# PDOC Test Report

## Test Date
* 2024/11/25, William

## Purpose

This document outlines the test methods and results to verify the effectiveness of our PDOC system. The system is designed to open the shutdown loop when over-temperature conditions occur on the precharge or discharge resistor. Additionally, the report includes explanations of several circuit operations.

## Related Rule

* EV5.6.6 Add Clause defining the PDOC (Local Addendum)

## PDOC Test Method

In order to **simulate the worst-case scenario** for the system, we directly connect a 400V DC voltage source (approximately the maximum voltage of the accumulator) to each terminal of our discharge and precharge resistors. **Using a thermal camera, we can verify whether the system successfully triggers the shutdown loop to open at the designed temperature.** Additionally, it allows us to assess the thermal conductivity of the resistors, heat sink, and thermal paste to ensure effective heat dissipation.


<img src="https://hackmd.io/_uploads/H1uAbvQXJg.jpg" width="60%"/>

## PDOC Test Result

**The temperature for triggering the shutdown loop is designed to be 80°C.** However, due to the thermal conductivity limitations of the heatsink and thermal paste, it takes some time for the NTC thermistor to respond. **In the worst-case scenario, the system may only trip when the resistor's surface temperature reaches 90°C. This is still within safe limits,** as the resistor's operating temperature range, according to the datasheet, is -65°C to +175°C.

<img src="https://hackmd.io/_uploads/r1tB5PXXJx.png" width="50%"/>



<img src="https://hackmd.io/_uploads/SkOFuwX71l.png" width="44%"/>

## Core System Explanation

### How to Detect The Temperature

In our system, we use an NTC thermistor (Littelfuse KX103J2) with a Beta value of 3892. The Beta value is a critical characteristic that determines the thermistor's resistance at specific temperatures. When paired with a resistor, it forms a voltage divider, which outputs varying voltages corresponding to different temperatures. The following graph illustrates the relationship between temperature and resistance.

<img src="https://hackmd.io/_uploads/rJcpTvXXJg.png" width="70%"/>

To monitor the temperature, a hysteresis OPA comparator is used to determine whether the temperature exceeds 80°C based on the voltage. Additionally, the hysteresis OPA comparator ensures system stability by introducing a hysteresis effect. Once the over-temperature protection is triggered, it will only disengage when the temperature drops back to 70°C, preventing rapid on/off switching and ensuring reliable operation.

<img src="https://hackmd.io/_uploads/S1WLpvmXJx.png" width="70%"/>