TWH8778 radio automatic shutdown circuit

Published:2011/7/7 7:09:00 Author:Fiona | Keyword: radio automatic shutdown, sound signal | From:SeekIC

The circuit mainly uses a new type of power switching device TWH8778.It produces simply and has no debugging.TWH8778 shape and the function of the pins is shown as above,the ⑤ pin is control side,when the pin's voltage is higher than the cut-in voltage (about 1.6V), the electronic switch is closed, ①, ② pins are connected. When touching the contact of the touch switch between BG1 and the power,BG1 is conducted,the voltage drop of R1 makes TWH8778 close,the recorder works normally due to the power is connected.If the recorder is on playback, thesound signal is coupled by C3 to the base of BG3 to make BG2 conduct,BG2 has a base current and it is in the conduction state,the voltage drop of R1 makes TWH8778 close again.



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