Patent ID: 11863167
Assignee: NANJING GREENCHIP SEMICONDUCTOR CO., LTD.
Field: Basic communication processes (Electrical engineering)
Classification: CPC H  Y | IPC H

Claim 0:
1. A drive circuitry for power transistor of a switching power supply comprising:
a first pull-up drive transistor;
a second pull-up drive transistor coupled to said first pull-up drive transistor in parallel; and
a first pull-down drive transistor coupled to said first pull-up drive transistor and said second pull-up drive transistor in series, wherein said first pull-up drive transistor is connected to a power supply and gate of an external power switching transistor, and is controlled by an external control signal through a first control path connected to said first pull-up drive transistor;
wherein said pull-up drive transistor is connected to a second control path, said power supply and said gate of said external power switching transistor, and is controlled by said external control signal through said second control path;
wherein said first pull-down drive transistor is connected to said external control signal;
in a case that said external control signal is at high level, said first pull-up drive transistor is turned on and outputs a predetermined clamp voltage, and said second pull-up drive transistor is turned off;
in a case that said external control signal is at high level, on or off state of said second pull-up drive transistor is determined by comparing voltage of said power supply and a threshold voltage, if said voltage of said power supply is higher than said threshold voltage, said second pull-up drive transistor is turned off, and said external power switching transistor is charged by said first pull-up drive transistor;
in a case that said external control signal is at high level and voltage of said power supply lower than a threshold voltage, on or off state of said second pull-up drive transistor is determined, by comparing output gate voltage of said external power switching transistor, a first reference voltage and a second reference voltage, through said second control path; if said output gate voltage of said external power is lower than said first reference voltage, said second pull-up drive transistor is turned off, said external power switching transistor is charged by said first pull-up drive transistor; if said output gate voltage of said external power switching transistor is between said first reference voltage and said second reference voltage, said second pull-up drive transistor is turned on, said external power switching transistor is charged by said first pull-up drive transistor and said second pull-up drive transistor; if said output gate voltage of said external power switching transistor is higher than said second reference voltage, said second pull-up drive transistor is turned off, said external power switching transistor is charged by said first pull-up drive transistor, wherein said first reference voltage is smaller than said second reference voltage;
in a case that said external control signal is at low level, both said first pull-up drive transistor and said second pull-up drive transistor are turned off, said first pull-down drive transistor is turned on, said external power switching transistor is discharged by said first pull-down drive transistor.