Semiconductor Switch Control Circuit for EMC Interference Reduction
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Solution Overview
Problem
Existing electronic circuit technologies face challenges in minimizing high-frequency interference when switching inductive loads, such as EC motor windings, which requires costly and large EMC filters to suppress interference spectra while maintaining minimal switching losses.
Innovation Solution
A novel control unit that modulates the switch edges by varying the control current based on the time profile of voltages measured at both the freewheeling element and the semiconductor switch, allowing for reduction of interference spectra without the need for costly EMC filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the semiconductor switch is switched on and off rapidly to minimize switching losses, then switching losses are reduced and cooling means can be kept small, but high-frequency interference voltages are generated that require costly and large EMC filters
Solution Approach 1:
The control unit preemptively shapes the control signal to prevent high-frequency interference from occurring in the first place. By applying preliminary action to the control signal (smoothing edges, limiting dv/dt), the patent prevents the generation of harmful interference voltages while maintaining rapid switching capability, thus resolving the contradiction between minimizing switching losses and preventing high-frequency interference without requiring large EMC filters
Solution Approach 2:
The control unit dynamically adjusts parameters of the control signal such as rise time, fall time, and voltage levels based on the switching state and load conditions. By changing these parameters adaptively, the system achieves rapid switching with minimal losses while simultaneously controlling the spectral content to reduce high-frequency interference, eliminating the need for costly EMC filtration
2Object-generated harmful factors
If costly and large EMC filters are constructed to suppress interference spectra, then high-frequency interference is reduced, but installation space increases and costs rise
Solution Approach 1:
The patent converts the potentially harmful effect of rapid switching (generation of high-frequency interference) into a beneficial control mechanism. By deliberately shaping the control signal to have controlled edges and voltage profiles, the system uses the switching action itself to prevent interference generation, thereby eliminating the need for separate EMC filters and reducing installation space and costs
Solution Approach 2:
The patent extracts the EMC filtering function from the hardware domain and relocates it to the control signal domain. By implementing interference suppression through software/control signal processing rather than passive hardware filters, the system eliminates the need for large, costly EMC filters while maintaining effective interference suppression
Data Source
AI summary
An electronic circuit comprises at least one semiconductor switch mounted with its switching path in series with an inductive load to be triggered, and at least one freewheeling element that interacts with the semiconductor switch during switching phases and is also mounted in series with the load. A control unit controls a control connection of the semiconductor switch with a variable control current as a function of the time profile of a voltage measured at the freewheeling element and/or as a function of the time profile of the voltage measured at the switching path. A method for triggering a semiconductor switch of such a circuit, triggered by a variable control current for switching, the control current predefined as a function of the time profile of a voltage measured at the freewheeling element and/or as a function of the time profile of the voltage measured at the switching path.