Method and integrated motor drive power electronics system with improved efficiency

1. An integrated motor drive power electronics system, comprising:

an active line filter configured to:

control and regulate time-invariant current drawn from a direct-current input power source, and

attenuate current ripple fed back to the input power source;

higher power motor drive electronics configured to operate directly from an output of the active line filter;

a bidirectional low voltage power supply configured to:

provide regulated power to a motor,

regulate voltage at the motor to a predetermined output voltage, and

selectively recycle power from the motor back to the input power source;

lower power motor driver electronics configured to operate from an output of the bidirectional low voltage power supply; and

an energy storage capacitance coupled to the output of the active line filter and configured to serve as a local input power source for the higher power motor drive electronics and the bidirectional low voltage power supply,

wherein the bidirectional low voltage power supply comprises:

a first discrete power converter configured to provide regulated power to the motor; and

a second discrete power converter configured to selectively recycle power from an output of the first discrete power converter back to the input power source and regulate the voltage at the motor to the predetermined output voltage, and

wherein the energy storage capacitance is recharged by a difference between current supplied by the active line filter and load current drawn by the higher power motor drive electronics plus load current drawn by the bidirectional low voltage power supply.

2. The integrated motor drive power electronics system of claim 1 , wherein:

the bidirectional low voltage power supply includes a first power stage to provide power conversion and first control electronics including a first error amplifier for controlling the first power stage to regulate a voltage at the output of the first discrete power converter to a first predetermined output voltage,

the second discrete power converter is coupled in parallel and in an opposite orientation with the first discrete power converter and includes a second power stage and second control electronics, the second power stage configured to provide power conversion to recycle the output power back to the input power source, and

the second control electronics include a second error amplifier for controlling the second power stage and configured to regulate the voltage at the output of the bidirectional low voltage power supply to a second predetermined output voltage.

3. The integrated motor drive power electronics system of claim 2 , wherein the first error amplifier is configured to:

reduce an output voltage of the first error amplifier when a voltage at the output of the first discrete power converter exceeds the first predetermined output voltage, and

further reduce the output voltage of the first error amplifier and set a duty cycle of the first discrete power converter to zero to disable the first discrete power converter when the output voltage remains higher than the first predetermined output voltage.

4. The integrated motor drive power electronic s system of claim 3 , wherein when the second error amplifier detects that the voltage at the output of the bidirectional low voltage power supply exceeds the second predetermined output voltage, the second error amplifier is configured to increase an output voltage of the second error amplifier to enable the second discrete power converter to recycle power back to the input power source.

5. The integrated motor drive power electronics system of claim 1 , wherein the second discrete power converter is configured to recycle power from the output of the first discrete power converter to the input of the first discrete power converter until a voltage at the output of the first discrete power converter drops below a predetermined output voltage.

6. A method for providing power in an integrated motor drive power electronics system, the method comprising:

controlling time-invariant current drawn from a direct-current input power source with an active line filter;

attenuating current ripple fed back to the input power source;

operating higher power motor drive electronics directly from an output of the active line filter;

providing regulated power to a motor with a bidirectional low voltage power supply;

selectively recycling power from the motor back to the input power source;

regulating a voltage at the motor to a predetermined output voltage;

operating lower power motor driver electronics from an output of the bidirectional low voltage power supply; and

providing a local input power source for the higher power motor drive electronics and the bidirectional low voltage power supply.

7. The method of claim 6 further comprising:

detecting when a voltage at the output of the bidirectional low voltage power supply exceeds the predetermined output voltage;

recycling power back to the input power source; and

regulating the voltage at the output of the bidirectional low voltage power supply.

8. An integrated motor drive power electronics system, comprising:

expander and balancer drive electronics configured to drive an expander motor and a balancer motor;

an active line filter arranged to:

attenuate ripple current fed back to a direct-current input power source, and

attenuate input voltage transients;

compressor motor drive electronics arranged to:

drive one or more compressor motors, and

draw power from and return power to an output of the active line filter; and

a bidirectional low voltage power supply arranged to:

provide power to the expander and balancer drive electronics,

recycle power from at least one of the expander motor and the balancer motor back to the output of the active line filter,

reduce electro-magnetic interference from the output of the active line filter, and

reduce input ripple current on the input power source.

9. The integrated motor drive power electronics system of claim 8 wherein the compressor motor drive electronics are arranged to drive one or more compressor motors of a cryocooler.

10. The integrated motor drive power electronics system of claim 9 , further comprising an energy storage capacitance coupled to the output of the active line filter and configured to serve as a local input power source for the compressor motor drive electronics and the bidirectional low voltage power supply.

11. The integrated motor drive power electronics system of claim 10 wherein:

compressor motor drive currents and voltage transients reflected back to the input power source are reduced, and

power sourced from a cryocooler motor is recycled back to the energy storage capacitance to increase efficiency.