Power circuit with overvoltage protection
View Patent ↗Power circuitry is disclosed for protecting an electronic device during an overvoltage event. A voltage clamp is connected in parallel with a charge pump, wherein the voltage clamp limits an input voltage of the charge pump. A current limiting resistor couples a supply voltage to the voltage clamp and to the charge pump. A power transistor couples the supply voltage to a load, wherein a gate of the power transistor is controlled by an output of the charge pump during a power-on operation. When the supply voltage exceeds a threshold thereby activating the voltage clamp, the current limiting resistor limits a current flowing through the voltage clamp.
1. Power circuitry for protecting an electronic device during an overvoltage event, the power circuitry comprising:
a voltage clamp in parallel with a charge pump, wherein the voltage clamp limits an input voltage of the charge pump;
a current limiting resistor coupling a supply voltage to the voltage clamp and to the charge pump;
a power transistor configured to couple the supply voltage to a load, wherein
when the supply voltage exceeds a threshold thereby activating the voltage clamp, the current limiting resistor limits a current flowing through the voltage clamp; and
control circuitry responsive to an output of the charge pump and configured to ramp a control voltage applied to a gate of the power transistor during a power-on operation.
2. The power circuitry as recited in claim 1 , wherein the load comprises a voltage regulator.
3. The power circuitry as recited in claim 2 , wherein after the power transistor at least partially turns on during the power-on operation, the voltage regulator generates a regulated voltage configured to power the charge pump.
4. The power circuitry as recited in claim 3 , wherein the charge pump further turns on the power transistor in response to the regulated voltage.
5. The power circuitry as recited in claim 1 , wherein the control circuitry is further configured to control the gate of the power transistor to limit a maximum voltage applied to the load when the supply voltage exceeds the threshold.
6. The power circuitry as recited in claim 5 , wherein when the supply voltage exceeds the threshold for a first interval, the control circuitry is further configured to control the gate of the power transistor to substantially turn off the power transistor.
7. The power circuitry as recited in claim 6 , wherein the gate of the power transistor is controlled to at least partially turn on the power transistor after a second interval following the first interval.
8. The power circuitry as recited in claim 7 , wherein the control circuitry is further configured to control the gate of the power transistor independent of the charge pump to at least partially turn on the power transistor after the second interval following the first interval.
9. The power circuitry as recited in claim 7 , wherein the gate of the power transistor is controlled using the output of the charge pump to at least partially turn on the power transistor after the second interval following the first interval.
10. A method of protecting an electronic device during an overvoltage event, the method comprising:
limiting an input voltage of a charge pump using a voltage clamp;
ramping a control voltage applied to a gate of a power transistor using an output of the charge pump during a power-on operation, wherein the power transistor applies a supply voltage to a load; and
when the supply voltage exceeds a threshold thereby activating the voltage clamp, limiting a current flowing through the voltage clamp.
11. The method as recited in claim 10 , wherein the load comprises a voltage regulator.
12. The method as recited in claim 11 , wherein after the power transistor at least partially turns on during the power-on operation, the voltage regulator generates a regulated voltage configured to power the charge pump.
13. The method as recited in claim 12 , wherein the charge pump further turns on the power transistor in response to the regulated voltage.
14. The method as recited in claim 10 , further comprising controlling the gate of the power transistor to limit a maximum voltage applied to the load when the supply voltage exceeds the threshold.
15. The method as recited in claim 14 , wherein when the supply voltage exceeds the threshold for a first interval, further comprising controlling the gate of the power transistor to substantially turn off the power transistor.
16. The method as recited in claim 15 , further comprising controlling the gate of the power transistor to at least partially turn on the power transistor after a second interval following the first interval.
17. The method as recited in claim 16 , further comprising controlling the gate of the power transistor independent of the charge pump to at least partially turn on the power transistor after the second interval following the first interval.
18. The method as recited in claim 16 , further comprising controlling the gate of the power transistor using the output of the charge pump to at least partially turn on the power transistor after the second interval following the first interval.
19. Power circuitry for protecting an electronic device during an overvoltage event, the power circuitry comprising:
a voltage clamp in parallel with a charge pump, wherein the voltage clamp limits an input voltage of the charge pump;
a current limiting resistor coupling a supply voltage to the voltage clamp and to the charge pump; and
a power transistor configured to couple the supply voltage to a load comprising a voltage regulator, wherein:
a gate of the power transistor is controlled by an output of the charge pump during a power-on operation;
when the supply voltage exceeds a threshold thereby activating the voltage clamp, the current limiting resistor limits a current flowing through the voltage clamp; and
after the power transistor at least partially turns on during the power-on operation, the voltage regulator generates a regulated voltage configured to power the charge pump.
20. The power circuitry as recited in claim 19 , wherein the charge pump further turns on the power transistor in response to the regulated voltage.
21. Power circuitry for protecting an electronic device during an overvoltage event, the power circuitry comprising:
a voltage clamp in parallel with a charge pump, wherein the voltage clamp limits an input voltage of the charge pump;
a current limiting resistor coupling a supply voltage to the voltage clamp and to the charge pump;
a power transistor configured to couple the supply voltage to a load; and
control circuitry configured to control a gate of the power transistor to limit a maximum voltage applied to the load when the supply voltage exceeds a threshold;
wherein:
the gate of the power transistor is controlled by an output of the charge pump during a power-on operation;
when the supply voltage exceeds the threshold thereby activating the voltage clamp, the current limiting resistor limits a current flowing through the voltage clamp; and
when the supply voltage exceeds the threshold for a first interval, the control circuitry is further configured to control the gate of the power transistor to substantially turn off the power transistor.
22. The power circuitry as recited in claim 21 , wherein the gate of the power transistor is controlled to at least partially turn on the power transistor after a second interval following the first interval.
23. The power circuitry as recited in claim 22 , wherein the control circuitry is further configured to control the gate of the power transistor independent of the charge pump to at least partially turn on the power transistor after the second interval following the first interval.
24. The power circuitry as recited in claim 22 , wherein the gate of the power transistor is controlled using the output of the charge pump to at least partially turn on the power transistor after the second interval following the first interval.
25. A method of protecting an electronic device during an overvoltage event, the method comprising:
limiting an input voltage of a charge pump using a voltage clamp;
controlling a gate of a power transistor using an output of the charge pump during a power-on operation, wherein the power transistor applies a supply voltage to a load comprising a voltage regulator; and
when the supply voltage exceeds a threshold thereby activating the voltage clamp, limiting a current flowing through the voltage clamp;
wherein after the power transistor at least partially turns on during the power-on operation, the voltage regulator generates a regulated voltage configured to power the charge pump.
26. The method as recited in claim 25 , wherein the charge pump further turns on the power transistor in response to the regulated voltage.
27. A method of protecting an electronic device during an overvoltage event, the method comprising:
limiting an input voltage of a charge pump using a voltage clamp;
controlling a gate of a power transistor using an output of the charge pump during a power-on operation, wherein the power transistor applies a supply voltage to a load;
when the supply voltage exceeds a threshold thereby activating the voltage clamp, limiting a current flowing through the voltage clamp;
controlling the gate of the power transistor to limit a maximum voltage applied to the load when the supply voltage exceeds the threshold; and
when the supply voltage exceeds the threshold for a first interval, controlling the gate of the power transistor to substantially turn off the power transistor.
28. The method as recited in claim 27 , further comprising controlling the gate of the power transistor to at least partially turn on the power transistor after a second interval following the first interval.
29. The method as recited in claim 28 , further comprising controlling the gate of the power transistor independent of the charge pump to at least partially turn on the power transistor after the second interval following the first interval.
30. The method as recited in claim 28 , further comprising controlling the gate of the power transistor using the output of the charge pump to at least partially turn on the power transistor after the second interval following the first interval.