LOAD SHORTCIRCUIT DETECTION CIRCUIT OF IGBT AND PROTECTING CIRCUIT USING IT

摘要

PURPOSE:To detect load shortcircuit without using high voltage signal and to acquire a load detection circuit without false detection by providing an IGBT a driver of a gate thereof and a bipolar transistor for detecting electric potential between electric potential of a gate path of the IGBT and electric potential of a driving power supply path of the driver. CONSTITUTION:When an input IN2 is 'on' level, an IGBT element Q2 is 'on' and normal load current flows to load R. In the state, when input IN1 is 'on' level and IGBT element Q1 is 'on', shortcircuit occures in the IGBT element Q2 and collector electric potential of the Q2 rises. Owing to the electric potential rise, gate electric potential of the Q2 rises through gate-to-collector capacity CGC, a bipolar transistor Q4 is 'on', a flip-flop 55 is set, and Q3 is in 'on' state. Load shortcircuit is detected by 'on' of the transistor Q4. Gate electric potential of the IGBT element Q2 is restrained from approximately +VGG to 'R2.VGG/ R1+R2+R4' by 'on' of the transistor Q3. Since a collector-to-emitter current thereby decreases, an allowable shortcircuit time of Q2 is increased.