# Questions tagged [buck]

A non-isolated DC-DC converter topology which outputs voltage less than or equal to the input voltage

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### Why do smaller loads require larger inductors in buck regulators?

The MC34063 Application Note lists the equation for calculating minimum inductor size as follows: $$L_{min} = \frac{V_{in} - V_{sat} - V_{out}}{I_{pk}(switch)} t_{on}$$ But this implies that as Ipk(...
4k views

### Why would a buck converter IC fail and blow up?

I have a deployed design in which we are experiencing a high (~4%) failure rate in the 12V to 5V step-down buck converter portion of the PCB. The buck converter's role in the circuit is to step down ...
15k views

### How important is self-resonant frequency for an inductor when used in a fast (~3MHz) buck SMPS?

I'm using the LM2734Z, a 3 MHz buck regulator. It's really fast which means it has a small inductor. One of the things I'm wondering is how important is the self-resonant frequency of the inductor? I'...
12k views

### Why do buck (step-down) switching regulators require an inductor and diode?

So, I understand, at least at a basic level, the method of operation of switching converters, both buck and boost. What puzzles me, though, is why buck converters in particular aren't simpler. Why ...
9k views

### For a small Vin-Vout difference, is it worth using an LDO vs a buck regulator?

I want to step down 5V to 3.3V at around 250mA. As far as I see it, there are two options to consider: Buck: more space, higher cost LDO: less space, lower cost, more difficult to remove heat(?), ...
10k views

### How do I select the correct inductor value for the following buck regulator?

First of all, I suck a bit at math, and I'm no electronics genius, so the stuff I do is for fun and for learning purposes... I'm working on a buck converter circuit to convert my USB Vbus 5V to 3.3V. ...
20k views

### Is it ok to connect the output of buck regulator in parallel?

I am using MCP16322 buck regulator powered from 12V and outputs 5V and 2A. Is it ok to connect the output of two of these in parallel? Does connecting the outputs in parallel mess up the maximum ...
1k views

### Where do the oscillations on the output voltage of my buck converter come from?

I am currently building a buck converter. Its main parameters are the following: 24V input 5V/3A output Able to sustain large load transient currents caused by the switching of power LEDs (~2A) I ...
2k views

### High current buck converter has excessive ringing and poor regulation

I am designing a power supply to power two fiber-coupled diode arrays for a solid state laser. The diode arrays need a current controlled source of about 50 A and will have a voltage drop of < 2.2 ...
3k views

### Noise problem with buck/boost switching regulator

I am designing a electrical device for a research project (I'm a PhD student, but unfortunately not EE!). More info on the device can be found at http://iridia.ulb.ac.be/supp/IridiaSupp2012-002/ The ...
1k views

### 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 ...
4k views

### What is the purpose of using MOSFET instead of free-wheeling diode in Buck topology?

(Source) I usually see Buck circuit models in which a MOSFET is used instead of a free-wheeling diode. What I understand from the Buck topology is, when the upper MOSFET is off, it doesn't matter ...
2k views

### Why do we clock Buck Converters?

Apologies if this has already been asked, but I couldn't easily find an answer. So - We all know the basic design of a buck converter: Closed-loop clocked PWM into a low-pass filter. But my ...
3k views

### Is it better to boost or buck?

I'm making a solder fume extractor from an old PC fan (4-pin PWM), driven by a mid-range PIC. The fan needs 12V @ max 0.28A for power and a 5V PWM @ max 5mA to control the RPM. So I'll be running the ...
2k views

### Routing a buck/boost DC/DC converter

I need some help with the layout of a power supply. I botched the first two iterations as I do not have the necessary experience, and I would like to avoid another costly run. For the sake of ...
3k views

### Why do we use closed-loop feedback in buck converters?

My power electronics professor spent most of his life in the time domain and in application-specific theory (SMPS-only vocabulary). For me, a buck converter is basically a square wave (generated by a ...
11k views

### Low side N-Mosfet buck converter

I often see schematics of basic buck converters. The majority of these schematics use a P-Mosfet as high side switch. Why is this design preferred over a low side, N-Mosfet buck converter? simulate ...
5k views

### Remove audible noise generated by buck converter

I'm dealing with a buck converter using an ISP452, an inductor and a capacitor to act as a buck converter driven by a PWM signal coming from a microcontroller. Some part of the circuit is producing a ...
925 views

### Is this normal Buck Regulator behaviour?

I recently got around to trying out buck regulators, my results weren't what I was expecting though. For one the ripple voltage seems a little high to me, It's about 800mV with no load and goes up to ...
1k views

### Buck converter, squeaking/whining inductor

I have a problem with my homemade buck converter. It is based on a TL494 control chip with my discrete MOSFET driver. The problem is that my inductor squeaks and whines, when the output current ...
2k views

### Boost or buck regulator for battery life?

I want to make a wireless sensor node that will run at about 2.5v. I am trying to decide between running 3 alkaline batteries in series with a buck converter or in parallel with a boost converter. I ...
4k views

### SMPS PCB Design Critic

Oldest versions of this post can be viewed through this link. This is my re-designed layout. What is your view again? 10-32V to 5V 1.2A SMPS Buck Regulator Design. The IC is IFX91041 from infineon. ...
17k views

### Calculating size of cap & inductor for buck convertor

What is the idea of choosing inductor & capacitor value for buck DCDC convertors (no specific part number, in general)? I've tried random one with low resistance, and it kinda works, but want to ...
2k views

### Best solution to get 3.3V from 5V-20V @ 250mA

For my Super OSD project, I need a +3.3V supply at 250mA from a variable input of 5.5V to 20V. Cost is a concern, as is size. Originally, I considered an LM317 in a SOT-223 package, due to the small ...
5k views

### Buck switching regulator based on ATtiny84a — please critique!

Here is an attempt at designing a buck regulator based on a ATtiny84a as the PWM controller. It should go from a 4S LiPo battery (12.8 - 16.8 volts in) to a reasonably regulated 12V output, used to ...
3k views

### Multiple buck converters on the same PCB, should switching frequency be the same?

I have a question regarding dc-dc buck converters. I need to supply multiple different voltages on my board and I am very limitted with power this is why I need to use high efficiency converters. If ...
1k views

### Routing Considerations for a Buck Converter

I am looking to build an adjustable output buck converter with the following requirements: Output 1.25-15V Input 20-24V Max current 5A (with limiting) Max output ripple 100mV (preferable but less ...
2k views

### Switching regulator output is unstable

I have a problem in buck regulator. I'm using L4970A to make a buck regulator with a variable output that can be adjusted using a potentiometer. Output is becoming a ramp when I set the output ...
2k views

### Output capacitance effect on stability of DC/DC Buck Converter?

How does having more or less capacitance at the output of a DC/DC buck converter contribute to the location of the poles and zeros. Is there a way to crudely make this calculation.
1k views

### Critique my SMPS buck design

I'm using an LM2734 buck regulator to get +3.3V at 400mA. The datasheet is unclear on how to lay out the supply, so I tried to follow some common sense, keeping all power traces short where possible. ...
2k views

### Maximum limit on the Buck converter inductance value

I found the minimum inductor required for a buck converter using the following formula - L_1 = \frac{V_{in\,max} - V_{out}}{I_o \times K_{ind}} \times \frac{V_{out}}{V_{in\,max} \times fsw}...
7k views

### How to control a buck-boost converter circuit from a microcontroller?

I'm reading about buck-boost DC-DC converters lately and one thing is still not very clear for me. Most of the converter ICs that I've seen have a feedback loop input pin. For example LTC3780 requires ...
2k views

### When did DC-DC buck converter modules become so popular?

Is it just me or from maybe since 4 years ago every project online for hobbyist electronics is using switch-mode power circuits in them? Looking back 15 years ago at projects from when I started doing ...
4k views

### Do buck converters increase the amp hours of a battery?

I've read that they are 90% efficient compared to linear regulators so given the relationship between volts and amps and I want to power the project off of a 12v battery that has 18Ah and is charged ...
847 views

### Is there a reason to use smps regulators over modules

I'm just discovering that TI have switch mode power modules as well as regulators. For example they have the LMZ12001 which would be significantly easier to use than the TPS62150 regulator. Elektor ...
3k views

### Can there be “too much” capacitance on a buck regulator output?

I've an MPM3610 buck regulator module with an integrated inductor of 0.47 ĀµH and a fixed internal compensation. It employs constant-on-time regulation. The datasheet gives some application ...
6k views

### Why does this buck converter output such low current?

I'm making my first attempt at building a buck converter, as a constant-current supply for a 700ma LED, from a 5V or 12V supply. I have it working with the parts I had on hand, at about 88% ...
12k views

### Bi-Directional Buck Boost Converter

I'm trying to build a Bi-Directional buck-boost converter. The input should be between 9-12 and output should be 12. Can any one recommend a good topology to follow. I also have a few conceptual ...
2k views

### Extract 5W low voltage power from 3000W high voltage source

I have a solarpanel array that generates 600V, 5A (3kW). I want to create a small electronic unit to measure the DC current and voltage and transmit this wireless. For this I have an electronic board ...
5k views

### Efficient low-power buck (step-down) regulator IC for Li-Ion - 3.3V conversion?

It's not easy for electronics novice to find good element base, so I hope this suitable question. Requirement: Efficiently power a lean, 3.3V-based MCU design from a Li-Ion battery. "Efficient" ...
845 views

### Change voltage without consumption

Is it possible to change voltage without consuming power? I have a 5V Arduino circuit that makes use of a wireless chip (NRF24L01) that runs on 3.3V. My current approach to get 3.3V out of a 5V source ...
368 views

### Problem with Bode diagram in LTspice

I am working on a buck converter and I want to obtain the Bode diagrams of the open-loop circuit. The below circuit is what I made. However, the DC-gain is -96 dB while it should be very small around -...
4k views

### Behavior of Boost and Buck Converters

I have a couple questions about boost and buck converters. First, do they try to hold the output voltage constant, or do they alter the input voltage by a constant factor? For example, if I change ...
2k views

### Determine efficiency of converter

I would like to determine as accurately as possible (ideally within an error limit of +/- 0.25% or better, but I guess that's nigh impossible) the efficiency of a converter, using a simple method. I ...
1k views

### Buck converter MOS Drive resulting in overheat

With the schematics below, which is a low side driven DC/DC buck converter similar to this post: The LINE voltage is about 300 VDC and controls a 24V halogen lamp connected to J1. C2, C3 are rated ...
680 views

### Reduce output current ripple on hysteretic buck converters

I am learning to use a new type of regulator: a buck with hysteretic control, therefore with no fixed frequency and no output capacitor. As example, I was trying out the ILD4001 for an LED driver. ...
128 views

### Can I decrease voltage to get higher amperage?

If I have for example a battery that outputs 10 V but with a maximum of 0.5 A. If I took the output of the battery and entered it in a buck converter to get 5 V will I get the same 0.5 A at 5 V or I ...
1k views

### USB-C Power Delivery with a buck converter

Following on from my previous question: The project I'm designing requires a peak current of 5V @ 6A. The average current draw will be more like 2A. The reason I'm looking into USB-C is that I want ...
2k views

### Snubbing DCM (nonsynchronous) Buck converter

FINAL UPDATE: I've posted an outcome report below. I'm very satisfied with how this has come out and I learned a lot in the process. More details and before/after shots in the answer below. Thanks to ...