Parallel Switching Circuit Current Balance via Parasitic Inductance Management
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Solution Overview
Problem
Existing switching circuits face challenges in balancing main currents across transistors connected in parallel, especially at high frequencies, due to increased circuit dimensions for current detection and delay in feedback, making it difficult to maintain current balance during transitions and high-frequency operations.
Innovation Solution
A switching circuit configuration that includes high-speed transistors connected in parallel, with a drive power supply, drive signal source, and a drive circuit that adjusts and balances main currents by managing parasitic inductance through distinct source terminals and drive signals, ensuring equal rated currents and optimized drive conditions for each transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current detection and feedback processing is implemented to balance main currents, then current balance between transistors is improved, but circuit dimensions increase and feedback delay time increases
Solution Approach 1:
The patent extracts the current detection function from the main current path by using sense resistors connected to current sense emitters on the transistor substrates. This separates the detection function from the power handling path, reducing circuit dimensions while maintaining detection capability.
Solution Approach 2:
The patent introduces operational amplifiers as intermediary components that compare sense voltages and generate corrected gate voltages. This intermediary processing enables precise current balancing without requiring direct feedback from the main current path, reducing feedback delay.
2Reliability
If current detection and feedback processing is implemented to balance main currents, then current balance between transistors is improved, but feedback delay time increases
Solution Approach 1:
The patent implements preliminary current balancing by comparing sense voltages before the switching operation completes and adjusting gate voltages in advance. The operational amplifiers process the voltage difference and generate corrected gate signals proactively, reducing feedback delay time and enabling high-frequency switching.
3Power
If transistors are connected in parallel to increase current capacity, then rated current is doubled, but main current balance between transistors becomes difficult to maintain
Solution Approach 1:
The patent implements feedback control by using operational amplifiers to compare sense voltages from parallel transistors and generate corrected gate voltages. This feedback mechanism continuously monitors and adjusts the gate voltages to maintain equal current distribution, enabling reliable parallel operation at doubled current capacity.
4Volume of moving object
If switching frequency is increased to reduce LC component dimensions, then power converter size is reduced, but current balance during transitions becomes difficult to maintain
Solution Approach 1:
The patent performs preliminary current balancing adjustments during the transition periods between switching states. The operational amplifiers detect voltage differences and correct gate voltages before the switching transition completes, ensuring current balance is maintained even at high switching frequencies where transition time is limited.
Data Source
AI summary
A switching circuit includes: a drive power supply; a first transistor and a second transistor; a drive signal source; and a drive circuit. Each of the first transistor and the second transistor includes: a drain electrode and a source electrode in which a main current flows when a corresponding one of the first transistor and the second transistor is ON; a first source terminal for passing the main current; and a second source terminal. Here, the first source terminal is connected to the source electrode at an impedance lower than an impedance of the second source terminal.