Dual Charge Pump Energy Harvesting for Low-Voltage Start-Up
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Solution Overview
Problem
Existing energy harvesting systems struggle with high start-up voltage requirements and inefficiencies in converting low AC voltage signals into usable DC power, particularly in integrated circuits using 180 nm CMOS technology.
Innovation Solution
The system incorporates a switch to selectively hold down the input voltage of a comparator when the AC-DC charge pump output exceeds a threshold, utilizes PMOS transistors to connect the DC-DC charge pump output to the comparator nodes, and employs control circuitry with dual oscillators to manage the DC-DC charge pump, enabling lower voltage start-up and reducing capacitor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional energy harvesting circuits are used, then they can convert AC voltage to DC voltage, but they require high start-up voltage and cannot operate from low voltage sources
Solution Approach 1:
The energy harvesting system is divided into two distinct charge pump stages: an AC-DC charge pump that converts AC voltage to DC voltage, and a DC-DC charge pump that boosts the DC voltage to higher levels. This segmentation allows each stage to be optimized for its specific function, enabling the system to start up from very low AC voltages while still achieving sufficient output voltage for practical applications.
Solution Approach 2:
The AC-DC charge pump performs preliminary voltage conversion by converting low-voltage AC signals to DC voltage before the main DC-DC charge pump operates. This preliminary action enables the system to accumulate sufficient voltage headroom to启动 the higher-voltage DC-DC charge pump, which then provides the necessary voltage boosting for the load.
2Loss of energy
If larger capacitors are used in the charge pump, then voltage conversion efficiency improves, but device area increases
Solution Approach 1:
The total capacitance requirement is segmented between two charge pump stages. The AC-DC charge pump uses smaller capacitors optimized for low-voltage operation, while the DC-DC charge pump uses capacitors optimized for higher voltage operation. This segmentation allows the system to achieve efficient voltage conversion without requiring one large capacitor that would consume excessive area.
Solution Approach 2:
The system changes operating parameters between stages: the AC-DC charge pump operates at low voltages with capacitance values optimized for that range, while the DC-DC charge pump operates at higher voltages with capacitance values optimized for boosting. This parameter change approach allows efficient operation across the full voltage range without requiring oversized capacitors.
3Productivity
If the charge pump operates continuously, then power conversion is maintained, but start-up time increases when voltage thresholds are not met
Solution Approach 1:
The system dynamically transitions between operational modes based on voltage thresholds. The AC-DC charge pump operates continuously to accumulate voltage, and when sufficient voltage is reached, the DC-DC charge pump is activated. This dynamic operation allows the system to minimize start-up time while maintaining continuous power conversion capability once operational.
Solution Approach 2:
The charge pumps operate in periodic cycles: the AC-DC charge pump charges capacitors during initial start-up, and when voltage thresholds are met, the DC-DC charge pump is periodically activated to boost voltage. This periodic activation pattern allows the system to maintain productivity while minimizing the time spent in non-operational states.
Data Source
AI summary
Systems and methods are disclosed for energy harvesting circuits. For example, an apparatus (e.g., an integrated circuit) includes a first PMOS transistor with a source terminal connected to an output of an AC-DC charge pump and a drain terminal connected to a first node; a second PMOS transistor with a source terminal connected to the output of the AC-DC charge pump and a drain terminal connected to an output node; a first NMOS transistor with a gate terminal connected to the first node, a source terminal connected to a first input node, and a drain terminal connected to the first node; a second NMOS transistor with a gate terminal connected to the first node, a source terminal connected to a second input node, and a drain terminal connected to the output node; and a switch connected between the second input node and a ground node.