The overvoltage protection mechanism of a ceramic ozone tube power supply is a core design element ensuring safe operation under abnormal voltage conditions. Its core objective is to limit the voltage within a safe range through a multi-level protection strategy, preventing safety accidents caused by overvoltage breakdown of the ceramic ozone tube or damage to the power module. This mechanism typically combines components such as a ceramic gas discharge tube (GDT), a varistor, and a transient voltage suppressor diode (TVS) to form a comprehensive solution of "graded protection + energy dissipation + current limiting."
The ceramic gas discharge tube (GDT) is the first line of defense against overvoltage. Filled with inert gas, it exhibits high impedance under normal operating voltage, having no impact on the circuit. When the voltage exceeds a threshold, the gas ionizes, forming a low-impedance path that diverts the surge current to ground, while simultaneously limiting the voltage to a low residual voltage level of 20-50V. For example, in the event of a lightning strike or grid fluctuation causing a sudden voltage surge, the GDT can respond quickly, preventing high voltage from directly impacting the ceramic ozone tube or power module. However, it's important to note that GDTs have a follow current issue—if their holding voltage drops below the supply voltage after the overvoltage disappears, they may continue to conduct, potentially damaging the equipment. Therefore, they must be used in conjunction with other devices.
Variants with rotating surfaces (MOVs) are crucial for secondary protection. Their nonlinear volt-ampere characteristics cause their resistance to drop sharply during overvoltage, clamping the voltage to a safe value. Compared to GDTs, MOVs have a faster response time (nanoseconds), but a smaller current capacity, so they are often used in series or parallel with GDTs. For example, after the GDT turns on, the MOV can absorb residual energy, preventing voltage bounce; simultaneously, its clamping effect limits the GDT's follow current, preventing the equipment from being in a short-circuit state for an extended period. Furthermore, the leakage current of MOVs must be strictly controlled; otherwise, it may accelerate aging and affect their lifespan.
Transient voltage suppressor diodes (TVS) are used for fine-tuning protection. Their extremely fast response time (picoseconds) and low clamping voltage make them ideal for protecting ceramic ozone tube control circuits. TVS (Transient Voltage Suppressor) devices are typically placed at the power input or in sensitive signal lines. When the voltage exceeds their breakdown voltage, the TVS quickly conducts, limiting the voltage to a safe range and preventing high voltage damage to downstream chips or sensors. For example, in the DC-DC conversion circuit of a power module, a TVS can suppress voltage spikes generated by the switching transistor, protecting the stability of the ceramic ozone tube drive circuit.
Multi-level protection design is a core strategy for improving safety. A typical solution uses a combination of a ground-level transformer (GDT) + varistor + TVS: the GDT is responsible for discharging amplified surges, the varistor absorbs medium-level overvoltages, and the TVS protects sensitive circuits. This structure expands the protection range and compensates for the shortcomings of a single device through synergistic effects. For example, in an industrial ozone generator, a GDT and a varistor may be configured simultaneously at the power input, while the control circuit uses a TVS for fine protection, ensuring stable operation of the equipment in complex electromagnetic environments.
Freewheeling current control is a critical aspect in preventing equipment damage. To address the freewheeling current issue of the GDT, a varistor or a self-resetting fuse (PPTC) can be connected in series in the circuit. When the GDT (Gas Transducer) is turned on, if the voltage still exceeds its sustaining voltage, the series-connected devices limit the current to a safe range, preventing overheating or fire. For example, in a ceramic ozone tube power supply, the GDT and varistor are connected in series and then in parallel across the power supply. When the GDT freewheels, the clamping effect of the varistor limits the current to the milliampere level, ensuring equipment safety.
In practical applications, overvoltage protection mechanisms need to be optimized based on the characteristics of the ceramic ozone tube. For example, high-frequency, high-voltage power supplies may generate voltage spikes due to switching transistor operation; in this case, a TVS (Transient Voltage Suppressor) or RC (Residual Voltage Suppressor) absorption circuit needs to be added to the power module output. High-power ozone generators require a combination of high-current-capacity GDTs and varistors to cope with extreme situations such as lightning strikes. Furthermore, regularly testing the performance of protection devices (such as the GDT's breakdown voltage and the varistor's leakage current) is also an important measure to ensure long-term safety.
The overvoltage protection mechanism of the ceramic ozone tube power supply constructs a comprehensive protection system from source to end through multi-level protection, energy dissipation, and current limiting strategies. This mechanism not only needs to consider the selection and matching of components, but also needs to be optimized in combination with actual application scenarios to ensure that ceramic ozone tubes operate stably in complex electromagnetic environments, providing a solid guarantee for the safety and reliability of ozone generating equipment.
