All Questions
70 questions
30
votes
4
answers
22k
views
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(...
- 7,749
6
votes
3
answers
669
views
Why would you sense peak inductor current at the high-side PMOS transistor rather than at the NMOS?
I found this image for peak current mode sensing here.
Is there any reason that you sense the peak inductor current from the MP instead of theMN transistor? I know that ideally both should work but I ...
- 270
6
votes
3
answers
2k
views
Switch mode power supply vs DC-DC converter
I have started learning about DC-DC converters and switch mode power supplies (SMPS.) I know that the standard SMPS (attached fig. below) has an input rectifier, DC link capacitor, inverter, output ...
- 87
6
votes
2
answers
1k
views
How does a buck converter's output ripple waveform become sinusoidal?
Below image is from Fundamentals of Power Electronics.
The ripple component of the inductor current will be flowing through the capacitor as shown in the ic(t) graph. This one I understood.
May I ...
- 3,061
6
votes
1
answer
3k
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 (...
- 1,078
5
votes
2
answers
659
views
What are the advantages and disadvantages of feeding DC into an SMPS?
Can I feed DC into an SMPS to get a regulated output? If yes, why? and What are the advantages and disadvantages?
For example, I would like to input 200VDC to an SMPS with an input range of 100-230VAC....
- 172
5
votes
4
answers
2k
views
Why do buck converters end up in steady state?
I'm studying buck converters such as the one in the following simulation:
I have learned that for buck converters that are in continuous conduction mode and at steady state, the following equation ...
- 543
4
votes
4
answers
8k
views
How to make a step down DC-DC converter fail safe?
I'm planning to power some high power colored LEDs with a buck converter, using a microcontroller to control the switching to maintain a constant current. I'm also considering a simpler, switched ...
- 597
4
votes
1
answer
3k
views
Design buck converter to meet output ripple voltage specs
I am stuck at calculating output ripple voltage with non-ideal components for buck converter. As you can see from the picture, the output ripple voltage caused by each individual component is ...
- 1,661
4
votes
1
answer
373
views
High current ripple through inductor
I am trying to figure out a way to create a high current ripple through and inductor, similar to that of the ripple the inductor sees in a SMPS. I would like to put a 2A peak to peak 400KHz current ...
- 402
3
votes
2
answers
902
views
Frequency Response of Ideal and Real Type III Compensator
I'm trying to develop a Buck Converter with a Voltage-Mode Control, using a Type III Compensator, just like the one below.
So I calculated its transfer function, and then with the correct values of ...
3
votes
2
answers
311
views
Sampling gain effect in buck converter
I recently learned that there is a phenomena called sampling gain effect in dc-dc converter and I am struggling to understand what this phenomena really is. Could someone enlighten me?
And I have seen ...
- 341
3
votes
2
answers
2k
views
Bidirectional DC-DC converter, 12V - 300V, 1 kW?
What DC-DC converter topology would you recommend for a device that supports bidirectional power flow of up to 1kW with 300VDC on the high-side and 10-15VDC on the low-side? I want to use it to ...
- 31
2
votes
5
answers
625
views
Ripple current in synchronous buck converter
I am designing a synchronous buck converter and I am at the bread board stage in my design. I wanted to check the current waveform through the inductor, but I do not have a current probe available. I ...
- 402
2
votes
3
answers
194
views
High voltage buck converter inductor voltage rating
We‘re designing a buck converter that should convert 600VDC down to 20V. For that purpose we use the ST VIPer26k.
We’re currently looking for an inductor (L2). The inductance is 1mH, but we‘re not ...
- 378
2
votes
1
answer
2k
views
Input filter to reduce conducted emissions caused by DC/DC converter
This material from ROHM explains the input filter design for a DC/DC converter.
The filter circuit is given below.
I understood the design of Lf, Cf2, Cd and Rd.
If you see the 3rd page (design of ...
- 3,061
2
votes
4
answers
10k
views
Battery Charger using a buck converter
I'm designing a Lead Acid battery charger with 3 stages. For the 2nd stage (constant voltage stage) as it is written in literature: the voltage applied on the battery must be dependent on temperature. ...
- 63
2
votes
3
answers
2k
views
What would cause a buck-boost regulator to buzz loudly and generate high voltage ripple during certain input voltages?
I've got a buck-boost power supply design based on the LM5118 by TI. A schematic of the device is shown below:
(Link to TI Workbench)
EDIT Many of the comments mention the layout, hence I've ...
- 1,318
2
votes
2
answers
2k
views
switching noise from ltc3780
I have currently built a buck-boost converter using LTC3780 on a breadboard following this deisgn.
The circuit is calculated and designed to accommodate the input voltage given in the schematic. I ...
- 21
2
votes
3
answers
1k
views
Core loss appearing in buck converter ripple current
I have been told (and have also seen experimentally) that an inductor with a high core loss will introduce "glitches" to the ripple current in a switch mode power supply. I have tried researching this,...
- 402
2
votes
1
answer
288
views
Buck converter current
I have this synchronous buck converter.
Input voltage - 8.7V
Output voltage - 5V
Switching frequency - 350kHz to 450kHz
Output load current is 2A
Schematic:
I have an input capacitor of 68uF and an ...
user220456
2
votes
0
answers
78
views
Phase shift at half the switching frequency of a dc-dc converter
I would like to know if, regardless of the control loop used (Voltage mode control, average current mode control, peak/valley current mode control), there is always a 90-degree phase drop at FSW/2 due ...
- 341
2
votes
1
answer
167
views
Output Capacitor Design for a Multiphase Buck Converter
According to this application note from Texas Instruments, in the design of the output filter for a multiphase buck converter there are basically two ways of choosing the output capacitor. The first ...
1
vote
2
answers
1k
views
DC-DC buck converter low input voltage behavior
I am using this DC-DC buck converter.
Schematics :
Buck Converter Specifications :
Input Voltage - 18V to 32V
Switching Frequency - 300kHz
Output Voltage 9V
Load Current - 0mA to 200mA Maximum.
I ...
user220456
1
vote
1
answer
292
views
Average Modelling of Buck Converter
I am doing Modelling of Buck Converter for LT3890 (Datasheet link attached) for Frequency response analysis .
I have some reference model of Buck converter ,please refer below image
Datasheet Link: ...
- 119
1
vote
1
answer
755
views
Bad Waveform on Output of Buck Converter
I have designed a buck converter (poorly) and have been getting terrible noise. I made a post here where I was given suggestions on how to do a proper layout for my buck converter. This post also ...
- 381
1
vote
1
answer
159
views
DC-DC current mode control frequency behavior
On a buck converter in average current control mode, for example, the inner current loop sees and manages the double pole created by the LC filter, and thanks to this the outer voltage loop is blind ...
- 341
1
vote
1
answer
84
views
Current Sensing Design
while using MCP1630 in switch mode power supply design, in the datasheet they gave the input bias current of the "current sense pin"
what are the considerations the designer should take while ...
- 1,078
1
vote
1
answer
593
views
DC/DC step-down regulator destruction because of inductive load?
I was evaluating PAM2316 DC/DC step-down converter and destroyed several of them, I suppose the cause could be an inductive load.
See my schematic and my layout here:
Let me explain: The circuit was ...
- 292
1
vote
1
answer
144
views
Buck converter: PWM modulator input waveform
I have a question about the pwm modulator in a classical buck converter in voltage mode control (VMC). For the circuit in question, I copied over the picture provided in the answer of another SE ...
- 1,083
1
vote
1
answer
1k
views
Buck Regulator Output is too Small
I'm making a buck regulator using L4970A using circuit from this application note figure 60 , except for the inductor. I change i to 180 uH
I wanna make it to be a power adaptor for laptop with solar ...
- 103
1
vote
0
answers
46
views
Are the prinicples the same for designing a high side vs low side buck?
I am an analog engineer that is getting into SMPS design.
This is a high side buck:
This is a low side buck:
simulate this circuit – Schematic created using CircuitLab
Assuming that I take ...
- 88.8k
1
vote
0
answers
2k
views
Design of a Buck Converter with LC Input Filter
I am attempting to design a circuit from an exercise:
I am stuck at point (c). I attempted to calculate the voltage and current ripple in the LC filter using the small-ripple approximation, but this ...
- 119
1
vote
0
answers
66
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 ...
- 305
1
vote
1
answer
146
views
LTC1775 Buck converter component question
I am trying to design a 12v,10A buck converter using a with LTC1775 and have gone through the calculations assuming a 40% inductor ripple current and a switching frequency of 150kHz. This gave an ...
- 15
1
vote
2
answers
227
views
What SMPS topology is this?
I came across this SMPS topology that I don't recognize. It looks sort of like a combination of a buck converter and a boost converter, but I can't quite figure it out. I haven't been able to find ...
- 51
0
votes
1
answer
6k
views
Build DC/DC (Buck) Converter using 555 timer
I saw a design for a 12V DC to 5V DC buck converter using a 555 timer on http://www.simple-electronics.com/2011/10/12v-to-5v-converter-555ic-mosfet.html. Is this a good design to use towards my smps? ...
- 69
0
votes
2
answers
185
views
I would like to drop a variable DC voltage from input 30Vdc to 200Vdc to output 5Vdc with a max 200mA
I am new to electronics and would like some help if possible.
The incoming voltage will be variable from 30Vdc to 200Vdc coming from a bank of solar panels. The output is 5vdc at a max of 200mA. I ...
- 11
0
votes
3
answers
3k
views
Spikes in Inductor Current : Buck Converter
What could be the reason of such spikes in inductor current at each Switch ON-OFF. ??
This spikes are also getting affected in load current.
Please help me to reduce / remove this spikes.
( ...
- 13
0
votes
2
answers
174
views
12V in, 1V @ 12 Amp Out, Buck, Why 100 Amp MOSFETS and 60A Inductor?
I was showing someone the TI Workbench and it came up with this schematic.
94% Efficiency, switching Freq. 100khz
With voltage of 12v and 1v, max Amps of 12, why would it select 25v and 30v 100 Amp ...
- 7,517
0
votes
3
answers
2k
views
The role of reference voltage in buck converters?
I asked a question here which made it quite clear that it's probably not a good start to make something that I plug directly into the mains.
Instead, I've decided to build a low-voltage buck ...
- 737
0
votes
1
answer
321
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 ...
- 1,078
0
votes
1
answer
777
views
Does current flow through the potentiometers of buck and boost converters?
I'm working on a project where I'm replacing the trimpots on a buck converter and a boost converter with proper potentiometers. The new potentiometers will be wired to the converters instead of ...
- 803
0
votes
1
answer
189
views
How can I achieve a 25V - 5V @10A buck circuit, and a 25V - 8V @6.5A buck circuit? [closed]
I'm a computer engineer major in my senior year.
My team and I are making a SmartKart, and I'm responsible for power management and power designing.
Right now, based on several components we will be ...
- 1
0
votes
3
answers
915
views
Role of the output capacitor in buck converter in terms of frequency
I am using this DC-DC buck converter - buck converter.
Schematics :
Buck Converter Specifications :
Input Voltage - 18V to 32V
Switching Frequency - 300kHz
Output Voltage 9V
Load Current - 0mA to ...
user220456
0
votes
2
answers
1k
views
DC/DC Converter Output Power Rating
Looking at chips such as
AP6502A
TPS5430
The output capability is rated in peak and continuous current. Why are they not rated in terms of power? What output voltage is this current rating for?
...
- 1,008
0
votes
2
answers
379
views
MP2359 dies after reset
I'm using MP2359 for converting 12V from 20V.
Datasheet: http://www.monolithicpower.com/desktopmodules/documentmanage/api/document/getdocument?id=269
I'm using the recommended sch and layout designs ...
- 1,043
0
votes
2
answers
683
views
Create a time-variable DC power source
For some reason, I need a time-variable DC power source that changes its value according to time. I need this change of value to be controllable.
I'll put it this way:
Say I have a 12 V DC power ...
0
votes
1
answer
125
views
Buck Converter Peak Current Mode Control Average Model
I am trying to understand average model of Buck Converter for Peak Current Mode Control Topology.
Below snapshot taken from Christophe Basso Webpage(https://powersimtof.com/Spice.htm) from file "...
- 119
0
votes
1
answer
118
views
Circuit to convert 14.8v battery with max 4a discharge current into 12v, 9v and 5v output?
I am making a robot with multiple devices mounted on top. I am planning to buy either a 14.8v or 11.1v Li-ion battery which has internal BMS limiting maximum discharge current to 4A. Now I need 9v for ...
- 45