PPTC protection application in air freshener
The air freshener is a kind of negative ion generator, which is mostly used in hotels, hotels, offices of enterprises and institutions, interiors of trolleys, etc., and gradually enters modern homes. Air fresheners have gradually become the above venues. The necessary equipment, while people pay attention to its applicability, its safety, reliability and stability are also people's concerns. Air fresheners use high frequency, high voltage, and tip discharge to generate negative ions by ionizing air. The power tube is driven by the high-frequency high-voltage generator circuit, and the high-frequency high-voltage driving circuit is prone to current and temperature being too high to burn out the driving transistor. Higher requirements are placed on the design of the engineer.
To ensure the reliability and safety of the circuit, overcurrent and overtemperature protection circuits must be designed. Especially in the circuit detuning, short circuit, power tube overload, causing the board to burn out or scrap. It even causes accidents such as smoke and popping, which can cause electrical appliances to catch fire. The control board is similar to an electronic ballast, and its overvoltage protection, overcurrent protection, and overtemperature protection are similar. Solving the above protection problems is also diverse, but we recommend using SR PPTC (positive temperature coefficient thermistor, also known as self-recovery fuse or 10,000-times fuse) to optimize the overload protection of the air freshener control board. The solution, because the use of PPTC only needs a single component connected in series with the output circuit of the power tube, avoiding the matching and debugging problems of multiple components, low cost and high reliability of the component, and SRPPTC device can complete overcurrent protection at the same time. And over-temperature protection, and will maintain this state of protection until the power is turned off to return to the initial state. In the fault state of SR PPTC under short circuit, over current, over temperature, etc., under the dual action of high current and high temperature rise, PPTC device can change from low resistance state to high resistance state more quickly, and limit the current of power tube to protect in time. purpose. This protection state is maintained, and the SR PPTC device will return to the low resistance state from the high resistance state only after the power is turned off. The uninterrupted SR PPTC will not be recovered, which can effectively avoid the recovery of the power, the possible problems of the control board and potential problems and safety hazards.