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Application Report
SPRA873 - February 2003
1
Thermoelectric Cooler Control Using a TMS320F2812 DSP
and a DRV592 Power Amplifier
David M. Alter, Ph.D. DSP Applications - Semiconductor Group
ABSTRACT
This application report presents a thermoelectric cooler system consisting of a Texas
Instruments TMS320F2812 digital signal processor (DSP) and DRV592 power amplifier.
The DSP implements a digital proportional-integral-derivative feedback controller using an
integrated 12-bit analog-to-digital converter to read the thermistor, and direct output of
pulse-width-modulated waveforms to the H-bridge DRV592 power amplifier. The system
presented provides up to 6.1 watts of heating or cooling to the laser mount, although the
DRV592 amplifier is actually capable of delivering up to 15 watts when configured
appropriately. The closed-loop TEC system is seen to achieve ±0.0006
°C temperature
accuracy, depending on the needed operating temperature range, with a step response
settling time of 14 to 16 seconds. A complete description of the experimental system, along
with software and software operating instructions, are provided.
Contents
1 Introduction...................................................................................................................................2
2 Discrete-Time PID Controller .......................................................................................................4
2.1 Mathematical Formulation.......................................................................................................4
2.2 Implementation Issues............................................................................................................6
3 Experimental Setup ......................................................................................................................6
3.1 eZdsp F2812 Board ................................................................................................................8
3.2 TCLMD9 Laser Diode Mount...................................................................................................9
3.2.1 Peltier Elements ..........................................................................................................9
3.2.2 Thermistor...................................................................................................................9
3.3 Instrumentation Board...........................................................................................................10
3.3.1 Whetstone Bridge......................................................................................................11
3.3.2 INA122P....................................................................................................................12
3.4 DRV592 Evaluation Module..................................................................................................13
3.5 Benchtop Power Supply........................................................................................................17
4 Software ......................................................................................................................................17
4.1 File Descriptions ...................................................................................................................17
4.2 Code Overview .....................................................................................................................19
4.3 Running the Software............................................................................................................21
4.4 Using the GEL File realtime.gel.............................................................................................24
5 Controller Performance..............................................................................................................25
5.1 Case 1: K
p
= 750, K
’
i
=0.4,K
’
d
= 125000...............................................................................25
5.2 Case 2: K
p
= 750, K
’
i
=0.3,K
’
d
= 300000...............................................................................27
5.3 DSP MIPS Requirements......................................................................................................28
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