self-energized synchronous rectifer circuit?

S

starfire

Guest
Hi all -

I've been reading a little about synchronous rectifiers as used in a
switching power supply. I've also seen some references to a
"self-energized" version of the synchronous rectifier which could be used in
small signal rectification applications.

Has anyone seen a complete schematic for a self-energized syunchrnous
rectifier circuit?

I've tried Google but most are references to "FreePatent", "IEEE", and
"PatentStorm"...

Thanks

Dave
 
"starfire" <starfire151@cableone.net> wrote in message
news:0tidnS2-T5SOEevVnZ2dnUVZ_g2dnZ2d@supernews.com...
Hi all -

I've been reading a little about synchronous rectifiers as used in a
switching power supply. I've also seen some references to a
"self-energized" version of the synchronous rectifier which could be used
in small signal rectification applications.

Has anyone seen a complete schematic for a self-energized syunchrnous
rectifier circuit?

I've tried Google but most are references to "FreePatent", "IEEE", and
"PatentStorm"...
Click to expand...
I found this using www.dogpile.com:

http://scholar.lib.vt.edu/theses/available/etd-173510281975580/unrestricted/chapter2.pdf

I made a simulation of a sort of a synchronous rectifier which uses
transistors to lower the forward voltage drop for a low voltage supply, in
this case down to 260 mV maximum at 600 mA. It could probably be done just
as well with Schottkys, but I wonder if this concept is viable for some
applications. This is for a FWCT DC supply, not a switching regulator. I
got efficiency of 83% for a 1.8 VDC output at 217 mW, for example. This
would not be possible for MOSFETs because of the body diode, but it should
work as shown with BJTs up to about 6 v P-P. LTSpice file follows.

Paul

====================================================================

Version 4
SHEET 1 880 680
WIRE 144 -160 -48 -160
WIRE 192 -160 144 -160
WIRE 400 -160 288 -160
WIRE 512 -160 400 -160
WIRE 608 -160 512 -160
WIRE 144 -80 144 -160
WIRE -144 -64 -288 -64
WIRE -288 -32 -288 -64
WIRE -144 -32 -144 -64
WIRE -48 16 -48 -80
WIRE 32 16 -48 16
WIRE 144 32 144 0
WIRE 176 32 144 32
WIRE 144 64 144 32
WIRE -288 80 -288 48
WIRE -144 80 -144 48
WIRE -144 80 -288 80
WIRE -48 96 -48 16
WIRE 32 128 32 16
WIRE 144 128 32 128
WIRE 240 128 240 80
WIRE 240 128 144 128
WIRE 144 176 -48 176
WIRE 192 176 144 176
WIRE 400 176 400 -160
WIRE 400 176 288 176
WIRE 144 240 144 176
WIRE 144 368 144 320
WIRE 176 368 144 368
WIRE 144 416 144 368
WIRE 32 480 32 128
WIRE 144 480 32 480
WIRE 240 480 240 416
WIRE 240 480 144 480
FLAG -288 80 0
FLAG 32 480 0
FLAG 608 -80 0
FLAG 512 -96 0
SYMBOL ind2 -32 -176 M0
SYMATTR InstName L1
SYMATTR Value 50m
SYMATTR Type ind
SYMBOL ind2 -32 80 M0
SYMATTR InstName L2
SYMATTR Value 50m
SYMATTR Type ind
SYMBOL pnp 288 -96 M270
WINDOW 0 48 34 Left 0
WINDOW 3 45 65 Left 0
SYMATTR InstName Q1
SYMATTR Value 2N3906
SYMBOL pnp 288 240 M270
WINDOW 0 50 32 Left 0
WINDOW 3 45 65 Left 0
SYMATTR InstName Q2
SYMATTR Value 2N3906
SYMBOL npn 176 -16 R0
SYMATTR InstName Q3
SYMATTR Value 2N3904
SYMBOL npn 176 320 R0
SYMATTR InstName Q4
SYMATTR Value 2N3904
SYMBOL res 224 -112 R0
SYMATTR InstName R1
SYMATTR Value 100
SYMBOL res 224 224 R0
SYMATTR InstName R2
SYMATTR Value 100
SYMBOL res 128 -96 R0
SYMATTR InstName R3
SYMATTR Value 5k
SYMBOL res 128 224 R0
SYMATTR InstName R4
SYMATTR Value 5k
SYMBOL diode 160 128 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL diode 160 480 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D2
SYMATTR Value 1N4148
SYMBOL ind2 -160 -48 R0
SYMATTR InstName L3
SYMATTR Value 100m
SYMATTR Type ind
SYMBOL voltage -288 -48 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 132 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 3 60 0 0 0 100)
SYMATTR SpiceLine Rser=.1
SYMBOL cap 496 -160 R0
SYMATTR InstName C1
SYMATTR Value 4700ľ
SYMBOL res 592 -176 R0
SYMATTR InstName R5
SYMATTR Value 15
TEXT -144 240 Left 0 !K1 L1 L2 L3 1
TEXT -322 504 Left 0 !.tran 1 startup
 
"Paul E. Schoen" <pstech@smart.net> wrote in message
news:4876ffb9$0$25545$ecde5a14@news.coretel.net...
"starfire" <starfire151@cableone.net> wrote in message
news:0tidnS2-T5SOEevVnZ2dnUVZ_g2dnZ2d@supernews.com...
Hi all -

I've been reading a little about synchronous rectifiers as used in a
switching power supply. I've also seen some references to a
"self-energized" version of the synchronous rectifier which could be used
in small signal rectification applications.

Has anyone seen a complete schematic for a self-energized syunchrnous
rectifier circuit?

I've tried Google but most are references to "FreePatent", "IEEE", and
"PatentStorm"...

I found this using www.dogpile.com:

http://scholar.lib.vt.edu/theses/available/etd-173510281975580/unrestricted/chapter2.pdf

I made a simulation of a sort of a synchronous rectifier which uses
transistors to lower the forward voltage drop for a low voltage supply, in
this case down to 260 mV maximum at 600 mA. It could probably be done just
as well with Schottkys, but I wonder if this concept is viable for some
applications. This is for a FWCT DC supply, not a switching regulator. I
got efficiency of 83% for a 1.8 VDC output at 217 mW, for example. This
would not be possible for MOSFETs because of the body diode, but it should
work as shown with BJTs up to about 6 v P-P. LTSpice file follows.

Paul

====================================================================

Version 4
SHEET 1 880 680
WIRE 144 -160 -48 -160
WIRE 192 -160 144 -160
WIRE 400 -160 288 -160
WIRE 512 -160 400 -160
WIRE 608 -160 512 -160
WIRE 144 -80 144 -160
WIRE -144 -64 -288 -64
WIRE -288 -32 -288 -64
WIRE -144 -32 -144 -64
WIRE -48 16 -48 -80
WIRE 32 16 -48 16
WIRE 144 32 144 0
WIRE 176 32 144 32
WIRE 144 64 144 32
WIRE -288 80 -288 48
WIRE -144 80 -144 48
WIRE -144 80 -288 80
WIRE -48 96 -48 16
WIRE 32 128 32 16
WIRE 144 128 32 128
WIRE 240 128 240 80
WIRE 240 128 144 128
WIRE 144 176 -48 176
WIRE 192 176 144 176
WIRE 400 176 400 -160
WIRE 400 176 288 176
WIRE 144 240 144 176
WIRE 144 368 144 320
WIRE 176 368 144 368
WIRE 144 416 144 368
WIRE 32 480 32 128
WIRE 144 480 32 480
WIRE 240 480 240 416
WIRE 240 480 144 480
FLAG -288 80 0
FLAG 32 480 0
FLAG 608 -80 0
FLAG 512 -96 0
SYMBOL ind2 -32 -176 M0
SYMATTR InstName L1
SYMATTR Value 50m
SYMATTR Type ind
SYMBOL ind2 -32 80 M0
SYMATTR InstName L2
SYMATTR Value 50m
SYMATTR Type ind
SYMBOL pnp 288 -96 M270
WINDOW 0 48 34 Left 0
WINDOW 3 45 65 Left 0
SYMATTR InstName Q1
SYMATTR Value 2N3906
SYMBOL pnp 288 240 M270
WINDOW 0 50 32 Left 0
WINDOW 3 45 65 Left 0
SYMATTR InstName Q2
SYMATTR Value 2N3906
SYMBOL npn 176 -16 R0
SYMATTR InstName Q3
SYMATTR Value 2N3904
SYMBOL npn 176 320 R0
SYMATTR InstName Q4
SYMATTR Value 2N3904
SYMBOL res 224 -112 R0
SYMATTR InstName R1
SYMATTR Value 100
SYMBOL res 224 224 R0
SYMATTR InstName R2
SYMATTR Value 100
SYMBOL res 128 -96 R0
SYMATTR InstName R3
SYMATTR Value 5k
SYMBOL res 128 224 R0
SYMATTR InstName R4
SYMATTR Value 5k
SYMBOL diode 160 128 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL diode 160 480 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D2
SYMATTR Value 1N4148
SYMBOL ind2 -160 -48 R0
SYMATTR InstName L3
SYMATTR Value 100m
SYMATTR Type ind
SYMBOL voltage -288 -48 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 132 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 3 60 0 0 0 100)
SYMATTR SpiceLine Rser=.1
SYMBOL cap 496 -160 R0
SYMATTR InstName C1
SYMATTR Value 4700ľ
SYMBOL res 592 -176 R0
SYMATTR InstName R5
SYMATTR Value 15
TEXT -144 240 Left 0 !K1 L1 L2 L3 1
TEXT -322 504 Left 0 !.tran 1 startup


Thanks very much, Paul.
Click to expand...

I'll take a look at it. It looks very promising, although I was hoping to
do this without a transformer. This is for an application within a strong
magnetic field and the transformer may be affected or affect the system
operation. This principles look good, though.

Dave
 
"starfire" <starfire151@cableone.net> wrote in message
news:K4qdncAebv1HPurVnZ2dnUVZ_rrinZ2d@supernews.com...
Thanks very much, Paul.

I'll take a look at it. It looks very promising, although I was hoping
to do this without a transformer. This is for an application within a
strong magnetic field and the transformer may be affected or affect the
system operation. This principles look good, though.

Dave
Click to expand...
The transformer is not really necessary for operation. You could use half
of the circuit if half wave is OK. Your choice of design depends on what
you are trying to do. Good luck.

Paul
 
Paul E. Schoen wrote:

The transformer is not really necessary for operation. You could use half
of the circuit if half wave is OK. Your choice of design depends on what
you are trying to do. Good luck.
Click to expand...
I'm not sure what its upper frequency limit is, but an air
core transformer might be a possibility, especially if
resonated with capacitance.

--
Regards,

John Popelish
 
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