Printing apparatus and light-emitting element driving device

A printing apparatus comprising:

• a light-emitting element;
• a light-receiving element including a first terminal and a second terminal, driven by a reverse bias voltage applied between the first terminal and the second terminal, and configured to detect a light emission amount of the light-emitting element;
• a reference current generation unit configured to supply a reference current to a current path;
• a comparison unit configured to compare a monitor current with the reference current, the monitor current being supplied to the current path based on a detection amount of the light-receiving element according to the light emission amount;
• a driving unit configured to drive the light-emitting element based on an output of the comparison unit;
• a reference voltage control unit configured to generate a reference voltage selected from at least two voltage values to control a voltage of the second terminal;
• and
• a reverse bias voltage control unit arranged between the second terminal and the comparison unit and configured to receive the reference voltage from the reference voltage control unit and to control the second terminal to a voltage according to the reference voltage,
• wherein the comparison unit comprises a first input terminal connected to the current path.

A light-emitting element driving device comprising:

• a driving terminal configured to output a driving signal used to drive a light-emitting element;
• a monitor terminal configured to receive a monitor current output from a light-receiving element configured to detect a light emission amount of the light-emitting element;
• a reference current generation unit configured to supply a reference current to a node connected to the monitor terminal;
• a comparison unit configured to compare the monitor current input from the light-receiving element to the monitor terminal with the reference current;
• a driving unit configured to generate the driving signal based on an output of the comparison unit;
• and
• a reference voltage control unit configured to control a voltage of the monitor terminal,
• wherein the comparison unit includes a first input terminal connected to the monitor terminal, and a second input terminal, and
• the reference voltage control unit is configured to supply a reference voltage selected from at least two voltage values to the second input terminal, and to control the voltage of the monitor terminal to be a voltage according to the reference voltage.