Description
The Elektor Low-Noise Lab Power Supply is a fully analogue, adjustable, medium-power symmetrical bench supply that contains no switching or digital components. It provides an output voltage adjustable between 0 V and ±22 V, and an output current adjustable from 0 A to 1 A. Because it avoids any form of switching circuitry, the design delivers extremely low noise. To display both output voltages and currents, four miniature moving-coil panel meters are used.
Most modern laboratory power supplies and AC adapters employ switch-mode techniques. Even the best examples inevitably exhibit high-frequency ripple and other switching artefacts on their output, which can interfere with the testing of sensitive analogue circuits and disturb low-level measurements. To overcome this, the concept here is a completely analogue power supply. Although less efficient than its switch-mode counterparts, the reduced efficiency is of little importance for test-bench use and ensures cleaner, more reliable measurement results.
Because many analogue circuits require a symmetrical supply, this design delivers positive and negative output voltages of equal magnitude. A small amount of adjustment is available to compensate for any imbalance. Naturally, a variable current-limit function is also included.
Specifications
| Output Voltage |
0…+22 V, 0, −22 V |
| Output Current |
0…+1 A, 0…−1 A |
| Noise |
−85 dBV, (at 0.95 A/20 V, B = 22 kHz) |
| −84 dBV (at 0.95 A/20 V, B > 500 kHz) |
| Ripple |
50 µVRMS (at 950 mA/20 V, B = 22 kHz, mainly 100 Hz component) |
Included
- 3x PCBs: Regulator (PCB-1), Mains Filter (PCB-2) and Transformer (PCB-3)
- All the components except the AC transformers
- 4x moving-coil meters
- Additional parts for wiring (wires, banana sockets, IEC Power entry module, etc.)
Not included
- The three AC transformers
- An enclosure
Parts List
For the Regulator PCB (240386-1)
Resistors (250 mW, 1%)
- R1 = 12 Ω
- R2, R8, R37, R62 = 1 MΩ
- R3, R7, R10, R13, R17, R20, R22, R30, R35, R42, R45, R47, R55, R60 = 100 Ω, 600 mW
- R4, R5 = 4.7 kΩ
- R6 = 100 kΩ
- R9, R12, R14, R36, R38, R39, R61, R63, R66, R72, R78, R79 = 10.0 kΩ, 600 mW
- R11 = 9.76 kΩ, 600 mW
- R15, R40 = 44.2 kΩ, 600 mW
- R16, R41, R77 = 1 kΩ
- R18, R43 = 1.5 kΩ, 1 W, 5%
- R19, R44 = 470 Ω, 1 W, 5%
- R21, R46 = 330 Ω, 600 mW
- R23, R24, R48, R49 = 1.0 Ω, 1 W
- R25, R50 = 1 kΩ, 1 W, 5%
- R26, R28, R51, R53 = 1.000 kΩ 0.1%, 15 ppm/C
- R27, R29, R52, R54 = 10.00 kΩ 0.1%, 15 ppm/C
- R31, R56 = 1.2 kΩ, 1 W, 5%
- R32, R57 = 47 kΩ
- R33, R58 = 270 Ω
- R34, R59 = 27 kΩ
- R64, R69 = 12.0 kΩ
- R65 = 3.0 kΩ, 600 mW
- R67, R80 = 470 Ω, 600 mW
- R68, R70 = 6.8 kΩ, 600 mW
- R71 = 30.0 kΩ,, 600 mW
- R73, R74, R75, R76 = 10 MΩ
- P1, P2, P3 = 10 kΩ, 200 mW, 20%, potentiometer, 1 turns, single, lin., panel mount
- P4, P5 = 500 Ω, 500 mW, 10%, trimmer, 25 turns, 3296Y-1-501LF Bourns
- P6, P7 = 10 kΩ, 500 mW, 10%, trimmer, 25 turns, 3296Y-1-501LF Bourns
Capacitors
- C1 = 100 nF, 50 V, 10%, ceramic X7R, LS 5 mm
- C2, C3, C6, C7, C30 = 10 µF, 63V, 20%, LS 2.5 mm, 3000hours@105°C
- C4, C5, C8, C9, C13, C14, C18, C19, C23, C24, C28, C29, C31, C32, C38, C39 = 100 nF, 250 V, 10%, PET, LS 7.5 mm
- C10, C20 = 47 nF, 100 V, 5%, PET, LS 5 mm
- C11, C21 = 10 nF, 100 V, 5%, PET, LS 5 mm
- C12, C22 = 220 µF, 35 V, 20%, 0.024 Ω, LS2.5/3.5 mm, Ir 3.4 A, 2000hours@125°C, polymer
- C15, C25 = 120 µF, 50 V, 20%, ESR 0.02 Ω, Diam. 10 mm max., LS 5 mm
- C16, C26 = 15 nF, 100 V, 5%, PET, LS 5 mm
- C17, C27 = 47 nF, 100 V, 5%, PET, LS 5 mm
- C33, C34 = 22 µF, 50 V, 20%, LS 2 mm, 10000 hours @ 105°C
- C35, C36, C44, C45 = 1 µF, 100 V, 10%, LS 5 mm, ceramic X7R
- C37 = 100 uF, 50 V, 20%. LS 3.5 mm
- C40, C41, C42, C43, C46, C47, C48, C49 = 1000 µF, 50 V, 20%, LS 5/7.5 mm, Ir 3.32 A, 10000hours@105°C, D 16 mm
- C50, C51, C52, C53 = 47 nF, 100 V, 10%, ceramic X7R, LS 5 mm
Inductors
- L1, L2 = 4.7 µH, 3.2 A, 0.033 Ω, LS 5 mm, RLB0914-4R7ML Bourns
- L3 = Commom mode choke, 14.5 mH, 3 A, SSRH24NH-30145 Kemet
Semiconductors
- D1, D2, D3, D4, D5, D9, D10, D11, D15 = BAT85, DO-34
- D6, D7, D12, D13 = SR560, DO-201AD
- D8, D14, D16 = 1N4148, DO-35
- D17 = Zenerdiode, 5.6 V, 0.5 W, DO-41
- D18, D19 = 1N4004, DO-41
- D20, D21 D22, D23 = V30100CI-M3/P, dual common cathode, TO-220
- D24 = Zener diode, 30 V, 1 W, DO-41
- LED1, LED2 = LED, red, T-1 (3 mm)
- LED3, LED4 = LED, green, T-1 (3 mm)
- TVS1, TVS2 = BZW50-33B, R6
- T1, T2, T4 = BC337.25, TO-92
- T3 = NJW0302G, TO-3P
- T5, T6, T8 = BC327.25, TO-92
- T7 = NJW0281G, TO-3P
- T9 = BD139, TO-126 (SOT-32)
- IC1 = LM334Z, TO-92
- IC2 = LM4040AIZ-5.0/NOPB, TO-92 (TO-226AA-3)
- IC3, IC4 = OPA2992IDR, SOIC-8
- IC5, IC6 = OPA4992IDR, SOIC-14
- IC7 = OPA992IDBVR, SOT-23-5
- IC8 = LM339N, DIP-14
- IC9 = LM317, TO-220
- IC10 = LM337, TO-220
Others
- F1, F2 = 5×20 mm fuse, 1.6 A, fast acting
- HS1, HS2 = Heatsink MC33271 (for T3/T7), 2.7°C/W, PCB mount, height 63.5 mm
- K1, K4 = 3-way screw terminal block, LS 3.5 mm, max. 1.5 mm²
- K2, K3 = 3-way screw terminal block, LS 3.5 mm, max. 1 mm²
- M1, M3 = Moving coil meter, Range 30 V, type 91C4, 45×45 mm
- M2, M4 = Moving coil meter, Range 1 A, type 91C4, 45×45 mm²
- RE1 = Relay DPDT,5V, UA2-5NU
Miscellaneous
- 3× 3-way screw terminal block, LS 3.5 mm, max. 1 mm² (for P1, P2, P3)
- 4× Pin header, 1×2, vertical, pitch 2.54 mm (for LED1, LED2, LED3, LED4)
- 4× Pin socket, 1×2, vertical. pitch 2.54 mm (for LED1, LED2, LED3, LED4)
- 2× Heatsink FK222SA220, 20°C/W, PCB mount (for IC9 & IC10)
- 2× Mica thermal pad for TO-220, 12×18×0.05 mm (for IC9 & IC10)
- 2× Insulating bushing IB 6, TO-220 (for IC9 & IC10)
- 2× Ceramic thermal pad, 23×20×2 mm (for T3 & T7)
- 2× PCB Fuse Holder, for 5×20 mm fuse, 10 A (for F1, F2)
- 2× Cover for PCB Fuse Holder, transparent (for F1, F2)
- 2× 2-way screw terminal block, LS 3.5 mm, max. 1 mm² (for M1 & M3)
- 2× 2-way screw terminal block, LS 3.5 mm, max. 1.5 mm² (for M2 & M4)
- 8× M3 solder lug, thickness 0.35 mm (for M1…M4)
- M4 solder lug, thickness 0.35 mm (to connect 4 mm banana connectors)
- Screened cable, 1 pair, 2×24 AWG/0.22 mm², 1 m (for P1, P2 & P3)
- IC socket, DIP, 14 contacts (for IC8)
- M3 washer, plain, steel
- M3 screw, 16 mm, steel, pan head
- M3 nut
- M3 spring washer
- 50 mm M3 standoff, steel, male-female
- 12 mm M3 standoff, steel, male-female
- 10 mm M3 standoff, steel, male-female
- M3 screw, 8 mm, steel, pan head
For the Mains Fiter PCB (240386-2)
Resistor
- R1 = 220 kΩ, 1 W, 500 V, 5%
Capacitors
- C1, C2 = 470 nF, 305 VAC, Class X2, 11 × 27 mm max., LS 15/22.5 mm
- C3, C4, C5, C6 = 2.2 nF, 300 VAC, Class Y2, 13 × 4 mm, LS 10 mm, PP
Inductors
- L1, L2 = Common-mode choke, 6.8 mH, 1.7 A, TDK B82732R2172B030
Semiconductor
- MOV1 = TVS varistor, 300 VAC, S14K300 (230 VAC, B72214S0301K101) and SK14K150 (150 VAC, B72214S0151K101)
Others
- K1, K2 = 3-way screw terminal block, LS 7.62 mm
- F1 = Time-delay fuse, 0.5 A (230 VAC) or 1 A (115 VAC)
Miscellaneous
- 1× Fuse holder, 5×20 mm, 10 A, 500 VAC
- 1× Transparent fuse cover
- 4× 10 mm M3 standoff, steel, male–female
- 4× M3 screw, 8 mm, steel, pan head
- 4× M3 nut
For the Transformer PCB (240386-3)
Resistors
- R1, R2 = 2.7 kΩ, 600 mW, 1%
- R3 = 10.0 kΩ, 600 mW, 1%
Capacitor
- C1 = 220 µF, 50 V, 20%, Ø10 mm, LS 5 mm, 4000 h @ 105°C
Transformers (not included in this kit!)
- TR1, TR2, TR3 = 2×7 V, 25 VA, PCB-mounted toroid, 70060K Talema
Semiconductors
- D1–D4 = 1N4148, DO-35
- D5, D6 = 1N4004, DO-41
- D7 = Zener 5.6 V, 1.3 W, DO-41
- LED1 = LED, red, T-1 (3 mm)
- IC1, IC2 = MOC8021M, CTR ≥ 1000%, DIP-6
Others
- F1, F2, F3 = 160 mA time-delay fuse (230 VAC) or 315 mA time-delay fuse (115 VAC)
- K1 = 2-way screw terminal block, LS 7.62 mm
- K2 = 3-way screw terminal block, LS 3.5 mm, max 1.5 mm²
- K3, K4 = 3-way screw terminal block, LS 3.5 mm, max 1 mm²
- RE1, RE2 = Relay DPDT, 5 A/250 VAC / 24 VDC
Miscellaneaous
- 1× Pin header 1×2, pitch 2.54 mm + matching socket for LED1
- 3× Fuse holder 5 × 20 mm, 10 A, 500 VAC + transparent cover
- 3× M4 screw, 8 mm, pan head + washer for TR1-TR3
- 8× M3 screw, 8 mm, pan head + nut + washer
- 8× 10 mm M3 standoff, steel, male–female
- 2× IC socket, DIP-6 for IC1 & IC2
Additional Parts
- 1 m red insulated wire, stranded, 1.5 mm²
- 0.5 m blue insulated wire, stranded, 1.5 mm²
- 0.5 m black insulated wire, stranded, 1.5 mm², 0.5 m
- 2 m red insulated wire, stranded, D 0.56 mm (0.25 mm²)
- 2 m black insulated wire, stranded, D 0.56 mm (0.25 mm²)
- 0.5 m Multicore Cable, Flexible, 3 Core, 0.75 mm² (24 x 0.2 mm)
- Red banana socket
- Black banana socket
- Blue banana socket
- Green banana socket
- IEC Power Entry Module with switch, IEC C14
- 3 crimp terminals, FASTON, 4.75 x 0.81 mm
- 3 knobs
Links