Coupled power supply inductors for reduced ripple current

• US 4,703,409 A
• Filed: 10/30/1986
• Issued: 10/27/1987
• Est. Priority Date: 09/26/1983
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Spreen, James H.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/925,032
• Time in Patent Office: 362 Days
• Field of Search: 363/19, 363/20, 363/21, 363/39, 363/45, 363/97
• US Class Current: 363/45
• CPC Class Codes: H02M 1/009 having two or more independently controlled outputs for DC-DC converter with intermediate AC H02M3/33561
• CPC Class Codes: H02M 1/14 Arrangements for reducing ripples from dc input or output
• CPC Class Codes: H02M 3/335 using semiconductor devices only
• CPC Class Codes: H02M 3/33538 of the forward type H02M3/3353, H02M3/33569 take precedence

Abstract

A power supply circuit for producing at least one output which is essentially free from current ripple is disclosed. A chopped DC voltage source is applied to a transformer having a primary coil and at least two secondary coils. The secondary coils provide input voltages to output stages which each include a rectifier diode, a freewheeling diode and an LC filter. The inductors in the LC filter of adjacent output stages are magnetically coupled together. The characteristics of these inductors are selected such that the current ripple through the inductors in all the output stages, other than the first output stage, is essentially zero. Multiple inductors can also be employed in the first output stage with each one being magnetically coupled to the inductor in a different succeeding output stage.

These multiple inductors in the first output stage can be combined in series or in parallel. A chained approach to coupling inductors as well as the use of an add-on ripple transformer can also be employed to product at least one essentially ripple-free output.

Claims

1. A power supply circuit with reduced ripple current for producing a first output and a second output comprising:

a voltage source;

a transformer having a primary input coil, a first secondary output coil for providing a first input voltage and a second secondary output coil for providing a second input voltage, said primary input coil being connected to said voltage source;

a first diode connected to said first secondary output coil for rectifying said first input voltage;

a second diode connected to said second secondary output coil for rectifying said second input voltage;

a first filter means connected to said first secondary output coil and said first diode for filtering said first input voltage, said first filter means including a first inductor; and

a second filter means connected to said second secondary output coil and said second diode for filtering said second input voltage, said second filter means including a second inductor magnetically coupled to said first inductor, the parameters of said inductors being chosen such that the induced open-circuit voltage across said second inductor (when said second inductor is disconnected from the remainder of said second filter means) is approximately identical to the imposed operating voltage on said second inductor when said second inductor is connected to the remainder of said second filter means, said ripple current through said second inductor being much lower than said ripple current through said first inductor.

2. A power supply circuit according to claim 1 wherein said first filter means additionally includes a first freewheeling diode for providing a path for the current through said first inductor when said voltage source is switched off and

said second filter means additionally includes a second freewheeling diode for providing a path for the current through said second inductor when said voltage source is switched off.

5. A power supply circuit according to claim 1 or 3 wherein said voltage source is a chopped DC voltage source.

6. A power supply circuit according to claim 5 wherein said first filter means additionally includes a first freewheeling diode for providing a path for the current through said first inductor when said voltage source is switched off and

said second filter means additionally includes a second freewheeling diode for providing a path for the current through said second inductor when said voltage source is switched off.

3. A power supply circuit for producing a first output and a second output comprising:

a means for reducing current ripple further comprising;

a voltage source;

a transformer having a primary input coil, a first secondary output coil for providing a first input voltage and a second secondary output coil for providing a second input voltage, said primary input coil being connected to said voltage source;

a first diode connected to said first secondary output coil for rectifying said first input voltage;

a second diode connected to said second secondary output coil for rectifying said second input voltage;

a first filter means connected to said first secondary output coil and said first diode for filtering said first input voltage, said first filter means includes a first inductor; and

a second filter means connected to said secondary output coil and said second diode for filtering said second input voltage, said second filter means includes a second inductor magnetically coupled to said first inductor, the parameters of said inductors being chosen such that the induced open-circuit voltage across said second inductor (when said second inductor is disconnected from the remainder of said second filter means) is identical to the imposed operating voltage on said second inductor when said second inductor is connected to the remainder of said second filter means, said ripple current through said second inductor being essentially zero.

4. A power supply circuit according to claim 3 wherein said first filter means additionally includes a first freewheeling diode for providing a path for the current through said first inductor when said voltage source is switched off and

said second filter means additionally includes a second freewheeling diode for providing a path for the current through said second inductor when said voltage source is switched off.

7. A power supply circuit for producing a plurality of outputs comprising:

a voltage source;

a transformer having a primary input coil connected to said voltage source and a plurality of secondary output coils, said plurality of secondary output coils providing a plurality of input voltages;

a plurality of output stages for providing said plurality of outputs, each of said plurality of output stages connected to a different one of said plurality of secondary output coils, one of said plurality of output stages including a plurality of inductors while all the other of said plurality of output stages including only one inductor each, each one of said plurality of inductors being magnetically coupled to a different one of the inductors included in said other of said plurality of output stages, the parameters of said inductors being chosen such that the induced open-circuit voltage across the inductors of said output stages including only one inductor (when the inductors of said output stages including only one inductor are disconnected from the output stages in which they are included) is identical to the imposed operating voltage thereon when the inductors of said output stages including only one inductor are connected to the output stages in which they are included, the ripple current through said inductors included in said other of said plurality of output stages being essentially zero.

8. A power supply circuit according to claim 7 wherein said plurality of inductors are serially connected.

9. A power supply circuit according to claim 8 wherein said voltage source is a chopped DC voltage source.

10. A power supply circuit according to claim 7 wherein said plurality of inductors are connected in parallel.

11. A power supply circuit according to claim 10 wherein said voltage source is a chopped DC voltage source.

12. A power supply circuit according to claim 7, 8 or 10 wherein each of said other of said plurality of output stages additionally includes

a rectifier diode connected to one of said plurality of secondary output coils for rectifying one of said plurality of input voltages and

a freewheeling diode connected to said rectifier diode and one of said plurality of secondary output coils for providing a path for the current through the inductor included in said other of said plurality of output stages when said voltage source is switched off.

13. A power supply circuit according to claim 12 wherein said voltage source is a chopped DC voltage source.

14. A power supply circuit according to claim 7 wherein said voltage source is a chopped DC voltage source.

15. A power supply circuit for producing a plurality of outputs comprising:

a voltage source;

a transformer having a primary input coil connected to said voltage source and a plurality of secondary output coils, said plurality of secondary output coils providing a pluraity of input voltages;

a first output stage connected to one of said plurality of secondary output coils for providing one of said plurality of outputs, said first output stage including a first inductor;

a second output stage connected to a second one of said plurality of secondary output coils for providing a second one of said plurality of outputs, said second output stage including a second inductor and a third inductor, said third inductor being magnetically coupled to said first inductor; and

a third output stage connected to a third one of said plurality of secondary output coils for providing a third one of said plurality of outputs, said third output stage including a fourth inductor, said fourth inductor being magnetically coupled to said second inductor, the parameters of said inductors being chosen such that the induced open-circuit voltage across said third inductor (when said third inductor is disconnected from said second output stage) is greater than the imposed operating voltage on said third inductor when said third inductor is connected to said second output stage, the ripple in the combined current through said second inductor and said third inductor and the ripple in the current through said fourth inductor being essentially zero.

16. A power supply circuit for producing a plurality of outputs comprising:

a voltage source;

a transformer having a primary input coil connected to said voltage source and a plurality of secondary output coils, said plurality of secondary output coils providing a plurality of input voltages;

a first output stage connected to one of said plurality of secondary output coils for providing one of said plurality of outputs, said first output stage including a first inductor;

a plurality of other output stages, each of said plurality of other output stages being connected to a different one of said plurality of secondary output coils and including a pair of inductors, one of said pair of inductors being magnetically coupled to an inductor included in a preceding output stage and the other of said pair of inductors being magnetically coupled to an inductor included in a succeeding output stage, the parameters of said inductors being chosen such that the induced open-circuit voltage across each inductor magnetically coupled to an inductor in a preceding output stage (when each inductor magnetically coupled to an inductor in a preceding output stage is disconnected from its respective output stage) is greater than the imposed operating voltage thereon when each inductor magnetically coupled to an inductor in a preceding output stage is connected to its respective output stage; and

a final output stage connected to one of said plurality of secondary output coils for providing one of said plurality of outputs, said final output stage including a final inductor, said final inductor being magnetically coupled to an inductor included in the preceding output stage, the ripple in the combined current through each of said pair of inductors and the ripple in the current through said final inductor being essentially zero.

17. A power supply circuit for producing at least one output comprising:

a voltage source;

a transformer having a primary input coil connected to said voltage source and at least two secondary output coils for providing at least two input voltages;

a first output stage connected to one of said at least two secondary output coils, said first output stage including a first inductor;

a second output stage connected to another one of said at least two secondary output coils for providing an output, said second output stage including a second inductor; and

an add-on transformer means for reducing current ripple, said add-on transformer means including at least a third inductor and a fourth inductor, said third inductor being magnetically coupled to said fourth inductor and connected in parallel to said first inductor, said fourth inductor being connected in parallel with said second inductor, the parameters of said inductors being chosen such that the induced open-circuit voltage across said fourth inductor (when said fourth inductor is disconnected from said second inductor) is greater than the imposed operating voltage on said fourth inductor when said fourth inductor is connected to said second inductor, the ripple in the combined current thrugh said second inductor and said fourth inductor being essentially zero.

18. A power supply circuit for producing at least one output comprising:

a voltage source;

a transformer having a primary input coil connected to said voltage source and at least two secondary output coils for providing at least two input voltages;

a first output stage connected to one of said at least two secondary output coils, said first output stage including a first inductor; and

a second output stage connected to another one of said at least two secondary output coils for providing said at least one output, said second output stage including a second inductor magnetically coupled to said first inductor, the parameters of said inductors being chosen such that the induced open-circuit voltage across said second inductor (when said second inductor is disconnected from said second output stage) is identical to the imposed operating voltage on said second inductor when said second inductor is connected to said second output stage, the ripple current through said second inductor being essentially zero.

19. A power supply circuit for producing a plurality of outputs comprising:

a voltage source;

a transformer having a primary input coil connected to said voltage source and a plurality of secondary output coils, said plurality of secondary output coils providing a plurality of input voltages; and

a plurality of output stages for providing said plurality of outputs, each of said plurality of output stages connected to a different one of said plurality of secondary output coils, each of said plurality of output stages includes an inductor, each inductor being magnetically coupled to the inductors in the other output stages, the parameters of said inductors being chosen such that the induced open-circuit voltages across each inductor included in said plurality of output stages (when the inductors included in said plurality of output stages are disconnected from the respective output stages) is identical to the imposed operating voltages thereon when the inductors included in said plurality of output stages are connected to their respective output stages; and

another output stage for providing another output, said another output stage connected to another of said secondary output coils, said another output stage also including an inductor magnetically coupled to each of the inductors included in said plurality of output stages, the ripple currents through the inductors included in said plurality of output stages being essentially zero.

20. A power supply circuit for producing a first output and a second output comprising:

a voltage source;

a transformer having a primary input coil, a first secondary output coil for providing a first input voltage and a second secondary output coil for providing a second input voltage, said primary input coil being connected to said voltage source;

a first diode connected to said first secondary output coil for rectifying said first input voltage;

a second diode connected to said second secondary output coil for rectifying said second input voltage;

a first filter means connected to said first secondary output coil and said first diode for filtering said first input voltage, said first filter means includes a first inductor; and

a second filter means connected to said second secondary output coil and said second diode for filtering said second input voltage, said second filter means includes a second inductor and a third inductor, said second inductor being magnetically coupled to said first inductor, the parameters of said inductors being chosen such that the induced open-circuit voltage across said second inductor (when said second inductor is disconnected from the remainder of said second filter means) is greater than the imposed operating voltage on said second inductor when said second inductor is connected to the remainder of said second filter means, the ripple in the combined current through said second inductor and said third inductor being much lower than the ripple in the current through said first inductor.

21. A power supply circuit with reduced ripple current for producing a first output and a second output comprising:

a voltage source;

a transformer having a primary input coil, a first secondary output coil for providing a first input voltage and a second secondary output coil for providing a second input voltage, said primary input coil being connected to said voltage source;

a first diode connected to said first secondary output coil for rectifying said first input voltage;

a second diode connected to said second secondary output coil for rectifying said second input voltage;

a first filter means connected to said first secondary output coil through said first diode for filtering said first input voltage, said first filter means including a first inductor; and

a second filter means connected to said second secondary output coil through said second diode for filtering said second input voltage, said second filter means including a second inductor magnetically coupled to said first inductor, the parameters of said inductors being chosen such that Tau is other than unity, where Tau=V₂ /V₁ √

L₁ /L₂ and L₁ and L₂ are the self-inductances of the respective first and second coupled inductors and V₁ and V₂ are the respective first and second input voltages, said ripple current through said second inductor being much lower than said ripple current through said first inductor.

22. A power supply circuit according to claim 21 wherein said first filter means additionally includes a first freewheeling diode for providing a path for the current through said first inductor when said voltage source is switched off, and

said second filter means additionally includes a second freewheeling diode for providing a path for the current through said second inductor when said voltage source is switched off.

25. A power supply circuit according to claim 21 or 23 wherein said voltage source is a chopped DC voltage source.

26. A power supply circuit according to claim 25 wherein said first filter means additionaly includes a first freewheeling diode for providing a path for the current through said first inductor when said voltage source is switched off, and

said second filter means additionally includes a second freewheeling diode for providing a path for the current through said second inductor when said voltage source is switched off.

23. A power supply circuit for producing a first output and a second output comprising:

a means for reducing current ripple further comprising;

a voltage source;

a transformer having a primary input coil, a first secondary output coil for providing a first input voltage and a second secondary output coil for providing a second input voltage, said primary input coil being connected to said voltage source;

a first diode connected to said first secondary output coil for rectifying said first input voltage;

a second diode connected to said second secondary output coil for rectifying said second input voltage;

a first filter means connected to said first secondary output coil through said first diode for filtering said first input voltage, said first filter means includes a first inductor; and

a second filter means connected to said second secondary output coil through and second diode for filtering said second input voltage, said second filter means includes a second inductor magnetically coupled to said first inductor, the parameters of said inductors being chosen such that Tau is other than unity, where Tau=V₂ /V₁ √

L₁ /L₂ and L₁ and L₂ are the self-inductances of the respective first and second coupled inductors and V₁ and V₂ are the respective first and second input voltages, said ripple current through said second inductor being essentially zero.

24. A power supply circuit according to claim 23 wherein said first filter means additionally includes a first freewheeling diode for providing a path for the current through said first inductor when said voltage source is switched off, and

said second filter means additionally includes a second freewheeling diode for providing a path for the current through said second inductor when said voltage source is switched off.

27. A power supply circuit for producing at least one output comprising:

a voltage source;

a transformer having a primary input coil connected to said voltage source and at least two secondary output coils for providing at least two secondary output coils for providing at least two input voltages;

a first output stage connected to one of said at least two secondary output coils, said first output stage including a first inductor; and

a second output stage connected to said first output stage and another one of said at least two secondary output coils for providing one of said at least one outputs, said second output stage including a second inductor magnetically coupled to said first inductor, the parameters of said inductors being chosen such that Tau is other than unity, where Tau=V₂ /V₁ √

L₁ /L₂ and L₁ and L₂ are the self-inductances of the respective first and second coupled inductors and V₁ and V₂ are the respective first and second input voltages, the ripple current through said second inductor being essentially zero.

28. A power supply circuit for producing a plurality of outputs comprising:

a voltage source;

transformer means having primary input coil means connected to said voltage source and a plurality of secondary output coil means of first and second classes, said plurality of secondary output coil means providing a plurality of input voltages; and

output stage means of said first class connected to said secondary output coil means of said first class and including inductor means carrying ripple current, and

a plurality of output stages of said second class for providing a plurality of outputs, each of said plurality of output stages of said second class connected to said secondary output coil means of said second class, each of said plurality of output stages of said second class including an inductor, each inductor being magnetically coupled to the inductor means of said output stage means of said first class, the parameters of said inductor means and said inductors being chosen such that the induced open-circuit voltages across each inductor included in said output stages of said second class (when the inductors included in said plurality of output stages of said second class are disconnected from their respective output stages) are approximately identical to the imposed operating voltages thereon when the inductors included in said plurality of output stages of said second class are connected to their respective output stages;

the ripple currents through the inductors included in said plurality of output stages of said second class being much lower than said ripple current in said inductor means of said first class.

30. A power supply circuit in accordance with claim 28 or claim 29 wherein said power supply circuit is a forward converter and wherein said output stages of said second class comprise averaging filters in which said inductors are filter inductors.

31. A power supply in accordance with claim 30, wherein all of said inductor means and said inductors are magnetically coupled by a common core.

29. A power supply circuit for producing a plurality of outputs comprising:

a voltage source;

a transformer having a primary input coil connected to said voltage source and a plurality of secondary output coil means of first and second classes, said plurality of secondary output coil means providing a plurality of input voltages; and

output stage means of said first class connected to said secondary output coil means of said first class and including inductor means carrying ripple current, and

a plurality of output stages of said second class for providing a plurality of outputs, each of said plurality of output stages of said second class connected to said secondary output coil means of said second class, each of said plurality of output stages of said second class including an inductor, each inductor being magnetically coupled to the inductor means of said output stage means of said first class, the parameters of said inductor means and said inductors being chosen such that the induced open-circuit voltages across each inductor included in said output stages of said second class (when the inductors included in said plurality of output stages of said second class are disconnected from their respective output stages) are substantially identical to the imposed operating voltages thereon when the inductors included in said plurality of output stages of said second class are connected to their respective output stages;

the ripple currents, arising from said imposed operating voltages, through the inductors included in said plurality of output stages of said second class being essentially zero.

32. A power supply circuit for producing a plurality of outputs comprising:

a voltage source;

transformer means having primary input coil means connected to said voltage source and secondary output coil means; and

output stage means of a first class connected to said secondary output coil means and including inductor means carrying ripple current, and

a plurality of output stages of a second class for providing a plurality of outputs, each of said plurality of output stages of said second class connected to said secondary coil means, each of said plurality of output stages of said second class including an inductor, each inductor being magnetically coupled to the inductor means of said output stage means of said first class,

said output coil means imposing proportionally related voltages on said output stages,

the parameters of said inductor means and said inductors being chosen such that the induced open-circuit voltages across each inductor included in said output stages of said second class (when the inductors included in said plurality of output stages of said second class are disconnected from their respective output stages) are approximately identical to the imposed operating voltages thereon when the inductors included in said plurality of output stages of said second class are connected to their respective output stages;

the ripple currents through the inductors included in said plurality of output stages of said second class being much lower than said ripple current in said inductor means of said first class.

34. A power supply circuit as claimed in claim 32 or 33 wherein said ripple currents in said inductors are essentially zero.

33. A power supply circuit for producing a plurality of outputs comprising:

voltage source means;

output stage means of a first class connected to said voltage source means and including inductor means carrying ripple current, and

a plurality of output stages of a second class for providing a plurality of outputs, each of said plurality of output stages of said second class connected to said voltage source means, each of said plurality of output stages of said second class including an inductor, each inductor being magnetically coupled to the inductor means of said output stage means of said first class,

said voltage source means imposing proportionally related voltages on said output stages,

the parameters of said inductor means and said inductors being chosen such that the induced open-circuit voltages across each inductor included in said output stages of said second class (when the inductors included in said plurality of output stages of said second class are disconnected from their respective output stages) are approximately identical to the imposed operating voltages thereon when the inductors included in said plurality of output stages of said second class are connected to their respective output stages;

the ripple currents through the inductors included in said plurality of output stages of said second class being much lower than said ripple current in said inductor means of said first class.