Original: 33µH drum core (saturates early).
Better: 47µH shielded power inductor (e.g., CDRH127 or SRN1060 series).
Below is the typical block schematic you’ll find online for generic WXDC12003 clones:
Input + ---[Cin]---[IC Vin]---[Internal Switch]---[L]--- Output +
| | |
[GND] [D1] [Cout]
| | |
Input - --------------------------------------------- GND
Feedback is taken after Cout, via a resistor divider (R1/R2) into the IC’s FB pin.
This works, but note: No feedforward capacitor, no compensation network, undersized inductor. wxdc12003 schematic better
A high-resolution PDF of the improved WXDC12003 schematic is available via public electronics repositories (search for “WXDC12003 enhanced schematic v2”). When sharing, always include:
Place a 10nF–100nF ceramic cap across the upper feedback resistor (R1).
This creates a zero in the control loop, improving transient response. On stock WXDC12003, load step from 0.5A to 2.5A causes a 300mV dip; with Cff, it drops to 80mV.
Stock: SS34 (3A, 40V).
Better: SS54 (5A, 40V) or SB540 (5A, 40V, lower Vf).
Lowers power loss at 3A from ~1.2W to ~0.7W. Original: 33µH drum core (saturates early)
Here is the improved schematic ready for breadboard or PCB layout:
Vin+ (12V-24V) ----||---+----[IC Vin pin] (WXDC12003) 0.1µF | | 100µF/35V GND | | +----[Inductor 47µH]----+---- Vout+ | | [SS54] +----[220µF]---- GND | | +----[IC SW pin] +----[47µF ceramic]--- GND | IC FB pin -----[R1]---- Vout+ | [R2] | GND
Cff (10nF) placed across R1
Typical values for adjustable output (Vout = 1.25(1+R1/R2)):*
Measurement fact: At 2.5A output, the stock module’s efficiency drops to ~78%, while the inductor reaches 105°C.
DC Jack -> Fuse/PTC -> TVS Protection Diode -> Main Power Switch -> Battery BMS (if charging) / System Rail Feedback is taken after Cout, via a resistor