Self-Regulating Current-to-Current Charge Pump
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Solution Overview
Problem
Conventional charge pumps face instability due to feedback regulation circuitry when converting input current to output current, particularly in applications like analog comparators, where maintaining a constant current ratio over process and temperature variations is crucial.
Innovation Solution
A self-regulating current to current charge pump design that includes two flying capacitors, a capacitor driver, rectifying inverters, a bypass capacitor, a current control transistor circuit, and an output circuit, which automatically adjusts to maintain a constant output current ratio without active feedback, using a capacitor driver to toggle the flying capacitors and rectifying inverters to develop an output current that follows the input current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback regulation circuitry is used to maintain current conversion ratio, then current ratio stability is improved, but system stability deteriorates due to feedback-induced oscillations
Solution Approach 1:
The patent removes the feedback regulation circuitry entirely from the charge pump system. Instead of using feedback to regulate current ratio, the invention relies on the inherent properties of the flying capacitor network and rectifying inverters to naturally maintain the desired current conversion ratio without causing stability issues.
Solution Approach 2:
The charge pump circuit self-regulates its current conversion ratio through the natural charging and discharging cycles of the flying capacitors and the rectifying action of the inverters. The circuit automatically maintains the correct current ratio without external feedback control, eliminating the stability problems associated with feedback loops.
2Measurement precision
If feedback regulation circuitry is implemented, then current conversion precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and removes the complex feedback regulation circuitry from the design. The current conversion precision is achieved instead through the carefully designed flying capacitor network and rectifying inverter configuration, which provide accurate current conversion without requiring additional regulation components.
3Power
If conventional voltage to voltage charge pump configuration is used, then voltage multiplication is achieved, but current to current conversion capability is lost
Solution Approach 1:
The patent designs a charge pump circuit that can perform both voltage multiplication and current to current conversion. The same flying capacitor network and rectifying inverters that provide voltage multiplication also enable accurate current conversion by tracking the input current through the capacitive energy transfer mechanism.
Solution Approach 2:
The patent replaces the traditional voltage-regulated mechanism with a current-tracking mechanism based on capacitive energy transfer. The flying capacitors transfer charge in proportion to the input current, and the rectifying inverters ensure unidirectional current flow, achieving current to current conversion while maintaining voltage multiplication capability.
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
The solution eliminates the need for active feedback circuitry, ensuring the output current remains constant over process and temperature variations, simplifying current sources and providing predictable tail currents for PMOS transistors in analog comparators, while operating with low supply voltage and minimizing voltage ripple.
Implementation Method 1
two flying capacitors, a capacitor driver... The capacitor driver drives a first terminal of each of the flying capacitors to opposite states between the control node and the input node using a clock signal
Implementation Method 2
two rectifying inverters... The rectifying inverters have inputs and outputs cross-coupled between the second terminals of the flying capacitors... develop an output current that follows the input current
Implementation Method 3
a bypass capacitor coupled between an input node and a control node
Data Source
AI summary
A current to current charge pump including two flying capacitors, a capacitor driver, two rectifying inverters, a bypass capacitor coupled between an input node and a control node, a current control transistor circuit coupled between the control node and a reference node, and an output circuit coupled between upper and lower nodes. One of the upper and lower nodes is held at a constant voltage level. A storage capacitor is coupled between the upper and lower nodes. The capacitor driver drives each of the flying capacitors to opposite states between the control and input nodes using a clock signal. The rectifying inverters are cross-coupled between the flying capacitors, and have supply terminals coupled between the upper and lower nodes. The current control transistor circuit develops an input current at the control node based on a reference current. The output transistor circuit develops an output current that follows the input current.