High Side Low Side Current Sensing Circuit Mirroring
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Solution Overview
Problem
Current sensing in switched mode power converters lacks accuracy and bandwidth, particularly in high side and low side current sensing, which affects the regulation and monitoring of output voltage.
Innovation Solution
A current sensing circuit is designed with mirroring circuitry and coupling switches to accurately sense high side and low side currents, using operational amplifiers and sensing resistors to mirror voltage drops and pre-bias the sensing circuits, thereby enhancing accuracy and bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current sensing circuits are used in switched mode power converters, then the circuit structure is simple, but the sensing accuracy and bandwidth are insufficient
Solution Approach 1:
The current sensing circuit is divided into separate high-side sensing and low-side sensing paths, each with dedicated mirroring circuitry. This segmentation allows independent optimization of each sensing path for accuracy while maintaining manageable circuit complexity through modular design
Solution Approach 2:
Mirroring circuitry is introduced as an intermediary element between the current sensing nodes and the output. This mirroring mechanism transforms the voltage drops across switches into accurate current representations, significantly improving sensing accuracy without directly increasing the complexity of the core sensing function
2Speed
If conventional current sensing circuits are used, then the circuit occupies less space, but the bandwidth and convergence speed are limited
Solution Approach 1:
The mirroring circuitry is pre-configured with coupling switches that can rapidly switch between high-side and low-side sensing modes. This preliminary configuration allows the circuit to quickly converge to the correct sensing state when switching between different operational phases, significantly improving bandwidth and convergence speed
Solution Approach 2:
The sensing circuit is designed with multi-functional capability to handle both high-side and low-side current sensing through the same output node. The coupling switches enable the circuit to universally sense currents from either switch, improving speed by eliminating the need for separate dedicated sensing paths while managing area through shared components
3Measurement precision
If separate high side and low side sensing circuits are implemented, then the sensing accuracy improves, but the offset and space requirements increase
Solution Approach 1:
The high-side and low-side sensing circuits are merged to share a common output node and mirroring circuitry. By combining the sensing paths while maintaining separate sensing capabilities through coupling switches, the design achieves high sensing accuracy for both switches while reducing the total component count and space requirements compared to completely separate circuits
Data Source
AI summary
A current sensing circuit is described. The current sensing circuit is for sensing a high side current through a high side switch and/or for sensing a low side current through a low side switch of a half bridge comprising the high side switch and the low side switch, which are arranged in series between a high side potential and a low side potential. The high side switch and the low side switch are in respective on-phases in a mutually exclusive manner. The high side sensing circuit comprises mirroring circuitry to mirror a current from a first node of the high side sensing circuit to an output node of the high side sensing circuit. The current sensing circuit comprises a low side sensing circuit to provide a sensed low side current which is indicative of the low side current during an on-phase of the low side switch.