Synchronous Rectifier Current-Sensor Control Against Reverse Current
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Solution Overview
Problem
Synchronous rectifiers face inefficiencies due to passive losses in diodes and safety concerns with active elements, exacerbated by unpredictable current flow and complex impedance, requiring precise control that is often inaccurate due to electromagnetic interference and voltage measurements.
Innovation Solution
A synchronous rectifier design using a single current sensor to control both switches based on current measurements, eliminating the need for voltage sensors and reducing noise susceptibility, with control logic ensuring safe and efficient operation by preventing reverse current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If voltage sensors are used to control each active circuit element in synchronous rectifiers, 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 to indirectly obtain switching control information. Instead of directly measuring the problematic low voltage across the switching element (which is susceptible to EMI), the system measures the current through the switching element using a current sensor, and derives the voltage state from this current measurement. This intermediary approach avoids the EMI problem while achieving the same control objective.
2Reliability
If passive circuit elements are used in rectifiers, then intrinsic safety is improved due to unidirectional current flow, but efficiency deteriorates due to losses in passive elements
Solution Approach 1:
The patent employs current sensing to enable the active circuit elements to self-regulate their operation. By monitoring the current through each switching element and comparing it to reference values, the system automatically controls the switching elements to maintain safe operation without requiring external safety mechanisms. This self-service approach allows the use of efficient active elements while preserving safety characteristics.
3Loss of energy
If active circuit elements are used in synchronous rectifiers, then efficiency is improved by reducing losses, but safety deteriorates due to potential current flow in wrong direction
Solution Approach 1:
The patent implements a feedback control mechanism where the current sensor continuously monitors the current through each switching element, and this measured current is fed back to the control logic. The control logic compares the measured current with reference values and adjusts the switching element operation accordingly. This feedback loop ensures that active circuit elements operate safely by preventing current flow in the wrong direction while maintaining high efficiency.
Data Source
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AI summary
A synchronous rectifier (100) including a first rectifier current path. The first rectifier current path has a first (104) and second (105) switching arrangement, which are arranged in series. The first switching arrangement (104) includes a first switch and the second switching arrangement includes a second switch. A first current sensor (108) is arranged to measure a current through the first rectifier current path; and a controller (110) is arranged to operate the first switch and the second switch based on the current measured by the first current sensor (108).