Isolation zero-cross detection circuit capable of reducing power consumption
By using electrolytic capacitors in parallel with discharge resistors for voltage division and rectification filtering in the isolated zero-crossing detection circuit, combined with transistor current amplification, the high power consumption problem caused by the optocoupler series resistor taking power at both ends of the mains is solved, and low-power isolated zero-crossing detection is achieved.
Patent Information
- Application Number
- CN202422625710.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-30
- Publication Date
- 2025-10-03
- Estimated Expiration
- 2034-10-30
AI Technical Summary
In the existing isolated zero-crossing detection circuit, the optocoupler series resistor directly draws power from both ends of the mains, resulting in high power consumption and serious resistance loss.
The discharge resistor in parallel with the electrolytic capacitor is used for voltage division, and the electrolytic capacitor is charged after rectification. Combined with the transistor current amplification, the loss of the mains power caused by the voltage division resistor is reduced.
It effectively reduces the power consumption of the isolated zero-crossing detection circuit, reduces the loss of the optocoupler series resistance, and realizes the low power consumption function.
Smart Images
Figure CN223413377U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a zero-crossing detection circuit, in particular to an isolated zero-crossing detection circuit capable of reducing power consumption. Background Art
[0002] Currently, a wide range of products on the market require isolation solutions, such as heating water dispensers, rice cookers, and toilet lids. Most of these products require temperature and speed control, both of which rely on zero-crossing signals. Common circuits use optocouplers to directly draw voltage from the mains to achieve zero-crossing. However, existing isolated zero-crossing solutions employ an optocoupler in series with a resistor, drawing power directly from both ends of the mains. However, as the mains voltage fluctuates, the optocoupler draws a constant drive current, requiring a small resistor value to achieve a stable square wave. However, this resistive voltage drop method generates significant losses, with most of the energy dissipated by the resistor. Utility Model Content
[0003] In response to the shortcomings of the existing technology, the utility model proposes an isolated zero-crossing detection circuit that can reduce power consumption. A discharge resistor connected in parallel with an electrolytic capacitor is used for voltage division. After rectification, the electrolytic capacitor is charged to obtain an effective low voltage. The current is amplified by a transistor, effectively reducing the loss of mains power caused by the voltage divider resistor.
[0004] To implement the above technical solution, the utility model provides an isolated zero-crossing detection circuit that can reduce power consumption, including: resistors R1, R2, R3, R4, R5, R6, R7, a rectifier diode D1, an electrolytic capacitor EC1, a transistor Q1 and an optocoupler U1, wherein one end of the resistor R1 is connected to ACL in the mains, the other end of the resistor R1 is connected to the resistor R2, the other end of the resistor R2 is connected to the resistor R3, the other end of the resistor R3 is connected to ACN in the mains, one end of the resistor R4 is connected to the connecting line between the resistor R2 and the resistor R3, the other end of the resistor R4 is connected to the B pole of the transistor Q1, and the E pole of the transistor Q1 is connected to the line connecting ACN and the resistor R3 On the left, the C pole of the transistor Q1 is connected to the 2nd pin of the optocoupler U1, one end of the rectifier diode D1 is connected to the connection line between the resistor R3 and the resistor R4, the other end of the rectifier diode D1 is connected to the resistor R5, the other end of the resistor R5 is connected to the 1st pin of the optocoupler U1, one end of the electrolytic capacitor EC1 is connected to the connection line between the rectifier diode D1 and the resistor R5, the other end of the electrolytic capacitor EC1 is connected to the connection line between the E pole of the transistor Q1 and the resistor R3, the 4th pin of the optocoupler U1 is respectively connected to one end of the resistor R6 and the resistor R7, the other end of the resistor R6 is connected to the +5V voltage, the other end of the resistor R7 is connected to the ZERO pin of the MCU, and the 3rd pin of the optocoupler U1 is grounded.
[0005] In the above technical solution, during actual operation, the alternating current ACL passes through resistors R1 and R2, then to resistor R3, and finally to ACN, forming a resistor divider. Resistor R4 draws power between resistors R2 and R3. After passing through resistor R4, the current flows to the B pole of transistor Q1, then flows from the B pole of transistor Q1 to the E pole of transistor Q1, and then returns to ACN, turning on transistor Q1. Rectifier diode D1 draws power between resistors R2 and R3. After passing through rectifier diode D1, the current flows to electrolytic capacitor EC1 for charging and filtering. The positive current of electrolytic capacitor EC1 flows to resistor R5 for current limiting, and then flows to pin 1 of optocoupler U1. Since transistor Q1 is already turned on, the current flows from pin 1 of optocoupler U1 to pin 2 of optocoupler U1, then from the C pole of transistor Q1 to the E pole of transistor Q1, and then back to the negative pole of electrolytic capacitor EC1. 5V DC power flows through resistor R6 to pin 4 of optocoupler U1. Because transistor Q1 inside optocoupler U1 receives light from the LED inside the optocoupler, it conducts current to ground. One pin of resistor R7 is connected to resistor R6 and pin 4 of optocoupler U1. High and low level signals flow through resistor R7 to zero, where they are sent to the MCU for processing.
[0006] Preferably, the isolated zero-crossing detection circuit, which can reduce power consumption, further includes a voltage-stabilizing diode ZD1, which is arranged in parallel with the electrolytic capacitor EC1. One end of the voltage-stabilizing diode ZD1 is connected to the connection line between the electrolytic capacitor EC1 and the resistor R5, and the other end of the voltage-stabilizing diode ZD1 is connected to the connection line between the electrolytic capacitor EC1 and the E-pole of the transistor Q1. During actual operation, the voltage-stabilizing diode ZD1 is connected in parallel to both ends of the electrolytic capacitor EC1 to stabilize the voltage across the electrolytic capacitor EC1.
[0007] The utility model provides an isolated zero-crossing detection circuit capable of reducing power consumption, which has the following beneficial effects: the isolated zero-crossing detection circuit capable of reducing power consumption has a simple structure and an ingenious design, can reduce the loss of the mains voltage to the series resistor of the optocoupler, and utilizes the divided voltage on the electrolytic capacitor discharge resistor to be rectified and filtered before being fed to the resistor in series with the optocoupler to achieve a low power consumption function, and after rectification, the electrolytic capacitor is charged to obtain an effective low voltage, which is amplified by the transistor current, effectively reducing the loss of the mains voltage to the voltage divider resistor. BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Figure 1 This is a circuit diagram of the utility model. DETAILED DESCRIPTION
[0009] The following is a clear and complete description of the technical solutions in the embodiments of the present invention, in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary persons in this field without creative work are within the scope of protection of the present invention.
[0010] Embodiment: An isolated zero-crossing detection circuit capable of reducing power consumption.
[0011] Reference Figure 1 As shown, an isolated zero-crossing detection circuit that can reduce power consumption includes: resistors R1, R2, R3, R4, R5, R6, R7, a rectifier diode D1, an electrolytic capacitor EC1, a voltage-stabilizing diode ZD1, a transistor Q1, and an optocoupler U1. One end of the resistor R1 is connected to ACL in the mains, the other end of the resistor R1 is connected to the resistor R2, the other end of the resistor R2 is connected to the resistor R3, the other end of the resistor R3 is connected to ACN in the mains, and one end of the resistor R4 is connected to the connecting line between the resistor R2 and the resistor R3. During actual operation, the alternating current ACL passes through the resistors R1 and R2, and then to the resistor R3 to ACN, forming a resistor voltage divider. The other end of the resistor R4 is connected to the B pole of the transistor Q1, the E pole of the transistor Q1 is connected to the line connecting ACN and the resistor R3, the C pole of the transistor Q1 is connected to the 2nd pin of the optocoupler U1, one end of the rectifier diode D1 is connected to the connection line between the resistor R3 and the resistor R4, the other end of the rectifier diode D1 is connected to the resistor R5, the other end of the resistor R5 is connected to the 1st pin of the optocoupler U1, one end of the electrolytic capacitor EC1 is connected to the connection line between the rectifier diode D1 and the resistor R5, The other end of capacitor EC1 is connected to the connection line between the E-pole of transistor Q1 and resistor R3. A Zener diode ZD1 is arranged in parallel with electrolytic capacitor EC1. One end of Zener diode ZD1 is connected to the connection line between electrolytic capacitor EC1 and resistor R5, and the other end of Zener diode ZD1 is connected to the connection line between electrolytic capacitor EC1 and the E-pole of transistor Q1. During actual operation, Zener diode ZD1 is connected in parallel to both ends of electrolytic capacitor EC1 to stabilize the voltage across electrolytic capacitor EC1. Pin 4 of optocoupler U1 is connected to one end of resistor R6 and one end of resistor R7, respectively. The other end of resistor R6 is connected to a +5V voltage, and the other end of resistor R7 is connected to the ZERO pin of the MCU. Pin 3 of optocoupler U1 is grounded.
[0012] In this embodiment, during actual operation, AC current ACL passes through resistors R1 and R2, then to resistor R3, and finally to ACN, forming a resistor-divided voltage. Resistor R4 draws power between resistors R2 and R3. After passing through resistor R4, the current flows to the B terminal of transistor Q1, from the B terminal of transistor Q1 to the E terminal of transistor Q1, and then returns to ACN, turning on transistor Q1. The rectifier diode D1 draws power between the resistors R2 and R3. After passing through the rectifier diode D1, the current flows to the electrolytic capacitor EC1 for charging and filtering. The voltage regulator diode ZD1 is connected in parallel to both ends of the electrolytic capacitor EC1. After stabilizing the voltage across the electrolytic capacitor EC1, the positive current of the electrolytic capacitor EC1 flows to the resistor R5 for current limiting, and then flows to pin 1 of the optocoupler U1. Since the transistor Q1 is turned on, the current flows from pin 1 of the optocoupler U1 to pin 2 of the optocoupler U1, and then from the C pole of the transistor Q1 to the E pole of the transistor Q1 and back to the negative pole of the electrolytic capacitor EC1. In this way, the divided voltage on the discharge resistor of the electrolytic capacitor EC1 can be used to achieve a low power consumption function after rectification and filtering to the resistor in series with the optocoupler, and the current is amplified by the transistor, effectively reducing the loss of the mains power by the voltage divider resistor. 5V DC power flows through resistor R6 to pin 4 of optocoupler U1. Because transistor Q1 inside optocoupler U1 receives light from the LED inside the optocoupler, it conducts current to ground, reducing the loss of the optocoupler's series resistor due to the mains voltage. One pin of resistor R7 is connected to resistor R6 and pin 4 of optocoupler U1. High and low level signals flow through resistor R7 to ZERO, where they are sent to the MCU for processing.
[0013] The isolated zero-crossing detection circuit that can reduce power consumption has a simple structure and an ingenious design. It can reduce the loss of the mains voltage on the optocoupler series resistor and realize the low power consumption function by using the divided voltage on the electrolytic capacitor discharge resistor to be rectified and filtered to the resistor in series with the optocoupler. Moreover, after rectification, the electrolytic capacitor is charged to obtain an effective low voltage, which is amplified by the transistor current, thereby effectively reducing the loss of the mains voltage by the voltage divider resistor.
[0014] The above description is only a preferred embodiment of the present invention, but the present invention should not be limited to the contents disclosed in the embodiment and the drawings. Therefore, any equivalent or modification completed without departing from the spirit disclosed in the present invention shall fall within the scope of protection of the present invention.
Claims
1. An isolated zero-crossing detection circuit that can reduce power consumption, characterized in that include: Resistors R1, R2, R3, R4, R5, R6, R7, rectifier diode D1, electrolytic capacitor EC1, transistor Q1 and optocoupler U1, wherein one end of resistor R1 is connected to ACL in the mains, the other end of resistor R1 is connected to resistor R2, the other end of resistor R2 is connected to resistor R3, the other end of resistor R3 is connected to ACN in the mains, one end of resistor R4 is connected to the connecting line between resistor R2 and resistor R3, the other end of resistor R4 is connected to the B pole of transistor Q1, the E pole of transistor Q1 is connected to the line connecting ACN and resistor R3, and the C pole of transistor Q1 is connected to the 2 Pin 1 of the optocoupler U1 is connected to the connecting line between the resistor R3 and the resistor R4, and the other end of the rectifier diode D1 is connected to the resistor R5. The other end of the resistor R5 is connected to pin 1 of the optocoupler U1. One end of the electrolytic capacitor EC1 is connected to the connecting line between the rectifier diode D1 and the resistor R5. The other end of the electrolytic capacitor EC1 is connected to the connecting line between the E pole of the transistor Q1 and the resistor R3. Pin 4 of the optocoupler U1 is connected to one end of the resistor R6 and one end of the resistor R7 respectively. The other end of the resistor R6 is connected to the +5V voltage. The other end of the resistor R7 is connected to the ZERO pin of the MCU. Pin 3 of the optocoupler U1 is grounded.
2. The isolated zero-crossing detection circuit capable of reducing power consumption according to claim 1, wherein: It also includes a Zener diode ZD1, which is arranged in parallel with the electrolytic capacitor EC1. One end of the Zener diode ZD1 is connected to the connection line between the electrolytic capacitor EC1 and the resistor R5, and the other end of the Zener diode ZD1 is connected to the connection line between the electrolytic capacitor EC1 and the E pole of the transistor Q1.