Switching Power Supply Noise Balancing for Common-Mode Currents
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Switching power-supply units face challenges in suppressing common-mode noise and associated heat generation and power loss, particularly due to the need for large-size high-impedance common-mode choke coils when used in conjunction with power conversion circuits that handle high currents.
Innovation Solution
A switching power-supply unit configuration that includes a power conversion circuit, a control circuit, a control-circuit-side common-mode choke coil, and half-bridge capacitors, forming a noise balancing circuit to confine and cancel out common-mode currents, with the common-mode choke coil connected to the control circuit on a lower power side to minimize heat generation and power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a large-size common-mode choke coil with high impedance is used to suppress common-mode noise, then common-mode noise suppression is improved, but heat generation and power loss increase
Solution Approach 1:
The patent divides the common-mode noise suppression function into two separate choke coils: one for the power conversion circuit and one for the control circuit. This segmentation allows each choke coil to be optimized for its specific circuit's current level, with the control circuit choke coil experiencing lower currents and thus generating less heat and power loss while still providing effective noise suppression for its respective circuit.
Solution Approach 2:
The patent applies different impedance characteristics to different parts of the system by using separate choke coils tailored to each circuit's requirements. The control circuit choke coil is designed with impedance appropriate for low-current control signals, while the power conversion choke coil handles high-current power signals, optimizing noise suppression efficiency while minimizing unnecessary heat generation in each location.
2Object-affected harmful factors
If a large-size common-mode choke coil with high impedance is used to suppress common-mode noise, then common-mode noise suppression is improved, but the size and cost of the choke coil increase
Solution Approach 1:
The patent segments the common-mode noise suppression function into two separate choke coils, allowing each to be sized appropriately for its specific application. The control circuit choke coil can be much smaller than a single large choke coil would need to be to handle both power and control currents, reducing overall size and cost while maintaining effective noise suppression.
3Object-affected harmful factors
If a common-mode choke coil is connected to a power conversion circuit with large current, then common-mode noise suppression is improved, but heat generation and power loss of the choke coil increase
Solution Approach 1:
The patent separates the common-mode noise suppression into dedicated choke coils for power conversion and control circuits. The control circuit choke coil operates at lower currents, significantly reducing heat generation and temperature rise compared to using a single large choke coil that would need to handle both power and control currents.
Solution Approach 2:
The patent optimizes each choke coil's impedance and size for its specific circuit's current characteristics. The control circuit choke coil is designed with appropriate impedance for low-current control signals, minimizing I²R losses and heat generation in that specific location where sensitive control electronics operate.
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 configuration effectively reduces common-mode noise occurrence from both power conversion and control circuits, suppresses heat generation and power loss, and allows for a smaller, less expensive common-mode choke coil, thereby improving the efficiency and reliability of the power supply unit.
Implementation Method 1
a control-circuit-side common-mode choke coil that is connected to the control circuit on the second direct-current power supply side
Implementation Method 2
a first half-bridge capacitor that is connected to the power conversion circuit on the first direct-current power supply side; and a second half-bridge capacitor that is connected to the control circuit on the second direct-current power supply side
Data Source
AI summary
A switching power-supply unit includes a power conversion circuit, a control circuit, a common-mode choke coil, and half-bridge capacitors. The common-mode choke coil is connected to the control circuit on its side of a direct-current power supply. The half-bridge capacitor is connected to the power conversion circuit on its side of a direct-current power supply, and is connected to the control circuit on its side of the direct-current power supply. A midway point of the half-bridge capacitor is electrically connected to a midway point of the half-bridge capacitor. A noise balancing circuit is configured as a closed circuit including the power conversion circuit, the control circuit, the half-bridge capacitors, and the common-mode choke coil, and causes common-mode currents to be confined and canceled out each other. The common-mode currents are switching noise generated in multiple parts of the closed circuit due to a switching operation of power-conversion switching devices.