| 摘要 |
PROBLEM TO BE SOLVED: To decrease power to be dispersed over a drive circuit by providing off-time noise immunity for the power MOSFET gate drive circuit to accelerate the turn-off speed of controlled switch. SOLUTION: A drive signal inputted to an isolation transformer T is made into rectangular bipolar waveform, and this signal is made into low impedance. A 1st area is made into the voltage of positive polarity for the ON of transistor Q1, namely, +VPK and a 2nd area is made into -VPK corresponding to the OFF of Q1. The source impedance of gate is kept low and a 3rd area is made into zero impedance. A drive MOSFET Q2 has high mutual conductance in all operating states, gets a gate current in ordinary state, minimizes the load of gate drive circuit and increases a drain current. Besides, a current pulse is let flow to a gate circuit loop by a positive voltage at the dotted line end of transformer T1, a capacitor Cin 1 is charged at +VPK, Q1 is turned on and Q2 is disconnected from the circuit. |
