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Questions tagged [switch-mode-power-supply]

A switch-mode power supply (SMPS) switches been fully-on and fully-off states quickly to maintain voltage regulation. They offer lower power dissipation and run cooler than linear regulators that continually dissipate power through a transistor.

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1answer
22 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 ...
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1k views

Why do some switching regulator require tantalum or electrolytic capacitors instead of ceramic?

I'm looking at this switching regulator: http://www.ti.com/lit/ds/symlink/lm2675.pdf. For its input and output capacitors it recommends tantalum or electrolytic capacitors. It mentions in section 9.2....
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42 views

With a SMPS charging a capacitor bank. What is the power rating of the SMPS?

I'm working on a project to build a 24VDC to 250VDC switch mode power supply for the purpose of charging a capacitor bank. The capacitor bank will be rated at 250V and 180mF. So, the prime power ...
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38 views

Low Dropout Regulator Enable Delay

I have a main buck DCDC 5V that feeds to five different LDOs(3.3V). To create power sequencing, I would like to use a resistor and a capacitor at the input of the enable pin of each LDOs and by ...
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0answers
24 views

Designing transformer for uc3842 offline flyback power supply

I need help on how to calculate turns in flyback transformer for the above mentioned power supply. Now I know about designing Half bridge, full bridge and forward converters but I am unable to figure ...
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1answer
56 views

Techniques for Filtering a Noisy Buck Converter

I have built a buck converter on the TS30011. Unfortunately, I am getting terrible noise on the output. External Parts Used: Inductor Output Capacitors I have been analyzing my design and have ...
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27 views

What's the LC filter arrangement on dual output DC/DC converters?

It's pretty hard to find a filter arrangement for a dual output converter, but I came across the following:- Taken from here. So for the bottom example, is the LC arrangement correct? I always ...
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1answer
47 views

SMPS feedback circuit with voltage regulation and current limiting

i’m self learning electronics for a few months now and i choose my first project to be a bench SMPS. Since it is my first circuit design ever i really need some clarification. My SMPS is 2-switch ...
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102 views

Help identifying component in SMPS

I have been working on a Schroff/Cherokee Europe PE1947/23B SMPS (circa 2004?) and have had trouble identifying a component within the circuit. This SMPS features the following outputs: +12v DC @ 8A ...
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20 views

Gate Current Calculation and Practical Mosfet Selection

Vnoo3 is the drive voltage, and Ig is the gate current. What I am wondering is: 1) How to calculate the peak Ig on the rising edge of the pulsed gate voltage? For instance, using the spice image ...
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2answers
41 views

SMPS controller duty cycle resolution

when reading the datasheet for some SMPS controllers like the lm25116, I can see that they operates around 1MHz, but nowhere we can find their duty cycle resolution: 8bits, 12bits, 16bits ? So I'm ...
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3answers
106 views

Energy in transformer air gap

Here is the following assertion : Question: Why is it commonly stated that in a flyback transformer, the "air gap carries most of the stored magnetic energy"? Answer: We can intuitively ...
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19 views

meanwell psu inrush current and temperature sensor

I want to use a Meanwell PCB mounted power supply on my next project. https://www.meanwell.com/Upload/PDF/IRM-20/IRM-20-SPEC.PDF The spec sheet says that it has an inrush current of 20A/115VAC (I'm ...
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1answer
57 views

Gate driver using switches UC3842 PWM Controller

I have prepared a crude model of boost controller using PSpice simulator of UC3842 IC Gate driver has Ron and Roff as 1 and 100meg respectively (S3 and S5) and Vout will go to external mosfet or a ...
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58 views

Can a single phase SMPS be converted to run from three phase?

If you have a switch-mode power supply that runs off 240 VAC single phase, is it possible to convert it so that it runs off 3P+N (415V phase-to-phase) by only changing the bridge rectifier? I have ...
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57 views

How to prevent voltage droop when discharging a battery?

This is quite an open question, so apologies in advance if you would rather schematics and the like, if you really think this would help I can provide them My problem: boosting from 2x AA Li ...
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1answer
91 views

3.3 Volts Output on 1.8 Volt Regultor

On my circuit board, I have three different voltage regulators. I have a 5V Buck converter that goes into a 3.3V LDO and then finally 1.8V LDO. When I power the board with a USB and do not use ...
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2answers
49 views

Switch mode power supply inrush current protection

I want to design a suitable PCB for my audio amplifier project. The amplifier boards (both left and right channels) will use almost 4 amps at 24 V at full power. I want to use a switch mode based ...
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31 views

TEA1733T switching in small bursts and with very brief on time for [external] FET

I should start, possibly, by saying I am no expert on offline SMPS, but am having a go. I have built up the schematic below: I am getting no proper voltage out of the outputs. The transformer ...
18
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2answers
3k views

Why did they use ultrafast diodes in a 50 or 60 Hz bridge?

This is again from an HP power supply (PSU). The incoming 230 V is rectified into 340 VDC and is fed to a switched-mode supply. The odd thing here is that the manual for that unit, HP6023A, ...
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1answer
78 views

How to extract the switching noise component for this signal data?

A servo accelerometer when powered by batteries has a clean output, but when used with this SMPS supply its output seems like have switching artifacts from the power supply(the datasheet says its ...
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1answer
56 views

Abnormal microcontroller circuit behavior when I connect SMPS

I designed a device that calculates current and power using a CT and an ATMega328P-AU microcontroller. The board I designed was simple and I didn't account for noise cancellation on the ADC lines and ...
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1answer
35 views

Controlling multiple floating power supplies from a single point

I have assembled a power supply from five HP dps-750rb common slot power supplies. All five units are in series. I have the first grounded electrically and have the other four units modified and ...
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1answer
47 views

Filter before or after switching regulator?

I will be passing a power line (12V-60Vdc depending on the circumstance) with a lot of noise, 300Hz and above, riding on it through a buck regulator. I want to remove this noise with a filter. I don't ...
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37 views

bode plot of LM3481 as boost converter

I have simulated an open loop boost converter using LM3481 average model, given by texas instruments and I got a very strange bode plot (More precisely, strage phase response), please can you tell me ...
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2answers
2k views

How does this circuit start up?

I'm trying to understand how CI HT7A6322 starts up. Relevant part of the datasheet says: Control circuit power supply. Also provides a charging current during start up due to a high voltage ...
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21 views

Conduction Mode in PFC

At a Power-Factor-Correction (PFC) circuit, Why mostly using Continues Conduction Mode (CCM) for high power applications, ex. above 300 kW, and using Boundary Conduction Mode (BCM) or Discontinuous ...
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2answers
86 views

How is the impedance of a circuit calculated when non linearity is introduced from a switch

What is the impedance of the following circuit if the switch operates at the same frequency with the input voltage. Since the switch introduces non-linearity to the circuit, how can I calculate the ...
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37 views

Pi Filter Calculation

Here is my circuit schematic below. PT4115 feeds LEDs. Load current is 200-215mA and switching frequency is 500kHZ. How do i calculate pi filter or what is the best values for pi filter in this design ...
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1answer
34 views

AC Simulation in Power supply simulators

I would like to design a boost converter using LM3481 from texas instruments. To de the job, I have selected TINA TI circuit simulator, where the average model of LM3481 is given. So I have used this ...
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1answer
81 views

Are input filters always required for switching power supplies?

This is a follow up to the questions here and here I recently designed a PCB that contained a buck regulator (LM2576 5V). You can see the PCB layout in this question. After converting the input 12VDC ...
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1answer
112 views

Mechanical Switch Causes Transients from AC-DC Power Supply

I'm having trouble getting rid of output transients from this Mean Well PSU right after the AC input is switched. https://www.meanwell.com/Upload/PDF/RPS-500/RPS-500-SPEC.PDF The PSU is a RPS-500 ...
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62 views

Why does rectifier output is showing DC instead of pulsating DC

I am using below circuit for PFC. Before connecting coupled inductor's auxiliary output to the IC's Vcc, I wanted to make sure that it is coming properly or not. So when I probed the red dot in the ...
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1answer
102 views

Why parallel diodes on the output of a switch-mode?

I am looking at buck-boost converters on the Texas Instruments design tool, and multiple of these topologies have parallel diodes on the output. I cannot see any reason to do this. Can anyone explain ...
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1answer
39 views

Ramp compensation for UC1843 and UCC38C44

When we pick up the datasheets of UC1843B-SP and UCC38C44, we notice that they have the same functional block diagram, specially the PWM generator circuit (Error amplifier, current sensing PIN and the ...
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2answers
52 views

How to calullate RMS current through switch (MOSFET) in boost converter?

Trying to calculate values for a boost converter based on document Basic Calculation of a Boost Converter's Power Stage. Want to know power dissipation though MOSFET which that document does not ...
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1answer
747 views

Generating negative voltage rail using P7805 DC-DC converter

I need to create a negative voltage rail (from positive supply rail), say -5V to keep a P-MOS transistor in ON-state even when the voltage on its [S] source is 0V. So I found this schematic in an ...
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1answer
56 views

Power supply design, Pi filter

I am designing a power supply circuit. Does anyone have any calculation formulas for resistor which we connect across inductor or capacitor? I have attached a circuit with highlighting a connections ...
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1answer
41 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 ...
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0answers
49 views

Can a Capacitance Multiplier be used with high voltage outputs?

I am designing an SMPS which two output voltages of 5kV and 2.5kV. My transformer is split into four equal sections, each feeding a FB multiplier, connected in series to form the final voltages. ...
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1answer
16 views

LinkSwitch-XT2 (LNK3696) with opto feedback

What's a proper circuit if I want to use a LinkSwitch-XT2 device (from Power Integrations) with an opto coupler in the feedback loop? This is the typical application circuit of LinkSwitch-XT2 devices....
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1answer
43 views

micro water pump set up

I need to create a water pump system for a modeled water tank. Now I'm a complete noob so my ignorant self thought I could just buy a small DC pump, a switch and some connectors and off I'd go. Doing ...
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1answer
47 views

switch-mode power supply

First post here. I'm making a DC/DC converter which will generate an output of 19.5V 18A. Its a synchronous buck converter with the LM5145 TI chip. When I have light load on the converter the output ...
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1answer
62 views

Y cap between AC ground and DC ground in SMPS [duplicate]

I have seen in many SMPS there is a Y cap placed between AC ground and DC ground. What is the need of this Y cap?
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2answers
78 views

Eliminating oscillation in a feedback circuit

I have built a switch-mode power supply where the output voltage is controlled by a PWM signal from a microprocessor. The power supply is based on an XL4015. The feedback pin is normally fed by a ...
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0answers
40 views

Current mode boost converter design

I was trying to design a current mode boost converter in CCM using a MCP1630 and the specifications of the design are as follow: ...
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5answers
154 views

How can I describe and explain SMPS on a very basic level without diving down in heavy maths / EE lingo?

I'm writing a book about repairing electronics. The audience level for the book is "very little knowledge about electronics" and it's mostly about the mindset and mindtools for finding problem sources ...
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60 views

PFC boost converter is not stepping up the voltage

I am making a PFC circuit for AC-DC converter. I am facing a weird issue. As per my design the output of the circuit should be 390VDC, but I am getting 311VDCrms with ringing (overshoot 360V, ...
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1answer
50 views

Does supply voltage affects stepper motor driver heat dissipation?

Below is a block diagram of a stepper motor controller with an external mosfet h-bridge that drives one of the stepper's coils. Let's say that the coil has 2ohm DC resistance and 3mh inductance, the ...
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2answers
1k views

Why do oscilloscopes use SMPSes instead of linear power supplies?

I'm wondering why digital oscilloscopes are using switching power supplies instead of linear power supplies. The SMPS has a higher efficiency, but it can produce some noise during high frequency ...