Voltage regulator with clamping circuit

• US 6,507,174 B1
• Filed: 09/06/2001
• Issued: 01/14/2003
• Est. Priority Date: 09/06/2001
• Status: Expired due to Fees

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Qian, Jinrong
• Primary Examiner(s): Sherry, Michael
• Assistant Examiner(s): Laxton, Gary L.
• Application Number:
  US09/948,804
• Time in Patent Office: 495 Days
• Field of Search: 323/222-225, 323/268, 323/271, 323/282, 323/311, 323/351, 363/55, 363/56.01, 363/56.09, 363/56.12
• US Class Current: 323/222
• CPC Class Codes: H02M 1/0064 Magnetic structures combining different functions, e.g. storage, filtering or transformation
• CPC Class Codes: H02M 1/34 Snubber circuits
• CPC Class Codes: H02M 1/342 Active non-dissipative snubbers
• CPC Class Codes: H02M 3/155 using semiconductor devices only
• 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 circuit for clamping a voltage across a switching element to a value equal to or less than the sum of the input voltage plus the voltage across a clamping capacitor is provided. The circuit achieves voltage clamping accordance with one embodiment in which an active clamp circuit includes a switch and a clamping capacitor connected in parallel with a first winding of a coupled winding. The active clamp prevents the occurrence of voltage spikes across the switch. The clamping capacitor recovers energy stored in the first winding of the coupled winding. The circuit achieves voltage clamping in accordance with a second embodiment in which a passive clamp circuit includes a switch a clamping capacitor,and first and second diodes. The passive clamp circuit prevents the occurrence of voltage spikes across the switch. The clamping capacitor recovers energy stored in the first winding of the coupled winding.

Claims

1. A converter circuit, comprising:

a base circuit including

a first switching element connected to a first junction,

a first winding coupled to the first junction and connected to a second junction,

a second winding magnetically coupled to said first winding and connected to the second junction, and

a switch-diode circuit connected to said second winding; and

a clamp circuit for clamping voltage across said first switching element at a predetermined level, said clamp circuit including

a second switching element connected to the second junction, and

a clamping capacitor connected to said second switching element and the first junction, wherein said clamping capacitor is adapted to recover leakage energy from said first winding.

2. The converter circuit of claim 1, wherein the switch-diode circuit includes a third switching element connected to said second winding.

3. The converter circuit of claim 2, wherein the switch-diode circuit includes a diode connected in parallel with said third switching element.

4. The converter circuit of claim 1, wherein said bas e circuit further includes a filter capacitor coupled in parallel to a load.

5. The converter circuit of claim 1, wherein said converter circuit is a DC-DC converter circuit.

6. A method for clamping a voltage across a switching element in a converter circuit, said method comprising:

providing a base circuit including

a first switching element connected to a first junction,

a first winding coupled to the first junction and connected to a second junction,

a second winding magnetically coupled to said first winding and connected to the second junction, and

a switch-diode circuit connected to said second winding; and

providing a clamp circuit for clamping a voltage across said first switching element at a predetermined level, said clamp circuit including

a second switching element connected to the second junction, and

a clamping capacitor connected to said second switching element and the first junction, wherein said clamping capacitor is adapted to recover leakage energy from said first winding.

7. The method of claim 6, wherein said clamping step is performed at a time when said first switching element transitions from an ON state to an OFF state.

8. The method of claim 6, wherein said clamping capacitor recovers energy during an OFF state of said first switching element.

9. The method of claim 6, further comprising the step of recovering leakage from a leakage inductor associated with said first winding in each switching cycle.

10. The method of claim 6, wherein the leakage energy in said inductor is recovered by charging the clamping capacitor through said second diode and said third switching element.

11. A converter circuit, comprising:

a base circuit including

a first switching element connected to a first junction,

a first winding coupled to the first junction and connected to a second junction,

a second winding magnetically coupled to said first winding and connected to the second junction; and

a clamp circuit for clamping a voltage across said first switching element at a predetermined level, said clamp circuit including

a clamping capacitor connected to the first junction and a third junction, wherein said clamping capacitor is adapted to recover leakage energy from said first winding,

a first diode connected to the second junction and the third junction,

a third winding magnetically coupled to said first winding and said second winding, and connected to the third junction, and

a second diode connected to said third winding.

12. The converter circuit of claim 11, wherein said converter circuit further includes a filter capacitor coupled in parallel to a load.

13. The converter circuit of claim 11, wherein said converter circuit is a DC-DC converter circuit.

14. A method for clamping a voltage across a switching element in a converter circuit, said method comprising:

providing a base circuit including

a first switching element connected to a first junction,

a first winding coupled to the first junction and connected to a second junction,

a second winding magnetically coupled to said first winding and connected to the second junction; and

a clamp circuit for clamping a voltage across said first switching element at a predetermined level, said clamp circuit including

a clamping capacitor connected to the first junction and a third junction, wherein said clamping capacitor is adapted to recover leakage energy from said first winding,

a first diode connected to the second junction and the third junction,

a third winding magnetically coupled to said first winding and said second winding, and connected to the third junction, and

a second diode connected to said third winding.

15. The method of claim 14, wherein the clamping is performed at a time when said switching element transitions from an ON state to an OFF state.

16. The method of claim 14, wherein said clamping capacitor recovers energy during an OFF state of said first switching element.

17. The method of claimi 14, further comprising the step of recovering leakage from an inductor associated with said first winding in each switching cycle.

18. The method of claim 17, where in the leakage energy in said inductor is recovered by charging the clamping capacitor through said first diode and said third winding.