The influence of heat effect at work of semiconductor laser crystal is very sensitive

so the request of the temperature of the laser crystal is very important.A kind of the improved circuit of pulse width modulating is designed

which adopts the method of the figure combining with simulation circuit

through changing the width of pulse and amplitude of the voltage of output to control the direction and size of the electric current

then different output power in the output end can be received.In this way

the output power of the semiconductor refrigeration device（TEC）can be controlled to realize the thick mediation of the temperature which makes TEC intensify or lower the temperature fast to adjust thickly

and the finely tune of the temperature which makes the system reach the dynamic stability finally.