Discrete-Time Current Sense Circuit for Flyback Converters
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Solution Overview
Problem
There is a trade-off issue in flyback power converters between accurately sensing the communication protocol current and minimizing power loss, as existing methods either fail to accurately sense the current or incur significant power loss.
Innovation Solution
A discrete-time current sense circuit is introduced, comprising a current mirror circuit, bias circuit, signal conversion circuit, and switches, which samples the communication protocol current in discrete periods to generate a discrete-time current sense signal, reducing power consumption and increasing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous current sensing is used to accurately sense the communication protocol current, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent implements discrete-time current sensing by periodically activating the sampling switch SW2 at specific moments during the power switch conduction period, rather than continuously sensing the current. This periodic sampling approach captures the necessary current information at critical instants while keeping the sensing circuit inactive for the remainder of the cycle, thereby significantly reducing power consumption while maintaining adequate measurement precision for communication protocol current detection
2Loss of energy
If discrete-time current sensing is used to reduce power loss, then energy efficiency is improved, but measurement precision deteriorates
Solution Approach 1:
The patent applies preliminary action by sampling the communication protocol current at specific predetermined moments before the power switch turns off, capturing the current value at the peak or critical point of the conduction period. This timing strategy ensures that the discrete sample taken represents the maximum or most significant current value, maintaining measurement precision for communication protocol determination while allowing the sensing circuit to remain inactive during other periods to minimize power loss
Data Source
AI summary
A discrete-time current sense circuit includes: a current mirror circuit, which includes: a power switch, for providing the communication current; and a sampling switch, which is for sampling the communication protocol current in a sampling period in a discrete manner, to generate a sampling current; a bias circuit, for providing a reference voltage to the reference node in the sampling period according to a communication protocol voltage of the communication protocol voltage node; a signal conversion circuit, for generating the discrete-time current sense signal according to the sampling current; and a first switch, for operating to determine the sampling period; wherein the sampling period is part of a complete period in which the power switch provides the communication protocol current.