Method and apparatus for zero-current switching control in switched-capacitor converters

Patent metadata

Field	Value
Publication number	US-10122256-B1
Application number	US-201715648764-A
Country	US
Kind code	B1
Filing date	Jul 13, 2017
Priority date	Jul 13, 2017
Publication date	Nov 6, 2018
Grant date	Nov 6, 2018

Abstract

A switched-capacitor converter includes a plurality of legs coupled between the input and a rectifier at the output. Each leg includes a capacitor. A first group of legs is coupled to a first branch of the rectifier, and a second group is coupled to a second branch of the rectifier. A switch device is connected to each leg. The controller alternates switching of the switch devices connected to the first and second groups of legs to transfer energy from input to output. The switching is modified based on zero-crossing information which indicates when current through each switch device crosses or nearly crosses zero, so that each switch device connected to the same group of legs is turned off when current through that switch device crosses or nearly crosses zero and remains off until all switch devices connected to that group have been turned off for a predetermined amount of time.

First claim

What is claimed is:

1. A switched-capacitor converter, comprising:
an input;
an output;
a rectifier at the output;
a plurality of legs coupled between the input and the rectifier, each leg comprising a capacitor, a first group of the legs being coupled to a first branch of the rectifier and a second group of the legs being coupled to a second branch of the rectifier;
a switch device connected to each leg; and
a controller operable to alternate switching of the switch devices connected to the first and the second groups of legs to transfer energy from the input to the output,
wherein the switching is modified based on zero-crossing information which indicates, for each leg of the first group of legs, when current through the switch device connected to said each leg crosses or nearly crosses zero, so that each switch device connected to a leg within the first group of legs is turned off when the current through that switch device crosses or nearly crosses zero and remains off until all switch devices connected to legs within the first group of legs have been turned off for a predetermined amount of time, and
wherein at least two switch devices connected to legs within the first group of legs are turned on for partially overlapping time intervals within a switching cycle, the partially overlapping time intervals having different time durations.

2. The switched-capacitor converter of claim 1 , wherein the zero-crossing information comprises sensed current through each switch device.

3. The switched-capacitor converter of claim 1 , wherein the zero-crossing information comprises a derivative of a sensed capacitor voltage across each capacitor of the legs.

4. The switched-capacitor converter of claim 1 , wherein the controller is operable to produce an individual PWM (pulse width modulation) signal for switching each switch device, and wherein the controller is operable to adjust the duty cycle of each PWM signal based on the zero-crossing information for the corresponding switch device so that the duty cycle for each switch device corresponds to the zero-crossing current of that switch device.

5. The switched-capacitor converter of claim 1 , wherein each switch device connected to the first group of legs is implemented as an integrated power stage configured to sense output current of the power stage, wherein the controller is operable to produce a single PWM (pulse width modulation) signal for switching each switch device connected to the first group of legs, and wherein each integrated power stage is operable to adjust the duty cycle of the PWM signal based on the output current of the power stage so that the duty cycle for the switch device included in the power stage corresponds to the zero-crossing current of that switch device.

6. The switched-capacitor converter of claim 1 , wherein each leg in the first group includes an inductor connected to the capacitor of that leg, wherein the inductor is formed by a first winding of a current transformer, and wherein the zero-crossing information for each leg in the first group is obtained by a sense circuit connected to a second winding of the current transformer of that leg, the sense circuit being configured to sense the zero-crossing current of the switch device connected to the corresponding leg.

7. The switched-capacitor converter of claim 1 , wherein each leg in the first group includes an inductor connected to the capacitor of that leg, and wherein the zero-crossing information for each leg in the first group is obtained by a DCR sense circuit connected to the inductor of that leg, the DCR sense circuit being configured to sense the zero-crossing current of the switch device connected to the corresponding leg.

8. The switched-capacitor converter of claim 1 , wherein each leg in the first group includes an inductor connected to the capacitor of that leg, and wherein the zero-crossing information for each leg in the first group is obtained by a sense circuit configured to sense a voltage across the inductor of that leg, referenced to ground, and wherein the controller is operable to account for mismatch in sensing the zero-crossing of a voltage across each inductor.

9. The switched-capacitor converter of claim 1 , wherein each switch device connected to the first group of legs is implemented as an integrated power stage configured to sense output current of the power stage, and wherein the zero-crossing information for each leg in the first group is derived from the output current sensed by the integrated power stage of that leg.

10. The switched-capacitor converter of claim 1 , wherein the zero-crossing information for each leg is derived from an on-state resistance measurement for the switch device connected to that leg.

11. The switched-capacitor converter of claim 1 , wherein each branch of the rectifier comprises an integrated power stage configured to sense current through that branch, and wherein the zero-crossing information for each leg is derived from the current sensed by the integrated power stage of the branch coupled to that leg.

12. The switched-capacitor converter of claim 1 , wherein the controller is operable to switch the first group of legs on during a first part of each switching cycle and off during a second part of each switching cycle, wherein the controller is operable to switch the second group of legs off during the first part of each switching cycle and on during the second part of each switching cycle, and wherein the controller is operable to use the same zero-crossing information determined for the present switching cycle to modify the point at which each switch device connected to the first group of legs is switched off during the first part of the present switching cycle and modify the point at which each switch device connected to the second group of legs is switched off during the second part of the present switching cycle.

13. The switched-capacitor converter of claim 1 , wherein the controller is operable to switch the first group of legs on during a first part of each switching cycle and off during a second part of each switching cycle, wherein the controller is operable to switch the second group of legs off during the first part of each switching cycle and on during the second part of each switching cycle, wherein the controller is operable to use first zero-crossing information determined for the first part of the present switching cycle to modify the point at which each switch device connected to the first group of legs is switched off during the first part of the present switching cycle, and wherein the controller is operable to use second zero-crossing information determined for the second part of the present switching cycle to modify the point at which each switch device connected to the second group of legs is switched off during the second part of the present switching cycle.

14. A method of operating a switched-capacitor converter that includes an input, an output, a rectifier at the output, and a plurality of legs coupled between the input and the rectifier, each leg comprising a capacitor, a first group of the legs being coupled to a first branch of the rectifier and a second group of the legs being coupled to a second branch of the rectifier, and a switch device connected to each leg, the method comprising:
alternately switching the switch devices connected to the first and the second groups of legs to transfer energy from the input to the output; and
modifying the switching based on zero-crossing information which indicates, for each leg of the first group of legs, when current through the switch device connected to said each leg crosses or nearly cr

Assignees

• Infineon Technologies Austria Ag

Inventors

• Babazadeh Amir
• Renganathan Rakesh
• Clavette Danny
• Rainer Christian

Classifications

• H02M3/33507 Primary

  with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence) · CPC title

• H02M3/18

  using capacitors or batteries which are alternately charged and discharged, e.g. charged in parallel and discharged in series · CPC title

• H02M7/219

  in a bridge configuration · CPC title

• H02M1/08

  Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters · CPC title

• H02M2001/0058

  Electricity · mapped topic