ON Semiconductor NCP1351B Application Note Download Page 25 | Manualshive

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AND8344/D

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25

Figure 53. Photo of the Demoboard, Bottom Side

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Summary of Contents for NCP1351B

Page 1: ...plays FPD 32 the power supply is generally internal and requires anywhere from 120 to 500 W depending on the size of the TV and the feature set Several voltage rails are needed to supply the different...

Page 2: ...cal topologies are not ideal for meeting these needs Flyback Transformer Usage is Far from Pptimal Forward the EMI Signature is Not Reduced to its Minimum Architecture Overview First the use of active...

Page 3: ...scillator driven by current flowing from the RT pin Fmin is set with 3 accuracy and Fmax has an accuracy of 15 Because the oscillator is current driven additional regulation loops can easily be connec...

Page 4: ...s are charged through diode D4 This voltage is divided by resistors R7 R11 R18 R28 R51 R38 R46 and R47 and is connected to the FB pin of the PFC in order to set the regulation level The current flowin...

Page 5: ...e NCP1351B the SMPS is powered from auxiliary winding W4 of the TR2 The circuit around Q17 R108 R113 R116 R127 and R128 is used to turn off the standby SMPS if the mains input is disconnected e g main...

Page 6: ...stage starts Thus the PFC stage never starts operating Because of negative current sense of the NCP1351B it is not possible to connect voltage from C55 directly to capacitor C56 because the current ch...

Page 7: ...rom the BO pin when the Vbulk is lower than the set level it is not possible to connect the BO pin directly to the PFC feedback divider As soon as this is connected the current sunk from the divider d...

Page 8: ...cup mode will be explained hereinafter The Rt pin is the only pin used for setting the operating frequency of this IC The soft start of this LLC is set by R83 which dictates the frequency at which sof...

Page 9: ...r of Q7 is grounded soft start capacitor C51 is discharged through D18 and transistor Q6 is turned on through diode D19 and R86 Transistor Q6 pulls the BO pin over 2 V and the NCP1392B immediately sto...

Page 10: ...voltage on the cathode of TLV431 is lower than Vcc In this situation current starts to flow through the EB junction of Q12 and through resistor R89 turning on the transistor Capacitor C53 is charged...

Page 11: ...d by RC segment R1 R9 C1 and C9 to suppress overshoot on the diode The output voltage is divided by R44 and the parallel combination of R84 and R85 IC4 is biased by resistor R42 Resistor R41 and capac...

Page 12: ...iode conducts This short but very high current can damage them A simulation tool is used to see how the resonant tank will operate with this transformer The results are shown in Figure 14 Vmin Vnom Vm...

Page 13: ...ign for end customers The main goal of this document is to illustrate a typical application where these controller would be used and illustrate some functions that can be implemented with external sub...

Page 14: ...put ripple Figure 20 Nominal Vbulk no load output ripple Figure 21 Nominal Vbulk transient respond to change load from 4 A to 0 4 A 50 duty cycle 10 Hz frequency Measured overshoot is 190 mV Figure 22...

Page 15: ...AC no load Primary current and drain voltage switching frequency of 2 kHz Figure 27 PFC coil current drain voltage for 265 VAC measured at peak of the sinusoidal waveform nominal load on the outputs F...

Page 16: ...32 LLC skip mode Primary current and output voltage s ripple for no load on the outputs Figure 33 LLC skip mode Primary current and output voltage s ripple for 100 mA on the 24 V line output Figure 34...

Page 17: ...8 LLC short overload primary current output voltage and C53 voltage Figure 39 LLC long overload primary current output voltage and C53 voltage Figure 40 LLC shorting of the output primary current outp...

Page 18: ...oft start to nominal load Efficiency 74 76 78 80 82 84 86 88 90 20 40 60 80 100 120 140 160 180 200 Output Power W Efficiency Figure 44 Efficiency of Entire Demoboard Figure 45 Conducted EMI Signature...

Page 19: ...AND8344 D www onsemi com 19 Figure 47 Schematic of the SMPS...

Page 20: ...AND8344 D www onsemi com 20 Figure 48 Bottom Side of the PCB...

Page 21: ...AND8344 D www onsemi com 21 Figure 49 Bottom Labels...

Page 22: ...AND8344 D www onsemi com 22 Figure 50 Top Labels...

Page 23: ...AND8344 D www onsemi com 23 Figure 51 Photo of the Demoboard with Temperatures Measured for 230 Vac and 110 Vac in Bracket Ambient Temperature 265C Full Load Vertical Position...

Page 24: ...AND8344 D www onsemi com 24 Figure 52 Photo of the Demoboard with Heatsinks Removed...

Page 25: ...AND8344 D www onsemi com 25 Figure 53 Photo of the Demoboard Bottom Side...

Page 26: ...AND8344 D www onsemi com 26...

Page 27: ...AND8344 D www onsemi com 27...

Page 28: ...on special consequential or incidental damages Typical parameters which may be provided in SCILLC data sheets and or specifications can and do vary in different applications and actual performance may...

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