Isolated Drive Circuit Using AC Bus for Motor Gate Drivers
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Solution Overview
Problem
Conventional motor drive systems require a significant number of DC-AC-DC signal conversions and discrete components for isolation, leading to complex configurations and high IC counts, while also needing isolation of gate driver supply signals from the source and each other to prevent single point failures.
Innovation Solution
The system converts a supply rail to AC in a first isolation stage, using transformers and coupled inductors to isolate motor phase control supply signals, eliminating the need for DC-AC-DC conversions and integrating primary and secondary supply channels with automatic output selection and monitoring to reduce the risk of single point failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional DC-AC-DC isolation conversions are used for each motor phase, then isolation reliability is improved, but device complexity and IC count increase significantly
Solution Approach 1:
The patent merges multiple isolation functions into a single AC bus that serves all motor phases simultaneously. Instead of performing separate DC-AC-DC conversions for each phase, the system converts DC to AC once and distributes it across all phases through isolated gate driver modules, dramatically reducing IC count while maintaining isolation reliability
Solution Approach 2:
The AC bus serves as a universal isolated power source for all motor phases and gate driver modules. A single AC-to-DC conversion stage provides power to multiple isolated outputs, making the isolation system multi-functional and eliminating the need for redundant conversion circuits in each phase
2Reliability
If multiple discrete components are used for DC-AC-DC conversion in each isolation stage, then isolation function is achieved, but manufacturing cost and assembly complexity increase
Solution Approach 1:
Multiple discrete conversion stages are merged into a single AC bus generation stage followed by distributed AC-to-DC conversion at gate driver modules. This consolidation reduces the total number of discrete components required and simplifies the manufacturing process while maintaining isolation functionality
3Device complexity
If gate driver supplies are not isolated from source and each other, then circuit complexity is reduced, but single point failure risk increases
Solution Approach 1:
The gate driver power supply is segmented into isolated channels for each motor phase through separate AC-to-DC conversion circuits. Each phase receives power through its own isolated path from the common AC bus, preventing single point failures from affecting the entire system while keeping the overall circuit design manageable
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 the number of ICs required, simplifies circuit design, and ensures reliable isolation of gate driver supplies, lowering voltage requirements and board space needs while maintaining a common AC supply voltage throughout the system, with only DC conversion occurring at the point of use.
Implementation Method 1
a first transformer has a primary winding having one end coupled to the first DC input signal and another end coupled to the first switch, and a second transformer has a primary winding having one end coupled to the second DC input signal and another end coupled to the second switch; controlling, by the supply control module, the first and second control signals so that a secondary winding of the first or second transformer energizes an isolated AC bus
Implementation Method 2
receiving a first isolated AC signal at a first gate driver module for a motor phase, wherein the first isolated AC signal is generated by first and second coupled inductors, wherein the first coupled inductor is connected to the isolated AC bus; and receiving a second isolated AC signal at a second gate driver module for the motor phase, wherein the second isolated AC signal is generated by third and fourth coupled inductors, wherein the third coupled inductor is connected to the isolated AC bus
Data Source
AI summary
Methods and apparatus for providing DC motor gate driver isolation. In embodiments, first and second DC input signals are received at a supply control module, which generates first and second control signals for controlling first and second switches. A first transformer has a primary winding having one end coupled to the first DC input signal and another end coupled to the first switch A second transformer has a primary winding having one end coupled to the second DC input signal and another end coupled to the second switch. The supply control module controls the first and second control signals so that a secondary winding of the first or second transformer energizes an isolated AC bus coupled to the first and second transformers. First and second gate drivers receive respective isolated AC signals from the isolated AC bus. Conversion of the isolated AC signals back to DC occurs at the point of use.