All Questions
38 questions
2
votes
2
answers
214
views
Calculating junction-to-ambient temperature rise for switching MOSFET
So I'm looking at datasheet's since I'm looking for a N-Channel MOSFET for a DC-DC Buck Converter that will be switching at 1.2MHz. Since the MOSFET will be used as a switch for the Buck Converter, I ...
- 275
3
votes
2
answers
1k
views
Best way to drive multiple LED strips at distinct times with one LED driver
Application:
6 LED strips: each strip has LEDs connected in series
Driver is TPS92691 (CC LED driver)
The source is a battery
The LED strips will be flashed in a carefully controlled cycle, starting ...
- 417
0
votes
1
answer
42
views
Analysis for the peaks in FFT
Suppose I have 2 cases:
1st MOSFET switches with rise times and fall times of around 10ns (Vds).
2nd MOSFET switches with rise times and fall times of around 50ns (Vds).
Both of them have a switching ...
- 295
1
vote
2
answers
148
views
DCM vs CCM Noise Spectrum
Will the noise spectrum (at the LISN) due to switching of a Synchronous Buck DC-DC converter be different (peaks) if the converter is operating in DCM (Inductor current) compared to CCM keeping the ...
- 295
0
votes
0
answers
67
views
Pspice simulation not working
I am simulating the evaluation board LM5145EVM-HD-20A on Pspice.
(https://www.ti.com/tool/LM5145EVM-HD-20A)
LM5145 already has the Pspice model for the same but the switches used are not Pspice models ...
- 295
0
votes
0
answers
39
views
Switching Freq. and Output voltage error
Attached is the datasheet for the Synchronous Buck Controller: https://www.ti.com/lit/ds/snvsb32b/snvsb32b.pdf?ts=1711536038118&ref_url=https%253A%252F%252Fwww.ti.com%252Ftool%252FLM5145EVM-HD-20A
...
- 295
0
votes
1
answer
67
views
Double Pulse Schematic
I had a doubt in the schematic of the gate driver part of the following double pulse test circuit.
Do I need to connect the source pin of Q2 to VDDB? What will be the path of the current during ON and ...
- 295
0
votes
1
answer
76
views
Simulation time for Full bridge
This is a full bridge circuit which I am trying to simulate in Ltspice with a snubber. When I use ideal switches instead of MOSFETS, the simulation works fine. But when I use the real mosfet models, ...
- 295
0
votes
0
answers
195
views
Why do we need a small external gate to source capacitor for a MOSFET drive circuit?
I have a question regarding a MOSFET half bridge driver circuit. We always connect a small capcitor between the gate and source of both the high side and the low side switch, typically in picofarads. ...
- 357
0
votes
1
answer
161
views
PCB trace width and high current with MOSFETs
Having designed the PCB for my double pulse test circuit I'm facing problems with the trace widths. Operating current is 30A and I checked on the trace width calculation sites and they are coming up ...
- 295
4
votes
1
answer
122
views
What is meant by Switching charge ( under Gate charge characteristics) in the given MOSFET datasheet?
What is switching charge in this MOSFET datasheet?
The switching actually takes place during Miller region. Hence I belive Qgd should be called as switching charge. But looks like the remianing gate ...
- 3,156
0
votes
0
answers
94
views
How to decide the number of layers? [duplicate]
I am new to PCB design and I want to understand how exactly we should select the number of layers. I just know more layers helps us with making the routing easy but I don't understand what is power ...
- 295
3
votes
2
answers
542
views
Which is the more important switching parameter in MOSFET datasheet? Turn on/off/delay times or Input/Output/Reverse capacitances?
I see both capacitance and timing details mentioned in the MOSFET datasheets.(Ref:)
Which one should be considered for comparing the MOSFET switching performance between 2 MOSFET part numbers?
Note: ...
- 3,156
0
votes
2
answers
190
views
Why do my MOSFET keep blowing up saying the gate-drain voltage exceeds its rating?
I'm working on a switched mode power supply that outputs 9 V in a simulation using a NE555 timer connected to the gate of my MOSFET and switching at 96 kHz frequency. Other components works just fine ...
- 1
5
votes
3
answers
941
views
Does turn-on and turn-off delay cause MOSFET switching loss?
I know during rise time and fall time, there are MOSFET switching losses.
Is same the case with turn on and turn off delay?
I don't see any relevant pics in internet with the IDS waveform included. ...
- 3,156
0
votes
1
answer
80
views
Quad-Channel Smart High-Side Switch Schematic Review
I am using TPS4H000BQPWPRQ1 in my design. Below is my design. Can you please review my design especially current sense (PIN No 8) and current limit (PIN No 9) design?
In the datasheet page no 27 you ...
- 3,061
1
vote
2
answers
158
views
MOSFET SOA: Why is the max current limit lower for DC case? [duplicate]
Shown above is the academic definition of MOSFET SOA. Rdson limit is not considered as a real limit in most academic texts - that's ok- understandable.
But why is the max drain current limit different ...
- 3,156
2
votes
1
answer
159
views
Multiple Source Terminals of SiC MOSFET
I want to know that most of the semiconductor top side cooled package have more than one power source terminal. I can understand by doing so you can minimze the loop inductance of gate driver loop ...
- 357
1
vote
1
answer
880
views
Influence of gate resistors and capacitors on driving gate of mosfet
Good Day,
I wannted to ask in a typical gate driving circut of a Mosfet, we always have Rgoff, Rgon,RGS and CGS as shown in below screenschot. What is the purpose of these components in driving the ...
- 357
1
vote
1
answer
269
views
Switching losses in a power supply
Switching losses calculation in resistive load and inductive load are different. For a full-bridge DC-DC topology with a resistive load at the output, should I calculate my switching losses like I ...
- 319
0
votes
2
answers
408
views
Power loss in gate driver independent of duty cycle?
Inside a generic switch mode power supply a MOSFET is used. The switching frequency is \$f_{sw} = 300\text{kHz}\$ and the duty cycle is \$D=0.45\$.
To drive the gate of a MOSFET, we use a gate driver ...
- 4,569
7
votes
4
answers
1k
views
Why is increasing gate voltage beyond 'reasonable' limits not advantageous in power MOSFETs?
In a power MOSFETs datasheet I see Rds(on) specified at Vgs= +10V whereas +Vgs (absolute max) is +30V. Why do they (manufacturers) restrict to +10V while quoting Rds(on)? The manufacturer could have ...
- 3,156
2
votes
2
answers
218
views
MOSFET selection for buck regulator (SOA vs thermal dissipation)
I am trying to design a buck regulator with the following specification: Vin = 24V Vout = 5V I max = 8A Fsw=228k. The load is basically a long strip of RGB LED's. Which in certain cases would be all ...
- 757
5
votes
2
answers
1k
views
What is the purpose of this sense pin in dual MOSFET package? [duplicate]
No info available in datasheet
http://www.aosmd.com/res/data_sheets/AONP36336.pdf
After going through the answers I got some additional doubts:
Why is the sense pin only there for high side MOSFET?
...
- 3,156
0
votes
0
answers
377
views
Failure Modes for Synchronous Boost Low-Side MOSFET?
I'm looking for some input on possible failure-modes for the low-side MOSFET in a synchronous BOOST converter. I am using LM5122: https://www.ti.com/lit/ds/symlink/lm5122.pdf
Out of 50 units built, 2 ...
- 1
0
votes
2
answers
681
views
Does the body diode of the high side n-channel FET in a buck converter turn on during switch node voltage spike time?
A typical synchronous buck:
The normal switch node spike that people typically see when the high side FET turns on:
In the past i have been fairly negligible on this part. When the switch node spike ...
- 109
1
vote
2
answers
336
views
MOSFET Selection criteria considering conduction losses, switching losses and working frequency
I am trying to choose a suitable MOSFET for my full-bridge resonant converter for wireless power transfer. The circuit topology is something like the following. Specifications: rated power \$-~500 W\$...
- 868
1
vote
1
answer
45
views
What's the purpose of components in these mosfet driver
I see these double ended transformer drivers on many places, I know the working principles of these gate drive transformers but still don't have an idea about external components that I've marked with ...
- 319
4
votes
1
answer
6k
views
Current spikes when MOSFET turns on and voltage spikes when MOSFET turns off
I studying for my Power Electronics course and have come across something which I can't seem to wrap my head around.
In a lab, we built a buck converter with an inductive load and measured various ...
- 43
0
votes
0
answers
549
views
Is the switching speed of MOSFET comparable to that of a Schottky diode?
Assuming identical voltage and current rating, which is having higher switching speed? MOSFET or Schottky diode?
In synchronous buck converter, we replace Schottky diode with MOSFET (low side) for ...
- 3,156
0
votes
0
answers
92
views
Questions regarding Gallium Nitride semiconductor devices in Switched Mode Power Supplies
I have a couple of questions regarding the use of Gallium Nitride MOSFET devices in a DC/DC converter design of mine. My topology is an LCC full bridge converter.
My knowledge is not at expert level ...
- 489
0
votes
1
answer
139
views
Buck converter design issue
I want to design buck converter for 385VDC to 48VDC for that I calculated the values of component and simulated it with proteus but I am not getting the desired output. What is wrong? PWM has a 20v ...
- 73
1
vote
2
answers
305
views
Fixing conmutation for high voltage switching with power MOSFET
I have an issue with a charge circuit for a capacitor as load.
I want to switch approximately 400 V DC to charge a 1000 µF 600 V capacitor. I'm using a power MOSFET for this application. I need it to ...
- 41
1
vote
1
answer
2k
views
Controlling a spark plug using 555 IC
I built a circuit for ignition system using MOSFET, 555, ignition coil (specs unknown, but current rating is more than 2 A and less than 10 A), SMPS (12 V, 10 A for powering the the whole circuit.)
...
- 79
0
votes
2
answers
1k
views
Switch between 2 power sources
I have one power source (bicycle dynamo) A.C 5-6V which will be rectified to D.C, and the other source D.C from a solar panel 12V. It will be 2 input source and one output.
what type of power switch ...
2
votes
2
answers
397
views
pulse width modulation versus amplification
If I want to make a sine-wave inverter where the output AC voltage is lower than the input DC input voltage, how can I see that using pulse-width modulation will be more efficient that just using a ...
0
votes
1
answer
742
views
Inductance overheating
I have a circuit designed to run a electro piezotransformer at resonance frequency of around 80kHz. As a controller was used microcontroller Attiny 25, which by measuring feedback current generates ...
- 11
2
votes
1
answer
812
views
How much power IRFP460 can proccess?
I decided to use IRFP460 in a two-switch forward converter. This Mosfet can dissipate 280 watts. Can I get 1000 Watt from my converter?
As a general rule how much power a Mosfet can transfer with ...
- 47