公开(公告)号：JPH0360039A

公开(公告)日：1991-03-15

申请号：JP19320290

申请日：1990-07-23

Applicant: SGS THOMSON MICROELECTRONICS

Inventor： SARUBATOORE RACHITEI ,  SERUJIO PARAARA

IPC: H01L29/73 ,  H01L21/331 ,  H01L21/822 ,  H01L27/02 ,  H01L27/04 ,  H01L27/06 ,  H01L29/732

Abstract: PURPOSE: To prevent break of a parasitic transistor by providing a shield element against negative impulses of a power source voltage in its voltage limiter. CONSTITUTION: If power apparatuses Q3 and Q4 are in a conducting state and an inductor L is assumed to be in a charged state, then any negative impulse on the voltage Vs executes the extinction of the arc on the power apparatuses Q3 and Q4 at the negative base voltage of the transistor Q3. At the same time, a voltage Vc at the common collector rises up to a clamp voltage set by a Zener diode Z2, and two breakdown stresses reverse to the power apparatuses Q3 and Q4 are produced, but these stresses are prevented by a voltage limiter constituted with transistors Q2 and Q5, a resistor Rc and a Zener diode Z1. Under this condition, the transistor Q2 is kept at a negative potential at its base by a voltage Vs, so that the arc is extinguished because the base is kept at a negative potential by the voltage Vs, and a positive over-voltage Vc on the load L ignites the transistor Q5, power apparatuses Q3 and Q4 in Darlington configuration are returned to a conducting state, and a positive over-voltage is discharged to the ground. By doing this, the parasitic effect caused by the negative impulse of the power source voltage can be eliminated.

公开(公告)号：JPH02304960A

公开(公告)日：1990-12-18

申请号：JP11189690

申请日：1990-05-01

Applicant: SGS THOMSON MICROELECTRONICS

Inventor： SARUBATOORE RACHITEI ,  SERUJIO PARAARA

IPC: H01L29/73 ,  H01L21/331 ,  H01L27/02 ,  H01L27/06 ,  H01L29/732 ,  H03K17/082

Abstract: PURPOSE: To surely enable setting a transistor itself to be protected, to a value lower than its ignition threshold by providing automatic commutating means between the base of the transistor and the collectors of power devices, and when the collector voltage of a power device drops from a preset value, generating currents associated with lower voltage drops between the base and collectors. CONSTITUTION: Automatic commutating means QP1 and QP2, which generate currents associated with low-voltage drops between the base of a transistor Q2 to be protected and collectors of power devices Q3 and Q4, when the collector voltage of a power device 1 drops from a preset value are provided between the base and collectors. When the collector voltage Vc of the device 1 drops from a preset value, a current having a small value and associated with a low-voltage drop flows to the collector of the device 1 from the base of the transistor Q2 through the means QP1 and QP2, so as to maintain the base/emitter voltage of the transistor Q2 at a value which is not higher than the conducting threshold of the transistor Q2. Therefore, the transistor Q2 to be protected is surely protected, so as to automatically set the transistor Q2 to a value lower than its ignition threshold.