Primary Side Controller for Switched Mode Power Supply Output Current Estimation
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Solution Overview
Problem
Conventional switched mode power supplies with secondary side control face inefficiencies due to constant power consumption and inaccurate representation of output current using peak current, which affects load compensation and power conversion efficiency.
Innovation Solution
A primary side controller generates estimation signals based on the charge current and discharge time of a transformer, allowing for accurate representation of output current and enabling precise load compensation by regulating the charge current and generating an offset current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If secondary side control is used to directly sense output current, then output voltage and current regulation can be easily achieved, but power conversion efficiency decreases due to constant power consumption
Solution Approach 1:
The patent segments the control function by placing sensing and control circuits on the primary side rather than the secondary side. The primary side controller senses transformer parameters (peak current, discharge time) and derives output current information without requiring continuous power consumption on the secondary side, thus resolving the contradiction between regulation precision and energy loss.
Solution Approach 2:
The patent uses transformer parameters (peak current Ip, discharge time td) as intermediary variables to represent output current. Instead of directly sensing output current on the secondary side, the controller uses these intermediary measurements from the primary side to infer and regulate output current, eliminating the need for continuous secondary side power consumption while maintaining regulation accuracy.
2Adaptability or versatility
If peak current through transformer is used to represent output current for load compensation, then load compensation can be implemented, but measurement precision is poor because peak current is so different from output current
Solution Approach 1:
The patent implements a feedback mechanism where the controller continuously monitors transformer parameters (peak current Ip and discharge time td) and uses this feedback to calculate and adjust the output current estimation. This feedback loop enables accurate representation of output current by combining multiple transformer parameters rather than relying solely on peak current, thereby improving measurement precision while maintaining load compensation capability.
Solution Approach 2:
The patent changes from using a single parameter (peak current) to using multiple parameters (peak current Ip and discharge time td) to represent output current. By incorporating discharge time as an additional parameter, the system achieves more accurate output current representation that better reflects actual load conditions, enabling precise load compensation while maintaining adaptability.
Data Source
AI summary
Controllers and related control methods for a switched mode power supply are disclosed. The switched mode power supply has an inductive device and a power switch connected in series. An output current estimator in a controller is configured for receiving a current-sense signal representing an inductor current flowing through the inductive device and a discharge-time signal indicating a discharge time of the inductive device. The output current estimator generates a charge current in response to the discharge-time signal and the current-sense signal, thereby the charge current substantially corresponding to an output current that the switched mode power supply outputs to a load. The charge current is limited not to exceed a maximum value. A current limiter is configured for limiting the current-sense signal when the charge current is the maximum value.