DIMMER FOR PREVENTING ASYMMETRIC CURRENT FLOW THROUGH AN UNLOADED MAGNETIC LOW-VOLTAGE TRANSFORMER

摘要

A two-wire dimmer is operable to control the amount of power delivered to a magnetic low-voltage (MLV) load and comprises a bidirectional semiconductor, a timing circuit, a trigger circuit having a variable voltage threshold, and a clamp circuit. When a timing voltage signal of the timing circuit exceeds an initial magnitude of the variable voltage threshold, the trigger circuit is operable to render the semiconductor switch conductive, reduce the timing voltage signal to a predetermined magnitude less than the initial magnitude, and to increase the variable voltage threshold to a second magnitude greater than the first magnitude. The clamp circuit limits the magnitude of the timing voltage signal to a clamp magnitude between the initial magnitude and the second magnitude, thereby preventing the timing voltage signal from exceeding the second magnitude. Accordingly, the MLV dimmer is prevented from conducting asymmetric current when an MLV transformer of the MLV load is unloaded.