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Hi jawale23,
Could you tell me detailed parameter of the transformer, such as primary inductance, core size, turns wire and switching frequency?
For flyback design guide, Please refer to: Fairchild application note AN4137
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No matter in CCM or DCM or CRM , operating period “T” is always equal to 1. Therefore, in figure 6-22(c), The diode average current only with “D1” “ILmax” is concerned, or only with the area of a triangle is concerned,The textbook is correct
Idave=ILmax×D1/2
Do you understand ?
Hi,Jegues,
for your information:
In CCM, the operating period T is equal to “D(Ton)+D1(Toff)” or 1.
In DCM, ”D(Ton)+D1(Toff)” is less than T or 1.
In Figure 6.22 (C) from page 245, we can figure out the average current of diode,
IDave=（ILmax×D1）/（2×T）
Where T is 1.
In figure 6.22(a),for...
I think "Is=ILD and ID=ILD1" is correct.
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You can also use the simulation software to verify your calculation. For example, Pspise
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modify: Pspice
Hi Jegues,
When the Buck or Boost Converter operating in DCM, the operating period T is not equal to D+D1, and the operating period T is not equal to 1, so I think that the calculation of the average current of the Boost Converter operating in DCM in your textbook may appear some mistakes. may...
Hi FvM,
First of all,thank you for your reading and helping
My colleague designed a SMPS, its input voltage rang is 90VAC to 265Vac, output voltage is 54vDC, and load current is 1.6A. The circuit of the SMPS is composed by two stages, a front-end PFC implementing the L6563S and a LLC...
This is not a complete PFC circuit.
it should be a PFC circuit with a zero ripple current technique
for details about zero ripple technique please look at the article "a zero ripple technique applicable to any dc converter"
Hi,
From the waveform of the MOSFET, I find the reset time is too short.
So I also think the problem is not for the snubber ，and it's a transformer reset problem.
in my opinion adding a snubber can not improve the spike voltage. I suggest you increase the primary inductance 。
If the...
Hi mtwieg,
First of all, thank you for your supports!
I have solved this problem in the afternoon. The compensation network parameters are as follows:
R38=220K, C27=100nF, C26=1nF,C38=33nF,R32=1K,C24=10nF and R31=100Ω。
I do not have enough time to do the small-signal analysis, because the...
there are two control loop in the flyback. one is output voltage feedback control loop and another is output over-voltage protection control loop.
I have confirmed that when the oscillations occurs,only one optocoupler control the feedback loop.
The oscillations frequency is about 1KHz and the...
Hi ZekeR,
About schematic please see this attachments.
The switching frequency of this SMPS is about 50KHZ. The transformer primary inductance is 10uH.
thank you for your help!!
Hello!
I am designing a 75W flyack SMPS, which input voltage is 18v~36vdc, output voltage is 110vdc, and output full load current is 0.65A.
The transformer primary turns are 4Ts and the secondary turns are 40Ts.
The pwm IC is UC3842B and the feedback IC is TL431.
The output ripple...
If let me design a 15V/4A SMPS, I’ll consider to use quasi resonant PWM controller-NCP1207A/B.
Because the QR mode Fly-back converter has low EMI noise.
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