SAMPLE AND HOLD SCHEME FOR A FEEDBACK NETWORK OF A POWER CONVERTER

• US 20080297128A1
• Filed: 06/05/2008
• Published: 12/04/2008
• Est. Priority Date: 05/31/2007
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Xu, Jingwei, Zeng, Xianwei
• Granted Patent: US 7,859,131 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

One embodiment of the invention includes a system for regulating an output voltage of a power converter. The system comprises an error amplifier that compares a feedback voltage associated with the output voltage with a reference voltage to generate an error signal that is employed to control a magnitude of the output voltage. The system also comprises a plurality of sample and hold circuits each configured to sample an error amplifier output voltage to provide the error signal. The system further comprises a switching controller configured to control switching of the error amplifier output voltage between each of the plurality of sample and hold circuits in response to a change in an output load of the power converter.

Claims

1. A system for regulating an output voltage of a power converter, the system comprising:

an error amplifier that compares a feedback voltage associated with the output voltage with a reference voltage to generate an error signal that is employed to control a magnitude of the output voltage;

a plurality of sample and hold circuits each configured to sample an error amplifier output voltage to provide the error signal; and

a switching controller configured to control switching of the error amplifier output voltage between each of the plurality of sample and hold circuits in response to a change in an output load of the power converter.

2. The system of claim 1, wherein the switching controller is further configured to control switching of the output voltage between each of a plurality of output loads concurrently with the switching of the error amplifier output voltage between each of the plurality of sample and hold circuits.

3. The system of claim 2, wherein each of the plurality of sample and hold circuits sample and hold the error amplifier output voltage that corresponds to a respective one of the plurality of output loads that is provided the output voltage.

4. The system of claim 2, wherein the switching controller sequentially switches the output voltage between the plurality of output loads based on a predetermined sequence.

5. The system of claim 4, wherein the switching controller concurrently disconnects the output voltage from a given load and an associated sample and hold circuit and connects a subsequent load to the output voltage and a subsequent sample and hold circuit to the error amplifier.

6. The system of claim 2, wherein the plurality of output loads comprise a plurality of series-connected LED strings and associated current regulators.

7. The system of claim 6, wherein the brightness of each of the plurality of series-connected LED strings is controlled based on a pulse-width of a respective enable signal output from the switching controller to switch the output voltage to a respective series-connected LED string.

8. The system of claim 1, wherein the plurality of sample and hold circuits comprises an off-state sample and hold circuit configured to sample the error amplifier output voltage and to provide the error amplifier output voltage to the input of the error amplifier in response to the output load being disconnected from the power converter.

9. The system of claim 1, wherein each of the plurality of sample and hold circuits comprises a switch and a feedback capacitor, the feedback capacitor being configured to sample the error amplifier output voltage and provide the error amplifier output voltage to the input of the error amplifier upon the switch being activated.

10. A portable electronic device comprising the system of claim 1.

11. A method for regulating power to a plurality of output loads, the method comprising:

generating an output voltage from a power converter based on a feedback voltage associated with an error amplifier;

sequentially switching the output voltage between each of the plurality of output loads; and

sequentially switching an error amplifier output voltage between a plurality of corresponding sample and hold circuits concurrently with each switching of the output voltage.

12. The method of claim 11, wherein switching between the plurality of sample and hold circuits comprises switching between a plurality of feedback capacitors each configured to sample and provide the error amplifier output voltage to an input of the error amplifier.

13. The method of claim 12, wherein the sequentially switching the output voltage and the sequentially switching the error amplifier output voltage is in response to enabling of associated enable signals.

14. The method of claim 13, wherein the plurality of output loads comprise a plurality of series-connected LED strings and associated current regulators, the method further comprising setting a brightness of the plurality of LED strings based on a pulse-width of the associated enable signals.

15. The method of claim 11, wherein sequentially switching between the respective plurality of sample and hold circuits comprises switching to an off-state sample and hold circuit when an output load is not connected to the output voltage.

16. The method of claim 11, wherein sequentially switching the error amplifier output voltage between the respective plurality of sample and hold circuits comprises:

sampling and providing the error amplifier output voltage associated with a respective one of the plurality of output loads to an input of the error amplifier associated with the feedback voltage;

comparing the feedback voltage with a reference voltage to generate the error amplifier output voltage; and

controlling a magnitude of the output voltage based on the error amplifier output voltage.

17. A system for regulating an output voltage of a power converter, the system comprising:

means for generating an output voltage;

means for adjusting the output voltage based on an error voltage;

means for switching between an on-state that provides the output voltage to an output load and an off-state that disconnects the output voltage from the output load;

a first means for sampling and providing the error voltage to the means for adjusting during the on-state; and

a second means for sampling and providing the error voltage to the means for adjusting during the off-state.

18. The system of claim 17, wherein the means for switching further comprises sequentially switching the output voltage between a plurality of output loads in a predetermined sequence.

19. The system of claim 17, further comprising a plurality of means for sampling and providing the error voltage to the means for adjusting and means for sequentially switching between the plurality of means for sampling concurrently with the sequentially switching the output voltage between the plurality of loads.

20. The system of claim 17, wherein the output load comprises a plurality of series-connected LED strings and associated current regulators, wherein a pulse-width of enable signals configured to control the means for switching between the on-state and the off-state and the means for sequentially switching between the plurality of means for sampling controls the brightness of the series-connected LED strings.