Switch-mode bi-directional thermoelectric control of laser diode temperature

Abstract

A system for actively heating and cooling an object contains a thermoelectric device having a Peltier junction. The system is capable of reversing the direction of DC current flow through the Peltier junction so that the thermoelectric cooler/heater either heats or cools the object, as selected. The DC power supply is preferably operated in switch-mode. The thermoelectric device is disposed in a laser diode module or in heat-conductive contact with a laser housing mounting plate in a high-density laser source bank.

1 . A system for heating and cooling an object, comprising: 
 a first thermoelectric cooler/heater having a Peltier junction between a first contact and a second contact;    a switch-mode power supply electrically connected to the first contact and the second contact, configured for flowing electrical current through the Peltier junction; and    a polarity controller configured for controlling the direction of electrical current flow through the Peltier junction.    
     
     
         2 . The system as set forth in  claim 1 , wherein the switch-mode power supply is configured to provide DC current.  
     
     
         3 . The system as set forth in  claim 1 , wherein the switch mode power supply is configured to provide pulse-modulated current.  
     
     
         4 . The system as set forth in  claim 3 , including a filter for use in smoothing the pulse-modulated current.  
     
     
         5 . The system as set forth in  claim 4 , wherein the filter is a capacitive filter.  
     
     
         6 . The system as set forth in  claim 5 , wherein the capacitive filter comprises an inductor preceding a capacitor.  
     
     
         7 . The system as set forth in  claim 1 , wherein the object comprises a laser diode contacting the first thermoelectric cooler/heater.  
     
     
         8 . The system as set forth in  claim 7 , comprising a heat conductive block contacting the first thermoelectric cooler/heater, and a second thermoelectric cooler/heater contacting the heat conductive block.  
     
     
         9 . The system as set forth in  claim 8 , including control circuitry operable to maintain each of the first and second thermoelectric cooler/heaters at different temperatures during system operation.  
     
     
         10 . The system as set forth in  claim 1 , comprising a closed loop feedback system including a temperature sensor contacting the object and configured to provide an input signal useful for controlling system temperature.  
     
     
         11 . The system as set forth in  claim 10 , wherein the temperature sensor comprises a thermistor and the input signal comprises a thermistor voltage signal.  
     
     
         12 . The system as set forth in  claim 11 , including an error amplifier that operates by comparing the thermistor voltage signal against a reference voltage representing a desired control temperature.  
     
     
         13 . The system as set forth in  claim 12 , comprising a digital to analog converter configured to provide the reference voltage.  
     
     
         14 . The system as set forth in  claim 1 , wherein the control circuitry includes a thermal process controller adapted to operate on a temperature signal.  
     
     
         15 . The system as set forth in  claim 14 , wherein the thermal process controller comprises a PID controller.  
     
     
         16 . The system as set forth in  claim 14 , wherein the thermal process controller comprises a PI controller.  
     
     
         17 . The system as set forth in  claim 1 , including a polarity control bridge adapted to electrically activate the thermoelectric cooler/heater based upon output from the polarity controller.  
     
     
         18 . The system as set forth in  claim 17 , wherein the polarity control bridge comprises an H-bridge.  
     
     
         19 . The system as set forth in  claim 1 , wherein the control circuitry includes a thermistor, an error amplifier, a thermal process controller, and a polarity control bridge forming a first loop.  
     
     
         20 . The system as set forth in  claim 19 , wherein the switch-mode power supply is connected to the polarity control bridge for supply of power thereto.  
     
     
         21 . The system as set forth in  claim 20 , comprising an absolute value circuit positioned between the thermal process controller and the switch-mode power supply to form a second loop which is a subset of the first loop.  
     
     
         22 . The system as set forth in  claim 21 , comprising a third loop including means for providing feedback based upon output of the switch-mode power supply, the third loop being operable to adjust the output of the switch mode power supply according to output from the thermal process controller.  
     
     
         23 . The system as set forth in  claim 1  including process control circuitry configured to adjust power output of the switch-mode power supply based upon a first input signal from a first feedback loop.  
     
     
         24 . The system as set forth in  claim 23 , wherein the first feedback loop is a temperature feedback loop and the input signal is a voltage signal based upon a temperature of the object.  
     
     
         25 . The system as set forth in  claim 1 , wherein the process control circuitry is configured to adjust power output of the switch-mode power supply based upon a second input signal from a second feedback loop.  
     
     
         26 . The system as set forth in  claim 25 , wherein the second feedback loop operates by comparing actual output and intended output of the switch-mode power supply, and by adjusting power output of the switch-mode power supply to meet the intended output.  
     
     
         27 . The system as set forth in  claim 1 , comprising a laser diode as the object, the laser diode and system being mounted on a modular card, and a plurality of such modular cards mounted adjacent to one another in a total number not less than twenty modular cards, the modular cards being identical to one another except that the laser diodes may emit light at different wavelengths.  
     
     
         28 . A system for heating and cooling an object, comprising: 
 a thermoelectric cooler/heater having a Peltier junction between a first junction contact and a second junction contact;    a switch-mode power supply electrically connected to the first junction contact and the second junction contact, for flowing electrical current through the thermoelectric cooler/heater through the Peltier junction;    a thermistor for converting a temperature of the object to a thermistor voltage;    an error amplifier for comparing the thermistor voltage to a reference voltage and producing an error voltage;    a PID controller for processing the error voltage and producing a PID signal;    an absolute value circuit for converting the PID signal to a negative feedback value for input to the switch-mode power supply;    an H-bridge for reversing the direction of current through the Peltier junction;    a polarity controller for sensing the polarity of the PID signal and controlling the H-bridge; and    a current-voltage amplifier for converting the electrical current that flows through the thermoelectric cooler/heater into a feedback signal for use in controlling the output of the switch mode power supply.    
     
     
         29 . A two-stage thermoelectric temperature control system for controlling the temperature of a laser diode, comprising: 
 a laser housing containing a laser diode device; and    a first switch-mode bi-directional thermoelectric cooler/heater disposed in contact with the laser housing and heat-conductively connected to the laser diode device.    
     
     
         30 . The two-stage thermoelectric temperature control system as set forth in  claim 29 , comprising: 
 a heat-conducting mount on which the laser housing is mounted; and    a second switch-mode bi-directional thermoelectric cooler/heater mounted on the mount.    
     
     
         31 . A thermoelectrically controlled high-density laser source bank, comprising: 
 a plurality of laser diode source modules, each laser diode source module containing a laser diode and a switch-mode bi-directional thermoelectric cooler/heater having a Peltier junction.    
     
     
         32 . The thermoelectrically controlled high-density laser source bank as set forth in  claim 31 , wherein each laser diode source module includes: 
 a laser housing containing a laser diode device;    a first switch-mode bi-directional thermoelectric cooler/heater disposed in contact with the laser housing and heat-conductively connected to the laser diode device;    a heat-conducting mounting block, on which the laser housing is mounted; and    a second switch-mode bi-directional thermoelectric cooler/heater mounted on the mounting block.    
     
     
         33 . A method of stabilizing temperature in a system having a first Peltier junction thermoelectric cooler/heater, the method comprising the steps of: 
 sensing the temperature in the system to provide a temperature signal corresponding to the temperature; and    selectively activating the first Peltier junction thermoelectric cooler/heater for heating and cooling purposes to maintain the temperature within a predetermined temperature range based upon the temperature signal,    wherein the step of selectively activating the first Peltier junction thermoelectric cooler/heater includes utilizing a switch-mode power supply.    
     
     
         34 . The method according to  claim 33 , wherein the system includes a laser diode and the step of sensing the temperature includes sensing the temperature of the laser diode.  
     
     
         35 . The method according to  claim 34 , including a step of performing optical telecommunications test operations by energizing the laser diode concomitantly with the steps of sensing temperature and selectively activating the first Peltier junction thermoelectric cooler/heater.  
     
     
         36 . The method according to  claim 34 , wherein the system includes a heat sink contacting the laser diode and an additional thermoelectric heater/cooler, the method comprising an additional step of selectively activating an additional Peltier junction thermoelectric cooler/heater.  
     
     
         37 . The method according to  claim 36 , wherein the additional step of selectively activating the additional Peltier junction thermoelectric cooler/heater includes maintaining the first Peltier junction thermoelectric cooler/heater and the additional Peltier junction thermoelectric cooler/heater at different temperatures.  
     
     
         38 . The method according to  claim 34 , wherein the step of sensing temperature comprises sensing temperature from a structure selected from the group consisting of a laser diode and a laser diode module.  
     
     
         39 . The method according to  claim 34 , wherein the step of sensing temperature comprises using a thermistor to provide the temperature signal.  
     
     
         40 . The method according to  claim 34 , wherein the system includes a thermistor for converting a temperature of the object to a thermistor voltage, and the step of sensing the temperature comprises using the thermistor to provide the temperature signal.  
     
     
         41 . The method according to  claim 40 , wherein the system includes an error amplifier, and the method includes a step of comparing the temperature signal to a reference signal to produce an error output signal.  
     
     
         42 . The method according to  claim 41 , wherein the step of selectively activating the Peltier junction thermoelectric cooler/heater comprises integrating the error output signal to provide and integrated value and providing control signals for use in heating and cooling operations based upon the integrated value.  
     
     
         43 . The method according to  claim 34 , wherein the step of selectively activating the Peltier junction thermoelectric cooler/heater comprises converting the integrated value into an absolute value for use as control input to a switch mode power supply.  
     
     
         44 . The method according to  claim 34 , wherein the step of selectively activating the Peltier junction thermoelectric cooler/heater comprises adjusting output of the switch mode power supply based upon a feedback comparison between desired output and actual output.  
     
     
         45 . The method according to  claim 45 , wherein the step of selectively activating the Peltier junction thermoelectric cooler/heater comprises adjusting output of the switch mode power supply based upon a feedback comparison between actual and desired temperature of the object.