Bootstrap Driver Supply Voltage for Strong Gate Drive
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Solution Overview
Problem
Existing power systems face challenges in providing a strong driving ability for power switches while maintaining low quiescent current and small die size, as increasing switching frequency or capacitance leads to increased quiescent current or die size, respectively.
Innovation Solution
The power system incorporates a switching circuit with a high side and low side transistor, a bootstrap capacitor, and a power generation circuit that generates a supply voltage based on the input voltage, boost output voltage, and bootstrap voltage, thereby enhancing the driving ability without increasing quiescent current or die size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the switching frequency of the charge pump is increased to improve driving ability, then the driving ability is improved, but the quiescent current increases
Solution Approach 1:
The charge pump circuit dynamically adjusts its switching frequency based on the actual driving requirements. The control circuit monitors the driving ability needs and modulates the switching frequency accordingly, allowing the system to achieve high driving ability only when necessary while maintaining low quiescent current during normal operation. This dynamic adaptation resolves the contradiction between power output and energy consumption.
2Power
If the capacitance of the flying capacitor is increased to improve driving ability, then the driving ability is improved, but the die size increases
Solution Approach 1:
Instead of using a large fixed capacitance flying capacitor, the system employs a smaller capacitor combined with dynamic switching control. The control circuit adjusts the switching frequency and duty cycle to compensate for the smaller capacitance, achieving the required driving ability without increasing the physical size of the capacitor. This resolves the contradiction between power capability and device area.
Solution Approach 2:
The system changes the operating parameters (switching frequency, duty cycle) of the charge pump circuit to optimize the performance of a smaller flying capacitor. By adjusting these parameters dynamically, the system achieves high driving ability from a compact capacitor design, avoiding the need for large die size while maintaining sufficient power output.
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 configuration effectively increases the driving ability of the power system while keeping the quiescent current low and the die size small, thereby addressing the limitations of existing power systems.
Implementation Method 1
a bootstrap capacitor coupled between the switching node and a bootstrap terminal, and configured to provide a bootstrap voltage at the bootstrap terminal
Implementation Method 2
the switching circuit is configured to work in a buck mode to convert the input voltage to the system voltage, or to work in a boost mode to convert the system voltage to a boost output voltage
Data Source
AI summary
A supply voltage generating circuit and method for a power system. The power system has a power input terminal to receive an input voltage, a system output terminal to provide a system voltage, a switching circuit, a bootstrap capacitor, and a first driver circuit with a power terminal. The switching circuit works in a buck mode to convert the input voltage to the system voltage, or in a boost mode to convert the system voltage to a boost output voltage. The bootstrap capacitor provides a bootstrap voltage at a bootstrap terminal. The method is generating an input pump voltage based on the input voltage and the boost output voltage, generating a first supply voltage based on the bootstrap voltage and the input pump voltage, and providing the first supply voltage to the power terminal of the first driver circuit.