A novel operating mode of thermoelectric module (TEM, cooling, heating, generation) is established for electronic devices cooling, based on the method of effectiveness-number of transfer units (epsilon - NTU). This work mainly focused on the effect of thermoelectric properties and the scale of extender block on cooling performance under different operating conditions in order to obtain effective cooling operating mode. Based on the TEM parameters, two sets of analytical solutions for thermoelectric cooler (TEC) are derived for the chip temperature T-j at a fixed cooling power Q(c) and Q(c) at a fixed T-J respectively. The performance of TEC with without scale of extender block is studied for the lowest chip temperature and maximum cooling capacity at fixed conditions. Analysis results show the thermoelectric properties and extender block are significant characteristics for different operating conditions. However, the coefficient of performance (COP) and temperature difference changed a little under given thermoelectric properties. The results indicate TEC system applied in electronic devices obtains effectively cooling module by controlling operating parameters, which do not changed with scale of extender block. The validation of the present analysis is also conducted compared with previous studies and through the infrared thermal imager. (C) 2016 Elsevier Ltd. All rights reserved.