Primary-side Regulaion PWM Conroller for Auomoive Applicaions SFA2 Daa Shee Descripion The SFA2 is he swiching power supply IC for flyback circui and has high accuracy error amplifier. When he load of he power supply circui becomes ligh, he operaion of IC becomes he burs oscillaion mode in order o improve he circui efficiency. By employing he primary-side regulaion, he IC realizes low componen couns and design-friendliness, leading o downsizing and sandardizaion of he power supply circui. Feaures AEC-Q1 Qualified Curren Mode Type PWM Conrol (Swiching frequency can be adjused by exernal capacior) Reducing Exernal Componen Coun by Primary-side Regulaion Buil-in High Accuracy Error Amplifier (V FB = 2.5 V ± 2%, 4 C o 125 C) Operaion Mode Normal Operaion: PWM Mode Ligh Load Operaion: Burs Oscillaion Sof Sar Funcion (Sarup ime can be adjused by exernal capacior) Drive Oupu Sop Funcion Proecions: Overcurren Proecion (OCP): Pulse-by-Pulse Overload Proecion (OLP): Auo-resar Thermal Shudown Proecion (TSD) wih Hyseresis: Auo-resar Package SOP8 Specificaions No o scale Maximum Power Supply Volage, V CC 36 V Adjusable Swiching Frequency (2 khz o 2 khz) Applicaions For following Isolaion auxiliary power supply: Inverer On-board Charger (OBC) Baery Managemen Sysem (BMS) Typical Applicaion IN T1 D51 OUT1 (+) C1 C2 D1 R2 R1 P S1 C51 C52 R51 OUT1 (-) C3 R3 Q1 R4 R5 5 6 7 8 SFA2 FREQ SS COMP GND DRIVE FB OCP VCC 4 3 2 1 C5 C9 C7 R7 R8 R1 D2 C8 D S2 D52 C53 C54 R52 OUT2 (+) OUT2 (-) R6 C6 C4 R9 SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 1
Conens Descripion ------------------------------------------------------------------------------------------------------ 1 Conens --------------------------------------------------------------------------------------------------------- 2 1. Absolue Maximum Raings ----------------------------------------------------------------------------- 3 2. Recommended Operaing Condiions ----------------------------------------------------------------- 3 3. Elecrical Characerisics -------------------------------------------------------------------------------- 3 4. Performance Curves -------------------------------------------------------------------------------------- 5 5. Block Diagram --------------------------------------------------------------------------------------------- 6 6. Pin Configuraion and Definiions --------------------------------------------------------------------- 6 7. Typical Applicaion --------------------------------------------------------------------------------------- 7 8. Physical Dimensions -------------------------------------------------------------------------------------- 8 9. Marking Diagram ----------------------------------------------------------------------------------------- 8 1. Timing Char ----------------------------------------------------------------------------------------------- 9 11. Operaional Descripion ------------------------------------------------------------------------------- 11 11.1. Pin Descripions ----------------------------------------------------------------------------------- 11 11.1.1. VCC -------------------------------------------------------------------------------------------- 11 11.1.2. FB 11 11.1.3. GND -------------------------------------------------------------------------------------------- 11 11.1.4. SS 11 11.1.5. FREQ ------------------------------------------------------------------------------------------ 11 11.1.6. COMP ----------------------------------------------------------------------------------------- 11 11.1.7. DRV -------------------------------------------------------------------------------------------- 11 11.1.8. OCP -------------------------------------------------------------------------------------------- 11 11.2. IC Sarup ------------------------------------------------------------------------------------------ 12 11.3. Sof Sar Funcion -------------------------------------------------------------------------------- 12 11.4. Consan Volage Conrol ------------------------------------------------------------------------ 12 11.5. Burs Funcion in Ligh Load ------------------------------------------------------------------- 13 11.6. Oscillaion Frequency Seing ------------------------------------------------------------------- 13 11.7. Drive Sop Funcion------------------------------------------------------------------------------- 14 11.8. Overcurren Proecion (OCP) ----------------------------------------------------------------- 14 11.9. Overload Proecion (OLP) ---------------------------------------------------------------------- 15 11.1. Thermal Shudown (TSD) ----------------------------------------------------------------------- 15 Imporan Noes ---------------------------------------------------------------------------------------------- 16 SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 2
1. Absolue Maximum Raings Curren polariies are defined as follows: curren going ino he IC (sinking) is posiive curren (+); curren coming ou of he IC (sourcing) is negaive curren ( ). Unless oherwise specified, T A = 25 C. Parameer Symbol Condiions Raing Uni Remarks OCP Pin Volage V OCP 5 o 5 V SS Pin Volage V SS.3 o 9 V FB Pin Volage V FB.3 o 5 V VCC Pin Volage V CC o 36 V COMP Pin Volage V COMP.3 o 5 V FREQ Pin Volage V FREQ.3 o 5 V DRIVE Pin Peak Curren I DRV(PEAK) 27 o 54 ma DRIVE Pin DC Curren I DRV(DC) 9 o 18 ma Power Dissipaion P D * Mouning on PCB 1.2 W Juncion Temperaure T J 4 o 15 C Sorage Temperaure T sg 4 o 15 C * PCB: 42 mm 32 mm in size, 1 mm in hickness 2. Recommended Operaing Condiions Parameer Symbol Condiions Min. Typ. Max. Uni Remarks VCC Pin Volage V CC 6 24 V Swiching Frequency f OSC 2 2 khz 3. Elecrical Characerisics Curren polariies are defined as follows: curren going ino he IC (sinking) is posiive curren (+); curren coming ou of he IC (sourcing) is negaive curren ( ). Unless oherwise specified, T A = 4 C o 125 C, VCC = 14 V, and FB = SS = OCP = V. The following elecrical characerisics in T A = 4 C o 125 C are guaraneed by design. The shipping es emperaure of he producs is 3 C, 25 C, and 125 C. Parameer Symbol Condiions Min. Typ. Max. Uni Remarks Power Supply Sarup Operaion Operaion Sar Volage V CC(ON) 4.9 5.1 5.3 V Operaion Sop Volage V CC(OFF) 4.4 4.6 4.8 V Circui Curren in Operaion I CC(ON) 1. 2. 3.2 ma Circui Curren in Non-operaion Normal Operaion SS Pin High Threshold Volage of OLP Operaion SS Pin Low Threshold Volage of OLP Operaion I CC(OFF) VCC = 4.8 V.3.5 1. ma V HSS 1.9 2. 2.1 V V LSS.9 1. 1.1 V SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 3
Parameer Symbol Condiions Min. Typ. Max. Uni Remarks SS Pin Volage Hyseresis of OLP Operaion ΔV SS V HSS V LSS.9 1. 1.1 V SS Pin Source Curren I SRC(SS) SS =.9 V 19 15 11 µa SS Pin Sink Curren I SNK(SS) SS = 2.1 V 13 17 21 µa Swiching Frequency f OSC(2p) FREQ = 2 pf 85 1 115 khz FREQ Pin Source Curren I SRC(FREQ) FREQ =.9 V 33 3 27 µa FREQ Pin Sink Curren I SNK(FREQ) FREQ = 2.1 V 75 85 95 µa Oscillaion Circui High Threshold Volage Oscillaion Circui Low Threshold Volage V HF 1.9 2. 2.1 V V LF.9 1. 1.1 V Maximum Duy Cycle D MAX FREQ = 2pF 7 74 78 % Slope Compensaion Rae SLP 2.1 2.5 2.9 mv/% Feedback Volage V FB 2.45 2.5 2.55 V Burs Operaion Threshold Volage Drive Volage Minimum Drive Volage Minimum On-ime Proecion Funcion Leading Edge Blanking Time* V BURST V DRIVE V DRIVE(MIN) ON(MIN) FREQ = 2pF, COMP pin volage increases from V. FREQ = 3 V, 1 pulse VCC 6 V, FREQ = 3 V, 1 pulse OCP = 1 V, DRIVE = 68 pf.18 V 7.6 8.3 9. V 4 V 17 ns BW 1 ns OCP Threshold Volage V OCP.46.5.54 V OLP Delay Time OLP SS = 1 nf 32 42 52 ms Drive Sop Threshold Volage V ST 3.5 4. 4.5 V Thermal Shudown Operaing Temperaure* Thermal Shudown Release Temperaure* T JH(TSD) 15 165 C T JL(TSD) 15 C * Guaraneed by design. SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 4
ICC[mA] Vdrive[V] VFB[V] fosc[khz] fosc(2p)[khz] SFA2 4. Performance Curves fosc (khz) 1 1 1 1 1 1 1 C FREQ CFREQ[pF] (pf) fosc(2 p) (khz) 115 112 19 16 13 1 97 94 91 88 85-5 5 1 15 T A Ta[ ( C) ] Figure 4-1. Swiching Frequency, f OSC, vs. FREQ Pin Capacior, C FREQ Figure 4-2. Swiching Frequency (FREQ = 2 pf) Temperaure Characerisics VDRIVE (V) 9 8 7 6 5 4 3 2 1 5 1 15 2 25 V CC VCC[V] (V) VFB (V) 2.55 2.54 2.53 2.52 2.51 2.5 2.49 2.48 2.47 2.46 2.45-5 5 1 15 T Ta[ ] A ( C) Figure 4-3. DRV Pin Volage, V DRIVE, vs. VCC Pin Volage, V CC Figure 4-4. Feedback Volage, V FB, Temperaure Characerisics ICC (ma) 4 3.5 3 2.5 2 1.5 1.5 5 1 15 2 25 V CC VCC[V] (V) Figure 4-5. VCC Pin Curren, I CC, vs. VCC Pin Volage,V CC SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 5
5. Block Diagram VCC (1) FREQ (5) SS (4) OCP (8) (7) DRIVE FB (2) (6) COMP (3) GND 6. Pin Configuraion and Definiions Pin No. Pin Name Funcion VCC 1 8 OCP 1 VCC Power supply volage inpu FB GND SS 2 3 4 7 6 5 DRIVE COMP FREQ 2 FB Consan volage conrol signal inpu 3 GND Ground 4 SS 5 FREQ Connecing capacior for sof-sar ime and OLP delay ime seing, and he DRIVE pin sop signal inpu Connecing capacior for swiching frequency seing 6 COMP Connecing capacior for phase compensaion 7 DRIVE Gae drive oupu 8 OCP Overcurren deecion signal inpu SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 6
7. Typical Applicaion In applicaions having a power supply specified such ha he drain pin of exernal power MOSFET has large ransien surge volages, a clamp snubber circui of a capacior-resisor-diode (C2, R2, and D1) combinaion should be added on he primary winding P, or a damper snubber circui of a capacior or a resisor-capacior (C3 and R3) combinaion should be added beween he drain pin and he source pin. IN T1 D51 OUT1 (+) C1 C2 D1 R2 R1 P S1 C51 C52 R51 OUT1 (-) C3 R3 Q1 R4 R5 5 6 7 8 SFA2 FREQ SS COMP GND DRIVE FB OCP VCC 4 3 2 1 C5 C9 C7 R7 R8 R1 D2 C8 D S2 D52 C53 C54 R52 OUT2 (+) OUT2 (-) R6 C6 C4 R9 Figure 7-1. Flyback Sep-up/ Sep-down Converer (Primary-side Deecion) IN C1 C2 D1 R2 R1 T1 S D51 P C51 C52 R51 PC1 R52 C53 R53 R54 R55 OUT1(+) OUT1(-) C3 R3 R6 Q1 R4 R5 C6 PC1 C7 SFA2 5 FREQ 6 COMP 7 DRIVE 8 OCP C4 SS GND FB VCC 4 3 2 1 C5 C9 D52 C54 C55 R56 OUT2(+) OUT2(-) Figure 7-2. Flyback Sep-up/ Sep-down Converer (Secondary-side Deecion) SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 7
8. Physical Dimensions SOP8 (Beween he roo of lead and he backside) NOTES: - Dimensions in millimeers - Bare lead frame: Pb-free (RoHS complian) Enlarged View of A 9. Marking Diagram 8 1 S F A 2 S K Y M D D Par Number Lo Number: Y is he las digi of he year of manufacure ( o 9) M is he monh of he year (1 o 9, O, N, or D) DD is he day of he monh (1 o 31) Conrol Number SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 8
1. Timing Char V CC(ON) V CC(OFF) V FB V BURST ΔV SS V HSS V LSS V HF V LF DRIVE V OCP IC sars Oupu volage increases. Sof sar operaion Normal operaion DRIVE oupu sops under ligh load condiion IC sops When he COMP pin volage decreases o V BURST or less, he IC operaion becomes ino burs oscillaion mode. The on-ime and he inermien cycle depend on he specificaion of ypical applicaion circui. Figure 1-1. Normal Operaion SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 9
V CC(ON) V CC(OFF) OLP OLP 8 V ST DRIVE Limied by overcurren proecion V OCP V OCP Overcurren saus When overcurren saus is released, he overload proecion is also released. Figure 1-2. Proecion Funcion When he drive sop signal is inpu o he SS pin, and hen he SS pin volage becomes V ST or more, he IC sops he DRIVE pin oupu signal. SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 1
DRV Pin Volage (V) SFA2 11. Operaional Descripion Unless oherwise specified, he characerisics values are shown in ypical value. Curren polariies are defined as follows: curren going ino he IC (sinking) is posiive curren (+); curren coming ou of he IC (sourcing) is negaive curren ( ). 11.1. Pin Descripions 11.1.1. VCC The VCC pin is he power inpu pin of he IC. When he VCC pin volage flucuaes grealy, he IC may malfuncion. When he impedance of power supply line is high, i is required o add resisors and capaciors o he VCC pin in order o suppress he VCC pin volage flucuaion. 11.1.2. FB The FB pin is he inpu of he oupu volage of a feedback signal. The IC conrols he FB pin volage o V FB = 2.5 V (see Secion 11.4). 11.1.3. GND The GND pin is he IC conrol ground pin. Since he flucuaion of he ground pin poenial may cause he IC malfuncion, he conrol ground race should be separaed from power ground and conneced o he GND pin as shor as possible. Please pay aenion o design of he conrol ground race o avoid he effec from he high frequency curren line. 11.1.4. SS The SS pin has hree funcions as follows: Seing he sof sar ime (see Secion 11.3) Sopping he drive (see Secion 11.7) Seing he OLP (Over Load Proecion) delay ime (see Secion 11.9) The capacior, C SS, for seing he sof sar ime and he OLP delay ime is conneced o he SS pin. These boh funcions should be aken ino accoun in seing he value of C SS. In normal operaion, he waveform of CSS pin volage is riangular. The SS pin charges he C SS by I SRC(SS) = 15 µa and discharges he C SS by I SNK(SS) = 17 µa when he SS pin volage reaches V HSS = 2. V. The SS pin sars o charge again when he SS pin volage decreases o V LSS = 1. V. 11.1.5. FREQ The FREQ pin is conneced o he capacior, C FREQ, for seing he oscillaion frequency of he DRV pin oupu. For he seing of oscillaion frequency, see Secion 11.6. 11.1.6. COMP The COMP pin is he oupu pin of an inernal error amplifier. The capacior for phase compensaion is conneced o he COMP pin. The capaciance is se according o he acual operaion. When he secondary oupu volage is conrolled using an opocoupler, an opocoupler is conneced o he COMP pin as shown in Figure 7-2. 11.1.7. DRV The gae of he power MOSFET is conneced o he DRV pin. The power of he DRV pin is supplied by he VCC pin via he inernal regulaor. The relaion beween he VCC pin volage and he DRV pin volage is shown in Figure 11-1. The DRV pin volage is clamped a V DRIVE = 8.3 V. The inernal regulaor is swiched by VCC pin volage of around 7 V and suppresses he drive volage drop a he VCC pin volage drop. The source poenial of he power MOSFET is increased by abou.5 V due o a drain curren deecion resisor. Therefore, i is required o selec he power MOSFET wih he gae hreshold volage ha is lower enough han he minimum drive volage, 4 V (min.). 9 8 7 6 5 4 3 2 1 5 1 15 2 25 VCC Pin Volage (V) Figure 11-1. 11.1.8. OCP VCC Pin Volage vs. DRV Pin Volage The OCP pin is he deecion pin of he drain curren of he power MOSFET. The curren deecion resisor, R OCP, is conneced beween he source and GND of he power MOSFET, and he volage is inpu o he OCP pin. The drain curren value inpu o he OCP pin is used SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 11
for he oupu volage conrol (see Secion 11.4) and he overcurren proecion. For he seing of overcurren deecion resisor, see Secion 11.8. 11.2. IC Sarup Applying a volage o he VCC pin sars he inernal regulaor. The regulaor is a highly accurae power supply of 2.5 V ± 2%. When he VCC pin volage reaches he Operaion Sar Volage, V CC(ON) = 5.1 V, or higher, he power supply in he IC urns on and sars he operaion. When he VCC pin volage decreases o be he Operaion Sop Volage, V CC(OFF) = 4.6 V, or lower, he power supply in he IC urns off and sops he operaion. C SS I SRC(SS) Figure 11-2. SS Pin Volage V HSS V LSS OCP Pin Volage SS 4 OCP 8 Sofsar SS Pin Peripheral Circui I SRC(SS) I SNK(SS) OCP comparaor 11.3. Sof Sar Funcion The IC operaes by sof sar in he power supply sarup. This reduces he volage and curren sress of he power MOSFET and he secondary recifier diode. The sof sar period is se by he capacior, C SS, conneced o he SS pin. When he VCC pin volage is V CC(ON) or higher afer he power is applied, he IC sars he operaion; and he C SS is charged by he SS Pin Source Curren, I SRC(SS) = 15 µa. When he power is supplied, he SS pin volage sars increasing. The OCP hreshold volage also increases proporional o he SS pin volage unil he SS pin volage reaches V HSS = 2. V. Thus he drain curren gradually increases in his period. When once he SS pin volage reaches he V HSS, he OCP hreshold volage is fixed a V OCP =.5 V. The approximae ime of sof sar operaion, SS, is calculaed by he following equaion. V OCP Figure 11-3. Sof Sar Operaion 11.4. Consan Volage Conrol The oupu volage conrol of swiching power supply uses he curren-mode conrol mehod ha provides he high speed response and sable operaion. The IC has he error amplifier beween he FB pin and he COMP pin, and conrols he FB pin volage o V FB = 2.5 V. Wihou an opocoupler, he secondary oupu volage is conrolled by deecing he volage coupled by he secondary oupu and he ransformer in he primary side, using he auxiliary winding, D, as shown in Figure 11-4. The relaion beween he smoohing volage, V D, and he secondary oupu volage, V OUT, is deermined by he raio of he auxiliary winding urns, N D, and he secondary winding urns, N S, as shown in Equaion (2). (2) The C SS value should be se wih he delay ime of OLP, OLP, aken ino accoun. If he C SS value is oo small, he overload proecion is acivaed in he sarup; and he sarup failure may be caused. The recommended C SS value is.1 µf o.47 µf, and should be deermined by confirming he acual operaion. (1) V D is divided by resisors. The divided volage is inpu o he FB pin. The IC conrols he FB pin volage o V FB = 2.5 V. Thus, he smoohing volage, V D, is calculaed by he following equaion. (3) The secondary oupu volage, V OUT, is calculaed by he following equaion. (4) SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 12
The acual V OUT and he calculaed value in Equaion (4) do no mach because of he leakage inducance beween he secondary-side winding and he auxiliary winding, and he difference of he forward volage, V F, beween he secondary recifier diode, D51, and he auxiliary winding diode, D2. Therefore, R8 and R9 mus be adjused by confirming he acual operaion. Where N D = N S and V OUT = V D, he accuracy of he secondary oupu volage is improved by using he same diode producs for D51 and D2. When here is a big difference of power dissipaion beween he auxiliary winding and he secondary side, he load regulaion is degraded due o he leakage inducance of a ransformer. In his case, he dummy resisor, R1, is conneced across he auxiliary winding. The value of R1 is adjused by confirming he acual operaion since i differs depending on he power supply specificaion. FB 2 R8 R9 Figure 11-4. V D R1 D2 D C8 P T1 Auxiliary winding S D51 OUT (+) C51 OUT (-) Deecion by Auxiliary Winding The volage conrol operaion in ligh/heavy load is as follows: (see Figure 11-5) Ligh Load Condiions When he auxiliary winding volage, V D, and he FB pin volage increase according o he oupu volage rise, he COMP pin volage decreases. The IC generaes he arge value of he FB comparaor by adding he slope compensaion signal o he COMP pin volage. The IC conrols he DRV oupu duy cycle by comparing he peak of he arge value and he OCP pin volage (he drain curren of he power MOSFET deeced by deecion resisor). When he COMP pin volage decreases, he arge value of he FB comparaor drops. As a resul, he drain peak curren of he power MOSFET decreases o suppress he oupu volage rise. Heavy Load Condiions In his case, conrary o he operaion describe above, he arge volage of FB comparaor increases. As a resul, he drain peak curren also increases o suppress he oupu volage drop. FB Pin Volage COMP Pin Volage OCP Pin Volage DRV Pin Volage Figure 11-5. Targe value Ligh load Heavy load Consan Volage Operaion 11.5. Burs Funcion in Ligh Load When he oupu volage of he power supply decreases, he on-ime of DRV pin shorens due o he COMP pin volage reducion. As a resul, he oupu volage is conrolled o be consan. However, he on ime of DRV pin canno be shorer han he Minimum On-ime, ON(MIN). Therefore, he operaion of he IC is auomaically swiched o he burs oscillaion operaion (inermien oscillaion) in ligh load. When he COMP pin volage decreases o Burs Operaion Threshold Volage, V BURST =.18 V, or lower, he DRV pin oupu is sopped. Then, he oupu volage decreases, resuling in he decrease of FB pin volage. This increases he COMP pin volage; and he DRV pin oscillaes again. As jus described, he burs oscillaion operaion of he DRV pin is repeaed in ligh load. The following facors depend on he applicaion circui and power supply specificaion. - he burs oscillaion frequency and on-ime in burs oscillaion operaion - he sop period of DRV pin 11.6. Oscillaion Frequency Seing The oscillaion frequency of he DRV pin oupu is se by he capacior, C FREQ, conneced o he FREQ pin (see Figure 11-6). The waveform of he FREQ pin volage becomes riangular due o he charge/discharge of C FREQ. C FREQ is charged by I SRC(FREQ) = 3 µa as shown in Figure 11-7. When he FREQ pin volage reaches V HF = 1. V, C FREQ is discharged by I SNK(FREQ) = 85 µa. When he FREQ pin volage decreases o V LF = 1. V, C FREQ is charged by I SRC(FREQ) again. The oscillaion frequency of he DRV pin is deermined by he frequency of he riangular waveform. SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 13
Oscillaion Frequency (khz) SFA2 In addiion, he maximum duy cycle is conrolled by he raio of charge and discharge. For he seing of oscillaion frequency of he DRV pin, see Figure 11-8. Ulimaely, he confirmaion of acual operaion is required. C FREQ I SNK(FREQ) Figure 11-6. I SRC(FREQ) FREQ 5 OSC FREQ Pin Peripheral Circui 11.8. Overcurren Proecion (OCP) The IC has he pulse-by-pulse Overcurren Proecion (OCP). When he OCP pin volage exceeds he OCP Threshold Volage, V OCP =.5 V, a every swiching cycle, he OCP is acivaed. When he OCP is acivaed, i urns off he DRV pin oupu o urn off he power MOSFET, resuling in suppressing he peak of drain curren. A high frequency swiching curren flows o he deecion resisor. If he resisor wih high inernal inducance is used, he malfuncions may be caused. The resisor wih low inernal inducance and high surge capabiliy mus be seleced. In addiion, when he IC malfuncions due o surges in swiching operaion, he RC filer is added o he OCP pin. FREQ Pin Volage V HF V LF Figure 11-7. FREQ Pin Volage Waveform Design Example of Curren Deecion Resisor The value of he curren deecion resisor, R OCP, is se according o he following calculaion example in disconinuous operaion as a reference. Since he R OCP and he calculaion example do no mach in coninuous operaion, i is required o ulimaely adjus by confirming he acual operaion. The peak drain curren, I PEAK, in disconinuous operaion is calculaed by he following equaion. 1 (5) 1 Where: V IN is inpu volage, P OUT is oupu power, η is efficiency and D is duy cycle of he power MOSFET. 1 1 1 1 1 C FREQ (pf) Figure 11-8. 11.7. Drive Sop Funcion Oscillaion Frequency vs. C FREQ (Reference) The IC has he drive sop funcion. When a volage is exernally applied o he SS pin, he funcion is acivaed, forcibly fixes he DRV pin oupu o low level, and sops he oscillaion. The inpu volage o he SS pin mus be se higher han 4.5 V and lower han 9 V. When he SS pin volage is lower han Drive Sop Threshold Volage, V ST, afer he exernal applied volage is sopped, he DRV pin sars oscillaing again. The relaion beween he power, P, and he drain curren, I D, is shown in he following equaion. The drain curren is proporional o. If he OCP is designed o operae a 13% of he raed load (he maximum oupu power a he minimum inpu volage), he peak of drain curren a he OCP operaion poin is abou 114% ( ) of I PEAK a he raed load. The curren deecion resisance, R OCP, is calculaed by he following equaion. (6) (7) Where: D (MAX) is he duy cycle a he minimum inpu volage, V IN(MIN) and he maximum oupu power, P OUT(MAX), η is efficiency, and SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 14
V OCP is he OCP Threshold Volage (.5 V). The waveform of he curren flowing hrough he R OCP becomes riangular in disconinuous operaion. The RMS curren is calculaed by he following equaion. (8) 11.1. Thermal Shudown (TSD) The IC has he Thermal Shudown (TSD). When he juncion emperaure of he IC reaches T JH(TSD) = 165 C, he DRV pin oscillaion is sopped. When he juncion emperaure of he IC decreases o T JL(TSD) = 15 C or lower due o he oscillaion sop, he DRV pin oscillaion is resared. The power consumpion of R OCP is calculaed by he following equaion. (9) 11.9. Overload Proecion (OLP) The IC has he Overload Proecion (OLP). When he overload sae (where he peak of drain curren is limied by OCP, or he DRV pin operaes in he maximum duy cycle) coninues for a cerain ime, OLP, he OLP is acivaed; and he oscillaion of he DRV pin is sopped. This reduces he sress of he power MOSFET and he secondary recifier diode. The delay ime of he OLP, OLP, is deermined by he capaciance of C SS conneced o he SS pin. When C SS is 1 nf, OLP becomes 42 ms. In anoher capaciance, he approximae value of OLP can be calculaed by he following equaion. (1) The sof sar ime in Secion 11.3 should be aken ino accoun in seing he C SS capaciance. The oscillaion sop period of he DRV pin is 7 OLP. The DRV pin repeas oscillaion and sop on an 8 OLP cycle unil he overload sae is dissolved. OCP Pin Volage V OCP OLP 8 OLP DRV Pin Volage 7 OLP Figure 11-9. Overload Proecion Operaion SFA2-DSE Rev.1.3 SANKEN ELECTRIC CO., LTD. 15
Imporan Noes All daa, illusraions, graphs, ables and any oher informaion included in his documen (he Informaion ) as o Sanken s producs lised herein (he Sanken Producs ) are curren as of he dae his documen is issued. The Informaion is subjec o any change wihou noice due o improvemen of he Sanken Producs, ec. Please make sure o confirm wih a Sanken sales represenaive ha he conens se forh in his documen reflec he laes revisions before use. The Sanken Producs are inended for use as componens of elecronic equipmen or apparaus (ransporaion equipmen and is conrol sysems, home appliances, office equipmen, elecommunicaion equipmen, measuring equipmen, ec.). Prior o use of he Sanken Producs, please pu your signaure, or affix your name and seal, on he specificaion documens of he Sanken Producs and reurn hem o Sanken. 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