Photoelectric Couplers And Their Applications: Traditional Chinese Cir

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Optocoupler and its applicationsOptocoupler is a semiconductor optoelectronic device developed in recent years. Due to its small size, long life, strong anti-interference ability, wide operating temperature and complete electrical isolation of contactless input and output, it is widely used in the field of electronic technology and industrial automatic control. It can replace relays, transformers, choppers, etc., and is used in isolation circuits, switching circuits, digital-to-analog conversion, logic circuits, overcurrent protection, long-line transmission, high-voltage control and level matching.In order to enable readers to understand and apply photoelectric couplers, several photoelectric coupling devices and application circuits are introduced for your reference and development.1． Device selection(1) Transistor output type photocouplerThe triode output type photocoupler circuit is shown in (a) in Figure 46-1. It consists of two parts. Among them, terminals 1 and 2 are input terminals, usually composed of light-emitting devices; terminals 4, 5, and 6 are connected to a photosensitive transistor to form the output terminal. When the infrared light emitted by the transmitter is received, there will be a current output in the collector of the triode. alt="46-1.jpg (18117 bytes)"> Figure 46-1The characteristics of the triode output type photocoupler are its high input and output insulation performance, frequency response up to 300kHz, and switching time of several microseconds.(2) Thyristor output optical couplerThe circuit of the thyristor output optical coupler is shown in (b) in Figure 46? The device is a six-pin dual-in-line package. When the input signal is added to terminals 1 and 2, the infrared light emitted by the transmitter tube is received by the photosensitive thyristor connected to pins 4, 5 and 6, causing it to conduct. It can be used in low-voltage electronic circuits to control the opening of high-voltage AC circuits.(3) Optically coupled thyristor switch driver(a) in Figure 46-2 is a photosensitive bidirectional switch device; (b) in Figure 46-2 is a combination of a zero-crossing control circuit and a photosensitive bidirectional switch device. Their working principle is: use the infrared light at the input end to control the conduction of the photosensitive two-way switch at the output end, and then trigger the conduction of the external bidirectional thyristor to achieve the purpose of controlling the load to connect to the AC 220V loop. (a) in the figure is non-zero-crossing control, and (b) in the figure is zero-crossing control. This driver has very good input and output insulation and can form a solid-state relay control circuit. Its output control power is determined by the controllable allowable power. …

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