Isolated SMPS Phase-Staggered Control for Lower Ripple and EMI
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Solution Overview
Problem
Existing isolated switched-mode power supplies (SMPS) face challenges in achieving optimized EMI shielding, balanced thermal distribution, reduced output ripple, smaller output capacitance, and improved conversion efficiency while maintaining higher output power and safety.
Innovation Solution
The proposed solution involves an isolated SMPS with multiple primary and secondary side circuits, transformers, and an isolated controller that generates phase-staggered PWM signals to control power switches, ensuring staggered operation and preventing cross-conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If higher output power is provided by increasing transformer size, switching frequency, or using lower on-resistance transistors, then output power is improved, but EMI shielding capability deteriorates and system size increases
Solution Approach 1:
The patent divides the single primary side circuit into multiple primary side circuits (at least two), each with its own power switch operating in staggered phases. This segmentation allows the system to achieve higher output power through parallel operation while maintaining smaller individual transformer cores and reducing EMI from each switching event, thus resolving the contradiction between output power and EMI shielding capability
2Power
If higher output power is achieved by using bigger transformers and higher switching frequency, then output power is improved, but system size increases
Solution Approach 1:
The patent segments the power conversion function across multiple primary side circuits with staggered operation, allowing each transformer to be smaller while achieving higher total output power through parallel operation. This reduces the overall system size compared to using a single large transformer
Solution Approach 2:
The patent employs periodic staggered switching of multiple primary side circuits, where power switches are turned on at different phases. This periodic action distributes the power delivery over time, enabling higher average output power with smaller magnetic components, thus reducing system size
3Reliability
If current limitation is implemented to avoid breakdown from cross-conduction, then safety is improved, but conversion efficiency deteriorates
Solution Approach 1:
The patent implements preliminary control through the isolated controller that monitors voltage signals and generates phase-staggered PWM signals to turn on power switches at precisely controlled times. This preliminary timing action ensures that switches are activated only when safe, preventing cross-conduction and eliminating the need for degrading current limitation, thus maintaining both safety and conversion efficiency
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
This approach results in reduced size and cost of the power supply, optimized EMI shielding, balanced thermal distribution, less output ripple, smaller required output capacitance, and improved overall conversion efficiency, while ensuring higher safety and preventing potential breakdowns.
Implementation Method 1
at least two transformers each including: a primary winding, which is connected in series with the power switch in a respective one of the primary side circuits and then between an input terminal of the isolated SMPS and a primary reference ground; and a secondary winding, which is connected in series with the synchronous rectifier
Data Source
AI summary
The present application provides an isolated switched-mode power supply, a control method and a computer-readable storage medium. The isolated SMPS includes: primary side circuits each including a power switch; secondary side circuits each including a synchronous rectifier; at least two transformers each including a primary winding connected in series with power switch and a secondary winding connected in series with synchronous rectifier, the number of primary side circuits, the number of secondary side circuits and the number of transformers are equal to one another; an isolated controller adapted to: receive output voltage signal from output terminal and winding voltage signals from secondary windings; based on the output voltage signal and winding voltage signals, generate PWM signals, the number of PWM signals is the same as the number of primary side circuits, and the PWM signals are staggered in phase; and transmit PWM signals to control terminals of power switches.