Dual pulse width modulated driver for thermo-electric cooler

Abstract

A dual pulse width modulated driver controls the operation of a thermo-electric cooler for stabilizing the operating temperature of a laser. The pulse width modulator has complementary outputs coupled to control inputs of dual pairs of complementary polarity electronic switching elements, that are coupled in circuit between first and second power supply terminals, and a pair of output nodes. The output nodes are coupled in common through a low pass filters to drive terminals of a thermoelectric cooling element. The thermal output generated by the thermoelectric cooling element is coupled to the laser. The thermal output of the cooling element is monitored by a temperature sensing element mounted with the laser and provides an output voltage in linear proportion of its thermal input. This output voltage is fed back through a temperature control servo loop to a differential summing circuit, which is also coupled to receive a reference voltage used to control the duty cycle of the pulse width modulator. The output of the differential summing circuit is filtered through a low pass loop filter to eliminate the modulator's switching frequency component in the voltage fed back from the thermistor.