I want to add a Pb accumulator charging capability to a power path prioritizer. Since I need to have a high-side N-MOSFET driver anyway, the Zeta topology pops up rather naturally. The specs are: V_OUT=13.8V/4A, 200kHz, V_IN=9..20V. There will also be a current slope-limiting input choke (to buy some time for the overcurrent fuse to react), which adds a nice side-effect of smoothing the Zeta's input ripple. L2 is used for the same purpose, but on the accu side. It still has ~3uH@80A, which is incredibly good. The soft saturation property of MS-130060-2 is extremely useful. This way I can integrate three separate blocks (the prioritizer, the charger, the fuse) into a weird-looking 3-MOSFET Zeta. Replacing D1 with a 4th one would buy me synchronous rectification on the low side. It simulates flawlessly (attached below), but there is a practical question: what should the
40uF (or more) C3 be in practice, given the high reliability needs? The current changes from -7A to 11A, so a 20A continuous ripple rating @200kHz is the minimum. Would 8x22uF/35V 1206 X7R be OK, including all the C(U) fun?
Best regards, Piotr
Version 4 SHEET 1 880 680 WIRE 240 80 240 16 WIRE 400 80 400 16 WIRE -128 128 -144 128 WIRE 16 128 -48 128 WIRE 112 128 96 128 WIRE 160 128 112 128 WIRE 320 128 320 16 WIRE 320 128 256 128 WIRE 384 128 320 128 WIRE 512 128 480 128 WIRE 528 128 512 128 WIRE 752 128 608 128 WIRE 800 128 752 128 WIRE 320 144 320 128 WIRE 800 144 800 128 WIRE -144 160 -144 128 WIRE 112 160 112 128 WIRE 752 160 752 128 WIRE 384 176 384 128 WIRE 416 176 384 176 WIRE 512 176 512 128 WIRE 512 176 480 176 WIRE 512 192 512 176 WIRE 112 240 112 224 WIRE 320 240 320 224 WIRE -144 256 -144 240 WIRE 752 256 752 224 WIRE 800 256 800 224 WIRE 512 272 512 256 WIRE 272 320 208 320 WIRE 208 352 208 320 WIRE 320 352 320 336 WIRE 208 448 208 432 FLAG -144 256 0 FLAG 752 256 0 FLAG 800 256 0 FLAG 112 240 0 FLAG 512 272 0 FLAG 320 352 0 FLAG 208 448 0 SYMBOL voltage -144 144 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 9 SYMBOL nmos 160 80 M90 WINDOW 3 -37 42 VLeft 2 SYMATTR Value BSB015N04NX3 SYMATTR InstName M1 SYMBOL res 112 112 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 1m SYMBOL voltage 224 16 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 99 41 VBottom 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value PULSE(0 10 0 100n 100n 3u 5u) SYMBOL schottky 528 256 R180 WINDOW 0 24 64 Left 2 WINDOW 3 -33 -39 Left 2 SYMATTR InstName D1 SYMATTR Value MBR745 SYMATTR Description Diode SYMATTR Type diode SYMBOL nmos 480 80 R90 WINDOW 3 -42 -127 VRight 2 WINDOW 0 -17 -31 Left 2 SYMATTR Value BSB015N04NX3 SYMATTR InstName M2 SYMBOL voltage 416 16 R90 WINDOW 0 -32 56 VBottom 2 WINDOW 3 32 56 VTop 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V3 SYMATTR Value 0 SYMBOL ind2 336 240 R180 WINDOW 0 36 80 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName L1
SYMATTR Type ind SYMBOL cap 736 160 R0 SYMATTR InstName C1
SYMBOL res 784 128 R0 SYMATTR InstName R2 SYMATTR Value 3 SYMBOL cap 96 160 R0 SYMATTR InstName C2
SYMBOL cap 480 160 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C3
SYMBOL ind2 624 144 M270 WINDOW 0 32 56 VTop 2 WINDOW 3 4 56 VBottom 2 SYMATTR InstName L2
SYMATTR Type ind SYMBOL ind -144 144 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L3
SYMBOL nmos 272 240 R0 WINDOW 3 -37 42 VLeft 2 SYMATTR Value BSB015N04NX3 SYMATTR InstName M3 SYMBOL voltage 208 336 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V4 SYMATTR Value 10 TEXT 40 352 Left 2 !.tran 3m TEXT 40 376 Left 2 !K L1 L2 0.99