Power Path Management with Cold Start Capacitor Charging
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Solution Overview
Problem
Energy harvesting systems with low energy density sources face challenges in providing stable and efficient power, particularly during peak demands and cold start conditions, leading to slow startup and potential deep discharge of rechargeable batteries.
Innovation Solution
A power converter circuit design that includes a cold start circuit to charge a capacitor using energy from the harvest source, enabling a regulated voltage level for the main converter circuit to operate efficiently, and a charging control circuit to manage energy from multiple sources, including a backup battery, to prevent deep discharge and ensure uninterrupted operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If energy harvesting systems use low energy density sources, then the system can achieve autonomy and energy independence, but the system experiences slow startup time and cannot meet peak energy demands
Solution Approach 1:
The system performs preliminary action by charging the capacitor during periods when energy is available (normal operating conditions). The capacitor is pre-charged to a high voltage level so that during cold start or peak demand situations, the stored energy can be immediately deployed without waiting for the low-power energy harvest source to accumulate sufficient energy, thus resolving the slow startup issue while maintaining autonomy
Solution Approach 2:
A capacitor is introduced as an intermediary energy storage device between the low energy density harvest source and the load. The capacitor acts as a buffer that can rapidly deliver high power during startup and peak demands, while the energy harvest source continuously charges it during normal operation. This intermediary resolves the contradiction by decoupling the slow energy accumulation from the fast power delivery requirements
2Device complexity
If the energy harvest source directly powers the system during cold start, then the system can maintain simplicity, but the startup process becomes excessively slow and may fail to reach operational voltage
Solution Approach 1:
The circuit performs preliminary action by using the energy harvest source to charge the capacitor to a predetermined high voltage level before the main system needs to operate. This pre-charging ensures that when cold start is required, sufficient energy is already stored in the capacitor to reliably bootstrap the system to operational voltage, preventing startup failure
Solution Approach 2:
The capacitor serves as an intermediary that bridges the gap between the limited energy harvest source and the higher voltage requirements of the system during cold start. By mediating the energy transfer and voltage transformation, the capacitor enables reliable startup without requiring complex voltage multiplication circuits or external power sources, thus maintaining circuit simplicity while improving reliability
3Power
If the rechargeable battery is used to provide power during peak demands, then the system can meet high energy requirements, but the battery may experience deep discharge which reduces its lifespan
Solution Approach 1:
The system implements feedback control through the charging control circuit that continuously monitors the battery charge level and the energy availability from the harvest source. When the battery charge level drops below a threshold or when the harvest source provides sufficient energy, the control circuit switches to charging the battery from the harvest source instead of discharging it further. This feedback mechanism prevents deep discharge and extends battery lifespan while still enabling peak power delivery when needed
Solution Approach 2:
The system changes the operational parameters of the battery by controlling its charge/discharge cycles through the charging control circuit. The circuit adjusts the battery's state of charge to remain within safe operating boundaries, preventing deep discharge conditions. By dynamically changing the battery's charge level parameter based on energy availability and system needs, the system achieves peak power delivery without compromising battery lifespan
4Reliability
If multiple energy sources and circuit paths are implemented, then the system can improve power management and prevent deep discharge, but the device complexity increases
Solution Approach 1:
The charging control circuit is designed with multi-functionality to manage multiple energy sources (energy harvest source and rechargeable battery) and multiple energy storage elements (capacitor and battery). This single control circuit performs several functions: monitoring energy levels, determining optimal power paths, controlling charge/discharge operations, and protecting against deep discharge. By consolidating these functions into one universal controller, the system achieves robust power management without proportionally increasing circuit complexity
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 significantly reduces cold start time and ensures efficient power delivery by utilizing energy from the capacitor and managing multiple energy sources, enhancing the reliability and efficiency of energy harvesting systems.
Implementation Method 1
a cold start circuit configured to produce a first voltage level at the output port by charging a capacitor at the output port using energy of the energy harvest source
Implementation Method 2
a main converter circuit configured to produce a second regulated voltage level at the input/output port using energy of the energy harvest source
Data Source
AI summary
An apparatus comprises an output port for a circuit load, a first input port for an energy harvest source, an input/output port a second energy source, a first circuit path from the energy harvest source to the second energy source at the input/output port and to the variable load at the output port, a second circuit path from the second energy source to the output port, a cold start circuit that produces a first voltage level at the output port by charging a capacitor at the output port using energy of the energy harvest source, and a main converter circuit that produces a second regulated voltage level at the input/output port using energy of the energy harvest source when the voltage at the output port capacitor is above a specified voltage value and uses the energy of the capacitor at the output port during startup of the main converter circuit.