Power Converter Discharge Control Circuit
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Solution Overview
Problem
The existing power converter systems for hybrid electric vehicles, plug-in hybrid electric vehicles, and electric vehicles face challenges in efficiently discharging smoothing capacitors without causing excessive heat generation in discharge resistors, leading to increased energy consumption and potential resistor burnout.
Innovation Solution
The power converter incorporates a voltage measurement circuit, a voltage-dividing circuit, and a control circuit that manage the discharge of smoothing capacitors by determining the optimal duration of discharge periods based on measured voltages, optimizing the discharge process to prevent excessive heat generation and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the discharge circuit discharges the smoothing capacitor for a long time, then the capacitor is fully discharged, but the discharge resistor generates excessive heat and may burn out
Solution Approach 1:
The discharge control circuit performs periodic discharge operations with multiple discharge cycles. Each cycle discharges the capacitor for a predetermined time, then pauses to allow the resistor to cool down. This periodic action pattern (discharge-pause-discharge) continues until the capacitor voltage reaches the discharge threshold, solving both the completeness and overheating issues.
Solution Approach 2:
Before performing the main discharge operation, the control circuit first measures the capacitor voltage and determines the number of discharge cycles needed. This preliminary assessment allows the system to plan the discharge strategy in advance, preventing excessive heat generation by calculating the appropriate discharge duration and pause intervals.
2Loss of time
If the discharge circuit discharges the smoothing capacitor for a short time to check contactor status, then the check is quick, but repeated short discharges increase energy consumption
Solution Approach 1:
The control circuit measures the capacitor voltage before and after each discharge operation to determine whether the contactor is in the on or off state. This feedback mechanism allows the system to make intelligent decisions about subsequent discharge operations, avoiding unnecessary repeated discharges and reducing energy consumption while maintaining quick detection capability.
3Speed
If the control circuit turns on the discharge switching device before the contactor is turned off, then the discharge operation starts immediately, but the high-voltage battery continues to supply current and the capacitor is not discharged
Solution Approach 1:
The control circuit performs a preliminary check by attempting to discharge the capacitor and measuring the voltage change. If the voltage does not decrease as expected (indicating the contactor is still on), the control circuit waits and retries the discharge operation after a predetermined time. This preliminary test approach ensures discharge effectiveness while maintaining responsive operation once the contactor is properly off.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach optimizes the discharge process, reducing energy consumption and preventing resistor overheating, allowing for the use of smaller, less costly discharge resistors and minimizing the size and cost of the inverter apparatus.
Implementation Method 1
the discharge circuit includes a discharge resistor and a switching device connected to each other in series and is connected in parallel to the smoothing capacitor
Data Source
AI summary
A power converter includes an inverter, a contactor for connecting a battery to the inverter in order to supply DC power from the battery to the inverter and for disconnecting the battery from the inverter in order to stop an operation to supply the DC power from the battery to the inverter, a smoothing capacitor connected in parallel to the battery through the contactor, a discharge circuit that is provided with a discharge resistor and a switching device connected in series to the discharge resistor and is connected in parallel to the smoothing capacitor to discharge electric charge from the smoothing capacitor, a voltage measurement circuit, a voltage-dividing circuit for dividing the voltage across the terminals of the smoothing capacitor to generate a partial voltage to be input to the voltage measurement circuit and a control circuit of the switching device.