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.
What is the term for an inrush current?
At the time of powering on an electronic device such as a switch-mode power supply (SMPS) or an inverter, the device is charged with an instantaneous abnormal current with a high peak. 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.
How to calculate the energy of an inrush resistor?
Thus if you have a large audio amplifier with 100,000 uF capacitors on +50v and -50v rails, the energy stored in each will be Energy = 1/2 * C * V^2 = 0.5 * 0.1Farad * 50 * 50 = 2500 * 0.1 * 0.5 = 125 joules Assume your surge-limited resistor dissipates that energy in 1/120 second.
What does inrush current in SMPS stand for?
Inrush current also refers to the non-repetitive maximum forward overload current that causes the junction temperature to exceed the rated junction temperature due to circuit abnormalities.
How to limit startup surge current of SMPs?
When we designing low-power switching mode power supplies (e.g., maximum a few watts), directly use power resistor to limit the inrush current can be a cost-efficient solution. This solution is not power-efficient because the resistance is almost constant no matter it’s in the startup period or during the working phase.
Which is larger the inrush current or the steady state current?
The inrush current of the switching power supply refers to the peak current flowing into the power supply equipment at the instant the power is turned on as shown in the below figure. Since the input filter capacitor of the charger quickly charges, the peak current is much larger than the steady-state input current.