High Voltage Inverter Abnormal Voltage Detection Circuit
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Solution Overview
Problem
High voltage inverter devices generating alternating-current voltages exceeding 10 KV pose safety risks due to potential electric shock and ignition, and existing abnormality detection methods are ineffective for such high voltages, often leading to circuit malfunctions and insulation breakdowns.
Innovation Solution
A high voltage inverter device equipped with an abnormal voltage detection circuit and control circuit that uses a varistor and photocoupler to detect abnormal voltages on the excitation winding or between switching element terminals, allowing immediate detection and shutdown of the switching operation to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the output voltage is increased to exceed 10 KV to generate atmospheric pressure plasma, then the plasma generation capability is improved, but the safety risk increases due to potential electric shock and ignition
Solution Approach 1:
The patent introduces an intermediary protection circuit between the high voltage output and the load that includes a detection circuit and switching element. This intermediary mechanism detects abnormal conditions (overcurrent, overvoltage, insulation breakdown) and automatically disconnects the load, thereby enabling high voltage operation while mitigating safety risks through automated protection rather than direct human intervention or passive safety measures alone
2Measurement precision
If conventional abnormality detection methods are used with resistors divided in series for high voltage detection, then voltage detection becomes possible, but the number of resistors required increases to several tens or more and voltage leakage causes circuit malfunction
Solution Approach 1:
The patent uses a voltage division circuit with a limited number of high-voltage-rated resistors as an intermediary to step down the high voltage to a detectable level for the detection circuit. Instead of using dozens of resistors in series, the invention employs a small number of high-voltage resistors (typically 3-10) configured in series, each rated for the full input voltage, thereby achieving voltage detection with significantly reduced complexity while maintaining measurement capability
Solution Approach 2:
The patent changes the parameter of resistor voltage rating from low-voltage to high-voltage rated resistors. By using resistors that can withstand the full input voltage (e.g., 10 KV or higher), the invention reduces the number of resistors needed in series from several tens to just a few, thereby simplifying the detection circuit while maintaining the ability to detect abnormal voltages accurately
3Power
If the inverter operates at high voltage to provide sufficient power, then the power output is improved, but insulation breakdown of the transformer may occur causing electric shock or risk to human body
Solution Approach 1:
The patent implements a feedback protection circuit that continuously monitors the high voltage output and immediately feeds back abnormal condition signals to the control circuit. When insulation breakdown or abnormal voltage is detected, the control circuit automatically stops the inverter operation, creating a closed-loop feedback system that maintains high power output capability while preventing insulation failure through real-time monitoring and automatic shutdown
Solution Approach 2:
The patent incorporates preliminary protection measures including overcurrent protection, overvoltage protection, and insulation monitoring circuits that are activated before insulation breakdown can cause catastrophic failure. These preliminary detection mechanisms identify early signs of insulation stress and trigger protective shutdown, preventing the progression to complete insulation failure and eliminating electric shock risks
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 immediate detection and protection against abnormal voltages, preventing insulation breakdown and ensuring safety by stopping the inverter operation when abnormal conditions occur, even at high voltages above 10 KV.
Implementation Method 1
uses a varistor and photocoupler to detect abnormal voltages on the excitation winding or between switching element terminals
Implementation Method 2
uses a varistor and photocoupler to detect abnormal voltages
Implementation Method 3
switching the input voltage to apply an exciting current to an excitation winding on a primary side of a transformer and output a high voltage from an output winding on a secondary side
Data Source
AI summary
A high voltage inverter device uses, as an input voltage (Vin), a DC voltage or a voltage composed of a DC component with a pulsating current superposed thereon, switches the input voltage by a switching element (Qsw) to apply an exciting current to an excitation winding (NP) of a resonant transformer (10) and output an alternating-current high voltage (Vout) from an output winding (NS) of the resonant transformer. An abnormal voltage detection circuit (7) including a varistor (12) detects an abnormal voltage generated in the excitation winding (NP) of the resonant transformer (10), and when the abnormal voltage is detected, its signal is transmitted by a photocoupler (11) to a control circuit (20), thereby causing the control circuit (20) to stop its oscillation operation to stop a switching operation of the switching element (Qsw).