Patent ID: 8585158
Filing Date: 2013-11-19
Classification: B66B,H02M

Abstract:
1. A brake control circuit comprising: input terminals for receiving DC power from a power source; output terminals for connection to electromagnetic brake that is spring biased to prevent movement when de-energized and that allows movement when energized; a transformer having a primary and a secondary; a semiconductor switch connected in series with the primary between the input terminals; a pulse width modulation (PWM) controller for providing PWM drive pulses to the semiconductor switch; a safety control circuit connected to the input terminals for controlling operation of the PWM controller, the safety control circuit including safety relay contacts connected to control power from the input terminals to the PWM controller, wherein the safety control circuit further includes supervising contacts; and a secondary circuit connected between the secondary and the output terminals for energizing and de-energizing the electromagnetic brake in response to a command signal, the secondary circuit de-energizing the electromagnetic brake to prevent movement when the safety control circuit removes power to the PWM controller.