Parallel Switch Current Control via Self-Calibration
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Solution Overview
Problem
Paralleled power switching devices in power converters often experience current imbalances due to manufacturing tolerances and temperature differences, leading to potential overheating and damage, which conventional methods like passive components and active control struggle to fully address without increasing EMI and complexity.
Innovation Solution
A method that involves measuring the threshold voltage of each switching device during startup to compute and apply a time delay to the gate signals, ensuring synchronized turn-on times and reducing current imbalances, particularly during transient states, using a self-calibration process and high pass filtering to detect input capacitance discontinuities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive components like inductors are added in series with switching devices to reduce current imbalance, then current sharing during transient is improved, but switching speed is slowed down and EMI increases
Solution Approach 1:
The patent replaces passive electrical components (inductors) with an active control system that uses sensing elements to detect current imbalance and control devices to adjust gate drive signals. This substitution eliminates the need for series inductance while maintaining current balance, thereby preserving switching speed and reducing EMI.
Solution Approach 2:
The patent introduces sensing elements and control devices as intermediaries between the control signal source and the switching devices. These intermediaries detect current imbalance and modulate gate drive signals accordingly, enabling precise current balancing without adding series impedance that would slow switching.
2Reliability
If active control devices are added to counteract current imbalances during steady state, then current balance is improved, but device complexity increases
Solution Approach 1:
The patent divides the control function into separate modular components: sensing elements for each switching device, control devices for signal adjustment, and a control signal source. This segmentation allows independent optimization of each component and simplifies implementation while achieving effective current balancing.
Solution Approach 2:
The patent implements a feedback mechanism where sensing elements continuously monitor current through each switching device and feed this information to control devices. The control devices then adjust gate drive signals based on detected imbalances, creating a closed-loop system that automatically maintains current balance without complex manual control.
3Reliability
If series inductance impedance is added to the power path, then current imbalance during transient is reduced, but EMI is adversely affected
Solution Approach 1:
The patent replaces passive inductance-based current balancing with an active electronic control system. By using sensing elements and control devices to dynamically adjust gate drive signals, the system achieves current balance without introducing series inductance into the power path, thereby eliminating the EMI problems associated with inductive components.
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
Effectively reduces current imbalances during switch-on and switch-off, enhancing the operational safety of power converters while minimizing EMI and maintaining system simplicity.
Implementation Method 1
measuring the threshold voltage of each switching device
Implementation Method 2
high pass filtering to detect input capacitance discontinuities
Implementation Method 3
compute and apply a time delay to the gate signals, ensuring synchronized turn-on times
Implementation Method 4
Distributing losses between several devices means that there is a lower risk of overheating at the device junction
Implementation Method 5
device junction temperatures
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2
AI summary
A method of controlling a power converter having a plurality of parallel-connected switching devices, the method comprising: measuring a threshold voltage of each of the parallel switching devices based on measuring the respective base current at start up of the parallel power converter in an initial self-calibration process; and determining synchronization of the times at which the threshold voltages of the respective switching devices occur.