As shown in Figure is a limiting protection charger. VT transistors and resistors R3 form limiting network. Seen from the figure, the resistor R3 is the base of transistor VT e
mitter Q resistor connected in series with the battery being charged. Charging current flows through the resistor R3. When the charge current is too large, the voltage drop on R3 exceeds 0.6V, the transistor VT will be turned on. Because VT parallel with resistor R2, VT conduction, so that the equivalent parallel resistance decreases, the output voltage Uo decreases, the output current is reduced, so as to achieve the purpose of limiting the charging current. When taken R3 l ), the maximum charging current is Iom 0.6/1 0.6A, select a smaller R3 will be higher charging current, but can not exceed the maximum integrated voltage regulator output current value.