Capacitor-Pulse Power Supply for Fast SMA Actuation Heating
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Solution Overview
Problem
Existing power supply circuits for shape memory alloy (SMA) and piezoelectric components result in slow actuation responses due to slow heating and significant heat loss, leading to low efficiency, and pose safety risks from direct high-voltage connections.
Innovation Solution
A power supply circuit that uses short high-voltage pulses by charging a tank capacitor and disconnecting the load during charging, then discharging the capacitor to supply the load, ensuring safe operation without direct high-voltage connection, utilizing an AC to DC converter, switching relay, and auxiliary resistor for safe discharge in case of load failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a DC low voltage supply is used to heat SMA component, then the structure is simple, but the actuation response is slow and heat loss is high
Solution Approach 1:
The patent applies periodic pulsed action by using a capacitor discharge mechanism that delivers high-voltage pulses to the SMA component. The capacitor is charged during a first time interval and discharged during a second time interval, creating periodic high-power pulses that rapidly heat the SMA component. This periodic action enables fast actuation response while maintaining simple structure.
2Speed
If high-voltage pulses are used to heat SMA component quickly, then actuation response is fast, but direct connection to high-voltage line may damage the component
Solution Approach 1:
The patent introduces a capacitor as an intermediary energy storage device between the power source and the SMA component. The capacitor is charged from the power line during a first time interval and then discharged to supply high-voltage pulses to the SMA component during a second time interval. This intermediary mechanism allows fast heating while isolating the component from direct high-voltage connection, ensuring component safety.
3Device complexity
If DC current is used to heat SMA component, then the supply circuit is simple, but heat loss to environment is high
Solution Approach 1:
The patent uses periodic pulsed operation where the capacitor is charged during a first time interval and discharged during a second time interval. This creates high-power pulses that rapidly heat the SMA component to the required temperature, significantly reducing the total energy required compared to continuous DC heating. The pulsed action minimizes heat loss to the environment while maintaining simple supply 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
Enables fast heating of SMA or piezoelectric components within 1-100 ms, improving actuation efficiency and ensuring safety by avoiding direct high-voltage connections, thus preventing overheating and component damage.
Implementation Method 1
Thermal activation of a component made of SMA, for example a wire made of SMA, may be driven by electrical current via Joule heating
Implementation Method 2
an AC to DC voltage converter (3, 5, 6, 8), connected between the AC input terminals and the DC output terminals, wherein the AC to DC voltage converter (3, 5, 6, 8), is configured to receive an AC mains voltage on the AC input terminals to generate a corresponding rectified DC voltage on the DC output terminals
Data Source
Figure 1
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Figure 2b
AI summary
A power supply circuit for supplying a load, which may be a SMA component or a piezoelectric component, may use short high-voltage pulses to achieve fast heating of the load and, in order to comply with functional requirements, the SMA or piezoelectric component should not be supplied by connecting it directly to an electric line at a relatively high voltage. It is also disclosed an actuator comprising a power supply circuit of this disclosure and at least one load, comprising at least one smart materials chosen between a piezoelectric device and a a shape memory alloy (SMA) component, and a method of supplying a load comprising the steps of: connecting the AC to DC voltage converter of the power supply circuit to the AC mains by closing the input switch for charging a tank capacitor of the converter and, at the same time, opening the output switch for disconnecting the load from the tank capacitor; disconnecting the AC to DC voltage converter of the power supply circuit from the AC mains by opening the input switch and, at the same time, closing the output switch to supply the load by discharging the tank capacitor.