Parallel MOSFET Current Sharing With Thermal Gate Feedback
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Solution Overview
Problem
Existing electronic circuits with parallel-connected transistors face challenges in uniform current distribution, leading to potential overheating and voltage drops, especially in applications with low voltages at high currents, making it difficult to prevent thermal runaway.
Innovation Solution
The proposed electronic circuit arrangement includes a pair of MOSFETs connected in parallel with source resistors and thermally coupled transistors that adjust gate voltages based on thermal couplings to equalize current and temperature, allowing for low source resistances and reduced voltage loss, even when driven to full output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large series resistors are inserted into each emitter or source line to prevent thermal runaway, then current distribution uniformity is improved, but voltage drops increase and additional power loss occurs
Solution Approach 1:
The patent changes the resistance value parameter dynamically based on temperature conditions. At normal operating temperatures, the circuit maintains very low source resistance (milliohm range) to minimize voltage drops and power losses. When thermal runaway is detected through temperature sensing, the circuit automatically increases the effective source resistance to redistribute current uniformly, thus preventing thermal runaway only when necessary while maintaining low loss during normal operation.
Solution Approach 2:
The patent implements a feedback mechanism where temperature sensors continuously monitor the thermal state of parallel-connected transistors. This temperature information is fed back to a control circuit that adjusts the source resistance accordingly. The feedback loop enables the system to maintain optimal current distribution by increasing resistance only when temperature differences indicate impending thermal runaway, rather than maintaining high resistance continuously.
2Reliability
If large series resistors are used to ensure uniform current distribution, then thermal runaway is prevented, but the circuit performance is degraded due to additional voltage loss
Solution Approach 1:
The patent transforms the static, fixed-value source resistors of conventional circuits into dynamic, adjustable resistance elements. The source resistance is kept minimal (milliohm range) during normal operation to maximize circuit performance and power delivery. When thermal conditions indicate non-uniform current distribution, the resistance is dynamically increased to restore uniformity, thus achieving both high performance and reliability through adaptive resistance control.
3Loss of energy
If minimal source resistance is used to reduce voltage loss, then circuit efficiency is improved, but thermal runaway becomes more difficult to prevent
Solution Approach 1:
The patent introduces temperature sensors and a control circuit as intermediary elements between the power transistors and the source resistance. These intermediaries monitor thermal conditions and mediate the adjustment of source resistance values. This allows the system to maintain minimal resistance for efficiency while having the capability to increase resistance through the intermediary control system when thermal runaway risks are detected, thus resolving the contradiction between efficiency and safety.
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 uniform current distribution and increased maximum power loss with reduced voltage loss, effectively preventing thermal runaway and improving performance in linear operation, especially in applications like battery simulation.
Implementation Method 1
a first thermal coupling is established between the first MOSFET and the first transistor and a second thermal coupling is established between the second MOSFET and the second transistor
Implementation Method 2
The first MOSFET comprises a first resistor at the gate terminal of the first MOSFET, and the second MOSFET comprises a second resistor at the gate terminal of the second MOSFET. A source terminal of the first MOSFET is connected to a first source resistor and a source terminal of the second MOSFET is connected to a second source resistor
Data Source
AI summary
An electronic circuit for uniform distribution of a current includes: a first MOSFET and a second MOSFET, wherein the first MOSFET and the second MOSFET are connected in parallel in order to distribute a current applied to an input terminal, the current flowing towards an output terminal of the electronic circuit, wherein the input terminal is respectively connected to a drain terminal of the first MOSFET and to a drain terminal of the second MOSFET; and a terminal for a control voltage, wherein the control voltage is applied to a gate terminal of the first MOSFET and to a gate terminal of the second MOSFET. The first MOSFET comprises a first resistor at the gate terminal of the first MOSFET, and the second MOSFET comprises a second resistor at the gate terminal of the second MOSFET.