Hybrid Inductor Current Sensing in DC-DC Converters
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Solution Overview
Problem
Current DC-DC converters face challenges in accurately sensing inductor current, especially during long PWM low pulse times, which can lead to inaccurate transient response and output voltage overshoot, degrading system performance.
Innovation Solution
The implementation of a hybrid emulation/measurement current sense circuit that combines the outputs of a current measurement circuit and a current emulation circuit to produce an accurate sense signal over the entire switching cycle, improving sensing accuracy and transient response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional current sensing method is used in DC-DC converters, then the device complexity is low, but the measurement precision of inductor current deteriorates during long PWM low pulse times
Solution Approach 1:
The current sensing function is segmented into two separate circuits: a current measurement circuit that directly measures inductor current, and a current emulation circuit that generates an emulated current signal. Each circuit operates during specific portions of the switching cycle, dividing the sensing task to maintain accuracy while managing complexity.
Solution Approach 2:
The current emulation circuit performs preliminary action by generating an emulated current signal in advance during the PWM low pulse time, before the actual inductor current measurement is needed. This allows the measurement circuit to be reset or prepared for the next measurement cycle, improving overall sensing accuracy.
2Reliability
If a conventional current sensing method is used, then the device complexity is low, but the transient response accuracy deteriorates
Solution Approach 1:
The measurement circuit and emulation circuit are merged through a switch network that combines their outputs. During different portions of the switching cycle, the appropriate circuit output is selected and combined to produce an accurate sense signal that reflects the true inductor current, thereby improving transient response accuracy.
Solution Approach 2:
The current emulation circuit uses feedback from the measurement circuit to generate an accurate emulated signal. The emulation circuit is configured to replicate the inductor current behavior based on feedback information, ensuring that the combined sense signal accurately represents the actual current during transient conditions.
3Measurement precision
If a conventional current sensing method is used, then the circuit structure is simple, but the sense signal accuracy deteriorates during switching cycles
Solution Approach 1:
The current sense circuit employs dynamic switching through the switch network, which dynamically connects either the measurement circuit or emulation circuit output to the sense current output based on the switching cycle phase. This dynamic operation ensures accurate sense signal generation throughout the entire switching cycle, adapting to different operational conditions.
Data Source
AI summary
A DC-DC converter includes a current sense circuit. The current sense circuit includes a sense current output, an inductor current measurement circuit, an inductor current emulation circuit, a first switch, and a second switch. The inductor current measurement circuit has an output. The inductor current emulation circuit has an output. The first switch is coupled between the output of the inductor current measurement circuit and the sense current output. The second switch is coupled between the output of the inductor current emulation circuit and the sense current output.