Droop reduction circuit for charge pump buck converter

• US 9,413,232 B2
• Filed: 06/09/2015
• Issued: 08/09/2016
• Est. Priority Date: 06/30/2014
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Torres, Erick Omar, Jang, Byungchul
• Primary Examiner(s): KIM, JUNG H
• Application Number:
  US14/734,720
• Publication Number:
  US 20150381035A1
• Time in Patent Office: 427 Days
• US Class Current: 1/1
• 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 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence
• CPC Class Codes: H02M 3/16 by dynamic converters
• CPC Class Codes: H02M 3/285 Single converters with a plurality of output stages connected in parallel parallel operation of a plurality of converters in dc distribution networks H02J1/10

Abstract

A Charge Pump Buck Converter (CPBC) includes a BC including an inductor and a CP coupled in parallel. Control logic is coupled to a switch driver coupled to a power switch(es). Control circuitry includes a voltage sensor sensing Vout and a voltage level generator for generating a first voltage level coupled to the CP stage and a second voltage level coupled to a duty cycle/rate generator block providing an input to an under voltage (UV) monitor coupled between OUT and the control logic. The control circuitry disables the CP when Vout>a first Vout level and controls the BC to regulate to a second Vout level>the first Vout level. During handoff between CP and BC during power up if Vout drops below a UV threshold, the UV monitor block modifies an input applied to the control logic for increasing charging supplied to the inductor.

Claims

1. A method of power conversion, the method comprising:

using a charge pump buck converter (CPBC) that includes;

a charge pump (CP) stage;

a buck converter (BC) stage connected in parallel with said CP stage between an input terminal (IN) and an output terminal (OUT);

control logic coupled through a switch driver to a least one control node of at least one power switch for driving an inductor of said BC stage; and

control circuitry including a duty cycle or repetition rate generator block (cycle/rate generator block);

wherein using said CPBC includes;

providing a first voltage level, which is coupled to said CP stage;

providing a second voltage level, which is coupled to said cycle/rate generator block, said first voltage level being above said second voltage level;

using said cycle/rate generator block to provide a duty cycle or repetition rate output coupled to an input of an under voltage (UV) monitor block, wherein said UV monitor block includes a UV comparator triggered by a UV threshold and is coupled between said OUT and an input of said control logic;

during a power up, when a voltage at said IN (Vin) is rising with time;

applying clock signals to said CP stage to increase a voltage at said OUT (Vout);

responsive to said Vout exceeding a first output voltage level (first Vout level), disabling said CP stage;

responsive to said Vin exceeding an input reference voltage, controlling said BC stage to regulate said Vout at a second Vout level that is above said first Vout level;

tracking said Vout using said UV monitor block; and

during a handoff between said CP stage and said BC stage during said power up, if said Vout drops below said UV threshold, using said UV monitor block to modify said input of said control logic to increase charging supplied to said inductor.

2. The method of claim 1, wherein using said CPBC includes:

using a voltage divider coupled between said OUT and a ground to;

provide said first voltage level, which is coupled through a first tap to said CP stage; and

provide said second voltage level, which is coupled through a second tap to said cycle/rate generator block.

3. The method of claim 1, further comprising ignoring said UV monitor block so that said control circuitry operates without influence from said UV monitor block except during said handoff.

4. The method of claim 1, wherein said ignoring is implemented with a counter having a counter time that is triggered by an enable signal sent upon said disabling of said CP stage.

5. The method of claim 4, wherein said counter time is >

a time for said BC stage to settle.

6. The method of claim 1, wherein said UV threshold (V_{REF_UV}) has hysteresis and is below a regulation point to allow said control circuitry to settle.

7. The method of claim 1, wherein said cycle/rate generator block comprises a pulse width generator block and said control logic comprises a pulse width modulation (PWM) controller.

8. The method of claim 1, wherein said cycle/rate generator block comprises a duty cycle generator block and said control logic comprises a pulse frequency modulation (PFM) controller.

9. The method of claim 7, wherein said CPBC further comprises a compensation network including a compensation capacitor between an input of said PWM controller and a ground.

10. A charge pump buck converter (CPBC), comprising:

a charge pump (CP) stage;

a bunk converter (BC) stage connected in parallel with said CP stage between an input terminal (IN) and an output terminal (OUT) of said CPBC, including at least one power switch for driving an inductor;

control logic coupled through a switch driver to at least one control node of said at least one power switch; and

control circuitry coupled to said OUT for;

sensing a voltage at said OUT (VOUT);

providing a first voltage level, which is coupled to said CP stage;

providing a second voltage level, which is coupled to a duty cycle or repetition rate generator block (cycle/rate generator block), said first voltage level being above said second voltage level, wherein said cycle generator block is for providing a duty cycle Or repetition rate output coupled to an input of an under voltage (UV) monitor block, and wherein said UV monitor block includes a UV comparator triggered by a UV threshold and is coupled between said OUT and an input of said control logic;

disabling said CP stage responsive to said Vout exceeding a first Vout level; and

controlling said BC stage to regulate said Vout at a second Vout level that is above said first Vout level;

wherein said UV monitor block is for;

tracking said Vout; and

, during a handoff between said CP stage and said BC stage during a power up, if said Vout drops below said UV threshold, modifying said input of said control logic to increase charging supplied to said inductor.

11. The CPBC of claim 10, wherein:

said control circuitry includes a voltage divider coupled between said OUT and a ground; and

said voltage divider includes;

a first tap for providing said first voltage level; and

a second tap for providing said second voltage level.

12. The CPBC of claim 10, wherein said UV monitor block further includes logic so that said control circuitry operates without influence from said UV monitor block except during said handoff.

13. The CPBC of claim 12, wherein said UV monitor block further comprises a counter having a counter time that is triggered by an enable signal sent upon said disabling of said CP stage.

14. CPBC of claim 10, wherein said UV threshold (V_{REF_UV}) has hysteresis and is below a regulation point to allow said control circuitry to settle.

15. The CPBC of claim 10, wherein said cycle/rate generator block comprises a pulse width generator block and said control logic comprises a pulse width modulation (PWM) controller.

16. The CPBC of claim 10, wherein said cycle/rate generator block comprises a duty cycle generator block and said control logic comprises a pulse frequency modulation (PFM) controller.

17. The CPBC of claim 15, further comprising a compensation network including a compensation capacitor between an input of said PWM controller and a ground.