Power controller with short-circuited protection and method of controlling the same
A power controller with short-circuit protection is disclosed to control a power switch, which is connected in series with a current-sense resistor and an inductive device between two power lines. The current-sense resistor provides a current-sense signal. The power controller includes a PWM signal generator and a short-circuit protection circuit. The PWM signal generator generates a PWM signal to the power switch to create switching cycles, each consisting of an ON time and an OFF time. The short-circuit protection circuit has a high-pass filter and a condition detector. The high-pass filter high-pass filters the current-sense signal to provide a filtered signal to the condition detector, which determines whether the filtered signal fits a predetermined condition during the ON time to generate a short-circuit protection signal and to prevent the power switch being turned on.
1. A power controller configured to control a power switch, the power switch, a current sense resistor, and an inductive component connected between two power lines in series, the current sense resistor configured to provide a current sense signal, the power controller comprising:
a PWM signal generator configured to generate a PWM signal to the power switch to generate a plurality of switch cycles having a first switch cycle, and the first switch cycle having a turned-on time and a turned-off time, and
a short-circuited protection circuit configured to receive the current sense signal, the short-circuited protection circuit comprising:
a high-pass filter configured to filter the current sense signal in a high-pass manner to generate a filtered signal, and
a state detection circuit configured to detect the filtered signal,
wherein when the filtered signal is less than a predetermined voltage within the turned-on time, the state detection circuit provides a short-circuited protection signal to disable the PWM signal generator to prevent the power switch being turned on.
2. The power controller as claimed in claim 1 , wherein the short-circuited protection circuit further comprises:
a clamp circuit configured to set the filtered signal to a starting value at the beginning of the turned-on time.
3. The power controller as claimed in claim 2 , wherein the PWM signal generator comprises:
a leading-edge blanking signal generator configured to define a leading-edge blanking time at the beginning of the turned-on time; the clamp circuit configured to set the filtered signal to a start value within the leading-edge blanking time.
4. The power controller as claimed in claim 3 , wherein the PWM signal generator is configured to determine the turned-on time according to the current sense signal, and the turned-on time is at least the leading-edge blanking time.
5. The power controller as claimed in claim 3 , wherein the state detection circuit comprises:
a comparator configured to compare the filtered signal with a predetermined voltage to generate a risk signal.
6. The power controller as claimed in claim 5 , wherein the starting value of the filtered signal is less than the predetermined voltage so that the risk signal is at a first level within the leading-edge blanking time.
7. The power controller as claimed in claim 6 , wherein the state detection circuit is configured to check the risk signal at a predetermined time point after the leading-edge blanking time to determine whether to generate the short-circuited protection signal.
8. The power controller as claimed in claim 7 , wherein at the predetermined time point, when the filtered signal is greater than the predetermined voltage, the risk signal is not the first level, and the state detection circuit does not generate the short-circuited protection signal; when the filtered signal is less than the predetermined voltage, the risk signal is the first level, and the state detection circuit generates the short-circuited protection signal.
9. A control method applied to a power controller to control a power switch, the power switch, a current sense resistor, and an inductive component connected between two power lines in series, the current sense resistor configured to provide a current sense signal, the control method comprising steps of:
alternatively turning on and turning off the power switch to generate a plurality of switch cycles having a first switch cycle, the first switch cycle having a turned-on time and a turned-off time,
filtering the current sense signal in a high-pass manner within the turned-on time to generate a filtered signal, and
providing a short-circuited protection signal to prevent the power switch being turned on when the filtered signal is less than a predetermined voltage within the turned-on time.
10. The control method as claimed in claim 9 , further comprising steps of:
defining a leading-edge blanking time at the beginning of the turned-on time, the turned-on time at least equal to the leading-edge blanking time, and
setting the filtered signal to a start value within the leading-edge blanking time.
11. The control method as claimed in claim 10 , further comprising steps of:
comparing the filtered signal and a predetermined voltage to generate a risk signal, and
checking the risk signal at a predetermined time point after the leading-edge blanking time to determine whether to generate the short-circuited protection signal.
12. The control method as claimed in claim 11 , further comprising steps of:
making the risk signal be a first level when the start value set in the leading-edge blanking time is less than the predetermined voltage,
making the risk signal different from the first level when the filtered signal is greater than the predetermined voltage at the predetermined time point, so that the short-circuited protection signal is not generated, and
making the risk signal be still the first level when the filtered signal is less than the predetermined voltage at the predetermined time point, so that the short-circuited protection signal is generated.
13. A power controller configured to control a power switch, the power switch, a current sense resistor, and an inductive component connected between two power lines in series, the current sense resistor configured to provide a current sense signal, the power controller comprising:
a PWM signal generator configured to generate a PWM signal to the power switch to generate a plurality of switch cycles having a first switch cycle, and the first switch cycle having a turned-on time and a turned-off time, and
a short-circuited protection circuit configured to receive the current sense signal, the short-circuited protection circuit comprising:
a high-pass filter configured to filter the current sense signal in a high-pass manner to generate a filtered signal, and
a state detection circuit configured to detect the filtered signal,
wherein when the filtered signal meets a predetermined condition that the current sense resistor is short-circuited within the turned-on time, the state detection circuit provides a short-circuited protection signal to disable the PWM signal generator to prevent the power switch being turned on.
14. The power controller as claimed in claim 13 , wherein the short-circuited protection circuit further comprises:
a clamp circuit configured to set the filtered signal to a starting value at the beginning of the turned-on time.
15. The power controller as claimed in claim 14 , wherein the PWM signal generator comprises:
a leading-edge blanking signal generator configured to define a leading-edge blanking time at the beginning of the turned-on time; the clamp circuit configured to set the filtered signal to a start value within the leading-edge blanking time.
16. The power controller as claimed in claim 14 , wherein the state detection circuit comprises:
a comparator configured to compare the filtered signal with a predetermined voltage to generate a risk signal; the starting value of the filtered signal is less than the predetermined voltage so that the risk signal is at a first level within the leading-edge blanking time.
17. The power controller as claimed in claim 16 , wherein the state detection circuit is configured to check the risk signal at a predetermined time point after the leading-edge blanking time to determine whether to generate the short-circuited protection signal.