US 5,752,385 AGranted

Electronic controller for linear cryogenic coolers

AssigneeLitton Systems, Inc.

InventorArthur Randall Nelson

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Abstract

A highly efficient motor driver circuit of an electronic controller for linear cryogenic coolers operates directly from a variable power supply, such as a battery, without the need for the voltage regulator control circuit of the prior art. Elimination of the prior art voltage regulator ensures a higher efficiency motor driver circuit of the electronic controller. Both open-loop and closed-loop controllers electronically control the motor driver circuit. The open-loop controller protects against temperature sensor failure, and will limit maximum motor power as a function of system ambient temperature. The closed-loop controller regulates the temperature of the cold finger accurately to a preset value, using feedback from a temperature sensor along with a novel pulse-width modulation concept for modifying motor drive waveforms. The motor driver circuit provides the advantages of increased efficiency, operation from a variable power source, tight control of temperature regulation, a fail-safe mode of temperature sensor feedback, and a small envelope space enabling electronic controller mounting internal to the cooler motor/compressor assembly of a linear cryogenic cooler.

Claims22

Dependent claims

A cryogenic cooler control system, comprising:

an electronic controller supplied with a variable voltage source;
a motor assembly containing a motor and a compressor, wherein the motor assembly is coupled to the electronic controller;
an insulated assembly containing a cold finger which is insulated by the insulated assembly, an infrared detector, and a temperature sensor, wherein the cold finger of the insulated assembly is coupled to the motor assembly and the temperature sensor is coupled to the electronic controller;
said electronic controller being further comprised of:
(a) an electromagnetic interference (EMI) filter supplied with the variable voltage source which filters noise from the variable voltage source and produces an output signal;
(b) a motor driver which converts the output signal of the EMI filter to a phased drive output signal which drives the motor of the motor assembly;
(c) a closed-loop controller supplied with a temperature sensor signal which produces an output signal which couples the closed-loop controller to the motor driver and controls the phased drive output signal of the motor driver;
and
(d) an open-loop controller which produces an output signal which couples the open-loop controller to the motor driver and controls the phased drive output signal of the motor driver to limit the power to the motor at a normal ambient temperature and increases the power to a preset power limit to the motor at an elevated temperature;
wherein the cold finger generates the refrigeration required to cool the infrared detector to a desired operating temperature and the electronic controller regulates the temperature of the infrared detector to a preset value.

7 more elements

A circuit for controlling the pulse-width of the motor drive applied to an electrical motor for use in a cryogenic cooler having a compressor for compressing a refrigerant used to cool a cold finger of the cryogenic cooler, the control circuit comprising:

an electromagnetic interference (EMI) filter supplied with a variable voltage source which filters noise from the variable voltage source and produces an output signal;
a motor driver which converts the output signal of the EMI filter to a phased drive output signal which drives a motor of a motor assembly;
a closed-loop controller supplied with a sensor signal which produces an output signal which couples the closed-loop controller to the motor driver and controls the phased drive output signal of the motor driver;
and
an open-loop controller which produces an output signal which couples the open-loop controller to the motor driver and controls the phased drive output signal of the motor driver to limit the power to the motor at a normal ambient temperature and increases the power to a preset power limit to the motor at an elevated temperature.

2 more elements

Dependencies are inferred from the claim text.