Design, Analysis, and Verification of a Constant Current Circuit With Settling Time at Microsecond Level for Shape Memory Alloy Actuators

Shape memory alloy (SMA) wire actuators present a viable alternative to conventional pyrotechnic devices in aerospace separation mechanisms due to their low impact, contamination-free operation, and reusability. However, in specialized scenarios, SMA actuators are required to achieve rapid actuation at millisecond-level comparable to pyrotechnic devices. In such scenarios, the use of commercial constant current power supplies, which exhibit settling time at the millisecond level, can introduce inaccuracies that cannot be ignored in evaluating the current-unlock time performance of SMA actuators and analyzing the electric-thermal theory model of SMA wire activated at millisecond level. In this work, we propose a circuit capable of regulating output current within microseconds for ground tests of SMA actuators. A detailed analysis and experimental verification are conducted to determine the key factors affecting the output current settling time. Based on the design, a prototype device has been developed for SMA wire actuators, which can generate a stable current output (∼10 A) within 2 μs in response to the change of control voltage, approximating an ideal step-current output compared to the actuation time (several to tens of milliseconds).