Power grid voltage zero-cross detection circuit, control circuit and detection method
By using a multi-stage discharge circuit and a zero-crossing comparison circuit in the grid voltage zero-crossing detection circuit, the problems of high power consumption, high cost and large detection delay in the prior art are solved, and high accuracy, low power consumption and high reliability of grid voltage zero-crossing detection is achieved.
Patent Information
- Application Number
- CN202411750965.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-29
- Publication Date
- 2025-03-28
AI Technical Summary
The existing grid voltage zero-crossing detection circuit has problems such as high power consumption, high cost and large detection delay, and is low in reliability, which makes it easy to damage the micro computing unit (MCU).
The grid voltage zero-crossing detection circuit adopts a multi-stage drain circuit, is coupled to the power grid through a rectifier circuit, and uses the first drain circuit and the second drain circuit to provide different drain currents, and is detected in combination with the zero-crossing comparison circuit to eliminate the delay effect of parasitic capacitors.
Improves the accuracy of zero crossing detection, reduces power consumption, reduces costs, and enhances the reliability of the circuit and avoids MCU damage.
Smart Images
Figure CN119716223A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of electronics, and specifically but not limited to, relates to a grid voltage zero-crossing detection circuit and a control circuit and a zero-crossing detection method. Background Art
[0002] Zero-crossing detection of industrial frequency AC voltage in power grids has important application value, including but not limited to thyristor on-off control, relay on-off control, grid voltage frequency detection, microcomputer unit (MCU) timing, etc.
[0003] Existing zero-crossing detection circuits are implemented by discrete devices. The following are the two most commonly used zero-crossing detection circuits. Figure 1 The first commonly used zero-crossing detection circuit is shown, which is realized by a resistor voltage divider network and a transistor. When the AC signal input to the zero-crossing detection circuit is a positive half-wave, the transistor D1 is turned on, and the zero-crossing signal ZERO outputs a low level; when the input is 0 or a negative half-wave, D1 is cut off, and ZERO is a high level. This detection method has relatively high reliability, but when the positive half-wave is input, the voltage divider network and the branch where the transistor D1 is located are always consuming energy, and the power consumption is large. Increasing the resistance can reduce the loss but will sacrifice the detection accuracy. In addition, this method requires additional transistors and some resistor-capacitor networks, which is costly.
[0004] Figure 2 Another zero-crossing detection circuit is shown, which is implemented by a clamping circuit in the MCU. When the AC input is a positive half-wave and is greater than the internal clamping voltage, the zero-crossing signal ZERO is a high level (i.e., the clamping voltage), and when the input is less than 0, the zero-crossing signal ZERO is a low level. This circuit is relatively simple and low in cost, but the delay of zero-crossing detection is large, and the reliability is low, which can easily damage the MCU.
[0005] In view of this, it is necessary to provide a new structure or control method to solve at least part of the above problems. Summary of the invention
[0006] At least in view of one or more problems in the background technology, the present invention proposes a zero-crossing detection circuit for detecting the zero-crossing of a power grid voltage, a control circuit including the zero-crossing detection circuit, and a zero-crossing detection method.
[0007] According to one aspect of the present invention, a grid voltage zero-crossing detection circuit is proposed. The zero-crossing detection circuit has a high-voltage pin, which is coupled to the grid through a rectifier circuit. The zero-crossing detection circuit includes: a first discharge circuit, whose input end is coupled to the high-voltage pin, and when the first discharge circuit is turned on, a first discharge current is provided to the high-voltage pin, and the first discharge current flows from the high-voltage pin to the first discharge circuit; a second discharge circuit, whose input end is coupled to the input end of the first discharge circuit, and when the second discharge circuit is turned on, a second discharge current is provided to the high-voltage pin, and the second discharge current flows from the high-voltage pin to the second discharge circuit, wherein the second discharge current is greater than the first discharge current; and a zero-crossing comparison circuit, which is coupled to the high-voltage pin, and the zero-crossing comparison circuit compares a voltage sampling signal representing the voltage on the high-voltage pin with a zero-crossing reference signal, and the zero-crossing detection circuit outputs a zero-crossing detection signal based on the comparison of the zero-crossing comparison circuit.
[0008] In one embodiment, the first discharge circuit includes a first current source and a unidirectional conducting device coupled in series, the first end of the first current source and the unidirectional conducting device coupled in series is coupled to a high voltage pin, and the second end of the first current source and the unidirectional conducting device coupled in series is coupled to a power supply pin, for powering the circuit.
[0009] In one embodiment, the second discharge circuit includes a switch and a second current source coupled in series, a second end of the second discharge circuit is coupled to a reference ground, and the switch is turned on during at least a partial falling phase of the voltage on the high voltage pin.
[0010] In one embodiment, when the voltage on the high voltage pin is less than a threshold, the switch is turned on.
[0011] In one embodiment, when the zero-crossing detection signal indicates a zero-crossing, the switch is closed.
[0012] In one embodiment, the zero-crossing detection circuit further includes a high-voltage field effect transistor, wherein the drain of the high-voltage field effect transistor is coupled to the high-voltage pin, and the source of the high-voltage field effect transistor is coupled to the input end of the first discharge circuit, the input end of the second discharge circuit and the input end of the zero-crossing comparison circuit.
[0013] In one embodiment, the second discharge circuit includes: a switch, a first end of the switch is coupled to the source of the junction field effect transistor; a second current source, an input end of the second current source is coupled to the second end of the switch, and an output end of the second current source is coupled to the reference ground; a second comparison circuit, a first input end of the second comparison circuit is coupled to the high voltage pin, and a second input end of the second comparison circuit receives a threshold signal; and a discharge control circuit, a first input end of the discharge control circuit is coupled to the output end of the second comparison circuit, a second input end of the discharge control circuit receives a zero-crossing detection signal, and an output end of the discharge control circuit is coupled to the control end of the switch.
[0014] In one embodiment, the zero-crossing detection circuit is integrated and manufactured on the same semiconductor substrate.
[0015] According to another aspect of the present invention, a control circuit is provided, comprising the zero-crossing detection circuit as described in any one of the above embodiments.
[0016] In one embodiment, the first discharge circuit shares a power supply circuit with the control circuit, and the first discharge circuit is used to supply power to the control circuit.
[0017] According to another aspect of the present invention, a detection method for detecting a zero-crossing point of a grid voltage is proposed, comprising: rectifying the grid voltage to obtain a rectified voltage at a high-voltage pin; discharging current from the high-voltage pin with a first current; discharging current from the high-voltage pin with a second current, wherein the first current is less than the second current; and comparing the rectified voltage after current discharge with a zero-crossing reference signal to obtain a zero-crossing detection signal.
[0018] In one embodiment, when the rectified voltage drops to less than a first threshold, the second current starts to be discharged, and when the zero-crossing detection signal indicates zero crossing, the second current stops discharging, and when the rectified voltage is greater than the second threshold, the first current continues to be discharged, wherein the first threshold is greater than the second threshold.
[0019] The zero-crossing detection circuit, control circuit and zero-crossing detection method proposed in the present invention can eliminate the delay effect of parasitic capacitance on the signal after grid voltage rectification, improve the accuracy of zero-crossing detection, and can share the power supply circuit and use the discharge current to power the circuit at the same time, which has high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings are used to provide a further understanding of the present invention and are used together with the description to explain the embodiments of the present invention, but do not constitute a limitation of the present invention. In the accompanying drawings:
[0021] Figure 1 A commonly used zero-crossing detection circuit is shown;
[0022] Figure 2 Another zero-crossing detection circuit is shown;
[0023] Figure 3 A zero-crossing detection circuit according to an embodiment of the present invention is shown;
[0024] Figure 4 A control circuit including a zero-crossing detection circuit according to a specific embodiment of the present invention is shown;
[0025] Figure 5 A waveform diagram according to an embodiment of the present invention is shown;
[0026] Figure 6A flowchart of a method for detecting a zero-crossing point of a power grid voltage according to an embodiment of the present invention is shown. DETAILED DESCRIPTION
[0027] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.
[0028] The description in this section is only for several typical embodiments, and the present invention is not limited to the scope of the embodiments. The combination of different embodiments, the mutual replacement of some technical features in different embodiments, and the mutual replacement of the same or similar prior art means with some technical features in the embodiments are also within the scope of the description and protection of the present invention.
[0029] "Coupled" or "connected" in the specification includes both direct connection and indirect connection. Indirect connection is a connection through an intermediate medium, such as a connection through an electrical conductive medium such as a conductor, wherein the electrical conductive medium may contain parasitic inductance or parasitic capacitance, or a connection through an intermediate circuit or component described in the embodiments in the specification; indirect connection may also include a connection through other active or passive devices on the basis of achieving the same or similar functions, such as a connection through circuits or components such as switches, signal amplification circuits, and follower circuits. "Multiple" or "many" means two or more.
[0030] Figure 3A zero-crossing detection circuit 30 according to an embodiment of the present invention is shown. The zero-crossing detection circuit 30 has a high-voltage pin HV, which is coupled to the power grid through a rectifier circuit 31, and generates a rectified voltage Vhv based on the AC input voltage ACIN of the AC power grid. The zero-crossing detection circuit provides a zero-crossing detection signal ZERO based on the rectified voltage Vhv on the high-voltage pin HV. On the high-voltage pin HV, a parasitic capacitor Cp exists due to the influence of the rectifier circuit 31 and the zero-crossing detection circuit 30. The parasitic capacitor Cp makes the waveform of the rectified voltage Vhv lag behind the AC input voltage ACIN, which will cause a delay in the zero-crossing detection time and affect subsequent control. In order to obtain a more accurate zero-crossing detection point, the zero-crossing detection circuit in the present invention adopts a multi-stage discharge circuit, and by discharging the current of the high-voltage pin, the rectified voltage Vhv drops faster, eliminating the detection delay caused by the parasitic capacitor Cp. At the same time, in order to reduce the power consumption of the discharge circuit, the embodiment of the present invention includes two discharge circuits, namely a first discharge circuit 301 and a second discharge circuit 302. The first discharge circuit 301 adopts a lower discharge current, which can be optionally used to discharge the current of the high-voltage pin for a longer time, gently correct the waveform of the rectified voltage Vhv, and reduce the delay. The second discharge circuit 302 adopts a higher discharge current, and quickly corrects the rectified voltage in the zero-crossing stage, so that the rectified voltage Vhv at the zero-crossing detection point is close to the actual absolute value of the grid voltage. The input end of the first discharge circuit 301 is coupled to the high-voltage pin HV, and when the first discharge circuit 301 is turned on, the first discharge current Ihv1 is provided to the high-voltage pin, and the first discharge current Ihv1 flows from the high-voltage pin to the first discharge circuit 301. The input end of the second discharge circuit 302 is coupled to the input end of the first discharge circuit 301, and is coupled in parallel with the first discharge circuit. When the second discharge circuit 302 is turned on, the second discharge current Ihv2 is provided to the high-voltage pin HV, and the second discharge current Ihv2 flows from the high-voltage pin HV to the second discharge circuit 302. Wherein the second discharge current Ihv2 is greater than the first discharge current Ihv1. In one embodiment, the rectifier circuit 31 is a full-wave rectifier circuit, and in each half power frequency cycle, the first discharge circuit 301 and the second discharge circuit 302 are each turned on once. In one embodiment, the rectifier circuit 31 is a half-wave rectifier circuit, and in one power frequency cycle, the first discharge circuit 301 and the second discharge circuit 302 are each turned on once. Preferably, under normal working conditions, the average turn-on time length of the first discharge circuit 301 is greater than the average turn-on time length of the second discharge circuit 302. In this way, the signal delay caused by parasitic capacitance can be effectively eliminated, and the flow time of the larger current Ihv2 is reduced, so that the overall loss of the system is low.The zero-crossing detection circuit 30 further includes a zero-crossing comparison circuit 303, whose first input terminal is coupled to the high-voltage pin HV. The zero-crossing comparison circuit 303 compares the voltage sampling signal Vhv2 representing the voltage Vhv on the high-voltage pin HV with the zero-crossing reference signal Vth to provide a zero-crossing detection signal ZERO. The zero-crossing reference signal Vth is a smaller reference signal close to zero. In the illustrated embodiment, when the voltage sampling signal Vhv2 of the rectified voltage after waveform correction by the discharge circuit is less than the corresponding reference signal Vth, the zero-crossing comparison circuit 303 outputs a high-level zero-crossing detection signal, and when the rectified voltage sampling signal Vhv2 is greater than the corresponding reference signal Vth, the zero-crossing comparison circuit 303 outputs a low-level zero-crossing detection signal. In one embodiment, there is a resistor voltage divider circuit between the rectifier circuit 31 and the zero-crossing comparison circuit 303, which is used to divide the rectified voltage Vhv output by the rectifier circuit to obtain the voltage sampling signal Vhv2. In another embodiment, a switch is provided between the rectifier circuit 31 and the zero-crossing comparison circuit 303, which is used for selective conduction, and the voltage sampling signal Vhv2 reflecting the partial waveform of the rectified voltage Vhv is input into the zero-crossing comparison circuit 303. The zero-crossing detection signal ZERO can be a high-low level signal, and when the level of the signal ZERO is switched, it indicates that the grid voltage crosses the zero point. For example, at. Figure 3 In the illustrated embodiment, when the rectifier circuit 31 is a half-wave rectifier circuit, the corresponding zero-crossing detection signal ZERO is a high-low level signal. When the signal ZERO level switches, it indicates that the grid voltage passes through zero. In another embodiment, the rectifier circuit 31 is a full-wave rectifier circuit, and the zero-crossing comparison circuit 303 outputs a high-level pulse signal. When the grid voltage passes through zero, the zero-crossing comparison circuit 303 outputs a high-level pulse. The zero-crossing detection circuit may further include a signal conversion circuit for converting a high-level pulse into a zero-crossing detection signal of a high-low level signal. The zero-crossing detection signal ZERO may also be a pulse signal. When the zero-crossing detection signal ZERO outputs a pulse signal, it indicates that the grid voltage passes through zero. For example, in Figure 3 In the illustrated embodiment, when the rectifier circuit 31 is a full-wave rectifier circuit, the corresponding zero-crossing detection signal ZERO is a high-level pulse signal.
[0031] Preferably, Figure 3 The zero-crossing detection circuit shown is integrated on the same semiconductor substrate, which has a high degree of integration and can provide accurate zero-crossing detection.
[0032] Figure 4A control circuit 40 including a zero-crossing detection circuit according to a specific embodiment of the present invention is shown. In this embodiment, the zero-crossing detection circuit 40 shares a power supply circuit in the control circuit. The power supply circuit includes a power supply control switch 43, preferably a high-voltage field effect transistor 43, which is used to selectively conduct according to the voltage Vhv on the high-voltage pin HV, and the power supply circuit further includes a first discharge circuit of the zero-crossing detection circuit. In the illustrated embodiment, the high-voltage field effect transistor includes a junction field effect transistor JFET, wherein the drain of the high-voltage field effect transistor 43 is coupled to the high-voltage pin HV, the control end of the high-voltage field effect transistor 43 is grounded, and the output end of the high-voltage field effect transistor 43 is used to couple the input end of the first discharge circuit, the input end of the second discharge circuit and the input end of the zero-crossing comparison circuit 403. The high-voltage field effect transistor 43 can also use other types of power switches for selective conduction to form a rectified voltage Vhv2 that reflects a partial stage of the rectified voltage Vhv, or a voltage sampling signal Vhv2, to provide the required power supply energy and zero-crossing detection for the subsequent circuit. In the illustrated embodiment, the output end of the first discharge circuit in the zero-crossing detection circuit is used to provide power supply for other circuits in or outside the control circuit 40. The output end of the first discharge circuit can be coupled to the power supply pin AVDD of the control circuit 40 / zero-crossing detection circuit 40. The power supply pin AVDD can be externally coupled to a capacitor. The first discharge circuit includes a first current source 411 and a unidirectional conduction device 412 coupled in series, wherein the first end of the first current source 411 and the unidirectional conduction device 412 coupled in series is coupled to the high-voltage pin HV through a junction field effect transistor JFET, and the second end of the first current source 411 and the unidirectional conduction device 412 coupled in series is coupled to the power supply pin AVDD, which is used to power the internal and / or external circuits. When the rectified voltage Vhv2 is greater than the power supply pin AVDD voltage, the unidirectional conduction device 412 is turned on, that is, the first discharge circuit is turned on, and a discharge path is provided for the high-voltage pin HV through the first discharge circuit, and power is supplied to the circuit at the power supply pin AVDD. At the same time, the distortion problem of the voltage Vhv2 caused by the parasitic capacitance Cp2 at the source end of the high-voltage field effect tube 43 can also be eliminated, making the zero-crossing detection more accurate. The second discharge circuit includes a switch 421 and a second current source 422 coupled in series, and the switch 421 is used to control the conduction of the second current source 422 when the rectified voltage Vhv meets the set condition, that is, the conduction of the second discharge circuit, which is used to make a larger current Ihv2 flow from the high-voltage pin HV to the inside of the zero-crossing detection circuit 40 and to the reference ground GND, so that the rectified voltage Vhv2 is quickly reduced, and the delay effect of the parasitic capacitance on the rectified voltage Vhv is eliminated, and the actual amplitude of the grid voltage ACIN is close to the actual zero-crossing value of the grid voltage ACIN. In one embodiment, the switch 421 is controlled to be turned on for a short period of time during the falling stage of the voltage Vhv on the high-voltage pin HV. In one embodiment, when the voltage Vhv on the high-voltage pin HV is less than a threshold, the switch 421 is turned on.In another embodiment, after a predetermined time after the high-voltage field effect transistor 43 is turned on, the switch 421 is turned on. In the illustrated embodiment, the second discharge circuit includes a switch 421, a second current source 422, a voltage sampling circuit 423, a second comparison circuit 424, and a discharge control circuit 425. The first end of the switch 421 is coupled to the source of the junction field effect transistor 43; the input end of the second current source 422 is coupled to the second end of the switch 421, and the output end of the second current source 422 is coupled to the reference ground GND. When the switch 421 is turned on, the current in the second current source 422 flows from the high-voltage pin HV to the reference ground, that is, the second discharge circuit is turned on, and the second discharge current Ihv2 is provided to the high-voltage pin HV. The voltage sampling circuit is used to obtain the rectified voltage Vhv on the high-voltage pin HV. In the illustrated embodiment, the voltage sampling circuit 423 includes a resistor divider circuit composed of resistors R1 and R2 and a voltage follower, so that the signal HVs output from the output end of the voltage sampling circuit is proportional to Vhv. In another embodiment, the voltage sampling circuit can sample the voltage Vhv2 at the output end of the power supply control switch 43. The first input end of the second comparison circuit 424 is coupled to the output end of the voltage sampling circuit 423. Since the voltage sampling circuit 423 is used to obtain the voltage on the high-voltage pin HV, the first input end of the second comparison circuit 424 can be regarded as coupled to the high-voltage pin HV for obtaining the voltage on the high-voltage pin HV. The second input end of the second comparison circuit 424 receives the threshold signal Vthb, and the output end of the second comparison circuit 424 is coupled to the first input end of the discharge control circuit 425. When the voltage sampling signal HVs of the high-voltage pin HV provided by the voltage sampling circuit 423 is less than the threshold signal Vthb, the second comparison circuit 424 outputs a valid signal, such as a high-level signal. A first input terminal of the discharge control circuit 425 is coupled to an output terminal of the second comparison circuit 424, a second input terminal of the discharge control circuit 425 receives a zero-crossing detection signal ZERO, an output terminal of the discharge control circuit 425 is coupled to a control terminal of the switch 421, when the voltage on the high-voltage pin HV is less than a threshold voltage, the discharge control circuit 425 controls the switch 421 to be turned on, and a current in the second current source 422 flows from the high-voltage pin HV to the reference ground GND, for quickly reducing the voltage on the high-voltage pin HV, and when the zero-crossing detection signal ZERO is in a valid state, the discharge control circuit 425 controls the switch 421 to be turned off.
[0033] Figure 5A waveform diagram according to an embodiment of the present invention is shown. From top to bottom, they are the AC input voltage ACIN, the rectified voltage Vhv, the zero-crossing detection signal ZERO and the current Ihv flowing through the high-voltage pin HV. This embodiment adopts a half-wave rectifier circuit to obtain a half-wave rectifier signal Vhv. When the difference between the rectified voltage Vhv and the voltage at the output end of the first discharge circuit is greater than the conduction threshold of a unidirectional conducting device such as a diode, the first discharge circuit is turned on, and the current Ihv1 flows from the high-voltage pin HV to the first discharge circuit. Optionally, the current Ihv1 is used to power the control circuit. At time t0, the rectified voltage Vhv on the high-voltage pin HV drops below the threshold, corresponding to Figure 4 Hvs in is lower than Vthb, switch 421 is turned on, the second discharge circuit is turned on, and the current flowing through the high-voltage pin HV is the sum of the first discharge current Ihv1 and the second discharge current, Ihv=Ihv1+Ihv2. When it is detected that the rectified voltage Vhv is lower than the zero-crossing reference signal, the zero-crossing detection signal ZERO outputs a high level and is used to trigger the second discharge circuit to shut down. At time t1, the rectified voltage Vhv gradually increases, the first discharge circuit is turned on, and the current flowing through the high-voltage pin HV is the first discharge current Ihv1, Ihv=Ihv1, until the rectified voltage Vhv drops below the threshold again in the falling stage, the second discharge circuit is turned on again, so that Ihv=Ihv1+Ihv2.
[0034] Figure 6A flow chart of a detection method for detecting a zero-crossing point of a power grid voltage according to an embodiment of the present invention is shown. The detection method for detecting a zero-crossing point of a power grid voltage includes rectifying the power grid voltage ACIN to obtain a rectified voltage Vhv in step 601, and the rectified voltage is input to a high-voltage pin of a circuit. The rectification may be full-wave rectification or half-wave rectification. In step 602, the high-voltage pin is discharged with a first current Ihv1. In one embodiment, as long as the rectified voltage Vhv is greater than the power supply pin terminal voltage of the control circuit and the diode conduction voltage drop, the high-voltage pin is discharged with a first current Ihv1. In another embodiment, when the high-voltage field effect transistor for power supply is turned on, the high-voltage pin is discharged with a first current Ihv1. In step 603, when Vhv is close to zero, it is determined whether a preset condition is met to determine whether Vhv is close to a zero-crossing interval in the falling phase. In one embodiment, the preset condition is that Vhv is less than a preset reference voltage. If the preset conditions are met, the high voltage pin is discharged with the second current Ihv2 in step 604, wherein the first current Ihv1 is less than the second current Ihv2. In step 605, the rectified voltage Vhv after current discharge is compared with the zero-crossing reference signal Vth to obtain a zero-crossing detection signal ZERO. If Vhv is less than the zero-crossing reference signal Vth, the zero-crossing detection signal ZERO in the effective state is output in step 606, indicating that the grid voltage is zero-crossing. In one embodiment, when the rectified voltage Vhv drops to less than the first threshold, the second current Ihv2 is started to be discharged, and when the zero-crossing detection signal ZERO indicates zero crossing, the second current Ihv2 stops discharging, and in the stage where the rectified voltage Vhv is greater than the second threshold, the first current Ihv1 continues to be discharged, wherein the first threshold is greater than the second threshold. The second threshold can be the sum of the voltage at the power supply end of the control circuit and the conduction threshold of the unidirectional conduction device.
[0035] Those skilled in the art should know that the logic controls such as "high level" and "low level", "set" and "reset", "AND gate" and "OR gate", "non-inverting input terminal" and "inverting input terminal" in the logic controls involved in the specification or drawings can be interchanged or changed with each other, and the same function or purpose as the above embodiment can be achieved by adjusting the subsequent logic controls.
[0036] The description and application of the present invention here are illustrative, and it is not intended to limit the scope of the present invention to the above-mentioned embodiments. The effects or advantages involved in the specification may not be reflected in the actual experimental examples due to the uncertainty of specific condition parameters or other factors, and the effects or advantages are not used to limit the scope of the invention. The deformation and change of the embodiments disclosed here are possible, and the replacement of the embodiments and the various equivalent parts are well known to those of ordinary skill in the art. It should be clear to those skilled in the art that the present invention can be implemented in other forms, structures, arrangements, proportions, and with other components, materials and parts without departing from the spirit or essential features of the present invention. Other deformations and changes can be made to the embodiments disclosed here without departing from the scope and spirit of the present invention.
Claims
1. A grid voltage zero-crossing detection circuit, having a high-voltage pin, the high-voltage pin is coupled to the grid through a rectifier circuit, the zero-crossing detection circuit comprising: A first discharge circuit, an input end of which is coupled to the high-voltage pin, and when the first discharge circuit is turned on, a first discharge current is provided to the high-voltage pin, and the first discharge current flows from the high-voltage pin to the first discharge circuit; a second discharge circuit, whose input end is coupled to the input end of the first discharge circuit, and provides a second discharge current to the high voltage pin when the second discharge circuit is turned on, and the second discharge current flows from the high voltage pin to the second discharge circuit, wherein the second discharge current is greater than the first discharge current; and The zero-crossing comparison circuit is coupled to the high-voltage pin. The zero-crossing comparison circuit compares a voltage sampling signal representing the voltage on the high-voltage pin with a zero-crossing reference signal. The zero-crossing detection circuit outputs a zero-crossing detection signal based on the comparison of the zero-crossing comparison circuit.
2. The zero-crossing detection circuit as claimed in claim 1, wherein the first discharge circuit comprises a first current source and a unidirectional conducting device coupled in series, a first end of the first current source and the unidirectional conducting device coupled in series is coupled to a high voltage pin, and a second end of the first current source and the unidirectional conducting device coupled in series is coupled to a power supply pin for powering the circuit.
3. The zero-crossing detection circuit as claimed in claim 1, wherein the second discharge circuit comprises a switch and a second current source coupled in series, a second end of the second discharge circuit is coupled to a reference ground, and the switch is turned on during at least a partial falling phase of the voltage on the high voltage pin. 4 . The zero-crossing detection circuit as claimed in claim 3 , wherein the switch is turned on when the voltage value on the high voltage pin is less than a threshold value. 5 . The zero-crossing detection circuit of claim 4 , wherein when the zero-crossing detection signal indicates a zero crossing, the switch is closed.
6. The zero-crossing detection circuit as claimed in claim 1, further comprising a high-voltage field effect transistor, wherein a drain of the high-voltage field effect transistor is coupled to the high-voltage pin, and a source of the high-voltage field effect transistor is coupled to an input end of the first discharge circuit, an input end of the second discharge circuit and an input end of the zero-crossing comparison circuit.
7. The zero-crossing detection circuit as claimed in claim 6, wherein the second discharge circuit comprises: A switch, wherein a first end of the switch is coupled to a source of the junction field effect transistor; A second current source, an input end of the second current source is coupled to the second end of the switch, and an output end of the second current source is coupled to the reference ground; A second comparison circuit, wherein a first input terminal of the second comparison circuit is coupled to the high voltage pin, and a second input terminal of the second comparison circuit receives a threshold signal; as well as The discharge control circuit has a first input terminal coupled to the output terminal of the second comparison circuit, a second input terminal of the discharge control circuit receives a zero-crossing detection signal, and an output terminal of the discharge control circuit is coupled to the control terminal of the switch. The zero-crossing detection circuit as claimed in claim 1 is integrated and manufactured on the same semiconductor substrate.
9. A control circuit, comprising the zero-crossing detection circuit according to any one of claims 1 to 8. 10 . The control circuit as claimed in claim 9 , wherein the first discharge circuit shares a power supply circuit of the control circuit, and the first discharge circuit supplies power to the control circuit.
11. A method for detecting a zero-crossing point of a power grid voltage, comprising: Rectify the grid voltage to obtain the rectified voltage at the high voltage pin; Discharging the high voltage pin with a first current; Discharging the high voltage pin with a second current, wherein the first current is smaller than the second current; The rectified voltage after current discharge is compared with the zero-crossing reference signal to obtain a zero-crossing detection signal.
12. The detection method as claimed in claim 11, wherein when the rectified voltage drops to less than a first threshold, the second current starts to be discharged, when the zero-crossing detection signal indicates zero crossing, the second current stops discharging, and when the rectified voltage is greater than the second threshold, the first current continues to be discharged, wherein the first threshold is greater than the second threshold.