Anti-Series Switch Control Circuit for ISG Voltage Regulation
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Solution Overview
Problem
Integrated starter-generator (ISG) systems face challenges in efficiently regulating output voltage across a wide range of operating conditions, particularly in managing energy flow and preventing battery discharge during low rpm operations, while also requiring efficient energy management to support both motor and generator modes.
Innovation Solution
A control circuit with anti-series connected switches and half-bridge configurations, utilizing MOSFETs and diodes, which allows for efficient series regulation, reducing power dissipation, and providing reverse battery protection, enabling constant voltage charging and efficient energy use across varying rpm conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional voltage regulation methods are used in ISG systems, then voltage control is achieved, but power dissipation increases and component count increases
Solution Approach 1:
The patent combines the voltage regulation function with the existing half-bridge circuit by adding only one switch per phase in anti-series configuration. This merging approach allows the same circuit topology to perform both motor control and voltage regulation functions, reducing the need for separate regulation components and thereby reducing overall component count while maintaining low power dissipation through efficient switching operation.
Solution Approach 2:
The patent employs dynamic switching control where the additional switches are activated only when needed for voltage regulation (when generator output voltage exceeds battery voltage). The switching duty cycle is dynamically adjusted based on the operating conditions, allowing the circuit to adapt between motor mode and generator mode efficiently. This dynamic operation minimizes power dissipation by avoiding continuous conduction and enables effective voltage regulation without requiring complex static regulation components.
2Loss of energy
If series regulation is implemented to reduce power dissipation, then energy efficiency improves, but circuit complexity increases
Solution Approach 1:
The patent makes the half-bridge circuit universal by enabling it to perform multiple functions: motor control in motor mode and series voltage regulation in generator mode. The same switches and circuit topology are used for both purposes, with the only addition being one switch per phase connected in anti-series. This multi-functionality approach allows series regulation to be implemented without creating a separate complex regulation circuit, thereby reducing power dissipation while keeping the overall circuit configuration manageable.
3Manufacturing precision
If anti-series switch configuration is used for voltage regulation, then constant voltage charging is achieved across wide speed range, but switch control complexity increases
Solution Approach 1:
The patent implements feedback control where the microcontroller monitors the generator output voltage and battery voltage, and based on this feedback, dynamically adjusts the switching duty cycle of the anti-series switches. The control algorithm compares the regulated voltage with the desired battery charging voltage and modifies the switch conduction time accordingly. This feedback mechanism enables precise constant voltage charging across the wide speed range while managing the switch control complexity through intelligent algorithms that adapt to operating conditions.
Solution Approach 2:
The patent changes the switching parameters (duty cycle, frequency, and conduction angle) of the anti-series switches based on the operating conditions. By dynamically adjusting these parameters, the circuit achieves constant voltage regulation despite variations in generator speed and load conditions. The microcontroller modifies the switching parameters in real-time to maintain optimal voltage regulation, thereby achieving manufacturing precision in voltage control while managing control complexity through parameter optimization.
Data Source
AI summary
This disclosure describes a control circuit to manage the energy flow for an integrated motor generator (IMG), such as an integrated starter generator (ISG) system. The circuit regulates the output voltage of the IMG when the IMG operates in generator mode. The circuit includes an additional switch for each phase connected in anti-series with the half-bridge circuit for the phase, e.g., the drain of the additional switch connects to the drain of the high-side switch. When the ISG is in generator mode, the additional switches are controlled, e.g., to charge the battery at a constant voltage and current throughout the speed range of the ISG (i.e. high rpm and low rpm). In generator mode, the high-side switches may be turned off, which configures the high-side switches to act as a diode and block battery discharge for low rpm operation when the phase voltages are lower.