Inverter Capacitor Pre-Charge Using Predictive Duty Cycle Control
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Solution Overview
Problem
Existing pre-charge solutions for battery-powered systems, such as those used in electric vehicles, suffer from high costs, complexity, and inefficiencies due to the requirement of specialized components like bulky resistors and high-voltage isolated power supplies, making it difficult to protect electrical circuits from large current pulses or voltages.
Innovation Solution
A software-based predictive active pre-charge system that uses low-frequency voltage measurements in a slow control loop to determine buck converter power switch duty cycles over defined intervals, eliminating the need for SMPS control hardware and isolated power supplies, and leveraging existing measurement circuitry to gradually charge electrical circuit elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive pre-charge systems are used with specialized components, then circuit protection is achieved, but system cost and component complexity increase
Solution Approach 1:
The patent extracts the pre-charge control function from dedicated hardware components and relocates it to software execution on existing processor units. The pre-charge controller executes pre-charge control code to generate switching signals, eliminating the need for specialized pre-charge control hardware while maintaining circuit protection functionality.
Solution Approach 2:
The patent makes existing measurement circuitry serve multiple functions by using it for both normal operation monitoring and pre-charge phase control. The same voltage and current measurement systems are utilized during pre-charge without requiring separate measurement circuits, reducing overall system complexity.
Solution Approach 3:
The control system uses its own existing processor units and measurement circuitry to perform pre-charge control, eliminating the need for external specialized components. The system serves its own pre-charge control needs through software execution on existing hardware rather than requiring separate dedicated hardware.
2Productivity
If active pre-charge systems with SMPS control hardware are used, then pre-charge performance is improved, but system cost and circuit complexity increase
Solution Approach 1:
The patent replaces the mechanical/electrical SMPS control hardware system with a software-based control system executing on existing processor units. The pre-charge control code performs the control function that would traditionally require dedicated SMPS control hardware, substituting software logic for hardware circuitry.
Solution Approach 2:
The patent extracts the control function from dedicated SMPS control hardware and relocates it to software execution. The processor units execute pre-charge control code to generate switching signals, removing the need for separate SMPS control hardware while maintaining effective pre-charge performance.
3Reliability
If high-voltage isolated power supplies are used for SMPS control, then control reliability is improved, but system cost increases
Solution Approach 1:
The patent extracts the high-voltage isolated power supply requirement by using low-voltage processor units that execute pre-charge control code. The same low-voltage power supply that powers the processor units also powers the measurement circuitry, eliminating the need for separate high-voltage isolated power supplies while maintaining control reliability through software-based control.
Solution Approach 2:
The patent makes the low-voltage power supply serve multiple functions by using it to power both the processor units and the measurement circuitry during pre-charge operation. This universal power supply approach eliminates the need for separate high-voltage isolated power supplies while maintaining system reliability.
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 system costs and complexity while effectively protecting electrical circuits by gradually charging to prevent damage, using low-frequency measurements and a software-controlled mechanism to manage duty cycles, thus enhancing efficiency and reliability.
Implementation Method 1
a switched bypass pre-charging path having one or more power switches for selectively connecting and disconnecting the battery and the inverter capacitor in response to one or more first switching control signals having a configurable duty cycle
Implementation Method 2
uses low-frequency measurements of a battery voltage and an inverter capacitor voltage to periodically determine a buck converter power switch duty cycle that is applied over a plurality of defined charging intervals
Data Source
AI summary
A device and method for actively pre-charging an inverter capacitor includes a switched bypass pre-charging path having one or more power switches for selectively connecting and disconnecting the battery and the inverter capacitor in response to one or more first switching control signals having a configurable duty cycle, where one or more processor units are configured with a predictive active pre-charging module to control active pre-charging of the inverter capacitor from the battery by using low-frequency measurements of a battery voltage and an inverter capacitor voltage to periodically determine the configurable duty cycle for the one or more first switching control signals that is applied over a plurality of specified charging intervals to actively pre-charge the inverter capacitor to the battery voltage.