1. A power module comprising:a housing having a first surface, a second surface and a third surface, the second and third surfaces are perpendicularly connected to two opposite edges of the first surface respectively;
a support bracket fixed to the first surface and having a hook member to retain a first side of a support rail;
a sliding member slidably connected to the support bracket, the sliding member has a latch member to retain a second side of the support rail, wherein the first side and the second side are two opposite sides of the support rail; and
a resilient recovery member has a first end connected to the support bracket and a second end connected to the sliding member, the resilient recovery member is configured to push the sliding member to cause the hook member and the latch member to sandwich the support rail,
wherein the sliding member has a first unlocking end and a second unlocking end for applying a force against the resilient recovery member, the first unlocking end projects beyond the second surface, the second unlocking end projects beyond the third surface.