Color TV infrared remote control receiving circuit

The infrared remote control receiving
circuit of the TV is shown in the figure. It is composed of an infrared receiving diode, CX 20106 preamplifier integrated circuit and peripheral components. The infrared receiving diode VDI is a PN photodiode. When there is no light, VD1 is reverse-biased and has no current;
when there is infrared light, VDI generates a photocurrent, which is input to the first pin of CX 20106. On the input impedance of the amplifier An optical signal
voltage is formed. CX 20106 is equipped with preamplifier, limiting amplification, filtering, detection and shaping circuits inside.
There is also an automatic brightness control circuit ABLC at the input end of the preamplifier circuit to prevent the input signal from being too large and overloading the amplifier. . The remote control signal emitted
    from the infrared remote control circuit is a modulated 38 kHz pulse signal. This signal is detected by the VDI. After amplification and
limiting, the stray modulation interference is eliminated, and then the stronger signal is sent to the center frequency. is a 38 kHz bandpass filter.
R2 is connected to the external circuit of the bandpass filter . Adjusting the resistor value can make the center frequency of the filter change within the range of 30 to 60 kHz. The signal output by the filter is detected and
the command code pulse is obtained, and then integrated and shaped. Finally, the command code pulse is output by the ⑦ pin of CX 20106. After the instruction code pulse
is processed by the microprocessor, the corresponding execution command will be issued.