Overvoltage protection circuit for integrated circuit

Abstract

The invention discloses an overvoltage protection circuit for an integrated circuit, which comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a PMOS transistor, a first NMOS transistor, a second NMOS transistor, a comparator and a plurality of zener diodes, wherein all the zener diodes are connected by connecting the negative electrode with the positive electrode sequentially; the overvoltage protection of the integrated circuit and the clamping and electrostatic discharge protection of an input power can be easily realized by selecting appropriate zener voltage and number of the zener diodes and the resistance valves of the first, second and third resistors; and the second NMOS transistor and the fifth resistor constitute an effective input power electrostatic discharge protection circuit; therefore, additional electrostatic discharge protection circuits are not required to monitor the overvoltage condition of the input power, and the complexity of the integrated circuit is greatly reduced; in addition, the overvoltage protection circuit can be applied to other systems besides an electronic power system, so the overvoltage protection circuit has wide application.

Description

technical field [0001] The invention relates to a voltage protection circuit, in particular to an integrated circuit overvoltage protection circuit. Background technique [0002] In electronic power systems, such as flyback AC-DC, LED power drive and other systems, these systems are usually composed of integrated circuits, transformers, peripheral resistors, capacitors and inductors that control the operation of the system. In these systems, the input power VDD of the integrated circuit is usually provided by the auxiliary coil of the transformer, but it is often affected by the output load and there is a danger of overvoltage. Such as figure 1 As shown in a common AC-DC system, the input power VDD of the integrated circuit U1 is provided by the auxiliary coil NA of the transformer T1. As the output load increases, the input power VDD will also increase accordingly, so there will be Risk of overvoltage. Therefore, in order to prevent the damage of the control integrated c...

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Problems solved by technology

Existing methods such as figure 2 As shown, usually a zener diode DZ is connected to the power supply ground at the input power port inside the integrated circuit, and the input power VDD is clamped at a fixed value by using the zener voltage of the zener diode DZ. This method can simply guarantee The input power supply VDD will not exceed the predetermined value, but the disadvantage is that the power consumption is too large, and the larger the input power supply VDD, the greater the power consumption, which cannot meet the current energy-saving and environmental protection requirements; at the same time, this method also requires additional circuits to Monitor the overvoltage of the input power supply VDD, which increases the complexity of the system

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