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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46 views

PSFB - Asymetric current at the secondary

At the 3rd step of the PSFB cycle, the current at the secondary is not shared equally by the two windings that it would be if it were a full bridge. Does anyone can explain why it is not the case ? ...
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Is a balancing diode really necessary for the Balanced Boost converter?

Please pardon all of the information that precedes the question -- I didn't want you to actually have to go read the paper itself. This question is in two parts, but they are really equivalent, so it'...
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58 views

GaN Power transitor said to "reduce EMI"

I have no experience in GaN, I am currently discovering the subject and I was studying a design from Infineon and I found on a GaN power transistor the following benefits: Here is the datasheet: ...
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PFC inductor calculation

I have a question about PFC inductor calculation. Please see the below figure. This is my answer, but I don't know how to only let Lmin equal to Vrms, P, fs. There is a V (output voltage) in there. I ...
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50 views

Flyback primary side control

I read the LT3573's datasheet, I have some questions would like to ask. Based on this block diagram, 1.) What's the main function of the below circuit (red circle). 2.) If I need to detect the output ...
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106 views

Safe residential use of high power switching DC power supplies

I'm looking to power a high power stereo amplifier using a 24V 17A switching power supply or, in another case, using a 48V 7.3A power supply. These are not your typical encased bricks, but rather come ...
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107 views

Why is a capacitor connected across the power MOSFET in the DC-DC stage of most SMPSs?

In many of the schematics of the DC-DC stage of SMPSs, there is an external capacitor connected across the MOSFET switch (across drain and source). Why is this capacitor required? MOSFETs have an ...
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Readjusting a wide range input power supply for higher wattage output. What components if any need to be adjusted?

Currently I am looking through the circuit design and component selection for this 30-W Ultra-Wide Range Power Supply for Protection Relay ( https://www.ti.com/lit/ug/tidu231/tidu231.pdf?ts=...
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63 views

Reverse recovery body diode in synchronous buck converter

I am building a synchronous buck converter from 72 V to 4.2 V 2 A. Is there a way to lower the losses of the lowside MOSFET’s body diode? I am using a switching frequency of 300 kHz and with the ...
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47 views

12VDC SMPS flashing problem

I have a 230 VAC/12 VDC switching power supply that powers some LED strips. Suddenly the LED strips started to flash with 1 second interval. I did a frequency test and the multimeter showed numbers ...
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Design questions for tweaking a Power supply blueprint for higher output

TI has a very good reference for a 30-W Ultra-Wide Range Power Supply that I'd like to use for a different application that would require about 50W. Could I still use the same main integrated circuit ...
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SG3525A power supply suggestion

Today I have an old switching power supply to be repaired based on the circuit SG3525A, which the bridge rectifier and all the transistors are exploded (2 MOSFET IRF740 and 2 BJT BD135). The problem ...
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Is there any simple way to calculate the turns per volt and required core area for a high frequency transformer?

I was trying to find some simple equations for designing a high-frequency transformer. The operating frequency will be 10-15 kHz. I searched many sites and didn't find any simple equation to calculate ...
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Deriving headroom for the 34063

I've hit a design dead-end because, after running the numbers for an SP34063A-driven SMPS, it seems it doesn't have enough headroom. This was not described directly in either the OnSemi or TI ...
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70 views

Diode ratings question

Can I use a 1000 V, 3 A diode instead of a 400 V, 3 A diode? The dead diode is a uf5404, it was in a satellite receiver power supply. The only ones I can find in the market are fr307 and 1n5408. Here'...
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78 views

LTspice - Staircase saturation transformer

I am trying to simulate on a full bridge converter a staircase saturation transformer. I was thinking by adding a very little resistor on one leg of the full brigdge converter, it will in any case ...
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Inductor saturation effect on power converters

How the inductor saturation decreases the cost and weight of the power converter? And how it increases the power density of the converter? What are the advantages to exploit the saturation of the ...
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87 views

What is the min and max input voltage range of a buck converter to maintain efficiency above 90%

I want to design a stepdown converter from 72V lithium ion battery to 12V, 5A. I am torn between using a flyback converter and a buck converter. Which topology will give me maximum efficiency at that ...
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107 views

5V SPDT relay not switching when the coil probes are dipped in water

I have been trying to get a relay to switch when one of the coil probe is underwater and the other probe connected to the positive of a 5V SMPS. The circuit is completed by the negative wire and the ...
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System level behavioral model for PSSR of a switching regulator

In a design I have a switching regulator (buck for the sake of my example). The switching frequency is much higher than the frequency range of interest and can be safely ignored. However, the input ...
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1answer
53 views

How do I calculate the number of turns or inductance while designing a transformer?

I was trying to design a transformer for a SMPS but can’t find any resource to calculate the number of turns and the core area. I know that the turns ratio has dependency with the signal frequency. If ...
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68 views

Does the PFC stage adjust its output power depending on the load requirements of downstream converters?

I am trying to calculate the overall efficiency of a PFC+flyback converter. The PFC boost converter has an efficiency of 0.9 and the flyback an efficiency of 0.89. Depending on the load which requires ...
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54 views

Two switch forward converter - replacing BJTs for IGBTs in welder

So my friend has a broken TIG welder, an Lorch IT 250 GW to be specific. It's quite old, water cooled, has 250A continuous welding current and is powered by 3x230V mains. It was sitting for about a ...
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52 views

Boost converter with regulator

I have set up a boost converter with a regulator in LTspice, but I get a lower voltage at the output than at the input. What could be the reason?
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Soft Start in switching regulator

Preface: I am designing a drone. My choice for stepping down voltage is to use a DC/DC switching converter. After using the parametric search of Digi-key, I selected TPS54495RSAT‎ as my SMPS. ...
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44 views

Can I use common mode power line choke as 1:1 transformer in isolated buck-boost switched mode power supply at 20 - 100 kHz?

I'm planning to build a multi-output power supply that allows output voltages between 0 - 30 V and currents below 5 A. The idea is that I will purchase a number of 30V 5.3A power bricks (unknown if ...
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64 views

Led strip and relay current splitting?

I have a 12 V LED strip that works at 10 W. I want it to run at multiple current configurations with two relays and without the help of a microcontroller. I am attaching a diagram of my intended setup....
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33 views

High Voltage PMOS devices availability

Generic question for experts well versed in semiconductor device physics. Most of the high voltage power switching devices seen are N-Channel (Silicon and Silicon Carbide) with varying ratings. Is ...
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64 views

Sense resistor placement in switching regulator

Preface: I am designing a drone. My choice for stepping down voltage is to use a DC/DC switching converter. After using the parametric search of Digi-key, I selected TPS54495RSAT‎ as my SMPS. ...
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2answers
84 views

Rogue winding on flyback transformer?

I was reverse engineering a battery charger (Lidl brand Parkside 20V battery charger PLGS 2012 A1, with smart functions, among them charge current and termination voltage settings) and came across ...
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60 views

Can we add a current limiter circuit to LM2576 fixed voltage version?

I know I can add an external current sense and comparator circuit to the feedback pin of LM2576-ADJ version to limit current, but can we make such a modified arrangement to a fixed version of the ...
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118 views

X2 polypropylene capacitor for DC smoothing after AC rectification

Can a X2 polypropylene film capacitor be used for dc smoothing at the output of a bridge rectifier? I want to use this capacitor at the input of a power factor correction circuit with a switching ...
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176 views

Boost converter IC layout fails with increased load

First post on here and not very experienced so let me know if there's anything wrong with my post as well as my design. I am trying to layout a boost converter using the PAM2421AECADJR IC I bought as ...
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52 views

DC power supply 10V AC between terminals and mains earth

My DC power supply shows 10V AC between earth and one of the terminals. How can I fix this, and is it safe to probe circuits with an oscilloscope, that are powered by it? The PSU ground terminal is ...
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76 views

Selecting a SMPS transformer

I am in the process of selecting a transformer for my SMPS design and need some help in doing so. I am trying to design a universal input - 54 V constant voltage output SMPS. Looking at the data sheet ...
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59 views

Power supply unit in series with load

I'm looking for the circuit that can operate in series with load. I want to improve poor one in my WiFi light switch. The current one is cutting sine wave to "steal" some power and when ...
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39 views

How to flow high current into a transformer - GaN Application

I would like to design a GaN converter with an output current of 150A. The output is regulated in current (not in voltage). If I am able to increase the frequency, I am able to reduce the size of the ...
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110 views

Transformer saturation when current is flowing

I have a nanocrystalline center-tapped transformer with 2 turns at the secondary and 17 turns at the primary. There are 4 windings at the secondary as each leg of the transformer is parallelized with ...
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SMPS Current Limiting Design

Sample SMPS Circuit 1 Sample SMPS Circuit 2 Considering the above two circuits, how are they able to predict that the max current at the output for 5V is 2Amps and 500mA for each of the circuits ...
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Splitting output power of a PFC stage to three flyback converters

I want to design three flyback converters whose input is taken from a single power factor correction circuit based on boost converter topology. The PFC stage delivers 200 W (400 V, 0.5 A), and I want ...
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What is the purpose of this transistor switch on the line providing VCC to this SMPS controller?

In this SMPS for white goods, the VCC pin 5 of U3 (LD7537) is initially fed from AC Mains through R54, R55 and R53 and once started it is fed from the auiliary winding (N2) of transformer (T1) through ...
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Nominal input current of a switching mode power supply

I was simply trying to design a constant voltage switching mode power supply for a small side project I have. 85 - 275 VAC input and 50 V constant output. As far as current regulation goes, a lot of ...
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158 views

Understanding flyback power supply with weird snubber circuit, and general function?

Hello fellow wanderers of the electromagnetic plains, I'm looking to replicate the function of the below pictured reference design, just a simple 230VAC SMPS using an iW1700 chip (72kHz operation), ...
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Step down 5V Power supply for IoT

I am trying to create common DC power supply to support ESP32 Development board, Servo Moter (MG995) & Fan Motor (0.2A), all required 5V DC. I am considering Hi-Link 5V 4A SMPS Mini PCB Mounted ...
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165 views

Increase switching frequency of boost converter with MAX1771

The MAX1771(always in DCM, has no oscillator) was chosen as controller for minimum component count: no error amplifier compensation, no slope compensation, no current feedback RC filter, no external ...
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Why is there a Schottky diode connected to the low-side switch

I am trying to understand the reason for having a Schottky diode for protection in a buck switch by reading here. To summarize, I can understand why two the switches should not be turned on at the ...
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What is a Ladder Switched Capacitor?

I have recently read several papers with LSC on it (I'm taking care of my Mom 24/7, so I can't find them right now). Are Dickson and Cockroft-Walton considered Ladder, or am I off? Thanks.
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73 views

Phase Margin and Transient Response Contradicting?

I am designing a forward converter that is supposed to work as a pre-regulator for a linear supply. The forward converter is supposed to be able to give output from 4V to 34V and 0 to 5A. While ...
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53 views

Practicallity of winding inductor for high current DC to DC boost converter?

This is a very basic question, not about the various designs of DC DC switched mode power supplies, but the practicalities of the inductor involved. If you want to boost from 12 volts to a much higher ...
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66 views

SMPS Pre Regulator Minimum load

I am designing a 30 V 5 A lab bench power supply having SMPS as a pre-regulator for the linear stage which will keep the SMPS output always 4 V higher than the main output voltage. This means SMPS ...

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