Isolation type precision zero-crossing detection circuit

Abstract

The invention discloses an isolation type precision zero-crossing detection circuit, which comprises a power supply circuit part, a high voltage zero-crossing detection circuit part, a signal enhancing circuit part, an optical coupler drive circuit part and an isolation output circuit part. The power supply circuit part includes a resistor R5, a resistor R6, a resistor R9, a rectifier diode D1, a rectifier diode D3, a Zener diode ZD1, a capacitor C3, a capacitor C4, and a capacitor C6. The high voltage zero crossing detection circuit part includes a resistor R3, a resistor R4, a triode Q2, a capacitor C5, and a rectifier diode D2. The signal enhancing circuit part includes a resistor R1, a resistor R7, a capacitor C1 and a triode Q1. The optical coupler drive circuit part includes a resistor R2, a resistor R8 and a capacitor C2. The isolation output circuit part includes a resistor R10. With a proper design, the precision of zero-crossing detection in a strong and weak power isolation circuit can be increased; the manufacturing cost and development difficulty for products with demanding requirement on power precision control can be reduced; and the development cycle is shortened.

Description

technical field [0001] The invention belongs to the field of zero-crossing detection equipment for household appliances, and in particular relates to an isolated precise zero-crossing detection circuit. Background technique [0002] In some household appliances, the control board uses the single-chip software to adjust the power of the AC load to achieve the purpose of controlling heating and speed control. First, it is necessary to detect the zero point in the AC power, that is, the moment when the voltage of the neutral line and the live line are equal. Based on this moment, delay for a certain period of time, and then trigger the thyristor to conduct, so that the load works in an incomplete and controllable sine wave power supply environment, and the power is changed to achieve the purpose of control. [0003] At present, the zero-crossing detection circuit is divided into two categories: strong current detection and weak current detection; power supply design is divided ...

AI Technical Summary

Problems solved by technology

The current products seem to run stably, but that is only a superficial phenomenon. The real power is fluctuating. For some demanding application products, some other methods have to be adopted, such as frequency conversion, DC control, and various feedback signals to participate in the calculation. , which not only increases the complexity of the circuit and product cost, but also increases the difficulty of development and prolongs the development cycle

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