Light control circuit of optical encoder and operating method thereof

A light control circuit of an optical encoder system, the optical encoder system comprising an encoding medium and a light source, the light control circuit comprising:

• a controller, configured to receive a first detected signal, a second detected signal, a third detected signal and a fourth detected signal associated with the encoding medium, and comprising an error amplifier which is configured to control a drive current of the light source, wherein a phase of the second detected signal leads or lags a phase of the fourth detected signal by 90 degrees;
• and
• a frequency detector, configured to
• receive the second detected signal and the fourth detected signal, and
• generate a first output signal, which is configured to change a bandwidth of the error amplifier to regulate a response time of the drive current of the light source, when the phase of the second detected signal leads the phase of the fourth detected signal;
• generate a second output signal, which is configured to change the bandwidth of the error amplifier to regulate the response time, when the phase of the second detected signal lags the phase of the fourth detected signal.

An operating method of a light control circuit of an optical encoder system, the optical encoder system comprising an encoding medium and a light source, and the light control circuit comprising an error amplifier and a frequency detector, the operating method comprising:

• filtering, by the frequency detector, a detected signal associated with the encoding medium to generate a filtered detected signal;
• comparing, by the frequency detector, the filtered detected signal and a first reference voltage to generate a comparison signal;
• comparing, by the frequency detector, another detected signal associated with the encoding medium with a second reference voltage to generate a clock signal, wherein a phase of the detected signal leads or lags a phase of said another detected signal by 90 degrees;
• and
• generating, by the frequency detector, a first output signal according to the comparison signal and the clock signal to change a bandwidth of the error amplifier to accordingly regulate a response time of a drive current of the light source when the phase of the detected signal leads the phase of said another detected signal.