Vehicle Horn EMC Interference Suppression via Input Capacitor
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Solution Overview
Problem
Existing motor vehicle horns suffer from electromagnetic radiation interference, leading to issues such as abrupt gear shifting, air conditioner malfunction, and ABS brake system failure, due to inadequate electromagnetic compatibility (EMC), which is not effectively addressed by current solutions like capacitors, resistors, diodes, or inductors, resulting in non-compliance with EMC standards.
Innovation Solution
Connecting one or more capacitors with a capacitance of 220-10000 microfarads in parallel to the power source input terminals of the horn to reduce internal resistance and effectively absorb electromagnetic interference, thereby improving EMC compliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional EMC suppression methods (capacitors, resistors, diodes, inductors) are used in horn circuits, then electromagnetic interference is reduced to some extent, but the horn driving current increases and electromagnet driving power is reduced, causing the horn sound to be weakened
Solution Approach 1:
The patent introduces a specific circuit configuration with capacitor C1 (220-10000μF) connected in parallel with the power source input terminals as an intermediary element. This capacitor acts as a mediator that filters high-frequency electromagnetic interference from the power supply while allowing the main horn driving current to pass through effectively, thus suppressing EMC without significantly reducing electromagnet driving power
Solution Approach 2:
The patent specifies precise parameter ranges for the capacitor (220-10000 microfarads) to optimize the balance between EMC suppression and power delivery. By carefully selecting the capacitance value within this range, the circuit achieves effective high-frequency noise filtering while maintaining sufficient current for strong horn output
2Object-affected harmful factors
If capacitors are used at two ends of driving electromagnet coils for absorbing interference, then electromagnetic interference is absorbed, but the horn driving current increases and horn sound is reduced
Solution Approach 1:
The patent positions capacitor C1 as an intermediary filter at the power source input terminals rather than directly at the electromagnet coils. This strategic placement allows the capacitor to clean the power supply before it reaches the electromagnet, suppressing interference without creating a bypass path that would reduce driving current and horn sound output
3Loss of energy
If serial capacitors and resistors are adopted at two ends of driving electromagnet coils for absorbing interference, then current bypass is reduced, but the interference inhibition action is not effectively improved
Solution Approach 1:
The patent extracts the EMC suppression function from the electromagnet coil terminals and relocates it to the power source input terminals. By placing capacitor C1 at the power input, the circuit separates the interference suppression function from the power delivery path to the electromagnet, achieving effective EMC inhibition without affecting the current bypass characteristics of the electromagnet circuit
Solution Approach 2:
The capacitor at the power source input acts as an intermediary filter that addresses electromagnetic interference at its source rather than attempting to suppress it at the electromagnet terminals. This approach provides more effective interference inhibition without the drawbacks of serial capacitor-resistor configurations
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
This solution significantly reduces conducted and radiated emission interferences, ensuring the horn meets EMC standards during tests like CIRS25 and ISO7637, preventing damage and ensuring driving safety.
Implementation Method 1
Connecting one or more capacitors with a capacitance of 220-10000 microfarads in parallel to the power source input terminals of the horn to reduce internal resistance and effectively absorb electromagnetic interference
Data Source
AI summary
A motor vehicle and/or water craft horn, comprising: at least one capacitor (C2) of about 220-10000 μF connected in parallel at the input terminals of the horn power supply to eliminate electromagnetic interference caused by electromagnetic radiation, conduction, and coupling. Also provided are a method of eliminating motor vehicle and/or water craft horn electromagnetic interference, an electronic device for using on a motor vehicle and/or water craft, and a motor vehicle and/or water craft. The present invention solves the problem of overrun out of limit of conducted emission (CE) and radiated emission (RE) when a motor vehicle or water craft uses a horn for CIRS 25 testing, thus enabling the horn EMC index to meet the standard.