Parallel MOSFET Circuit Assembly With Thermal Current Balancing
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Solution Overview
Problem
Existing electronic circuits connecting transistors in parallel face challenges in evenly distributing current and power loss, leading to potential overheating, especially in applications with low voltages and high currents, which complicates power distribution and increases voltage drops.
Innovation Solution
The electronic circuit arrangement includes thermally coupled transistors with MOSFETs, where transistors act as temperature sensors to balance current and temperature between MOSFETs, allowing for smaller source resistances and reduced voltage loss, thereby increasing maximum power loss and improving frequency behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If series resistors are inserted into each emitter or source line to distribute current evenly, then current distribution is improved, but voltage drops increase and additional power loss occurs
Solution Approach 1:
The patent implements feedback by using transistors to sense the temperature of each MOSFET and automatically adjusting the gate voltage accordingly. The transistor base is connected to the MOSFET source, and the transistor collector controls the MOSFET gate, creating a closed-loop feedback system that responds to thermal conditions and balances current distribution without requiring large series resistors.
Solution Approach 2:
The patent introduces transistors as intermediary elements between the MOSFETs and the control system. These transistors act as temperature-sensing mediators that convert thermal information into electrical signals (gate voltage adjustments), enabling indirect control of current distribution through thermal coupling rather than direct electrical resistance.
2Stability of the object's composition
If large series resistors are used to prevent thermal runaway, then thermal stability is improved, but voltage drops create additional power loss
Solution Approach 1:
The feedback mechanism continuously monitors MOSFET temperature through thermally coupled transistors and dynamically adjusts gate voltages to maintain thermal stability. This active feedback control achieves thermal runaway prevention with much smaller source resistors, thereby reducing the voltage drops and power losses associated with large resistive elements.
Solution Approach 2:
The patent replaces the passive mechanical/resistive approach (large series resistors) with an active electronic control system using thermally coupled transistors. This substitution transitions from a resistive-mechanical current balancing method to an electronically-controlled thermal feedback system, achieving the same stability goal with reduced energy loss.
3Power
If transistors are connected in parallel to increase power dissipation capacity, then power handling is improved, but current distribution becomes difficult to control
Solution Approach 1:
The feedback system automatically balances current distribution among parallel MOSFETs by sensing their individual temperatures and adjusting gate voltages accordingly. This self-regulating mechanism simplifies control complexity because the system autonomously distributes current based on real-time thermal conditions rather than requiring complex external control circuitry.
Solution Approach 2:
Each MOSFET- transistor pair forms a self-regulating unit where the transistor monitors its associated MOSFET's temperature and automatically adjusts its gate voltage to maintain optimal operating conditions. This self-service approach enables parallel MOSFETs to automatically balance their own current distribution without requiring complex external control systems.
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 effectively balances current and temperature between MOSFETs connected in parallel, preventing thermal runaway and reducing voltage loss, enabling efficient power distribution even at high currents and low voltages.
Implementation Method 1
a thermal coupling is established between the first MOSFET and the first transistor, as well as between the second MOSFET and the second transistor
Data Source
Figure 1~1b
Figure 2
Figure 3
AI summary
In an electronic circuit arrangement (1) for the uniform distribution of a current in which several MOSFETs (T11, T21) are connected in parallel, the maximum power dissipation is to be increased in linear operation. This is achieved by the circuit arrangement (1) comprising a first transistor (T12) and a second transistor (T22), wherein the first transistor (T12) is arranged in relation to the first MOSFET (T11) and the second transistor (T22) is arranged in the circuit arrangement (1) such that thermal coupling (19) is established between the first MOSFET (T11) and the first transistor (T12), as well as between the second MOSFET (T21) and the second transistor (T22).