Adjustable blanking time for overload protection for switch-mode power supplies

Patent metadata

Field	Value
Publication number	US-9570994-B1
Application number	US-201514823860-A
Country	US
Kind code	B1
Filing date	Aug 11, 2015
Priority date	Aug 11, 2015
Publication date	Feb 14, 2017
Grant date	Feb 14, 2017

Abstract

A blanking time for a switch-mode power supply controller includes a first blanking time interval and a second blanking time interval. During the first blanking time interval, the time to charge the feedback voltage at the feedback input of the switch-mode power supply is measured, and a timer setting time is stored based on the measured time. During the second time interval, a series of charge cycles is used. At each charge cycle, the feedback voltage is discharged and then allowed to charge. If, after being discharged, the feedback voltage reaches a voltage threshold during the timer setting time, a counter value is incremented and the next cycle begins. If the feedback voltage does not reach the voltage threshold within the timer setting time, the blanking time ends. If the counter value reaches a count threshold, a shutdown mode is initiated.

First claim

What is claimed is:

1. A device for overload protection, comprising:
a switch-mode power supply controller, including:
a feedback pin that is coupled to a feedback node;
a logic circuit that is arranged to determine whether a fault condition has ended by an end of a first blanking time interval;
a capacitor size counter that is arranged to, if the logic circuit determines that the fault condition has not ended by the end of the first blanking time interval, during the first blanking time interval, measure a time that is based on an external component that is coupled to the feedback pin;
a preset timer setting circuit that is arranged to, if the logic circuit determines that the fault condition has not ended by the end of the first blanking time interval, store a preset timer setting that is based on the measured time,
wherein the logic circuit is further arranged to, if the logic circuit determines that the fault condition has not ended by the end of the first blanking time interval, during a second blanking time interval that follows the first blanking time interval, perform a charge cycle sequence such that a duration of the second blanking time interval is based on the preset timer setting, and
wherein performing the charge cycle sequence includes:
determining whether a fault condition has ended during the second blanking time interval;
if a fault condition is determined to have ended during the second blanking time interval, controlling ending the second blanking time interval and restarting controlling regulation of an output voltage based on a feedback voltage at the feedback node; and
if the fault condition is determined not to have ended during the second blanking time interval, initiating a shutdown mode.

2. The device of claim 1 , wherein
the logic circuit is arranged to:
during the first blanking time interval, control discharging of the feedback voltage to a first voltage level, wherein the logic circuit is arranged to determine whether the fault condition has ended by the end of the first blanking time interval by determining whether the feedback voltage reaches a second voltage level during the first blanking time interval after being discharged to the first voltage level;
after discharging the feedback voltage to the first voltage level during the first blanking time interval, control ending the first blanking time interval and restarting controlling regulation of the output voltage based on the feedback voltage if the feedback voltage did not reach the second voltage level during the first blanking time interval, wherein the capacitor size counter is arranged to, if the feedback voltage reached the second voltage level during the first blanking time interval, measure the time that is based on a size of an external component that is coupled to the feedback pin by measuring the time as how much time occurs between the feedback voltage being at the first voltage level and the feedback voltage being at the second voltage level, and wherein the logic circuit is arranged to perform a charge cycle sequence by beginning a first charge cycle of the second blanking time interval, wherein the logic circuit is arranged to control a second cycle of the second blanking time interval such that the second cycle of the second blanking time interval includes:
discharging the feedback voltage to the first voltage level;
determining whether the feedback voltage reaches the second voltage level within the timer setting time after the feedback voltage was last discharged to the first voltage level;
if the feedback voltage fails to reach the second voltage level within the timer setting time after the feedback voltage was last discharged to the first voltage level, ending the second blanking time interval and restarting controlling regulation of the output voltage based on the feedback voltage;
if the feedback voltage reaches the second voltage level within the timer setting time after the feedback voltage was last discharged to the first voltage level, incrementing a charge cycle counter value;
after incrementing the charge cycle counter value, if the charge cycle counter has reached a charge cycle count threshold, initiating the shutdown mode; and
after incrementing the charge cycle counter value, if the charge cycle counter has failed to reach the charge cycle count threshold, beginning a next charge cycle of the second blanking time interval.

3. The device of claim 2 , wherein the switch-mode power supply controller further includes a transistor that is coupled to the feedback pin and a pull-up resistor that is coupled to the feedback pin, wherein the logic circuit is arranged to control discharging of the feedback voltage to the first voltage level during the first blanking time interval by controlling the transistor, and wherein the logic circuit is further arranged to control charging of the feedback voltage via the transistor and the pull-up resistor.

4. The device of claim 2 , wherein the charge cycle count threshold is at least two hundred fifty six.

5. The device of claim 1 , further comprising a compensation network that is external to the switch-mode power supply controller, wherein the compensation network includes an external capacitor that is coupled to the feedback pin.

6. The device of claim 5 , wherein the time that occurs between the feedback voltage being at a first voltage level and the feedback voltage being at a second voltage level is based on a size of the capacitor that is coupled to the feedback pin, wherein the capacitor is the external component that is coupled to the feedback pin.

7. The device of claim 1 , further comprising a switch-mode power supply that includes the switch-mode power supply controller.

8. The device of claim 7 , wherein the switch-mode power supply is a half-bridge resonant LLC switch-mode power supply.

9. A method for overload protection, comprising:
determining whether a fault condition has ended by the end of a first blanking time interval; and
if it is determined that the fault condition has not ended by the end of the first blanking time interval:
during the first time interval, measuring a time that is based on an external component that is coupled to a feedback pin;
storing a preset timer setting that is based on the measured time; and
during a second blanking time interval that follows the first blanking time interval, performing a charge cycle sequence such that a duration of the second blanking time interval is based on the preset timer setting, and wherein performing the charge cycle sequence includes:
determining whether the fault condition has ended during the second blanking time interval;
if the fault condition is determined to have ended during the second blanking time interval, controlling ending the second blanking time interval and restarting controlling regulation of an output voltage based on a feedback voltage at a feedback node; and
if the fault condition is determined not to have ended during the second blanking time interval, initiating a shutdown mode.

10. The method of claim 9 , further comprising:
during the first blanking time interval, controlling discharging of the feedback voltage to a first voltage level, wherein determining whether the fault condition has ended by an end of the first blanking time interval includes determining whether the feedback voltage reaches a second voltage level during the first blanking time interval after being discharged to the first voltage level;
after discharging the feedback voltage to the first voltage level during the first blanking time interval, controlling ending the first blanking time interval and restarting controlling regulation of the output voltage based on the feed

Assignees

• Infineon Technologies Austria Ag

Inventors

• Mao Mingping
• Gong Xiaowu

Classifications

• H02M3/33546 Primary

  with automatic control of the output voltage or current (H02M3/33561 takes precedence) · CPC title

• H02H3/0935 Primary

  the timing being determined by numerical means · CPC title

• H02M3/33507

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

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title