Questions tagged [sepic]

For questions about single-ended primary-inductor converters (SEPICs), which are a type of DC/DC converter. Use with the "dc-dc-converter" tag.

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How to calculate components values for LM3421 in SEPIC mode

How can I calculate the components values for LM3421 in SEPIC mode? In the LM3421 datasheet, there is not much information about SEPIC topology. (Section 9.2.9.2 is labelled "Detailed Design ...
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Meaning of these inductor dot symbols

For the following circuit from the NCV5171 datasheet: What is the meaning of a solid dot on one inductor and an open dot on the other?
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Beginner seeking feedback on circuit design: SEPIC with adjustable voltage

I recently got very interested in electrical engineering. After watching a bunch of YouTube videos on circuit and PCB design, I figured it's finally the time to get a bit hands on. I decided to start ...
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3 votes
4 answers
134 views

13-48 V SEPIC - > 19.5 Vout; 0.5 A

I am trying to design a SEPIC converter with the parameters stated above and have already drawn a schematic using the LM5022 IC. I have built the system and noticed a few things: The output voltage ...
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2 votes
1 answer
199 views

Ceramic output capacitor selection for ripple current (SEPIC)

I'm designing a SEPIC converter based on a wide input voltage range SMPS controller (LTC3758). The requirement is for a wide input voltage (10-60V) with a fixed output of 28V @ 1.5A. I'm trying to ...
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202 views

Confusion of the working principle of Isolated SEPIC converter

I am a bit confused about the current flowing in the magnetizing inductance L_m when the switch is off. I am reading a book(Erickson & Maksimovic, Fundamentals of Power Electronics, 2020), ...
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218 views

Why does this SEPIC buck-boost oscillate so much?

I've made this SEPIC regulator based on this design, using a MT3608 boost regulator, which has the same oscillation (ripple) as this question: I've made these changes: C1=100uF, C2=470uF R2(bottom ...
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115 views

Is a SEPIC converter truly isolated?

I have been in two separate design reviews where the SEPIC topology was rejected for an isolated < 40W application. These meetings were at 2 different companies and with different principal ...
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2 answers
77 views

Calculating ripple voltage across sense resistor (SEPIC DC-DC Converter)

I am designing a SEPIC DC-DC converter based on the LT3758 (Analog Devices). In the data sheet the maximum switch ripple current percentage is calculated using the ripple voltage across the sense ...
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62 views

Coupled Inductor for DC-DC Converter ~50W

I'm designing a DC-DC Flyback or SEPIC converter, not decided yet. The converter is used to source some power LED's. The output voltage up to 60V and 1A with an input of 12-24V. The switching ...
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92 views

Powering a 12 V Relay and a 3.3 V Microcontroller with one Power Supply

I'm trying to power the LN298 motor driver in order to use a 12V linear actuator. This motor driver comes with a 5V voltage regulator, so you can power a microcontroller with one power supply. The ...
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1 vote
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32 views

Secondry side pulse by pulse current limit

Coupled inductor SEPIC converter using UC3843. Vin nominal = 14 V Vout max = 30 V Iout max = 2 A According calculations based on many resources the MOSFET's current will be Peak = 7.62 A RMS = 5.3 ...
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97 views

Buck converter after SEPIC converter

I have designed a SEPIC and Buck converter using the TI power designer tool, which I have individually tested, and proved to be working correctly. They are both of the non-isolated type, but when I ...
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SEPIC converter : why average secondary inductor is the output current?

I can't get the reason the why the average secondary inductor current is the output current. Simulation confirms it's true, as well as documentation. But I haven't found any clear explanation. Sorry ...
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185 views

Selecting capacitor for SEPIC converter

I'm looking for an advice how to select capacitors for my SEPIC converter. I have done calculations, but I haven't find Cin, Cs and Cout yet. What seems like a problem is that there are few work ...
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sepic converter using lm3478

Is it possible to make a sepic converter of 120 W using LM3478 ? I am trying to make the circuit in TI web bench but it is not supporting over 12V 3A in LM3478.
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1 answer
270 views

Is there a problem using electrolytic (polarized) capacitor as coupling capacitor in SEPIC converter?

I found this circuit from here and have been thinking about to build it: The author present it as Ćuk converter but I understand it as SEPIC, after reading this and this. Q: My main concern is, ...
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building real simulation in multisim(NI company) of dc-dc SEPIC convertor

hi I am trying to build real simulationin multisim of dc-dc SEPIC convertor how ever in my output voltage i get a lot of RIPPLE . the problem is that I get a lot of spikes in my capacitor current . ...
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1 vote
1 answer
378 views

SEPIC vs. ZETA feedback

When I was reading through the RECOM book of knowledge DC-DC, I found out that the SEPIC converter has more chance of having resonance feedback than the ZETA converter. They mention that the SEPIC has ...
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186 views

How to limit starting current of a SEPIC based LED driver?

I have designed a SEPIC based LED driver which gives 60 V, 350 mA constant output with a good power factor. It is connected with 220 V AC source.Then I have used full-wave rectifier.After ...
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0 answers
78 views

High voltage drop over output diode sepic converter

I made a SEPIC converter please see the wiki for the scematic: https://en.wikipedia.org/wiki/Single-ended_primary-inductor_converter Observation: The output is 12V 2A max. When I use a scope I see ...
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680 views

LTspice XVII problem simulating SEPIC converter

This is the second time I'm trying to simulate a SEPIC converter today. First I went with LT3959, but after hours of trying to make it work, I assumed there is something wrong with the component and ...
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TI LM3488 SEPIC, adjustable power supply down to 0 volts

I decided to make an adjustable power supply with input voltages from 3 to 6 volts (4A), and output voltages from 2 to 12 volts. But I had a thought, that as long as I'm making it, I should make it go ...
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2 votes
1 answer
188 views

Lossless Resistor model in PSpice?

Is it possible to make a lossless resistor model in spice? I want to test the large signal model of my DCM SEPIC converter (without linearizing it). OrCad's PSpice library doesn't seem to have it, but ...
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3 votes
2 answers
8k views

SEPIC vs Cuk vs Zeta Converter

My understanding is that SEPICs, Cuks, and Zeta converters all provide a stable output voltage despite an input voltage that can vary either above or below what is desired. The SEPIC and Zeta ...
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SEPIC converter capicitors calculation

I have got a SEPIC converter design see here: http://www.linear.com/docs/27994 The calculation of the SEPIC converter starts at page 21. For the input capacitance on page 17 they tell you need: \$I_{...
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154 views

SEPIC converter working in BURST mode without having one

I designed a SEPIC using the LT3467 with coupled inductors. It supply 17V starting from a 12V input. On the simulator (LTSPICE) everything works, but on the test board there is a problem. With 70mA ...
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2 votes
1 answer
237 views

Sepic based charger

I have acquired a LT1512 Sepic based controller which is a controller for charging purposes. I have followed the datasheet as much as can, read few articles on how to set it up for my purposes, ...
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1 vote
1 answer
2k views

Compensation Capacitor and Resistor Values

I'm currently working on a Power Electronics project which I will convert 10-28V input DC voltage to 12V DC output voltage. I've deciced to use LM3481/3488 configured as SEPIC in my project. I've ...
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6 votes
1 answer
404 views

Vin: 2-36, Vout: 4.2. Should I use step-up, followed by step-down, or SEPIC?

My application has a small device, which draws about a watt, and is powered through a small dynamo, backed by a battery: The dynamo generates 33 volts at maximum speed, close to L6902's max input ...
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1 vote
2 answers
1k views

Low voltage DC UPS - confirm specs

I've looked at the other answers here regarding building a low voltage UPS and have come up with the following design. Requirements: 1) At least a couple of hours of up time; 2) USB power 5V @500mA, ...
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9 votes
4 answers
3k views

Can I use a common mode choke as a coupled inductor in a SEPIC converter

I do not really understand the difference between common mode chokes and coupled inductors. They are both 2 coils wrap around the same core but I know they have different purposes. I want to design a ...
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5 votes
3 answers
3k views

Isolated DC/DC flyback/SEPIC

As far as I understand the flyback topology, it can be used in both buck and boost converters. What I am not sure about is: Does it also work for the case where buck-boost is needed, i.e. \$V_{\text{...
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2 votes
0 answers
176 views

Why does my SEPIC converter output more power at higher temperatures? What are the implications of this behavior?

I have a Pololu S18V20ALV SEPIC voltage regulator board that is wired to a high-amperage 5V USB power source on the input and a DC brushless fan on the output. The output is set to about 5.5V. ...
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1 vote
1 answer
1k views

LTSpice SEPIC simulation current spikes

I am designing a SEPIC power supply using the LT3758. I have simulated the circuit in LTSpice and all the waveforms are as expected except the L1 current. Here I see massive overshoots when the MOSFET ...
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0 votes
2 answers
149 views

How to choose V_out resistors for LT8494 SEPIC

I am in the middle of a project where i want to use a mcu (ST32F3028U6 with DAC of 2.4V - 3.6V) to control the V_out voltage of a LT8494 SEPIC DC/DC Converter. I understand the basic operation of the ...
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11 votes
2 answers
3k views

How do I size the coupling capacitance for a SEPIC converter?

The app notes I've seen for a SEPIC converter1 all tell me to size the coupling capacitor for ripple currents and voltages. I haven't seen one that tells me how to size the capacitance. Obviously ...
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1 vote
0 answers
2k views

DC/DC Converter MOSFET switching

I am currently building a SEPIC converter. The signal arriving from the MOSFET driver to the MOSFET seems all good, however the Vds doesn't seem to follow the drivers signal and it makes the MOSFET ...
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3 votes
2 answers
1k views

Switching supply burning mosfets, what is happening?

I have been working on a SEPIC converter for an electronic cigarette power supply. This application involves using two 3.7v INR batteries in parallel, rated for an appropriately high current ...
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1 vote
0 answers
444 views

SEPIC converter current waveform question

I am designing a SEPIC converter, powered by 3.7 V Li-Ion cell. Frequency 500kHz, Transformer 10uH per side, 1:1 ratio. Ferrite material #87. Output to be variable by adjusting duty cycle. It has ...
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0 votes
1 answer
285 views

PWM Dimming results in input ripple due to excessive inrush current

I use a constant current SEPIC boost regulator ([TI LM3410X) to run a 8.5V 400mA OLED panel from a single Cell Lithium polymer battery. I have noticed that the input voltage ripple is too much (~1V ...
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1 vote
2 answers
1k views

Troubleshooting a SEPIC regulator (MIC2296)

I am trying to regulate a 5V input, which drops to around 3.5V when a large load is applied. I need to keep the 5V steady, and I am willing to do this at the expense of current, which is why I thought ...
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11 votes
7 answers
16k views

What do phase dots on an inductor mean?

I have a SEPIC supply with coupled inductors. The inductors have phase dots. What do these "phase dots" mean? Is it important to have the phase dot in the same place?
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5 votes
4 answers
6k views

Coupled inductor vs an actual transformer?

What is the difference between a coupled inductor and an actual transformer? The LT3757 datasheet mentions that I need a coupled inductor for the SEPIC to work
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3 votes
2 answers
572 views

12V @ 1A from a 6V to 20V input

I have a 6V to 20V input I want to convert to 12V at 1 amp maximum continuous current. The output must be the same polarity as the input, so that pretty much means a SEPIC is the only way to go... ...
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