching means to selectively operate in a buck portion or a boost portion of an input-to-output transfer characteristic to regulate the output voltage at the pre-selected level.

4. The converter according to claim 1, wherein said discharge means comprises a capacitor serially coupled to a first unidirectional conduction device for storing energy associated with said inductor.

5. The converter according to claim 4, wherein said discharge means further comprises a switching device connected in parallel with said capacitor and connected to a second inductor and a second unidirectional conduction device to enable discharge of said capacitor through said second inductor when said switching device is enabled, and to enable discharge of said second inductor through said second unidirectional conduction device to said input means when said switching device is disabled.

6. The apparatus according to claim 5, wherein said switching device is operated at a second duty cycle corresponding to the duty cycle associated with said first and second switching means.

7. The apparatus according to claim 4, wherein said unidirectional current device is a diode having a first terminal coupled to an output terminal of said inductor and a second terminal coupled to a first terminal of said capacitor, and wherein said capacitor has a second terminal coupled to an input terminal of said inductor.

8. The apparatus according to claim 1, wherein said predetermined time interval corresponds to a buck portion of the duty cycle wherein said first and second switching means are non-conducting.

9. The converter according to claim 1, wherein said first and second switching means are semiconductor switching devices.

10. A power converter comprising:

a power transformer having a primary winding and a secondary winding flux coupled to the primary winding;

input means for receiving an input voltage;

output means for providing an output voltage;

a single winding inductor coupled between the input means and the primary winding;

a switching arrangement comprising a plurality of switches which are switched on and off according to a duty cycle for controllably causing a flow of current from the primary winding;

means for controlling the duty cycle of said switching arrangement;

unidirectional conduction means coupled to the transformer secondary winding for rectifying flux coupled energy to provide an output voltage Vo to the output means; and

means coupled to an output terminal of the inductor for providing a current path for discharging the inductor during a predetermined time interval associated with a portion of the duty cycle of the switching arrangement when said plurality of switches are off to enable the power converter to operate in a mode where the output voltage Vo is lower than the input voltage.

11. The converter according to claim 10, wherein said discharge means comprises:

a first unidirectional conduction device having a first end coupled to an output terminal of the inductor;

a capacitor having a first terminal coupled to a second end of the first unidirectional conduction device, and a second terminal coupled to an input terminal of the inductor; and

a switching circuit connected in parallel with said capacitor and selectively enabled during the predetermined time interval associated with the portion of the duty cycle of the switching arrangement when said plurality of switches are off to enable discharge of energy stored in the capacitor.

12. The converter according to claim 11, wherein the switching circuit comprises a controllable switch coupled to a second inductor and to a second unidirectional conduction device such that enabling the switch enables a communication path between the second inductor and the capacitor to discharge the capacitor, and disabling the switch enables a communication path between the second inductor and the second unidirectional conduction device for energy discharge to the input means.

13. The converter according to claim 10, wherein the plurality of switches of the switching arrangement are arranged in a bridge configuration.

14. A buck-boost converter comprising:

a power transformer having a primary winding and a secondary winding of a given turns ratio;

input terminals for receiving an input voltage;

output terminals for providing an output voltage;

a single winding inductor coupled between the input terminals and the primary winding;

a switching arrangement comprising a plurality of switches to be turned on and off according to a duty cycle for controllably causing a flow of current through the primary winding;

a controller for controlling the duty cycle of said switching arrangement;

unidirectional conduction means coupled to the transformer secondary winding for rectifying flux coupled energy to provide an output voltage Vo to the output means;

means coupled to an output terminal of the inductor and operable in a first mode for providing a path for discharging the inductor during a predetermined time interval associated with a portion of the duty cycle of the switching arrangement when said plurality of switches are each off to enable the boost converter to operate in a first mode where the voltage Vo is lower than the input voltage, and operable in a second mode for providing a path for discharging energy associated with leakage inductance reflected to the output terminal of said single winding inductor when the boost converter is operated in a second mode wherein said plurality of switches are each on during a same portion of said duty cycle.

15. The converter according to claim 14, wherein said controller means is responsive to said output voltage to adjust the duty cycle of said switching arrangement to enable operation in said first or second modes.

16. The converter according to claim 15, wherein said means coupled to the output terminal of said inductor comprises a reset circuit including a switch to be turned on and off according to a second duty cycle to selectively discharge energy through said path of said reset circuit.

17. The converter according to claim 16, wherein said controller means operates to control said second duty cycle at a rate proportional to said duty cycle of said switching arrangement.

18. In a boost converter comprising a power transformer having a primary winding and a secondary winding flux-coupled to the primary winding, input terminals for receiving an input voltage;

output terminals for providing an output voltage;

a switching arrangement coupled to said transformer comprising a plurality of switches to be turned on and off according to a duty cycle for controllably causing a flow of current through the primary winding of said transformer such that the output voltage is greater than the input voltage;

means for controlling the duty cycle of said switching arrangement;

unidirectional conduction means coupled to the transformer secondary winding for rectifying flux coupled energy to provide the output voltage Vo to the output means, the improvement comprising;

a single winding inductor coupled between the input means and the primary winding; and

an operating circuit coupled to an output terminal of the inductor for providing a path for discharging energy associated with leakage inductance reflected to the output terminal of the inductor through the switch arrangement back to the input means, whereby the energy is recovered and recycled through the boost converter.

19. The converter according to claim 18, wherein the operating circuit includes a capacitor for storing and discharging energy associated with said leakage inductance;

and

a switch responsive to a signal from said control means for enabling said capacitor to discharge according to a given duty cycle.

20. The converter according to claim 18, wherein said operating circuit further includes:

a first diode having a first end coupled to an output terminal of said inductor and a second end coupled to a first terminal of said capacitor, said capacitor having a second terminal coupled to an input terminal of said inductor; and

a second inductor having a first end coupled to said inductor first terminal and a second end coupled to said switch and to a second diode.