Datasheet MP6925A (Monolithic Power Systems) - 12
| Hersteller | Monolithic Power Systems |
| Beschreibung | Fast Turn-Off, CCM/DCM Compatible, Dual-LLC, Synchronous Rectifier with lmproved Noise Immunity |
| Seiten / Seite | 15 / 12 — MP6925A – FAST TURN-OFF, CCM/DCM DUAL LLC SYNCHRONOUS RECTIFIER. IPEAK. … |
| Dateiformat / Größe | PDF / 1.3 Mb |
| Dokumentensprache | Englisch |
MP6925A – FAST TURN-OFF, CCM/DCM DUAL LLC SYNCHRONOUS RECTIFIER. IPEAK. IDS. Body diode. conducts. it ). c u. DON. oi u
Modelllinie für dieses Datenblatt
Textversion des Dokuments
MP6925A – FAST TURN-OFF, CCM/DCM DUAL LLC SYNCHRONOUS RECTIFIER
Figure 15 shows how tON affects system Figure 12 shows how different turn-on delay efficiency. values affect efficiency according to different output voltages. To keep the body diode
IPEAK
conduction loss at a fairly low level (below 0.5%
V
of the output power), the turn-on delay should
DS IDS
be less than 5% of the switching cycle. For example, in a fSW = 200kHz LLC system, the
IF
switching cycle is about 5µs. It is recommended
Body diode conducts
to select the MOSFET so that tDON is shorter than 250ns.
VF
6 Vout=5V
V n GS o
Vout=12V
it )
5 Vout=24V
c u %( t d r DON n e o
4
C w o e P d t oi u
3
Figure 11: Turn-On Delay Effect on Efficiency D p t y u d O
2 During t
o o
DON, the body diode of the SR MOSFET
B t f s
conducts, which leads to a power loss (P
o s
ON)
o o i L
1 that can be calculated with Equation (3):
t a R
0 V I 0 5 10 15 20 25 P F F 2f t V I f t (3)
Ratio of Turn-On Delay to Switching Cycle (%)
ON SW DON F F SW DON 2
Figure 12: Turn-On Delay vs. Power Loss
Where VF is the body diode forward voltage drop, I The turn-off delay (tDOFF) is critical in CCM F is the switching current when the turn- on delay (t applications with fast transients. Choose the DON) has ended, and fSW is the switching frequency. MOSFET that keeps tDOFF below the CCM current transient duration. Otherwise, the If the switching current is considered to be a MOSFET may require a lower QG, or an complete sine wave, IF can be estimated with external totem pole driver circuit may be added Equation (4): to prevent shoot-through. I I sin(2 f t ) (4) F PEAK SW DON Where IPEAK is the peak switching current through the MOSFET, calculated with Equation (5): I I (5) PEAK OUT 2 Where IOUT is the system output current. When plugging the values from Equation (4) and Equation (5) into Equation (3), the turn-on delay power loss (PON) through the SR MOSFET’s body diode can be calculated with Equation (6): P I V f t sin(2 f t ) ON OUT F SW DON SW DON 2 (6) MP6925A Rev. 1.0 www.MonolithicPower.com
12
2/26/2020 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2020 MPS. All Rights Reserved.
Figure 15 shows how tON affects system Figure 12 shows how different turn-on delay efficiency. values affect efficiency according to different output voltages. To keep the body diode
IPEAK
conduction loss at a fairly low level (below 0.5%
V
of the output power), the turn-on delay should
DS IDS
be less than 5% of the switching cycle. For example, in a fSW = 200kHz LLC system, the
IF
switching cycle is about 5µs. It is recommended
Body diode conducts
to select the MOSFET so that tDON is shorter than 250ns.
VF
6 Vout=5V
V n GS o
Vout=12V
it )
5 Vout=24V
c u %( t d r DON n e o
4
C w o e P d t oi u
3
Figure 11: Turn-On Delay Effect on Efficiency D p t y u d O
2 During t
o o
DON, the body diode of the SR MOSFET
B t f s
conducts, which leads to a power loss (P
o s
ON)
o o i L
1 that can be calculated with Equation (3):
t a R
0 V I 0 5 10 15 20 25 P F F 2f t V I f t (3)
Ratio of Turn-On Delay to Switching Cycle (%)
ON SW DON F F SW DON 2
Figure 12: Turn-On Delay vs. Power Loss
Where VF is the body diode forward voltage drop, I The turn-off delay (tDOFF) is critical in CCM F is the switching current when the turn- on delay (t applications with fast transients. Choose the DON) has ended, and fSW is the switching frequency. MOSFET that keeps tDOFF below the CCM current transient duration. Otherwise, the If the switching current is considered to be a MOSFET may require a lower QG, or an complete sine wave, IF can be estimated with external totem pole driver circuit may be added Equation (4): to prevent shoot-through. I I sin(2 f t ) (4) F PEAK SW DON Where IPEAK is the peak switching current through the MOSFET, calculated with Equation (5): I I (5) PEAK OUT 2 Where IOUT is the system output current. When plugging the values from Equation (4) and Equation (5) into Equation (3), the turn-on delay power loss (PON) through the SR MOSFET’s body diode can be calculated with Equation (6): P I V f t sin(2 f t ) ON OUT F SW DON SW DON 2 (6) MP6925A Rev. 1.0 www.MonolithicPower.com
12
2/26/2020 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2020 MPS. All Rights Reserved.