Power module protection at start-up
View Patent ↗A power conversion unit includes a power converter and a controller coupled to the secondary or output stage of the power converter. The power conversion unit is configured to generate an output test voltage or current during a pre-start test period of the power converter, where the output test voltage or current is monitored to determine a converter fault condition. A method of operating a power conversion unit is also included.
1. A power conversion unit comprising:
a power converter having a primary stage and a secondary stage, the primary stage including a pulse width modulated (PWM) circuit;
an isolation barrier separating the primary stage from the secondary stage such that primary stage information is unavailable to the secondary stage; and
a voltage controller located in the secondary stage and configured to test the power converter and a load coupled to the power converter for a fault condition by driving the PWM circuit to produce an output test voltage at the secondary stage during a pre-start test period of the power converter; wherein the output test voltage beyond a predetermined threshold value is indicative of a fault condition.
2. The power conversion unit as recited in claim 1 wherein the output test voltage corresponds to one of a low duty cycle PWM signal and a variable frequency signal.
3. The power conversion unit as recited in claim 1 wherein the pre-start test period corresponds to one selected from the group consisting of:
a fixed length of time;
a variable length of time;
a fixed amplitude voltage during the pre-start test period; and
a variable amplitude voltage during the pre-start test period.
4. The power conversion unit as recited in claim 1 wherein the fault condition corresponds to one selected from the group consisting of:
an output capacitor fault;
an output load fault;
a temperature fault; and
a current fault.
5. The power conversion unit as recited in claim 1 , wherein the voltage controller is in an ON state during an ENABLE period, and the power converter is in an OFF state during the ENABLE period; and wherein the ENABLE period precedes the pre-start test period.
6. The power conversion unit as recited in claim 1 further comprising a current controller coupled to the secondary stage and operative to limit a secondary stage output current during the pre-start test period.
7. The power conversion unit as recited in claim 6 wherein the secondary stage output current is an initial surge current.
8. The power conversion unit as recited in claim 6 wherein the secondary stage output current corresponds to one of an output capacitor fault and an output load fault.
9. A method of operating a power conversion unit having a power converter with primary and secondary stages, the method comprising:
isolating the primary stage from the secondary stage using an isolation barrier such that primary stage information is unavailable to the secondary stage;
testing the power converter and a load coupled to the power converter for a fault condition by monitoring an output test voltage using a voltage controller at the secondary stage during a pre-start test period;
controlling a PWM circuit in the power converter to yield the output test voltage during the pre-start test period; and
determining a fault condition of the power converter based on the output test voltage.
10. The method of claim 9 wherein isolating the primary stage from the secondary stage further comprises isolating the primary stage from the secondary stage with a galvanic isolator.
11. The method as recited in claim 9 wherein the output test voltage corresponds to a low duty cycle PWM signal.
12. The method as recited in claim 9 wherein the fault condition corresponds to one selected from the group consisting of:
an output capacitor fault;
an output load fault;
a temperature fault; and
a current fault.
13. The method as recited in claim 9 further comprising operating a controller during an ENABLE period; and monitoring an output of the secondary stage with the controller while the power converter is in an OFF state.
14. The method as recited in claim 9 further comprising limiting a secondary stage output current during the fault condition.
15. The method as recited in claim 9 wherein the secondary stage output current is an initial surge current.
16. The method as recited in claim 14 wherein a surge in the secondary stage output current corresponds to one of an output capacitor fault and an output load fault.
17. The method as recited in claim 12 wherein the output capacitor fault corresponds to an output capacitor impedance short.
18. A power conversion unit comprising:
a power converter having an input stage and an output stage;
an isolation barrier separating the input stage from the output stage such that input stage information is unavailable to the output stage;
a controller located in the output stage and driving the power converter; and
the power converter operative to test the power converter and a load coupled to the power converter for a fault condition by producing an output test current at the output stage during a pre-start test period, wherein a value of the output test current is indicative of a fault condition.
19. The power conversion unit as recited in claim 18 wherein the isolation barrier further comprises a galvanic isolation between the input stage and the output stage.