# Questions tagged [power-factor-correction]

A circuit that compensates the reactive characteristics of a load to make behave as close as possible to a resistive load in order to maximize the power consumption efficiency.

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### Is this PFC choke design correct?

I would really appreciate it if you could check this inductor design, if there are any mistakes, or if it can be improved. I'm designing a $50\,\mathrm{\mu H}$ PFC choke for a totem-pole bridgeless ...
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1 vote
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### Relationship between inrush current, blowing the fuse and switching power supplies with PFC

I'm having the problem that my (switching) power supply of my new "mobile workstation" (laptop) is blowing the 230V/16A (about 40 years old) fuse (circuit breaker) most of the time when ...
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### Ideal 3 Phase Rectifier [closed]

I am working on a 3 phase PFC and implementing third harmonic injection. In order to do so, I use the min-max method. This would be trivial in an MCU, but everything is being done in analog. I have ...
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### Impact of Low Power Factor on Loss Generation in PMSMs

I am focusing on the losses generation in PMSMs and still have some doubts about the role of a low power factor. For the analysis, I consider a three-phase PMSM controlled with Field Oriented Control (...
58 views

### How to reduce notches in input AC voltage for Totempole Power factor Correction circuit?

Respected readers, I am working with a totem pole PFC circuit. In an experimental study, I face a problem of high-frequency notches in source voltage (Yellow one). I found an explanation behind this. ...
1 vote
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### Capacitance for power factor correction formula

I wrote a test the other day and the paper provided a formula for calculating the required capacitance needed for power factor correction. The formula: \begin{align} C = \frac{Q_c}{\omega V_{RMS}^2} \...
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### Pulse width modulation using ML4800CP

I am working on a SMPS (450 V output). It use an ML4800CP IC to control and manage 450 V DC. How can I measure the PWM signal using an oscilloscope? I attached it, and it worked well for the PFC ...
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### In a PFC boost converter, would input current distortion happen during initial voltage build up- when input is higher than output?

It is said that "Boost DC voltage output must be higher than the maximum line peak voltage otherwise you will introduce distortion (harmonics)" Shown below is the simulation output for a PFC ...
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### How to calculate boost PFC iL, Vout by duty?

When steady state ∆iL - ∆iL‘ = 0 and Vout Vin/(1-D) ∆iL=(Vin/L)･Ton ∆iL‘=((Vin-Vout)/L)･Toff Vout=Vin/(1-D) Can I calculate current changes(∆iL - ∆iL‘) during dynamic state by using the same equations?...
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### For an active power factor correction circuit (PFC boost,) is there any characterisation graph between input voltage and power factor?

Just like the regulation graph (ouput voltage vs. input voltage) for a voltage regulator, is there a similar graph (power factor vs. input voltage) for a power factor corrector circuit? My aim is to ...
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### Would an AC EMI filter capacitors contribute to inrush current?

Shown below is an EMI filter for an AC input. My doubt is when I analyse the inrush current, should I be considering the contribution due to all three capacitors? a) Differential mode capacitors b) ...
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1 vote
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### Pulsed current measurement and power factor calculation

I want to measure pulsed current in a 3-phase power meter application. I understand that the waveform will be random, as the current in question is the overall current consumed by different types of ...
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### Why is the current angle negative?

I don't understand why the current angle is negative.
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### PFC circuit: Rectified AC voltage going beyond input AC voltage limits

We have a PFC circuit powered from a bridge rectifier as shown below: Fig 1: We have separate sense terminals to detect the AC voltage levels and accordingly enable the PFC converter (sample circuit ...
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### Current sense resistor determination

Please help me understand this PRC circuit of a SMPS. According to the NCP1606 PFC controller datasheet pin 4 is responsible for current sensing. Now, there are two resistors: (red) in series to the ...
1 vote
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### Forward biasing of diode bridge in a discontinuous mode operation of a three phase buck-boost derived power factor corrected converter

In this paper, they said that during mode 1 the diode bridge is forward biased because the output capacitor voltage is greater than peak line to line voltage but during mode 2 they are forward biased. ...
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### How do I model domestic power demand and identify consumers by their resistive and reactive draw?

I put a commercially available 80 A current transformer on the live tail to my domestic fuse box. I obtain readings of current draw, supply voltage and power draw. When an appliance is turned on I am ...
187 views

### Boost Inductor Design for three phase Diode Bridge Rectifier for PFC operation

I am doing a simple DCM based control for power factor correction. Please see the topology below . Specifications are as below: 1.) Power 5KW 2.) Input Voltage is 415V L-L Nominal 3.) Inductor ...
223 views

### PFC Boost with LT1242

I have tried a PFC Boost simulation with lt1242. The specification is Input Voltage Range = 90 to 264 Vac, Output Voltage = 400 Vdc. I have got the result but I am not sure does this make sense at all ...
215 views

### PFC Boost Converter

I have two questions regarding PFC boost Converter. Why boost converter is preferred over buck for PFC? What is the difference between PFC boost converter and a traditional Boost converter?
1 vote
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### Power factor EMC filter analysis

As an embedded system engineer, I must admit that my knowledge in electronics is not particularly strong. Therefore, I am seeking assistance to clarify the purpose of certain elements in the provided ...
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### How to find the cutoff frequency of my EMC filter

I am seeking assistance in understanding the calculation process for EMC filter capacitors and inductance. I comprehend that this filter operates with a cutoff frequency, and based on this cutoff ...
1 vote
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### Boost PFC ICs not turning on

I've built a boost PFC circuit on a PCB using the LT1249 controller, using the reference design guide provided by Analog Devices here: https://www.analog.com/media/en/technical-documentation/data-...
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### How does power factor affect the efficiency of a 12v pure sine wave inverter?

I am trying to calculate how long I can run a given load (a sound system and laptop charger) from a 55 Ah 12 V battery using a pure sine wave inverter (specifically, this one). Though, at the end of ...
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### Why does the power factor of my fluorescent ballast seem to be impossible?

I have a ballast that's rated to run two 32 watt bulbs, which means (I think) that the working power is 64 watts. The line rating of the ballast is 0.5A at 120V, which means the apparent power (the ...
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### Identify a SMD diode used in a PFC circuit

I am trying to identify a SMD diode that is used in a PFC circuit on a SMPS power supply board from a Hisense 50" smart TV. The diode is connected on a IDP2301 (multi-mode PFC and LLC controller) ...
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### NCP1654 current Mirror

Regarding the NCP1654, there is a circuit in the IC block diagram that I don't fully understand. Could you please take a look at the figure below and help me understand the blue and red lines? below ...
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### Totem pole PFC control

I found a figure that discusses how to control S3 and S4 of the totem pole PFC. Please refer to the image below. However, I couldn't find any information regarding the control method used in this ...
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### My AC-DC PFC rectifier self-boosts voltage when with no load

I have made a PFC IC LT1249 reference design - a few differences are 820 uH inductor, 1.1 mF capacitor and different MOSFET. When I connect AC (50 V) with no control (17 V) voltage the DC output rises ...
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### CRM PFC frequency drop

When designing CRM PFC, I encountered an issue with the switching frequency. In theory, the frequency waveform appears as expected. However, during simulation using a tool, I observed a drop in ...
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### Why does PFC often use OTA to do the compensation?

I see some design documents about PFC, they often use OTA to compensate for the circuit. I know the OPA is voltage control voltage and OTA is voltage control current, but I don't know why I can't use ...
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### Boost PFC compensator saturation issue

I try to use a simulation tool to model the PFC circuit. There is a weird thing I can't very understand. Please see the below figure from my simulation. As you can see the output is 400V, after the ...
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### Boost PFC compensator design

I'm trying to design a type II compensator for my LT1249 boost PFC stage but I'm not sure on how to place the zero and poles frequencies using a typical error amplifier: I have a working LTspice ...
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### LT1249 boost PFC controller CAout pin

Looking at the reference design for the LT1249 PFC controller below: What is the purpose of the CAout pin? Are there any equations on how to setup the resistor and capacitor network?
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### Power factor in AC circuits

A lagging power factor means that it has an inductive load, right? The final circuit will still be lagging meaning that it will still be inductive? How is the power factor getting used here? I can get ...
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### Bridgeless totem-pole PFC controllers [closed]

I'm considering bridgeless totem-pole PFC for a design and am looking for the quickest integrated solution. Unfortunately, it seems like a lot of implementations currently use MCUs and DSPs for ...
1 vote
258 views

### Selecting PFC topology

I'm considering different PFC topologies for the AC-DC stage of a device around 1 kW with aim of optimizing for efficiency and secondarily component size. This far I have identified following options: ...
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### Buck PFC controller

I'm considering a buck PFC for the design of my SMPS. The input will take 50 VAC rectify it using a full bridge rectifier. The buck PFC stage will then step down the voltage to a 15 V/20 A output. I'm ...
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### Do modern variable frequency drives perform power factor correction?

Do modern variable frequency drives (VFDs) perform power factor correction? I can't find info to see whether VFDs do power factor correction. If they do, how good are they?
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### Does a transformer have different primary and secondary PFs?

I tried connecting two energy meters on primary and secondary and found that they were showing different values when a load was connected to the transformer. Does a transformer have two different PFs, ...
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### Power Quality Measurement & Reporting Standards

I'm analyzing power quality in low and medium voltage facilities (50/60Hz; 0.48 - 69 kV; factories, campuses, etc.) while trying to apply existing standards wherever possible. In addition to demand ...
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### PFC (Power Factor Correction) harmonics

I recently succeeded in creating a powerful buck PFC with a value almost equal to 1 (0.999) As you know there are always problems when dealing with real life circuits. I mean, the PFC value is real, ...
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### Half-bridge converter input capacitor setup from boost PFC

I am using a uUC3854 for my boost PFC stage with an output power of 750 W. From my calculations of the output capacitor with a hold-up time of 25 ms and a maximum output voltage of 400 V and a minimum ...
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### Inrush current on current sense resistors

The problem is on a circuit which implements PFC circuitry. There are two parallel 0.36R current sense resistors located in the inrush current path. These resistors measure the PFC current through the ...
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### How to choose PFC controller and how to boost voltage

I have found this PFC controller (I am building a rectifier to ~500V). As I understand, because PFC uses a boost converter, it should be able to boost rectified voltage to bigger voltage. How would I ...
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### Why the effect of a triphasic capacitor could be as twice as its rated kVar? *(check Update 1)*

Why the effect of a triphasic capacitor could be as twice as its rated kVar? Please check Update 1, since if its true, then I think my issues are solved. Intro This is a real life case of a client of ...
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### Why does the variac make a "zing" sound during testing?

I've tested my prototype transition mode 80 W boost PFC with 220 VAC input and 400 VDC output. When I supply the Vcc of the controller and start the switching MOSFET, after a couple of minutes, the ...
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### What is the correct arrangement of the EMI filter?

I want to design an EMI filter for the input side of a PFC converter. there are various topologies for EMI filters. in some cases, the CM filter is located on the network side and the DM filter on the ...
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### What is an intuitive explanation of using a boost converter for power factor correction?

By theory, a bridge diode and a capacitor bank can convert an AC sine wave into a DC signal, but the source current would appear spikey, having a power factor much smaller than unity. In order to ...
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