Hysteresis Switch Stabilizes Charging Voltage in Energy Harvesting Modules
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Solution Overview
Problem
Conventional battery charging modules for rechargeable batteries in energy harvesting environments often fail to provide stable charging due to fluctuations in external power sources, leading to inefficient charging and reduced battery life.
Innovation Solution
A hysteresis switch with a simple circuit configuration, utilizing voltage dividing resistor pairs and switching devices like FETs or BJTs, is integrated into an electricity charging module, which includes a storage capacitor and a rectifying unit to stabilize the charging voltage and prevent overcharging/over-discharging, ensuring stable power delivery to rechargeable batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If external power is applied directly to the charging unit without storage capacitors, then the circuit configuration is simple, but the charging current is insufficient and charging stability is poor
Solution Approach 1:
The storage capacitor is charged in advance from the external power source before the charging unit operates. This preliminary energy storage ensures that when the charging unit activates, sufficient current is available, solving the insufficient charging current problem while maintaining circuit simplicity.
Solution Approach 2:
The storage capacitor acts as an intermediary between the external power source and the charging unit. It buffers power fluctuations and provides stable current to the charging unit, resolving the contradiction between simple circuit design and charging stability.
2Ease of operation
If the supply voltage fluctuates around the turn-on voltage level due to noises or environmental conditions, then the switch responds to voltage changes, but the switch turns on and off frequently resulting in unstable charging voltage
Solution Approach 1:
The hysteresis switch incorporates feedback through its inherent hysteresis characteristics, where the turn-on voltage threshold is higher than the turn-off voltage threshold. This feedback mechanism prevents frequent switching by requiring a significant voltage change to toggle the switch state, thereby stabilizing the charging voltage despite supply fluctuations.
Solution Approach 2:
The hysteresis characteristic acts as a cushion against voltage fluctuations. By designing the switch with a hysteresis window, the system anticipates and absorbs small voltage variations around the threshold, preventing unnecessary switching actions and maintaining stable charging voltage.
3Device complexity
If conventional switches are used without hysteresis characteristics, then the circuit is simple, but frequent switching occurs degrading charging efficiency and battery life
Solution Approach 1:
The patent changes the parameter of the switch by introducing hysteresis characteristics. This parameter change modifies the switching behavior from sensitive to fluctuating voltages to stable operation with defined turn-on and turn-off thresholds, thereby improving charging efficiency and extending battery life without significantly 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 hysteresis switch and charging module provide a stable charging voltage to rechargeable batteries, extending their life and reducing power consumption by minimizing leakage current, even in energy harvesting environments with fluctuating power sources.
Implementation Method 1
a first voltage dividing resistor pair (R1, R2) that divides the voltage of an external power source by the resistance ratio of the first voltage dividing resistor pair; a second voltage dividing resistor pair (R3, R4) whose one end is connected to a positive electrode terminal of the external power source
Implementation Method 2
a hysteresis switch capable of supplying a stable charging power to a rechargeable battery using a simple circuit configuration
Data Source
AI summary
An electricity charging module using a hysteresis switch includes a storage capacitor that preliminarily stores electrical energy supplied from an external power source, a charging unit for preventing over-charging or over-discharging through monitoring of the charging state of the rechargeable battery, and a hysteresis switch that has a larger turn-on voltage level than the turn-off voltage level, and located between the storage capacitor and the charging unit, thereby electrically connecting or disconnecting the storage capacitor with the charging unit. The hysteresis switch includes a first voltage dividing resistor pair that divides the voltage of an external power source by the resistance ratio of the first voltage dividing resistor pair, a second voltage dividing resistor pair whose one end is connected to a positive electrode terminal of the external power source, a first switching device whose control terminal is connected to the junction of the voltage dividing resistors of the second voltage dividing resistor pair, a second switching device whose control terminal is connected to the junction of the voltage dividing resistors of the first voltage dividing resistor pair, and a resistor that is connected to the junction between the first electrode terminal of the second switching device and the junction of the voltage dividing resistors of the first voltage dividing resistor pair.