METHODS AND APPARATUS FOR POWER SUPPLY
Methods and apparatus for supplying a load according to various aspects of the present invention operate in conjunction with an output stage and a control system driving the output stage. The control system may include a PWM controller adapted to provide a drive signal to the output stage and an over-current protection circuit. The over-current protection circuit may sense an over-current condition at the load and truncate the drive signal in response to the over-current condition.
1 . A power supply for supplying a load, comprising:
an output stage; and
a control system driving the output stage, comprising:
a PWM controller adapted to provide a drive signal to the output stage; and
an over-current protection circuit adapted to:
sense an over-current condition at the load; and
truncate the drive signal in response to the over-current condition.
2 . A power supply according to claim 1 , wherein the control system comprises a comparator adapted to:
compare a reference signal to a load current signal; and
generate an over-current signal according to the comparison.
3 . A power supply according to claim 1 , wherein the over-current protection circuit is adapted to detect a rising edge of each cycle of the drive signal and truncate the drive signal after detection of the rising edge.
4 . A power supply according to claim 3 , wherein the over-current protection circuit is adapted to truncate the drive signal after detection of the rising edge and a selected blanking period.
5 . A power supply according to claim 4 , wherein the blanking period comprises an adjustable blanking period.
6 . A power supply according to claim I, wherein the over-current protection circuit is adapted to truncate the drive signal only for the duration of the over-current condition.
7 . A power supply according to claim 1 , wherein the over-current protection circuit is adapted to truncate the drive signal for the remaining duration of a drive signal pulse in which the over-current condition occurs.
8 . A power supply according to claim 1 , wherein the over-current protection circuit is adapted to selectively and independently truncate each individual pulse of the drive signal.
9 . A power supply for supplying a current to a load, comprising:
a PWM controller adapted to generate a PWM drive signal;
an output stage responsive to the PWM controller and adapted to supply the current to the load according to the drive signal;
a sensor adapted to determine the magnitude of the load current; and
an over-current protection circuit responsive to the sensor and adapted to selectively truncate the PWM drive signal in response to an over-current condition in the magnitude of the current.
10 . A power supply according to claim 9 , wherein the over-current protection circuit comprises a comparator adapted to:
compare a reference signal to the magnitude of the load current; and
generate an over-current signal according to the comparison.
11 . A power supply according to claim 9 , wherein the over-current protection circuit is adapted to detect a rising edge of each cycle of the PWM drive signal and truncate the PWM drive signal after detection of the rising edge.
12 . A power supply according to claim 11 , wherein the over-current protection circuit is adapted to truncate the drive signal after detection of the rising edge and a selected blanking period.
13 . A power supply according to claim 12 , wherein the blanking period comprises an adjustable blanking period.
14 . A power supply according to claim 9 , wherein the over-current protection circuit is adapted to truncate the drive signal only for the duration of the over-current condition.
15 . A power supply according to claim 9 , wherein the over-current protection circuit is adapted to truncate the drive signal for the remaining duration of a drive signal pulse in which the over-current condition occurs.
16 . A power supply according to claim 9 , wherein the over-current protection circuit is adapted to selectively and independently truncate each individual pulse of the drive signal.
17 . A method of supplying a current to a load, comprising:
supplying the current to the load according to a PWM drive signal;
sensing an over-current condition in the current at the load; and
selectively truncating the PWM drive signal according to the over-current condition.
18 . A method of supplying a current to a load according to claim 17 , wherein the sensing the over-current condition comprises:
comparing a reference signal to a load current signal; and
generating an over-current signal according to the comparison.
19 . A method of supplying a current to a load according to claim 17 , wherein selectively truncating the PWM drive signal comprises:
detecting a rising edge of each cycle of the PWM drive signal; and
truncating the drive signal after detecting the rising edge.
20 . A method of supplying a current to a load according to claim 19 , wherein selectively truncating the PWM drive signal comprises selectively truncating the drive signal after detecting the rising edge and a selected blanking period.
21 . A method of supplying a current to a load according to claim 20 , wherein the blanking period comprises an adjustable blanking period.
22 . A method of supplying a current to a load according to claim 17 , wherein selectively truncating the PWM drive signal comprises selectively truncating the drive signal only for the duration of the over-current condition.
23 . A method of supplying a current to a load according to claim 17 , wherein selectively truncating the PWM drive signal comprises selectively truncating the drive signal for the remaining duration of a drive signal pulse in which the over-current condition occurs.
24 . A method of supplying a current to a load according to claim 17 , wherein selectively truncating the PWM drive signal comprises selectively and independently truncating each individual pulse of the drive signal.