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Power Efficiency Improvement for Low Ohm Current Sense Resistor by Optimum Thermal Management
Keywords: Efficient Thermal Dispersion, Improve Rated Power, Current Sense Resistor
To improve power efficiency, design engineers need to detect current throughout the circuit to minimize power loss. Low ohm current sense resistors are used to detect current to measure and monitor power. These components need to handle higher power to achieve optimal performance. In this work, we extensively studied to improve the power handling capability of low ohm current sense resistors while maintaining smaller size. We optimized power dissipation by applying innovative thermal management techniques. Employing novel packaging technique, we optimized heat dispersion and minimized the peak surface temperature rise. Using proprietary thermal protection material, we avoided direct heat transfer from component to PC board and minimize the risk of thermal damage against PCB and extreme thermal cycle. We extensively discussed the thermal fatigue of resistor termination structure. Solid metal package construction leads to solder cracks due to thermal fatigue, hence decreases resistor reliability. We improved the packaging footprint and significantly reduced the chance of solder cracking. We optimized the resistor structure for current sensing and shunting purpose. We laid out electrodes and termination in parallel and minimized the contact resistance. By improving the packaging and design, we maintained industry's lowest ESL. Reduced ESL improved I/V conversion coefficient and we achieved ideal I/V conversion for desired current detection. We investigated several techniques to improve the efficiency while product is used for current and voltage measurement. By laying out the resistor as four terminals, we separated current and voltage measurement terminals; resulting separation of contact and line resistance from the intended resistance. Consequently, we reduced the power loss through the resistor and improved the efficiency of voltage and current measurement. Considering these parameters, we manufactured low ohm current sense resistor of 0.5 milli ohm to 100 mili ohm values with up to 5W rated power with tolerance as low as 0.5%.
Akhlaqur Rahman, Product Development Engineer
Thin Film Technology Corporation
North Mankato, MN

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