Fail-Safe HV Discharge Circuit for Fast Low-Loss Vehicle Discharge
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Solution Overview
Problem
High voltage systems in motor vehicles face challenges in safely and efficiently discharging electrical components, particularly due to high power loss and slow discharge rates in existing passive methods, and the need for reliable discharge even in fault conditions.
Innovation Solution
A discharge device comprising a series circuit of a discharge resistor and a normally-off semiconductor switch, controlled by a microcontroller that activates the discharge circuit only in the absence of a disable signal, allowing for autonomous and fast discharge with reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a passive resistive discharge method is used, then the discharge device is simple, but the power loss is very high and the discharge time is long
Solution Approach 1:
The patent changes the discharge resistance parameter dynamically by using a semiconductor switch to connect different resistance values in series. The resistance is adjusted based on the capacitor voltage: high resistance when voltage is high (to limit power loss), and low resistance when voltage is low (to maintain discharge rate). This resolves the contradiction by making the discharge device structurally simple yet energy-efficient through parameter variation.
2Device complexity
If a passive resistive discharge method is used, then the discharge device is simple, but the discharge rate is slow
Solution Approach 1:
The patent dynamically changes the discharge resistance parameter based on capacitor voltage levels. When voltage is high, high resistance limits power loss; when voltage drops, resistance decreases to maintain discharge rate. This ensures fast discharge without complex device structure, resolving the contradiction between simplicity and productivity.
3Loss of energy
If the discharge device is dimensioned for acceptable power consumption at high voltages, then the power loss is acceptable, but the discharge rate slows down as voltage decreases
Solution Approach 1:
The patent implements dynamic parameter change by adjusting discharge resistance based on voltage levels. High resistance at high voltage acceptsable power loss, while low resistance at low voltage maintains discharge rate. This resolves the contradiction by making resistance a variable parameter rather than a fixed value.
4Productivity
If a semiconductor switch is used for active discharge, then the discharge rate is fast and power loss is reduced, but the device complexity increases
Solution Approach 1:
The patent uses a semiconductor switch to change the discharge resistance parameter dynamically. The switch connects different resistance values in series based on voltage conditions, enabling fast discharge with reduced power loss while keeping the overall device structure relatively simple through controlled parameter variation.
5Reliability
If the discharge device remains active during normal operation, then the discharge is ready, but the power consumption is high
Solution Approach 1:
The patent prepares the discharge device in advance by keeping the semiconductor switch and control circuit ready, but only activates the discharge path when needed (when voltage exceeds threshold or discharge is requested). This preliminary preparation ensures rapid response while minimizing continuous power consumption during normal operation.
Solution Approach 2:
The patent uses periodic monitoring of capacitor voltage with hysteresis comparison. The discharge device is activated periodically when voltage thresholds are exceeded and deactivated when thresholds are met, creating a periodic on-off operation that ensures discharge readiness while reducing continuous power consumption.
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
Enables rapid and safe discharge of high voltage systems with minimal power loss, ensuring safety and reliability even in fault conditions without the need for additional actuation devices.
Implementation Method 1
a discharge circuit having a discharge resistor and a normally-off first semiconductor switch
Data Source
AI summary
A discharge device, for discharging an electrical network or an electrically operated unit, includes a discharge circuit having a discharge resistor and a normally-off first semiconductor switch connected in series with the discharge resistor. A controller controls the first semiconductor switch. The controller is commanded in such a manner that the discharge circuit is deactivated during normal operation of the electrical network or the electrically operated unit and the discharge circuit is activated in the event of commanding failing to occur. An electrically powered unit and a discharge method are also provided.