Sulzer regulators are well known and proved their efficiency over the years. Schematic offered here is slightly modified two-polarity Sulzer regulator which has some improvements over original one:
1. Active regulation elements (opamps U1 and U2) are supplied by capacitive multipliers Q1, R3, C5 and Q2, R4, C6 for negative rail respectively.
2. Reference voltage sources (Zener diodes D10 and D11 resp.) are fed by constant current sources (Q5, R13 and Q6, R16 resp.) which ensures constant currents via D10, D11 and hence their constant working points.
3. Reference voltage sources are placed on the right (stabilized) sides of the stabilizers which ensures much more lower noise over them.
4. Diodes D9, D12 ensure normal start of the two rails no matter what load is connected.
That schematic has very good capabilities (both simulated and measured) for ripple and noise suppression.
PCB for the schematic is with dimensions 163×70 mm.
PCB thickness: FR4 1.55 mm. Copper thickness: 35um (1oz). Surface finish – Nickel Gold (ENIG).
It is one-layer design with solder mask coating on bottom layer for best durability. Silk screen with parts layout is placed on the top of the PCB.
PCB has following abilities:
– 3 different types of power transformers can be mounted on it – 15 or 25 VA series of Talema’s PCB mounting toroidal transformers, PL20-XX-130B series of Tamura and standard toroidal transformers with outer diameter not larger than 70 mm.
– When power transformers with two primary windings are used, ability for choosing the input AC voltage 230/115 V is provided on PCB.
– Places for main filter capacitors with different sizes – radial leaded with lead spacing 5 or 7.5mm and outer diameter 18 mm. max.
– Places for rectifier diodes with different cases – DO41, SOD-57, DO-201.
– Bleeder resistors R1, R2 and output resistors R7, R8 can be RM10 or RM15 lead spacing (depending on their desired power rating).
– In case of higher output voltages series resistors R14, R16 ensure safety voltage drop over JFETs.
– Output MOLEX connector has two terminals for positive, negative and ground outputs (if multiple consumers are to be attached to regulator).
– different types of heatsinks can be mounted on PCB.
All parts used are easily obtainable from big supplier stores (Mouser, Farnell, Digi-Key etc.) or via e-bay.
On the pictures you can see measured results at output voltage 15V, 40 Ohm load (375 mA load current) with some easily obtainable OPAmps (NE5534, OP37) that has been taken in order to verify schematic’s capabilities.
For the tests was used a 35VA toroidal transformer with two secondary windings, capacitors after bridge rectifiers – 2200 uF Nippon ChemiCon KZE, all other parts – standard inexpensive; souncard used – E-MU 0404.
Note that even with good old NE5534 (cheap nowadays), schematic and PCB show very well results.
Of course, they can be even better if larger rectifier capacitors are used or parts are with better noise characteristics.
And finally – as a reference, the measurements of a regulator with LM317 were taken. All other parts (transformer, rectifier diodes, filter capacitor, load resistors) are the same. On the picture you can see spectrum of LM317 (TO220 body) loaded with 120 Ohm resistive load (approx. 140 mA consumption current).
Schematic and parts list will be sent to the buyer’s PayPal address after purchase. If for some reason a different e-mail address must be used, note it in the process of checkout.
What the buyer will receive:
The package will contain 1 pcs. PCB for modified Sulzer regulator – v.2.
The unit will be shipped with Priority AirMail Registered (or equivalent courier service where applicable). The tracking number will be sent to the customer after shipment.