Bidirectional Solid-State Switch With Soft Switching and Snubber Control
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Solution Overview
Problem
Conventional solid-state relays suffer from transient current and voltage shocks due to parasitic inductance and capacitance, leading to unreliable operation in medium to high power scenarios, and existing solutions fail to provide independent control over current flow direction.
Innovation Solution
A bidirectional controllable solid-state relay with dual semiconductor switches and snubber circuits for zero-current turn-on and zero-voltage turn-off, allowing independent control of current flow direction and suppressing transient shocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional solid-state relays are used for switching, then switching speed and response time are improved, but transient current and voltage shocks occur due to parasitic inductance and capacitance, causing unreliable operation in medium to high power scenarios
Solution Approach 1:
The patent applies preliminary action by pre-charging capacitors before switching operations. The control circuit charges capacitors C1 and C2 to the supply voltage before turn-on, and maintains capacitor C3 charged during turn-off. This preliminary energy preparation eliminates transient shocks by ensuring proper voltage levels are established before switching occurs, thereby achieving both fast switching and reliable operation in medium to high power scenarios.
Solution Approach 2:
The patent uses capacitors C1, C2, and C3 as intermediary energy storage elements between the power source and the semiconductor switches. These capacitors act as buffers that absorb and release energy during switching transitions, preventing direct transient shocks from reaching the switches. This intermediary approach allows fast switching while maintaining reliable operation by isolating the switches from harmful transients.
2Power
If electromechanical relays are used for high DC voltage switching, then switching capability is achieved, but the cost grows very rapidly
Solution Approach 1:
The patent replaces the mechanical relay system with a solid-state switching circuit using semiconductor switches (Q1, Q2), capacitors, and a control circuit. This substitution eliminates moving parts, contact arcing, and mechanical wear while maintaining high voltage switching capability. The solid-state implementation achieves the same power switching function at a lower cost and with improved reliability, directly addressing the cost escalation problem of mechanical relays in high power applications.
3Ease of operation
If electromechanical relays are used, then switching function is provided, but abrupt on and off transitions create large transitional spikes that can weld contacts and cause sparking
Solution Approach 1:
The control circuit performs preliminary action by pre-charging capacitors C1 and C2 before turn-on switching. This ensures that when the semiconductor switches close, there are no inrush current spikes because the capacitors are already at the required voltage level. Similarly, C3 is pre-charged before turn-off to prevent voltage spikes. This eliminates contact welding and sparking hazards while maintaining smooth switching function.
Solution Approach 2:
The patent converts the potentially harmful parasitic capacitance into a beneficial element by using capacitors C1, C2, and C3 to actively manage switching transitions. Instead of allowing parasitic effects to create harmful spikes, the circuit uses controlled capacitance to shape the switching waveforms, ensuring smooth transitions that eliminate sparking and contact damage while maintaining effective switching function.
4Adaptability or versatility
If dual channel control signals are independently controlled, then higher degree of freedom for control and protection is achieved, but device complexity increases
Solution Approach 1:
The control circuit achieves multi-functionality by using a single integrated circuit that can independently control two channels (Q1 and Q2) with different timing and voltage requirements. The same control circuit handles both turn-on and turn-off sequences, charges multiple capacitors, and provides protection functions. This universal approach provides high control flexibility for bidirectional power flow while avoiding the complexity of separate control circuits for each function.
Data Source
AI summary
An apparatus for controlling an electrical current flow between a first device and a second device includes a first semiconductor switch having a first conduction terminal and a second semiconductor switch having a first conduction terminal coupled to the first conduction terminal of the first semiconductor switch. The apparatus also includes a first snubber circuit coupled to a second conduction terminal of the first semiconductor switch and a second snubber circuit coupled to a second conduction terminal of the second semiconductor switch, wherein the first snubber circuit is adapted to couple with the first device and the second snubber circuit is adapted to couple with the second device.