Tech Ideas

With the increasing fashion to get the notebook in the car to enjoy the convenience and the joy during travel, more and more car owners like to use the car adapter to ensure the exchange of the different current for the items in the car. Since it is to protect the items, you have the necessity to learn about the theory of the working of the adapter. Here provides you just a brief introduction for the theory of the current.

PolyZenTM component devices are combination of integrated circuit components precision Zener diodes and polymer positive temperature coefficient (PPTC). Theses devices are used to prevent inductive voltage spikes, instantaneous high voltage power to adapter, the wrong circuit overvoltage, overcurrent protection causing damages. The RLOAD is protected by downstream circuit.

During normal operation, VIN input voltage is higher than the breakdown voltage of Zener diode VZ. The IFLT current through the Zener diode to ground, VOUT output voltage is stable. With the abnormal over-voltage input VIN, then the zener diode IFLT will produce over-current. When over-current is on the device, its resistance is to high resistance by the low resistance state and transient state, so that the pressure drops in its increase. This is the brief theory in the use of the car adapter.

VOUT output is essentially the same, but the current flows through the zener diode IFLT decreases. Device voltage drop increases not only to protect the Zener diode, but also to protect the downstream circuitry. In addition, if they are to protect the downstream short circuit in the presence of local or short-circuit fault, IOUT will increase. PPTC devices from the low resistance state into a high impedance state can get over current protection circuit.

The device’s main features are to protect downstream electronics from overvoltage and reverse components bias the damage (for example, whe it used the wrong car adapter 5V as 12V adapter or reverse polarity). Because of PPTC devices, it reduces the Qi Zener cooling requirements, reducing the total PCB area and cost. In overvoltage fault, VOUT output is essentially the same. And the tolerance Zener diode energy is up to 30W.

The device is mainly used in portable multimedia player (PMP), GPS, 5V and 12V bus, hard drive-based protection, and USB5V bus protection. The device has nine varieties, and its electrical characteristics as shown in the use. The circuit protection devices appear to be some of the simple structure of the components, and they are often not being seriously. Among the many books in the circuit, protection circuit is not described or only introduced some old products (such as fuses, zinc oxide varistor and TVS). Technical books in this area need to keep up with product development, such as the main sources of information manufacturer of circuit protection components, data and application notes.