| 摘要 |
<p>ISOLATION CIRCUIT WITH DUTY CYCLE FEEDBACK An isolation circuit with duty cycle feedback is disclosed which includes an operational amplifier with capacitive coupled negative feedback such that its output voltage varies to maintain its input terminals at the same potential, and which output is connected to the control terminal of a voltage controlled oscillator which generates a square wave voltage in which the ratio of ON time to the total period is directly related to the voltage from the operational amplifier. The output pulses of the voltage controlled oscillator are fed through a resistor to the negative input terminal of the operational amplifier. The output pulses from the oscillator are also fed through a driver transistor to control the input of an opto-coupler. The output from the opto-coupler passes through an amplifier to produce a square wave voltage with the same ON time ratio as the voltage controlled oscillator. The average value of this square wave voltage is obtained by a low pass filter and is directly proportional to the input analog voltage.</p> |
