Questions tagged [switch-mode-power-supply]

A switch-mode power supply (SMPS) switches been fully-on and fully-off states quickly to maintain voltage regulation. They offer lower power dissipation and run cooler than linear regulators that continually dissipate power through a transistor.

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27 views

Relationship between switching frequency and controller's crossover frequency in DC-DC converters

I am reading some answers related to my questions based on control loop stability of SMPS. I came across this question. The accepted answer states: A switch mode power supply is essentially a ...
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43 views

SMPS voltage feedback using op-amps

I'm designing an adjustable high-voltage low-current power supply using UC3843 control chip. Basic parameters: Uin = 24 V DC, Uout = 30-1000 V DC, Iout = 10 mA, Uripple < 1 V, fsw = 40 kHz I have ...
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Understanding datasheet for SMPS transformer

Looking at different datasheets of SMPS transformer, I found that the manufacturer always specifies voltage in a certain frequency range. Why is this parameter important? For example this transformer:...
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49 views

Optocouplers driving MOSFETs in an inverter

For many hours I was trying to simulate in LTspice XVII an optocoupler driver for MOSFETs in an inverter. My project is to build a SMPS with linear voltage stabilizer (I didnt put it on the schematic ...
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43 views

Does a DCM flyback always operate in CCM during startup?

In the flyback topology : When dimensioned for fixed frequency discontinuous mode, to me it seems unavoidable that the converter will operate in CCM during startup since v=L*di/dt. And since the ...
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Is the switching speed of MOSFET comparable to that of a Schottky diode?

Assuming identical voltage and current rating, which is having higher switching speed? MOSFET or Schottky diode? In synchronous buck converter, we replace Schottky diode with MOSFET (low side) for ...
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61 views

What is the difference between these two half bridge configurations?

I have seen two different half bridge versions. One has an extra capacitor attached between the load and the neutral point of the capacitor divider. What is the difference?
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Beginner's power supply design

I'm trying to design a bench power supply that can be easily controlled by a microcontroller and is more efficient than a simple linear design (although crazy-high efficiency is not the primary target)...
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52 views

SMPS design problem, low available current

I'm having an issue with this SMPS design where the voltage is correct at approx. 19.45V but I'm getting nowhere near the target of 3000mA The zener voltage on D3 is 18V. R3 is a 1K resistor. When I ...
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Why are boost/buck converters never fully integrated/all-in-one?

Moving from small arduino applications to higher-power applications for work, I've had to switch from using simple linear regulators to switching boost/buck converters any time a different voltage to ...
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Voltage variation and electrical fields Maxwell Equations

I actually know without knowing the reason or the mathematical expression of the physical phenomenon, that if we apply accross a capacitor a voltage which varies in function of the time, it produces ...
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43 views

MIC4830 output voltage too low

I have built the typical applicaiton circuit from the MIC4830 datasheet. I have used the values for 0.4inch2 EL panel running at 900Hz (REL=0.369MOhm, RSW=321kOhm). The input voltage is 3.3V. My ...
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Is it better to use mains power or an external power supply for a rack mount unit? [closed]

I've seen many rack mount audio units that have an IEC connector for direct mains power, and others that have a DC jack for an external power supply (12V DC for example). What are the advantages and ...
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How does an “auto voltage setting” laptop charger work? [closed]

I recently came across a very interesting device for me, a laptop adapter that claims it adjusts its output voltage automatically: https://www.trust.com/en/product/20194-plug-go-universal-90w-laptop-...
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42 views

MCP1630V a battery charger

To charge a 4 cell Li-Ion battery pack, microchip have developped a circuit (board) that I am trying to understand, (the link for the PDF is here:https://www.microchip.com/developmenttools/...
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Making a more efficient replacement for my diode

I am making a boost converter using the LM3481 IC (although it might be considered a sepic topology as well). Typically in a boost topology, you put a diode before the output capacitors so they don't ...
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43 views

Output capacitor current of boost converter

I am simulating a boost converter. The input voltage is 8 V and the duty ratio is 0.3. The load resistor is 1 ohm. I want to plot the output capacitor current. In DTs time when MOSFET is on, the ...
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84 views

Resistor annotated with a frequency

The LT3757 datasheet includes the following schematic: The resistor in the bottom left corner is annotated with a frequency (100kHz). What is the significance of that annotation?
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Line and load regulation testing of flyback converter

I have designed a flyback converter with dual outputs. I have the following queries for performing line & load regulation tests for the same. 1)To perform line regulation on 25 V rail, should I ...
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Bad Waveform on Output of Buck Converter

I have designed a buck converter (poorly) and have been getting terrible noise. I made a post here where I was given suggestions on how to do a proper layout for my buck converter. This post also ...
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Why do some switching regulator require tantalum or electrolytic capacitors instead of ceramic?

I'm looking at this switching regulator: http://www.ti.com/lit/ds/symlink/lm2675.pdf. For its input and output capacitors it recommends tantalum or electrolytic capacitors. It mentions in section 9.2....
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43 views

With a SMPS charging a capacitor bank. What is the power rating of the SMPS?

I'm working on a project to build a 24VDC to 250VDC switch mode power supply for the purpose of charging a capacitor bank. The capacitor bank will be rated at 250V and 180mF. So, the prime power ...
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38 views

Low Dropout Regulator Enable Delay

I have a main buck DCDC 5V that feeds to five different LDOs(3.3V). To create power sequencing, I would like to use a resistor and a capacitor at the input of the enable pin of each LDOs and by ...
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62 views

Techniques for Filtering a Noisy Buck Converter

I have built a buck converter on the TS30011. Unfortunately, I am getting terrible noise on the output. External Parts Used: Inductor Output Capacitors I have been analyzing my design and have ...
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27 views

What's the LC filter arrangement on dual output DC/DC converters?

It's pretty hard to find a filter arrangement for a dual output converter, but I came across the following:- Taken from here. So for the bottom example, is the LC arrangement correct? I always ...
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54 views

SMPS feedback circuit with voltage regulation and current limiting

i’m self learning electronics for a few months now and i choose my first project to be a bench SMPS. Since it is my first circuit design ever i really need some clarification. My SMPS is 2-switch ...
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103 views

Help identifying component in SMPS

I have been working on a Schroff/Cherokee Europe PE1947/23B SMPS (circa 2004?) and have had trouble identifying a component within the circuit. This SMPS features the following outputs: +12v DC @ 8A ...
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Gate Current Calculation and Practical Mosfet Selection

Vnoo3 is the drive voltage, and Ig is the gate current. What I am wondering is: 1) How to calculate the peak Ig on the rising edge of the pulsed gate voltage? For instance, using the spice image ...
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SMPS controller duty cycle resolution

when reading the datasheet for some SMPS controllers like the lm25116, I can see that they operates around 1MHz, but nowhere we can find their duty cycle resolution: 8bits, 12bits, 16bits ? So I'm ...
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Energy in transformer air gap

Here is the following assertion : Question: Why is it commonly stated that in a flyback transformer, the "air gap carries most of the stored magnetic energy"? Answer: We can intuitively ...
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meanwell psu inrush current and temperature sensor

I want to use a Meanwell PCB mounted power supply on my next project. https://www.meanwell.com/Upload/PDF/IRM-20/IRM-20-SPEC.PDF The spec sheet says that it has an inrush current of 20A/115VAC (I'm ...
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58 views

Gate driver using switches UC3842 PWM Controller

I have prepared a crude model of boost controller using PSpice simulator of UC3842 IC Gate driver has Ron and Roff as 1 and 100meg respectively (S3 and S5) and Vout will go to external mosfet or a ...
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61 views

Can a single phase SMPS be converted to run from three phase?

If you have a switch-mode power supply that runs off 240 VAC single phase, is it possible to convert it so that it runs off 3P+N (415V phase-to-phase) by only changing the bridge rectifier? I have ...
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How to prevent voltage droop when discharging a battery?

This is quite an open question, so apologies in advance if you would rather schematics and the like, if you really think this would help I can provide them My problem: boosting from 2x AA Li ...
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92 views

3.3 Volts Output on 1.8 Volt Regultor

On my circuit board, I have three different voltage regulators. I have a 5V Buck converter that goes into a 3.3V LDO and then finally 1.8V LDO. When I power the board with a USB and do not use ...
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54 views

Switch mode power supply inrush current protection

I want to design a suitable PCB for my audio amplifier project. The amplifier boards (both left and right channels) will use almost 4 amps at 24 V at full power. I want to use a switch mode based ...
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TEA1733T switching in small bursts and with very brief on time for [external] FET

I should start, possibly, by saying I am no expert on offline SMPS, but am having a go. I have built up the schematic below: I am getting no proper voltage out of the outputs. The transformer ...
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Why did they use ultrafast diodes in a 50 or 60 Hz bridge?

This is again from an HP power supply (PSU). The incoming 230 V is rectified into 340 VDC and is fed to a switched-mode supply. The odd thing here is that the manual for that unit, HP6023A, ...
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How to extract the switching noise component for this signal data?

A servo accelerometer when powered by batteries has a clean output, but when used with this SMPS supply its output seems like have switching artifacts from the power supply(the datasheet says its ...
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58 views

Abnormal microcontroller circuit behavior when I connect SMPS

I designed a device that calculates current and power using a CT and an ATMega328P-AU microcontroller. The board I designed was simple and I didn't account for noise cancellation on the ADC lines and ...
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35 views

Controlling multiple floating power supplies from a single point

I have assembled a power supply from five HP dps-750rb common slot power supplies. All five units are in series. I have the first grounded electrically and have the other four units modified and ...
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Filter before or after switching regulator?

I will be passing a power line (12V-60Vdc depending on the circumstance) with a lot of noise, 300Hz and above, riding on it through a buck regulator. I want to remove this noise with a filter. I don't ...
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bode plot of LM3481 as boost converter

I have simulated an open loop boost converter using LM3481 average model, given by texas instruments and I got a very strange bode plot (More precisely, strage phase response), please can you tell me ...
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How does this circuit start up?

I'm trying to understand how CI HT7A6322 starts up. Relevant part of the datasheet says: Control circuit power supply. Also provides a charging current during start up due to a high voltage ...
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Conduction Mode in PFC

At a Power-Factor-Correction (PFC) circuit, Why mostly using Continues Conduction Mode (CCM) for high power applications, ex. above 300 kW, and using Boundary Conduction Mode (BCM) or Discontinuous ...
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86 views

How is the impedance of a circuit calculated when non linearity is introduced from a switch

What is the impedance of the following circuit if the switch operates at the same frequency with the input voltage. Since the switch introduces non-linearity to the circuit, how can I calculate the ...
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Pi Filter Calculation

Here is my circuit schematic below. PT4115 feeds LEDs. Load current is 200-215mA and switching frequency is 500kHZ. How do i calculate pi filter or what is the best values for pi filter in this design ...
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34 views

AC Simulation in Power supply simulators

I would like to design a boost converter using LM3481 from texas instruments. To de the job, I have selected TINA TI circuit simulator, where the average model of LM3481 is given. So I have used this ...
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89 views

Are input filters always required for switching power supplies?

This is a follow up to the questions here and here I recently designed a PCB that contained a buck regulator (LM2576 5V). You can see the PCB layout in this question. After converting the input 12VDC ...
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113 views

Mechanical Switch Causes Transients from AC-DC Power Supply

I'm having trouble getting rid of output transients from this Mean Well PSU right after the AC input is switched. https://www.meanwell.com/Upload/PDF/RPS-500/RPS-500-SPEC.PDF The PSU is a RPS-500 ...