Power-down detection circuit and method, ac-dc power supply module

Abstract

The embodiment of the present application relates to the field of power electronics, and discloses a power-down detection circuit and method and an AC-DC power supply module, the power-down detection circuit comprises a first-stage comparison circuit, a second-stage comparison circuit and a controller, the first-stage comparison circuit comprises a rectifier circuit and a first comparator, the rectifier circuit is connected with a live wire and a zero line of alternating current, a non-inverting terminal of the first comparator is connected with an output terminal of the rectifier circuit, an inverting terminal is used for inputting a reference voltage, and an output terminal is used for outputting a square wave signal, the second-stage comparison circuit inputs the square wave signal and converts the square wave signal into a sawtooth wave signal and comprises a second comparator, an inverting terminal of the second comparator is used for inputting the sawtooth wave signal, a non-inverting terminal is used for inputting the reference voltage, and an output terminal is used for outputting a flag signal, and a power-down detection end of the controller is configured to input the flag signal and judge whether the alternating current is powered down according to the flag signal, the embodiment of the present application adopts two-stage comparison circuits to judge whether the alternating current is powered down, the circuit has high reliability, low delay, simple structure and low cost.

Description

TECHNICAL FIELD

[0001] The embodiment of the application relates to the field of power electronics, in particular to a power-off detection circuit and method and an AC-DC power supply module. BACKGROUND

[0002] The AC-DC power supply module is very common in daily applications as a power supply part of a system, however, due to the influence of uncertain factors such as lightning strike and sudden change of power load of a power supply network, the input voltage waveform may appear missing wave, distortion or even power-off. Especially for medical equipment, data processing center and server system, when the input AC power is powered off, the power-off fault needs to be quickly detected, and the running equipment needs to be protected, so as to ensure the normal work of the electronic equipment and reduce the loss of life and property.

[0003] In the implementation process of the embodiment of the application, the inventor finds that the current common several AC power-off detection circuits have various problems as follows: the scheme using the RC filter energy storage circuit usually has long detection time and large delay; the scheme using the optical coupling for isolation sampling is affected by the difference between the on and off threshold voltages of the optical coupling, so that the time accuracy is affected; the scheme directly connected to the AC high-voltage detection is prone to misoperation when the power supply network is not clean; and the scheme using the AC differential input sampling and realizing the power-off detection in the form of software through digital signal processing has high cost. SUMMARY

[0004] The embodiment of the application provides an AC-DC power supply module and a power-off detection circuit and method.

[0005] The embodiment of the application aims to realize the following technical scheme:

[0006] To solve the above technical problems, in a first aspect, the embodiment of the application provides a power-off detection circuit, which comprises a first-stage comparison circuit, a second-stage comparison circuit and a controller, wherein the first-stage comparison circuit at least comprises: a rectifier circuit, an input end of which is connected with a live wire and a neutral wire of AC power, a first comparator, a same-phase end of which is connected with an output end of the rectifier circuit, an opposite-phase end of which is used for inputting a reference voltage, and an output end of which is used for outputting a square wave signal; the second-stage comparison circuit inputs the square wave signal and converts it into a sawtooth wave signal, and the second-stage comparison circuit at least comprises: a second comparator, an opposite-phase end of which is used for inputting the sawtooth wave signal, a same-phase end of which is used for inputting a reference voltage, and an output end of which is used for outputting a flag signal; and the power-off detection end of the controller is configured to input the flag signal and judge whether the AC power is powered off according to the flag signal.

[0007] In some embodiments, the first-stage comparison circuit further comprises a voltage-division filter circuit, an input end of which is connected with a direct-current voltage source, and an output end of which is connected with an inverting end of the first comparator.

[0008] In some embodiments, the voltage-division filter circuit comprises a first resistor, one end of which is connected with the direct-current voltage source, and the other end of which is connected with the inverting end of the first comparator; a second resistor, one end of which is connected with the other end of the first resistor, and the other end of which is grounded; and a first capacitor, one end of which is connected with the other end of the first resistor, and the other end of which is grounded.

[0009] In some embodiments, the rectifier circuit comprises a first diode, an anode of which is connected with a live wire of the alternating current; a second diode, an anode of which is connected with a neutral wire of the alternating current; a third resistor, one end of which is connected with a cathode of the first diode and a cathode of the second diode, and the other end of which is connected with a non-inverting end of the first comparator; and a fourth resistor, one end of which is connected with the other end of the third resistor, and the other end of which is grounded.

[0010] In some embodiments, the first-stage comparison circuit further comprises a protection circuit, one end of which is connected with the non-inverting end of the first comparator, and the other end of which is grounded.

[0011] In some embodiments, the protection circuit comprises a first zener diode, a cathode of which is connected with the non-inverting end of the first comparator, and an anode of which is grounded.

[0012] In some embodiments, the second-stage comparison circuit further comprises an attenuation filter circuit, an input end of which is connected with an output end of the first comparator, and an output end of which is connected with an inverting end of the second comparator.

[0013] In some embodiments, the attenuation filter circuit comprises a fifth resistor, one end of which is connected with the output end of the first comparator; a third diode, an anode of which is connected with the other end of the fifth resistor, and a cathode of which is connected with the inverting end of the second comparator; a second capacitor, one end of which is connected with the cathode of the third diode and the inverting end of the second comparator, and the other end of which is grounded; and an eighth resistor, which is connected in parallel across the second capacitor.

[0014] In some embodiments, the second-stage comparison circuit further comprises a voltage-division feedback circuit, an input end of which is connected with a direct-current voltage source, an output end of which is connected with a non-inverting end of the second comparator, and a feedback end of which is connected with an output end of the second comparator.

[0015] In some embodiments, the voltage dividing feedback circuit comprises: a sixth resistor, one end of which is connected to the DC voltage source and the other end of which is connected to the non-inverting terminal of the second comparator; a seventh resistor, one end of which is connected to the other end of the sixth resistor and the other end of which is grounded; and a fourth diode, the cathode of which is connected to the non-inverting terminal of the second comparator and the anode of which is connected to the output terminal of the second comparator.

[0016] In some embodiments, the second-stage comparison circuit further comprises: a voltage dividing and attenuating circuit, the input terminal of which is connected to the output terminal of the second comparator, and the output terminal of which is connected to the power-down detection terminal of the controller and used for modulating the output of the flag signal.

[0017] In some embodiments, the voltage dividing and attenuating circuit comprises: a ninth resistor, one end of which is connected to the output terminal of the second comparator and the other end of which is connected to the feedback terminal of the voltage dividing feedback circuit; a fifth diode, the anode of which is connected to the other end of the ninth resistor and the cathode of which is connected to the power-down detection terminal of the controller; a tenth resistor, one end of which is connected to the cathode of the fifth diode and the other end of which is grounded; and a third capacitor, which is connected in parallel across the tenth resistor.

[0018] To solve the above technical problems, in a second aspect, an embodiment of the present application provides a power-down detection method applied to the power-down detection circuit of the first aspect, and the method comprises: filtering, by the first-stage comparison circuit, the phase angle near the zero-crossing of the alternating current to modulate a square wave signal; modulating, by the second-stage comparison circuit, the square wave signal into a flag signal meeting the time accuracy requirement; and determining, according to the flag signal, whether the alternating current is powered down.

[0019] To solve the above technical problems, in a third aspect, an embodiment of the present application provides an AC-DC power supply module comprising the power-down detection circuit of the first aspect.

[0020] Compared with the prior art, the application has the beneficial effects that: different from the prior art, the embodiment of the application provides a power-off detection circuit and method and an AC-DC power supply module, the power-off detection circuit comprises a first-stage comparison circuit, a second-stage comparison circuit and a controller, wherein the first-stage comparison circuit at least comprises a connected rectifier circuit and a first comparator, the rectifier circuit is connected with a live wire and a zero wire of alternating current, a same-phase end of the first comparator is connected with an output end of the rectifier circuit, an opposite-phase end is used for inputting a reference voltage, and an output end is used for outputting a square wave signal, the second-stage comparison circuit inputs the square wave signal and converts the square wave signal into a sawtooth wave signal, and the second-stage comparison circuit at least comprises a second comparator, an opposite-phase end of the second comparator is used for inputting the sawtooth wave signal, a same-phase end is used for inputting the reference voltage, and an output end is used for outputting a flag signal, and a power-off detection end of the controller is configured to input the flag signal and judge whether the alternating current is powered off according to the flag signal, the embodiment of the application adopts two-stage comparison circuits to judge whether the alternating current is powered off, and the circuit has high reliability, low delay, simple structure and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0021] One or more embodiments are illustrated by way of example in the drawings in which like reference numerals refer to like elements / modules and steps throughout, and wherein: the drawings are not necessarily to scale, except as otherwise noted.

[0022] Figure 1 is a structural block diagram of a power-off detection circuit provided by the embodiment one of the application;

[0023] Figure 2 is a structural block diagram of another power-off detection circuit provided by the embodiment one of the application;

[0024] Figure 3 is a circuit structure schematic diagram of a power-off detection circuit provided by the embodiment one of the application;

[0025] Figure 4 is a level change waveform diagram of the power-off detection circuit provided by the embodiment one of the application in the case of a short-wave loss distortion of input alternating current;

[0026] Figure 5 is a flowchart of a power-off detection method provided by the embodiment two of the application;

[0027] Figure 6 is a structural schematic diagram of an AC-DC power supply module provided by the embodiment three of the application. DETAILED DESCRIPTION

[0028] The application will be described in further detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the application, but are not intended to limit the application in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the application. These are all within the scope of protection of the application.

[0029] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0030] It should be noted that the various features in the embodiments of the present application can be combined with each other without conflict, and are all within the scope of protection of the present application. In addition, although the functional modules are divided in the device schematic diagram, and the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order from the module division in the device or the order in the flowchart. In addition, the "first", "second", "third" and the like used herein do not limit the data and execution order, but only distinguish the same items or similar items with basically the same function and effect. It should be noted that when an element is described as "connected" to another element, it can be directly connected to the other element or one or more intermediate elements can be present therebetween.

[0031] Unless otherwise defined, all technical and scientific terms used in the specification are the same as those commonly understood by those skilled in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not intended to limit the present application. The term "and / or" used in the specification includes any and all combinations of one or more related listed items.

[0032] In addition, the technical features involved in each embodiment of the application described below can be combined with each other as long as there is no conflict.

[0033] Specifically, the embodiments of the present application will be further described below in combination with the drawings.

[0034] Example 1

[0035] The embodiment of the present application provides a power failure detection circuit, please refer to Figure 1Fig. 1 shows a structural block diagram of a power-off detection circuit according to an embodiment of the present application, which comprises a first-stage comparison circuit 100, a second-stage comparison circuit 200 and a controller 300, wherein the first-stage comparison circuit 100 at least comprises: a rectifier circuit 110, an input end of which is connected with a live wire and a zero wire of an alternating current AC, a first comparator U1A, a same-phase end of which is connected with an output end of the rectifier circuit 110, an opposite-phase end of which is used for inputting a reference voltage, and an output end of which is used for outputting a square wave signal; the second-stage comparison circuit 200 inputs the square wave signal and converts it into a sawtooth wave signal, and the second-stage comparison circuit 200 at least comprises: a second comparator U1B, an opposite-phase end of which is used for inputting the sawtooth wave signal, a same-phase end of which is used for inputting a reference voltage, and an output end of which is used for outputting a flag signal; a power-off detection end of the controller 300 is configured to input the flag signal and judge whether the alternating current is powered off according to the flag signal. The sawtooth wave signal is a sawtooth wave signal with fast charging and slow discharging.

[0036] The embodiment of the present application adopts two-stage comparison circuits to judge whether the alternating current is powered off, and has high circuit reliability, strong anti-interference, low delay, simple structure, low cost, and can adjust the power-off holding time according to requirements, and outputs the phase angle after shielding part of the phase angle near the zero-crossing of the alternating current to the controller for power-off judgment, thereby avoiding the problem that the alternating voltage is easily misjudged under the condition of noise interference due to small amplitude near the zero-crossing.

[0037] In some embodiments, please refer to Figure 2 Fig. 2 shows a structural block diagram of another power-off detection circuit according to an embodiment of the present application, which is similar to Fig. 1, and the difference is that the first-stage comparison circuit 100 further comprises: a voltage division filter circuit 120, an input end of which is connected with a direct current voltage source VREF, and an output end of which is connected with an opposite-phase end of the first comparator U1A. After the alternating voltage is converted into a same-phase and low-amplitude steamed-bun wave voltage through the rectifier circuit 110 and the voltage division filter circuit 120, the alternating voltage is inputted as the input of the first comparator U1A.

[0038] Specifically, please refer to Figure 3This illustration shows the circuit structure of a power-down detection circuit provided in an embodiment of the present invention. The voltage divider and filter circuit 120 includes: a first resistor R1, one end of which is connected to the DC voltage source VREF, and the other end of which is connected to the inverting input of the first comparator U1A; a second resistor R2, one end of which is connected to the other end of the first resistor R1, and the other end of which is grounded; and a first capacitor C1, one end of which is connected to the other end of the first resistor R1, and the other end of which is grounded. The first resistor R1 and the second resistor R2 are voltage-dividing attenuation resistors. The voltage output from the DC voltage source VREF is filtered by the first capacitor C1, the first resistor R1, and the second resistor R2 to obtain a constant reference voltage, which is then input to the inverting input of the first comparator U1A.

[0039] For details, please continue to see Figure 3 The rectifier circuit 110 includes: a first diode D1, whose anode is connected to the live wire of the AC power supply; a second diode D2, whose anode is connected to the neutral wire of the AC power supply; a third resistor R3, one end of which is connected to the cathodes of the first diode D1 and the second diode D2, and the other end of which is connected to the non-inverting input of the first comparator U1A; and a fourth resistor R4, one end of which is connected to the other end of the third resistor R3, and the other end of which is grounded. Wherein, the first diode D1 and the second diode D2 are rectifier diodes, and the third resistor R3 and the fourth resistor R4 are two voltage divider resistors for input sampling.

[0040] In some embodiments, please continue to see Figure 2 The first-stage comparator circuit 100 further includes a protection circuit 130, one end of which is connected to the non-inverting input of the first comparator U1A, and the other end of which is grounded. The protection circuit 130 is used to protect the first comparator U1A from damage in the event of an abnormal AC power supply.

[0041] For details, please continue to see Figure 3 The protection circuit 130 includes a first Zener diode Z1, whose cathode is connected to the non-inverting input of the first comparator U1A, and whose anode is grounded; that is, the first Zener diode Z1 is connected in parallel across the fourth resistor R4. The first Zener diode Z1 is used to ensure that the input pin of the first comparator U1A is not damaged by excessive voltage in the event of lightning strikes or surge voltage spikes.

[0042] The first-stage comparison circuit 100 provided by the embodiment of the present application works in the following manner: the high-level voltage input to the first comparator U1A after attenuation filtering is the supply voltage, and the low-level voltage is close to zero voltage. After comparison between the first comparator U1A and the reference voltage, a high-level square wave and / or a low-level signal are output. Specifically, when the voltage value input to the same-phase end of the first comparator U1A is less than the reference voltage of the opposite-phase end, the first comparator U1A outputs a low level. At this time, the voltage input to the same-phase end of the first comparator U1A is the phase angle near the zero-crossing point of the alternating current, and other voltages with phase angles other than the zero-crossing point are rectified by the rectifier circuit 110 and then compared with the reference voltage by the first comparator U1A, and a high level is output. The reference voltage can be adjusted by reasonably setting the resistance value ratio of the first resistor R1 and the second resistor R2 in the voltage division and filtering circuit 120, so that the first comparator U1A can determine the low voltage of the sine wave near the zero-crossing point, thereby preventing the false judgment caused by interference and unstable sampling.

[0043] In some embodiments, please continue to refer to Figure 2 , the second-stage comparison circuit 200 further comprises: an attenuation filtering circuit 210, an input end of which is connected with an output end of the first comparator U1A, and an output end of which is connected with an opposite-phase end of the second comparator U1B. The attenuation filtering circuit 210 is used to attenuate and filter the square wave signal output by the first comparator U1A into a sawtooth wave signal with fast charging and slow discharging, and then input the sawtooth wave signal to the opposite-phase end of the second comparator U1B.

[0044] Specifically, please continue to refer to Figure 3 , the attenuation filtering circuit 210 comprises: a fifth resistor R5, one end of which is connected with the output end of the first comparator U1A; a third diode D3, an anode of which is connected with the other end of the fifth resistor R5, and a cathode of which is connected with the opposite-phase end of the second comparator U1B; a second capacitor C2, one end of which is connected with the cathode of the third diode D3 and the opposite-phase end of the second comparator U1B, and the other end of which is grounded; and an eighth resistor R8, which is connected in parallel across the second capacitor C2. The square wave signal can be adjusted into a sawtooth wave signal with fast charging and slow discharging by the second capacitor C2. The discharge time constant of the second capacitor C2 after the alternating current is powered off can be adjusted by adjusting the capacitance value of the second capacitor C2 and the resistance value of the eighth resistor R8, so as to adjust the detection accuracy of the alternating current power-off. The third diode D3 is used to prevent the second capacitor C2 from discharging through the fifth resistor R5 when the first comparator U1A outputs a low level due to the zero-crossing point of the alternating current or the alternating current power-off.

[0045] In some embodiments, please continue to refer toFigure 2 The second-stage comparison circuit 200 further comprises a voltage division feedback circuit 220, an input end of which is connected with the DC voltage source, an output end of which is connected with the non-inverting terminal of the second comparator U1B, and a feedback end of which is connected with the output end of the second comparator U1B. The DC voltage source can input a stable reference voltage to the non-inverting terminal of the second comparator U1B through the voltage division feedback circuit 220, and can prevent the second comparator U1B from outputting high-low jitter.

[0046] Specifically, please continue to refer to Figure 3 The voltage division feedback circuit 220 comprises a sixth resistor R6, one end of which is connected with the DC voltage source VREF, and the other end of which is connected with the non-inverting terminal of the second comparator U1B; a seventh resistor R7, one end of which is connected with the other end of the sixth resistor R6, and the other end of which is grounded; and a fourth diode D4, a cathode of which is connected with the non-inverting terminal of the second comparator U1B, and an anode of which is connected with the output end of the second comparator U1B. The DC voltage source VREF can obtain a stable reference voltage as the input reference given to the non-inverting terminal of the second comparator U1B by voltage division through the sixth resistor R6 and the seventh resistor R7, and compare the voltage with the sawtooth wave voltage input to the inverting terminal of the second comparator U1B. By adjusting the voltage values of the sixth resistor R6 and the seventh resistor R7, the voltage minimum value of the sawtooth wave output by the second capacitor C2 is kept greater than the reference voltage, so that the output end of the second comparator U1B can keep outputting a low-level signal when the AC power is normal. In addition, the fourth diode D4 is a hysteresis diode, so that the second comparator U1B can realize a self-locking high-level signal function, thereby preventing the output of the second comparator U1B from repeatedly jittering when the AC power is powered off.

[0047] It should be noted that the DC voltage source VREF connected with the sixth resistor R6 and the DC voltage source VREF connected with the first resistor R1 can be the same DC voltage source, or two independent DC voltage sources. Preferably, when the power-off detection circuit 10 is in the same power module, a DC voltage source is shared, and the specific setting can be made according to actual needs.

[0048] In some embodiments, please continue to refer to Figure 2 The second-stage comparison circuit 200 further comprises a voltage division feedback circuit 220, an input end of which is connected with the DC voltage source, an output end of which is connected with the non-inverting terminal of the second comparator U1B, and a feedback end of which is connected with the output end of the second comparator U1B. The DC voltage source can input a stable reference voltage to the non-inverting terminal of the second comparator U1B through the voltage division feedback circuit 220, and can prevent the second comparator U1B from outputting high-low jitter.

[0049] Specifically, please continue to see Figure 3 , the voltage dividing attenuation circuit 230 comprises: a ninth resistor R9, one end of which is connected with the output end of the second comparator U1B, and the other end of which is connected with the feedback end of the voltage dividing feedback circuit 220, that is, the other end of which is connected with the anode of the fourth diode D4; a fifth diode D5, the anode of which is connected with the other end of the ninth resistor R9, and the cathode of which is connected with the power failure detection end of the controller 300; a tenth resistor R10, one end of which is connected with the cathode of the fifth diode D5, and the other end of which is grounded; and a third capacitor C3, which is connected in parallel across the tenth resistor R10. The high-level signal output by the second comparator U1B is divided and attenuated by the ninth resistor R9 and the tenth resistor R10, and after being shallowly filtered by the third capacitor C3, it is used as a flag signal for judging the power failure of the alternating current.

[0050] When the second-stage comparison circuit 200 provided by the embodiment of the present application is working, the square wave signal output by the first comparator U1A is input to the inverting end of the second comparator U1B after being output as a sawtooth wave by the attenuation filter circuit 210, and the voltage value of the sawtooth wave is compared with the reference voltage input to the non-inverting end of the second comparator U1B, so that a low level is output in the case of normal alternating current, and a high level is output in the case of power failure of the alternating current. Specifically, when the alternating current is powered off, the voltage of the sawtooth wave will continuously decrease, and when the voltage value of the sawtooth wave is less than the reference voltage input to the non-inverting end of the second comparator U1B, the second comparator U1B outputs a high level. The time from the peak of the last sawtooth wave to the change of the output of the second comparator U1B from low to high is the detection time of the power failure detection circuit.

[0051] Compared with the prior art, please see Figure 4 , which shows the level change waveform diagram of the power failure detection circuit provided by the embodiment of the present application in the case of short-wave-loss distortion of the input alternating current, as shown in Figure 4 , after setting the scene of short-wave-loss distortion and detecting the voltage detection points of the power failure detection circuit provided by the embodiment of the present application, it can be found that the power failure detection circuit provided by the embodiment of the present application will not malfunction in the case of short-wave-loss distortion of the input alternating current, and the circuit reliability is strong. Specifically, by detecting the voltage Va of the non-inverting end of the first comparator U1A, the voltage Vb (square wave) of the output end of the first comparator U1A, the voltage Vc (sawtooth wave) of the inverting end of the second comparator U1B, and the voltage Vd (that is, the power failure detection end Vin_drop of the controller 300) of the cathode end of the fifth diode D5, it is not difficult to see that the power failure detection circuit provided by the embodiment of the present application can quickly return to the normal state for power failure detection after short-wave-loss distortion such as surge, lightning strike, and jitter, and the circuit reliability is strong.

[0052] Embodiment two

[0053] The embodiment of the present application provides a power-off detection method, please refer to Figure 5 which shows the flow of a power-off detection method provided by the embodiment of the present application, the power-off detection method can be applied to the power-off detection circuit described in embodiment one, and the method comprises the following steps but is not limited to the following steps:

[0054] Step S10: filtering the phase angle near the zero-crossing of alternating current by the first-stage comparison circuit to obtain a square wave signal;

[0055] Specifically, please refer to the above embodiment one, after comparison by the first-stage comparison circuit, the phase angle near the zero-crossing of alternating current is filtered out, thereby obtaining a square wave signal with high and low levels. Whether it belongs to the judgment range of the phase angle near the zero-crossing of alternating current can be adjusted and set by setting the resistance value and the proportion of the resistance value of the resistance in the voltage division filter circuit in the above embodiment one.

[0056] Further, in addition to detecting the sinusoidal wave signal as described in embodiment one, the first-stage comparison circuit can also detect the power-off condition of alternating current with other waveforms such as triangular wave and square wave by configuring the parameters of each electronic component in the first-stage comparison circuit.

[0057] Step S20: modulating the square wave signal into a flag signal meeting the time accuracy requirement by the second-stage comparison circuit;

[0058] Specifically, please continue to refer to the above embodiment one, the square wave signal output by the first-stage comparison circuit enters the second-stage comparison circuit and is compared with a reference voltage, thereby outputting two cases of whether the alternating current has power-off. The RC time constant of the resistance and the capacitance in the attenuation filter circuit of the second-stage comparison circuit can be adjusted to meet the time accuracy requirement of the system for power-off fault detection.

[0059] Step S30: judging whether the alternating current has power-off according to the flag signal.

[0060] Specifically, after obtaining the flag signal output by the second-stage comparison circuit, whether the alternating current has power-off can be determined according to the level of the flag signal. Further, the time of power-off detection can also be determined by detecting the time when the peak of the last sawtooth wave input into the second-stage comparison circuit changes from low to high.

[0061] Embodiment three

[0062] The embodiment of the present application provides an AC-DC power supply module, please refer toFigure 6 It shows the structure of an AC-DC power module provided by the embodiment of the application, and the AC-DC power module 1 comprises the power-off detection circuit 10 as described in the first embodiment.

[0063] The AC-DC power module 1 is a device, a device, a module, a unit capable of converting alternating current into direct current, and the power-off detection circuit 10 is arranged in the AC-DC power module 1, so that the power-off detection of the input alternating current can be realized.

[0064] The specific structure, connection relationship, working principle and the like of the power-off detection circuit 10 are described in the above first embodiment and the accompanying drawings. Figure 1 , the accompanying Figure 2 and the accompanying Figure 3 , which will not be described here in detail.

[0065] It should be noted that the controller 300 in the power-off detection circuit 10 can be a controller / control chip / control unit shared with other functions in the AC-DC power module 1, or can be a controller / control chip / control unit independently arranged in the module / circuit board of the power-off detection circuit 10, and the specific arrangement can be made according to actual needs. Moreover, the controller 300 at least includes a processor and a memory connected in communication, the memory stores instructions executable by the processor, so that the processor can execute the power-off detection method described in the above second embodiment; the memory as a non-volatile computer readable storage medium can be used to store non-volatile software programs, non-volatile computer executable programs and modules.

[0066] The embodiment of the application provides a power-off detection circuit and method and an AC-DC power module, the power-off detection circuit comprises a first-stage comparison circuit, a second-stage comparison circuit and a controller, wherein the first-stage comparison circuit at least comprises a rectifier circuit and a first comparator connected, the rectifier circuit is connected with a live wire and a zero line of alternating current, a same-phase end of the first comparator is connected with an output end of the rectifier circuit, an opposite-phase end is used for inputting a reference voltage, and an output end is used for outputting a square wave signal, the second-stage comparison circuit at least comprises a second comparator, an opposite-phase end of the second comparator is used for inputting a fast-charging slow-discharging sawtooth wave signal, a same-phase end is used for inputting a reference voltage, and an output end is used for outputting a flag signal, and a power-off detection end of the controller is configured to input the flag signal and judge whether the alternating current is powered off according to the flag signal, the embodiment of the application adopts two-stage comparison circuits to judge whether the alternating current is powered off, the circuit has high reliability, low delay, simple structure and low cost.

[0067] It should be noted that the above-described apparatus embodiments are merely illustrative, and the units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e., can be located in one place, or can be distributed on multiple network units. Part or all of the modules can be selected according to actual needs to achieve the purpose of the embodiment.

[0068] Through the above description of the embodiments, those skilled in the art can clearly understand that the embodiments can be implemented by means of software plus a general hardware platform, and of course, can also be implemented by hardware. Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by a computer program instructing related hardware, and the program can be stored in a computer readable storage medium. When the program is executed, it can include the processes of the above-mentioned embodiment methods. The storage medium can be a magnetic disc, an optical disc, a read-only memory (ROM) or a random access memory (RAM), etc.

[0069] Finally, it should be noted that: the above examples are used to illustrate the technical solutions of the present application, and are not limited thereto; under the idea of the present application, the technical features of the above examples or different examples can also be combined, the steps can be implemented in any order, and there are many other changes of the different aspects of the present application as described above. In order to be brief, they are not provided in detail; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A power-down detection circuit, characterized by, The first-stage comparison circuit, the second-stage comparison circuit and the controller are included, wherein The first-stage comparison circuit at least includes The rectifier circuit has an input end connected with a live wire and a zero wire of an alternating current, The first comparator has a non-inverting input end connected with an output end of the rectifier circuit, an inverting input end for inputting a reference voltage, and an output end for outputting a square wave signal; The second-stage comparison circuit inputs the square wave signal and converts it into a sawtooth wave signal, and the second-stage comparison circuit at least includes a second comparator having an inverting input end for inputting the sawtooth wave signal, a non-inverting input end for inputting a reference voltage, and an output end for outputting a flag signal; The attenuation filter circuit has an input end connected with an output end of the first comparator and an output end connected with the inverting input end of the second comparator, and is configured to attenuate and filter the square wave signal output by the first comparator into a sawtooth wave signal with fast charging and slow discharging and input the sawtooth wave signal into the inverting input end of the second comparator; The attenuation filter circuit includes a fifth resistor, a third diode, a second capacitor and an eighth resistor, one end of the fifth resistor is connected with the output end of the first comparator; The anode of the third diode is connected with the other end of the fifth resistor, and the cathode of the third diode is connected with the inverting input end of the second comparator; One end of the second capacitor is connected with the cathode of the third diode and the inverting input end of the second comparator, and the other end of the second capacitor is grounded; The eighth resistor is connected in parallel across the second capacitor; The power-off detection end of the controller is configured to input the flag signal and determine whether the alternating current is powered off according to the flag signal.

2. The power-down detection circuit of claim 1, wherein, The first-stage comparison circuit further includes The voltage dividing filter circuit has an input end connected with a direct current voltage source and an output end connected with the inverting input end of the first comparator.

3. The power down detection circuit of claim 2, wherein, The voltage dividing filter circuit includes The first resistor has one end connected with the direct current voltage source and the other end connected with the inverting input end of the first comparator; The second resistor has one end connected with the other end of the first resistor and the other end grounded; The first capacitor has one end connected with the other end of the first resistor and the other end grounded.

4. The power-down detection circuit of claim 1, wherein, The rectifier circuit includes The first diode has an anode connected with the live wire of the alternating current; The second diode has an anode connected with the zero wire of the alternating current; The third resistor has one end connected with the cathodes of the first diode and the second diode and the other end connected with the non-inverting input end of the first comparator; The fourth resistor has one end connected with the other end of the third resistor and the other end grounded.

5. The power down detection circuit of claim 2, wherein, The first-stage comparison circuit further includes The protection circuit has one end connected with the non-inverting input end of the first comparator and the other end grounded.

6. The power-down detection circuit of claim 5, wherein, The protection circuit includes The first voltage stabilizing tube has a cathode connected with the non-inverting input end of the first comparator and an anode grounded.

7. The power-down detection circuit of claim 1, wherein, The second-stage comparison circuit further includes The voltage dividing feedback circuit has an input end connected with a direct current voltage source, an output end connected with the non-inverting input end of the second comparator, and a feedback end connected with the output end of the second comparator.

8. The power-down detection circuit of claim 7, wherein, The voltage dividing feedback circuit includes a sixth resistor, one end of which is connected to the direct current voltage source, and the other end of which is connected to the non-inverting terminal of the second comparator; a seventh resistor, one end of which is connected to the other end of the sixth resistor, and the other end of which is grounded; a fourth diode, the cathode of which is connected to the non-inverting terminal of the second comparator, and the anode of which is connected to the output terminal of the second comparator.

9. The power down detection circuit of claim 7, wherein, The second-stage comparison circuit further comprises: a voltage division and attenuation circuit, the input terminal of which is connected to the output terminal of the second comparator, and the output terminal of which is connected to the power failure detection terminal of the controller and used for modulating the output of the flag signal.

10. The power-down detection circuit of claim 9, wherein, The voltage division and attenuation circuit comprises: a ninth resistor, one end of which is connected to the output terminal of the second comparator, and the other end of which is connected to the feedback terminal of the voltage division and feedback circuit; a fifth diode, the anode of which is connected to the other end of the ninth resistor, and the cathode of which is connected to the power failure detection terminal of the controller; a tenth resistor, one end of which is connected to the cathode of the fifth diode, and the other end of which is grounded; a third capacitor, which is connected in parallel to the tenth resistor.

11. A power down detection method, comprising: The method is applied to the power failure detection circuit according to any one of claims 1-10, and the method comprises: filtering the phase angle near the zero-crossing of the alternating current by the first-stage comparison circuit to modulate a square wave signal; modulating the square wave signal into a flag signal meeting the time accuracy requirement by the second-stage comparison circuit; judging whether the alternating current is powered off according to the flag signal.

12. An AC-DC power supply module, characterized by, The power failure detection circuit according to any one of claims 1-10.

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