Resonant Converter EMI Suppression via Gain Modulation
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Solution Overview
Problem
Conventional switching power supply products with resonant converters face challenges in meeting electromagnetic compatibility (EMC) standards due to electromagnetic interference (EMI) noise, which is typically addressed by adding filter circuits or shielding, leading to increased cost and volume without effectively managing spatial coupling interference.
Innovation Solution
A control method that adjusts the gain of the resonant converter by generating a time-varying control signal based on the phase of the ripple voltage, extending the frequency range of the drive signal to reduce EMI noise intensity without altering the hardware structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a multi-stage filter circuit is added to suppress EMI noise, then the filtering effect is improved, but the product volume and cost increase
Solution Approach 1:
The patent replaces the traditional hardware-based filter circuit approach with a control method that adjusts the resonant converter's operating parameters. By using control signals to modulate the switching frequency and duty cycle, the system achieves EMI suppression without adding physical filter components, thereby avoiding increased product volume.
Solution Approach 2:
The patent changes the operating parameters of the resonant converter dynamically by adjusting switching frequency and duty cycle through control signals. This parameter modulation allows the system to suppress EMI noise at the source by avoiding resonant frequencies and optimizing switching characteristics, eliminating the need for additional filter hardware.
2Object-affected harmful factors
If a multi-stage filter circuit is added to suppress EMI noise, then the filtering effect is improved, but the cost increases
Solution Approach 1:
The patent substitutes expensive multi-stage filter circuits with a control-based EMI suppression method. By using existing control circuitry to adjust operating parameters, the system achieves comparable or superior EMI performance without the cost of additional filter components, reducing overall manufacturing cost.
Solution Approach 2:
The resonant converter suppresses its own EMI noise through self-regulation of switching parameters. The control system continuously monitors and adjusts frequency and duty cycle to minimize EMI generation at the source, eliminating the need for separate filter circuits and associated costs.
3Reliability
If a shielding cover is added to prevent spatial coupling interference, then the filtering performance is protected, but the cost and space increase
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the operating parameters of the resonant converter to avoid EMI-prone conditions. By proactively modulating switching frequency and duty cycle before EMI issues arise, the system prevents spatial coupling interference without requiring shielding covers, thereby saving space.
4Speed
If the gain of the resonant converter is adjusted periodically, then the frequency range of drive signal is extended, but the control complexity increases
Solution Approach 1:
The patent implements periodic action by cyclically adjusting the gain of the resonant converter through control signals. This periodic modulation of switching parameters extends the effective frequency range of the drive signal, allowing the system to operate across broader frequency bands while managing control complexity through structured periodic variations.
Data Source
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AI summary
The present application provides a conversion system and a control method thereof. The conversion system includes a PFC circuit (101), a bus capacitor (102) and a resonant converter (103). An input terminal of the PFC circuit (101) is electrically coupled to an alternating current source, and an output terminal of the PFC circuit (101) is electrically coupled to the bus capacitor (102) and an input terminal of resonant converter (103), and the control method includes the following steps: acquiring a phase of a ripple voltage of the bus capacitor; generating a time varying control signal according to the phase of the ripple voltage; adjusting a gain of the resonant converter periodically according to the time varying control signal to extend a frequency range of a drive signal output to a switching transistor in the resonant converter, thereby reducing a noise intensity of a single frequency band, so as to suppress the EMI noise.