CC/CV Charger Loop

by VladM

28 parts

A linear CC/CV charger. Q1, a P-MOSFET, feeds the cell from a 5V supply (100mF + 400mΩ, starting at 3.0V). U1 holds the current: Rsense (0.1Ω) against Viset 0.1V; U2 holds the voltage: bat against Vvset 4.2V. Each pulls the gate up through its diode, so whichever wants less current wins: the CC-to-CV handover is the moment the two amplifier outputs, Iloop and Vloop, cross. Press Run: on screen at ×0.25 the current reaches its plateau after about 2s, hands over at about 7s and falls through C/10 (0.1A) at about 17s.

• VIN 5V
• Q1 Vt 2V
• Cg 3.3µF
• Rg 10kΩ
• Rser 1kΩ
• ESR 400mΩ
• cell 100mF
• Rsense 100mΩ
• U1
• Rd1 1MΩ
• Rc1 1kΩ
• Viset 100mV
• D1
• U2
• Rd2 1MΩ
• Rc2 1kΩ
• Vvset 4.2V
• D2