it's circuit of power supply circuit for smartphone charging application. kindly help me understand working of this circuit. I have attached circuit diagram along with bom for your reference . thanks
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help me understand working of this circuit
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It appears to be a Flyback Converter with an auxiliary winding to power the chips on the primary side. The main difference between a forward converter and a flyback converter is the phase dots on the primary and secondary windings are opposite to each other. The schematic has two devices labeled U2. The U2 on the primary side should be labeled U1 since it is presumably the SP6648. The actual U2 is on the secondary side and is a PC817B opto-isolator.
ETA: Here is rudimentary description of a Flyback Converter:
https://en.wikipedia.org/wiki/Flyback_converter
What more would you like to know?
ETA: Here is rudimentary description of a Flyback Converter:
https://en.wikipedia.org/wiki/Flyback_converter
What more would you like to know?
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what's the use of U1, U2, U3, U4 & U5??? explain each one in detail
what's the use of d2 in series with r3 and what's the use of d2 in series with r3
what's the use of ec1, ec2, l1, l2 & r8 in primary side???? why not only simple r & c filter at primary side???
what's the useof primary winding, auxillary winding and secondary winding of this transformer used in the circuit?
phase dots on the primary and secondary windings are opposite to each other means? what's the advantage in that?
explain all the points in detail
thanks
There isn't a U1.
U2 (left) is a flyback controller
U2 (right) is an optoisolator
U3 is an adjustable shunt regulator
U4 is a control IC which determines the charge rate according to the resistances on the USB lines
U5 is a rectifier.
Mr. Google will help you find out how a flyback converter works. When you have understood that, please feel free to ask about anything you still don't understand.
U2 (left) is a flyback controller
U2 (right) is an optoisolator
U3 is an adjustable shunt regulator
U4 is a control IC which determines the charge rate according to the resistances on the USB lines
U5 is a rectifier.
Mr. Google will help you find out how a flyback converter works. When you have understood that, please feel free to ask about anything you still don't understand.
U1 (labeled U2 on the primary side of the schematic) is an 8-pin IC SP6648F. I cannot find a datasheet for a 8-pin part with that designation so I guess you're out of luck there. There is a surface mount 10-pin part but who knows if it has the same function.
U2 appears to be a PC817B optocoupler. It is used to sample the output voltage of the converter and feed that information back to the controller on the primary side. That would be pin 4 of the SP6648 labeled U2 (actually U1) on the primary side, signal node FB (FeedBack).
U3 is a TL431 Shunt Voltage Regulator, which is used in conjunction with the opto-isolator U2 to feed back a sample of the output voltage to the primary side controller.
U4 is a type of USB protocol controller that communicates with a USB master to inform it of its requirements and/or capabilities. Here is a link to a datasheet. https://datasheet.lcsc.com/szlcsc/FP6601Q_C86198.pdf
U5 is an SP6536 Synchronous Rectifier. I cannot find a datasheet for this part so I can't help you with that.
Whoever labeled both diodes D2 would have been fired if he was working for me. This kind of laziness is inexcusable.
D2 & R3 on the primary winding are used to prevent the primary from developing a net DC voltage. Transformers are AC devices.
D2 & R9 rectify the AC on the auxiliary winding to power U1 (labeled U2 on the schematic on pin 3).
For EC1, EC2, L1, L2, and R8 it is a more capable filter than an RC filter. Depending on the phasing of L1 & L2 it could be either a common mode filter or a differential mode filter. If I had to guess, I would choose common-mode for no real particular reason.
You should already know the purpose of the windings of a transformer. The opposite phase dots on the primary and secondary are explained in the article on Flyback converters.
U2 appears to be a PC817B optocoupler. It is used to sample the output voltage of the converter and feed that information back to the controller on the primary side. That would be pin 4 of the SP6648 labeled U2 (actually U1) on the primary side, signal node FB (FeedBack).
U3 is a TL431 Shunt Voltage Regulator, which is used in conjunction with the opto-isolator U2 to feed back a sample of the output voltage to the primary side controller.
U4 is a type of USB protocol controller that communicates with a USB master to inform it of its requirements and/or capabilities. Here is a link to a datasheet. https://datasheet.lcsc.com/szlcsc/FP6601Q_C86198.pdf
U5 is an SP6536 Synchronous Rectifier. I cannot find a datasheet for this part so I can't help you with that.
Whoever labeled both diodes D2 would have been fired if he was working for me. This kind of laziness is inexcusable.
D2 & R3 on the primary winding are used to prevent the primary from developing a net DC voltage. Transformers are AC devices.
D2 & R9 rectify the AC on the auxiliary winding to power U1 (labeled U2 on the schematic on pin 3).
For EC1, EC2, L1, L2, and R8 it is a more capable filter than an RC filter. Depending on the phasing of L1 & L2 it could be either a common mode filter or a differential mode filter. If I had to guess, I would choose common-mode for no real particular reason.
You should already know the purpose of the windings of a transformer. The opposite phase dots on the primary and secondary are explained in the article on Flyback converters.
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This is very presumptive of you - I don't think anyone as the time to go into that much detail. If you are serious about product design (and why anyone would want to try an compete in this market space beats me) you have to do the leg work. There are thousands of design guide and application notes from the big manufacturers on designing SMPS, just google them. Collect the datasheets for all the active devices and read them - compare their circuit suggestions with those from other suppliers. Here's a link to the datasheet for the main controller.
I was willing to spend a little time, but being retired I can afford it. I guess I quit looking when "SP6648F" returned no useful results. Interesting datasheet and the reference design looks pretty close to the schematic in post #1.
what's the use of y capacitor at the output side?
It's an interference suppression component which returns current capacitively induced in the transformer windings.
What is a y capacitor on the output side?
CY1
He means CY1, which looks as though it is connected to earth (as Class Y capacitors often are) but it is connected between output and the negative supply on the primary side.
It is to bypass high frequencies to the chassis ground.
ETA: the values is 102 = 1000 pf. At line frequency the impedance is 2.65 MΩ, but at a typical switching frequency of say 100kHz the impedance drops to 1.59KΩ
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what's the use of r3 + d2 at primary winding side and r9 +d2 at auxillary winding side?
R3, D2 and C1 (don't forget C1, it's important) clamp the voltage spike that occurs when the MOSFET switches off due to the leakage inductance of the transformer. R4 and R5 then slowly dissipate the accumulated charge.
R9 and D2 rectify the output from the auxiliary winding to produce a low-voltage supply to run the IC, just like @Papabravo said.
R9 and D2 rectify the output from the auxiliary winding to produce a low-voltage supply to run the IC, just like @Papabravo said.
At primary side, why r1 & r2 are in series and why r3 & r4 is in parallel? also, at pin 3 of pwm ic, what's the use of ec3? also, capacitors like c1, c2, c3,c4, c5 ,c6 etc etc used in any electronics circuit is mainly for what particular purpose????
Also, output from primary winding and auxilary winding is AC???? and purpose of d2 is to convert ac to dc, like that????
two resistors in series is for what purpose? two resistors in parallel is for what purpose, resistor and capacitor in series is for what purpose and resistors and capacitors in parallel is for what purpose ???? for any electronics circuit I am asking, thanks
R1 and R2 are likely to be surface mount resistors with a maximum voltage rating of 200V.
R3 and R4 could be replaced by a single resistor with double the power rating.
EC3 = smoothing capacitor for auxiliary supply.
Yes, exactly, it is a half wave rectifier.
