Power Converter Current Sensing with Duty Cycle Compensation
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Solution Overview
Problem
Existing power converters face inefficiencies in current limiting and current sharing functions, particularly in delivering high currents at low voltages, with existing methods requiring complex sensing mechanisms and resulting in lower sensitivity, efficiency, and accuracy due to common mode noise and voltage level shifts.
Innovation Solution
The implementation of an average current mode control methodology that senses only a portion of the output current referenced to the converter ground, compensates for duty cycle variations, and averages the signal to control the output current, allowing for accurate current limiting and sharing with reduced complexity and increased efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complete output current waveform sensing is implemented using traditional sensors, then current limiting and current sharing functions can be achieved, but sensing efficiency decreases and common mode noise interference increases
Solution Approach 1:
The patent extracts only the essential current information needed for control by sensing current through the low side switch during its ON state, rather than sensing the complete output current waveform. This selective extraction of necessary information reduces sensing complexity and improves efficiency while maintaining adequate current control functionality
Solution Approach 2:
The patent uses the low side switch as an intermediary element to sense output current indirectly. By measuring the current through this switch during its ON period and processing it through compensation and averaging circuits, the system achieves accurate current control without directly sensing the complete output waveform, thereby reducing common mode noise interference
2Measurement precision
If traditional current sensing methods are used with wide output voltage range, then current can be monitored, but common mode rejection requirements increase and signal integrity degrades
Solution Approach 1:
The patent extracts current information only during the low side switch ON period, creating a simplified sensing signal that is less susceptible to common mode noise. By processing this extracted signal through compensation and averaging circuits, accurate current measurement is achieved without requiring high common mode rejection
Solution Approach 2:
The patent creates a compensated and averaged copy of the current signal that represents the output current accurately. This processed copy, generated through digital signal processing, maintains measurement precision while being inherently more robust against common mode interference than direct sensing approaches
3Power
If multiple power converters are operated in parallel for high current delivery, then current sharing function is required, but existing sensing approaches increase system complexity
Solution Approach 1:
The patent implements a universal current sensing and control approach that works for both single converter and parallel converter configurations. The same simplified sensing method, compensation technique, and averaging process used for individual converter control also enables accurate current sharing in parallel operations, reducing overall system complexity
Solution Approach 2:
The patent uses digital signal processing to create processed copies of current signals from multiple converters, allowing centralized or distributed control to achieve accurate current sharing. This copying and processing approach simplifies the control architecture compared to traditional analog sensing methods
Data Source
AI summary
A power converter provides current limit/current share functionality, allowing use in a point-of-load architecture and/or in parallel with one or more other power converters. An inner current control loop may sense output current over only a portion of a duty cycle, for example at a low side active switch. The resulting signal is compensated, and may be level shifted, for example via a resistor divider network, and supplied to a current control amplifier. An outer voltage control loop may sense output voltage, and provide a voltage error signal from a voltage error amplifier to the resistor divider network. Power converters are operable as masters or slaves, and include sense input and trim input terminals.