Full-Wave Charge Pump Low-Voltage Startup
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Solution Overview
Problem
Existing charge pump technologies face challenges in achieving low-voltage startup, particularly for harvester outputs with low voltage and low power AC or DC signals, as they require overcoming diode threshold voltages without transformers or pre-charged supplies, limiting their ability to efficiently charge larger capacitors and maintain stable power supply in applications like wireless sensors and microprocessors.
Innovation Solution
A charge pump circuit with a Cockcroft-Walton arrangement, incorporating transistor pairs and a switching circuit with comparators and inverters, that uses passive sub-threshold switching and a mode selector to manage energy storage and switching based on threshold voltages, allowing efficient boosting and rectification of low-voltage inputs without external assistance, enabling startup from as low as 220 mV and stable charging of up to 100 μF capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional charge pump circuits are used, then voltage boosting can be achieved, but the minimum input voltage is limited by diode threshold voltage
Solution Approach 1:
The charge pump circuit is divided into multiple stages, each with its own transistor pair (NMOS and PMOS). This segmentation allows the circuit to progressively build voltage through each stage rather than requiring a single high-threshold component, enabling operation from lower input voltages while achieving the desired output voltage boost.
Solution Approach 2:
The patent introduces an intermediary mechanism using transistor pairs with complementary switching. The NMOS and PMOS transistors work together as intermediaries to transfer charge between stages, overcoming the limitation of single-diode threshold voltage and enabling voltage boosting from lower input levels.
2Extent of automation
If active MOSFET switches are used in charge pump, then switching control is improved, but a DC power supply is required to generate switching signals
Solution Approach 1:
The charge pump circuit generates its own switching signals internally through the operation of the transistor pairs and capacitive coupling. The circuit is self-sufficient and does not require an external DC power supply to generate switching signals, thereby maintaining automated switching control while reducing device complexity and external dependencies.
Solution Approach 2:
The transistor pairs serve multiple functions: they act as switches for voltage boosting, generate their own switching signals, and enable the circuit to operate from low input voltages. This multi-functionality eliminates the need for separate power supply circuits while maintaining controlled switching operation.
3Device complexity
If diodes are used for voltage boosting, then circuit simplicity is maintained, but significant voltage drop occurs due to threshold voltage
Solution Approach 1:
The patent changes the key parameter from diode threshold voltage to transistor threshold voltage by using MOSFET pairs. This parameter change allows for lower effective threshold voltage operation and reduced voltage drops during the boosting process, while maintaining relatively simple circuit architecture through the use of standard transistor components.
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 enables efficient low-voltage startup and high-efficiency boosting, achieving stable DC output voltages up to 1.5 V from inputs as low as 220 mV, with improved efficiency and reduced diode turn-on voltage, suitable for powering microprocessors and sensors with minimal power consumption, and maintaining stability even with non-periodic inputs.
Implementation Method 1
The charge pump circuit includes a first pair of capacitors coupled between a first node and a second node, and a second pair of capacitors coupled between a third node and a fourth node
Data Source
AI summary
A charge pump with low-voltage startup is presented. The charge pump circuit is comprised of transistor pairs arranged in stages, where the charge pump circuit is configured to receive an input voltage and generate an output voltage whose magnitude is larger than magnitude of the input voltage. An energy storage device is configured to receive and store voltage from the charge pump circuit. A switching circuit is interfaced with the control terminals of the transistors in the charge pump circuit. In response to leakage current through the transistors in the charge pump circuit, the switching circuit switches on select transistors in the charge pump circuit while voltage stored by the energy storage device is below threshold voltage of the transistors in the charge pump circuit.