No load detection and slew rate compensation

• US 9,711,990 B2
• Filed: 06/21/2013
• Issued: 07/18/2017
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Flextronics America LLC (Flextronics International Limited)
• Original Assignee: Flextronics America LLC (Flextronics International Limited)
• Inventors: Telefus, Mark
• Primary Examiner(s): Behm, Harry
• Assistant Examiner(s): PEREZ, BRYAN REYNALDO
• Application Number:
  US13/924,388
• Publication Number:
  US 20140268912A1
• Time in Patent Office: 1,488 Days
• Field of Search: 363 2112, 363 2114, 363 44, 363 49, 713320, 323901
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/20 using microwaves or radio frequency waves
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge
• CPC Class Codes: H02M 3/28 using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
• CPC Class Codes: H02M 3/335 using semiconductor devices only
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

The power regulation control circuit is implemented during two modes. A first mode is a sleep mode and a second mode is a wake-up mode. During the sleep mode, the power supply detects a no-load presence and artificially increases the output voltage Vout to its maximum allowable value. In some embodiments, this is accomplished by pulling up an output of a error amplifier that feeds a PWM module. During the wake-up mode when the power supply wakes up from the sleep mode under maximum load, the output voltage Vout sinks from the artificially higher voltage, but still stays above a minimum operational voltage level. A slew rate compensation can be implemented to control a rate at which the output voltage drops when a load is applied. The artificially high output voltage during no-load condition and the slew rate compensation provide open loop voltage adjustment.

Claims

1. A method of controlling an output voltage of a power converter, the method comprising:

a. while in a sleep mode, periodically turning a main switch ON and OFF according to a burst mode of operation and detecting a load condition at an output of the power converter comprising the main switch coupled to a primary side winding and the load coupled to a secondary side winding, wherein the load condition causes the output voltage to decrease at a first rate during a wake-up time period, wherein a rate is an amount of output voltage decrease during the wake-up time period divided by the wake-up time period;

b. applying a plurality of slew rate compensation adjustments to a driving signal for the main switch of the power converter, wherein each slew rate compensation adjustment results in a voltage pull-up of the output voltage during the wake-up time period to decrease the first rate to a second rate at which the output voltage decreases during the wake-up period; and

c. discontinuing application of the plurality of slew rate compensation adjustments and resuming regulation of the output voltage at a regulated output voltage level after the wake-up time period.

2. The method of claim 1 wherein resuming regulation comprises discontinuing the slew rate compensation adjustments to the driving signal.

3. The method of claim 1 wherein applying the slew rate compensation adjustments comprises increasing the output voltage at successive periodic intervals.

4. The method of claim 1 wherein when the load is coupled to the output while in the sleep mode, the output voltage drops, further wherein applying the slew rate compensation adjustments comprises increasing the output voltage at successive periodic intervals.

5. The method of claim 1 wherein the sleep mode of operation comprises alternating periods of inactivity and burst periods of activity.

6. The method of claim 1 wherein the output voltage is periodically pulled-up according to a slope of an output voltage drop while the load condition is detected and before the controller wakes-up.

7. The method of claim 1 wherein during the wake-up time period after a load is applied, the output voltage drops from a regulated output voltage level to an intermediate voltage level that is within the acceptable operating voltage range and above an under voltage condition.

8. The method of claim 1 wherein during a wake-up time period after the load is applied, the output voltage drops from a regulated output voltage level to an intermediate voltage level that is within the acceptable operating voltage range and above an under voltage condition.

9. The method of claim 1 wherein being in the sleep mode corresponds to a no-load condition.

10. The method of claim 1 wherein each slew rate compensation adjustment is triggered according to a set RC time constant.

11. The method of claim 1 wherein the power converter further comprises a signal modulator connected to the main switch and an error amplifier connected to the signal modulator, wherein an error signal is output from the error amplifier to the signal modulator and the plurality of slew rate compensation adjustments are applied to the error signal.

12. A method of controlling an output voltage of a power converter, the method comprising:

a. determining between a load condition and a no-load condition at an output of the power converter, wherein the power converter comprises a main switch coupled to a primary side winding and a load coupled to a secondary side winding during the load condition;

b. when a no-load condition is detected, a controller of the power converter enters a sleep mode which includes periodically turning the main switch ON and OFF according to a burst mode of operation; and

c. when a load condition is detected while in the sleep mode, applying a plurality of slew rate compensation adjustments to a driving signal for the main switch of the power converter, wherein each slew rate compensation adjustment results in a voltage pull-up of the output voltage until the controller wakes-up, wherein the load condition causes the output voltage to decrease at a first rate during a wake-up time period and applying the slew rate compensation adjustments decreases the output voltage decrease to a second rate that is less than the first rate, wherein a rate is an amount of output voltage decrease during the wake-up time period divided by the wake-up time period.

13. The method of claim 12 further comprising discontinuing application of the plurality of slew rate compensation adjustments and resuming regulation of the output voltage at a regulated output voltage level once the controller wakes-up.

14. The method of claim 12 wherein applying the slew rate compensation adjustments comprises increasing the output voltage at successive periodic intervals.

15. The method of claim 12 wherein when the load is coupled to the output while the controller is in the sleep mode, the output voltage drops, further wherein applying the slew rate compensation adjustments comprises increasing the output voltage at successive periodic intervals.

16. The method of claim 12 wherein the sleep mode of operation comprises alternating periods of inactivity and burst periods of activity.

17. A power converter for regulating an output voltage supplied to a load, the power converter comprises a power regulation control circuit having a main switch coupled to a primary side winding and the load coupled to a secondary side winding, the power regulation control circuit configured to periodically turn the main switch ON and OFF according to a burst mode of operation while in a sleep mode and to detect a load condition at an output of the power converter while in the sleep mode, wherein the load condition causes the output voltage to decrease at a first rate during a wake-up time period, wherein a rate is an amount of output voltage decrease during the wake-up time period divided by the wake-up time period, apply a plurality of slew rate compensation adjustments to a driving signal for the main switch of the power converter, wherein each slew rate compensation adjustment results in a voltage pull-up of the output voltage during the wake-up time period to decrease the first rate to a second rate at which the output voltage decreases during the wake-up period, and discontinue application of the plurality of slew rate compensation adjustments and resume regulation of the output voltage at a regulated output voltage level after the wake-up time period.

18. The power converter of claim 17 wherein the output voltage remains within an acceptable operating voltage range that is below an over voltage condition and above an under voltage range while applying the slew rate compensation.

19. The power converter of claim 17 wherein the power regulation control circuit is configured to apply the slew rate compensation adjustments by increasing the output voltage at successive periodic intervals.

20. The power converter of claim 17 wherein the power regulation control circuit is configured to apply the slew rate compensation adjustments by providing voltage adjustments according to a slope of an output voltage level drop while the load is detected during the wake-up time period.