LT8309/LT3748 No-Opto Flyback Converter with Synchronous Rectifier (DC1961A)
Demonstration circuit 1961A featuring the LT8309 and LT3748 in an isolated no-opto flyback converter providing 12V at 5A from a 36V-72V input range.
Overview
Demonstration circuit 1961A is an isolated, no-optocoupler flyback converter featuring the LT8309 secondary synchronous driver and the LT3748 boundary conduction mode flyback controller. The circuit regulates a 12V, 5A output from an input source ranging from 36V to 72V. By sensing output voltage directly from the primary side, the LT3748 eliminates the need for an optocoupler. The LT8309 synchronous rectifier driver replaces the standard secondary diode with an N-channel MOSFET, improving thermal performance and efficiency. To ensure robust short-circuit performance, the LT8309 is biased from the rectified drain voltage node of the synchronous MOSFET, allowing it to remain active even when the output is shorted.
Use Cases
- Isolated power supplies
- Industrial control systems
- Telecom equipment
- High-efficiency power conversion
Topics
Referenced Parts
CMZ5928B TR
Central Semiconductor
Diode Zener, 13V SMA
BAV20W-7-F
Diodes Incorporated
DIODE, SWITCHING 150V, 0.2A, SOD123
SMBJ85A-13-F
Diodes Incorporated
Diode, TVS UNI-DIR 85V, 600W, SMB
LT3748EMS#PBF
Linear Technology
I.C., No-Opto Flyback Converter
LT8309ES5#PBF
Linear Technology
I.C., Rectifier Driver, TSOT23-S5
EMZA800ADA470MJA0G
Nippon Chemi-Con
CAP., ALUM, 47μF, 80V, 20%, SMD
PA1736NLT
Pulse Electronics
Transformer, ±5%, 20.5μH, EFD20 Platform
RL3720WT-R010-F
Susumu
Sense Res., RL Vert. 0.010, 1W, 1%, 0815
SOD123
Diodes
17 2 D4, D5 DIODE, SWITCHING 150V, 0.2A, SOD123 Diodes Inc., BAV20W-7-F
| 06033A470JAT2A | AVX | Cap., NPO, 47pF, 25V, 5%, 0603 |
| 06033A471JAT2A | AVX | Cap., NPO, 470pF, 25V, 5%, 0603 |
| 06033C333KAT2A | AVX | Cap., X7R, 0.033μF, 25V, 10%, 0603 |
| CMHZ5258BTR | Central Semiconductor | Zener Diode, 36V, SOD-123 |
| CMMR1U-02TR | Central Semiconductor | Diode, 1A/200V, SOD-123 |
| XAL6030-102MEB | Coilcraft | Inductor, 1μH, XAL6030 |
| XAL6060-223MEC | Coilcraft | Inductor, 22μH, XAL6060 |
| BSC047N08NS3G | Infineon | MOSFET, N-CH, 80V, 100A, TDSON-8 |
| BSC320N20NS3 G | Infineon | MOSFET, N-CH, 200V, 36A, TDSON-8 |
| 2501-2-00-80-00-00-07-0 | Mill-Max | Turret, Testpoint |
| GA343DR7GD472KW01L | Murata | Cap., X7R, 4700pF, 250V, 10%, 1812 |
| GRM21A7U2E121JW31D | Murata | Cap., U2J, 120pF, 250V, 5%, 0805 |
| GRM32ER61C476KE15L | Murata | Cap., X5R, 47μF, 16V, 10%, 1210 |
| C1608X7R1E224K | TDK | Cap., X7R, 0.22μF, 25V, 10%, 0603 |
| C2012X5R1C475M | TDK | Cap., X5R, 4.7μF, 16V, 20%, 0805 |
| C2012X5R1E475K | TDK | Cap., X5R, 4.7μF, 25V, 10%, 0805 |
| C2012X7S2A105K | TDK | Cap., X7S, 1μF, 100V, 10%, 0805 |
| C3216X7R2A105M | TDK | Cap., X7R, 1μF, 100V, 20%, 1206 |
| C3225X7S2A475MT | TDK | Cap., X7S, 4.7μF, 100V, 20%, 1210 |
| CRCW06030000Z0EA | Vishay | Res/Jumper, Chip 0Ω, 0.25W, 5A, 0603 |
| CRCW06031M20JNEA | Vishay | Res., Chip 1.2M, 0.1W, 5%, 0603 |
| CRCW06033R00JNEA | Vishay | Res., Chip 3, 1/10W, 5%, 0603 |
| CRCW060351K0JNEA | Vishay | Res., Chip 51k 0.1W 5% 0603 |
| CRCW060360K4FKEA | Vishay | Res., Chip 60.4k, 0.1W, 1%, 0603 |
| CRCW06036K04FKEA | Vishay | Res., Chip 6.04k, 0.1W, 1%, 0603 |
| CRCW06037K50FKEA | Vishay | Res., Chip 7.50k, 0.1W, 1%, 0603 |
| CRCW0805160KFKEA | Vishay | Res., Chip 160k, 1/8W, 1%, 0805 |
| CRCW08053R00JNEA | Vishay | Res., Chip 3Ω, 1/8W, 5%, 0805 |
| CRCW080568R0JNEA | Vishay | Res., Chip 68, 1/8W, 5%, 0805 |
| CRCW12062K37FKEA | Vishay | Res., Chip 2.37k, 0.25W, 1%, 1206 |
| CRCW1210100RJNEA | Vishay | Res., Chip 100, 0.50W, 5%, 1210 |
| TDSON-8 | Infineon | 22 1 Q2 MOSFET, N-CH, 200V, 36A, TDSON-8 Infineon, BSC320N20NS3 G |
| TDSON-8 | Infineon | 21 1 Q1 MOSFET, N-CH, 80V, 100A, TDSON-8 Infineon, BSC047N08NS3 G |
| CMZ5928B TR | Central Semiconductor | Diode Zener, 13V SMA |
| BAV20W-7-F | Diodes Incorporated | DIODE, SWITCHING 150V, 0.2A, SOD123 |
| SMBJ85A-13-F | Diodes Incorporated | Diode, TVS UNI-DIR 85V, 600W, SMB |
| LT3748EMS#PBF | Linear Technology | I.C., No-Opto Flyback Converter |
| LT8309ES5#PBF | Linear Technology | I.C., Rectifier Driver, TSOT23-S5 |
| EMZA800ADA470MJA0G | Nippon Chemi-Con | CAP., ALUM, 47μF, 80V, 20%, SMD |
| PA1736NLT | Pulse Electronics | Transformer, ±5%, 20.5μH, EFD20 Platform |
| RL3720WT-R010-F | Susumu | Sense Res., RL Vert. 0.010, 1W, 1%, 0815 |
| SOD123 | Diodes | 17 2 D4, D5 DIODE, SWITCHING 150V, 0.2A, SOD123 Diodes Inc., BAV20W-7-F |