Working on a gadget that uses a 12 volt motor (10 amp peak) and misc electr onics running on lower voltages. It is powered from an external PSU like a laptop supply, but 12 volts. There is also a sealed lead acid battery for backup when the power fails.
This design uses pairs of pFETs to route the power from the 12 volts input when present, or the battery when the line is not present. There is also a means of shutting down all power.
Initially when designing this there was a problem with shoot through from t he battery at a slightly higher voltage than the line power initially. The n I added the capacitors present on the motor circuit which helped. But th at made large surge currents in the capacitors when the power is shut on or off.
I'm hoping someone can make some suggestions. I've run out of ideas on how the time the turn on of one switch and turn off of the other while also br inging up the power slowly to reduce the inrush of the capacitors.
Here is the LTspice schematics. I didn't use anything not in the LTspice l ibrary.
Thanks,
Rick
Version 4 SHEET 1 1752 916 WIRE 288 -608 272 -608 WIRE -608 -576 -672 -576 WIRE -352 -576 -608 -576 WIRE -96 -576 -352 -576 WIRE 32 -576 0 -576 WIRE 64 -576 32 -576 WIRE 96 -576 64 -576 WIRE 240 -576 192 -576 WIRE 272 -576 272 -608 WIRE 272 -576 240 -576 WIRE 336 -576 272 -576 WIRE 416 -576 336 -576 WIRE 544 -576 512 -576 WIRE 576 -576 544 -576 WIRE 608 -576 576 -576 WIRE 816 -576 704 -576 WIRE 32 -544 32 -576 WIRE 240 -544 240 -576 WIRE 336 -544 336 -576 WIRE 544 -544 544 -576 WIRE 816 -512 800 -512 WIRE -688 -496 -704 -496 WIRE 800 -480 800 -512 WIRE -704 -464 -704 -496 WIRE 240 -464 240 -480 WIRE 336 -464 336 -480 WIRE -608 -432 -608 -576 WIRE -352 -432 -352 -576 WIRE -80 -432 -96 -432 WIRE -16 -432 -16 -528 WIRE -16 -432 -80 -432 WIRE 16 -432 -16 -432 WIRE 32 -432 32 -464 WIRE 32 -432 16 -432 WIRE 112 -432 112 -528 WIRE 112 -432 32 -432 WIRE 432 -432 416 -432 WIRE 496 -432 496 -528 WIRE 496 -432 432 -432 WIRE 544 -432 544 -464 WIRE 544 -432 496 -432 WIRE 624 -432 624 -528 WIRE 624 -432 544 -432 WIRE 416 -400 416 -432 WIRE 592 -384 576 -384 WIRE 720 -384 704 -384 WIRE 800 -384 800 -400 WIRE -704 -368 -704 -384 WIRE 16 -368 16 -432 WIRE 592 -352 592 -384 WIRE 720 -352 720 -384 WIRE 416 -288 416 -320 WIRE 464 -288 416 -288 WIRE 480 -288 464 -288 WIRE -608 -272 -608 -352 WIRE -512 -272 -608 -272 WIRE -352 -272 -352 -352 WIRE -352 -272 -432 -272 WIRE -304 -272 -352 -272 WIRE -256 -272 -304 -272 WIRE -224 -272 -256 -272 WIRE -80 -272 -144 -272 WIRE 16 -272 16 -288 WIRE 64 -272 16 -272 WIRE 80 -272 64 -272 WIRE 16 -256 16 -272 WIRE 416 -256 416 -288 WIRE 592 -256 592 -288 WIRE 720 -256 720 -288 WIRE 720 -256 592 -256 WIRE 736 -256 720 -256 WIRE -352 -240 -352 -272 WIRE -256 -240 -256 -272 WIRE 656 -192 608 -192 WIRE -80 -176 -80 -272 WIRE -32 -176 -80 -176 WIRE 224 -176 192 -176 WIRE 368 -176 224 -176 WIRE 608 -176 608 -192 WIRE -432 -144 -464 -144 WIRE -352 -144 -352 -160 WIRE -80 -144 -80 -176 WIRE -432 -128 -432 -144 WIRE -464 -112 -464 -144 WIRE 224 -112 224 -176 WIRE 256 -112 224 -112 WIRE 368 -112 336 -112 WIRE -608 -96 -608 -272 WIRE -560 -96 -608 -96 WIRE -496 -96 -560 -96 WIRE 368 -96 368 -112 WIRE 496 -96 480 -96 WIRE 560 -96 496 -96 WIRE -320 -80 -432 -80 WIRE -256 -80 -256 -160 WIRE -256 -80 -320 -80 WIRE -608 -64 -608 -96 WIRE -496 -64 -544 -64 WIRE -80 -64 -80 -80 WIRE 608 -64 608 -80 WIRE 16 -48 16 -160 WIRE 112 -48 16 -48 WIRE 368 -48 112 -48 WIRE 416 -48 416 -160 WIRE 416 -48 368 -48 WIRE -464 0 -464 -48 WIRE -400 0 -464 0 WIRE -352 0 -400 0 WIRE -240 0 -288 0 WIRE -224 0 -240 0 WIRE 368 0 368 -48 WIRE 32 16 -32 16 WIRE 144 16 112 16 WIRE 688 16 656 16 WIRE 848 16 768 16 WIRE -608 32 -608 16 WIRE 848 32 848 16 WIRE -128 48 -176 48 WIRE -96 48 -128 48 WIRE -32 48 -32 16 WIRE -176 64 -176 48 WIRE -96 64 -96 48 WIRE -80 64 -96 64 WIRE 480 80 416 80 WIRE 544 80 480 80 WIRE 560 80 544 80 WIRE -544 96 -544 -64 WIRE -512 96 -544 96 WIRE -400 96 -432 96 WIRE -80 112 -96 112 WIRE -96 128 -96 112 WIRE 848 128 848 112 WIRE 224 144 208 144 WIRE 336 144 304 144 WIRE 368 144 368 96 WIRE 368 144 336 144 WIRE 432 144 416 144 WIRE 544 144 544 80 WIRE 544 144 496 144 WIRE -176 160 -176 144 WIRE -32 160 -32 128 WIRE 208 160 208 144 WIRE 416 160 416 144 FLAG -432 -128 0 FLAG -608 32 0 FLAG -672 -576 Vin IOPIN -672 -576 In FLAG -560 -96 Vth FLAG 432 -432 VbatOn_n FLAG -80 -432 VinOn_n FLAG 288 -608 V_main IOPIN 288 -608 Out FLAG 64 -576 VinSS FLAG 576 -576 VbatSS FLAG 816 -576 Vbatt IOPIN 816 -576 In FLAG -704 -368 0 FLAG -688 -496 Vin IOPIN -688 -496 In FLAG 800 -384 0 FLAG 816 -512 Vbatt IOPIN 816 -512 Out FLAG -400 96 Vref IOPIN -400 96 In FLAG -240 0 Vin FLAG -32 160 0 FLAG 144 16 V_main IOPIN 144 16 In FLAG -304 -272 VinOn FLAG 656 -192 PwrFail_n IOPIN 656 -192 Out FLAG 464 -288 Vbatdrv FLAG 64 -272 Vindrv FLAG 208 160 0 FLAG 480 80 PwrOn_g FLAG 112 -48 SoftStart FLAG 704 -384 Vbatt IOPIN 704 -384 In FLAG 576 -384 Vin IOPIN 576 -384 In FLAG 736 -256 V12_always IOPIN 736 -256 Out FLAG 560 80 PwrOn IOPIN 560 80 In FLAG 240 -464 0 FLAG 336 -464 0 FLAG 656 16 PwrOn IOPIN 656 16 Out FLAG 848 128 0 FLAG 416 160 0 FLAG 192 -176 Vref IOPIN 192 -176 Out FLAG 336 144 Vreg FLAG 608 -64 0 FLAG -80 -64 0 FLAG 368 -96 0 FLAG -320 -80 Vcmp FLAG -400 0 U1pwr FLAG -544 -64 V4Ref FLAG 496 -96 Vcmp FLAG 848 16 PwrOnDrv FLAG -352 -144 0 FLAG -80 -272 Vinon_g FLAG -176 160 0 FLAG -128 48 LoadOn FLAG -96 128 0 FLAG -32 16 LdGnd SYMBOL nmos 368 -256 R0 SYMATTR InstName M7 SYMATTR Value 2N7002 SYMBOL res -624 -80 R0 WINDOW 0 -11 40 Right 2 WINDOW 3 -11 65 Right 2 SYMATTR InstName R7 SYMATTR Value 27K SYMBOL res -624 -448 R0 SYMATTR InstName R8 SYMATTR Value 47K SYMBOL res -368 -448 R0 SYMATTR InstName R10 SYMATTR Value 10K SYMBOL res 16 -560 R0 SYMATTR InstName R11 SYMATTR Value 2K SYMBOL res -416 -288 R90 WINDOW 0 2 93 VBottom 2 WINDOW 3 1 29 VBottom 2 SYMATTR InstName R12 SYMATTR Value 330K SYMBOL voltage 800 -496 R0 WINDOW 123 0 0 Left 0 WINDOW 39 10 98 Left 2 WINDOW 3 -324 -53 Invisible 2 SYMATTR SpiceLine Rser=0.1 SYMATTR Value PULSE(10 13 0.1s 0.1s 0.3s 0.45s) SYMATTR InstName Batt SYMBOL voltage -704 -480 R0 WINDOW 123 0 0 Left 0 WINDOW 39 -20 -49 Left 2 WINDOW 3 -8 153 Invisible 2 SYMATTR SpiceLine Rser=0.05 SYMATTR Value PULSE(0 12.5 0.2s 0.1s 0.1s 0.3s) SYMATTR InstName In SYMBOL res 128 0 R90 WINDOW 0 48 45 VLeft 2 WINDOW 3 48 67 VRight 2 SYMATTR InstName LOAD SYMATTR Value 2 SYMBOL res 400 -416 R0 SYMATTR InstName R14 SYMATTR Value 47 SYMBOL res 528 -560 R0 SYMATTR InstName R16 SYMATTR Value 2K SYMBOL res 0 -384 R0 WINDOW 3 35 66 Left 2 SYMATTR InstName R15 SYMATTR Value 47 SYMBOL schottky 704 -352 R0 SYMATTR InstName D1 SYMATTR Value MBRS140 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 576 -352 R0 SYMATTR InstName D2 SYMATTR Value MBRS140 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky -288 -16 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D3 SYMATTR Value MBRS140 SYMATTR Description Diode SYMATTR Type diode SYMBOL res -416 80 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 1Meg SYMBOL res 784 0 R90 WINDOW 0 -12 72 VRight 2 WINDOW 3 -12 57 VLeft 2 SYMATTR InstName R2 SYMATTR Value 1Meg SYMBOL pmos -96 -528 R270 WINDOW 0 88 16 VRight 2 WINDOW 3 65 -18 VRight 2 SYMATTR InstName M1 SYMATTR Value AOD4185 SYMBOL pmos 192 -528 M270 WINDOW 0 87 62 VLeft 2 WINDOW 3 66 75 VLeft 2 SYMATTR InstName M2 SYMATTR Value AOD4185 SYMBOL pmos 416 -528 R270 WINDOW 0 88 38 VRight 2 WINDOW 3 65 -21 VRight 2 SYMATTR InstName M3 SYMATTR Value AOD4185 SYMBOL pmos 704 -528 M270 WINDOW 0 83 66 VLeft 2 WINDOW 3 63 74 VLeft 2 SYMATTR InstName M4 SYMATTR Value AOD4185 SYMBOL nmos -32 -256 R0 SYMATTR InstName M5 SYMATTR Value 2N7002 SYMBOL nmos 416 0 M0 WINDOW 0 62 34 Left 2 WINDOW 3 61 8 Left 2 SYMATTR InstName M8 SYMATTR Value 2N7002 SYMBOL Comparators\\LTC1841 -464 -80 M180 WINDOW 0 -10 49 Right 2 WINDOW 3 28 -15 Left 2 SYMATTR InstName U1 SYMBOL polcap 224 -544 R0 WINDOW 3 24 56 Left 2
SYMATTR InstName C1 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=35 Irms=1.95 Rser=0.03 Lser=0 mfg="Panasonic" pn="ECA1VFQ102L" type="Al electrolytic" SYMBOL polcap 320 -544 R0 WINDOW 3 24 56 Left 2
SYMATTR InstName C2 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=35 Irms=1.95 Rser=0.03 Lser=0 mfg="Panasonic" pn="ECA1VFQ102L" type="Al electrolytic" SYMBOL voltage 848 16 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 WINDOW 3 -16 101 Invisible 2 WINDOW 0 -25 84 Right 2 SYMATTR Value PULSE(3.3V 0V 0.4S 1us 1us 99.998ms 0.5s) SYMATTR InstName PwrOn SYMBOL cap 496 128 R90 WINDOW 0 -11 41 VRight 2 WINDOW 3 -12 29 VLeft 2 SYMATTR InstName C3 SYMATTR Value 22nF SYMBOL res 320 128 R90 WINDOW 0 -13 75 VRight 2 WINDOW 3 -13 56 VLeft 2 SYMATTR InstName R3 SYMATTR Value 330 SYMBOL nmos 560 -176 R0 SYMATTR InstName M9 SYMATTR Value 2N7002 SYMBOL res -272 -256 R0 SYMATTR InstName R4 SYMATTR Value 3.6K SYMBOL cap -96 -144 R0 SYMATTR InstName C5 SYMATTR Value 150nF SYMBOL voltage 240 -112 R270 WINDOW 123 0 0 Left 0 WINDOW 39 -20 -49 Left 2 WINDOW 3 37 76 VRight 2 WINDOW 0 37 38 VLeft 2 SYMATTR Value 4V SYMATTR InstName Vref SYMBOL res -368 -256 R0 SYMATTR InstName R5 SYMATTR Value 10K SYMBOL res -128 -288 R90 WINDOW 0 -12 72 VRight 2 WINDOW 3 -12 57 VLeft 2 SYMATTR InstName R6 SYMATTR Value 100K SYMBOL voltage -176 48 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 WINDOW 3 -16 101 Invisible 2 WINDOW 0 -25 84 Right 2 SYMATTR Value PWL(0 -1 50ms -1 50.001ms 1 370ms 1 370.001ms -1 550ms -1 550 .001ms 1 950ms 1 950.001ms -1) SYMATTR InstName LoadOn SYMBOL sw -32 144 M180 WINDOW 3 12 96 Left 2 SYMATTR InstName S1 TEXT 160 -384 Left 3 !.tran 1sec TEXT -552 -544 Left 2 ;Nominal range\n11.4 < Vin < 12.6 TEXT -600 -224 Left 2 ;11.2V rising,\n10.6V falling TEXT 656 -160 Left 3 ;To Control Board TEXT 560 160 Left 3 ;From Control Board TEXT -664 -608 Left 2 !.model SW sw(Ron=0.001 Roff=10Meg vt=0.5)