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How do you limit the surge current in a rectifier circuit?
An efficient way to cut down the inrush is to replace the resistor with an NTC thermistor (RT1 in Figure 4). Before the power supply powers up, the NTC thermistor is cool and holding a high resistance. Hence, the high resistance can be used to limit the inrush current during power up transient.
How does an inrush current limiter work?
The nature of the inrush current limiter to self-heat as an increasing amount of current is applied, which generates heat, causes resistance to drop, allowing the current to flow freely. This self-heating effect is the underlying reason that allows the inrush current limiter to work effectively.
How does the inrush current in a DC converter work?
Inrush current is the current drawn by a power system when power is applied or it is turned on. A typical power system is shown in Figure 1. The input EMI filter will include some capacitance connected across the input line. The DC-DC converter will have capacitance internally across its input and output.
How is inrush current limiting used in switching power supply?
Application: Inrush current limiting in a switching power supply Various switch-mode power supplies (SMPS) – which are small, lightweight, and high-performance – are often used as power supplies of electronic devices. At the time of powering on an SMPS, the device is charged with an inrush current with a high peak to charge a smoothing capacitor.
How are NTC thermistors used for inrush current limiting?
It is called an inrush current, and without protection, it may destroy a semiconductor device or have a harmful effect on the service life of a smoothing capacitor. NTC thermistors are used as ICLs (inrush current limiters) to protect circuits of electrical and electronic devices against inrush currents easily and effectively.
Which is the best circuit to limit inrush?
The three types of inrush-limiting circuits designers use most are a negative temperature coefficient (NTC) thermistor, a relay, and a MOSFET bypass circuit. NTC thermistor An effective way to cut down the inrush current is to increase the resistance on the capacitor-charging path – inserting a resistor like that shown in Figure 3.