SEMICONDUCTOR LASER MODULE, DRIVING METHOD OF SEMICONDUCTOR LASER MODULE AND COMMUNICATION EQUIPMENT USING SEMICONDUCTOR LASER MODULE

PROBLEM TO BE SOLVED: To suppress the passage of anaovercurrent through a thermomodule. SOLUTION: A thermomodule 5 performs a heating operation when a current in the direction to turn from a lead pin 16f to a lead pin 16a is passed through the thermomodule 5 and to the contrary, the thermomodule 5 performs a cooling operation when a current in the direction to turn from the lead pin 16a to the lead pin 16f is passed through the thermomodule 5. An overcurrent limiting circuit 20 for suppressing the passage of an overcurrent in the heating direction through the thermomodule 5 is provided. The circuit 20 has a by-pass passage 21, a Zener diode 22 and a diode 23 and the Zener diode 22 and the diode 23 are reversely connected with each other. When a current in the heating direction is passed through the thermomodule 5, the diode 23 turns on and when the Zener voltage of the Zener diode 22 exceeds its set value, the current is shunted into the thermomodule 5 and the passage 21 to flow. Hereby, the passage of the overcurrent through the thermomodule 5 can be suppressed.