High-Efficiency Floating Gate Driver for FCML Converters
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Solution Overview
Problem
Conventional methods for driving high-side MOSFETs in flying capacitor multi-level (FCML) converters are inefficient and costly due to the need for large and complex DC/DC converters or multiple linear regulators, with existing techniques achieving only 36% efficiency.
Innovation Solution
A high-efficiency floating gate driver is developed, utilizing two capacitors and two switches, along with a voltage driver, level shifter, and FET driver, to provide a power supply for the gate of the high-side MOSFET, achieving 70% to over 80% efficiency by leveraging nodes within the power converter and minimizing component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional DC/DC converters or multiple linear regulators are used to drive high-side MOSFETs, then the MOSFETs can be properly controlled, but the efficiency is low (36%) and the device complexity is high
Solution Approach 1:
The driver circuit uses the floating node voltage of the high-side MOSFET source terminal to automatically charge the first capacitor during specific switching intervals. The circuit leverages the existing voltage differences in the power converter topology to charge capacitors without requiring external high-voltage power supplies, making the driver self-sufficient and eliminating the need for inefficient DC/DC converters or linear regulators
Solution Approach 2:
The circuit dynamically changes the charging voltage of the first capacitor by utilizing different voltage levels available at the floating node during different switching intervals. By capturing charge at appropriate voltage levels and transferring it to drive the MOSFET gate, the circuit achieves high efficiency without dissipative linear regulation
2Reliability
If conventional DC/DC converters or multiple linear regulators are used to drive high-side MOSFETs, then the MOSFETs can be properly controlled, but the device complexity and size are large
Solution Approach 1:
The driver circuit merges multiple functions into a single integrated structure: the first and second capacitors serve both as charge storage elements and as part of the voltage transformation mechanism; the switches serve both as power conversion elements and as gate drive control elements. This consolidation eliminates the need for separate DC/DC converter modules and multiple linear regulators, significantly reducing device complexity
Solution Approach 2:
The floating node in the power converter topology serves multiple purposes: it provides the charging voltage for the first capacitor, acts as a reference for the second capacitor, and enables the voltage transformation needed for high-side MOSFET gate drive. This multi-functionality eliminates the need for dedicated high-voltage power supply circuits, reducing overall system complexity
3Reliability
If conventional DC/DC converters or multiple linear regulators are used to drive high-side MOSFETs, then the MOSFETs can be properly controlled, but the cost is high
Solution Approach 1:
The circuit uses simple, low-cost components such as standard capacitors and switches instead of expensive DC/DC converter modules or multiple linear regulators. The capacitors are charged and discharged in specific intervals to provide the necessary gate drive voltage, replacing costly high-voltage power supply components with inexpensive energy storage elements
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
The solution significantly reduces the size and cost of the driver circuit while achieving higher efficiency, making it suitable for high-side MOSFETs in FCML converters.
Implementation Method 1
a first capacitor including a first terminal coupled to an output of the first driver; a first switch coupled to a second terminal of the first capacitor
Implementation Method 2
a second capacitor including a third terminal coupled to the first switch at a second node; and a second driver including a supply input coupled to the first switch and the third terminal second capacitor at the second node
Data Source
AI summary
Methods and apparatus to provide a high-efficiency drive for a floating gate are disclosed. An example apparatus includes a driver including a supply terminal, the driver configured to output a third voltage corresponding to the supply terminal, the driver to drive a gate of a transistor in a power converter; and a second capacitor to be charged using a first discharging current of a first capacitor and discharged at the supply terminal of the driver, the driver to drive the gate of the transistor based on a second discharging current from the second capacitor.