Low power isolated zero crossing circuit

Abstract

The utility model belongs to zero -crossing detection circuit technical field, especially for a kind of low power consumption and take isolated zero -crossing circuit, this low power consumption and take isolated zero -crossing circuit includes ac power unit, DC power unit, rectifier unit, zero -crossing detection unit, DC power unit is equipped with switch control subunit and pulse transformer subunit, zero -crossing detection unit is equipped with electronic switch, photoelectric coupler and zero -crossing signal detection circuit, the control end electric connection of electronic switch is to the live wire of ac power unit, pulse transformer subunit is equipped with auxiliary winding, the output end of auxiliary winding and the input side of photoelectric coupler and electronic switch are connected in series and then grounded, the auxiliary winding of transformer of pulse transformer subunit is powered to the input side inside photoelectric coupler of emitting diode, effectively reduce power consumption.And through electronic switch control photo-coupler input side emitting diode on-off, control accuracy is high, solve the problem of big zero-crossing positive and negative deviation caused by current photo-coupler isolation.

Description

Technical Field

[0001] This utility model belongs to the field of zero-crossing detection circuit technology, specifically relating to a low-power zero-crossing circuit with isolation. Background Technology

[0002] In circuits, zero-point voltage detection is a common functional requirement. Zero-point detection outputs a detection signal when the AC voltage is "zero". This detection signal can be used to further realize other control functions. For example, in dimming switches and motor speed control devices, the AC conduction angle can be controlled from zero point through the zero-point voltage detection signal to realize the adjustment of the brightness of dimming lamps and the speed of motors.

[0003] For zero-point voltage detection, the zero-point voltage on the high-voltage side is usually detected by measuring the voltage on the low-voltage side, such as... Figure 1 As shown, Figure 1 It is a common zero-point voltage detection circuit currently used in Figure 1 In this circuit, an optocoupler U1 is installed between the high-voltage and low-voltage sides. Optocoupler U1 serves to isolate and convert signals between the two sides. The live wire ACL and neutral wire ACN on the high-voltage side provide operating voltage for loads such as lamps and motors. A voltage divider circuit, consisting of power resistors R1 and R2 and a Zener diode D1, powers the optocoupler U1. On the low-voltage side, a signal sampling circuit, consisting of resistors R3 and R4 and a filter capacitor C1, connects the +5V power supply to the ground terminal GND. The zero-point signal ZERO is acquired between resistor R4 and filter capacitor C1. For this... Figure 1 The zero-point voltage detection circuit in the power supply has the following problems: because the optocoupler U1 takes the signal from the high voltage side, the optocoupler U1 needs to be connected in parallel with power resistors R1 and R2 and Zener diode D1. Due to the power consumption of power resistors R1 and R2 and the current consumption of the LED inside the optocoupler U1, the standby power consumption of the power supply is too high. Utility Model Content

[0004] The present invention aims to provide a low-power, isolated zero-crossing circuit to solve the technical problem of excessive standby power consumption of existing zero-crossing detection circuits.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A low-power circuit with isolated zero-crossing is provided, comprising: An AC power supply unit, which is equipped with a live wire and a neutral wire; A DC power supply unit, which includes a switch control subunit and a pulse transformer subunit, wherein the switch control subunit is electrically connected to the pulse transformer subunit; A rectifier unit, which is electrically connected between the AC power supply unit and the DC power supply unit; The zero-crossing detection unit includes an electronic switch, an optocoupler, and a zero-crossing signal detection circuit. The control terminal of the electronic switch is electrically connected to the live wire. The pulse transformer subunit has an auxiliary winding. The output terminal of the auxiliary winding is connected in series with the input side of the optocoupler and the electronic switch and then grounded. The zero-crossing signal detection circuit is electrically connected to the output side of the optocoupler.

[0006] Preferably, a first diode and a first current-limiting resistor are provided between the output end of the auxiliary winding and the input side of the optocoupler.

[0007] Preferably, the electronic switch is a transistor, and a second diode and a second current-limiting resistor are provided between the live wire and the base of the transistor.

[0008] Preferably, the DC power supply unit includes a first voltage regulator circuit electrically connected to the output terminal of the rectifier unit. The first voltage regulator circuit outputs a first DC voltage source. The input terminal of the primary winding of the pulse transformer subunit is electrically connected to the positive terminal of the first DC voltage source, and the output terminal of the primary winding is electrically connected to the negative terminal of the first DC voltage source via the switch control subunit.

[0009] Preferably, the DC power supply unit includes a second voltage regulator circuit electrically connected to the secondary winding of the pulse transformer subunit, and the second voltage regulator circuit outputs a second DC voltage source.

[0010] Preferably, the zero-crossing signal detection circuit includes a first voltage divider resistor, the second DC voltage source is grounded through the first voltage divider resistor and the output side of the optocoupler, an RC filter circuit is connected in parallel on the output side of the optocoupler, and a zero-crossing signal monitoring point is provided in the RC filter circuit.

[0011] Preferably, a differential mode suppression capacitor is provided between the live wire and the neutral wire of the AC power supply unit; and a common mode suppression capacitor is provided between the primary winding and the secondary winding of the pulse transformer subunit.

[0012] Preferably, the rectifier unit is a rectifier bridge.

[0013] Compared with existing technologies, the beneficial effects of this utility model are as follows: This low-power, isolated zero-crossing circuit includes an AC power supply unit, a DC power supply unit, a rectification unit, and a zero-crossing detection unit. The DC power supply unit has a switch control subunit and a pulse transformer subunit. The zero-crossing detection unit has an electronic switch, an optocoupler, and a zero-crossing signal detection circuit. The control terminal of the electronic switch is electrically connected to the live wire of the AC power supply unit. The pulse transformer subunit has an auxiliary winding. The output terminal of the auxiliary winding is connected in series with the input side of the optocoupler and the electronic switch and then grounded. The auxiliary winding of the transformer in the pulse transformer subunit supplies power to the LED on the input side of the optocoupler, effectively reducing power consumption. Furthermore, the electronic switch controls the on / off state of the LED on the input side of the optocoupler, resulting in high control accuracy and solving the problem of large positive and negative zero-crossing deviations caused by current optocoupler isolation. Attached Figure Description

[0014] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is the circuit schematic of an existing isolated zero-crossing circuit.

[0015] Figure 2 This is a circuit diagram of an embodiment of the present invention, which features low power consumption and isolation zero-crossing circuit. Detailed Implementation

[0016] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0017] In one embodiment, a low-power circuit with isolated zero-crossing is provided, such as Figure 2 As shown, the low-power circuit with isolated zero-crossing includes an AC power supply unit 10, a DC power supply unit, a rectifier unit 40, and a zero-crossing detection unit 50. The DC power supply unit is equipped with a switch control subunit 20 and a pulse transformer subunit 30. The AC power supply unit 10 provides an AC voltage source, which is rectified by the rectifier unit 40 to obtain a DC voltage, which is then supplied to the DC power supply unit. The switch control subunit 20 of the DC power supply unit controls the pulse transformer subunit 30 to perform voltage conversion on the rectified DC voltage. The zero-crossing detection unit 50 is used to detect the zero point of the AC voltage source provided by the AC power supply unit 10 and outputs a zero-crossing detection signal.

[0018] Specifically, such as Figure 2 As shown, the AC power supply unit 10 has a live wire ACL and a neutral wire ACN. A fuse FUSE1 is installed on the live wire ACL for overcurrent protection. A varistor ZNR1 is installed between the live wire ACL and the neutral wire ACN to absorb surge energy in the circuit. A differential mode suppression capacitor, namely capacitor CX1, is also installed between the live wire ACL and the neutral wire ACN to suppress differential mode noise between the live wire ACL and the neutral wire ACN. A resistor RF1 installed on the live wire ACL is used for current limiting. A series resistor RX1 and a resistor RX2 are also installed between the live wire ACL and the neutral wire ACN to discharge capacitor CX1 to ensure safety when the power is off.

[0019] like Figure 2 As shown, the switch control subunit 20 is electrically connected to the pulse transformer subunit 30. The switch control subunit 20 includes a switch control chip U1 and its peripheral circuitry. The pulse transformer subunit 30 has a transformer T1. The switch control chip U1 controls the duty cycle of the primary winding of transformer T1, thereby enabling the secondary winding of transformer T1 to output a corresponding voltage. The voltage output from the secondary winding of transformer T1 is used to power other circuits or electronic devices. A common-mode rejection capacitor, namely two capacitors CY1 and CY1 connected in series, is also provided between the primary and secondary windings of transformer T1 in the pulse transformer subunit. The rectifier unit 40 is electrically connected between the AC power supply unit 10 and the DC power supply unit, and the rectifier unit 40 is a rectifier bridge DB1.

[0020] The zero-crossing detection unit 50 is equipped with an electronic switch QZ1, an optocoupler UZ1, and a zero-crossing signal detection circuit. The control terminal of the electronic switch QZ1 is electrically connected to the live wire ACL. The transformer T1 in the pulse transformer subunit 30 is equipped with an auxiliary winding (between terminals 4 and 5 of the transformer T1). The output terminal of the auxiliary winding is connected in series with the input side of the optocoupler UZ1 and the electronic switch QZ1 and then grounded. The zero-crossing signal detection circuit is electrically connected to the output side of the optocoupler. Whenever the light-emitting diode on the input side of the optocoupler UZ1 lights up once, the zero-crossing signal detection circuit can detect the signal generated on the output side of the optocoupler UZ1.

[0021] like Figure 2 As shown, in this embodiment, a first diode D11 and a first current-limiting resistor RZ3 are provided between the output terminal of the auxiliary winding of transformer T1 and the input side of optocoupler UZ1. The positive terminal of the first diode D11 is electrically connected to the output terminal of the auxiliary winding of transformer T1, and the first current-limiting resistor RZ3 is electrically connected to the negative terminal of the first diode D11. The first diode D11 and the first current-limiting resistor RZ3 protect the electronic switch QZ1.

[0022] In addition, in this embodiment, the electronic switch QZ1 is an NPN transistor. A second diode D10 and a second current-limiting resistor are provided between the live wire ACL and the base of the transistor. The second current-limiting resistor includes two resistors RZ4 and RZ5 connected in series. The positive terminal of the second diode D10 is electrically connected to the live wire ACL, and the resistors RZ4 and RZ5 are electrically connected to the negative terminal of the second diode D10. The second diode D10, resistors RZ4 and RZ5 protect the electronic switch QZ1.

[0023] Furthermore, such as Figure 2 As shown, the DC power supply unit in this low-power DC power supply unit with isolated zero-crossing circuit also includes a first voltage regulator circuit 60 electrically connected to the output terminal of the rectifier unit 40. The first voltage regulator circuit 60 outputs a first DC voltage source with a voltage of 300V. The input terminal of the primary winding of the transformer T1 in the pulse transformer subunit 30 is electrically connected to the positive terminal of the first DC voltage source, and the output terminal of the primary winding of the transformer T1 is electrically connected to the negative terminal of the first DC voltage source via the switch control subunit 20.

[0024] like Figure 2 As shown, the DC power supply unit also includes a second voltage regulator circuit 70 electrically connected to the secondary winding of the pulse transformer subunit 30. The second voltage regulator circuit 70 outputs a second DC voltage source, which is a 5V DC voltage. This 5V DC voltage can power the zero-crossing signal detection circuit. The zero-crossing signal detection circuit includes a first voltage divider resistor RZ1. The second DC voltage source (5V DC voltage) is grounded through the first voltage divider resistor RZ1 and the output side of the optocoupler UZ1. An RC filter circuit (composed of a series resistor RZ2 and a capacitor CZ2) is connected in parallel on the output side of the optocoupler UZ1. A zero-crossing signal monitoring point is set in the RC filter circuit, which is point B.

[0025] The principle of this low-power and isolated zero-crossing circuit is as follows: (1) Combining Figure 2As shown, when the live wire ACL is in the positive half-cycle, the live wire ACL supplies power to the base (B-terminal) of transistor QZ1 through the second diode D10, resistors RZ4 and RZ5, and transistor QZ1 is turned on. The voltage +VPP input from the auxiliary winding of transformer T1 supplies power to the LED on the input side of optocoupler UZ1 through the first diode D11 and resistor RZ3, and the transistor on the output side of optocoupler UZ1 is turned on. The voltage at point A in the zero-crossing signal detection circuit is low. (2) When the live wire ACL is in the negative half-cycle, transistor QZ1 is not turned on, and the LED on the input side of optocoupler UZ1 does not form a circuit. Therefore, the transistor on the output side of optocoupler UZ1 is also not turned on, and the voltage at point A in the zero-crossing signal detection circuit is high. By repeating the above steps (1) and (2), a complete square wave zero-crossing signal can be obtained at point B in the zero-crossing signal detection circuit.

[0026] The low-power and isolated zero-crossing circuit has the following advantages: (1) The low-power and isolated zero-crossing circuit supplies power to the LED inside the input side of the optocoupler UZ1 through the auxiliary winding of transformer T1, instead of directly supplying power to the LED inside the optocoupler UZ1 through the power resistor connected by the live wire ACL, thus effectively reducing power consumption. (2) Directly supplying power to the LED inside the optocoupler UZ1 through the auxiliary winding of transformer T1 in the circuit eliminates the need for additional power supply components such as transformers, reducing circuit cost. (3) Since the current zero-point signal detection circuit supplies power to the LED on the input side of the optocoupler through the live wire ACL, the error is large, resulting in a difference of more than 2 milliseconds between the positive and negative periods of the zero-crossing signal. The low-power and isolated zero-crossing circuit controls the on / off state of the LED on the input side of the optocoupler through an electronic switch, achieving high control accuracy and solving the problem of large positive and negative deviations in zero crossing caused by the current optocoupler isolation. (4) When supplying power to the LED inside the optocoupler through the auxiliary winding of transformer T1, selecting a resistor RZ3 with an appropriate resistance value helps to reduce the standby power consumption of the entire circuit.

[0027] It should be noted that, unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains, and terms such as those defined in a common dictionary should be interpreted as having a meaning consistent with their meaning in the context of the relevant art. It should also be understood that the above is a description of this disclosure and should not be considered as a limitation thereof. Although several exemplary embodiments of this disclosure have been described, those skilled in the art will readily understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of this invention. Therefore, all such modifications are intended to be included within the scope of this disclosure as defined in the claims, and will not be detailed here.

Claims

1. A low-power circuit with isolated zero-crossing, characterized in that, include: An AC power supply unit, which is equipped with a live wire and a neutral wire; A DC power supply unit, which includes a switch control subunit and a pulse transformer subunit, wherein the switch control subunit is electrically connected to the pulse transformer subunit; A rectifier unit, which is electrically connected between the AC power supply unit and the DC power supply unit; The zero-crossing detection unit includes an electronic switch, an optocoupler, and a zero-crossing signal detection circuit. The control terminal of the electronic switch is electrically connected to the live wire. The pulse transformer subunit has an auxiliary winding. The output terminal of the auxiliary winding is connected in series with the input side of the optocoupler and the electronic switch and then grounded. The zero-crossing signal detection circuit is electrically connected to the output side of the optocoupler.

2. The low-power circuit with isolation zero-crossing according to claim 1, characterized in that: A first diode and a first current-limiting resistor are provided between the output end of the auxiliary winding and the input side of the optocoupler.

3. The low-power circuit with isolation zero-crossing according to claim 1, characterized in that: The electronic switch is a transistor, and a second diode and a second current-limiting resistor are provided between the live wire and the base of the transistor.

4. The low-power circuit with isolation zero-crossing according to claim 1, characterized in that: The DC power supply unit includes a first voltage regulator circuit electrically connected to the output terminal of the rectifier unit. The first voltage regulator circuit outputs a first DC voltage source. The input terminal of the primary winding of the pulse transformer subunit is electrically connected to the positive terminal of the first DC voltage source, and the output terminal of the primary winding is electrically connected to the negative terminal of the first DC voltage source via the switch control subunit.

5. The low-power circuit with isolation zero-crossing according to claim 1, characterized in that: The DC power supply unit includes a second voltage regulator circuit electrically connected to the secondary winding of the pulse transformer subunit, and the second voltage regulator circuit outputs a second DC voltage source.

6. The low-power circuit with isolation zero-crossing according to claim 5, characterized in that: The zero-crossing signal detection circuit includes a first voltage divider resistor, the second DC voltage source is grounded through the first voltage divider resistor and the output side of the optocoupler, an RC filter circuit is connected in parallel on the output side of the optocoupler, and a zero-crossing signal monitoring point is provided in the RC filter circuit.

7. The low-power circuit with isolation zero-crossing according to claim 1, characterized in that: A differential mode suppression capacitor is provided between the live wire and the neutral wire of the AC power supply unit; a common mode suppression capacitor is provided between the primary winding and the secondary winding of the pulse transformer subunit.

8. The low-power circuit with isolation zero-crossing according to claim 1, characterized in that: The rectifier unit is a rectifier bridge.

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