Magnetic Interference Suppression of Tunnel Magnetoresistance Current Sensor in Power Converters

Abstract

Tunnel magnetoresistance (TMR) sensor is a promising candidate for current sensing with non-invasively measuring and very small footprint. However, in power converter products, the surrounding PCB tracks and magnetic components will generate magnetic fields, thereby affecting the current sampling accuracy of the TMR. This paper analyzes the influence of parallel and crossed PCB track currents and magnetic components in the power converter on the TMR measurement results and proposes methods to suppress magnetic field interference. For parallel PCB tracks, the design of spacing is used to reduce the interference, and the calculation of minimum spacing is given. A reasonable crossing angle design can reduce the crossed conductors' magnetic interference. For magnetic components, this paper selects the optimal installation position and layout to improve the detection accuracy of TMR. A prototype was built to demonstrate the feasibility of the proposed methods. With the optimized layout, the interference from parallel PCB tracks, cross tracks and magnetic components can be effectively suppressed, and the measured interference ratios are all within 5%.