High-precision low-cost zero-cross detection circuit
By using a bridge rectifier circuit with two voltage divider resistors and an optocoupler to drive the transistor, the problems of low accuracy and high cost in existing zero-crossing detection circuits are solved, achieving high-precision and low-cost zero-crossing detection.
Patent Information
- Application Number
- CN202423191000.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-24
- Publication Date
- 2025-12-23
- Estimated Expiration
- 2034-12-24
AI Technical Summary
In the existing technology, zero-crossing detection circuits of the resistor voltage divider type have low accuracy and high device temperature, while zero-crossing detection circuits of the sampling chip type have high cost.
By employing two voltage divider resistors and optocouplers, combined with a bridge rectifier circuit, optocoupler driving transistors, and filter capacitors, high-precision zero-crossing detection is achieved, avoiding the use of chips.
It achieves high-precision zero-crossing detection, with low device temperature rise, thus reducing product costs.
Smart Images
Figure CN223711701U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to zero voltage detection technical field especially relates to a high accuracy low cost zero crossing detection circuit. BACKGROUND
[0002] The intelligent capacitor is a kind of capacitor applied in power system, and the intelligent capacitor integrates modern measurement and control, power electronics, network communication, automation control and advanced technologies such as power capacitor, changes the controller technology of traditional reactive power compensation device and the switching technology of the switching capacitor using backward mechanical contactor or mechatronic switch, changes the bulky and heavy structure mode of traditional reactive power compensation device, so that the new generation of low-voltage reactive power compensation device has better compensation effect, smaller size and lower power consumption, and therefore is widely applied.
[0003] The basic functions of the intelligent capacitor include: storing electric energy to reduce power transmission loss, adjusting voltage and reactive power of power system, and improving power factor of system.The service life of capacitor influences the stability of product, and the capacitor is switched in at the time when voltage is zero, and there is no inrush current when switched at zero voltage, which can slow down the capacity attenuation of capacitor, prolong the service life of product and ensure the reliability of product.How to accurately detect the moment of voltage zero crossing is the key to ensure capacitor switching.Currently, the zero crossing detection circuit scheme of resistance voltage division type on the market has the problems of low precision and high device temperature rise, and although the zero crossing detection circuit scheme of sampling chip type can realize high precision, it has the problem of high cost, so the applicant proposes a solution of high-precision low-cost zero-crossing detection circuit. SUMMARY
[0004] The utility model discloses a high-precision low-cost zero-crossing detection circuit, which has high detection precision, low device temperature rise and low product cost.
[0005] The utility model discloses a high-precision low-cost zero-crossing detection circuit, which has high detection precision, low device temperature rise and low product cost.
[0006] A high-precision low-cost zero-crossing detection circuit, which comprises two paths of voltage dividing resistors and a photoelectric coupler U1, one path of voltage dividing resistors R3, R4 and R5 is connected in series and then connected to a line UL of a tertiary side of a voltage transformer, and another path of voltage dividing resistors R6, R7 and R8 is connected in series and then connected to a line UN of a secondary side of the voltage transformer; the UL end is connected to the resistors R3, R4 and R5 in sequence, the resistor R5 is connected to diodes D1 and D5, the UN end is connected to the resistors R6, R7 and R8 in sequence, the resistor R8 is connected to diodes D2 and D6, and the diodes D1, D2, D5 and D6 form a bridge rectifier resistor.
[0007] The input end of the photoelectric coupler U1 is connected with the capacitor C1 and the resistor R10 respectively, the capacitor C1 is connected with the photoelectric coupler U1 in parallel, the capacitor C1 is connected with the collector of the triode Q1 and one end of the resistor R10 respectively, the base of the triode Q1 is connected with the emitter of the triode Q2; one end of the resistor R1 is connected with the base of the triode Q2, the resistor R1 is the driving current limiting resistor of the triode Q2, the other end of the resistor R1 is connected with one end of the diode D2; the output end of the photoelectric coupler U1 is connected with the resistor R2 respectively, the resistor R2 is the pull-up resistor of the output of the photoelectric coupler U1; the output end of the photoelectric coupler U1 is the Vout end.
[0008] The one end of the capacitor C3 is connected with the diode D3, the diode D3 is connected with the UL end, and the diode D3 is used for preventing reverse.
[0009] The emitter of the triode Q1 is connected with the stabilizing tube D4, the stabilizing tube D4 is connected with the capacitor C3 in parallel, and the stabilizing tube D4 is used for setting the charging voltage size of the capacitor C3.
[0010] The collector of the triode Q2 is connected with one end of the resistor R9, the other end of the resistor R9 is connected with one end of the diode D6, and the resistor R9 is used for providing a loop for the triode Q2.
[0011] The output end of the photoelectric coupler U1 is also connected with the capacitor C2, the capacitor C2 is grounded, and the capacitor C2 is used as the Vout filter capacitor.
[0012] Compared with the prior art, the high-precision low-cost zero-crossing detection circuit has the beneficial effects that:
[0013] The high-precision low-cost zero-crossing detection circuit is mainly used for zero-crossing detection of a grid-side voltage, the capacitor C1 and the capacitor C3 are connected with the photoelectric coupler U1 in parallel, the capacitor C3 is connected with the stabilizing tube D4 in parallel, the triode Q1 is used as the driving of the photoelectric coupler U1, and the triode Q2 provides a driving loop for the triode Q1; when being at a zero point, the output Vout is a low level, and when being at a positive half cycle or a negative half cycle, the output Vout is always a high level, so that high-precision zero-crossing detection can be realized, the temperature rise of the device is not high, and a chip does not need to be used, so that the product cost can be reduced. BRIEF DESCRIPTION OF DRAWINGS
[0014] Figure 1 It is a circuit schematic diagram of the utility model.
[0015] Figure 2 It is a charging path schematic diagram when the UL of the utility model is greater than the UN.
[0016] Figure 3The discharge path schematic diagram when UL is equal to UN of the utility model.
[0017] Figure 4 The charging path schematic diagram when UL is less than UN of the utility model.
[0018] Figure 5 The cycle detection flow schematic diagram of the utility model. DETAILED DESCRIPTION
[0019] For better understanding of the technical scheme of the utility model, the following will be combined with relevant drawings to make detailed description. It should be understood that the following specific embodiments are not used to limit the specific implementation manners of the technical scheme of the utility model, and they are only implementation manners that can be adopted by the technical scheme of the utility model. It should be first stated that the expression about the position relationship of each component in this paper, such as A component is located above B component, is based on the expression of the relative position of each component in the drawing, and is not used to limit the actual position relationship of each component.
[0020] Embodiment 1:
[0021] Referring to Figures 1-5 , Figure 1 A circuit schematic diagram of a high-precision low-cost zero-crossing detection circuit of the utility model is drawn. As shown in the figure, the high-precision low-cost zero-crossing detection circuit related to the utility model comprises two-way voltage division resistors and a photoelectric coupler U1, one-way voltage division resistors R3, R4 and R5 are connected in series and then connected with the line UL end of the three-side voltage transformer, and the other way voltage division resistors R6, R7 and R8 are connected in series and then connected with the line UN end of the two-side voltage transformer.
[0022] The UL end is connected with resistors R3, R4 and R5 in sequence, the resistor R5 is connected with diodes D1 and D5, the UN end is connected with resistors R6, R7 and R8 in sequence, the resistor R8 is connected with diodes D2 and D6, and the diodes D1, D2, D5 and D6 form a bridge rectifier resistor.
[0023] The input end of the photoelectric coupler U1 is connected with a capacitor C1 and a resistor R10 respectively, the capacitor C1 is connected in parallel with the photoelectric coupler U1, the capacitor C1 is connected with the collector of a triode Q1 and one end of the resistor R10 respectively, the base of the triode Q1 is connected with the emitter of a triode Q2, the emitter of the triode Q1 is connected with a voltage stabilizing tube D4, the voltage stabilizing tube D4 is connected in parallel with a capacitor C3, one end of the capacitor C3 is connected with a diode D3, and the diode D3 is connected to the UL end.
[0024] One end of the resistor R1 is connected with the base of the triode Q2, and the other end of the resistor R1 is connected with one end of the diode D2; one end of the resistor R9 is connected with the collector of the triode Q2, and the other end of the resistor R9 is connected with one end of the diode D6.
[0025] The output end of the photoelectric coupler U1 is connected with the resistance R2 and the capacitor C2, respectively, the output end of the photoelectric coupler U1 is the Vout end, and the capacitor C2 is grounded.
[0026] The resistances R3, R4, R5, R6, R7 and R8 are only used for sharing voltage and have no accuracy requirement; the bridge rectifier resistance composed of the diodes D1, D2, D5 and D6 ensures that the zero point of the positive half cycle and the negative half cycle can be detected; the diode D3 is used for preventing reverse; and the voltage stabilizing tube D4 is used for setting the charging voltage size of the capacitor C3.
[0027] The triode Q1 is mainly used for driving the photoelectric coupler U1; the triode Q2 is mainly used for providing a driving loop for the triode Q1;
[0028] The resistance R1 is a driving current-limiting resistance of the triode Q2; the resistance R9 mainly provides a loop for the triode Q2; the capacitor C1 is used for filtering; the resistance R10 is a driving current-limiting resistance of the photoelectric coupler U1; the resistance R2 is an up pull resistance of the photoelectric coupler U1 output; and the capacitor C2 is used for filtering the Vout output capacitor.
[0029] Taking the LN fire line zero line as an example, when the LN fire line zero line is not in the zero point state, the Vout output is high level; on the contrary, when it is in the zero point moment, the Vout output is low level. Therefore, the detection circuit of the embodiment 1 can efficiently and quickly measure the zero point moment through the high and low level states of the Vout.
[0030] Referring to Figure 2 , Figure 2 The charging path schematic diagram of the UL greater than the UN state of the embodiment 1 is drawn. As shown in the figure, taking the LN fire line zero line as an example, when the UL is greater than the UN state, the waveform is in the positive half cycle, at this time, the capacitor C3 is charged, and the charging path is path ① in Figure 2 .
[0031] From the UL to the resistance R3, the resistance R4, the resistance R5, the diode D1, the diode D3, the capacitor C3, the voltage stabilizing tube D4 in parallel, the diode D6, the resistance R8, the resistance R7, the resistance R6 and the UN.
[0032] Since the photoelectric coupler U1 is not driven, the output Vout is always high level in this state.
[0033] Referring to Figure 3 , Figure 3 The discharge path schematic diagram of the UL equal to the UN state of the embodiment 1 is drawn. As shown in the figure, when the UL=UN state, the waveform is in the zero point moment, at this time, the capacitor C3 is discharged, and the discharge path is path ② in Figure 3 .
[0034] (1) from capacitor C3→ base b and emitter e of transistor Q1→ base b and emitter e of transistor Q2→ resistor R1;
[0035] (2) from capacitor C3→ emitter e and collector c of transistor Q1→ photodiode (1 pin 2 pin) of optocoupler U1→ resistor R10.
[0036] The optocoupler U1 is in the discharge circuit, the optocoupler U1 is driven, the output Vout of the optocoupler U1 is pulled low, and the output is low;
[0037] That is, when not in zero state, the optocoupler U1 is not driven, and the output Vout is high; when in zero point, the optocoupler U1 is driven, and the output Vout is low.
[0038] Referring to Figure 4 , Figure 4 The charging path diagram when UL is less than UN in the embodiment 1 is drawn. As shown in the figure, when UL is less than UN, the waveform is in the negative half cycle, at this time, the capacitor C3 is charged, and the charging path is Figure 4 path ③ in the figure:
[0039] From UN→ resistor R6→ resistor R7→ resistor R8→ diode D2→ diode D3→ capacitor C3 and zener D4→ diode D5→ resistor R5→ resistor R4→ resistor R3→ UL.
[0040] Since the optocoupler U1 is not driven, the output Vout is always high in this state.
[0041] Referring to Figure 5 , Figure 5 The cycle detection flowchart of the embodiment 1 is drawn. As shown in the figure, the cycle detection flowchart of the zero-crossing detection circuit of the embodiment 1 is summarized:
[0042] When in the positive half cycle state, the capacitor C3 is charged to a set value, the optocoupler U1 is not driven, and the output Vout is always high;
[0043] When in the zero point, the capacitor C3 is discharged, the optocoupler U1 is driven, and the output Vout is low;
[0044] When in the negative half cycle state, the capacitor C3 is charged to a set value, the optocoupler U1 is not driven, and the output Vout is always high;
[0045] That is, when in the zero point, the output Vout is low, and when in the positive half cycle or the negative half cycle, the output Vout is always high.
[0046] Working principle:
[0047] The utility model provides a kind of high-precision low-cost zero-crossing detection circuit, mainly for the zero-crossing detection of net side voltage, with LN live wire zero line as an example, when LN live wire zero line is not in zero point state, Vout output high level;In zero point moment, Vout output low level.Through the high-low state of Vout, zero point moment can be clearly understood.
[0048] The above is only the specific application example of the utility model, and does not constitute any limitation on the protection scope of the utility model. Any technical solution formed by equivalent transformation or equivalent replacement falls within the protection scope of the utility model.
Claims
1. A high-precision low-cost zero-crossing detection circuit, characterized by: It includes two-way voltage divider and photoelectric coupler U1, one-way voltage divider R3, R4 and R5 are connected in series and then connected with line UL end of voltage transformer three side, another way voltage divider R6, R7 and R8 are connected in series and then connected with line UN end of voltage transformer secondary side; UL end is connected with resistance R3, R4 and R5 in turn, resistance R5 is connected with diode D1 and D5, UN end is connected with resistance R6, R7 and R8 in turn, resistance R8 is connected with diode D2 and D6, diode D1, D2, D5 and D6 form a bridge rectifier resistance; The input end of photoelectric coupler U1 is connected with capacitor C1 and resistance R10 respectively, capacitor C1 is connected with photoelectric coupler U1 in parallel, capacitor C1 is connected with the collector of triode Q1 and one end of resistance R10 respectively, the base of triode Q1 is connected with the emitter of triode Q2; one end of resistance R1 is connected with the base of triode Q2, resistance R1 is the drive current limiting resistance of triode Q2, the other end of resistance R1 is connected with one end of diode D2; the output end of photoelectric coupler U1 is connected with resistance R2 respectively, resistance R2 is the pull-up resistance of photoelectric coupler U1 output; the output end of photoelectric coupler U1 is connected with Vout end.
2. A high precision low cost zero crossing detection circuit according to claim 1, characterized in that: The emitter of triode Q1 is connected with stabilizing tube D4, stabilizing tube D4 is connected with capacitor C3 in parallel, stabilizing tube D4 is used for setting the charging voltage size of capacitor C3.
3. A high precision low cost zero crossing detection circuit as claimed in claim 2, characterized in that: One end of capacitor C3 is connected with diode D3, diode D3 is connected with UL end, diode D3 is used for preventing reverse.
4. The high-precision low-cost zero-crossing detection circuit of claim 1, wherein: The collector of triode Q2 is connected with one end of resistance R9, the other end of resistance R9 is connected with one end of diode D6, resistance R9 is used for providing loop for triode Q2.
5. The high precision low cost zero-crossing detection circuit of claim 1, wherein: The output end of photoelectric coupler U1 is also connected with capacitor C2, capacitor C2 is grounded, capacitor C2 is used for outputting Vout filter capacitor.