Abstract: The present device includes a resistor network wherein the values of the resistors are chosen such that the heat generated by current passing through the resistors will be substantially equal to heat generated at a semiconductor junction which is to be cooled. The present device further includes a heat sink which is substantially identical to the heat sink employed to withdraw heat from the semiconductor junction to be cooled. Accordingly, the present device provides heat which is identical to the heat generated at the semiconductor junction and which heat remains ambient to the semiconductor junction to be cooled. The present device further includes a sensor which converts temperature to an electrical signal and which is located substantially in the center of the resistor network and at a distance from the heat sink that approximates the position of the semiconductor junction from its heat sink.

Abstract: In a space shuttle, payloads are individually temperature controlled by means of a liquid control loop in heat exchange relationship with both the payload and a radiator or shuttle cold plate. The liquid pump is driven at a variable speed to control the heat transferred between the load and the radiator or cold plate, and the motor may be reversed to by-pass the radiator through check valves. The radiator includes heat pipes seated in elongated, high thermal conductivity extrusions and retained therein by elongated springs. The motor is a brushless DC motor isolated from the pump by a magnetic clutch and thermal isolator. The motor is driven by a digital circuit which provides a single pulse to each set of windings during each energizing time frame. The width of that pulse is modulated to provide for speed control. Pulse width modulation is by means of a one-shot, the pulse duration of which is controlled by a speed control signal.