Common Mode Choke PCB Layout for Noise and Heat Dissipation
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Solution Overview
Problem
Existing switching power supply devices face issues with common mode noise and heat dissipation in DC-DC converters due to increased power loss and electromagnetic interference, particularly when using common mode choke coils with high turn counts to increase impedance, which can lead to decreased efficiency and potential electromagnetic interference in connected electronic devices.
Innovation Solution
A switching power supply device with a noise reducing circuit that includes a surface mount type common mode choke coil, capacitors, and a noise balanced circuit on a circuit board, which suppresses common mode noise and improves heat dissipation by using a parallel configuration and through-hole conductors to manage noise currents and dissipate heat effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the number of turns in the common mode choke coil is increased to increase impedance in noise frequency band, then the impedance increases, but power loss due to copper loss increases and power conversion efficiency decreases
Solution Approach 1:
The patent divides the common mode noise suppression function into multiple components: the common mode choke coil (first impedance element) and the differential mode choke coil (second impedance element). This segmentation allows each component to target specific noise types, enabling effective noise suppression without requiring excessive turns in the common mode choke coil, thereby reducing copper loss.
Solution Approach 2:
The patent combines common mode noise suppression and differential mode noise suppression into a single filter circuit by integrating both the common mode choke coil and differential mode choke coil. This merged approach achieves comprehensive EMI filtering while optimizing the turn counts of individual coils to minimize power loss.
2Object-affected harmful factors
If the number of turns in the common mode choke coil is increased to increase impedance, then the impedance increases, but the temperature of the core approaches the Curie temperature and impedance decreases
Solution Approach 1:
By segmenting the noise suppression function into common mode and differential mode components, the patent reduces the burden on the common mode choke coil. This allows the coil to operate at lower temperatures, maintaining core properties and impedance stability without approaching the Curie temperature.
Solution Approach 2:
The differential mode choke coil acts as an intermediary that handles differential mode noise, allowing the common mode choke coil to focus solely on common mode noise with reduced operational stress. This mediator approach prevents the common mode choke coil from overheating and maintaining impedance stability.
3Object-affected harmful factors
If the number of turns in the choke coil is increased to increase impedance, then the impedance increases, but electromagnetic interference in connected electronic devices increases
Solution Approach 1:
The patent segments the filtering function to address different noise modes separately. The differential mode choke coil specifically targets differential mode noise that can cause EMI in connected devices, while the common mode choke coil handles common mode noise. This segmentation enables effective EMI suppression without requiring excessive turns that would generate harmful electromagnetic fields.
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 solution effectively suppresses common mode noise and improves heat dissipation, maintaining power conversion efficiency while reducing electromagnetic interference in connected devices, without the need for high turn counts in the choke coil, thus minimizing power loss.
Implementation Method 1
a common mode choke coil is provided in the direct-current input line as a countermeasure for the electromagnetic interference
Implementation Method 2
heat generated by the common mode choke coil is dissipated through the through-hole conductors, the ground pattern, and the heat dissipation conductor patterns
Implementation Method 3
a common mode noise current flows in an output line of direct-current voltage via a parasitic capacitance formed between a primary winding and a secondary winding of the isolation transformer
Implementation Method 4
because of a stray capacitance formed between the switching device and the metal housing, a steep voltage change is generated when the switching device is turned on or turned off
Data Source
AI summary
A circuit board of a switching power supply device includes a positive terminal circuit pattern and a negative terminal circuit pattern that are provided on a component mount surface and respectively supply currents from input parts to two input terminals of a common mode choke coil. The positive terminal circuit pattern and the negative terminal circuit pattern are positioned in parallel and close to each other. The component mount surface of the circuit board includes a component mount surface side ground pattern arranged below the common mode choke coil. A heat dissipation ground surface of the circuit board includes a ground pattern and a plurality of heat dissipation conductor patterns. Input terminals and output terminals of the common mode choke coil are respectively electrically and thermally connected to the heat dissipation conductor patterns via through-hole conductors provided between the component mount surface and the heat dissipation ground surface.