Circuit protection is necessary to ensure that a circuit will work reliably for 10 years and beyond. Input power supplies are susceptible to spikes from various sources including lightning, high-power machinery (e.g., generators and motors), or interference from outside sources (e.g., microwaves). The figure below shows one way to provide circuit protection. If a voltage spike is applied at VIN, the metal oxide varistor (MOV) will act at 18 V and the positive temperature coefficient (PTC) fuse will limit the current drawn. A transorb (transient voltage suppressor), which can be thought of as an ultrafast silicon zener diode, can be used in place of the MOV. Also, a capacitor in parallel with the MOV will soak up fast transient spikes—an electrolytic capacitor for low-frequency transient voltages and a small-value ceramic capacitor for high frequency transient voltages.
Circuit Cellar's editorial team comprises professional engineers, technical editors, and digital media specialists. You can reach the Editorial Department at [email protected], @circuitcellar, and facebook.com/circuitcellar
Leave a Comment