DC-DC Power Supply Circuit for Conducted Noise Suppression
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Solution Overview
Problem
In-vehicle electronic equipment experiences electromagnetic compatibility (EMC) issues due to radiation noise emitted from switching power supplies, which fail to meet EMC standards like CISPR 25, primarily because of the drastic current changes in power supply cables during switching operations of DC-DC converters.
Innovation Solution
A direct current power supply apparatus is designed with a current stabilizing circuit connected before or after the DC-DC converter, incorporating a variable oscillating circuit and oscillating control circuit to change the frequency of the oscillating signal to a value longer than the switching frequency, combined with a spectrum diffusion function to distribute electromagnetic noise across a broader frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a switching power supply (DC-DC converter) is used to convert direct current voltage, then power supply efficiency is improved and voltage decrease is prevented, but conducted noise and radiation noise are generated due to drastic current changes during switching operations
Solution Approach 1:
The patent applies preliminary anti-action by introducing a current stabilizing circuit that proactively suppresses current fluctuations before they generate noise. The circuit uses feedback control to detect and counteract current changes caused by switching operations, thereby preventing conducted and radiated noise while maintaining the efficiency benefits of the DC-DC converter.
Solution Approach 2:
The patent uses an intermediary approach by inserting a current stabilizing circuit between the DC-DC converter and the power supply cable. This intermediary circuit acts as a buffer that smooths current variations, allowing the switching power supply to operate efficiently while the stabilizing circuit handles the noise-generating current changes.
2Reliability
If a current stabilizing circuit is added to suppress noise, then EMC compliance is improved, but device complexity increases
Solution Approach 1:
The patent merges the current stabilizing function with the existing DC-DC converter control system. The current stabilizing circuit is integrated into the converter's control architecture, sharing common components such as the microcontroller and feedback pathways, thereby achieving noise suppression without proportionally increasing overall device complexity.
Solution Approach 2:
The patent implements multi-functionality by designing the current stabilizing circuit to serve multiple purposes: it suppresses conducted noise, reduces radiated noise, and maintains power supply efficiency. This universal approach allows a single circuit addition to address multiple EMC issues simultaneously, reducing the need for separate dedicated noise suppression components.
Data Source
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AI summary
A direct current power supply apparatus that converts direct current input voltage supplied from a direct current power supply and that outputs a direct current voltage at a different potential is shown. The apparatus includes a switching power supply apparatus and a current stabilizing circuit connected at a stage before or after the switching power supply apparatus. The switching power supply apparatus includes, an oscillating circuit in which a frequency is variable and that generates an oscillating signal to apply a switching frequency, and an oscillating control circuit that generates an oscillating control voltage or an oscillating control current that changes the frequency of the oscillating circuit to the frequency longer than the switching frequency.