PLC and PLC triode output protection circuit

Abstract

The invention discloses a PLC triode output protection circuit which is applied to a PLC. The PLC comprises a control unit and a triode; the control unit is connected with the base electrode end of the triode; the PLC triode output protection circuit comprises a diode; the forward end of the diode is respectively connected with the collector electrode end of the triode and the first end of an inductive loader; the backward end of the diode and the second end of the inductive loader are both connected with the anode of a power supply; the cathode of the power supply is connected with the emitter electrode end of the triode. Therefore, at the moment the triode is turned off, the inductive loader generates high voltage at the collector electrode end, then the diode is conducted, high potential generated at the collector electrode end can be quickly guided into the anode of the power supply, the high potential at the collector electrode end can be inhibited, an ideal triode protecting effect is achieved, and the diode use cost is low. The invention further discloses the PLC.

Description

technical field [0001] The invention relates to the technical field of PLC output protection, in particular to a PLC and a PLC triode output protection circuit. Background technique [0002] In the output circuit of PLC (Programmable Logic Controller, Programmable Logic Controller), there is a kind of triode (transistor) output. The program controls the turn-on and cut-off of the triode to play the role of a switch. When the user uses the PLC as a switch to control other circuits, if the connected external circuit exhibits the characteristics of an inductive load, at the moment the triode is turned off due to the continuous flow of the inductive load (the principle of electromagnetic induction), it will be generated at the collector of the triode. Instantaneous high voltage will damage the triode. [0003] In order to solve this technical problem, in the prior art, a Zener diode is usually used to absorb the flyback voltage on the output circuit of the PLC triode, such as ...

AI Technical Summary

Problems solved by technology

When the user uses the PLC as a switch to control other circuits, if the connected external circuit exhibits the characteristics of an inductive load, at the moment the triode is turned off due to the continuous flow of the inductive load (the principle of electromagnetic induction), it will be generated at the collector of the triode. Instantaneous high voltage, causing damage to the triode

[0003] In order to solve this technical problem, in the prior art, a Zener diode is usually used to absorb the flyback voltage on the output circuit of the PLC triode, such as figure 1 As shown, since the reverse breakdown power of the Zener diode is relatively small, it is easy to cause the thermal breakdown of the Zener diode and burn it in the place where the relatively high flyback voltage is used, so that the output circuit of the triode will lose protection, and then damage the triode.

If you increase the reverse breakdown power of the Zener diode or increase the withstand voltage of the triode, the circuit cost will be greatly increased.

Images