Stepping inductor for fast transient response of switching converter

• US 6,188,209 B1
• Filed: 02/07/2000
• Issued: 02/13/2001
• Est. Priority Date: 02/07/2000
• Status: Expired due to Fees

• Current Assignee: University of Hong Kong (Government of Hong Kong Special Administrative Region)
• Original Assignee: University of Hong Kong (Government of Hong Kong Special Administrative Region)
• Inventors: Pong, Man Hay, Poon, Franki Ngai Kit, Liu, Joe Chui Pong
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US09/499,836
• Time in Patent Office: 372 Days
• Field of Search: 323/255, 323/224, 323/282, 323/284, 323/285, 323/286, 323/287, 323/225
• US Class Current: 323/255
• CPC Class Codes: H02M 1/0019 the disturbance parameters being load current fluctuations
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

A fast transient response power converter is disclosed which makes use of a variable inductor to speed up the converter'"'"'s output voltage response under fast transient conditions. The inductive element in a switching converter is replaced by two series or parallel inductive elements of which one has a smaller inductance value and the other has a larger inductance value. During the fast transient condition, the total inductance is greatly reduced to allow rapid current change during the transient condition.

Claims

1. A power converter comprising:

an input for receiving input power;

an output for providing regulated output power;

a variable inductance device coupled between the input and the output, said variable inductance device having a higher inductance state and a lower inductance state, said variable inductance device being controllable to switch between said higher inductance state and said lower inductance state; and

a control circuit that is operable to sense voltage at the output and is operable to signal said variable inductance device to switch from one of said inductance states to said other inductance state in response to a deviation in the output voltage.

2. The power converter of claim 1 wherein said variable inductance device comprises a fixed inductance component and a variable inductance component, said variable inductance component coupled in series with said fixed inductance component, said variable inductance component comprising a transformer having a plurality of windings.

3. The power converter of claim 2 wherein said transformer has three windings.

4. The power converter of claim 2 wherein a first winding of said transformer is in series with said fixed inductance component.

5. The power converter of claim 4 further comprising an auxiliary power source that is coupled in series with a second winding of said transformer and a first switch.

6. The power converter of claim 5 wherein said auxiliary power source is coupled in series with a third winding of said transformer and a second switch.

7. The power converter of claim 5 wherein said auxiliary power source is coupled to said input power source.

8. The power converter of claim 5 wherein said auxiliary power source is coupled to said output.

35. The power converter of claim 1 wherein said control circuit comprises a first comparator, said first comparator being operable to sense voltage at said output and to signal said variable inductance device to switch from said high inductance state to said low inductance state in response to the sensed output voltage.

36. The power converter of claim 35 wherein said control circuit further comprises a second comparator, said second comparator being operable to sense voltage at said output and to signal said variable inductance device to switch from said low inductance state to said high inductance state in response to the sensed output voltage.

37. The power converter of claim 36 further comprising:

switch means coupled to said variable inductance device, said switch means having a first state and a second state, said switch means being operable to allow input power to reach said variable inductance device when in said first state, said switch means being operable to resist the flow of input power to said variable inductance device when in said second state; and

a pulse width modulation controller coupled to said switch means, said pulse width modulation controller being operable to signal said switch means to transition to said first state or said second state.

38. The power converter of claim 37 further comprising means operable to signal said variable inductance device to switch from said high inductance state to said low inductance state when said switch means is in said first state, said means also being operable to signal said variable inductance device to switch from said low inductance state to said high inductance state when said switch means is in said second state.

9. A power converter comprising:

an input for receiving input power;

an output for providing regulated output power;

a variable inductance device coupled between the input and the output, said variable inductance device having a higher inductance state and a lower inductance state, said variable inductance device being controllable to switch between said higher inductance state and said lower inductance state;

said variable inductance device further comprising;

a lower inductance element;

a switch coupled in series with said lower inductance element thereby forming a switch and lower inductance element series combination; and

a higher inductance element coupled in parallel with said switch and lower inductance element series combination; and

wherein said switch is operable to switch said variable inductance device between said lower inductance state and said higher inductance state and

a control circuit that is operable to sense voltage at the output and is operable to signal said variable inductance device to switch from one of said inductance states to said other inductance state in response to the sensed output voltage.

10. The power converter of claim 9 wherein said control circuit comprises a first comparator, said first comparator being operable to sense voltage at said output and to signal said variable inductance device to switch from said high inductance state to said low inductance state in response to the sensed output voltage.

11. The power converter of claim 10 wherein said control circuit further comprises a second comparator, said second comparator being operable to sense voltage at said output and to signal said variable inductance device to switch from said low inductance state to said high inductance state in response to the sensed output voltage.

12. The power converter of claim 11 further comprising:

a pulse width modulation controller coupled to said switch, said pulse width modulation controller being operable to signal said switch to switch said variable inductance device between said lower inductance state and said higher inductance state.

13. A device comprising:

an input for receiving input power;

an output for providing regulated output power;

an electrical load coupled to said output to receive regulated output power;

a variable inductance device coupled between the input and the output, said variable inductance device having a higher inductance state and a lower inductance state, said variable inductance device being controllable to switch between said higher inductance state and said lower inductance state; and

a control circuit that is operable to sense voltage at the output and is operable to signal said variable inductance device to switch from one of said inductance states to said other inductance state in response to a deviation in the output voltage.

14. The device of claim 13 wherein said variable inductance device comprises a fixed inductance component and a variable inductance component, said variable inductance component coupled in series with said fixed inductance component;

said variable inductance component further comprising a transformer having a plurality of windings.

15. The device of claim 14 wherein said transformer has three windings.

16. The device of claim 14 wherein a first winding of said transformer is in series with said fixed inductance component.

17. The device of claim 16 further comprising an auxiliary power source that is coupled in series with a second winding of said transformer and a first switch.

18. The device of claim 17 wherein said auxiliary power source is coupled in series with a third winding of said transformer and a second switch.

19. The device of claim 17 wherein said auxiliary power source is coupled to said input power source.

20. The device of claim 17 wherein said auxiliary power source is coupled to said output.

21. The device of claim 13 wherein said variable inductance device comprises:

a lower inductance element;

a switch coupled in series with said lower inductance element thereby forming a switch and lower inductance element series combination; and

a higher inductance element coupled in parallel with said switch and lower inductance clement series combination; and

wherein said switch is operable to switch said variable inductance device between said lower inductance state and said higher inductance state.

22. The device of claim 21 wherein said control circuit comprises a first comparator, said first comparator being operable to sense voltage at said output and to signal said variable inductance device to switch from said high inductance state to said low inductance state in response to the sensed output voltage.

23. The device of claim 22 wherein said control circuit further comprises a second comparator, said second comparator being operable to sense voltage at said output and to signal said variable inductance device to switch from said low inductance state to said high inductance state in response to the sensed output voltage.

24. The device of claim 23 further comprising:

a pulse width modulation controller coupled to said switch, said pulse width modulation controller being operable to signal said switch to switch said variable inductance device between said lower inductance state and said higher inductance state.

39. The device of claim 13 wherein said control circuit comprises a first comparator, said first comparator being operable to signal said variable inductance device to switch from said high inductance state to said low inductance state.

40. The device of claim 39 wherein said control circuit further comprises a second comparator, said second comparator being operable to signal said variable inductance device to switch from said low inductance state to said high inductance state.

41. The device of claim 40 further comprising:

switch means coupled to said variable inductance device, said switch means having a first state and a second state, said switch means being operable to allow input power to reach said variable inductance device when in said first state, said switch means being operable to resist the flow of input power to said variable inductance device when in said second state; and

a pulse width modulation controller coupled to said switch means, said pulse width modulation controller being operable to signal said switch means to transition to said first state or said second state.

42. The device of claim 41 further comprising means operable to signal said variable inductance device to switch from said high inductance state to said low inductance state when said switch means is in said first state, said means also being operable to signal said variable inductance device to switch from said low inductance state to said high inductance state when said switch means is in said second state.

25. A switching power converter apparatus comprising:

a first node of the apparatus that provides switching voltage pulses;

a first inductor;

a first transformer having a plurality of windings magnetically coupled with one another, said transformer including a first winding coupled to said first inductor, a second winding, and a third winding;

a voltage source;

a first switch coupled to said second winding and operable to couple voltage from said voltage source to said second winding;

a second switch coupled to said third winding and operable to couple voltage from said voltage source to said third winding;

a first control circuit that is operable to cause said first switch to couple said voltage from said voltage source to said second winding;

a second control circuit that is operable to cause said second switch to couple said voltage from said voltage source to said third winding;

a unit, comprising said first inductor and first transformer, coupled to said first node that provides switching voltage pulses;

an output capacitor coupled to said unit and to a return node of said converter;

output terminals coupled to said output capacitor for connection to a load; and

an overvoltage protection circuit that is operable to guard said first and said second switches against exposure to overvoltages.

26. The apparatus according to claim 25 further comprising means for monitoring converter load voltage at said output terminals;

and wherein

said first control means is operable to cause said first switch to couple said voltage from said voltage source to said second winding when said load voltage falls below a first voltage level, said first control means being operable to cause said first switch to decouple said voltage source from said second winding when said load voltage rises above a second voltage level that is higher than said first voltage level; and

said second control means is operable to cause said second switch to couple said voltage source to said third winding when said load voltage rises above a third voltage level, said second control means being further operable to cause said second switch to decouple said voltage source from said third winding when said load voltage falls below a fourth voltage level that is lower than said third voltage level; and

whereby said third and fourth voltage levels are higher than said first and second voltage levels.

27. A switching power converter apparatus comprising:

a pair of input terminals for connection to a DC voltage source, the first of said terminals being a positive terminal and the second of said terminals being a negative terminal;

a first node of the apparatus that provides switching voltage pulses;

a first inductor;

a first transformer having a plurality of windings magnetically coupled with one another, said windings including a first winding coupled to said first inductor, a second winding, and a third winding;

a first switch coupled to said second winding;

a second switch coupled to said third winding;

a unit, comprising the said first inductor and first transistor, coupled to said first node that provides switching voltage pulses;

an output capacitor coupled to said unit and to a return node of said converter;

a pair of output terminals, the first of said output terminals being a positive terminal and the second of said output terminals being a negative terminal, coupled to said output capacitor for providing a connection point for a load;

a first control circuit that is operable to cause said first switch to couple said second winding to said output capacitor;

a second control circuit that is operable to cause said second switch to couple said third winding to said output capacitor; and

an overvoltage protection circuit that is operable to guard said first and said second switches against exposure to overvoltages.

28. The apparatus according to claim 27 wherein said overvoltage protection circuit comprises:

a first diode with its cathode coupled to said positive input terminal and its anode coupled to a node joining said second winding and said first switch; and

a second diode with its cathode coupled to said positive input terminal and its anode coupled to a node joining said third winding and said second switch.

29. The apparatus according to claim 27 wherein said overvoltage protection circuit comprises:

a first diode with its anode coupled to a node joining said first inductor and said first transformer winding and its cathode coupled to said positive input terminal; and

a second diode with its anode coupled to said negative input terminal and its cathode coupled to said anode of said first diode.

30. The apparatus according to claim 27 further comprising means for monitoring the converter load voltage at said output terminals;

and wherein

said first control circuit is operative to cause said first switch to couple said second winding to said output capacitor when said load voltage falls below a first voltage level, said first control circuit also being operative to cause said first switch to decouple said second winding from said output capacitor when said load voltage rises above a second voltage level that is higher than said first voltage level; and

said second control circuit is operative to cause said second switch to couple said third winding to said output capacitor when said load voltage rises above a third voltage level, said second control circuit being further operative to cause said second switch to decouple said third winding from said output capacitor when said load voltage falls below a fourth voltage level that is lower than said third voltage level; and

whereby said third and fourth voltage levels are higher than said first and second voltage levels.

31. The apparatus according to claim 30 further comprising:

means for switching said first switch to an on-state only if a high pulse voltage is coupled to said first inductor; and

means for switching said second switch to and on-state only if a low pulse voltage is coupled to said first inductor.

32. A switching power converter apparatus comprising:

a pair of input terminals for connection to a DC voltage source, the first of said terminals being a positive terminal and the second of said terminals being a negative terminal;

a first node of the apparatus that provides switching voltage pulses having a high voltage level and a low voltage level;

a first inductor coupled to said first node;

a second inductor coupled to a first series switch thereby forming an inductor series-switch combination, said combination being coupled in parallel with said first inductor;

a first diode with its cathode coupled to said positive input terminal and its anode coupled to a node joining said second inductor and said first series switch;

a second diode with its anode coupled to said negative input terminal and its cathode coupled to a node joining said second inductor and said first series switch;

a control circuit that is operable to cause said first series switch to couple said second inductor in parallel with said first inductor;

an output capacitor coupled to said first inductor and a return node of the converter;

a pair of output terminals coupled to said output capacitor for providing a connection point for a load; and

an overvoltage protection circuit that is operable to guard said first switch against exposure to an overvoltage.

33. The apparatus according to claim 32 further comprising means for monitoring the converter load voltage at said output terminals;

and wherein

said control circuit is operative to cause said first series switch to couple said second inductor in parallel with said first inductor when said load voltage falls below a first voltage level, said control circuit also being operative to cause said first series switch to decouple said second inductor from said first inductor when said load voltage rises above a second voltage level that is higher than said first voltage level, said control circuit being further operative to cause said first series switch to couple said second inductor in parallel with said first inductor when said load voltage rises above a third voltage level, said control means also being operative to cause said first series switch to decouple said second inductor from said first inductor when said load voltage falls below a fourth voltage level that is lower than said third voltage level; and

whereby said third and fourth voltage levels are higher than said first and second voltage levels.

34. The apparatus according to claim 33 further comprising:

means for switching said first series switch to an on-state only if a high pulse voltage is coupled to said first inductor; and

means for switching said first series switch to an off-state only if a low pulse voltage is coupled to said first inductor.