High-efficiency-direct-drive cryocooler driver

1. A cryocooler drive circuit for a cryocooler motor, comprising:

a first switching power converter configured to track a first sinusoidal input voltage signal to provide a first sinusoidal output voltage signal at a first node;

a second switching power converter configured to track a second sinusoidal input voltage signal to provide a second sinusoidal output voltage signal at a second node, wherein the second sinusoidal input voltage signal is an inverted version of the first sinusoidal input voltage signal such that the cryocooler motor is driven by an alternating current flowing through the first and second nodes; and

a first integrating operational amplifier for generating a first tracking signal responsive to the first sinusoidal input voltage signal and also responsive to the first sinusoidal output voltage signal, wherein the first switching power converter tracks responsive to the first tracking signal.

2. The cryocooler drive circuit of claim 1 , further comprising a power supply rail providing a power supply voltage signal, wherein each of the switching power converters is configured to convert the power supply voltage signal into the first and second sinusoidal output voltage signals.

3. The cryocooler drive circuit of claim 1 , wherein each of the first and second switching power converters is comprises a synchronous buck controller.

4. The cryocooler drive circuit of claim 1 , further comprising a feedback controller configured to adjust an amplitude of the first and second sinusoidal input voltage signals in response to a cryogenic temperature generated in response to the alternating current driven into the cryocooler motor.

5. The cryocooler drive circuit of claim 4 , wherein the feedback controller is a microcontroller.

6. The cryocooler drive circuit of claim 1 , further comprising a first inverting operational amplifier for generating the first sinusoidal input voltage signal in response to a microcontroller sinusoidal amplitude command signal, wherein a microcontroller adjusts the amplitude of the first sinusoidal input voltage signal using the microcontroller sinusoidal amplitude command signal.

7. The cryocooler drive circuit of claim 6 , further comprising a midscale voltage detection circuit configured to detect a midscale voltage in the microcontroller sinusoidal amplitude command signal, wherein the first inverting operational amplifier is also responsive to the midscale voltage in generating the first sinusoidal input voltage signal.

8. The cryocooler drive circuit of claim 6 , further comprising a second inverting operational amplifier for generating the second sinusoidal input voltage signal in response to the first sinusoidal input voltage signal.

9. The cryocooler drive circuit of claim 8 , wherein the second inverting operational amplifier is also responsive to a midscale voltage in generating the second sinusoidal input voltage signal.

10. The cryocooler drive circuit of claim 1 , further comprising the cryocooler motor.

11. The cryocooler drive circuit of claim 1 , further comprising a second integrating operational amplifier for generating a second tracking signal responsive to the second sinusoidal input voltage signal and also responsive to the second sinusoidal output voltage signal, wherein the second switching power converter tracks responsive to the second tracking signal.

12. A method of driving a cryocooler motor, comprising:

generating a first sinusoidal input voltage signal and a second sinusoidal input voltage signal that is out-of-phase with regard to the first sinusoidal input voltage signal;

in a first buck controller, converting a power supply voltage signal into a first sinusoidal output voltage signal that tracks the first sinusoidal input voltage signal, wherein the first sinusoidal output voltage signal is coupled to a first port for the cryocooler motor so as to drive an alternating current through the cryocooler motor; and

in a second buck controller, converting the power supply voltage signal into a second sinusoidal output voltage signal that tracks the second sinusoidal input voltage signal so as to drive the alternating current with regard to second port;

wherein the generating the first sinusoidal input voltage signal comprises generating a first tracking signal responsive to the first sinusoidal input voltage signal and also responsive to the first sinusoidal output voltage signal, wherein the first buck controller tracks responsive to the first tracking signal.

13. The method of claim 12 , wherein the generation of the first and second sinusoidal input voltage signals occurs responsive to sensing a cryogenic temperature in a cryocooler driven by the cryocooler motor.

14. The method of claim 13 , wherein the generation of the first and second sinusoidal input voltage signals further occurs responsive to a midscale voltage such that positive and negative cycles of the first and second sinusoidal input voltage signals are centered about the midscale voltage.

15. The method of claim 14 , wherein the second sinusoidal input voltage signal is 180 degrees out-of-phase with the first sinusoidal input voltage signal.

16. A cryocooler, comprising:

a cryocooler motor; and

a cryocooler drive circuit for driving an alternating current through the cryocooler motor, wherein:

the cryocooler drive circuit comprises a pair of buck controllers for generating the alternating current and a corresponding pair of operational amplifiers;

the corresponding pair of operational amplifiers are configured to generate first and second tracking signals responsive to first and second sinusoidal input voltage signals for respective ones of the pair of buck controllers and also responsive to first and second sinusoidal output voltage signals configured to provide the alternating current; and

the pair of buck controllers are configured to track responsive to the corresponding tracking signals.

17. The cryocooler of claim 16 , wherein each of the buck controllers is a synchronous buck controller.

18. The cryocooler of claim 16 , further comprising a feedback controller configured to adjust an amplitude of a sinusoidal amplitude command signal to adjust an amplitude of the alternating current generated by the pair of buck controllers.

19. The cryocooler of claim 18 , further comprising a temperature detector for detecting a cryogenic temperature produced by the cryocooler, wherein the feedback controller adjusts the amplitude responsive to the detected cryogenic temperature.

20. The cryocooler of claim 19 , wherein the feedback controller is a microcontroller.