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48 Threads found on Crossover Frequency
Hi, From the little I know, op amps with feedback can become unstable and oscillate due to poles and zeroes, something or other about unity gain at the crossover frequency. A zero introduces a phase shift of +90? and boosts the gain by some amount in dB, a pole introduces a phase shift of -90? and decreases gain by some amount in dB, you add pole
crossover frequency is just the frequency at which the total loop gain is 0dB. I don't think "bandwidth" has a specific meaning with regards to smps. Could possibly refer to the -3dB point of the converter's transfer function, or the -3dB point of the closed loop transfer function.
Hello, The LTspice simulation of a 28vin to 1V5 out, 20A out, Dual Buck converter (each buck switches at 200khz and is in CCM, current mode) shows a crossover frequency of 14000 Hertz and phase margin of 63 degrees. The excel calculation of this circuit (also attached), gives it as 9600Hz for crossover, and 53 degrees for phase margin. (...)
Hello, Why do the following application notes, both by fairchildsemi, contradict each other about the nearness of the SMPS crossover frequency to the corner frequency of the output LC filter (?post filter?) The text just above fig22, page 12 of the following document by Choi , suggests that TL431/opto feedback can be undertaken with (...)
if you do use an LC post filter make sure that its resonant frequency is at least 10 times higher than the smps crossover frequency, as per page 3 of AN57 AN57: ...Bottom right of page three
Hi, Going to use Cadence SpectreRF to check DCDC buck converter AC characteristic (gain margin, phase margin, crossover frequency). Any reference? or Tutorial to use SpectreRF for DCDC? I think I have to use PAC (periodic AC) analysis in spectreRF analysis setting but I have no idea how to create DCDC testbench and also set analysis parame
With a differential probe you measure the difference voltage between two points. You canīt measure the difference between "cycles". What circuits would you want to measure the difference voltage? But if you use a differential probe and connect the two wires to the two output stages. Then you will see the same voltage on your
The very old and very slow LM324 is the first problem. It also produces crossover distortion that you will see and hear on the sinewave and triangle wave. The second problem is probably the RC filter that smoothes the PWM but also cuts high frequencies. The third problem: You made a high frequency boost circuit that has infinite gain (and noise) at
The datasheet for the lousy old LM324 shows that when its gain is 200 times then its frequency response drops above only 2kHz so sounds will be more muffled than an old telephone or an AM radio. Also it is very noisy and has crossover distortion. For amplifying DC then the maximum input offset voltage of 7mV will cause an output of plus or minus 1
Hello, Would the crossover frequency of a Buck, witch-mode LED driver be lower in frequency if the load was changed from LEDs to a dummy load resistor of resistance (VLEDs/ILEDs)?
surely the resonance should be kept well away from the crossover frequency? Ray ridley, in his book "power supply design: volume 1 control" (page 47) states that the LC resonant frequency should be less than half of the crossover frequency. This doesn't tally with what are saying. Only one of them can be (...)
In the third page (top left) of the following document, it says that the crossover frequency of Voltage Mode SMPS's must always be above the power stage LC resonant frequency.......... (its actually called page "24", even though its only the third page) ...Isn't this missing somethi
Hello, Does this 5W SEPIC LED driver have a poor phase margin.? The LED current oscillates at ~500Hz (loop crossover frequency) during start-up, as it rises upwards, -however, there is absolutely no LED current overshoot, and the LED current never oscillates when it gets near its regulation value of 50mA. The LED driver spec is: Vin = 12V V
Hello, The below voltage mode flyback has an output LC filter pole at 618Hz. The feedback loop crossover frequency is 1150Hz (this can be seen in the simulation by the frequency of the ringing on the "COMP" pin) So, the feedback loop crossover frequency is less than double the LC filter pole (...)
An LM358 dual or an LM324 quad are old but they have low power consumption. Then they have trouble above only 2kHz, are noisy and produce crossover distortion.
Hello What is the relationship between SMPS input filter frequency and F(sw) and also, crossover frequency? is it that the crossover freq must be at least half as much as as the filter resonant frequency? (the input filter resonant frequency as "seen" from the SMPS input)
I'm skipping the point if a guitar amplifier needs PFC to comply with EN61000-3-2, there have been sufficient previous discussions about it. If I remember right, you took part in it. You missed however to explain the question title. A PFC needs in fact a voltage control crossover frequency considerably below 100 Hz, the Onsemi datasheet is e.g.
Dear all, How to determine crossover frequency of peak-current mode buck converter if my target switching frequency is 1.5MHz?
Dear all, How to determine crossover frequency of peak-current mode buck converter if my target switching frequency is 1.5MHz?
If you examine the output impedance of complementary CMOS and 50 Ohm line drivers you will find a similarity in structure but the crossover distortion is reduced by having a current surge during crossover which tends to make dynamic power consumption increase with transition frequency. THis used exclusively for driving square waves or (...)