Resettable fuse - parameters

Resettable fuse - parameters(Metal Oxide Varistor)

IH: Maximum operating current (25 ℃)

IT: Minimum operating current (25 ℃)

Itrip: overload current

Tmax: maximum overload current action time

Vmax: maximum overload voltage

Imax: maximum overload current

Rmin: minimum resistance (25 ℃)

Rmax: maximum resistance (25 ℃)

Resettable fuse - Application

Since the resumption of the the fuse series DIP DIP or SMD surface mount DC / AC power supply circuit. PPTC polarity of points. PPTC in the protection of the state, the surface temperature is high, to be installed in the ventilation status under high-temperature-sensitive components not in direct contact with the PPTC.

Applications:

ADSL equipment in the self-recovery fuse applications

Self-recovery fuse in the radio product, battery pack and charger products automotive electronics and auto parts overcurrent protection applications

Remote control electric toy car, high-low-frequency power charger electric toys, stroller and other electronic toys

Application of products in the satellite receiver DVB

Resettable fuse in the communication terminal equipment products

Power supply products

Home theater / speaker / crossover / electromagnetic load / motor / vacuum cleaner

Self-recovery fuse applications:

Ballast

Fluorescent lamps require a ballast to generate a high voltage and high current to point. The electrical characteristics of the ballast control fluorescent lamps. Produce high impact both ends of the electronic ballast of the lamp lights when the lamp lit, to form a self-oscillation circuit in the electronic ballast, the control of the oscillation circuit by the transistor. Many electronic ballast is due to lamp failure. Lamp shorted to achieve use deadline or lights are taken to open an overcurrent condition, and lead to the cathode of the lamp open. Due to the sake of the power factor, the load resistance becomes low. During starting, the ballast is in the non-normal operating current, high oscillation frequency state where more than three; switch circuit overcurrent and result in ballast failure.

Resettable fuse provide protection and fault protection transistor lights in the period of use is reached. Ballast failure often because the upper and lower terminal voltage of the transistor switch is open simultaneously, so the transistor fault protection is of great significance.

First, since the number of resettable fuse with automatic recovery performance, reduce rework and service, thereby reducing costs. Secondly, because resettable fuse can operate in extreme time, in order to protect some of the more sensitive resistor circuits, the ballast reliability and service life can be improved. Third, since the resettable fuse the power consumption is very low, does not appear the phenomenon of extreme heat and energy consumption in the the normal current working state. The resistance in the normal operating current is very small (usually only a few tenths of Ohms) and thus will not form an oscillation circuit. Fourth, self-resettable fuse small size, the space occupied by the circuit board, easy to design.

2 transformer(Metal Oxide Varistor)

With the failure of the power supply transformer is generated due to the over-current, resulting stream usually due to a short circuit or load decreases; cause failure circuit smoke, fire, and that damage to the circuit as well as interfaces. The low halide lamps light body structure transformer is often due to a short circuit fault. If improper installation and connection between the transformer and the lamp body, makes it easier to damage. Lamps are used in parallel, the short-circuit current. Installed resettable fuse to prevent short circuit and overload fault on the second coil of the transformer.

3 speakers

More stringent requirements on the protection of the speaker system. The ordinary fuse the speaker only from the disposable protective effect, so the increase in product failure rates; additional fuse box and wire manufacturer's costs increase. Also, the fuse must also meet the specifications, the error specifications fuse makes speaker damage. Install circuit breaker is a solution; However, they have not disconnected before off making noise. So, the best option is resettable fuse resettable fuse element. Self-resettable fuse in disconnected state (high-impedance state) is equivalent to a soft-switch will automatically revert to the failure to eliminate the state of the low resistance path.

4 Battery

a mobile phone battery pack: mobile phone battery pack key lies in its application characteristics, this battery is housed in a small and light and very narrow box inside. (NICD, NiMH, Li-ION) three major chemical batteries are installed in this universal inside the box. Now commonly used in a battery pack voltage is less than 10V, the maximum charging voltage of 16V, the latest varieties of the battery pack voltage is even lower, at between 3 ~ 4V. This means that the battery pack packaging changes very fast, from the development of the welding strip to the printed circuit board mount components. The battery packs are required circuit protection devices, such as VTP210G, able to 60C when the current maintained at about 1 amps. Protection circuit resistance is lower, the smaller the energy consumption, the greater the space of component selection.

b, cordless phone batteries: the cordless telephone via the current and voltage is relatively small. SRP120, LTP070 and LTP100 are good overcurrent protection devices.

c, radio communication battery: radio communication with current mobile phone battery current, than small laptop operating current. LR4 series of working current of 7.3 amperes, small size, light weight, and is very suitable for this application. With large current SRP or LTP series can also be applied.(Metal Oxide Varistor)

B) chemical batteries

Increasingly wide application of chemical batteries, the application of these components will cause the battery pack to have a better, lower-cost protection device.

A, NiCD battery: low impedance, stable chemical characteristics NiCD battery not like NiMH and Li-ION battery, as on so sensitive overcurrent. However, due to the low loss, the application is still very widely. However, in the short-circuited or overcurrent state, the low internal resistance will lead to a higher current through. The reasons for the failure of these batteries are usually over-current, instead of overheating, the products are suitable for application by any battery material.

B, NiMH battery: NiMH batteries have a higher energy density than NiCD battery. When more than 90C, these batteries are more easily degraded. Use the VTP or the LTP than SRP/LR4 material more suitable for the protection of this type of battery. According to the design method of the battery, SRP and LR4 can the battery protection, but using the LTP thermal performance when the VTP is stronger.

C, Li-ION battery: all chemical batteries, the energy density of Li-ION battery, the chemical properties of the most sensitive. , Need to be equipped with a circuit protection device in use and when charging. Now commonly used protective device is an integrated circuit, but this is not the most secure, because of the integrated circuit itself, may also cause a short circuit or a CMOS startup failure of the protective device unsafe. When more than 90C, Li-ION battery also began to degenerate, this battery voltage, circuit protection requirements even more stringent. LTP, SRP series as early as the battery, but the most appropriate PTC element VTP; the LR4 series of action shorter time for large capacity Li-ION battery, more than SRP series.

1, resettable fuse rechargeable battery pack

1), the problem with the analysis: NICD, NiMH, Li-ION special protection circuits commonly used in mobile phones and computers. Usually due to failure of these battery packs: the positive and negative terminals accidental short circuit; charger can not stop charging the battery fully charged; hold against the wrong charger or battery polarity. PTC SMD series installed in series in each cell of the battery pack to provide over-current and over-temperature protection circuit.

2), and protection requirements: when a failure occurs, the mobile phone of the voltage up to 16V, the voltage of the computer can achieve 24V; its current can be up to 100 amperes. In overcharge condition, the battery pack needs to be over-temperature protection, the the NiCD battery can not exceed 120C, NiMH and Li-ION battery can not exceed 90C.

3), the PTC element selection: LTP, VTP and LR4 commonly used in mobile phones and cordless phones, has higher holding current of the SRP, LTP and LR4 series commonly used in desktop and laptop computers. NiMH battery pack, VTP LTP material allows designers to increase the protective function of the thermal conductivity. Some special application of the patch and VTP Series the AAA battery unit can be used.(Metal Oxide Varistor)