Totem-Pole AC-DC Converter Zero-Crossing PWM for Common Mode Noise
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Solution Overview
Problem
In totem-pole power factor correction circuits, large voltage changes across low-frequency MOSFET switches at zero crossings of AC voltage input induce common mode current due to capacitance charging and discharging, leading to significant common mode noise.
Innovation Solution
A switch-mode AC-DC power converter with a bridgeless totem-pole circuit arrangement and a control circuit that applies pulse-width modulation (PWM) control signals to reduce the rate of voltage change across switches during zero crossings, specifically by supplying PWM signals to the fourth switch during zero crossings to mitigate common mode noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large voltage changes are allowed across MOSFET switches at zero crossings, then power conversion efficiency is improved, but common mode noise increases due to capacitance charging and discharging
Solution Approach 1:
The control circuit proactively manages switch transitions by applying PWM control signals to the fourth switch before and during the zero crossing event. This preliminary action prepares the circuit state to minimize voltage changes across MOSFET switches at the critical moment, thereby reducing common mode noise while maintaining efficient power conversion.
Solution Approach 2:
The control circuit applies pulse-width modulation (PWM) control signals periodically synchronized with the AC voltage input cycle. By timing the PWM signals to coincide with zero crossings, the circuit repeatedly mitigates voltage changes and common mode noise generation at each cycle, achieving continuous noise reduction throughout operation.
2Object-generated harmful factors
If PWM control signals are applied to reduce voltage change rate across switches, then common mode noise is reduced, but control circuit complexity increases
Solution Approach 1:
The control circuit performs multiple functions: it generates PWM control signals for power switching, synchronizes with AC voltage zero crossings, and actively manages voltage change rates across switches. By consolidating these functions into a single control unit, the patent achieves noise reduction without proportionally increasing overall system complexity.
Solution Approach 2:
The control circuit monitors the AC voltage input and uses this feedback to timing the PWM control signals appropriately. By detecting zero crossings and adjusting switch control accordingly, the circuit achieves adaptive noise reduction that responds to actual operating conditions, optimizing performance without requiring overly complex predetermined control logic.
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 reduces common mode noise by controlling the rate of voltage change across MOSFET switches, thereby minimizing induced common mode current and improving the converter's performance.
Implementation Method 1
apply pulse-width modulation (PWM) control signals to the third and fourth switches
Implementation Method 2
large voltage changes induce common mode current that is due at least in part to charging and discharging of a capacitance between an output terminal of the circuit and an earth ground
Data Source
AI summary
A switch-mode AC-DC power converter includes a pair of input terminals, a pair of output terminals, and four switches coupled in a bridgeless totem-pole circuit arrangement between the pair of input terminals and the pair of output terminals. A control circuit is coupled to the four switches and configured to, during a cycle of an AC voltage input, turn on the first switch, turn off the second switch, and apply pulse-width modulation (PWM) control signals to the third and fourth switches. The control circuit is also configured to, during a zero crossing of the AC voltage input, supply a PWM control signal to the fourth switch to reduce a rate of voltage change across the second switch at the zero crossing to reduce common mode noise of the power converter.