Constant Current Control Circuit for Power Converter Line Regulation
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Solution Overview
Problem
Existing constant current control circuits for power converters suffer from poor line regulation, resulting in significant variations in average output current when input voltage changes, leading to instability in power delivery.
Innovation Solution
A constant current control circuit comprising a sample and hold unit, a first capacitor, a discharge unit, a charge unit, and a comparator, which stores and compares current sensing voltages to adjust the duty cycle of the power converter, compensating for input voltage changes to stabilize the average output current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the power converter operates under constant current mode control, then the maximum level of current through the power switch is kept constant, but the average output current varies significantly when input voltage changes
Solution Approach 1:
The patent introduces a feedback mechanism where the current sensing voltage is stored in a sample and hold unit, and the stored voltage is compared with a reference voltage through a comparator. The comparator output controls the duty cycle of the power switch, creating a closed-loop feedback system that adjusts the average output current based on the relationship between input voltage and current characteristics, thereby improving line regulation while maintaining constant current control precision
Solution Approach 2:
The sample and hold unit performs preliminary action by storing the current sensing voltage during specific phases of the switching cycle. This stored voltage represents the peak current information, which is then used by the comparator to determine the appropriate duty cycle adjustment before the next switching cycle begins, enabling proactive compensation for input voltage variations
Data Source
AI summary
A constant current control circuit includes a sample and hold unit coupled to a current sensing resistor of a power converter, for storing a current sensing voltage of the current sensing resistor; a first capacitor for storing a comparison voltage; a discharge unit coupled between the sample and hold unit and the first capacitor, for controlling a discharge current of the first capacitor according to a reference voltage and the current sensing voltage stored in the sample and hold unit; a charge unit coupled to the first capacitor, for controlling a charging current of the first capacitor according to the reference voltage and a ground voltage; and a comparator for comparing the comparison voltage with the reference voltage to generate a comparison result, and outputting a control signal according to the comparison result, in order to control a duty cycle of the power converter.