Fractional Negative Charge Pump With Dynamic NFET Gate Bias Control
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Solution Overview
Problem
Conventional charge pumps struggle to provide a fractional negative voltage output that is within a safe range for modern FET-based circuitry, as the magnitude of the negative voltage from a conventional negative charge pump can exceed the device's limits, leading to reliability issues and gate-induced drain leakage.
Innovation Solution
A charge pump design that outputs a fractional negative voltage, such as VOUT=−½ VDD, by connecting fly capacitors in series during charging and in parallel during discharging, reducing the magnitude of the negative voltage and minimizing electronic noise, thereby providing a more balanced output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional negative charge pump is used to generate negative voltage, then the output voltage magnitude is sufficient for most applications, but the voltage magnitude exceeds the safe range for modern FET-based circuitry, causing reliability issues and gate-induced drain leakage
Solution Approach 1:
The charge pump circuit is divided into multiple identical charge pump units connected in parallel. Each unit generates a fraction of the total required current, with individual current control capability. This segmentation allows precise control of the negative voltage output magnitude to match FET gate bias requirements, preventing gate-induced drain leakage while maintaining circuit reliability.
Solution Approach 2:
The charge pump implements dynamic current control through adjustable duty cycle operation. The control circuit dynamically adjusts the switching duty cycle to regulate the average output current and voltage magnitude. This dynamic adjustment enables the output voltage to be precisely controlled within the safe range for modern FET-based circuitry, eliminating reliability issues caused by excessive voltage magnitude.
2Reliability
If the charge pump output voltage magnitude is reduced to a safe range, then FET gate bias safety is improved, but the voltage may be insufficient for applications requiring higher voltage levels
Solution Approach 1:
The charge pump system is segmented into multiple identical, independently controllable units. Each unit can be adjusted to provide a safe fractional negative voltage for FET gate bias. The parallel configuration and individual duty cycle control of each unit provide adaptability to match various voltage requirements, ensuring both safety for modern FET-based circuitry and versatility for different application voltage levels.
Solution Approach 2:
The charge pump employs adjustable duty cycle operation to dynamically change the output voltage parameter. By varying the duty cycle, the output voltage magnitude can be precisely controlled to match different application requirements while maintaining safety within the FET breakdown voltage limits, thus achieving both reliability and adaptability.
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 design effectively reduces the output impedance and voltage magnitude, ensuring a safe and efficient gate bias for NFETs, reducing power consumption and preventing gate-induced drain leakage, while maintaining a lower voltage sufficient for most applications.
Implementation Method 1
A converter circuit based on a charge pump uses capacitors (not shown in FIG. 1) to transfer charge from the input to the output of the power converter 100
Data Source
AI summary
Charge pump circuits having a fractional negative voltage output from a positive voltage input. A control circuit provides for feedback control of the output of such a charge pump, and may include dynamic adjustment of the charge pump output based on one or more factors. In some embodiments, two or more charge pumps are coupled in a differential configuration such that while one set of capacitors are in series charging, at least one other set of capacitors is discharging. One embodiment encompasses a fractional negative voltage charge pump including n≥2 capacitors configured to be coupled in series between an input voltage and ground during a charging phase, and in parallel between ground and an output terminal during a discharging phase. The fractional negative voltage charge pump outputs a negative voltage that is no more than 1/n of a positive voltage input in magnitude.