Schallrauschmaskierung im Steuerung eines H-Brücke

摘要

Masking of switching noise is implemented in the driving system of an "H" bridge stage by exploiting the periodic signal generated by a PWM control circuit (normally present in the control system for controlling the "H" bridge in an open-loop mode) for masking the decay time of the disturbances caused by the switching from off-to-on of a first pair of switches of the bridge that drive a current in a certain direction through the load. This is implemented by keeping high for a preset period of time the periodic signal generated by the PWM circuit and varying the duty-cycle of the signal for regulating the mask time in function of the load characteristics. The system further comprises the masking of the decay interval of the disturbances caused by the switching from on-to-off of the first pair of switches and from off-to-on of the other pair of switches that provide a current ricirculation path of the energy stored in the reactance of the load, for a preset number of clock cycles, thus impeding any subsequent switching for the duration of this second mask. This second mask may be realised in different ways. The use of an up-counter and a programmable comparator been preferred.