Solid-State Relay Boost Circuit for Normally Closed Operation
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Solution Overview
Problem
Semiconductor switches typically default to an open, non-conducting state when power is lost, making them unsuitable for applications requiring normally closed (NC) characteristics, such as electric door locks, where a power failure should not change the lock state.
Innovation Solution
A solid-state relay (SSR) is created by combining semiconductor switches with a boost converter, where the voltage drop across the switch is boosted to maintain the switch in a closed position even without a control signal, using components like enhancement mode FETs or BJTs, ensuring low resistance and energy efficiency for heavy load switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If semiconductor switches are used in traditional topology, then the device can switch AC or DC loads, but the switch defaults to an open non-conducting state when power is lost, which is unsuitable for applications requiring normally closed characteristics
Solution Approach 1:
The patent combines a semiconductor switch with a boost converter circuit to create a hybrid system that achieves normally closed characteristics. The boost converter uses the voltage drop across the conducting semiconductor switch to generate a control voltage that maintains the switch in its closed state, effectively merging two functional components to resolve the default state limitation.
Solution Approach 2:
The patent introduces a boost converter as an intermediary mechanism between the power source and the semiconductor switch. This intermediary circuit converts the small voltage drop across the switch into a sufficient control voltage, mediating the relationship between the switch's parasitic resistance and the required gate drive voltage to maintain the closed state.
2Reliability
If semiconductor switches with NC characteristics such as depletion mode FETs or JFETs are used, then the switch can maintain closed state without power, but these devices have high resistance in conducting state and are not suitable for high current switching
Solution Approach 1:
The patent changes the operating parameters of an enhancement mode FET by using a boost converter to provide sufficient gate-source voltage. This allows the FET to operate in its low-resistance linear region rather than relying on depletion mode devices, thereby reducing conduction losses while maintaining the ability to hold the closed state without continuous control power.
3Reliability
If a boost converter is added to create NC characteristics, then the switch can maintain closed state during power failures, but the device complexity increases
Solution Approach 1:
The boost converter circuit is designed to be self-sustaining by using the voltage drop across the conducting semiconductor switch as its input power source. Once the switch closes, the resulting voltage drop automatically powers the boost converter, which in turn maintains the switch closed without requiring external control power, making the system self-service and eliminating the need for separate control power supplies.
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 SSR maintains a closed state without additional control signals, ensuring secure and reliable door lock operation even during power failures, preventing unauthorized access by maintaining the lock state.
Implementation Method 1
a voltage output of the semiconductor switch (122) being electrically connected to a voltage input (108) of the boost converter (104), and a voltage output (110) of the boost converter (104) being electrically connected to the control input (124)
Data Source
AI summary
A solid-state relay includes a semiconductor switch and a voltage boost block. The semiconductor switch has a control input, which causes the semiconductor switch to shift from an open, non-conducting position to a closed, conducting position when a voltage is applied to the control input. The voltage boost block includes a boost converter and a ground connector. A voltage output of the semiconductor switch is electrically connected to a voltage input of the boost converter. A voltage output of the boost converter is electrically connected to the control input. The ground connector of the boost converter is electrically connected to a voltage input of the semiconductor switch When the semiconductor switch is in the closed position, the semiconductor switch is maintained in a closed position in the absence of another control signal.