Current detection circuit

Abstract

The present invention provides a current detection circuit. Using a electrostatic capacitor (12) and a diode (13), a gate voltage of a protecting MOSFET (7) is increased when a drain voltage of a power transistor (2) increases. A voltage clamp circuit (14) clamps the maximum voltage of the gate voltage of the protecting MOSFET (7)to a predetermined clamp voltage (Vc). A voltage control circuit (17) controls a drain voltage of a sense transistor (6) so as to substantially coincide with a source voltage of the protecting MOSFET (7). A detection circuit (40) detects the current of the drain of the sense transistor (6). Therefore, even if the substrate bias effect occurs in the protecting MOSFET of the current detection circuit of the power transistor, the current of a load is detected precisely by means of a high voltage negatively fed back by the operation amplifier on the basis of satisfying the resistant voltage between the source and gate of the protecting MOSFET.

Description

Technical field [0001] The present invention relates to a current detection circuit for detecting the value of current flowing through a power semiconductor device. Background technique [0002] Power semiconductor devices such as thyristors (hereinafter referred to as power transistors) are semiconductors that convert and control electric power. For example, they are mostly used as drive elements for inverter control of motors or power for switching power supplies. control element. Specifically, in order to generate the driving torque of the motor load, the current flowing through the power transistor is used, and in the switching power supply, the power transistor is used for improving the responsiveness. In particular, compared with Bipolar Junction Transistor (BJT) or semiconductor thyristor, IGBT (Insulated Gate Bipolar Transistor: Insulated Gate Bipolar Transistor) and Power MOSFET (Metal Oxide Semiconductor Field Effect Transistor: Metal Oxide Semiconductor Field Effect T...

AI Technical Summary

Problems solved by technology

However, even if LDD (Lightly Doped Drain) structure or the like is used to increase the withstand voltages between the drain-gate and the drain-substrate of the enhancement type MOSFET 137, in order to increase the mutual conduction between the source and the gate, the integrated The withstand voltage is usually the lowest in the circuit

Therefore, with respect to the minimum voltage value of the source voltage, a voltage equal to or less than the withstand voltage between the source and the gate can be applied to the gate of the enhancement type MOSFET 137 at most.

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