Solid-State Switch Zero-Crossing Control for Inrush Suppression

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Solution Overview

Problem

Solid-state switches experience large impact currents upon startup at high voltage, leading to incorrect short-circuit protection activation, especially in capacitive loads, due to their poor short-circuit endurance and fast response.

Innovation Solution

Implementing a control circuit that determines the direction of phase voltage and switches on semiconductor devices at zero-crossing points to gradually increase current flow from zero, suppressing impact currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the solid-state switch is configured with fast short-circuit protection response (less than 5 microseconds), then the short-circuit protection capability is improved, but the impact current generated upon startup causes wrong activation of short-circuit protection

Engineering Contradiction:

Improveshort-circuit protection capabilityVSAvoidimpact current causing wrong protection activation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The control circuit performs preliminary detection of the startup state before activating the solid-state switch. By detecting whether the switch is in a startup state and the phase voltage direction, the control circuit prepares the switching strategy in advance, ensuring that the switch is turned on at the appropriate zero-crossing point to avoid impact current

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control circuit continuously monitors the phase voltage and detects its direction and zero-crossing points. This feedback mechanism allows the control circuit to adjust the switching timing dynamically, turning on the solid-state switch at the correct moment when phase voltage crosses zero, thereby preventing impact current while maintaining fast short-circuit protection response

Inventive Principle:

Principle #23Feedback

2Productivity

If the solid-state switch is turned on at high voltage value upon startup, then the switch can immediately supply power to the load, but a large impact current is generated especially in capacitive load

Engineering Contradiction:

Improvepower supply speedVSAvoidlarge impact current

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The invention changes the timing parameter of the switching operation by detecting the phase voltage direction and waiting for the zero-crossing point before activating the solid-state switch. This parameter change ensures that switching occurs when voltage is zero, eliminating impact current while maintaining rapid power supply capability through optimized control

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12562728B2Solid-state switch device and operating method for the same

Publication Date: 2026.02.24 SCHNEIDER ELECTRIC IND SAS

AI summary

There is provided a solid-state switch device connected between a single-phase power supply source and a load, including: a phase bridge arm circuit, including a first and a second power semiconductor switches, which each includes a first, a second and a control ends and each includes a body diode, wherein the second ends of the first and the second power semiconductor switches are connected in series in phase of a single-phase power supply source; a phase voltage sampling circuit, configured to acquire sampled values of phase voltage of the phase bridge arm circuit; and a control circuit, configured to determine direction of the phase voltage according to the sampled values, turn on one of the power semiconductor switches whose body diode direction is the same as the direction of the phase voltage, and turn on the other within a half cycle after the immediate zero-crossing of the phase voltage.