Photo-sensing pixel circuit with conversion gain adjustment unit and image sensor

A photo-sensing pixel circuit, comprising:

• a photo-sensing part, sensing a light source, and generating a corresponding number of electrons;
• a signal conversion unit, coupled to the photo-sensing part, having a floating node, and converting the electrons into a voltage signal according to a conversion gain, the signal conversion unit comprising:
• a row select transistor, coupled to a source follower and an output circuit, and transmitting an amplified voltage signal to the output circuit, wherein the output circuit is coupled to a transfer transistor via the source follower and the row select transistor;
• a conversion gain adjustment unit, coupled to the signal conversion unit via the floating node, and adjusting the conversion gain;
• and
• the output circuit, coupled to the signal conversion unit, and outputting a sensing signal according to the voltage signal, wherein the sensing signal corresponds to the brightness of the light source,
• wherein the conversion gain adjustment unit operates in at least two operation modes, and a conversion gain in one of the operation modes is greater than a conversion gain in the other operation mode,
• wherein the conversion gain adjustment unit has a first end and a second end, the first end is coupled to a first power supply, and the second end is coupled to the floating node,
• wherein the conversion gain adjustment unit comprises:
• coupled between the first end and the second end, wherein the number of adjustment transistors is three or more, and wherein different numbers of the adjustment transistors are turned on in different ones of the operation modes, and the conversion gain of the signal conversion unit is adjusted according to the number of the adjustment transistors that are turned on,
• wherein the photo-sensing pixel circuit further comprises:
• a control unit, coupled to the output circuit, and adjusting the number of the adjustment transistors that are turned on according to the brightness of the light source corresponding to the sensing signal.