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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questions
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1answer
32 views
Buck-Boost Transformer with Three Phase Wiring
I live in a residence with 120v / 208v electrical service. (Measured as leg1: 124v, leg2: 125v, 215v across legs)
I am nearly certain that the service is the result of two legs of three phase power. ...
0
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3answers
63 views
why are non isolated buck converters a safety risk with 120V DC?
So i've come to understand that buck converters CAN be used for 120V to 5V BUT they are not becuase they are often a safety risk. I also understand that they can be used if they are away from a ...
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0answers
12 views
Buck converter as current source - capacitor influence
I would like to find some documentations about buck converter as a current source. I found nothing interesiting on internet. If you know particular links. It would be a great pleasure to see them ! I ...
4
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1answer
46 views
36x LED 5730 in series: diodes burnt when LED driver (based on BP9833A or MT7854BD) powered up
Background:
I have 18W, 36 LED lamp fixture which I cannot change.
Originally it has 2x parallel 18off 5730 LEDs and 300mA driver. It works for some time, but diodes starts burning. I thought that ...
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0answers
43 views
How to split high current low voltage? Voltage regulators , current regulators(?)
I am using a 20v dc laptop charger that supplies 4 amps. I need 5v dc 4 amps. When I use a linear voltage regulator it’s too much current to pass through safely.. 15 amps change and 4 amps, so I use a ...
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1answer
54 views
Which buck converter can be used for 120 V AC to 5 V AC rated at 5 amps?
I have used buck converters that can move from 30 V DC to 5 V DC, their maximum current is set at 400 mA, I need 3.5 amps. I am looking to move from 120 V AC to 5 V AC. I'm then going to change it to ...
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0answers
27 views
Is multi-output buck converter or a power distribution board better choice for a robotics project?
I have a 20V power bank which I am using for my project. I need to power two components at 12V. Should I be using a power distribution board (which can supply 12V as mentioned on the board) or a multi-...
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1answer
123 views
Why does my comparator not compare?
I have designed a buck converter and I am baffled with its comparator's functionality. The op-amp comparator does not give a PWM, instead it gives an amplified ramp.
What am I doing wrong?
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2answers
54 views
Distributing the output capacitance of a buck regulator
Buck regulators often specify the value and placement of the output capacitor.
Typically 10µF placed very close to the buck regulator.
However, what would the effect be of replacing the 10µF output ...
0
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3answers
72 views
Current Sensing on positive and negative voltage rails
I'm working on a design that uses two separate buck regulators to generate a positive and negative voltage, and I'm trying to implement current limiting with a current sensor. However, I am running ...
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1answer
77 views
Why Gate voltage must be higher than source voltage in N-MOSFET as High side switch?
In many circuit, like buck converters, MOSFET used in high side for switching, I've came across the term that Gate voltage with respect to ground must be greater than source voltage by +8V.
For ...
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76 views
Buck converter output instability
First post here, mechanical engineer with not too much experience in designing circuits.
I'm trying to control a DC motor torque via a buck; the motor is driven, so it's acting as a brake, and I'm ...
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3answers
51 views
Solar DC circuit: Preventing Buck Converter from Dropping out Due to Motor switching on/off (in Parallel)
I have an off-grid orchard which has a well pump running directly off of a 24v PV array. (27-32v when at full power) Parallel to this direct circuit, I have a buck converter to power a Raspberry pi (...
4
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1answer
229 views
PCB Layout advice for high current buck converter
I am building a dual high current buck driver for driving two fiber coupled laser diode arrays. This is my second attempt at a board -- my first attempt had excessive ringing due to the board layout (...
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0answers
39 views
How to model / control a FCCM buck (variable frequency)
I am trying to control the voltage of a buck in FCCM mode (where the half bridge grounds the inductor until the inductor current goes negative by X mA, and then turns it on again), but I am suffering ...
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0answers
24 views
Zener diode at the output of High-Side Buck Converter
I'm designing a buck converter based on UCC28881 and this Reference Design.
The datasheet for the UCC28881 states that:
9.2.1.2.5 Pre-Load Resistor (RL)
The pre-load resistor connected at the ...
0
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1answer
35 views
Input capacitor in buck converter
I've chosen this Reference Design as starting point. Here the schematic. I'm using full wave rectifier instead.
I'm designing a buck converter with these requirements:
Input voltage: 120-690Vrms AC ...
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1answer
29 views
Reverse voltage in LED buck converter circuit [closed]
The circuit
simulate this circuit – Schematic created using CircuitLab
Everything is fine except when the switch is open, I measure ~-3.5V on the points marked.
Why is that and is it ...
0
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1answer
28 views
Limiting the current with the LM2679
I'm building a power supply, and I'm trying to see if the LM2679 will fit my needs. I like how it's similar to the LM2596 as well as the fact that it has a pin to limit the switch current. However, I ...
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1answer
22 views
Buck Converter with RLE Load
I am trying to calculate the duty cycle of the buck converter as in the figure for discontinuous conduction mode of operation. I have worked to the math and have got the following graph as in the ...
2
votes
2answers
85 views
Limiting input voltage for buck converter
I want to power some micro controllers and a couple of leds on my electric bike, counting up towards 5 Amps.
Power supply is a 36V battery, with a range of about 42V to 33V. This voltage is to be ...
2
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2answers
47 views
Overloading buck regulator
I'm having a hard time explaining to myself why the output voltage of a buck regulator drops at the load when the load pulls more current than the max limit of the buck regulator.
Can someone help ...
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1answer
19 views
Buck converter simulation issues
I am trying to use a buck converter to step down a 48v to 33v. The confusing part is that I am trying to simulate it using LTspice and I can’t figure what how to control the nmos with pulse width ...
1
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1answer
36 views
Buck converter ringing on rising and falling edges before failure
I have recently designed a PCB with a buck converter based on the LM3671 buck converter IC from TI to step down 5V to 3.3V. However, there is ringing on the rising and falling edges, and after a short ...
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3answers
66 views
Is it better to have a higher Vgs than Vds on a MOSFET (n-channel)?
I've been studying MOSFET switching applications recently, and have been playing with the Circuit Simulator Applet here. In my diagram below, I have Vds usually set to either 12 or 14, as I am trying ...
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2answers
67 views
Buck Converter Capacitor and Inductor Characteristics
I'm trying to make a buck converter with this mickey-mouse MC34063A chip that will step-down +5V to +3V3 up to 500 milliamps. I've gone through the calculations by hand and validated them with an ...
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0answers
43 views
How does LTSpice model reverse recovery time?
Hello everyone,
I am working on the prediction of the reverse recovery losses in a Buck converter. I have the following schematic:
You can see below a zoom on the turning-off time of the diode:
I ...
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0answers
37 views
Load impedance simulation of buck converter
I would like to design a buck converter that will feed a printed circuit board that contains an inductive load like a DC motor and a relay, and some capacitive circuits like RLC filter. I have started ...
0
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3answers
58 views
Why capacitor value should be greater than gate capacitance of gate of NMOS in Bootstrap topology?
In case of buck converter when NMOS is used as high side driver then bootstrap circuit is used to keep gate voltages higher. While designing that bootstrap circuit, the value of capacitor is ...
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2answers
49 views
How to charge an android device with a buck converter
I've got a male micro USB connector like this one
I'm feeding the output of a buck converter set at 5V to pin 1 positive and pin 5 negative. Remaining pins are not connected. When I plug the ...
2
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2answers
83 views
In a buck boost inverting converter is there any difference exchanging the position of the diode from the positive to the negative rail?
In a buck boost inverting converter is there any difference exchanging the position of the diode from the positive to the negative rail keeping the same current rotational direction ?
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23 views
What modifications can I do in my simulation so Vg must not exceed 20V?
I have implemented gate driver of Buck Converter. But when input voltage exceeds 20V then Vg also exceeds 20V wich is threshold value of transistor. What modifications should I do so that my gate ...
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1answer
46 views
Low profile buck converter [closed]
This is a follow up to my previous question regarding USB-C power delivery as a power source. There's been a fair about of development since when that question was asked and since STM have released a ...
1
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1answer
36 views
In Buck Converter, when the ESR and EPR of Inductor increases then what is the its effect on output voltages and why?
I have done LTSpice simulation. I have seen that by increasing ESR of inductor, the output voltages decreases and by increasing EPR of inductor the output voltages and ripple in output current and ...
0
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1answer
30 views
Buck converter output power definition
I'm designing a buck converter to feed the following loads:
A control circuit 3.3V/100mA
A 80V solenoid which has a DC resistance of 300 ohms. This means a current of ~270 mA.
My plan is to ...
4
votes
1answer
114 views
Slope compensation in current mode control
There is something a little bit confusing to me between papers dealing with the theory of external slope compensation in current mode control of SMPS and application notes dealing with implementation (...
1
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1answer
50 views
Add isolation to a switching power supply
Actually I'm using a simply switching buck regulator that perform a 24v to 12v convention. I'd like to add isolation between power source and regulator. I've checked already all-in-one isolating DC-DC ...
3
votes
3answers
412 views
What will happen if you supply a higher voltage to a buck converter? [duplicate]
The title says enough, but let’s give a real life example too. Take one of those LM2596 35V boards. What will happen to it if it gets 50V on the input?
Most likely it will burn, but will this voltage ...
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0answers
25 views
Current mode buck modeling
I am following this document Loop response consideration in PCM. Here I am implementing fig 5 schematic in page 9. From equation 1 to 22 got me some of the hidden values of the schematic which I have ...
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0answers
60 views
Optimizations for LM2596, Positive and Negative Voltage
I'm working with the LM2596 to get a positive and negative voltage using two separate IC for each. I'm having trouble optimizing them for a 1 A load. I followed along with TI's WEBBENCH designer to ...
0
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1answer
39 views
DC current at input and ouput capacitance of buck
I'm working on this website
http://www.onmyphd.com/?p=voltage.regulators.buck.step.down.converter
Could someone help me to understand those two statements:
1) "since the DC current of the inductor ...
0
votes
1answer
56 views
Rectifier to Step Down Buck Regulator
I'm trying to simulate an AC to DC voltage regulator. I'm trying to go from 115 Vrms to 5 V DC at 1 amp max, though 0.5 amps nominally. I initially thought of using the LM317 at first, but after ...
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6answers
5k views
How to reduce MOSFET heating in Buck Converter
I have designed this Buck Converter which convert 60VDC to 12VDC at 10A.
Switching Freq 100KHz.
Facing MOSFET too much heating issue.
MOSFET ON time and OFF time is decided by a UC3845B based circuit. ...
13
votes
3answers
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 ...
0
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0answers
26 views
PCM CCM Converter using SIMetrix/SIMPLIS
I have built the attached file which is a peak current mode buck converter on SIMetrix/SIMPLIS software but I cannot simulate due to some errors that I could not troubleshoot. Please can anyone ...
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1answer
30 views
SIMtrix/Simplis Simulator
I'd like to use SIMtrix/Simplis Simulator for simulation of SMPS design, and I'm about to start building a peak current mode buck converter like the one shown below from richtek.com:
but ...
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0answers
30 views
Noise and interference from a buck converter
I have heard that buck converters cause noise/radio interference. Since I am using it next to a Xbee S2C module, will it interfere with my Zigbee signal?
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0answers
34 views
Input DCDC buck filter design equation
I am asking because I am confused. I cannot resolve this issue since yesterday and I am still learning.
I was reading article about Input DC-DC buck filter. Each of the two articles say something ...
0
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1answer
48 views
In my dc to dc buck converter(0 to 17V - 12v), when i connect a load ,converter output voltage decreases to 1V [closed]
I try a buck converter of variable input(0 to 17) to 12V. when i connect a load with very small resistance , voltage decreases.if load increases , converter voltage looks constant.
what happens if i ...
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2answers
69 views
Buck converter or regulator [duplicate]
I have a battery supply consisting of 3 AA batteries of each 1.5V.
I need an operating voltage of 3.3V.
Which choice of buck converter or regulator would be better?
My application requires 100mA of ...
