I'm designing an interface to an HBS (HomeBus) system, which is variously known by different manufacturer's names:
Daiken: P1/P2 or F1/F2 Mitsubishi: M-Net Toshiba: TCC-Link Hitachi: H-link Panasonic/Sanyo: SIII-Net. Other manufacturers use it too, e.g. Rinnai
See Chapter 4 of the EchoNet standard here:
Anyhow, it's a single pair multi-drop network with one device feeding power at nominally 14V, with superimposed RS232-ish signalling of 2V alternate-space-inversion pulses at 9600baud. Power is typically fed through something equivalent to a 22mH inductor, with a DC resistance around 5 ohms but dynamic impedance more like 200 ohms. It can be connected in either polarity, so the first step is a bridge rectifier, but I've ignored that.
Out of this supply, I want to draw up to 100mA for a 5V circuit that has quite bursty current consumption but doesn't require a strictly regulated voltage. So a linear regulator is out, or I'll couple too much supply noise onto the line and upset the signalling. It doesn't matter how big an output capacitor would be, the linear regulator would aggressively recharge it on usage spikes.
The classic approach is to use a 22mH inductor, and that would work fine, but as in telephony, everybody uses gyrators instead. For reasons of supply headroom, I want to combine a gyrator with regulation down to nominal 5V.
The attached circuit does this ok... but I can't work out why it doesn't work better. The Sziklai pair is operating at a gain around 250,000, so should be multiplying the 10uF capacitance of C3 by something in that order.
I still see about 30mV of noise being injected into the line, and nothing I've tweaked seems to reduce that by much.
Can anyone figure out why this noise is getting into Vline, and how to fix it?
Clifford Heath
--- Chop with axe --- Version 4 SHEET 1 1608 1700 WIRE 704 -80 576 -80 WIRE -480 48 -544 48 WIRE -288 48 -480 48 WIRE -144 48 -288 48 WIRE 0 48 -48 48 WIRE 80 48 0 48 WIRE 208 48 160 48 WIRE 352 48 208 48 WIRE 544 48 352 48 WIRE 576 48 576 -80 WIRE 576 48 544 48 WIRE 608 48 576 48 WIRE -544 144 -544 48 WIRE -96 160 -96 112 WIRE 0 160 0 48 WIRE 704 272 704 -80 WIRE -288 288 -288 48 WIRE -208 288 -288 288 WIRE -48 288 -48 224 WIRE -48 288 -128 288 WIRE 32 288 -48 288 WIRE 208 288 208 48 WIRE 208 288 112 288 WIRE -544 336 -544 224 WIRE 544 336 544 48 WIRE 352 352 352 48 WIRE -48 368 -48 288 WIRE 0 368 -48 368 WIRE 208 368 208 288 WIRE 208 368 64 368 WIRE 704 416 704 336 WIRE -48 432 -48 368 WIRE -48 528 -48 512 WIRE -48 544 -48 528 WIRE -544 624 -544 416 WIRE -48 624 -48 608 WIRE 352 624 352 416 WIRE 544 624 544 416 WIRE 704 624 704 496 FLAG 544 624 0 FLAG 608 48 Vout FLAG -544 624 0 FLAG -48 624 0 FLAG 704 624 0 FLAG 352 624 0 FLAG -48 288 Vb FLAG 0 48 Vee FLAG -480 48 Vline FLAG -48 528 Vz SYMBOL res 528 320 R0 SYMATTR InstName R1 SYMATTR Value 47R SYMBOL voltage 704 400 R0 WINDOW 123 0 0 Left 2 WINDOW 39 -61 129 Left 2 WINDOW 3 -63 102 Left 2 SYMATTR SpiceLine Rser=10 SYMATTR InstName V1 SYMATTR Value PULSE(-2 2 0.001 1u 10u 50u 100u) SYMBOL res -112 272 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R5 SYMATTR Value 470k SYMBOL cap 0 384 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName C3 SYMATTR Value 10u SYMATTR SpiceLine Rser=12m Lser=10n Rpar=3e6 Cpar=3e-9 SYMBOL zener -32 608 R180 WINDOW 0 47 31 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D1 SYMATTR Value BZX84C6V2L SYMBOL res 176 32 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 3.3R SYMBOL res 128 272 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 100k SYMBOL voltage -544 320 R0 WINDOW 123 0 0 Left 2 WINDOW 39 24 118 Left 2 SYMATTR SpiceLine Rser=5R SYMATTR InstName V2 SYMATTR Value 14V SYMBOL cap 688 272 R0 SYMATTR InstName C1 SYMATTR Value 10u SYMATTR SpiceLine Rser=12m Lser=10n Rpar=3e6 Cpar=3e-9 SYMBOL cap 336 352 R0 SYMATTR InstName C2 SYMATTR Value 47u SYMATTR SpiceLine Rser=12m Lser=10n Rpar=3e6 Cpar=3e-9 SYMBOL ind -560 128 R0 SYMATTR InstName L1 SYMATTR Value 22mH SYMATTR SpiceLine Rser=0.1 SYMBOL npn -96 224 R270 WINDOW 0 -7 4 VRight 2 WINDOW 3 73 6 VRight 2 SYMATTR InstName Q2 SYMATTR Value 2N3904 SYMBOL pnp -48 112 M270 WINDOW 0 -7 86 VLeft 2 WINDOW 3 81 94 VLeft 2 SYMATTR InstName Q1 SYMATTR Value 2N5401 SYMBOL res -64 416 R0 SYMATTR InstName R2 SYMATTR Value 47k TEXT -416 624 Left 2 !.tran 60m TEXT -232 752 Left 2 ;HomeBus Gyrator/Regulator TEXT 648 664 Left 2 ;Load variation TEXT 568 432 Left 2 ;DC load TEXT -568 672 Left 2 ;HomeBus source