Charge Pump Actuator for MEMS Capacitive Loads
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Solution Overview
Problem
Existing MEMS devices face challenges in designing a low-cost, power-efficient charge pump mechanism for charge-reuse actuators, particularly in initializing voltages across capacitors efficiently, especially when the power source is of low voltage and parasitic resistances are present.
Innovation Solution
A low-cost power-efficient charge pump mechanism is implemented using a controller to manage the timing of charge transfer between capacitors, utilizing an inductor to complement the charge of one capacitor before starting a new cycle, ensuring efficient voltage control by determining the programmable time duration for inductor current buildup and discharging the remaining charge to ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge pump mechanism is used to initialize high voltage on capacitors, then voltage initialization is achieved, but power consumption increases and device complexity increases
Solution Approach 1:
The system uses the capacitive load itself to generate the high voltage needed for initialization through charge pumping during normal operation. The load's own operation creates the conditions for voltage initialization without requiring an external high-voltage charge pump, making the system self-sufficient and reducing power consumption.
Solution Approach 2:
The charge pump operates periodically during specific phases of the capacitive load operation cycle. By timing the charge transfer to coincide with natural discharge phases of the load, the system achieves voltage initialization only when needed, minimizing unnecessary power consumption while maintaining reliable voltage levels.
2Productivity
If parasitic resistance is present in the circuit, then charge transfer occurs, but voltage maintenance becomes difficult and power efficiency decreases
Solution Approach 1:
The system proactively replenishes charge to the capacitive load before the voltage drops to problematic levels. By monitoring and preemptively adding charge during optimal moments in the operation cycle, the system compensates for parasitic resistance losses without allowing efficiency to degrade significantly.
Solution Approach 2:
The controller monitors the voltage levels and charge state of the capacitive load, using this feedback to determine when charge pumping is needed. This closed-loop control ensures charge is transferred efficiently only when necessary to maintain voltage, minimizing power dissipation while compensating for parasitic resistance effects.
3Use of energy by moving object
If charge reuse mechanism is implemented, then power consumption is reduced, but device complexity increases due to additional control circuitry
Solution Approach 1:
The controller serves multiple functions: it manages the capacitive load operation, monitors voltage levels, determines charge pumping needs, and controls the charge transfer timing. By making the controller multi-functional rather than adding separate dedicated circuits for each function, the system achieves charge reuse with minimal increase in overall device complexity.
Solution Approach 2:
The charge pump control logic is integrated with the existing capacitive load control architecture. By merging the charge management functions into the existing control structure rather than implementing them as separate systems, the design achieves power-efficient charge reuse while minimizing the complexity overhead of additional control circuitry.
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
This solution enables highly efficient charge-reuse capacitive load actuators in MEMS devices, reducing power consumption and maintaining high voltage levels across capacitors, even with low-voltage sources, by effectively managing inductor current and capacitor charging cycles.
Implementation Method 1
feeding the inductor with a supply current provided by a supply circuit, disconnecting the inductor from the supply circuit, coupling the inductor to the first capacitive load, and charging the first capacitive load by the inductor
Implementation Method 2
the voltage of the first capacitive load at the end of step 620 (when reaching a steady state) may exceed (and even well exceed) the maximal supply voltage
Implementation Method 3
first capacitor C112, first switch 13, input 14 from charge pump, second resistor R219, second capacitor C218, second switch 17
Data Source
AI summary
A method for charge-reuse, the method may include performing multiple repetitions of the steps of: operating a second capacitive load while the second capacitive load is disconnected from a first capacitive load; wherein the second capacitive load is a Microelectromechanical systems (MEMS) capacitive load or a Nanoelectromechanical systems (NEMS) capacitive load; electrically coupling a first capacitive load to a second capacitive load via a path that comprises an inductor; charging the first capacitive load with a second charge provided from the second capacitive load; electrically disconnecting the first capacitive load, the second capacitive load and the inductor from each other; feeding the inductor with a supply current provided by a supply circuit; disconnecting the inductor from the supply circuit and coupling the inductor to the first capacitive load; charging the first capacitive load by the inductor; electrically coupling the first capacitive load to the second capacitive load via the path that comprises the inductor; charging the second capacitive load with a first charge provided from the first capacitive load; and operating the second capacitive load while the second capacitive load is disconnected from the first capacitive load.