Current-Sensed Synchronous Rectifier Switching Against Reverse Conduction
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Solution Overview
Problem
Synchronous rectifiers face inefficiencies and safety concerns due to the need for precise control of active circuit elements, especially when dealing with complex impedances and unpredictable current flow, which can lead to incorrect switching and potential short-circuits.
Innovation Solution
A synchronous rectifier design using a single current sensor to control both switches based on current measurements, eliminating the need for voltage sensing and reducing susceptibility to noise, thereby enhancing safety and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage sensing is used to control switching arrangements, then switching control can be achieved, but measurement accuracy deteriorates due to electromagnetic interference from surrounding voltages
Solution Approach 1:
The patent introduces a current sensor as an intermediary measurement device that indirectly provides the necessary control information for switching arrangements. Instead of directly measuring voltage across switching elements (which is susceptible to EMI), the system measures current through the rectifier current path and uses this current information to control the switching arrangements, thereby avoiding the harmful electromagnetic interference while maintaining measurement accuracy
Solution Approach 2:
The patent replaces the voltage sensing approach with a current sensing approach. By substituting voltage measurement with current measurement, the system eliminates the measurement of very low voltages that are prone to EMI, and instead measures current which provides a more robust and accurate signal for controlling the switching arrangements
2Loss of energy
If active circuit elements are used to improve efficiency, then energy losses are reduced, but safety deteriorates due to potential current flow in wrong direction
Solution Approach 1:
The patent implements a feedback control system where the controller continuously monitors the current measured by the current sensor and uses this feedback information to control the switching arrangements. The controller operates the switches based on the measured current, ensuring that switches are turned off in time to prevent reverse conduction, thus maintaining both efficiency and safety
Solution Approach 2:
The patent applies preliminary action by controlling the switching arrangements to turn off the switches before reverse conduction can occur. The controller uses the current measurement to predict when current may reverse and takes preliminary action to turn off the switches in advance, preventing the harmful effect of reverse conduction before it can happen
3Device complexity
If a single current sensor is used to control both switches, then device complexity is reduced, but control precision may deteriorate
Solution Approach 1:
The patent applies universality by making the single current sensor serve multiple functions: it measures current for controlling the first switching arrangement, controls the second switching arrangement, and provides information for preventing reverse conduction. This single sensor replaces what would traditionally require multiple voltage sensors, reducing device complexity while maintaining adequate control precision through intelligent control algorithms
Data Source
AI summary
A synchronous rectifier including a first rectifier current path. The first rectifier current path has a first and second switching arrangement, which are arranged in series. The first switching arrangement includes a first switch and the second switching arrangement includes a second switch. A first current sensor is arranged to measure a current through the first rectifier current path; and a controller is arranged to operate the first switch and the second switch based on the current measured by the first current sensor.