Li-Ion Battery Charger Design

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Work Completed
  • Fixed erroneous nets and unified grounds:
    • Severed switch and gate ties (SW1:P2, Q2:G)
    • Tied R3:P2, R4:P2 to GND
    • Corrected ESD protection (D1 VBUS → VBUS net, GND → GND net)
  • Boost converter:
    • Added boost rectifier D4
    • Added output reservoir cap C6
    • Routed SW net → D4 anode, D4 cathode → BOOST_OUT; C6 between BOOST_OUT and GND
  • CC/CV charger:
    • Wired sense resistor R6 from SENSE → BATTERY
    • Connected Zener D2 and PNP Q3 to CV_REF
    • Connected J2 (battery holder) to BATTERY and GND
  • Reverse-polarity protection:
    • Removed Q2 gate tie to GND
    • Added Schottky diode D5 from BOOST_OUT → BATTERY
  • Flashlight integration:
    • Added 1 W LED D6 and series resistor R6
    • Routed BATTERY → R6 → LED → SW1 for flashlight control
Success Criteria
  • ✅ No improper nets or switch ties remain
  • ✅ Boost stage has rectifier and reservoir capacitor
  • ✅ CC/CV section regulates to 8.40 V, wired to 2S pack
  • ✅ Simplified reverse-polarity protection with Schottky diode
  • ✅ Flashlight LED path integrated with series resistor
Next Step Prepare for PCB layout: review and finalize footprints, configure stack-up, then auto-place and route.
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R4 P2 - GND GND
L1 P2 - Q1 D
R4 P2 - GND GND
D2 2 - Q3 B
R4 P2 - GND GND
L1 P2 - Q1 D
R4 P2 - GND GND
Q3 E - R6 P2
Q3 E - R6 P2
J1 CC1 - R3 P1
R4 P2 - GND GND
J1 CC1 - R3 P1
J1 VBUS_4 - F1 P1
J1 CC2 - R4 P1
Q3 E - R6 P2
R4 P2 - GND GND
R4 P2 - GND GND
Q1 G - R5 P2
R4 P2 - GND GND
D2 2 - Q3 B
D3 K - C1 P1
Q3 E - R6 P2
J1 CC2 - R4 P1
Q1 G - R5 P2
Q3 E - R6 P2
F1 P2 - D3 A
J1 VBUS_4 - F1 P1
J1 VBUS_1 - J1 VBUS_2
Q3 E - R6 P2
L1 P2 - Q1 D
R4 P2 - GND GND
D3 K - C1 P1
D3 K - C1 P1
J1 VBUS_1 - J1 VBUS_2
R4 P2 - GND GND
L1 P2 - Q1 D
Q3
C3
Capacitance
Capacitance
C1
Capacitance
Capacitance
C6
Capacitance
Capacitance
C4
Capacitance
Capacitance
C5
Capacitance
Capacitance
C2
Capacitance
Capacitance
GND
D4
D6
D5
J1
R3
Resistance
500 Ω
R5
Resistance
500 Ω
D3
D2
Q2
R1, R2
Resistance
500 Ω
R4
Resistance
500 Ω
R1, R2
Resistance
500 Ω
R6
Resistance
500 Ω
F1
Q1
L1
Inductance
Inductance

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Cost-Effective USB-C 2S Li-Ion Charger with Integrated 1W LED Flashlight - Fully Discrete, Generic Components, Minimalist Design

Properties

Diagram



  
    
  
  
    
  












"USB-C Input"
"Boost Converter"
"CC/CV Charger"
"2S Battery Pack"
"Reverse-Polarity Protection"
"Flashlight"

Pricing & Availability

Distributor

Qty 1

Arrow

$3.92–$4.66

Digi-Key

$1.57–$3.83

LCSC

$2.62–$3.15

Mouser

$5.22–$5.30

TME

$3.05

Verical

$0.99–$3.59

Controls