Article
Soft Start for PSU
Be nice to your power supply – and its load
The circuit presented here is a general-purpose soft-start accessory for both homemade and commercial power supplies.The simplest lab power supplies have an adjustable output voltage and (ideally) short-circuit protection. That’s fairly basic, but for a budding electronics enthusiast it’s an excellent way to start their career. The better models also have adjustable output current limiting, and precise indication of the output voltage and current is a feature that should be present in any respectable lab power supply.
Gerber file
CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.
Elektor recommends the Elektor PCB Service service from its business partner Eurocircuits or AISLER as the best services for its own prototypes and volume production.
The use of our Gerber files is provided under a modified Creative Commons license. Creative Commons offers authors, scientists, educators and other creatives the freedom to handle their copyright in a more free way without losing their ownership.
PCB
Component list
Component List
Resistors
R1 = 100Ohm, thick film, 5%, 0.1W, 150V
R2,R7 = 10kOhm, thick film, 5%, 0.1W, 150V
R3,R4 = 1kOhm, thick film, 5%, 0.1W, 150V
R5 = 3.6kOhm, 1%, 125mW, 150V, 0805
R6 = 240kOhm, 1%, 125mW, 150V, 0805
Capacitors
C1 = 100nF, 50V, X7R, 0805
C2 = 22µF, 10V, X5R, 20%, 1206
C3 = 1µF, 50V, 10%, X7R, 1206
C4 = 220nF, 50V, X7R, 0805
C5 = 1nF, 50V, 10%, X7R, 0603
Semiconductors
D1,D2 = 1N4148WS (100V, 200mA, 4ns)
LED1 = bicolour red/green, 3mm
T1,T2 = NVD6824NLT4G (n-channel MOSFET, 100V, 41A)
T3 = 2N7002 (60V, 250mA, 300mW, Vgs = 4.5V, RDS(on) = 1Ohm)
IC1 = MAX5024 (voltage regulator, 5V, 150mA, LDO)
IC2 = MAX16126TCA+ (voltage supervisor)
IC3 = MAX16054AZT+T (pushbutton debouncer)
K1 = 2-way PCB screw terminal block, 0.2" pitch, 630V
K2A = see text
K2B = 2-way PCB screw terminal block, 0.2" pitch, 630V
K3,K4 = 2-pin (1×2) pinheader
S1 = pushbutton NO (e.g. Multicomp R13-24A-05-BR)
Miscellaneous
PCB 160383-1 V1.1 with IC2 premounted (see text)
Resistors
R1 = 100Ohm, thick film, 5%, 0.1W, 150V
R2,R7 = 10kOhm, thick film, 5%, 0.1W, 150V
R3,R4 = 1kOhm, thick film, 5%, 0.1W, 150V
R5 = 3.6kOhm, 1%, 125mW, 150V, 0805
R6 = 240kOhm, 1%, 125mW, 150V, 0805
Capacitors
C1 = 100nF, 50V, X7R, 0805
C2 = 22µF, 10V, X5R, 20%, 1206
C3 = 1µF, 50V, 10%, X7R, 1206
C4 = 220nF, 50V, X7R, 0805
C5 = 1nF, 50V, 10%, X7R, 0603
Semiconductors
D1,D2 = 1N4148WS (100V, 200mA, 4ns)
LED1 = bicolour red/green, 3mm
T1,T2 = NVD6824NLT4G (n-channel MOSFET, 100V, 41A)
T3 = 2N7002 (60V, 250mA, 300mW, Vgs = 4.5V, RDS(on) = 1Ohm)
IC1 = MAX5024 (voltage regulator, 5V, 150mA, LDO)
IC2 = MAX16126TCA+ (voltage supervisor)
IC3 = MAX16054AZT+T (pushbutton debouncer)
K1 = 2-way PCB screw terminal block, 0.2" pitch, 630V
K2A = see text
K2B = 2-way PCB screw terminal block, 0.2" pitch, 630V
K3,K4 = 2-pin (1×2) pinheader
S1 = pushbutton NO (e.g. Multicomp R13-24A-05-BR)
Miscellaneous
PCB 160383-1 V1.1 with IC2 premounted (see text)
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