Parallel MOSFET Switching With Temperature-Based Delay Control
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Solution Overview
Problem
The inefficiencies in semiconductor switches, such as MOSFETs, due to differences in operating characteristics and temperature variations lead to excessive heat buildup and reduced power efficiency when used in parallel configurations, potentially causing damage and limiting power switching capacity.
Innovation Solution
A power switching circuit that adjusts the activation timing of MOSFETs based on temperature delta reference signals, allowing for controlled propagation delays to normalize junction temperatures and equalize power dissipation among paralleled MOSFETs, thereby maintaining safe operating conditions and improving manufacturing yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple semiconductor switches are used in parallel to increase power capacity, then the power handling capability is improved, but differences in operating characteristics cause power dissipation as heat and reduce efficiency
Solution Approach 1:
The patent applies preliminary action by measuring the junction temperatures of parallel semiconductor switches before they operate, and using these temperature measurements to pre-calculate and set appropriate propagation delays. This ensures that switches with higher initial temperatures are delayed in their activation, preventing them from dissipating excessive power. The temperature measurement and delay configuration happen in advance, before the actual power switching operation begins.
Solution Approach 2:
The patent implements feedback by continuously monitoring the junction temperatures of parallel semiconductor switches and using this temperature information to dynamically adjust the propagation delays of individual switches. The temperature measurements feed back into the control system, which then modifies the switching timing to equalize power dissipation across all parallel switches, creating a closed-loop control system that optimizes power distribution in real-time.
2Adaptability or versatility
If semiconductor switches operate at different temperatures, then manufacturing variations are accommodated, but temperature differences lead to inefficient operating conditions and excessive heat buildup
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the propagation delay parameter of each semiconductor switch based on its measured junction temperature. Instead of attempting to manufacture all switches with identical characteristics, the system accepts temperature variations as a parameter difference and compensates for it by modifying the timing parameter. This allows switches with different thermal characteristics to operate efficiently together by changing their activation timing rather than their physical properties.
Solution Approach 2:
The patent implements local quality by applying individualized propagation delays to each semiconductor switch based on its specific junction temperature characteristics. Rather than using a uniform switching strategy for all parallel switches, the system tailors the switching timing to the local thermal conditions of each device. This localized approach allows each switch to operate within its optimal temperature range, accommodating manufacturing variations while maintaining overall system efficiency.
3Temperature
If propagation delays are adjusted to normalize temperatures, then temperature equalization is achieved, but switching timing becomes more complex
Solution Approach 1:
The patent introduces an intermediary temperature measurement and control system that mediates between the parallel semiconductor switches. This intermediary system measures junction temperatures, calculates appropriate propagation delays, and inserts these delays into the switching control signals. By placing this intermediary control layer between the control input and the switches, the system simplifies the overall control architecture while achieving temperature normalization, as the intermediary handles the complexity of individual switch timing adjustments.
Data Source
AI summary
In described examples, a first power switching circuit receives a power switching control signal and activates a first power switch in response to the power switching control signal. A second power switching circuit receives the power switching control, activates a second power switch in response to the power switching control signal, and determines a first power switching delay in response to temperature indications of the first and second power switches. The second power switching circuit activates the second power switch at a first delayed time after the activation of the first power switch, where the first delayed time follows the activation of the first power switch by the determined first power switching delay.