LLC DC/DC Converter Noise Suppression for Full-Load Common-Mode Control
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Solution Overview
Problem
The increasing power load capacity in switch-mode power supplies necessitates higher power density, leading to larger magnetic components, which are not conducive to miniaturization, and the higher switching frequencies generate significant switching noise that overwhelms previous-stage filter circuits.
Innovation Solution
A DC/DC converter with an LLC resonant topology, incorporating a transformer, resonant inductor, and capacitor, along with a noise suppression network that generates a suppression current opposite to the total noise current, effectively canceling common mode noise across a full load range by balancing parasitic capacitances and using a signal source and impedance network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the working frequency of the magnetic component is increased to reduce its volume, then the power density is improved, but the switching noise increases significantly
Solution Approach 1:
The patent utilizes the resonant circuit to convert the harmful switching noise into beneficial resonant oscillations. The LLC resonant topology transforms the high-frequency switching disturbances into controlled resonant waves at frequencies where the system naturally oscillates, thereby reducing the harmful noise effects while maintaining high power density operation
Solution Approach 2:
The resonant circuit acts as an intermediary between the switching noise source and the output. It mediates the high-frequency switching disturbances by absorbing and transforming them through resonant oscillations, preventing the direct transmission of harmful noise to the output while allowing efficient power transfer
2Object-affected harmful factors
If a common mode inductor is used to suppress common mode interference, then the filtering effect is improved, but the volume of the magnetic component increases
Solution Approach 1:
The patent converts the harmful common mode interference into beneficial resonant oscillations. The resonant circuit absorbs the common mode noise and transforms it into controlled resonant waves, turning the harmful interference into a useful phenomenon that aids in noise suppression while maintaining compact dimensions
Solution Approach 2:
The patent changes the operating parameters by utilizing resonant frequencies instead of traditional high-frequency switching. By operating at the resonant frequency of the LLC circuit, the system achieves effective common mode noise suppression with significantly reduced magnetic component volumes compared to traditional common mode inductors
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 reduces common mode noise across varying loads, facilitating miniaturization of the converter and communication power supply by minimizing the volume of magnetic components and improving power density.
Implementation Method 1
The primary-side winding, the resonant inductor, and the resonant capacitor are connected between a first node and a second node after being connected in series. The secondary-side winding is connected between a third node and a fourth node. The primary-side winding and the secondary-side winding form a transformer.
Implementation Method 2
a resonant inductor, a resonant capacitor, and a noise suppression network. The primary-side winding, the resonant inductor, and the resonant capacitor are connected between a first node and a second node after being connected in series
Implementation Method 3
The noise suppression network is configured to generate a suppression current. A direction of the suppression current is opposite to a direction of a total noise current generated by the resonant inductor and the resonant capacitor. The suppression current is used to suppress the total noise current.
Data Source
Figure 1~3
Figure 4~6
Figure 7~9A
AI summary
This application discloses a DC/DC converter and a communication power supply. The converter includes a primary-side winding, a secondary-side winding, a resonant inductor, a resonant capacitor, and a noise suppression network. The primary-side winding and the secondary-side winding form a transformer. The noise suppression network is connected between a primary-side quiescent point and a secondary-side quiescent point. The primary-side quiescent point is a direct current stable potential at an input terminal of the DC/DC converter. The secondary-side quiescent point is a direct current stable potential at an output terminal of the DC/DC converter. A first parasitic capacitance between a first terminal of the primary-side winding and the secondary-side quiescent point is equal to a second parasitic capacitance between a second terminal of the primary-side winding and the secondary-side quiescent point. A suppression current is generated by the noise suppression network, has a direction opposite to a direction of a total noise current generated by the resonant inductor and the resonant capacitor, and is used to suppress the total noise current. A voltage of the noise suppression network varies with a size of a load. This implements common mode noise suppression in a full load range, and effectively reduces a common mode noise caused between the primary-side winding and the secondary-side winding.