A foldable walker includes upstanding legs arranged in a generally square pattern, each of which is capped by a fixed joint member and each of which has a slider member slideably disposed on it. The method includes the steps of outputting a plurality of link pulses, asserting a plurality of disabling signals between two adjacent link pulses for disabling the sub-circuits, respectively, and deasserting the disabling signals for enabling the sub-circuits, respectively. A first switch switchably provides a drive output signal to the transformer based upon a switch input signal.