All Questions
Tagged with switch-mode-power-supply capacitor
108 questions
3
votes
1
answer
127
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Higher capacitance for EMI return cap in isolated DC-DC-SMPS?
A typical SMPS converter usually includes a small capacitor of ~1 nF in tight proximity to the isolation transformer to return the common-mode switch noise to the primary side switch for EMC reasons.
...
- 38.5k
2
votes
1
answer
167
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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 ...
CommunityBot
- 1
3
votes
3
answers
292
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Using only ceramic capacitors on an input of an SMPS - unclear advice from manufacturer
I was reading through the datasheet of a boost converter, TPS61023 from TI.
In the "Input Capacitor Selection section", they give the following advice:
Notably, TI advises against using ...
0
votes
0
answers
70
views
Capacitance Formula derivation
Can anyone help me with how this formula came in the first place (marked in red)? I am not able to understand the denominator term.
This is with reference to Double Pulse Test taken from the book : ...
- 295
0
votes
3
answers
95
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Charge "something" over a 10 second interval then dump the charge on a load. (Alternative to battery?)
I'm getting a limited current of about 10 mA from a 12 V DC source. I would like to charge "something" (anything but a battery) with this energy over 10 seconds, and then dump it to a 12V ...
- 81.7k
0
votes
0
answers
195
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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. ...
- 73.6k
0
votes
1
answer
116
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Why solid state capacitors?
I've been looking through multiple cellphone chargers and I have noticed that they all use solid state capacitor for the output capacitor of the switching power supply (flyback converter).
Is there ...
- 172k
0
votes
0
answers
46
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5 V to 3.3 V buck with limited input current and large capacitor to cover current spikes?
We need to design a power supply for a 3.3 V WiFi-device. But there are quite some current spikes during WiFi startup. Using the design below there is a risk the 5 V (250 mA max) supply (not mine) ...
- 16.8k
7
votes
4
answers
1k
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Derating of C0G DC block capacitors with applied DC voltage
I was having a discussion with a colleague at work regarding derating of MLCC capacitors when used as a DC block capacitor. My colleague mentioned that it is standard practice to derate MLCCs with the ...
- 1
2
votes
3
answers
322
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Output stage filter of a buck regulator and ESR
I am trying to design a two LC stage output filter on a buck converter. And as the needed peak to peak ripple has to be pretty low ~ 1 mV, the overshoot and undershoot need also to be pretty low, I ...
- 473k
0
votes
1
answer
2k
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Bulk Capacitor for Full Wave Rectification
By using notes from C.Basso Bulk Capacitor Calculation, I managed to plot the ripple curve for bulk capacitors for offline converters.
This bulk capacitor location:
Assume that my system is AC/DC ...
- 23.5k
2
votes
2
answers
504
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How can you calculate Peak Pulse Power for a Non-Rectangular Power Pulse
I was reading this Vishay document on how Peak Pulse Power can affect resistors.
There is a flow which is attached in the document describing the process of calculating the Peak Pulse Power for a Non-...
- 45.6k
3
votes
2
answers
615
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What is the role of an MKP capacitor in the input of this SMPS? What happens if I remove it?
I'm trying to repair this SMPS board. It converts 220VAC into 15VDC. The circuit is based on KA5L0380R power switch.
The input 1A subminiature fuse of the circuit is blown. To find other broken ...
- 45.6k
17
votes
7
answers
9k
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Why are charge pumps only used for low current applications?
Typically the most expensive (and hard to get) elements in a SMPS are the inductors. Thus I was wondering if it's possible to use inductor-less switching mode power supplies (i.e. charge pumps) for ...
7
votes
1
answer
11k
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Why do we need 100nF cap in the output of an SMPS?
I was looking at Micrel AN-53 and I have noticed that in a circuit in the first page (circuit is below), at the output of an 400KHz, 27V, 7A, 180W boost converter, there are two 680 uF, two 10 uF and ...
- 2,980
1
vote
1
answer
303
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Capacitor ESR Calculation
I'm trying to perform esr calculations of this capacitor(1uF):
https://alconelectronics.com/wp-content/uploads/2020/06/KP-6-JUNE-2019.pdf
to do that I need to know dissipation factor and at the bottom ...
CommunityBot
- 1
5
votes
2
answers
743
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What is the purpose of the capacitor in this SMPS circuit?
Can anyone tell me the purpose of the 2n2 100V capacitor and its function in the circuit?
Image source: danyk.cz - 12V 5A switched power supply
- 73.6k
1
vote
1
answer
81
views
Duty Cycle and Filtering in Switching Power Supplies
I have a few confusions to clear up. The first one is about the switching power supply.
Does the power supply simply work on the bases of the duty cycle? Like If I have a pulsating signal of 50% duty ...
- 14.8k
0
votes
1
answer
106
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When finding ESR/ESL of a ceramic capacitor, what frequency should I assume during a load step?
I want to determine the output droop in a transient load step for a buck converter I am designing.
The output capacitor will supply current during this load step, and there will be a drop associated ...
- 11.2k
3
votes
2
answers
628
views
Half bridge SMPS with polypropylene film capacitor
I dismantled a cheap Chinese 240VAC to 48v-20A SMPS to try to understand the basic working principle.
There is a CBB22 335J630V polypropylene film capacitor in it. I have drawn it in red on this basic ...
- 38.5k
0
votes
1
answer
165
views
Non-isolated DC/DC converter
I am integrating a non-isolated DC/DC converter from Mornsun in one of our designs.
We are trying to stick to the typical application schematic:
However, two questions dictated by the limited space ...
- 103
1
vote
3
answers
197
views
Different type of capacitors
How can I distinguish between filter capacitors, decoupling capacitors, and bypass capacitors? What is the most basic and important difference in their functionality?
- 355
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1
answer
42
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Purpose of non-polar C1 - R1 in series
what is the purpose or function of series non-polar C1 - R1 (24 Ohm resistor) on parallel to rectifying D around SMPS output here ?
Help clarify by elaborated explanation, thanks
- 172k
1
vote
1
answer
439
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What is the purpose of adding series resistor to tantalum capacitors?
For a power rail, we have used tantalum polymer caps whose ESR is as low as 50 mohm.
I see that a few of these capacitors have a 1 ohm resistor added in series, a significant value.
What could be the ...
- 25.6k
1
vote
2
answers
104
views
What is the frequency at the input of the bulk capacitor in a flyback?
I am under the impression that the output frequency of the bulk capacitor will be the same as the switching frequency of the PWM chip. The input however I am a bit confused about, because if it is ...
- 88.8k
2
votes
1
answer
2k
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What is the function of the feedforward capacitor on the LM2596-ADJ?
I'm looking at the LM2596S datasheet and notice that on page 7 (figure 3) it recommends a "feedforward" capacitor for the adjustable variant.
The example schematic on page 9 shows a ...
- 24.7k
0
votes
1
answer
371
views
A ceramic capacitor on my PC SMPS has blown; need to identify it [closed]
I have a Cooler Master 600 W SMPS Model no. RS-600-pcar-E3. Recently I tried to switch on my motherboard and I heard something burst and saw sparks before it stopped working.
After opening it I got a ...
- 9,310
4
votes
2
answers
1k
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What capacitors are proper to use for input of AC DC converter?
I am trying to build an 120 AC to 15 DC @ 200 mA converter using a Power Integrations LNK3206P. Using the full bridge rectifier setup on Table 10 from application note AN-70, Cin1 and Cin2 should each ...
0
votes
1
answer
42
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Choosing output capacitor for Power converting Switching regulator (Cout_Eff)
I am using R1276S001A-E2-FE to convert my 24 V supply to 3.3 V to power my microcontroller.
In order to do the conversion properly I need to choose the output capacitor. I see there are three ways to ...
- 8,173
0
votes
1
answer
1k
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Why is an inductor rather than a capacitor used to smooth switch mode regulators
I understand (at least at a high level) how to use both capacitors and inductors to reduce noise but I don't understand the advantages/disadvantages of each approach or why one is chosen over the ...
- 73.6k
0
votes
1
answer
243
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Can I replace the ceramic capacitor with tantalum?
In the following topology, a 2200nF multilayer ceramic capacitor (SR305E225MAR) is used in the compensation network. Can I replace it with a tantalum capacitor with equivalent voltage and capacitance? ...
- 2,275
1
vote
1
answer
271
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SMPS bulk capacitor number
I am designing a SMPS and calculated the input capacitor to be around 47µF. The voltage rating needs to be >1000V.
What would be the difference (advantages/disadvantages) between using 2x500V in ...
- 174k
2
votes
3
answers
601
views
X2 polypropylene capacitor for DC smoothing after AC rectification
Can a X2 polypropylene film capacitor be used for dc smoothing at the output of a bridge rectifier? I want to use this capacitor at the input of a power factor correction circuit with a switching ...
- 34.2k
0
votes
0
answers
98
views
What is a Ladder Switched Capacitor?
I have recently read several papers with LSC on it (I'm taking care of my Mom 24/7, so I can't find them right now). Are Dickson and Cockroft-Walton considered Ladder, or am I off? Thanks.
- 2,980
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0
answers
94
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Must a 12V to 110V switched-capacitor inverter output be isolated? if so, does anything special have to be done?
I have an LTSpice simulation of a small switched-capacitor boost converter producing about 12W x 110V of DC, and I was wondering, does it have to be isolated (and need anything special to attain ...
- 2,980
4
votes
3
answers
673
views
Ceramic capacitors shorting on power up
I have a power supply unit that is used to drive a couple of relays. Rarely but sometimes the input capacitors (C218, C200, C201 and C207) to the switch (U202) short when the power is turned on (230V.)...
- 152k
1
vote
1
answer
514
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For calculating inrush current in a ceramic capacitor , do we need to consider the effective capacitance after derating for dc-bias effect?
Inrush current happens when capacitor is initially charged from 0V to the intended rail voltage.
What should be the effective capacitance to be considered during this charging? -Since the voltage ...
- 174k
0
votes
1
answer
107
views
Feedback loop design (buck converter): Output capacitance- effective value or nominal value to be considered?
In this TI datasheet of TPS62180, it was mentioned that the LC filter combination should be selected from a set of predefined values. I understand this is usually the case for an internally ...
- 148k
1
vote
1
answer
80
views
Why is the input capacitor calculation different in TI datasheet?
Below is the input capacitor calculation from TI datasheet
Why is it different from standard buck calculation given below?
Another TI dcoument
- 473k
0
votes
1
answer
211
views
Prevent spark/surge when connecting power cable (charging input bulk capacitor)
In cheap off-line AC-DC SMPS you will probably notice a huge spark when you connecting the PSU to mains. That usually won't cause problem because your mains is far more capable to handle that surge.
...
- 24k
1
vote
2
answers
171
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Charge pump circuit- What is the need for caps near CLK pin?
Below is a charge pump circuit in NB680 IC Datasheet
I was trying to understand the charge pump functionality by comparing it with the standard circuitry shown below:
https://www.edn.com/capacitive-...
- 47.1k
1
vote
1
answer
2k
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Capacitor blows up in TV power supply circuit
I have an LED TV Samsung T22B350EW (Type No.: LT22B350) which can not power on. I'm trying to fix it, to learn more about such type of circuits. A capacitor in its power supply board is blown up.
The ...
- 148k
6
votes
3
answers
381
views
Headphone Noise from Laptop SMPS
I have been facing an issue that has been a mystery to me for quite some time, and I wanted to see if someone here can potentially give me more insights on this so I can understand why it is happening....
- 1
1
vote
3
answers
777
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Following is an excerpt from a power electronics textbook. Is the statement true?
As far as I know ESR primarily depends on the type of dielectric.
eg: Al electrolytic (higher capacitance value) would have much higher ESR than ceramic (usually lower capacitance value).
Say for ...
- 148k
-2
votes
1
answer
75
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How will this circuit work [closed]
This circuit is after the rectification process how will this work
- 180k
0
votes
0
answers
148
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how this equation is obtained for calculating input capacitor of a fly back presented in UC3842 datasheet?
i know that it refers to stored energy formula for a capacitor according to voltage variations. but i dont have any idea about the specified part. where did this part come from?
https://www.ti.com/lit/...
- 755
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0
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96
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What type of SMPS is this?
What specific type of SMPS is this? I'm working on troubleshooting no power out.
I'm having trouble finding comparable circuits so I can learn how it works. It appears to be some sort of resonant ...
- 16.8k
3
votes
2
answers
599
views
SMPS Layout, capacitors in parallel placement
I'm laying out a buck converter based on the TPS54308, and the datasheet recommends the following, which I'm trying to replicate:
Webench (the interactive design tool by TI), however, recommends 2 ...
- 81.7k
3
votes
3
answers
925
views
Capacitors in series, equivalent capacitance to reduce voltage rating
For example, I need 100uF 60V capacitor for filtering in power supply. The DC source is about 40V, but I have 400uF 20V capacitors.
If I arrange four of them in series I got in total 100 uF and each ...
- 73.6k
0
votes
0
answers
167
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Can a MOV properly discharge a X-Capacitor?
I created an AC-DC SMPS with a EMI filter that consists of a X-Capacitor and Common-Mode Choke. IEC 62368-1 requires that capacitors be discharged below ES1 (60V) within 2s of being disconnected. As ...
