Earth leakage detection circuit

Abstract

The invention provides an earth leakage detection circuit. A zero-phase current transformer (102) detects a ground fault current and outputs a zero-phase current. When the voltage of the zero-phase current exceeds a positive side threshold (TH1) or drops below a negative side threshold (TH2), an open collector output circuit (108) operates to discharge a capacitor (104). When the inter-plate voltage of the capacitor (104) drops below a threshold voltage (Vref), a control means (134) detects the fact as earth leakage and notifies the control section (212) of an air conditioner (200) to this effect.

Description

technical field [0001] The invention relates to the leakage detection function. Background technique [0002] According to the prior art, a leakage detection function has been proposed to detect the presence or absence of leakage by multiple detections of currents exceeding a predetermined positive threshold and currents below a predetermined negative threshold. For example, it is disclosed in Patent Document 1. . [0003] Patent Document 1: (Japanese) Unexamined Patent Publication No. 2003-219552 [0004] The purpose, characteristics, aspects and advantages of the present invention will be clarified by the following detailed description and accompanying drawings. [0005] However, in the technology disclosed in the above-mentioned Patent Document 1, as long as the current exceeding the threshold on the positive side and the current below the threshold on the negative side cannot be detected multiple times together, it cannot be detected as a leakage, so there is a problem...

AI Technical Summary

Problems solved by technology

[0005] However, in the technology disclosed in the above-mentioned Patent Document 1, as long as the current exceeding the threshold on the positive side and the current below the threshold on the negative side cannot be detected multiple times together, it cannot be detected as a leakage, so there is a problem that it cannot be quickly responded to. question

In addition, for example, when alternating current is converted to direct current by a rectifier such as a semiconductor switching element (thyristor), there is a problem that current leakage in the positive direction cannot be detected even if the current in the positive direction exceeds the positive side threshold value because the current in the negative direction cannot flow. (refer to Figure 9 : Figure explaining the subject of the present invention)

[0006] In addition, when using an integrated circuit with a leakage detection function, since noise may be generated by the operation of the integrated circuit, there is a problem that countermeasures against noise must also be devised in addition to the leakage detection function.

Images