# 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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1 vote
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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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### 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 ...
170 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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### 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), ...
199 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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### 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 ...
1 vote
71 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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59 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 ...
86 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 ...
1 vote
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 ...
89 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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59 views

### 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 ...
169 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 ...
107 views

### 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.
241 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 . ...
1 vote
354 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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1 vote
183 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 ...
77 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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652 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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### 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 ...
7k 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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### 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
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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### 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 ...
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 ...
1 vote
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 ...
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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439 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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277 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 ...
1 vote
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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### 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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### 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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