Input power protection
In one general aspect, an apparatus can include an input terminal, an output terminal and a ground terminal. The apparatus can also include an overcurrent protection device coupled between the input terminal and the output terminal. The apparatus can further include a thermal shunt device coupled between the output terminal and the ground terminal, the thermal shunt device being configured to, at a threshold temperature, operate in a thermally-induced low-impedance state.
1. An apparatus, comprising:
an input terminal;
an output terminal;
a ground terminal;
an overcurrent protection device coupled between the input terminal and the output terminal; and
a thermal shunt coupled between the output terminal and the ground terminal, the thermal shunt including:
a shunt device; and
a thermally-activated current sink coupled in parallel with the shunt device, the thermally activated current sink being thermally coupled with the overcurrent protection device in a positive thermal-feedback loop,
the thermal shunt being configured to, at a threshold temperature and in response to thermal feedback in the positive thermal-feedback loop, operate in a thermally-induced low-impedance state.
2. The apparatus of claim 1 , wherein the overcurrent protection device is configured to change from a high conduction state to a low conduction state as a result of the thermal shunt operating in the thermally-induced low-impedance state.
3. The apparatus of claim 1 , wherein the thermally-activated current sink includes a p-type Schottky diode.
4. The apparatus of claim 1 , wherein the thermally-activated current sink includes an n-type Schottky diode.
5. The apparatus of claim 1 , wherein the overcurrent protection device includes a fuse device configured to blow open as a result of the thermal shunt operating in the thermally-induced low-impedance state.
6. The apparatus of claim 1 , wherein the overcurrent protection device is configured to change from a high conduction state to a low conduction state as a result of at least one of:
heat generated by the thermal shunt; and
current pulled through the overcurrent protection device as a result of the thermal shunt operating in the thermally-induced low-impedance state.
7. The apparatus of claim 1 , wherein the thermal shunt is configured to operate in the thermally-induced low-impedance state in response to heat that is generated as a result of power dissipated in the overcurrent protection device.
8. The apparatus of claim 1 , wherein the thermal shunt is configured to operate in the thermally-induced low-impedance state in response to heat transferred from a printed circuit board on which the apparatus is included.
9. The apparatus of claim 1 , further comprising a plurality of thermal shunts coupled in parallel with one another, each of the plurality of thermal shunts being coupled between the output terminal and the ground terminal, the plurality of thermal shunts being spatially distributed across a printed circuit board.
10. The apparatus of claim 1 , wherein the overcurrent protection device and the thermally-activated current sink are implemented in a common silicon substrate.
11. An apparatus, comprising:
an input terminal;
an output terminal;
a ground terminal;
an overvoltage protection device coupled between the output terminal and the ground terminal; and
a thermally-activated current sink coupled between the output terminal and the ground terminal, in parallel with the overvoltage protection device; and
an overcurrent protection device coupled between the input terminal and the output terminal, the overcurrent protection device being thermally coupled with the thermally-activated current sink in a positive thermal-feedback loop, such that heat produced by the overcurrent protection device at a current below a rated current of the over current protection device causes at least one of the overvoltage protection device and the thermally-activated current sink to change from a high impedance state to a low impedance state as a result of positive thermal feedback in the positive thermal-feedback loop.
12. The apparatus of claim 11 , wherein the thermally-activated current sink changing to the low impedance state occurs as a result of positive thermal feedback between the overcurrent protection device, the overvoltage protection device and the thermally-activated current sink.
13. The apparatus of claim 11 , wherein the overvoltage protection device changing to the low impedance state occurs as a result of positive thermal feedback between the overcurrent protection device, the thermally-activated current sink and the overvoltage protection device.
14. The apparatus of claim 11 , wherein the thermally-activated current sink includes a cobalt-silicide (CoSi) p-type Schottky diode.
15. The apparatus of claim 11 , wherein the thermally-activated current sink includes one of an n-type Schottky diode, a polysilicon resistor with a negative thermal coefficient and a polysilicon diode.
16. The apparatus of claim 11 , wherein the thermally-activated current sink, the overvoltage protection device and the overcurrent protection device are implemented in a common silicon substrate such that a positive thermal feedback loop is formed between the overcurrent protection device, the thermally-activated current sink and the overvoltage protection device.
17. The apparatus of claim 11 , wherein the overcurrent protection device is configured to change from a high conduction state to a low conduction state as a result of the thermally-activated current sink or the overvoltage protection device changing to the low impedance state.
18. The apparatus of claim 11 , wherein the overvoltage protection device includes a Zener diode or a transient-voltage-suppression diode.
19. The apparatus of claim 11 , wherein the thermally-activated current sink changing to the low impedance state occurs as a result of a thermal shunt device included in the thermally-activated current sink initiating thermal runaway.
20. The apparatus of claim 11 , wherein the overcurrent protection device comprises a fuse configured to blow open as a result of the thermally-activated current sink or the overvoltage protection device changing to the low impedance state.
21. An apparatus, comprising:
an overvoltage protection portion, the overvoltage protection portion including:
a thermally-activated current sink; and
a shunt device coupled in parallel with the thermally activate current sink; and
an overcurrent protection portion thermally coupled with the thermally activated current sink in a positive thermal-feedback loop such that:
positive thermal feedback between the overcurrent protection portion and the thermally activated current sink in the positive thermal-feedback loop causes the overvoltage protection portion to change from a voltage regulation state to a thermally-induced conduction state, and
the overvoltage protection portion changing from the voltage regulation state to the thermally-induced conduction state causes the overcurrent protection portion to change from a current conduction state to a current blocking state.
22. The apparatus of claim 21 , wherein the thermally-induced conduction state is a thermal thermal-runaway state.
23. The apparatus of claim 21 , wherein the thermally-activated current sink includes a p-type Schottky diode.
24. The apparatus of claim 21 , wherein the overcurrent protection portion further includes:
a sensor operably coupled with the overvoltage portion, the sensor being configured to detect the overvoltage protection portion changing from the voltage regulation state to the thermally-induced conduction state; and
a current switch operably coupled with the sensor, the current switch being configured to change from the current conduction state to the current blocking state in response to the sensor detecting the overvoltage protection portion changing from the voltage regulation state to the thermally-induced conduction state.