Charge Pump With Level-Shift Circuit For Wide Control Voltage Range
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Solution Overview
Problem
Conventional charge pumps have a narrow operating range for the control voltage, which limits their suitability for various circuit applications, as the control voltage must be restricted between the supply voltage minus twice the overdrive voltage and the ground voltage plus twice the overdrive voltage, making them inadequate for broader operational needs.
Innovation Solution
The charge pump design includes a pull-up circuit and a pull-down circuit with level-shift circuits and switches that isolate the output node from the voltage nodes during operations, allowing the control voltage to vary widely without affecting the output voltage, effectively widening the operating range by decoupling the control voltage from the output voltage during charging and discharging processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control voltage is directly used to adjust transistor operation in conventional charge pumps, then the transistors operate in appropriate work modes, but the operating range of the control voltage becomes extremely narrow
Solution Approach 1:
The patent introduces a level-shift circuit as an intermediary between the control voltage input and the transistor gates. This level-shift circuit translates the wide-range control voltage into appropriate gate voltages for the transistors, allowing the control voltage to vary over a wide range while maintaining proper transistor operation. The level-shift circuit acts as a mediator that decouples the control voltage range from the transistor operating requirements.
2Adaptability or versatility
If the control voltage range is expanded beyond traditional limits, then the charge pump becomes more versatile for different applications, but the direct coupling between control voltage and output voltage causes operational instability
Solution Approach 1:
The patent segments the charge pump circuit into distinct functional blocks: a pull-up circuit with PMOS transistors, a pull-down circuit with NMOS transistors, and level-shift circuits for each. This segmentation allows independent optimization of each block and enables the control voltage to be decoupled from the output voltage through the level-shift interfaces, maintaining stability while expanding the operating range.
Solution Approach 2:
Level-shift circuits are introduced as intermediary stages between the control voltage input and the transistor gates in both pull-up and pull-down circuits. These level-shift circuits translate the wide-range control voltage into appropriate gate drive voltages, preventing direct coupling between control voltage variations and output voltage, thus maintaining output stability while allowing wide control voltage range.
3Adaptability or versatility
If switches are used to isolate nodes during charging and discharging, then the control voltage can vary independently from output voltage, but the circuit complexity increases
Solution Approach 1:
The patent combines the level-shift function with the switching function into integrated level-shift circuits that inherently provide node isolation during charging and discharging phases. By merging these functions, the patent reduces the number of separate components needed while achieving both control voltage independence and proper charge transfer timing.
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
A charge pump at least includes a current source, a first switch, a second switch, a level-shift circuit, and a capacitor. The first switch is coupled between the current source and an internal node. The capacitor is coupled between the internal node and the level-shift circuit. The second switch is coupled between the internal node and an output node. The first switch performs a closing-and-opening operation and the level-shift circuit performs a level-shift operation while the second switch is kept open and the internal node is isolated from the output node. The operating range of the charge pump is effectively widened by using the proposed design.