3.8  Temperature sensors

To protect the power devices from over - heating, temperature measurement must be implemented at the IGBT-driver-chip, the IGBTs and at the first stage of the cascade. Analog Devices provides an integrated circuit (TMP01) with two programmable TLL compatible outputs. Combined with a small circuit (Figure 3.41), a temperature controlling element is formed. The 'under' - output is used to control a fan, the 'over' - output is used to control the shutdown of the voltage multiplier if an over temperature occurs. The green LED is emitting as long as the temperature is below T_{fan on}. The red LED is on when the temperature is higher then T_{circuit off}.

Figure 3.41: Protel Schematic: Temperature Controller

Analog Devices offers a pc-program for calculating the resistor - values (R1, R2, R3) on their web site.

The first setting:

            T_{fan on}              =          60ºC

            T_{circuit off}          =          90ºC

            T_hysteresis        =          20ºC

calculates resistor - values as shown in Figure 3.42. These resistor - values are not common, so a second calculation with values from the E12 standard-resistor-table is shown in Figure 3.43. The resulting temperature trip points are:

            T_{fan on}              =          48.7ºC

            T_{circuit off}          =          80.9ºC

            T_hysteresis        =          20.1ºC

Figure 3.42: Analog Devices Program: Calculation of the determining resistors, first setting

Figure 3.43: Analog Devices Program: Calculation of the determining resistors - setting with E12 standard resistors.

This page is part of a Frameset: Electrodynamic Sculpture: A Thesis by Rafael Bräg.