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RD-0608

output stage, such that output current spikes are reduced or eliminated. The presence of such current spikes may

cause the inductor to hum or buzz where the emitted sound will be that of the dimming frequency. The inrush of

current produces mechanical movement in the inductor due to the change in magnetic field, which can be heard

since the PWM signal is within the audible range of the human ear. The effects of adding in Rout can be seen in

Fig. 25 – 28.

Fig. 25 Load Current Spike Excluding Rout

Iout = 350mA, Vin = 100V, Vout = 17V

Fig. 26 Load Current Ripple Excluding Rout

Iout = 350mA, Vin = 100V, Vout = 17V