High voltage generator using inductor-based charge pump for automotive alternator voltage regulator

摘要

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.