Isolating Switch Circuit Using Auxiliary Winding for Precise Control
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Solution Overview
Problem
Existing isolating switch circuits face issues of high cost, large power consumption, and low precision due to the use of optical couplers for signal transmission and primary control methods.
Innovation Solution
The proposed isolating switch circuit eliminates the need for optical couplers by using a secondary control circuit to detect first time information related to the freewheeling time of a parasitic diode and secondary current, allowing for precise control of the main power switch transistor without optical couplers, thereby reducing cost and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an optical coupler is used to transmit feedback signals between primary and secondary sides, then signal transmission and isolation are achieved, but cost and power consumption increase
Solution Approach 1:
The patent extracts and eliminates the optical coupler from the traditional isolated feedback system. By detecting the first time information (freewheeling time of parasitic diode) directly on the primary side through voltage sampling and edge detection, the system removes the need for optical signal transmission, thereby reducing power consumption while maintaining feedback functionality
Solution Approach 2:
The patent introduces an auxiliary winding as an intermediary element. This auxiliary winding couples the secondary side information to the primary side through electromagnetic induction, enabling indirect signal transmission without optical couplers. The auxiliary winding acts as a mediator that transfers the first time information across the isolation barrier through magnetic coupling
2Reliability
If an optical coupler is used to transmit feedback signals between primary and secondary sides, then signal transmission and isolation are achieved, but cost increases
Solution Approach 1:
The patent extracts and eliminates the optical coupler from the traditional isolated feedback system. By detecting the first time information (freewheeling time of parasitic diode) directly on the primary side through voltage sampling and edge detection, the system removes the need for optical signal transmission, thereby reducing power consumption while maintaining feedback functionality
Solution Approach 2:
The patent replaces the expensive optical coupler with simpler, cheaper components including an auxiliary winding, voltage sampling circuit, and edge detection circuit. These components are more cost-effective and easier to manufacture, reducing overall system cost while achieving the same isolation and feedback functions
3Ease of operation
If primary control method is used to control main power switch transistor, then control simplicity is maintained, but control precision decreases
Solution Approach 1:
The patent implements precise feedback by detecting the first time information (freewheeling time of parasitic diode) on the primary side and using it to adjust the second time (turn-on timing of main power switch). This closed-loop feedback mechanism based on actual current zero-crossing detection significantly improves control precision compared to traditional primary control methods
Solution Approach 2:
The patent performs preliminary detection of the first time information through the auxiliary winding and voltage sampling circuit before adjusting the main power switch timing. This advance detection and processing enables precise control adjustments, improving measurement precision while maintaining operational simplicity
Data Source
AI summary
The present invention provides an isolating switch circuit and a control method. The present invention takes first time information as a characteristic to control and adjust primary and secondary sides The primary side identifies the first time information by detecting the voltage between two ends of a main power switch transistor, and the secondary side compares a sampling output voltage or/and output current with a corresponding reference signal to obtain a first control signal representing the first time information. The present invention does not need to use the optical coupler to carry out isolated transmission of primary and secondary signals, which reduces the cost of the circuit, and the freewheeling time of a parasitic diode of a synchronous rectification transistor is taken as a characteristic to carry out identifying and controlling, such that power consumption is low and the control and adjustment is more precisely.