SMPS Noise Reduction via Air-Core Inductor Damping
Solution Overview
Problem
Buck-type switching mode power supplies in motor vehicles generate high frequency noise due to parasitic reverse current pulses through catch diodes, which cause electromagnetic interference (EMI) and radio frequency interference (RFI), affecting sensitive electronic systems.
Innovation Solution
Incorporating a small air-core inductor in series between the battery input and the voltage supply input pin of the SMPS, along with the absence of bypass capacitors, to dampen the parasitic reverse current pulses and reduce noise, while maintaining the efficiency of the power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a buck-type switching mode power supply is used to convert battery voltage to lower stable voltage, then voltage conversion efficiency is improved, but high frequency noise and electromagnetic interference are generated
Solution Approach 1:
A small air-core inductor is introduced as an intermediary damping element in series with the catch diode. This inductor acts as a mediator that dampens parasitic reverse current pulses without significantly impacting the main power conversion function, thereby reducing high frequency noise while maintaining voltage conversion efficiency
Solution Approach 2:
The patent modifies the circuit parameters by adding a specific damping element (small air-core inductor with optimized inductance value) to change the current waveform characteristics. This parameter change reduces the amplitude and duration of parasitic reverse current pulses, effectively lowering high frequency noise emissions
2Stability of the object's composition
If bypass capacitors are added to stabilize voltage output, then voltage stability is improved, but parasitic reverse current pulses and noise are increased
Solution Approach 1:
The patent extracts or removes the bypass capacitors from the circuit configuration. By eliminating these capacitors, the source of parasitic reverse current pulses is removed, thereby reducing high frequency noise while alternative voltage stability measures are implemented
Solution Approach 2:
The patent converts the potentially harmful effect of rapid voltage changes into a benefit by using the small air-core inductor to control the rate of current change. The inductor's damping effect transforms what would be harmful current spikes into controlled, reduced-amplitude pulses that maintain voltage stability without generating excessive noise
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
Significantly reduces high frequency noise emissions by attenuating the parasitic reverse current pulses, thereby minimizing EMI/RFI, as demonstrated by oscilloscope traces showing reduced ringing and current spikes in the modified SMPS circuit.
Implementation Method 1
A damping element is included to damp current spikes through the catch diode upon turn-on of the solid state switch and thus reduce noise pulses that would otherwise be introduced by the current spikes
Implementation Method 2
An output filter at the output of the solid state switch includes at least an inductor and a catch diode
Data Source
AI summary
A switching mode power supply generating reduced high frequency noise. The power supply includes a solid state switch, a modulator for driving the solid state switch with a periodic pulse drive signal, an output filter at the output of the solid state switch, where the output filter includes an inductor and a catch diode. A damping element is included for damping current spikes through the catch diode when said solid state switch turns on and thus reduce noise pulses that would otherwise be introduced by the current spikes.