Cryocooler Driver Circuit Using Tracking Buck Converters

Solution Overview

Problem

Conventional cryocooler drive circuits suffer from poor power efficiency due to excess power being wasted as heat, as they require additional voltage headroom to properly bias H-bridge transistors, leading to inefficient energy delivery to the motor.

Innovation Solution

A cryocooler drive circuit utilizing a pair of switching power converters, specifically synchronous buck controllers, to generate sinusoidal output voltages that track input voltages, eliminating the need for H-bridge driver circuits and reducing heat loss by optimizing voltage delivery to the motor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If H-bridge driver circuits are used to drive AC motor, then the motor can be properly biased and driven, but excess power is wasted as heat due to voltage headroom requirements

Engineering Contradiction:

Improvemotor drive capabilityVSAvoidpower efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the voltage parameter relationship by using tracking power converters that dynamically adjust the output voltage to match the input voltage minus a small dropout, eliminating the fixed voltage headroom requirement of H-bridge circuits. This allows the motor to be driven with much smaller voltage margins, reducing power loss while maintaining drive capability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes the mechanical H-bridge switching architecture with an electrical tracking power converter system. Instead of using transistors to mechanically switch and create voltage differences, the system uses controlled power conversion to directly synthesize the required motor drive voltages, eliminating the inherent voltage headroom losses of the H-bridge topology.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If voltage headroom is provided for H-bridge transistors, then proper transistor biasing is achieved, but 40 watts of peak power is wasted

Engineering Contradiction:

Improvetransistor biasingVSAvoidwasted power

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent changes the voltage parameter relationship by using tracking power converters that dynamically adjust the output voltage to match the input voltage minus a small dropout, eliminating the fixed voltage headroom requirement of H-bridge circuits. This allows the motor to be driven with much smaller voltage margins, reducing power loss while maintaining drive capability.

Inventive Principle:

Principle #35Parameter changes

3Power

If conventional buck converter is used to convert 50V to 26V, then power supply conversion is achieved, but 5V headroom is lost creating excess heat

Engineering Contradiction:

Improvevoltage conversionVSAvoidvoltage headroom loss

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent employs feedback control in the tracking power converters to continuously monitor the input voltage and dynamically adjust the output voltage to maintain the minimum necessary voltage differential. This feedback mechanism ensures that only the essential voltage drop is taken, minimizing power loss while maintaining proper operation of the motor drive circuitry.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the voltage parameter relationship by using tracking power converters that dynamically adjust the output voltage to match the input voltage minus a small dropout, eliminating the fixed voltage headroom requirement of H-bridge circuits. This allows the motor to be driven with much smaller voltage margins, reducing power loss while maintaining drive capability.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution achieves high efficiency, with synchronous buck controllers operating in the 80-90% range, significantly reducing heat loss and improving power delivery to the cryocooler motor, compared to conventional systems.

Implementation Method 1

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

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS8970158B1High-efficiency-direct-drive cryocooler driver

Publication Date: 2015.03.03 TELEDYNE FLIR LLC

AI summary

In one embodiment, a cryocooler drive circuit for a cryocooler motor is provided that includes: 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 output node; and 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 output 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 between the first and second output nodes.