Under-voltage and over-voltage protection using a single comparator
An apparatus includes a pulsed-width modulation signal corresponding to a cutoff voltage, a periodic signal generation circuit, a comparator, and logic. The comparator is configured to compare a voltage input with an output of the periodic signal generation circuit and, based on a comparison of the voltage input with the output of the periodic signal generation circuit, generate another pulsed-width modulation signal. The logic is configured to compare the pulsed-width modulation signal and the other pulsed-width modulation signal to determine whether the voltage input has reached the cutoff voltage.
1. An apparatus, comprising:
a first pulsed-width modulation signal with a duty cycle, the duty cycle corresponding to a first cutoff voltage;
a periodic signal generation circuit;
a comparator configured to:
compare a voltage input with an output of the periodic signal generation circuit; and
based on a comparison of the voltage input with the output of the periodic signal generation circuit, generate a second pulsed-width modulation signal; and
logic configured to compare the first pulsed-width modulation signal and the second pulsed-width modulation signal to determine whether the voltage input has reached the first cutoff voltage.
2. The apparatus of claim 1 , wherein:
the periodic signal generation circuit is configured to generate a sawtooth signal;
an upper bound of the output of the signal generation circuit corresponds to an upper voltage limit for the voltage input; and
a lower bound of the output of the signal generation circuit corresponds to a lower voltage limit for the voltage input.
3. The apparatus of claim 1 , further comprising:
a third pulsed-width modulation signal corresponding to a second cutoff voltage; and
logic configured to compare the second pulsed-width modulation signal and the third pulsed-width modulation signal to determine whether the voltage input has reached the second cutoff voltage.
4. The apparatus of claim 3 , further comprising a single logic output representing whether the voltage input has reached the second cutoff voltage or the first cutoff voltage.
5. The apparatus of claim 1 , wherein the logic configured to compare the first pulsed-width modulation signal and the second pulsed-width modulation signal includes an AND operation with a first input of the first pulsed-width modulation signal and a second input of the second pulsed-width modulation signal.
6. The apparatus of claim 1 , wherein the first pulsed-width modulation signal is delayed to match the output of the comparator.
7. The apparatus of claim 1 , wherein logic configured to compare the first pulsed-width modulation signal and the second pulsed-width modulation signal is configured to provide a logic output to a shut-off of a switched-mode power supply output generator.
8. A method, comprising:
generating a first pulsed-width modulation signal with a duty cycle, the duty cycle corresponding to a first cutoff voltage;
comparing a voltage input with an output of a periodic signal generation circuit;
based on a comparison of the voltage input with the output of the periodic signal generation circuit, generating a second pulsed-width modulation signal; and
comparing the first pulsed-width modulation signal and the second pulsed-width modulation signal to determine whether the voltage input has reached the first cutoff voltage.
9. The method of claim 8 , wherein:
the output of the periodic signal generation circuit is a sawtooth signal;
an upper bound of the output of the signal generation circuit corresponds to an upper voltage limit for the voltage input; and
a lower bound of the output of the signal generation circuit corresponds to a lower voltage limit for the voltage input.
10. The method of claim 8 , further comprising:
generating a third pulsed-width modulation signal corresponding to a second cutoff voltage; and
comparing the second pulsed-width modulation signal and the third pulsed-width modulation signal to determine whether the voltage input has reached the second cutoff voltage.
11. The method of claim 10 , further comprising representing in a single logic output whether the voltage input has reached the second cutoff voltage or the first cutoff voltage.
12. The method of claim 8 , further comprising comparing the first pulsed-width modulation signal and the second pulsed-width modulation signal using an AND operation with a first input of the first pulsed-width modulation signal and a second input of the second pulsed-width modulation signal.
13. The method of claim 8 , further comprising delaying the first pulsed-width modulation signal to match the output of the comparator.
14. The method of claim 8 , wherein comparing the first pulsed-width modulation signal and the second pulsed-width modulation signal includes providing a logic output to a shut-off of a switched-mode power supply output generator.
15. A microcontroller, comprising:
a first pulsed-width modulation generator configured to generate a first pulsed-width modulation signal with a duty cycle, the duty cycle corresponding to a first cutoff voltage;
a periodic signal generation circuit;
a comparator configured to:
compare a voltage input with an output of the periodic signal generation circuit; and
based on a comparison of the voltage input with the output of the periodic signal generation circuit, generate a second pulsed-width modulation signal; and
logic configured to compare the first pulsed-width modulation signal and the second pulsed-width modulation signal to determine whether the voltage input has reached the first cutoff voltage.
16. The microcontroller of claim 15 , wherein:
the periodic signal generation circuit is configured to generate a sawtooth signal;
an upper bound of the output of the signal generation circuit corresponds to an upper voltage limit for the voltage input; and
a lower bound of the output of the signal generation circuit corresponds to a lower voltage limit for the voltage input.
17. The microcontroller of claim 15 , further comprising:
a third pulsed-width modulation generator configured to generate a third pulsed-width modulation signal corresponding to a second cutoff voltage; and
logic configured to compare the second pulsed-width modulation signal and the third pulsed-width modulation signal to determine whether the voltage input has reached the second cutoff voltage.
18. The microcontroller of claim 17 , further comprising a single logic output representing whether the voltage input has reached the second cutoff voltage or the first cutoff voltage.
19. The microcontroller of claim 15 , wherein the logic configured to compare the first pulsed-width modulation signal and the second pulsed-width modulation signal includes an AND operation with a first input of the first pulsed-width modulation signal and a second input of the second pulsed-width modulation signal.
20. The microcontroller of claim 15 , wherein logic configured to compare the first pulsed-width modulation signal and the second pulsed-width modulation signal is configured to provide a logic output to a shut-off of a switched-mode power supply output generator.