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An inrush current limiter is a device or devices combination used to limit inrush current. Passive resistive components such as resistors (with power dissipation drawback), or negative temperature coefficient (NTC) thermistors are simple options while the positive one (PTC) is used to limit max current afterward as the circuit has been operating (with cool-down time drawback on both).
Consequently, they are generally chosen for lower power circuitry, where the additional ongoing power waste is minor. Inrush limiting resistors are much cheaper than thermistors. They are found in most compact fluorescent lamps (light bulbs). They can be switched out of the circuit using a relay or MOSFET after inrush current is complete.
It is known as a current-limiting diode (CLD) or current-regulating diode (CRD). Internal structure. It consists of an n-channel JFET with the gate shorted to the source, which functions like a two-terminal current limiter (analogous to a voltage-limiting Zener diode). It allows a current through it to rise to a certain value, but not higher.
In most circuits, this means pulling an enhancement-mode MOSFET's gate voltage towards its drain voltage turns it on. In a depletion-mode MOSFET, the device is normally on at zero gate–source voltage. Such devices are used as load "resistors" in logic circuits (in depletion-load NMOS logic, for example).
Closed-loop regulator circuits using the TL431 are always designed to operate in high transconductance mode, with I CA no less than 1 mA (point D on the current-voltage curve). [8] [7] [2] For better control loop stability, optimal I CA should be set at around 5 mA, although this may compromise overall efficiency. [30] [7]
Active constant current is typically regulated using a depletion-mode MOSFET (metal–oxide–semiconductor field-effect transistor), which is the simplest current limiter. [2] Low drop-out (LDO) constant current regulators also allow the total LED voltage to be a higher fraction of the power supply voltage.
In digital circuits, subthreshold conduction is generally viewed as a parasitic leakage in a state that would ideally have no conduction. In micropower analog circuits , on the other hand, weak inversion is an efficient operating region, and subthreshold is a useful transistor mode around which circuit functions are designed.
Except at low collector-emitter voltages, the secondary breakdown limit restricts the collector current more than the steady-state power dissipation of the device. [3] Older power MOSFETs did not exhibit secondary breakdown, with their safe operating area being limited only by maximum current (the capacity of the bonding wires), maximum power ...