DC-DC Converter Bypass for Electric Drive Efficiency

Solution Overview

Problem

Electric drive systems face inefficiencies due to sizing of DC-DC converters to peak power requirements, leading to undesirable electrical losses, particularly in inductor coils and semiconductor switches, despite often operating at lower torque/power levels.

Innovation Solution

Implementing a downsized DC-DC converter, such as a buck-boost or pure boost converter, and using a controller to selectively bypass the converter under high-power/high-torque conditions, adjusting bus voltage to match battery output voltage, and dissipating energy stored in the inductor coil to improve energy efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a DC-DC converter is sized to match peak power requirements, then peak power delivery capability is ensured, but electrical losses in the inductor coil and semiconductor switches increase

Engineering Contradiction:

Improvepeak power delivery capabilityVSAvoidelectrical losses in inductor coil and semiconductor switches

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent applies dynamics by making the DC-DC converter capacity adjustable rather than fixed. The controller dynamically selects between a first capacity (sized for peak power) and a second reduced capacity based on real-time power requirements. This allows the system to operate with a smaller converter during low-power conditions, reducing electrical losses in the inductor coil and semiconductor switches, while still maintaining peak power delivery capability when needed.

Inventive Principle:

Principle #15Dynamics

2Power

If a DC-DC converter is sized for peak power requirements, then peak power delivery is ensured, but system size and weight increase

Engineering Contradiction:

Improvepeak power delivery capabilityVSAvoidconverter size and weight

Core Design Contradiction:

PowerVSWeight of stationary object

Solution Approach 1:

The patent applies dynamics by making the DC-DC converter capacity adjustable rather than fixed. The controller dynamically selects between a first capacity (sized for peak power) and a second reduced capacity based on real-time power requirements. This allows the system to operate with a smaller converter during low-power conditions, reducing electrical losses in the inductor coil and semiconductor switches, while still maintaining peak power delivery capability when needed.

Inventive Principle:

Principle #15Dynamics

3Loss of energy

If a downsized DC-DC converter is used, then electrical losses are reduced, but peak power delivery capability is compromised

Engineering Contradiction:

Improveelectrical losses in converterVSAvoidpeak power delivery capability

Core Design Contradiction:

Loss of energyVSPower

Solution Approach 1:

The patent applies dynamics by making the DC-DC converter capacity adjustable rather than fixed. The controller dynamically selects between a first capacity (sized for peak power) and a second reduced capacity based on real-time power requirements. This allows the system to operate with a smaller converter during low-power conditions, reducing electrical losses in the inductor coil and semiconductor switches, while still maintaining peak power delivery capability when needed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies multi-functionality by enabling the DC-DC converter to perform multiple functions through capacity switching. The same converter infrastructure can operate in different capacity modes (first capacity for peak power, second capacity for reduced losses), allowing a single component to adapt to varying operational requirements rather than requiring separate converters for different power levels.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

This approach reduces electrical losses and system size, enhancing overall energy efficiency by operating the electric drive system with a smaller converter rated for less than 50% of peak power requirements, while maintaining responsive torque and power delivery.

Implementation Method 1

DC-DC converters include a relatively large and heavy inductor coil

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

switching control of the power inverter converts the polyphase voltage from the electric machine into a direct current voltage suitable for storage in the battery pack

Methodology Applied

Scientific EffectSemiconductor switching:

Data Source

PatentUS10110103B1Electric drive system enhancement using a DC-DC converter

Publication Date: 2018.10.23 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

An electric drive system includes bus rails carrying a bus voltage, an energy storage system (ESS), and a power inverter. The system includes a voltage converter connected to the bus rails and having an inductor coil, semiconductor switches, a bypass switch connected to a positive bus rail, and a capacitor. A polyphase electric machine is electrically connected to the power inverter. A controller executes a method in which operation of the converter is regulated based on power, torque, and speed values of the electric machine. The converter is selectively bypassed by closing the bypass switch under predetermined high-power/high-torque conditions, with the bus voltage adjusted until it is equal to the battery output voltage. The bypass switch is opened and the bus voltage thereafter regulated to a predetermined voltage.