Optical transmitter with forward controlled peltier device

Abstract

The present invention provides an optical transmitter with a forward controlled Peltier driver. The temperature sensor generates a monitoring signal Sm. The comparator compares this monitored signal Sm with the target temperature signal St to generated the temperature difference signal Sn. The limiter restricts this difference signal Sn between the positive and negative maximum of the periodic signal Sw to generate the limiting signal Sa. The second comparator compares this limiting signal Sa with the periodic signal Sw to generate the control signal. The PWM signal generator, responding to this limiting signal Sa, generates a plurality of PWM signals, Sg 1 to Sg 4. The H-bridge including four transistors and two inductors, responding to this PWM signals, controls the direction of the current flowing in the Peltier device. The magnitude of the current can be determined by the duty ratio of the PWM signals.

1 . An optical transmitter with a forward controlled Peltier device, comprising: 
 a light-emitting device, a temperature of said light-emitting device being controlled by said Peltier device;    a temperature sensor for monitoring a temperature of said light-emitting device and outputting a monitored signal; and    a controller for controlling said temperature of said light-emitting device by receiving said monitored signal output from said temperature sensor,    wherein said controller forwardly controls said temperature of said Peltier device without any sensing resistor connected in series to said Peltier device for sensing a current flowing in said Peltier device.    
   
   
       2 . The optical transmitter according to  claim 1 , 
 wherein said controller includes a first comparator and a limiter, said first comparator comparing said monitored signal with a target signal corresponding to a target temperature of said light-emitting device and outputting a temperature difference signal denoting a temperature difference between said monitored temperature of said light-emitting device and said target temperature, and said limiter cramping said temperature difference signal between a preset maximum value and a preset minimum value.    
   
   
       3 . The optical transmitter according to  claim 2 , 
 wherein said limiter outputs said preset maximum value when said temperature difference signal is greater than said preset maximum value and outputs said preset minimum value when said temperature difference signal is smaller than said preset minimum value.    
   
   
       4 . The optical transmitter according to  claim 1 , 
 wherein said controller includes a second comparator for comparing said temperature difference signal with a periodic signal with a triangular shape having a positive peak value greater than said preset maximum value and a negative peak value smaller than said preset minimum value, and for outputting a pulse width modulation signal with a pulsed shape, said pulse width modulation signal being generated by slicing said periodic signal by said temperature difference signal.    
   
   
       5 . The optical transmitter according to  claim 1 , 
 wherein said controller includes a switching ladder including a pair of two switches, each switches including a pair of switching devices operated in complementary, said Peltier device being connected between said pair of two switches through a low pass filter including an inductor and a capacitor such that a direction of current flowing in said Peltier device is altered by switching said pair of two switches in complementary.    
   
   
       6 . An optical transmitter having a semiconductor light-emitting device and an forward controlled Peltier device without any sensing resistor for monitoring an current flowing in said Peltier device, said Peltier device controlling a temperature of said light-emitting device, said optical transmitter comprising: 
 a temperature sensor for monitoring said temperature of said light-emitting device, and for outputting a temperature-monitored signal; and    a controller for controlling a current flowing in said Peltier device, said controller including,    a first comparator for comparing said temperature-monitored signal with a target temperature signal denoting a target temperature for said light-emitting device, and for generating a temperature difference signal,    a limiter for cramping said temperature difference signal between a preset maximum value and a preset minimum value,    a second comparator for slicing a periodic signal by said temperature difference signal, said periodic signal having a triangular waveform with a positive peak value greater than said preset maximum value and a negative peak value smaller than said preset minimum value, and for outputting a control signal with a pulsed wave form, and    a switching ladder including a pair of two switches each having two switching devices operating in complementary, said Peltier device being connected between said two switches through a low pass filter including an inductor and a capacitor, said switches being driven by said control signal and another control signal complementary to said control signal.