Multi-Level Power Conversion Control Without Zero-Current Detection
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Solution Overview
Problem
Conventional multi-level AC/DC and DC/DC conversion circuits face inefficiencies due to inaccurate turn-off timing of synchronous rectification switches, which can lead to increased losses or malfunction, and the addition of zero-current or zero-crossing detection circuits increases cost and complexity, while introducing current direction variability and sampling errors.
Innovation Solution
A multi-level AC/DC and DC/DC conversion circuit that calculates the duty ratio of synchronous rectification switches based on input and output voltages, switching cycle, and interval time, reducing cost and enhancing reliability by alternately operating main and synchronous rectification switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If synchronous rectification switch is used to replace rectifier diode to improve efficiency, then circuit efficiency is improved, but turn-off timing accuracy becomes critical and complex to control
Solution Approach 1:
The patent implements a feedback mechanism where the controller detects the voltage polarity across the flying capacitor and uses this feedback signal to determine the optimal turn-off timing of the synchronous rectification switch. The controller continuously monitors the flying capacitor voltage and adjusts the switch turn-off timing based on the detected polarity, ensuring accurate timing without complex external detection circuits.
Solution Approach 2:
The flying capacitor itself serves a dual function: it performs voltage clamping to protect the synchronous rectification switch from overvoltage damage, and simultaneously provides the polarity detection function needed for accurate turn-off timing control. This self-service approach eliminates the need for separate protection and detection circuits, reducing overall system complexity.
2Measurement precision
If zero-current detecting function is added to accurately control turn-off time, then turn-off timing accuracy is improved, but cost and circuit complexity increase
Solution Approach 1:
The flying capacitor is designed to perform multiple functions simultaneously: voltage clamping for switch protection, polarity detection for timing control, and energy storage for circuit operation. By making the existing component multi-functional, the patent eliminates the need for separate zero-current detection circuits, thereby reducing cost and complexity while maintaining timing accuracy.
Solution Approach 2:
The flying capacitor's inherent voltage characteristics are utilized for polarity detection. The controller simply reads the voltage polarity across the flying capacitor to determine when to turn off the synchronous rectification switch, eliminating the need for external detection circuits and reducing overall system complexity.
3Measurement precision
If zero-crossing detection circuit is added to control turn-off time, then turn-off timing is improved, but cost increases and layout difficulty increases
Solution Approach 1:
The flying capacitor serves as both the voltage clamping element and the zero-crossing detection element. The controller detects the polarity voltage across the flying capacitor to determine turn-off timing, eliminating the need for separate zero-crossing detection circuits and simplifying both manufacturing and layout.
Solution Approach 2:
The patent extracts the detection function from a separate circuit component and integrates it into the existing flying capacitor. By using the flying capacitor's voltage polarity as the detection signal, the patent removes the need for additional detection circuits, reducing manufacturing complexity and layout difficulty.
4Reliability
If flying capacitor clamps synchronous rectification switch, then switch protection is improved, but switch may be broken when current is too large
Solution Approach 1:
The controller continuously monitors the voltage polarity across the flying capacitor and uses this feedback to precisely control the turn-off timing of the synchronous rectification switch. By turning off the switch at the optimal moment based on real-time voltage detection, the patent minimizes the duration and magnitude of negative current flow, thereby protecting the switch from damage while maintaining reliable clamping protection.
Data Source
AI summary
In the present disclosure, the multi-level AC/DC conversion circuit and the multi-level DC/DC conversion circuit calculate the duty ratio of synchronous rectification switch according to the input voltage, the output voltage, the interval time of turning on the main switch, the switching cycle and the duty ratio of main switch, thereby eliminating the need for additional zero-current detecting function or zero-crossing detection circuit in conventional AC/DC conversion circuits. Accordingly, for the multi-level AC/DC conversion circuit and the multi-level DC/DC conversion circuit of the present disclosure, the cost is reduced, and the reliability is enhanced.