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LOW-COST DOUBLE LI-ION BATTERY CHARGER USING ST6255C/ST6265C MCU

Figure 3. PWM Signal Generation Circuit

Selecting the proper power PNP transistor is not enough to make sure the buck converter can

also be chosen accordingly.

to be in saturation state, with a high base current. This current is equal to:

are on. It equals the sum of saturation collector-emitter voltages for the 2 NPNs.

Example with the evaluation board hardware:

– When on, the NPN transistors must also be in saturation state.

V

PWM signal from ST6

A

rear

V

supply

rear charge enable

signal from ST6

A

front

supply

front charge enable

signal from ST6

EB

BE

B

Son

BE

ply

sup

B

R

V

R

V

V

V

I

−

−

−

=