Power Semiconductor Gate Current Shaping for Lower EMI Switching
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Solution Overview
Problem
Existing methods for reducing electromagnetic interference emissions from power semiconductors during switching are either ineffective in limiting emissions or result in increased power loss, requiring complex and costly control circuits.
Innovation Solution
A method using a simple current pre-control that divides the control current into two half-waves, with the first half-wave decaying before the second half-wave acts on the power semiconductor, allowing for universal application across different operating points and temperatures, reducing complexity and cost while maintaining comparable interference emissions and power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the switching process is slowed down, then electromagnetic interference emissions are reduced, but power loss within the power semiconductor increases leading to increased heating
Solution Approach 1:
The control current is divided into two distinct half-waves: a first half-wave that charges the input capacitance and a second half-wave that completes the switching action. This segmentation allows the switching process to be broken into controlled stages, reducing electromagnetic interference while managing power loss through optimized timing and amplitude of each half-wave.
Solution Approach 2:
The first half-wave of the control current performs a preliminary charging action on the input capacitance before the main switching action. By pre-charging the capacitance with a controlled current waveform, the subsequent switching transition is smoother and generates less electromagnetic interference, while the total energy loss is managed through the decay timing between half-waves.
2Loss of energy
If faster switching of the power semiconductor is used, then power loss is reduced, but electromagnetic interference emissions increase
Solution Approach 1:
The control current is structured as periodic half-waves with specific timing relationships. The first half-wave charges the input capacitance, then decays to zero before the second half-wave begins. This periodic structure with controlled duty cycle and frequency allows fast switching action while shaping the current waveform to minimize electromagnetic interference emissions.
Solution Approach 2:
The amplitude, duration, and timing of the control current half-waves are optimized parameters. By adjusting these parameters, the switching speed can be increased to reduce power loss while the waveform shaping maintains electromagnetic interference within acceptable limits. The decay time constant and half-wave amplitude ratios are critical parameters for balancing these competing requirements.
3Object-affected harmful factors
If complex control circuits with multiple control loops and correction circuits are used, then electromagnetic interference emissions are reduced, but device complexity and cost increase
Solution Approach 1:
The complex correction circuits and multiple control loops from prior art are extracted and replaced with a single control loop that directly generates the two half-wave control currents. This extraction simplifies the control architecture while maintaining the ability to reduce electromagnetic interference through the inherent waveform shaping of the half-wave control strategy.
Solution Approach 2:
The control circuit generates both half-waves of the control current through a single control loop without requiring separate correction circuits for voltage and current. The circuit self-regulates the switching process by naturally producing the required bipolar control waveforms, eliminating the need for additional complexity while achieving comparable electromagnetic interference reduction.
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
The method effectively reduces electromagnetic interference emissions while minimizing power loss and operational complexity, offering robustness across various operating conditions without the need for adaptive control adjustments.
Implementation Method 1
the capacitive input of the power semiconductor is subjected to a voltage jump and then a very high current spontaneously flows into the input electrode of the power semiconductor
Data Source
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AI summary
The invention relates to a method for reducing electromagnetic emissions during the activation of a power semiconductor (16) by means of a current pilot controller (25) and a device (10) for carrying out the method, wherein the power semiconductor (16) controls a load (12) such that after activation a load current (IL, lD,3, lD,4) flows through the load (12) and the power semiconductor (16), the saturation value (lD,sat,3, lD,sat,4) of which defines an operating point of the power semiconductor (16), and wherein different operating points of the power semiconductor (16) result for different saturation values (lD,sat,3, lD,sat,4) of the load current (IL, lD,3, lD,4). The method is characterized in that a control current (lS, IG,3, IG,4) predetermined by the current pilot controller (25) is divided substantially into at least two consecutive half-waves (44, 46), wherein for the operating point of the power semiconductor (16) corresponding to the highest saturation value (lD,sat,3) of the load current (lD,3), a further half-wave (46) follows a first half-wave (44) when the load current (IL, lD,3) has approximately reached the maximum value (lD,max,3) thereof.