| Jira Legacy | ||||||
|---|---|---|---|---|---|---|
|
Relevant page on testing MSXII: Precharge Revisions
Initial board validation:
...
Normally precharge will be enabled through a firmware signal from the MCU to the enable pin on the load switch U3. If the firmware is unavailable, this can be powered by connecting a 3V3 source to the connector P1 and the enable pin (pin 2). Whenever the enable pin receives power, the isolated side of the board turns on and precharge starts. Before enabling precharge, set up the oscilloscope to read voltage output. There are multiple points of interest to be measured over the duration of precharging and discharging. To precharge and discharge the capacitors, supply and stop supplying the 3V3 to the enable pin on the load switch. With the 3 x 1 kohm resistance for precharge and 1 x 5 kohm resistance for discharge, allow 3s for the capacitor to precharge and 5s for discharge each test.
In place of the 150V supplied by the battery, another 12V source (or any lower voltage source) can be used to connect to the HV line. The precharge functions should be tested with a lower voltage first, remember to recalculate the voltage division values to see when precharge stops.
Test points:
The first point to test is the capacitor itself. Enable precharge and measure of the change in voltage over the duration of the capacitor's charge. It should follow the expected curve of voltage in an RC circuit. Now unpower the enable pin and check the discharge normally.
Next point to test is the voltage on the capacitor side of the precharge and make sure the circuit and at the IN+ pin of the comparator alongside the comparator output test point. When using 12V in place of the 150V, the voltage at the IN- should be 0.75V. Then the voltage on the capacitor side should be around 11.45V when IN+ exceeds IN-. Check that the capacitor stops precharging when the voltage on the capacitor side indeed reaches around 11.45V and the IN+ pin reaches 0.75V.
Repeat this test, except instead of checking the voltage on the capacitor, measure the test points COMP_OUT, AND_OUT, ISO_LATCH_OUT, and LATCH_OUT. The latter 3 should all be logic low to start and only send a 12V signal only when the condition above is met. COMP_OUT will probably output a logic high when both pins are unpowered at the start. Note the times taken for each output to reach logic high. Also check the behaviour of LATCH_OUT to ensure it doesn't oscillate during the transition from logic high to logic low.
CAN tests:
Thermistor tests:
Fans: