Power supply methods and apparatus
A detection circuit includes a first power line, a first signal conditioning module operationally coupled to the first power line, a neutral line (N) operationally coupled to the first signal conditioning module, a second signal conditioning module operationally coupled to the first power line, a second power line operationally coupled to the second signal conditioning module, and an analog to digital (A/D) converter operationally coupled to the first and the second signal conditioning modules.
1. A method for detecting at least one of a mis-wire and a neutral fault in an oven, said method comprising:
connecting a load resistor between a first power line and a neutral line;
comparing an alternating current (AC) voltage between the first power line and the neutral line to a first reference voltage range, wherein at least one load is connected via a relay between the first power line and the neutral line; and
comparing an AC voltage between the first power line and a second power line to a second voltage range.
2. A method in accordance with claim 1 wherein said comparing a voltage between a first power line and a neutral line to a first reference voltage range comprises:
connecting the first power line and the neutral line to a signal conditioning module that outputs a direct current voltage proportional to the AC voltage between the first power line and the neutral line; and
connecting an analog to digital (A/D) converter to the signal conditioning module, wherein the A/D converter outputs a digital representation of the direct current voltage.
3. A method in accordance with claim 2 further comprising:
connecting a controller to the A/D converter;
receiving at the controller from the A/D converter the digital representation of the voltage between the first power line and an N line; and
comparing the received digital representation with a range stored in a memory of the controller.
4. A method in accordance with claim 3 further comprising connecting a resistor between the second power line and the neutral line.
5. A method in accordance with claim 3 further comprising providing an indication when the received digital representation in not within the range.
6. A method in accordance with claim 5 wherein said providing an indication comprises providing a visual indication.
7. A method in accordance with claim 3 further comprising controlling the relay based upon whether the received digital representation in within the range.
8. A method in accordance with claim 1 further comprising sizing the load resistor to draw a current greater than a leakage path current when the neutral line is disconnected.