Self synchronizing power converter apparatus and method suitable for auxiliary bias for dynamic load applications

• US 8,824,167 B2
• Filed: 07/18/2011
• Issued: 09/02/2014
• Est. Priority Date: 07/18/2011
• Status: Active Grant

• Current Assignee: Crane Electronics, Inc. (Crane Company)
• Original Assignee: Crane Electronics, Inc. (Crane Company)
• Inventors: Hughes, Rodney Alan, Adriance, Reid, Nkei, Bertrand, Kuehny, Jay Allen
• Primary Examiner(s): PATEL, RAJNIKANT B
• Application Number:
  US13/185,217
• Publication Number:
  US 20130020867A1
• Time in Patent Office: 1,142 Days
• Field of Search: 363 16- 20, 363/25, 363/26, 363/21.02, 363/21.13, 363/37, 363/41, 363/89, 363/97, 363/98, 323/222, 323/235, 323282-290, 323/299, 323311-316, 323/251
• US Class Current: 363/17
• CPC Class Codes: H02J 3/12 for adjusting voltage in ac networks by changing a characteristic of the network load
• CPC Class Codes: H02M 1/0006 Arrangements for supplying an adequate voltage to the control circuit of converters
• CPC Class Codes: H02M 1/0019 the disturbance parameters being load current fluctuations
• 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

Abstract

An auxiliary power supply or bias voltage supply employs a step up switch mode DC/DC power converter topology to supply regulated bias supply voltages, from very low input voltages (e.g., less than 2V). The supply will synchronize to dynamic loads making it particularly useful in circuits with periodic high peak current power demands, for example, gate drive circuits employed in regulated switched mode power converters. When unladed, the supply will efficiently adjust its cycle period to the minimum required to maintain the desired boosted output voltage. Additional transformer windings or a charge pump may be used to generate additional vias voltage sources.

Claims

1. A bias voltage supply to supply multiple regulated bias supply potentials to dynamic loads, comprising:

a DC/DC converter including a transformer having at least a first winding, a second winding and a core, the first winding coupled at a first node to receive an input at a first input potential and coupled at a second node to provide a first output potential and a second output potential with an output voltage which is higher than an input voltage supplied to the DC/DC converter, the DC/DC converter also including a converter switch operable to selectively couple the second node of the first winding to a ground reference node;

an error circuit coupled to control the converter switch through the second winding of the transformer based at least in part on a difference between the first output potential and a reference potential; and

a synchronization capacitance electrically coupled in parallel with the diode between the first winding and the VCC output node that in response to a dynamic load condition provides a signal that is reflected by the first winding across the transformer to the second winding to drive the converter switch to synchronize operation with a periodic load demand.

2. The bias voltage supply of claim 1 wherein the synchronization capacitance is supplied at least in part by a parasitic capacitance of an output diode electrically coupled between the second node of the first winding and a VCC output node and at least in part by a substrate capacitive coupling.

3. The bias voltage supply of claim 1 wherein the error circuit sums the first output potential and the reference potential and produces a time average of a difference between the first output potential and the reference potential.

4. The bias voltage supply of claim 3 wherein the error circuit produces a time average of a difference between the first output potential and the reference potential.

5. The bias voltage supply of claim 3 wherein the error circuit includes an error amplifier that sums the first output potential and the reference potential, and further comprising:

an integration capacitor that feeds back an output of the error amplifier to an input of the error amplifier.

6. The bias voltage supply of claim 5 wherein the error circuit includes a current mirror coupled to reflect an output of the error amplifier to the second winding of the transformer.

7. The bias voltage supply of claim 3 wherein the error circuit includes a bipolar voltage-to-current converter, a control capacitance, a unipolar voltage-to-current converter a drive capacitance, and a drive resistor, the bipolar voltage-to-current converter coupled to receive the sum of the first output potential and the reference potential and to charge the control capacitance, the unipolar voltage-to-current converter coupled to be driven by a potential of the control capacitance and to charge the drive capacitance, the drive capacitance coupled to drive the second winding of the transformer through the drive resistor.

8. The bias voltage supply of claim 7 wherein the unipolar voltage-to-current converter includes a transistor, a base diode and an emitter resistor, the transistor having a base coupled to a ground reference node via the base diode, an emitter coupled to the control capacitance via the emitter resistor, and a collector coupled to the drive capacitance.

9. The bias voltage supply of claim 1, further comprising:

a charge pump coupled to the second node of the first winding of the transformer to supply the second output potential.

10. The bias voltage supply of claim 9 wherein the first output potential is supplied at a VCC output node and wherein the charge pump includes a charge pump capacitor, a VSS output capacitor and a pair of charge pump diodes, a first one of the charge pump diodes coupled between the charge pump capacitor and a ground node and a second one of the charge pump diodes electrically coupled between the charge pump capacitor and a VSS potential output node, the VSS output capacitor electrically coupled between a first node between the first charge pump diode and the ground and a second node between the second charge pump diode and the VSS potential output node.

11. The bias voltage supply of claim 1, further comprising:

an over voltage clamp circuit coupled to turn OFF the converter switch in response to a transient condition in at least one of the first input potential or the first output potential.

12. The auxiliary voltage supply of claim 1 wherein the transformer includes at least a third winding to supply a third output potential which is different than the first and the second potentials.

13. An auxiliary voltage supply to supply a VCC supply potential and a VSS supply potential to dynamic loads, comprising:

a transformer having at least a first winding, a second winding and a core;

a converter switch operable to selectively couple the first winding to a ground reference node;

a drive capacitance coupled to drive the converter switch; and

a synchronization capacitance,

wherein the transformer, the converter switch and the drive capacitance are coupled in a positive feedback loop such that as a current flow through the first winding via the converter switch increases, the first winding reflects a corresponding voltage change to the second winding that increases a drive voltage to turn the converter switch full ON and as current flow through the first winding via the converter switch decreases, the first winding reflects a corresponding voltage change to the second winding that decreases the drive voltage to turn the converter switch full OFF; and

wherein the transformer, the converter switch and the synchronization capacitance are coupled such that in response to a dynamic load current demand larger than a threshold the first winding reflects a voltage pulse to the second winding to turn the converter switch ON to synchronize a cycle of the bias voltage supply.

14. The auxiliary voltage supply of claim 13 wherein the synchronization capacitance is supplied at least in part by a parasitic capacitance of an output diode electrically coupled between the first winding and a VCC output node.

15. The auxiliary voltage supply of claim 14 wherein the synchronization capacitance is supplied at least in part by a parasitic substrate capacitive coupling.

16. The auxiliary voltage supply of claim 13, further comprising:

an error circuit coupled to control the converter switch through the second winding of the transformer based at least in part on a difference between an output voltage and a reference voltage.

17. The auxiliary voltage supply of claim 16 wherein the error circuit produces a time averaged difference of the sum of the VCC supply potential and a reference potential.

18. The auxiliary voltage supply of claim 13 wherein the transformer includes at least a third winding.

19. A method of operating an auxiliary voltage supply to supply a VCC supply potential and a VSS supply potential to dynamic loads, the auxiliary voltage supply comprising a transformer having at least a first winding, a second winding and a core;

a converter switch operable to selectively couple the first winding to a ground reference node;

a drive capacitance coupled to drive the converter switch; and

a synchronization capacitance, the method comprising;

increasing a supply of current via the converter switch to the first winding of the transformer;

in response to an increase in current flow through the first winding via the converter switch, reflecting a corresponding voltage change by the first winding to the second winding;

increasing a drive voltage to turn the converter switch full ON in response to the reflection of the voltage change corresponding to the increase in current flow through the first winding;

decreasing the supply of current via the converter switch to the first winding of the transformer;

in response to the decrease in current flow through the first winding via the converter switch, reflecting a corresponding voltage change by the first winding to the second winding;

decreasing a drive voltage to turn the converter switch OFF in response to the reflection of the voltage change corresponding to the decrease in current flow through the first winding;

in response to a dynamic load current demand larger than a threshold, providing a voltage pulse to the first winding by the synchronization capacitance;

reflecting the voltage pulse by the first winding to the second winding; and

applying the voltage pulse via the second winding to turn the converter switch ON to synchronize a cycle of the bias voltage supply.

20. The method of claim 19, further comprising:

determining a difference between an output voltage and a reference voltage; and

applying a signal to the second winding based on the determined difference.

21. The method of claim 19, further comprising:

determining a time averaged difference of a sum of the VCC supply potential and a reference potential; and

applying a signal to the second winding based on the determined time averaged difference.

22. The method of claim 19, further comprising:

driving a charge pump coupled to the first winding of the transformer to supply the VSS supply potential.