Method of operating a switching power converter

• US 6,906,500 B2
• Filed: 11/14/2002
• Issued: 06/14/2005
• Est. Priority Date: 11/14/2002
• Status: Expired due to Term

• Current Assignee: Exar Corporation (Maxlinear Incorporated)
• Original Assignee: FYRE Storm Incorporated (Maxlinear Incorporated)
• Inventors: Kernahan, Kent
• Primary Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US10/295,448
• Publication Number:
  US 20040095107A1
• Time in Patent Office: 943 Days
• Field of Search: 323/225, 323/271, 323/282, 323/284
• US Class Current: 323/225
• CPC Class Codes: G05F 3/262 using field-effect transistors only
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/008 Plural converter units for generating at two or more independent and non-parallel outputs, e.g. systems with plural point of load switching regulators
• CPC Class Codes: H02M 1/0845 digitally controlled (or with digital control)
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: H03M 5/08 Code representation by pulse width
• CPC Class Codes: H05B 41/2828 using control circuits for the switching elements H05B41/2827 takes precedence
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A method of operating a switching power converter circuit having first and second transistors connected to an inductor, where a conduction control signal is selectively applied to the second transistor as a function of an operation of the first transistor during a conduction cycle. The decision on whether to provide a conduction control signal to the second transistor is made in one mode of operation as a function of the length of the first conduction control signal applied to the first transistor during the conduction cycle. In another mode of operation a comparison is made of the on-to-off conduction transition time of the second transistor to the length of time remaining in a conduction cycle after the first transistor ceases to conduct.

Claims

1. A method of operating a switching power converter circuit including an inductor, a first transistor having a terminal connected to the inductor, a diode having one terminal connected to the common connection between the first transistor and the inductor, a second transistor connected in parallel with the diode, each transistor having a control terminal for receiving a conduction control signal in a conduction cycle having a length, the method comprising:

providing a first conduction control signal to the control terminal of the first transistor during at least a portion of the conduction cycle to cause the first transistor to conduct; and

selectively providing a second conduction control signal to the control terminal of the second transistor as a function of an operation of the first transistor during the conduction cycle.

2. The method of claim 1, wherein the function of an operation of the power converter considered in a decision to selectively provide the second conduction control signal to the second transistor is a length of the first conduction control signal applied to the first transistor during the conduction cycle.

3. The method of claim 2, further comprising providing the second conduction control signal to the control terminal of the second transistor if an on-to-off conduction transition time of the second transistor is less than a length of time remaining in a conduction cycle after a cessation of conduction of the first transistor in the conduction cycle.

4. The method of claim 2, further comprising:

measuring an on-to-off conduction transition time of the second transistor;

storing the measured on-to-off conduction time of the second transistor; and

providing the second conduction control signal to the control terminal of the second transistor if the amount of time remaining in a conduction cycle is greater than the stored on-to-off conduction time of the second transistor.

5. The method of claim 2, further comprising:

storing an on-to-off conduction time of the second transistor; and

providing the second conduction control signal to the control terminal of the second transistor if the amount of time remaining in a conduction cycle after the first transistor ceases conduction is greater than the stored on-to-off conduction time of the second transistor.

6. The method of claim 1, further comprising:

calculating a length of time required for a current in the inductor to cease flowing if the second transistor were not caused to conduct;

comparing an on-to-off conduction transition time of the second transistor with the length of time for the current in the inductor to cease flowing;

causing the second transistor to conduct if the on-to-off transition time of the second transistor is less than a length of time for the conduction of current in the inductor to cease if the second transistor was not caused to conduct.

7. A method of operating a switching power converter circuit including an inductor, a first transistor having a terminal connected to a terminal of the inductor, and a second transistor having a terminal connected to the common connection between the first transistor and the inductor, each transistor having a control terminal for receiving a conduction control signal in a conduction cycle having a length, the method comprising:

providing a first conduction control signal to the control terminal of the first transistor during at least a portion of the conduction cycle to cause the first transistor to conduct; and

selectively providing a second conduction control signal to the control terminal of the second transistor as a function of an operation of the first transistor during the conduction cycle.

8. The method of claim 7, wherein the function of an operation of the power converter considered in a decision to selectively provide the second conduction control signal to the second transistor is a length of the first conduction control signal applied to the first transistor during the conduction cycle.

9. The method of claim 8, further comprising providing the second conduction control signal to the control terminal of the second transistor if an on-to-off conduction transition time of the second transistor is less than a length of time remaining in a conduction cycle after a cessation of conduction of the first transistor in the conduction cycle.

10. The method of claim 8, further comprising:

measuring an on-to-off conduction transition time of the second transistor;

storing the measured on-to-off conduction time of the second transistor; and

providing the second conduction control signal to the control terminal of the second transistor if the amount of time remaining in a conduction cycle is greater than the stored on-to-off conduction time of the second transistor.

11. The method of claim 8, further comprising:

storing an on-to-off conduction time of the second transistor; and

providing the second conduction control signal to the control terminal of the second transistor if the amount of time remaining in a conduction cycle after the first transistor ceases conduction is greater than the stored on-to-off conduction time of the second transistor.

12. The method of claim 7, further comprising:

calculating a length of time required for a current in the inductor to cease flowing if the second transistor were not caused to conduct;

comparing an on-to-off conduction transition time of the second transistor with the length of time for the current in the inductor to cease flowing;

causing the second transistor to conduct if the on-to-off transition time of the second transistor is less than a length of time for the conduction of current in the inductor to cease if the second transistor was not caused to conduct.

13. The method of claim 7, further comprising:

determining a magnitude of a current flowing through the inductor during a conduction of the first transistor during a conduction cycle;

calculating an amount of power that would be consumed if the second transistor were provided the second conduction control signal in a portion of the conduction cycle after the first transistor ceases conduction;

calculating an amount of power that would be consumed if the second transistor were not provided the second conduction control signal; and

comparing the amounts of power that would be consumed for conduction and non-conduction of the second transistor; and

providing the second conduction control signal to the second transistor based on the results of the comparison.