High-Voltage MOSFET Precharge Circuit for Rapid Switching
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Solution Overview
Problem
Conventional high-voltage MOSFETs in on-board power supply systems face challenges in rapidly switching on and off to precharge intermediate circuit capacitance, leading to high switching times and increased losses and heat development.
Innovation Solution
A circuit arrangement with a first circuit assembly for rapid switch-on and a second circuit assembly for rapid switch-off of the high-voltage MOSFET, utilizing current-switched and voltage-switched switches, a voltage threshold value transmitter, and ohmic resistors to manage energy storage and discharge, allowing for nanosecond switch-on and microsecond switch-off times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional switching methods are used for the high-voltage MOSFET, then the circuit structure is simple, but the switching time is too long (above 600 nanoseconds) causing high losses and heat development
Solution Approach 1:
The circuit pre-charges the gate-source capacitance of the MOSFET before switching is required, so that when switching is needed, the energy is already available and the MOSFET can turn on within nanoseconds. This preliminary energy preparation eliminates the delay in conventional switching methods.
Solution Approach 2:
The switching control is divided into two independent circuit assemblies: a first circuit assembly for rapid switch-on using current-switched switches, and a second circuit assembly for rapid switch-off using voltage-switched switches. This segmentation allows each assembly to be optimized for its specific function, achieving both fast turn-on and turn-off.
2Loss of energy
If rapid switching is achieved through complex circuit arrangements, then switching losses are reduced, but the number of electrical connections and circuit complexity increases
Solution Approach 1:
The first and second circuit assemblies are integrated into a single unified circuit arrangement that shares common components such as the intermediate circuit capacitance and MOSFET. This merging reduces the overall number of connections while maintaining the rapid switching capability through coordinated operation of the two assemblies.
Solution Approach 2:
The intermediate circuit capacitance serves multiple functions: it acts as the energy storage element for the high-voltage power supply, the precharge source for rapid MOSFET switching, and the load for the switching circuits. This multi-functionality reduces the need for separate dedicated components, simplifying the overall circuit.
3Speed
If the gate-source capacitance is charged quickly for rapid switch-on, then switching speed improves, but energy availability and heat management become critical issues
Solution Approach 1:
The gate-source capacitance is periodically recharged during normal operation to maintain readiness for rapid switching. This periodic energy replenishment ensures that when switching is required, the energy is already available, enabling nanosecond turn-on without requiring excessive energy discharge that would generate harmful heat.
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 solution enables quick energy availability for the high-voltage MOSFET during switch-on and rapid safe state attainment during switch-off, reducing switching losses and heat generation.
Implementation Method 1
A rapid switch-on means that the gate-source capacitance is charged as quickly as possible—that is to say the energy is available for the HV MOSFET
Implementation Method 2
Switch-off means that, after the deactivation of the control signal/PWM signal, the energy from the driver stage is reduced as quickly as possible, the MOSFET opens
Implementation Method 3
The precharging current is limited here by means of an external precharging resistor
Data Source
AI summary
The present invention relates to a circuit arrangement for switching a high-voltage MOSFET (7) for precharging an intermediate circuit capacitance of a high-voltage on-board network with a first circuit assembly (11), by means of which the switching times of a high-voltage MOSFET used for charging the intermediate circuit capacitance can be reduced.