Questions tagged [inrush-current]

The high current, that often occurs when first plugging an appliance in the power supply.

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2 votes
1 answer
43 views

Efuses, inrush and output drooping

Here's a simplified efuse diagram: Here is the efuse configurations in my circuit: The load is not present on this pcba. There is a 100mm long cable connecting this board to the load which is a ...
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0 answers
65 views

How large is too large a capacitance across SMPS?

I have a circuit that operates from a 16 VAC input from a transformer. For the purposes of this question, just consider it to be a linear power supply: AC -> full wave bridge rectifier -> large ...
1 vote
1 answer
27 views

Inrush rating of relays

I have trouble understanding the specification for inrush contact in relay contacts (more or less the issue in SMPS inrush time) Background: I have some beefy power supplies (about 16A at full load) ...
8 votes
6 answers
1k views

How to find the root cause of this relay failure

The following is the schematic for the relay section of the board: VBAT: 45-56 V. RY_REAR_MOT: Power to the front motor controller RY_REAR_MOT_EN: 3.3 V enable signal from the MCU. On power up, this ...
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2 votes
0 answers
35 views

Sensitivity of Inrush Current Circuit

I'm new to LTSpice and analog design - I'm having a bit of a struggle getting a feel for the behavior of this inrush limiting circuit. Stole the design from another SE post, but playing with the ...
0 votes
1 answer
77 views

Add inrush current limiter to board for USB compliance

I have no experience with current inrush limiter designs. I have to design a simple prototype in which I have to adapt a USB port to be USB compliant but instead of 5 V to 3.3 V (nothing else changes) ...
0 votes
1 answer
52 views

Maximum inrush current and contact rating?

I am doing a hobby project where I am using a thermostat which has a contact rating of 230 VAC, 5 A. Please see below thermostat details (RS link also contains full datasheet). I want to drive a ...
2 votes
0 answers
37 views

Inrush NTC thermistor vs. frequent on/off

NTC thermistors has high resistance at normal temperature, thus limiting the effect of a surge of current during power-up. Its resistance lowers after itself heating up during normal operation, ...
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0 votes
2 answers
78 views

Understanding inrush current and mitigation methods

I want to be able to automatically switch on an AC-DC power supply edit for clarity: it's a constant current LED Driver [edited again for further clarity- the driver won’t actually be driving LEDs- ...
0 votes
3 answers
69 views

Does limiting inrush current prolong inrush time?

Let's say you have a power supply that at 110 V draws 1.3 A max in its steady state, but has an inrush of up to 50 A. If you want to limit that inrush current to 5 A, you could use a 22 ohm resistor. ...
4 votes
2 answers
521 views

Will this method theoretically reduce inrush current during relay turn on?

When a relay is connected to a purely capacitive load and an AC supply voltage is turned on, it will experience inrush current. Since the potential difference of an AC voltage can be represented by $$...
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1 vote
3 answers
63 views

Rectifier circuit behavior - Need an intuitive understanding

Case1: OUT Series res = 10 ohm -> spiky input current reaching upto 15 A -> capacitor charging fast After a long time: Case 2: OUT series res = 100 ohm -> almost sinusoidal input current ...
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1 vote
1 answer
101 views

High side n-MOS driver without charge pump

I couldn't find details of this circuit configuration in an internet search. Most online results are about P-MOSFET in high side path or N-channel MOSFET with charge-pump/IC based driver. simulate ...
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1 vote
1 answer
48 views

Resistor surge current rating: Why is the pulse energy withstand capability lower for short duration?

As per an online surge capability calculator, the pulse energy withstand capability is low initially and increases with higher pulse width. In short, we are not allowed to pass a narrow high current ...
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2 votes
1 answer
90 views

Limiting cold-start current of an SMPS by an NTC

I'm using this SMPS (12 VDC, 12.5 A model) and in my application in steady state the SMPS draws much less than one ampere from the AC line. But as you see its datasheet mentions its cold-start (inrush)...
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2 votes
2 answers
116 views

Model positive exponential current curve on LTSPICE

I am trying to model the inrush current for a contactor. From the specifications I should get something like this: The hold current is 0.13A and the inrush current is 3.2A. This is controlled using R3 ...
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60 views

Inductor calcualtions to limit inrush and avoid oscillations in power line

I want to design a circuit that is able to supply my load with 12V at 2.3A for around 10ms when the power is switched off. The capacitor size will therefore be 23000 uF, assuming a 1V sag. Applying ...
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0 votes
2 answers
137 views

Relay does not turn on when using a 2.5A 12V power supply

I have a relay that I am using for a project. The relay datasheet is here. I am using a 12V DC 2.5A power supply to supply power to the relay above, datasheet. From the datasheet, however, I saw that ...
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0 votes
1 answer
72 views

Bigger NTC = better protection?

A 2.5 ohm NTC is used in the following PFC booster. I've got a 20 ohm one. Can I use it instead of 2.5ohm one? Does it provide better protection or does it disturb the normal operation of the circuit?
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3 votes
2 answers
116 views

Is stall current generally equal to inrush current?

I haven't been able to find a clear or definitive answer on this, and I've been wondering about it for some time, now: Does the peak inrush current of an electric motor equal the peak stall current of ...
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6 votes
2 answers
310 views

Are inrush thermistors thermally insulated?

Vaguely related to this question but with some different questions and a different component. For an inrush-limiting NTC thermistor such as the Ametherm SL series: It seems purposefully designed to ...
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0 votes
1 answer
88 views

VFD filament inrush current resistor

How can I calculate the resistance for a minimization inrush current effects, to increase the life of the filament of a VFD tube (IV22). Or is there another technical solution to prevent the filament ...
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1 vote
1 answer
107 views

Break peak inrush current

I want to renew a 30 Year old line-filter 230V AC for an electronic device. At the end of the filter is a 230V transformer with 9 secondary outlets: 5.8V, 51.4V, 16V, 13.3V, 9V, 9.8V, 18V, 80V, 100V. ...
1 vote
1 answer
118 views

Why is my battery showing a huge negative inrush current in my designed charger model?

I have a three-phase charger model on simulink as shown below, with a three-phase active front end converter followed by a phase-shifted full bridge DC/DC converter. The circuit is working pretty ...
2 votes
2 answers
220 views

Inrush current handling for relays

I am building a controller (ESP based) to sit in front of a Meanwell LED Driver (HLG-150H-12B). I intend on using a trigger relay module to switch the 230VAC-Live into the HLG, however I am slightly ...
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1 vote
1 answer
58 views

Load current high-side power switch

I have some motors connected to a battery which I start with a switch. I suppose they have some big capacitors inside their drivers so when I turn on the motors with the switch, they draw a big ...
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3 votes
3 answers
525 views

Would this inrush current circuit work in practice?

I am building a USB hub circuit, which, because of the 120uF capacitance requirements on upstream USB ports, means that I need to charge those large capacitors in my circuit. However, my hub will be ...
4 votes
4 answers
737 views

Limit inrush current for USB and large capacitors

I am building an ESP32 custom board (project link and full schematics/layout.) I want to add USB to it for programming only. Power Supply: USB to serial: During normal operation, the board will be ...
0 votes
1 answer
117 views

Limit inrush current to capacitor bank

My goal is to drive a beefy solenoid (1.6 Ohm / 1.5 mH / 50ms actuation time, once every 1-2 seconds) from a 36mF (3x12mF in parallel) capacitor bank at 24V, charged from an 1A PSU. This capacitor/low ...
0 votes
1 answer
160 views

Choice of AC/DC power supply for PTC heater with inrush current

I want to power 2x PTC heaters mounted in parallel with a 24VDC power supply (this one). If possible I would like to avoid using a current-limiting system to handle the inrush currents. The specs of ...
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0 votes
3 answers
195 views

Motor Controller doesn't precharge

I want to include a precharge resistor in parallel with my contactor to charge up the capacitors on my motor controller. This way, there won't be a large in-rush current through the contactor when I ...
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0 votes
0 answers
56 views

Ramping up Regulator Voltage on Switch On

I'm currently trying to design a supply using a low dropout regulator capable of 1.5 A that has a high capacitance of up to 1 mF at its output. To limit inrush current I would like to ramp up the ...
0 votes
1 answer
118 views

Use SCR and resistor as an inrush current limiter

I try to design an inrush current limiter using an SCR S2800F (https://datasheetspdf.com/pdf-file/1129612/Motorola/S2800F/1) and a resistor, as shown in the below diagram. A 600 VDC power supply ...
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0 votes
3 answers
155 views

Estimating load capacitance from inrush current

I need to estimate the capacitance of a load for choosing a PSU for it, as they state the maximum capacitance. It is a strobe light so I suspect it will have quite a bit of capacitance. I've tried ...
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0 answers
94 views

How to spec a inrush current resistor?

I want to know how do I spec a limiting resistor for the below circuit: The relay used is this. The power supply input is 48V and the output is 12V DC. First switch SW1 is pressed which powers the DC/...
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1 vote
1 answer
143 views

Control PMOS or NMOS for Soft Start with Variable Voltage Source (Battery or known series string of solar)?

I have a soft start circuit that looks like so: The load will actually be a synchronous boost/buck converter, and ultimately this could also have an AC source instead of just DC and have a rectifier ...
0 votes
1 answer
79 views

Why AC motor driver shorts out?

I have been working in a VFD using an AC motor driver FSBB30CH60DF and making control of it using a dspic30f4011. As you can see in the attached circuit schematic, the mains supply is a single phase ...
0 votes
2 answers
76 views

Clamping inrush current in a lighting circuit

I use a relay to switch on/off lighting circuits with lots of LEDs. The relay switches the mains supply so must run happily with 110/220/240 Vac. The relay I'm using is rated for an 800 A inrush ...
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1 vote
1 answer
224 views

For calculating inrush current in a ceramic capacitor , do we need to consider the effective capacitance after derating for dc-bias effect?

Inrush current happens when capacitor is initially charged from 0V to the intended rail voltage. What should be the effective capacitance to be considered during this charging? -Since the voltage ...
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1 vote
1 answer
328 views

Switch-on time of an active p-channel MOSFET current limiting circuit

I have recently posted a question on the design of an inrush-current limiting circuit: Current limiting circuit with P-Channel MOSFET I have decided to post a new question on how to analytically ...
3 votes
2 answers
531 views

Current limiting circuit with P-Channel MOSFET

I am designing a simple inrush current limiting circuit with a P-Channel MOSFET: The simulation shows a 48V source that switching on with a fairly fast rise time of 1ns. The Drain-Gate capacitor ...
1 vote
3 answers
108 views

Inrush control transient at power on

I have a circuit with a not-so-small capacitor on the supply and I need to reduce the inrush surge; as a matter of fact the power supply breaks after a while (these cinese supplies are not fun) I ...
0 votes
1 answer
90 views

Is the dipping in VCC caused by inrush current of charging 1 uF and 0.1 uF capacitors?

I'm powering MSP430FR5994 microcontroller from a power supply using a 2.2 V regulator. This regulator can source up to 200 mA. When MSP430 turns on, it starts to charge a 1 uF and 0.1 uF by driving ...
0 votes
0 answers
30 views

What are the implied peak current ratings of GFCI's?

Using GFCIs with transformer or other high-inrush current loads is problematic, because in some designs the differential transformer core can locally saturate and produce an invalid output in the ...
0 votes
0 answers
92 views

Active inrush current limiter using relay

I'm concerned about the delay of a typical relay used in this circuit: DC: voltage from a low quality switching regulator. R : high wattage current limiting resistor. Cap : group of parallel ...
0 votes
2 answers
382 views

Improving this circuit from Texas Instruments note (inrush current)

this is an example circuit in this PDF from TI. (page 19, inrush current stuff) Description : In steady-state operation, Q1 is fully turned on and load current flows through the series sense ...
1 vote
1 answer
92 views

Would sparks from connecting power adapter to DC jack cause issues to a circuit?

When connecting a power adapter (19V) to a circuit through a wall mount DC jack, I get these sparks. Would this cause any damage to the circuit, and if so what would be the solution other than not ...
2 votes
4 answers
398 views

Limiting the Inrush current of the Boost converter device?

I have a source of 24 V and I cannot draw more than 2.4 W from the same. This means I cannot draw a current more than 100 mA from this supply. Alongside the LM5001 boost converter, it also has some ...
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3 votes
0 answers
85 views

High-side mosfet switch placement

this is a power circuit I'm trying to complete: the button at top turns the curcuit on, supplying VCC to mcu, and the MCU will output a high signal to a pin (marked in pink) which turns the N-MOSFET ...
0 votes
1 answer
205 views

Super Basic Inrush limiting for super capacitors

I have 6 x 500 farad super caps in series. I want to use them to smooth voltage dips in a 12v system that is powered by a DC-DC converter. Currently my application is a water pump (desalination) ...

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