| 摘要 |
<p>PURPOSE:To detect the current of a high voltage portion and measure an efficiency by providing voltage detecting means for detecting a voltage proportional to a voltage generated in a primary winding and means for calculating the efficiency on the basis of a value detected by the voltage detecting means. CONSTITUTION:A screen grid current Isg is converted to a 30KHz signal in a high voltage resistant current sensor 1 by a signal from an oscillator 10, inputted to a port 303 and then to a subtraction circuit 8 via a rectifying amplifier 7. Therefore, a signal representative of a current Ik-Isg is outputted from the subtraction circuit 8 and inputted to a subsequent subtraction circuit 9. A grid current Ig is inputted to a port 305 via a similar high voltage resistant current sensor 2, converted to DC current signals in a rectifying amplifier 11 and inputted to the subtraction circuit 9. The output of the oscillator 10 is applied to the high voltage resistant current sensors 1 and 2 from a port 304. The output of the circuit 9 is made Ik-Isg-Ig to be inputted to an efficiency calculating circuit 5. The circuit 5 is inputted with If from a mean value circuit 4 and If-Isg-Ig from the subtraction circuit 9 and outputs a signal indicative of a broadcasting apparatus efficiency from a port 306 to a display unit (electronic meter) 12.</p> |
