A low cost, board level, inductor-based charge pump is provided to
generate a sufficiently high voltage to drive a power MOSFET 307 having a
rotor coil 311 attached on its source side in an automotive alternator
voltage regulator. A first BJT transistor 303 of the charge pump receives
a clock signal at its base from an application specific integrated
circuit (ASIC) 302. The clock signal continuously turns transistor 303 on
and off, forcing a current to flow through an inductor 301 connected to a
voltage supply terminal. A second BJT transistor 308 receives a gate
control signal at its base from the ASIC 302 for turning the second
transistor 308 on and off to enable the circuit. In operation when the
first transistor 303 is turned off, a slowly decreasing current flows
from the inductor 301 to an output node. With the base of the second
transistor 308 low to enable the system, the second transistor 308 is
turned off and the current flows from the output node through a capacitor
309 to ground. The current charges the capacitor 309 to a higher voltage
level than the alternator system voltage Vcc. The voltage across the
capacitor 309 is sufficiently high to drive the power MOSFET 307 in an
automotive alternator voltage regulator.