PMIC Cold-Start Circuit for Energy Harvesting
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Solution Overview
Problem
Existing power management integrated circuits (PMICs) for energy harvesting face inefficiencies in the cold-start voltage converter mode, as they do not operate at the optimum voltage for energy extraction, and may fail to start due to insufficient power availability, especially with varying energy harvester topologies and technologies.
Innovation Solution
A PMIC with a second input terminal for a voltage comparator that enables the cold-start circuit when a specific reference voltage is reached, allowing for optimal starting based on the input voltage, and transitions to the main voltage converter when the minimum operational voltage is achieved, using a voltage reducer to adjust the input voltage for efficient power extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cold-start circuit is used to start energy harvesting when output voltage is below minimum operational voltage, then energy harvesting can be initiated in degraded mode, but power extraction efficiency is reduced because the circuit does not operate at optimum voltage
Solution Approach 1:
The patent implements a dynamic switching mechanism between cold-start circuit and main voltage converter circuit based on real-time output voltage monitoring. When output voltage exceeds the minimum operational threshold, the system automatically transitions from cold-start mode to main converter mode, optimizing power extraction efficiency while ensuring reliable startup capability.
Solution Approach 2:
The voltage converter is segmented into two distinct circuits: a cold-start circuit for initial operation when voltage is below threshold, and a main voltage converter circuit for efficient operation when voltage exceeds threshold. This segmentation allows each circuit to be optimized for its specific operating range, resolving the contradiction between startup reliability and efficiency.
2Loss of energy
If the main voltage converter circuit is used for power extraction, then high efficiency is achieved, but the circuit cannot operate when output voltage is below minimum operational voltage
Solution Approach 1:
The cold-start circuit performs preliminary action by enabling initial energy harvesting and voltage buildup when the output voltage is below the minimum operational threshold. This preliminary operation prepares the system for subsequent high-efficiency operation of the main voltage converter circuit, ensuring both startup reliability and overall efficiency.
3Loss of energy
If a fixed nominal start-up voltage is used for the main voltage converter, then optimal power extraction is achieved for specific harvester types, but the system cannot adapt to varying energy harvester topologies and technologies
Solution Approach 1:
The patent enables dynamic adjustment of the nominal start-up voltage parameter based on the specific energy harvester type and topology being used. By allowing this critical parameter to be modified, the system maintains optimal power extraction efficiency across diverse harvester technologies including photovoltaic cells, thermoelectric generators, and electromagnetic energy sources with various configurations.
Solution Approach 2:
The voltage converter system is designed with multi-functionality to handle various energy harvester types and topologies. Through programmable control and adjustable parameters, the same hardware platform can adapt to different energy sources and extraction requirements, achieving universal compatibility while maintaining efficiency.
Data Source
AI summary
A power management integrated circuit (PMIC) is provided for extracting power from an energy harvester. The PMIC includes a voltage converter to convert an input power at a voltage Vin into an output power at an output voltage Vout_VC. The voltage converter includes, in addition to a main voltage converter circuit, a cold-start circuit for starting the voltage converter from an OFF state. The PMIC further includes an input terminal for receiving a voltage VEN-CS proportional to the converter input voltage Vin and a voltage comparator for comparing the voltage VEN-CS with a reference voltage Vref. A controller enables the cold-start circuit when VEN-CS≥Vref.