Time-Sharing Bootstrap Drive Circuit for Switch Capacitor Converters
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Solution Overview
Problem
Traditional switch capacitor converters require multiple external bootstrap capacitors and additional pins for higher-power applications, making miniaturization difficult and limiting their use in small devices like mobile phones.
Innovation Solution
A drive circuit for switch capacitor converters that employs a time-sharing bootstrap power supply circuit with a single bootstrap capacitor, allowing power switches to be driven with the same voltage, reducing the number of components and simplifying the circuit by using a time-sharing control method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple external bootstrap capacitors are used to drive power switches in higher-power switch capacitor converters, then the driving capability and power handling are improved, but the device size and pin count increase, making miniaturization difficult
Solution Approach 1:
The patent merges multiple bootstrap capacitor functions into a single shared bootstrap capacitor. The drive circuit uses one bootstrap capacitor to generate bootstrap voltages for multiple power switches (Q1, Q2, Q3, Q4) through a unified power supply path, eliminating the need for separate external bootstrap capacitors for each switch. This consolidation reduces the overall device area while maintaining the power handling capability needed for higher-power applications.
Solution Approach 2:
The single bootstrap capacitor serves multiple functions by providing bootstrap voltage to multiple different power switches at different potential levels. The drive circuit dynamically connects the bootstrap capacitor to different switches as needed, making this single component universal for driving all power switches in the converter, thereby reducing component count and device size.
2Power
If multiple external bootstrap capacitors and additional pins are used for higher-power applications, then the driving capability is improved, but the circuit complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple independent bootstrap power supply circuits into a single unified bootstrap power supply circuit. Instead of having separate bootstrap capacitors and associated control circuitry for each power switch, the invention uses one bootstrap capacitor shared among all switches, controlled by a centralized drive circuit. This merging significantly reduces circuit complexity and the number of external pins required.
Solution Approach 2:
The drive circuit segments the bootstrap voltage distribution in time and control space. The single bootstrap capacitor is sequentially connected to different power switches through controlled switching, with each switch receiving bootstrap voltage during its specific operating phase. This time-based segmentation allows one capacitor to serve multiple switches without requiring simultaneous multiple capacitors, simplifying the overall circuit architecture.
Data Source
AI summary
A drive circuit for a switch capacitor converter having first, second, third, and fourth power switches connected in series, can include: first, second, third, and fourth drivers configured to respectively drive the first, second, third power, and fourth power switches according to control signals; a bootstrap power supply circuit comprising a bootstrap capacitor configured to supply power to the first, second, and third drivers in a time-sharing manner; and a power supply configured to supply power to the fourth driver and charge the bootstrap capacitor, where the fourth power switch is grounded.