DC Power Supply Discharge Circuit with Voltage Monitoring Control
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Solution Overview
Problem
In inverter systems for hybrid automobiles, if the contactor inadvertently turns ON during capacitor discharge, it can cause a prolonged high current flow in the discharge circuit, leading to inefficiencies and potential damage.
Innovation Solution
A discharge circuit for a DC power supply smoothing capacitor that includes a resistor, a switch, and a control circuit. The control circuit measures the terminal voltage and controls the switch to stop discharge when the voltage exceeds a predetermined characteristic, preventing continuous current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contactor turns ON during capacitor discharge, then the capacitor can be charged from the battery, but prolonged high current flow occurs in the discharge circuit causing energy waste and potential damage
Solution Approach 1:
The control circuit continuously monitors the capacitor terminal voltage during discharge and compares it against a predetermined voltage decrease characteristic. When the voltage exceeds this characteristic (indicating contactor ON state), the control circuit automatically interrupts the discharge circuit. This feedback mechanism resolves the contradiction by detecting the harmful condition and automatically correcting it to prevent both energy waste and circuit damage.
Solution Approach 2:
The control circuit acts as an intermediary between the discharge circuit and the voltage monitoring system. It receives voltage information, processes it against the predetermined characteristic, and controls the discharge switching element accordingly. This intermediary function enables intelligent decision-making to prevent prolonged current flow while maintaining discharge capability when needed.
2Reliability
If the discharge circuit operates continuously to ensure complete capacitor discharge, then safety is improved, but unnecessary energy consumption occurs when contactor is inadvertently ON
Solution Approach 1:
The control circuit uses voltage monitoring feedback to determine whether discharge should continue or be interrupted. By comparing real-time voltage against the predetermined characteristic, the system only performs discharge when actually needed (contactor OFF) and interrupts when not needed (contactor ON), thus ensuring discharge completeness when required while avoiding wasteful energy consumption.
Solution Approach 2:
The discharge circuit transitions from a static continuous operation mode to a dynamic controlled mode. The discharge state (ON/OFF) changes dynamically based on the contactor status and voltage characteristics, allowing the system to adapt between ensuring complete discharge and preventing wasteful consumption according to actual operating conditions.
3Reliability
If the discharge current is limited to prevent damage, then circuit safety is improved, but discharge time is prolonged reducing efficiency
Solution Approach 1:
The control circuit is pre-configured with the predetermined voltage decrease characteristic that defines safe discharge parameters. This preliminary setup allows the discharge to proceed at optimal speed while automatically preventing damage by interrupting when voltage exceeds the predetermined characteristic, thus resolving the contradiction between discharge speed and protection.
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
Effectively prevents prolonged discharge current flow even if the contactor inadvertently turns ON, ensuring safe and efficient capacitor discharge.
Implementation Method 1
a resistor (324) that discharges charge in the capacitor (326)
Data Source
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AI summary
A discharge circuit for a DC power supply smoothing capacitor 326 that is used in a power conversion device 200 that supplies DC power via a switch to the DC power supply smoothing capacitor 326 and an inverter 144, includes; a resistor 324 that discharges charge in the capacitor 326; a switch 325 connected in series with the resistor 324, that either passes or intercepts discharge current flowing from the capacitor 326 to the resistor 324; a measurement circuit 317, 319 that measures a terminal voltage of the capacitor 326; and a control circuit 172 that controls continuity and discontinuity of the switch 325; wherein the control circuit 172, after having made the switch 325 continuous and starting discharge of the capacitor 326 by the resistor 324, if a terminal voltage of the capacitor 326 as measured by the measurement circuit 317, 319 exceeds a voltage decrease characteristic set in advance, makes the switch 325 discontinuous and stops discharge by the resistor 324.