DC-DC Converter Gate Charge Reuse Driver
Solution Overview
Problem
Switch mode DC-DC converters experience increased switching losses at higher frequencies due to metal-oxide-semiconductor field effect transistors (MOSFETs), which reduces system efficiency and shortens battery life in low-voltage battery-powered equipment.
Innovation Solution
Implementing gate charge re-use and charge sharing techniques in the driver circuit, combined with the use of laterally diffused MOS (LDMOS) transistors and a tank capacitor, to regulate voltage swings and reduce power consumption across the gates of switching transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If switching frequency is increased to reduce output filter size, then converter compactness is improved, but switching losses increase and system efficiency deteriorates
Solution Approach 1:
The patent extracts the gate charge from the driver circuit and stores it in a dedicated capacitor during the high-side MOSFET on-time. This separated storage approach allows the gate charge to be reused rather than continuously supplied by the driver, thereby reducing switching losses while enabling higher switching frequencies that can shrink the output filter size.
Solution Approach 2:
The patent recovers the gate charge that would otherwise be wasted during the low-side MOSFET on-time by storing it in a capacitor during the high-side MOSFET on-time. This recovered charge is then reused to drive the low-side MOSFET gate, converting what would be energy loss into a useful resource that reduces overall switching losses and improves efficiency.
2Power
If switching frequency is increased to improve power density, then converter efficiency is improved, but battery life deteriorates due to increased switching losses
Solution Approach 1:
The patent converts the harmful effect of gate charge discharge (which normally occurs during dead-time and causes power loss) into a beneficial resource. By capturing the gate charge during the high-side MOSFET on-time and storing it in a capacitor, the system transforms what would be wasted energy into reusable charge for the low-side MOSFET gate drive, thereby reducing switching losses and extending battery life while maintaining high power density.
Solution Approach 2:
The system becomes self-sufficient in generating its own gate drive charges. The gate charge capacitor serves itself by being charged during one MOSFET's on-time and then autonomously providing the charge for the other MOSFET's gate drive, reducing the continuous power demand from the external power supply and improving overall system efficiency and battery life.
3Loss of energy
If gate charge re-use is implemented to reduce switching losses, then system efficiency is improved, but driver circuit complexity increases
Solution Approach 1:
The patent segments the gate drive function into two distinct parts: a driver circuit that generates control signals and a separate gate charge capacitor that stores and supplies the actual gate charge. This segmentation allows the driver to operate at lower power while the capacitor handles the high-current gate drive requirements, reducing overall switching losses while keeping the driver circuit relatively simple.
Solution Approach 2:
The gate charge capacitor acts as an intermediary between the driver circuit and the MOSFET gates. Instead of the driver directly driving the MOSFET gates (which would require continuous high current), the capacitor serves as a buffer that stores charge and delivers it to the gates, simplifying the driver's requirements while reducing switching losses through controlled charge transfer.
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 significantly reduces switching losses, allowing for higher frequency operation while extending battery life by minimizing power consumption and maintaining efficiency.
Implementation Method 1
a tank capacitor, to regulate voltage swings and reduce power consumption across the gates of switching transistors
Data Source
AI summary
A DC-DC converter includes an output power stage and a driver circuit. The output stage switches an input voltage to a switch node using a first transistor in response to a top-gate signal received at a top-gate node, and the switch node to ground using a second transistor in response to a bottom-gate signal received at a bottom-gate node. The driver circuit that provides the top- and bottom-gate signals in response to high- and low-side switch signals, respectively, activates the top-gate signal by actively regulating the top-gate node to a first voltage between a threshold voltage and a breakdown voltage of the first transistor using charge from the bottom-gate node, and activates the bottom-gate signal by actively regulating a second voltage provided to the bottom-gate node between a threshold voltage and a breakdown voltage of the second transistor using charge from the top-gate node.