Parallel MOSFET Driver Feedback for Uniform Current Sharing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In electrical power applications, operating multiple semiconductor switches in parallel leads to nonuniform current distribution due to small disparities in device parameters, causing device overload and failure, especially in wide bandgap semiconductor switches like SiC power transistors operating at high frequencies and voltages.
Innovation Solution
A control circuit and driver circuit system that senses the states of parallel-connected semiconductor switches, adjusts power supply voltages, and controls output resistors to ensure uniform current distribution by using sensor circuits with zener diodes and amplifiers to detect on-state voltages and transitions, and communicates through serial links to align switching times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple semiconductor switches are operated in parallel to increase current carrying capacity, then the current carrying capacity is improved, but nonuniform current distribution occurs due to parameter disparities leading to device overload and failure
Solution Approach 1:
The patent implements a feedback control system where sensor circuits monitor the on-state voltage of each parallel-connected semiconductor switch, and the control circuit adjusts the gate drive signals based on these measurements to equalize current distribution. This closed-loop feedback mechanism continuously compensates for parameter variations among devices, ensuring uniform current sharing and preventing overload while maintaining high current carrying capacity.
2Measurement precision
If sensor circuits with zener diodes and amplifiers are used to detect on-state voltages, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces zener diodes as intermediary elements in the sensor circuits. These zener diodes are connected in series with the semiconductor switch and provide a stable reference voltage that simplifies the measurement of on-state voltage. By using the zener diode's breakdown voltage as a reference, the circuit achieves precise voltage detection without requiring complex measurement circuitry, thus balancing measurement precision with circuit simplicity.
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
The solution achieves uniform current distribution among parallel-connected semiconductor switches, reducing the risk of overload and failure by implementing closed-loop feedback control, particularly beneficial for wide bandgap devices like SiC power MOSFETs.
Implementation Method 1
Each sensor circuit may include a resistor and a zener diode coupled in series across one of the MOSFETs and an amplifier configured to detect a voltage across the zener diode
Implementation Method 2
a comparator circuit configured to generate a state transition signal responsive to a voltage across the resistor
Data Source
AI summary
An apparatus includes a plurality of parallel-connected semiconductor switches (e.g., wide bandgap transistors) and a plurality of driver circuits having outputs configured to be coupled to control terminals of respective ones of the plurality of semiconductor switches and configured to drive the parallel-connected semiconductor switches responsive to a common switch state control signal. The apparatus further includes a control circuit configured to sense respective states of respective ones of the parallel-connected semiconductor switches and to control respective ones of the driver circuits responsive to respective ones of the sensed states.