Servo motor drive amplifier
Posted on Feb 4, 2013 3310
Digital ICs and opto-isolators provide the drive for this TMOS servo amplifier, resulting in fewer analog circuits and less drift. Fast and consistent turn-on and turn-off characteristics also enable accurate analog output results directly from the digital signal without the need for analog feedback. An `H` bridge configuration is employed for the servo amplifier, which obtains complementary PWM inputs from digital control circuits. The PWM inputs are applied via opto-isolators, which keep the digital control logic isolated from the 75 V supply used for the amplifier.
A short circuit indicator is provided by opto-isolator U3 if there is a short, the drop across R9 increases to a value sufficient to activate the isolator and send a short indication to the digital control logic.