Method and apparatus for inductive-kick protection clamp during discontinuous conduction mode operation

Patent metadata

Field	Value
Publication number	US-9825521-B2
Application number	US-201414466463-A
Country	US
Kind code	B2
Filing date	Aug 22, 2014
Priority date	Aug 22, 2014
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

A method includes determining that a current at an inductor in a series transfer capacitor buck converter is decaying to zero during a first cycle. The method also includes, in response to determining that the current at the inductor is decaying to zero, enabling an electrostatic discharge (ESD) structure and turning off a low side transistor. The ESD structure is disposed at a node connecting the low side transistor, a high side transistor and the inductor. The method further includes disabling the ESD structure before the high side transistor is turned on during a next cycle following the first cycle.

First claim

What is claimed is:

1. A method comprising:
determining that a current at an inductor in a series transfer capacitor buck converter is decaying to zero during a first cycle;
in response to determining that the current at the inductor is decaying to zero, enabling an electrostatic discharge (ESD) structure and turning off a low side transistor, the ESD structure disposed at a node connecting the low side transistor, a high side transistor and the inductor; and
disabling the ESD structure before the high side transistor is turned on during a next cycle following the first cycle; wherein enabling the ESD structure clamps a voltage rise at the node caused by turning off the low side transistor.

2. The method of claim 1 , wherein turning on the low side transistor during the first cycle, wherein the current at the inductor decays to zero in response to the low side transistor turning on.

3. The method of claim 1 , wherein the ESD structure is enabled just before the low side transistor is turned off.

4. The method of claim 1 , wherein the low side transistor is rated for a voltage that is approximately one half of a supply voltage.

5. The method of claim 1 , wherein the low side transistor is a low side synchronous rectifier power field effect transistor (FET) and the high side transistor is a high side power FET.

6. The method of claim 1 , wherein the series transfer capacitor buck converter further comprises a transfer capacitor disposed between two half bridge circuits, the transfer capacitor having a charge capacity approximately equal to one-half of a supply voltage.

7. The method of claim 1 , wherein the ESD structure comprises an ESD field effect transistor (FET).

8. An apparatus comprising:
a series transfer capacitor buck converter configured to be coupled to a power supply, the series transfer capacitor buck converter comprising an inductor, a low side transistor, and a high side transistor;
an electrostatic discharge (ESD) structure disposed at a node connecting the low side transistor, the high side transistor, and the inductor; and
a controller configured to:
determine that a current at the inductor is decaying to zero during a first cycle;
in response to determining that the current at the inductor is decaying to zero, enable the ESD structure and turn off the low side transistor;
disable the ESD structure before the high side transistor is turned on during a next cycle following the first cycle; and
turn on the low side transistor during the first cycle and cause the current at the inductor to decay to zero;
wherein the ESD structure is configured when enabled to clamp a voltage rise at the node caused by turning off the low side transistor.

9. The apparatus of claim 8 , wherein the ESD structure is enabled just before the low side transistor is turned off.

10. The apparatus of claim 8 , wherein the low side transistor is rated for a voltage that is approximately one-half of a supply voltage.

11. The apparatus of claim 8 , wherein the low side transistor is a low side synchronous rectifier power field effect transistor (FET) and the high side transistor is a high side power FET.

12. The apparatus of claim 8 , wherein the series transfer capacitor buck converter further comprises a transfer capacitor disposed between two half bridge circuits, the transfer capacitor having a charge capacity approximately equal to one-half of a supply voltage.

13. The apparatus of claim 8 , wherein the ESD structure comprises an ESD field effect transistor (FET).

14. A series transfer capacitor buck converter circuitry comprising:
an inductor;
a low side transistor;
a high side transistor;
an electrostatic discharge (ESD) structure disposed at a node connecting the low side transistor, the high side transistor, and the inductor; and
control circuitry configured, in a discontinuous conduction mode of the series transfer capacitor buck converter circuitry, to:
determine that a current at the inductor is decaying to zero during a first cycle;
in response to determining that the current at the inductor is decaying to zero, enable the ESD structure and turn off the low side transistor;
disable the ESD structure before the high side transistor is turned on during a next cycle following the first cycle; and
turn on the low side transistor during the first cycle and cause the current at the inductor to decay to zero;
wherein the ESD structure is configured when enabled to clamp a voltage rise at the node caused by turning off the low side transistor.

15. The series transfer capacitor buck converter circuitry of claim 14 , wherein the ESD structure is enabled just before the low side transistor is turned off.

16. The series transfer capacitor buck converter circuitry of claim 14 , wherein the low side transistor is rated for a voltage that is approximately one-half of a supply voltage.

Assignees

• Texas Instruments Inc

Inventors

• Khayat Joseph Maurice

Classifications

• Y02B70/1466

  Cross-Sectional Technologies · mapped topic

• H02M1/34 Primary

  Snubber circuits · CPC title

• H02M2001/344

  Electricity · mapped topic

• H02M3/005

  using Cuk converters · CPC title

• H02M3/1588

  comprising at least one synchronous rectifier element (H02M3/1582, H02M3/1584 take precedence) · CPC title