Demagnetization Detection Circuit Using Bipolar and Internal MOS Transistors
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Solution Overview
Problem
Conventional switch-mode power converters rely on high-voltage MOS transistors for demagnetization detection, which are costly and increase the size and cost of the converter.
Innovation Solution
Implementing a controller with external bipolar transistors and internal MOS transistors to detect demagnetization, utilizing a demagnetization detector to change logic levels based on base voltage to indicate the end of the demagnetization process, thereby eliminating the need for external components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-voltage MOS transistors are used for demagnetization detection, then detection accuracy is improved, but cost and device size increase
Solution Approach 1:
The patent uses a low-voltage MOS transistor as an internal copy/alternative to the external high-voltage MOS transistor. The internal transistor replicates the demagnetization detection function without requiring the expensive external high-voltage component, thereby reducing cost and device size while maintaining detection capability through the bipolar transistor interface
Solution Approach 2:
The external high-voltage bipolar transistor serves as an intermediary between the high-voltage demagnetization detection node and the internal low-voltage MOS transistor. It translates high-voltage signals into forms that the internal low-voltage transistor can process, eliminating the need for expensive external high-voltage MOS transistors while preserving detection accuracy
2Reliability
If external high-voltage MOS transistors are used, then demagnetization detection capability is improved, but quantity of components increases
Solution Approach 1:
The patent extracts the high-voltage handling function into a single external bipolar transistor while keeping the internal MOS transistor low-voltage. This separation allows the system to maintain demagnetization detection capability through the bipolar transistor's high-voltage interface while reducing the total number of external high-voltage MOS transistors needed
Solution Approach 2:
The external bipolar transistor serves multiple functions: it acts as the demagnetization detection switch, provides high-voltage to low-voltage signal translation, and interfaces with the internal low-voltage MOS transistor. This multi-functionality reduces the overall component count while maintaining reliable demagnetization detection capability
Data Source
AI summary
Controller and method for power converter. For example, a controller for a power converter includes: a first driver configured to generate a drive current and output the drive current to a first terminal of a first transistor, the first transistor further including a second terminal and a third terminal; a second driver configured to generate a drive voltage and output the drive voltage to a fourth terminal of a second transistor, the second transistor further including a fifth terminal and a sixth terminal; a demagnetization detector configured to receive a first voltage of the first terminal of the first transistor and generate a detection signal based at least in part on the first voltage; and a control signal generator configured to receive the detection signal and generate a first control signal and a second control signal based at least in part on the detection signal.