Buck-Boost Rectifier for Stable Refrigeration Power From Variable AC

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Solution Overview

Problem

Three-phase PWM rectifiers in vehicle refrigeration systems face challenges in managing varying AC power from alternators, leading to incomplete disconnection of power when AC voltage exceeds desired DC voltage, potentially damaging the system.

Innovation Solution

A buck/boost rectifier with a novel buck circuit that reduces DC voltage and includes a PWM controller and phase-angle controller to dynamically adjust voltage, allowing continuous power supply regardless of AC voltage magnitude by boosting or bucking the DC output as needed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If power is disconnected from the refrigeration system when AC voltage exceeds desired DC voltage, then system damage is prevented, but continuous operation cannot be maintained

Engineering Contradiction:

Improvesystem safetyVSAvoidcontinuous power supply

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

Instead of disconnecting power when AC voltage is too high, the patent inverts the approach by using a buck circuit to actively reduce the DC voltage to the desired level. This allows the system to remain connected and operational while maintaining safe voltage levels through active voltage reduction rather than passive disconnection.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent implements dynamic voltage control by switching between boost and buck circuits based on real-time AC voltage conditions. The controller dynamically adjusts the circuit configuration to maintain optimal DC voltage levels, enabling continuous operation across varying input conditions rather than static disconnection thresholds.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If only boost circuit is used in three-phase PWM rectifier, then DC voltage can exceed AC voltage, but system cannot handle cases where AC voltage is greater than desired DC voltage

Engineering Contradiction:

Improvevoltage regulation rangeVSAvoidsystem protection

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent makes the rectifier system universal by incorporating both boost and buck circuits, enabling it to handle both voltage boosting (when AC < DC) and voltage bucking (when AC > DC) scenarios. This multi-functional design allows the single system to adapt to all AC voltage conditions without requiring separate protection circuits.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent segments the voltage control function into two distinct circuits: a boost circuit for increasing voltage and a buck circuit for reducing voltage. Each circuit is optimized for its specific function, and the controller selects the appropriate circuit based on real-time voltage conditions, providing comprehensive voltage management capability.

Inventive Principle:

Principle #1Segmentation

3Adaptability or versatility

If AC voltage varies with alternator speed, then power generation adapts to engine speed, but DC voltage stability for refrigeration system cannot be maintained

Engineering Contradiction:

Improvepower generation adaptationVSAvoidDC voltage stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The patent implements feedback control by continuously monitoring the AC voltage from the alternator and using the controller to select appropriate circuit configurations (boost or buck) that maintain stable DC voltage output. The system responds to voltage variations by adjusting its operation in real-time, ensuring stable power delivery to the refrigeration system despite alternator speed changes.

Inventive Principle:

Principle #23Feedback

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

Enables continuous power supply to the refrigeration system without completely disconnecting power, ensuring system safety and efficiency across varying AC voltage conditions.

Implementation Method 1

rectifying the AC power into DC power, boosting the DC power when the AC power is not sufficient to produce DC power having a voltage that exceeds a threshold by rectifying alone

Methodology Applied

Scientific EffectRectification:

Implementation Method 2

bucking the DC power when the AC power has a magnitude which would produce a DC voltage that exceeds a second threshold when rectified alone

Methodology Applied

Scientific EffectRectification:

Data Source

PatentUS8605472B2Buck-boost rectifier, refrigeration system including a buck-boost rectifier, and method of providing power to a refrigeration unit via a buck-boost rectifier

Publication Date: 2013.12.10 THERMO KING CORP

AI summary

A buck/boost rectifier. The rectifier is connectable to an alternating current power source and includes an upper bus, a lower bus, an upper rectifier, a lower rectifier, a pulse-width-modulation (PWM) controller, a phase-angle (PA) controller, and a capacitor. The upper rectifier is coupled to the upper bus, and the lower rectifier is coupled in a series-type relationship with the upper rectifier and to the lower bus. The PWM controller is coupled to the lower rectifier and is configured to boost a direct current (DC) voltage output by the rectifier. The PA controller is coupled to the lower rectifier and is configured to buck the DC voltage output by the rectifier. The capacitor is coupled between the upper bus and the lower bus.