Thermal analysis of laser diode module by an equivalent electrical network method

Abstract

An equivalent electrical network method is presented in this paper to analyze the cooling characteristics of a laser diode module (LDM). And a modified equivalent model of a thermoelectric cooler (TEC) with an adjunctive thermal resistance and a contact resistance is proposed. The performance of a commercial TEC has been simulated. The thermal analysis of a LDM incorporated with a TEC has been performed by using an equivalent circuit model of the LDM. In the analysis the change of LD current, TEC current,and the ambient temperature are all considered. It shows that the equivalent circuit approach is an effective tool for the qualitative analysis of TEC and LDM. Heat generation and dissipation in LD packages without TEC have been investigated both analytically and experimentally [14]. However, the thermal analysis of LDM incorporated with a TEC has not yet been sufficiently investigated. A finite element method to analyse a LDM has been presented in reference [5][6]. These works were only primary and the method suffers from a great limitation that its operation can not be modeled in CFD or ANSYS software directly since TEC's performance does not obey standard rules of conduction. In addition, the method is complex and all internal characteristics of the device have to be known.In this paper an equivalent electrical network method is presented to analyze the cooling and heating characteristics of a LDM. Following an approach similar to reference[7-1 and considered the adjunctive thermal resistance and the contact resistance, a modified equivalent model of a TEC is also presented. Then an equivalent circuit model of LDM incorporated with a TEC is developed in order to understand the thermal behavior of a LDM. The thermal analysis of a LDM is performed through the circuit model.A typical LDM is shown in Fig. 1. As an important part of the thermal management of optical package, a TEC is commonly used for cooling, heat pumping and maintaining the LI~s operating temperature. A negative temperature coefficient thermistor (NTC) mounted near the LD chip is used to monitor the chip temperature (not shown in Fig. 1). The NTC resistance decreases with increasing temperature. As the temperature inside the laser changes, the NTC resistance change is translated into the supply of current to the TEC.The exothermic heat of the LD is the Joule heat gen-* E-mail: mingwei_dlmu@ sina. com~ yangmingwei@ hit. edu. cn where Rm is the resistance of the LD. The internal heat convection and thermal radiation are ignored. A TEC relies on the Peltier effect and directly uses electrical energy for cooling and heating. A TEC consists of many arrays of positively-doped (p-type) and negatively doped (n-type) semiconductor pellets connected electrically in series and thermally in parallel between ceramic substrates. Each adjacent pair of p-type and n-type pellets is referred to as a thermocouple and there are N thermocouples in a TEC. A single-stage TEC is shown in Fig. 2 which only shows a single thermoeouple.Here, the controlled and uncontrolled...

High‐accuracy thermoelectrical module model for energy‐harvesting systems

“…Modelling (6)- (9) has been made in [4][5][6] by using currentand voltage-dependant sources. Our own model employs the S, k and R m parameters variation with temperature and is built using Linear Technology's LTspice simulator.…”

“…In [4][5][6] the authors have already proposed a SPICE thermoelectrical model that starts from the equilibrium equation of the energy flow through a unit of volume [20] TJ…”

“…Some authors [4][5][6] have already implemented thermoelectric models, but they used only the manufacturer's datasheet constant parameters when building their models. In reality these parameters vary strongly with temperature as our experiments demonstrated [7], resulting in erroneous simulation results.…”

Parasitic elements modelling in thermoelectric modules

“…Equations (9)- (12) were used in [11,12] to create a thermoelectric model of the TEM. In this model, the hot and cold side temperatures are following the applied voltage regardless of the input frequency.…”

“…Up to the moment the current paper was written, no SPICE models employing the parasitic components were found by the authors. The existent models [10][11][12][13][14][15][16] only take into account the internal resistance, Seebeck coefficient and thermal conductivity.…”