Undervoltage detection circuit and electronic equipment

Abstract

An undervoltage detection circuit and electronic device provided by an embodiment of the present application include a voltage divider circuit and a comparison circuit; the comparison circuit includes a first input terminal and a second input terminal; the first input terminal is connected to the output terminal of the voltage divider circuit, and the second input terminal is connected to the reference voltage output terminal, and the voltage divider circuit is used to divide the power supply voltage into 1 / N power supply voltage, wherein N is a natural number greater than or equal to 2, and the comparison circuit is used to compare the reference voltage with the voltage output of the voltage divider circuit input at the first input terminal to determine whether the power supply is in an undervoltage state. After the power supply voltage is divided by a voltage divider circuit composed of a capacitor and a switch, the application performs undervoltage detection in the input comparison circuit to determine whether the power supply voltage is in an undervoltage state, which can reduce the power consumption of the power supply and increase the service life of the power supply.

Description

Technical Field

[0001] The embodiments of the present application belong to the field of voltage detection technology, and in particular, relate to undervoltage detection circuits and electronic devices. Background Art

[0002] Low voltage detection is an important functional module in integrated circuits. When the power supply voltage is lower than a certain threshold during power-off, other internal circuit modules need to be shut down. When the power supply voltage rises above a certain threshold during power-on, other internal modules start working. The power consumption of undervoltage detection circuits in the prior art is relatively large, resulting in a shortened power supply time for the chip to be powered.

[0003] In order to solve the technical problems in the prior art, it is necessary to study a new undervoltage detection circuit. Summary of the invention

[0004] In order to solve or alleviate the problems in the prior art, in a first aspect, an embodiment of the present application provides an undervoltage detection circuit, including a voltage divider circuit and a comparison circuit;

[0005] The comparison circuit comprises a first input terminal and a second input terminal;

[0006] The first input terminal is connected to the output terminal of the voltage divider circuit, and the second input terminal is connected to the reference voltage output terminal. The voltage divider circuit is used to divide the power supply voltage into 1 / N power supply voltage, wherein N is a natural number greater than or equal to 2, and the comparison circuit is used to compare the reference voltage with the voltage output by the voltage divider circuit input at the first input terminal to determine whether the power supply is in an undervoltage state.

[0007] Compared with the prior art, the embodiment of the present application provides an undervoltage detection circuit. After the power supply voltage is divided by a voltage divider circuit composed of a capacitor and a switch, an undervoltage detection is performed in an input comparison circuit to determine whether the power supply voltage is in an undervoltage state. Since the undervoltage detection circuit consumes less power, the power consumption of the power supply can be reduced, thereby increasing the service life of the power supply.

[0008] In a second aspect, an embodiment of the present application provides an electronic device, comprising the undervoltage detection circuit described in the first aspect.

[0009] Compared with the prior art, the beneficial effects of the electronic device provided by the second aspect are the same as the beneficial effects of the undervoltage detection circuit provided by the first aspect, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. Some specific embodiments of the present application will be described in detail in an illustrative and non-restrictive manner with reference to the drawings. The same reference numerals in the drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the drawings:

[0011] Figure 1 is a structural schematic diagram of an undervoltage detection circuit provided in an embodiment of the present application;

[0012] Figure 2 is a schematic diagram of the structure of a voltage divider circuit provided in an embodiment of the present application;

[0013] Figure 3 is a schematic diagram of the structure of a voltage divider circuit provided in an embodiment of the present application;

[0014] Figure 4-9 is a schematic diagram of the structure of the voltage divider circuit provided in different embodiments of the present application;

[0015] Fig.10 is a schematic diagram of the structure of a comparison circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0016] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only embodiments of a part of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0017] The present application is applicable to undervoltage detection circuits of various chips, and a voltage divider circuit composed of switched capacitors is used to replace the resistor voltage divider circuit in the prior art to realize the step-down conversion of the power supply voltage. The voltage divider circuit composed of switched capacitors realizes the integral multiple voltage division of the power supply voltage with an extremely small current. In addition, the comparison circuit used in the present application consumes only a small part of the total current before the undervoltage occurs, which greatly reduces the power consumption.

[0018] like Figure 1 As shown, an embodiment of the present application provides an undervoltage detection circuit, including a voltage divider circuit 01 and a comparison circuit 02;

[0019] The comparison circuit 02 includes a first input terminal and a second input terminal;

[0020] The first input terminal is connected to the output terminal of the voltage divider circuit 01, and the second input terminal is connected to the reference voltage output terminal. The voltage divider circuit 01 is used to divide the power supply voltage into 1 / N power supply voltage, where N is a natural number greater than or equal to 2. The comparison circuit 02 is used to compare the reference voltage with the voltage output by the voltage divider circuit input at the first input terminal to determine whether the power supply is in an undervoltage state.

[0021] In the embodiment of the present application, the first input terminal of the comparison circuit 02 is a positive electrode, and the second input terminal of the comparison circuit 02 is a negative electrode.

[0022] like Figure 2 As shown, as a preferred embodiment of the present application, the voltage divider circuit 01 includes a first voltage divider sub-circuit 04-1 and a first capacitor 03 connected to each other, and the circuit composed of the first voltage divider sub-circuit 04-1 and the first capacitor 03 is used to output a 1 / N power supply voltage.

[0023] like Figure 3 As shown, preferably, on the basis of the above embodiment, the voltage divider circuit also includes a second voltage divider sub-circuit 04-2 and a first capacitor 03, and the circuit composed of the second voltage divider sub-circuit 04-2 and the first capacitor 03 is used to output a voltage of 1 / N power supply voltage; the first voltage divider sub-circuit 04-1 and the second voltage divider sub-circuit 04-2 are alternately connected to the power supply to realize uninterrupted monitoring of the voltage change of the power supply.

[0024] The specific structure of the voltage divider circuit of the present application is described in detail below with specific embodiments:

[0025] The following mainly introduces the voltage divider circuit of the present application in detail by taking the voltage divider circuit that divides the power supply voltage into 1 / 2, 1 / 4, and 1 / 5 as an example. It should be noted that any circuit structure can realize the voltage division of the power supply voltage into 1 / N of the power supply voltage, and the present application does not impose any restrictions on this.

[0026] Embodiment 1

[0027] like Figure 4 As shown, this embodiment mainly describes the specific circuit structure of the voltage divider circuit dividing the power supply voltage into 1 / 2.

[0028] The first voltage dividing sub-circuit 04 - 1 includes a second capacitor 011 , a first switch 012 , a second switch 013 , a third switch 014 and a fourth switch 015 ;

[0029] One end of the first switch 012 is connected to the power supply, and the other end of the first switch 012 is connected to one end of the second switch 013, the third switch 014 and the fourth switch 015 in sequence;

[0030] One end of the second capacitor 011 is connected to the common end between the first switch 012 and the second switch 013, and the other end of the second capacitor 011 is connected to the common end between the third switch 014 and the fourth switch 015;

[0031] One end of the first capacitor 03 is connected to the common end between the second switch 013 and the third switch 014, and the other end of the first capacitor 03 and the other end of the fourth switch 015 are both connected to the equipotential node;

[0032] The first switch 012 and the third switch 014 form a first switch combination, the second switch 013 and the fourth switch 015 form a first switch combination, by controlling the first switch combination to be turned off and the second switch combination to be turned on, the first capacitor 03 and the second capacitor 011 are connected in parallel, and the first voltage divider circuit outputs a voltage of 1 / 2 of the power supply voltage through the first capacitor 03; or,

[0033] By controlling the first switch combination to be turned on and the second switch combination to be turned off; or, the output voltage of the first voltage divider sub-circuit 04 - 1 through the first capacitor 03 is 1 / 2 of the power supply voltage.

[0034] It should be noted that this embodiment mainly forms a first voltage divider sub-circuit 04 - 1 through a capacitor switch combination. The first voltage divider sub-circuit 04 - 1 can divide the power supply voltage into 1 / 2 and then input it into the comparison circuit 02 through the first input terminal of the comparison circuit 02 .

[0035] exist Figure 4 In the circuit structure shown, the first voltage-dividing subcircuit 04-1 is composed of four switches and two capacitors, and the four switches are controlled by a non-overlapping dual-phase clock. In the first phase stage, the first capacitor 03 is connected in series with the second capacitor 011. In the second phase stage, the first capacitor 03 is connected in parallel with the second capacitor 011. When the first capacitor 03 is connected in series with the second capacitor 011, the first capacitor 03 will be charged, and the voltage of the first capacitor 03 after charging is equal to the power supply voltage minus the voltage of the second capacitor 011. When the first capacitor 03 is connected in parallel with the second capacitor 011, the charge on the first capacitor 03 is moved to the second capacitor 011, so that the power supply voltage is divided into 1 / 2 of the power supply voltage by the first voltage-dividing subcircuit 04-1.

[0036] Embodiment 2

[0037] like Figure 5 As shown, in Figure 4 On the basis of the circuit shown in the figure, a second voltage dividing sub-circuit 04-2 is added, and the second voltage dividing sub-circuit 04-2 includes a third capacitor 020, a fifth switch 016, a sixth switch 017, a seventh switch 018 and an eighth switch 019;

[0038] One end of the fifth switch 016 is connected to the power supply, and the other end of the fifth switch 016 is connected to one end of the sixth switch 017, the seventh switch 018 and the eighth switch 019 in sequence;

[0039] One end of the third capacitor 020 is connected to the common end between the fifth switch 016 and the sixth switch 017, and the other end of the third capacitor 020 is connected to the common end between the seventh switch 018 and the eighth switch;

[0040] One end of the first capacitor 03 is connected to the common end between the sixth switch 017 and the seventh switch 018, and the other end of the first capacitor 03, the other end of the fourth switch 015 and the other end of the eighth switch 019 are all connected to the equipotential node;

[0041] When the fifth switch 016 and the seventh switch 018 are turned off, and the sixth switch 017 and the eighth switch are turned on, the first capacitor 03 and the third capacitor 020 are connected in parallel, and the second voltage divider circuit 04-2 outputs a voltage of 1 / 2 of the power supply voltage through the first capacitor 03; or,

[0042] When the fifth switch 016 and the seventh switch 018 are turned on and the sixth switch 017 and the eighth switch are turned off, the first capacitor 03 and the third capacitor 020 are connected in series, and the second voltage divider sub-circuit 04 - 2 outputs a voltage of 1 / 2 of the power supply voltage through the first capacitor 03 .

[0043] The fifth switch 016 and the seventh switch 018 form a third switch combination, and the sixth switch 017 and the eighth switch 019 form a fourth switch combination. By controlling the third switch combination to be turned off and the fourth switch combination to be turned on, the first capacitor 03 and the second capacitor 011 are connected in parallel, and the output voltage of the second voltage divider sub-circuit 04-2 through the first capacitor 03 is 1 / 2 of the power supply voltage; or, by controlling the third switch combination to be turned on and the fourth switch combination to be turned off, the first capacitor 03 and the third capacitor 020 are connected in series; the output voltage of the second voltage divider sub-circuit 04-2 through the first capacitor 03 is 1 / 2 of the power supply voltage;

[0044] By controlling the first switch combination and the fourth switch combination to be turned on, and by controlling the second switch combination and the third switch combination to be turned off; or, by controlling the first switch combination and the fourth switch combination to be turned off, and by controlling the second switch combination and the third switch combination to be turned on, the first voltage divider sub-circuit 04-1 and the second voltage divider sub-circuit 04-2 can uninterruptedly monitor the voltage changes of the power supply.

[0045] exist Figure 4As shown, in the first embodiment, in the second phase stage, since the first switch combination is in the off state, the voltage change information cannot be directly transmitted to the output end. This problem can be solved by the second embodiment, such as when the first switch combination in the first voltage-dividing subcircuit 04-1 of one phase is turned off, the third switch combination in the second voltage-dividing subcircuit 04-2 of another phase is turned on; or, when the first switch combination in the first voltage-dividing subcircuit 04-1 of one phase is turned on, the third switch combination in the second voltage-dividing subcircuit 04-2 of another phase is turned off. If the voltage of the power supply changes, the voltage change will be continuously transmitted to the output end through the first capacitor 03, which improves the response speed. That is to say, in the second embodiment, the voltage change of the power supply can be continuously monitored.

[0046] Embodiment 3

[0047] like Figure 6 As shown, this embodiment is mainly a voltage divider circuit formed by a capacitor switch combination. The power supply voltage can be divided into 1 / 4 by this voltage divider circuit and then input to the comparison circuit through the first input terminal of the comparison circuit 02.

[0048] The first voltage-dividing subcircuit 04-1 includes a fourth capacitor 029, a fifth capacitor 030, a sixth capacitor 031, a ninth switch 021, a tenth switch 022, an eleventh switch 023, a twelfth switch 024, a thirteenth switch 025, a fourteenth switch 027, a fifteenth switch 026 and a sixteenth switch 028, wherein the voltage drop of the fourth capacitor 029 is 3 / 4 of the power supply voltage, the voltage drop of the fifth capacitor 030 is 1 / 2 of the power supply voltage, and the voltage drop of the sixth capacitor 031 is 1 / 4 of the power supply voltage;

[0049] One end of the ninth switch 021 is connected to the power supply, and the other end of the ninth switch 021 is connected to one end of the tenth switch 022, the eleventh switch 023, and the twelfth switch 024 in sequence;

[0050] One end of the fourth capacitor 029 is connected to the common end between the ninth switch 021 and the tenth switch 022, one end of the fifth capacitor 030 is connected to the common end between the tenth switch 022 and the eleventh switch 023, one end of the sixth capacitor 031 is connected to the common end between the eleventh switch 023 and the twelfth switch 024, and one end of the thirteenth switch 025 and the fourteenth switch 027 are both connected to the common end between the twelfth switch 024 and the first capacitor 03;

[0051] The thirteenth switch 025 is connected in series with the fifteenth switch 026, the fourteenth switch 027 is connected in series with the sixteenth switch 028, the other end of the fourth capacitor 029 is connected to the common end between the thirteenth switch 025 and the fifteenth switch 026, and the other end of the fifth capacitor 030 is connected to the common end between the fourteenth switch 027 and the sixteenth switch 028;

[0052] The other end of the sixth capacitor 031 is connected to the circuit where the other end of the fourth capacitor 029 is located;

[0053] The other end of the fifteenth switch 026, the other end of the sixteenth switch 028 and the first capacitor 03 are all connected to the equipotential node;

[0054] The ninth switch 021, the eleventh switch 023, the thirteenth switch 025 and the sixteenth switch 028 form a fifth switch combination, the tenth switch 022, the twelfth switch 024, the fourteenth switch 027 and the fifteenth switch 026 form a sixth switch combination, and by controlling the fifth switch combination and the sixth switch combination to be alternately turned on and off, the output voltage of the second voltage dividing sub-circuit 04-1 through the first capacitor 03 is 1 / 4 of the power supply voltage.

[0055] like Figure 6 As shown, this circuit is composed of 8 switches and 4 capacitors. Here, the non-overlapping dual-phase clock is used to control the four switches. In the embodiment of the present application, the voltage drop of the fourth capacitor 029 is 3 / 4VDD, the voltage drop of the fifth capacitor 030 is 1 / 2VDD, and the voltage drop of the sixth capacitor 031 is 1 / 4VDD. In the first phase stage, the fourth capacitor 029 is connected to the first capacitor 03, and the voltage drop of the fourth capacitor 029 causes the output voltage to be 1 / 4 of the power supply voltage. The lower plate of the fifth capacitor 030 is connected to the equipotential node, and the upper plate voltage of the second capacitor is 1 / 2VDD. The sixth capacitor 031 is stable at 1 / 4VDD. In the second phase stage, the fourth capacitor 029 and The fifth capacitor 030 is connected to the upper plate. Because the voltage drop of the fourth capacitor 029 is 3 / 4VDD, and the lower plate of the fourth capacitor 029 is connected to the equipotential node, the voltage of the upper plate of the fifth capacitor 030 is 3 / 4VDD, the voltage drop of the fifth capacitor 030 is 1 / 2VDD, the voltage of the lower plate of the fifth capacitor 030 is 1 / 4VDD, the lower plate of the fifth capacitor 030 is connected to the voltage output circuit, and the output voltage is 1 / 4 of the power supply voltage. The voltage drop of the sixth capacitor 031 is 1 / 4VDD, and the upper plate of the sixth capacitor 031 is connected to the voltage output terminal, outputting 1 / 4 of the power supply voltage, where VDD is the power supply voltage.

[0056] Embodiment 4

[0057] like Figure 7 As shown, in Figure 6 On the basis of the circuit shown in FIG. 1 , a second voltage-dividing subcircuit 04-2 is added, and the second voltage-dividing subcircuit 04-2 includes a seventh capacitor 036, an eighth capacitor 037, a ninth capacitor 038, a seventeenth switch 032, an eighteenth switch 033, a nineteenth switch 034, a twentieth switch 035, a twenty-first switch 039, a twenty-second switch 041, a twenty-third switch 040, and a twenty-fourth switch 042, wherein the voltage drop of the seventh capacitor 036 is 3 / 4 of the power supply voltage, the voltage drop of the eighth capacitor 037 is 1 / 2 of the power supply voltage, and the voltage drop of the ninth capacitor 038 is 1 / 4 of the power supply voltage;

[0058] One end of the seventeenth switch 032 is connected to the power supply, and the other end of the seventeenth switch 032 is connected to one end of the eighteenth switch 033, the nineteenth switch 034, and the twentieth switch 035 in sequence;

[0059] One end of the seventh capacitor 036 is connected to the common end between the seventeenth switch 032 and the eighteenth switch 033, one end of the eighth capacitor 037 is connected to the common end between the eighteenth switch 033 and the nineteenth switch 034, one end of the ninth capacitor 038 is connected to the common end between the nineteenth switch 034 and the twenty-third switch 035, and one end of the twenty-first switch 039 and the twenty-second switch 041 are both connected to the common end between the twenty-third switch 035 and the first capacitor 03;

[0060] The twenty-first switch 039 and the twenty-third switch 040 are arranged in series, the twenty-second switch 041 and the twenty-fourth switch 042 are arranged in series, the other end of the seventh capacitor 036 is connected to the common end between the twenty-first switch 039 and the twenty-third switch 040, and the other end of the eighth capacitor 037 is connected to the common end between the twenty-second switch 041 and the twenty-fourth switch 042;

[0061] The other end of the ninth capacitor 038 is connected to the circuit where the other end of the seventh capacitor 036 is located;

[0062] The other end of the 23rd switch 040, the other end of the 24th switch 042 and the first capacitor 03 are all connected to the equipotential node;

[0063] The seventeenth switch 032, the nineteenth switch 034, the twenty-first switch 039 and the twenty-fourth switch 042 form a seventh switch combination, and the eighteenth switch 033, the twentieth switch 035, the twenty-second switch 041 and the twenty-third switch 040 form an eighth switch combination. By controlling the seventh switch combination and the eighth switch combination to be alternately turned on and off, the output voltage of the second voltage dividing sub-circuit 04-2 through the first capacitor 03 is 1 / 4 of the power supply voltage;

[0064] By controlling the fifth switch combination and the eighth switch combination to be turned on, and by controlling the sixth switch combination and the seventh switch combination to be turned off; or, by controlling the fifth switch combination and the eighth switch combination to be turned off, and by controlling the sixth switch combination and the seventh switch combination to be turned on, the first voltage-dividing sub-circuit 04-1 and the second voltage-dividing sub-circuit 04-2 can uninterruptedly monitor the voltage changes of the power supply.

[0065] like Figure 6 As shown, in the third embodiment, in the second phase stage, when the fifth switch combination is turned off, the power supply voltage change information cannot be directly transmitted to the output end. This problem can be solved by the fourth embodiment, which controls the fifth switch combination in the first voltage divider sub-circuit 04-1 of one phase to be turned off, and controls the seventh switch combination in the second voltage divider sub-circuit 04-2 of another phase to be turned on; or controls the fifth switch combination in the first voltage divider sub-circuit 04-1 of one phase to be turned on, and the seventh switch combination in the second voltage divider sub-circuit 04-2 of another phase to be turned off. If the power supply voltage changes, the voltage change will be transmitted to the output end through the first capacitor 03, thereby improving the response speed. That is to say, in the fourth embodiment, the voltage change of the power supply can be continuously monitored.

[0066] Embodiment 5

[0067] like Figure 8 As shown, the first voltage-dividing sub-circuit 04-1 includes a tenth capacitor 048, an eleventh capacitor 049, a twelfth capacitor 050, a thirteenth capacitor 051, a twenty-fifth switch 043, a twenty-sixth switch 044, a twenty-seventh switch 045, a twenty-eighth switch 046, a twenty-ninth switch 047, a thirtieth switch 052, a thirty-first switch 053, a thirty-second switch 054, a thirty-third switch 055, a thirty-fourth switch 056, a thirty-fifth switch 057, a thirty-sixth switch 058 and a thirty-seventh switch 059; the voltage drop of the tenth capacitor 048 is 4 / 5 of the power supply voltage, the voltage drop of the eleventh capacitor 049 is 3 / 5 of the power supply voltage, the voltage drop of the twelfth capacitor 050 is 2 / 5 of the power supply voltage; the voltage drop of the thirteenth capacitor 051 is 1 / 5 of the power supply voltage;

[0068] One end of the 25th switch 043 is connected to the power source, and the other end of the 25th switch 043 is connected to one end of the 26th switch 044, the 27th switch 045, the 28th switch 046, and the 29th switch 047 in sequence;

[0069] One end of the tenth capacitor 048 is connected to the common end between the twenty-fifth switch 043 and the twenty-sixth switch 044, one end of the eleventh capacitor 049 is connected to the common end between the twenty-sixth switch 044 and the twenty-seventh switch 045, one end of the twelfth capacitor 050 is connected to the common end between the twenty-seventh switch 045 and the twenty-eighth switch 046, one end of the thirteenth capacitor 051 is connected to the common end between the twenty-eighth switch 046 and the twenty-ninth switch 047, one end of the first capacitor 03 is connected to the other end of the twenty-ninth switch 047; the other end of the first capacitor 03 is connected to the equipotential node;

[0070] The other end of the tenth capacitor 048 is connected to the first capacitor 03 through the 30th switch 052, and the other end of the tenth capacitor 048 is also connected to the equipotential node through the 31st switch 053;

[0071] The other end of the eleventh capacitor 049 is connected to the first capacitor 03 through the thirty-second switch 054, and the other end of the eleventh capacitor 049 is also connected to the equipotential node through the thirty-third switch 055;

[0072] The other end of the twelfth capacitor 050 is connected to the first capacitor 03 through a thirty-fourth switch 056, and the other end of the twelfth capacitor 050 is also connected to the equipotential node through a thirty-fifth switch 057;

[0073] The other end of the thirteenth capacitor 051 is connected to the first capacitor 03 through a thirty-sixth switch 058, and the other end of the thirty-sixth switch 058 is also connected to the equipotential node through a thirty-seventh switch 059;

[0074] The twenty-fifth switch 043, the twenty-seventh switch 045, the twenty-ninth switch 047, the thirtieth switch 052, the thirty-second switch 054, the thirty-fourth switch 056 and the thirty-sixth switch 058 form a ninth switch combination; the twenty-sixth switch 044, the twenty-eighth switch 046, the thirty-first switch 053, the thirty-third switch 055, the thirty-fifth switch 057 and the thirty-seventh switch 059 form a tenth switch combination; by controlling the ninth switch combination and the tenth switch combination to be alternately turned off and on, the output voltage of the first voltage divider sub-circuit 04-1 is 1 / 5 of the power supply voltage.

[0075] like Figure 8As shown, this circuit is composed of five capacitors, and a non-overlapping dual-phase clock is used to control the switch. The voltage drop of the tenth capacitor 048 is 4 / 5VDD, the voltage drop of the eleventh capacitor 049 is 3 / 5VDD, the voltage drop of the twelfth capacitor 050 is 2 / 5VDD, and the voltage drop of the thirteenth capacitor 051 is 1 / 5VDD. Through this structure, the power supply voltage is gradually reduced to the target value. In the first phase stage, the two ends of the tenth capacitor 048 are connected to the power supply and the output voltage respectively. At this time, the voltage of the tenth capacitor 048 is balanced to 4 / 5VDD. In the second phase stage, one end of the tenth capacitor 048 is connected to the equipotential node, and the other end is connected to the equipotential node. One end of the eleventh capacitor 049 is connected to the upper board of the tenth capacitor 048, and the voltage of the eleventh capacitor 049 is 4 / 5VDD. The other end of the eleventh capacitor 049 is connected to the output circuit, and the output voltage is 1 / 5VDD. When the next first phase arrives, it is transmitted to the twelfth capacitor 050 for voltage division processing until it is transmitted to the thirteenth capacitor 051. When each capacitor is working, the output voltage is 1 / 5VDD, where VDD is the power supply voltage.

[0076] Embodiment 6

[0077] like Fig. 9 As shown, in Figure 8 On the basis of the invention, a second voltage-dividing sub-circuit 05-1 is added, wherein the second voltage-dividing sub-circuit 05-1 includes a fourteenth capacitor 065, a fifteenth capacitor 066, a sixteenth capacitor 067, a seventeenth capacitor 068, a thirty-eighth switch 060, a thirty-ninth switch 061, a fortieth switch 062, a forty-first switch 063, a forty-second switch 064, a forty-third switch 069, a forty-fourth switch 070, a forty-fifth switch 071, a forty-sixth switch 072, a forty-seventh switch 073, a forty-eighth switch 074, a forty-ninth switch 075 and a fiftieth switch 076;

[0078] The voltage drop of the fourteenth capacitor 065 is 4 / 5 of the power supply voltage, the voltage drop of the fifteenth capacitor 066 is 3 / 5 of the power supply voltage, the voltage drop of the sixteenth capacitor 067 is 2 / 5 of the power supply voltage; the voltage drop of the seventeenth capacitor 068 is 1 / 5 of the power supply voltage;

[0079] One end of the 38th switch 060 is connected to the power supply, and the other end of the 38th switch 060 is connected to one end of the 39th switch 061, the 40th switch 062, the 41st switch 063, and the 42nd switch 064 in sequence;

[0080] One end of the fourteenth capacitor 065 is connected to the common end between the thirty-eighth switch 060 and the thirty-ninth switch 061, one end of the fifteenth capacitor 066 is connected to the common end between the thirty-ninth switch 061 and the fortieth switch 062, one end of the sixteenth capacitor 067 is connected to the common end between the fortieth switch 062 and the forty-first switch 063, one end of the seventeenth capacitor 068 is connected to the common end between the forty-first switch 063 and the forty-second switch 064, one end of the first capacitor 03 is connected to the other end of the forty-second switch 064, and the other end of the first capacitor 03 is connected to the equipotential node;

[0081] The other end of the fourteenth capacitor 065 is connected to the first capacitor 03 through the forty-third switch 069, and the other end of the fourteenth capacitor 065 is also connected to the equipotential node through the forty-fourth switch 070;

[0082] The other end of the fifteenth capacitor 066 is connected to the first capacitor 03 through a forty-fifth switch 071, and the other end of the fifteenth capacitor 066 is also connected to the equipotential node through a forty-sixth switch 072;

[0083] The other end of the sixteenth capacitor 067 is connected to the first capacitor 03 through a forty-seventh switch 073, and the other end of the sixteenth capacitor 067 is also connected to the equipotential node through a forty-eighth switch 074;

[0084] The other end of the seventeenth capacitor 068 is connected to the eleventh capacitor through the forty-ninth switch 075, and the other end of the seventeenth capacitor 068 is also connected to the equipotential node through the fifty-third switch 076;

[0085] The thirty-eighth switch 060, the fortieth switch 062, the forty-second switch 064, the forty-third switch 069, the forty-fifth switch 071, the forty-seventh switch 073 and the forty-ninth switch 075 form an eleventh switch combination; the thirty-ninth switch 061, the forty-first switch 063, the forty-fourth switch 070, the forty-sixth switch 072, the forty-eighth switch 074 and the fiftieth switch 076 form a twelfth switch combination; by controlling the eleventh switch combination and the twelfth switch combination to be alternately turned off and on, the output voltage of the second voltage-dividing sub-circuit 04-1 is 1 / 5 of the power supply voltage;

[0086] By controlling the ninth switch combination and the twelfth switch combination to be turned on, and by controlling the tenth switch combination and the eleventh switch combination to be turned off; or, by controlling the ninth switch combination and the twelfth switch combination to be turned off, and by controlling the tenth switch combination and the eleventh switch combination to be turned on, the first voltage-dividing sub-circuit 04-1 and the second voltage-dividing sub-circuit 04-1 can uninterruptedly monitor the voltage change of the power supply.

[0087] like Figure 8 As shown, when the output voltage drops in the second phase, the ninth switch combination is in a closed state, and the power supply voltage change information cannot be directly transmitted to the output end. Embodiment 6 can solve this problem. Fig. 9 As shown, when the ninth combination of the first voltage-dividing sub-circuit 04-1 of one phase is turned off, the eleventh switch combination of the second voltage-dividing sub-circuit 04-2 of another phase is turned on; or, when the ninth combination of the first voltage-dividing sub-circuit 04-1 of one phase is turned on, the eleventh switch combination of the second voltage-dividing sub-circuit 04-2 of another phase is turned off; if the voltage of the power supply changes, the voltage change will be transmitted to the output end through the first capacitor 03, thereby improving the response speed. That is to say, in Example 6, the voltage change of the power supply can be monitored uninterruptedly.

[0088] Embodiment 7

[0089] like Fig.10 As shown, the comparison circuit 02 includes: a first switch tube 077, a second switch tube 078, a current mirror, a first sub-circuit and a second sub-circuit;

[0090] The current mirror includes a driving tube 080 and a load tube 081 connected to each other, the first sub-circuit is connected to the driving tube 080, and the second sub-circuit is connected to the load tube 081;

[0091] The first switch tube 077 is connected to the output end of the voltage divider circuit, the second switch tube 078 is connected to the reference voltage output end, the first switch tube 077 and the second switch tube 078 are connected to a current source, the first sub-circuit is connected to the first switch tube 077, and the second sub-circuit is connected to the second switch tube 078;

[0092] The signal output circuit is connected to the common end of the load tube 081 of the current mirror and the second sub-circuit. The signal output circuit is also provided with a signal conversion circuit 088 for converting analog signals into digital signals.

[0093] When the voltage outputted by the output terminal of the voltage divider circuit is greater than the voltage outputted by the reference voltage output terminal, the first switch tube 077 is turned off, no current flows through the first sub-circuit and the current mirror, the second switch tube 078 is turned on, and the current provided by the current source flows through the second switch tube 078 and the second sub-circuit in sequence, and the signal output circuit outputs a signal indicating that the power supply is in a normal working state;

[0094] When the voltage outputted from the output end of the voltage divider circuit is less than the reference voltage, the first switch tube 077 and the second switch tube 078 are turned on at the same time, and the current provided by the current source flows through the first switch tube 077, the second switch tube 078, the first sub-circuit, the second sub-circuit and the current mirror, and the signal outputted by the signal output circuit indicates that the power supply is in an undervoltage state.

[0095] In the embodiment of the present application, the first sub-circuit includes a first NMOS transistor 082, a second NMOS transistor 083 and a third NMOS transistor 084 connected in sequence, the third NMOS transistor 084 is connected to the driving transistor 080, and the first NMOS transistor 082 is connected to the first switch transistor 077;

[0096] The second sub-circuit includes a fourth NMOS tube 085 , a fifth NMOS tube 086 and a sixth NMOS tube 087 which are connected in sequence. The sixth NMOS tube 087 is connected to the driving tube 080 , and the fourth NMOS tube 085 is connected to the second switch tube 078 .

[0097] In the embodiment of the present application, a low-power voltage comparison circuit is used to generate a final comparison result. In the embodiment of the present application, the comparison circuit 02 adopts a current mirror load mode. When the power supply undervoltage does not occur in the comparison circuit 02, only the second switch tube 078 and the second sub-circuit will consume current. When the voltage output by the output end of the voltage divider circuit is greater than the voltage output by the reference voltage output end, the first switch tube 077 is in an off state, and the bias current provided by the current source only flows through the second switch tube 078. The voltage of the common terminal A connected to the gates of the first NMOS tube 082 and the second NMOS tube 083 in the first sub-circuit is not 0, the current of the branch formed by the second NMOS tube 083 and the driving tube 080 is 0, and the fifth NMOS tube 086 and the load tube 081 branch are 0. The current of the circuit is also 0, and the overall current consumption is only the current on the second switch tube 078. When the voltage output by the output end of the voltage divider circuit is less than the voltage output by the reference voltage output end (power supply undervoltage occurs), the first switch tube 077 and the second switch tube 078 are both turned on, and the bias current also flows through the first switch tube 077. At this time, the overall current includes the sum of the currents flowing through the first sub-circuit, the first switch tube 077, the second switch tube 078, the second sub-circuit and the current mirror. Therefore, when the power supply is working normally, the comparison circuit provided by the present application consumes very little current, and when the power supply is in an undervoltage state, although the comparison circuit 02 consumes more current than when the power supply is in normal operation, the chip is in a power-off state at this time, so it will not consume current.

[0098] In a second aspect, an embodiment of the present application provides an electronic device, comprising the undervoltage detection circuit described in the first aspect.

[0099] Compared with the prior art, the beneficial effects of the electronic device provided by the second aspect are the same as the beneficial effects of the undervoltage detection circuit provided by the first aspect, which will not be described in detail here.

[0100] The electronic device may be a chip or other electronic devices.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An undervoltage detection circuit, characterized in that: It includes a voltage divider circuit and a comparison circuit; The comparison circuit comprises a first input terminal and a second input terminal; The first input terminal is connected to the output terminal of the voltage divider circuit, and the second input terminal is connected to the reference voltage output terminal. The voltage divider circuit is used to divide the power supply voltage into 1 / N power supply voltages, where N is a natural number greater than or equal to 2, and the comparison circuit is used to compare the reference voltage with the voltage output by the voltage divider circuit input at the first input terminal to determine whether the power supply is in an undervoltage state; The voltage divider circuit comprises a first voltage divider subcircuit and a first capacitor connected to each other, wherein the circuit formed by the first voltage divider subcircuit and the first capacitor is used to output a 1 / N power supply voltage; The voltage divider circuit also includes a second voltage divider sub-circuit, and the circuit composed of the second voltage divider sub-circuit and the first capacitor is used to output a voltage of 1 / N of the power supply voltage; the first voltage divider sub-circuit and the second voltage divider sub-circuit are alternately connected to the power supply to achieve uninterrupted monitoring of the voltage changes of the power supply.

2. An undervoltage detection circuit as claimed in claim 1, characterized in that: The first voltage dividing subcircuit includes a second capacitor, a first switch, a second switch, a third switch and a fourth switch; One end of the first switch is connected to the power supply, and the other end of the first switch is connected to one end of the second switch, the third switch and the fourth switch in sequence; One end of the second capacitor is connected to the common end between the first switch and the second switch, and the other end of the second capacitor is connected to the common end between the third switch and the fourth switch; One end of the first capacitor is connected to the common end between the second switch and the third switch, and the other end of the first capacitor and the other end of the fourth switch are both connected to an equipotential node; The first switch and the third switch form a first switch combination, the second switch and the fourth switch form a second switch combination, the first switch combination is turned off and the second switch combination is turned on, the first capacitor and the second capacitor are connected in parallel, and the first voltage divider sub-circuit outputs a voltage of 1 / 2 of the power supply voltage through the first capacitor; or, By controlling the first switch combination to be turned on and the second switch combination to be turned off; the first capacitor and the second capacitor are connected in series, and the first voltage divider subcircuit outputs a voltage of 1 / 2 of the power supply voltage through the first capacitor.

3. An undervoltage detection circuit as claimed in claim 2, characterized in that: The second voltage dividing sub-circuit includes a third capacitor, a fifth switch, a sixth switch, a seventh switch and an eighth switch; One end of the fifth switch is connected to the power supply, and the other end of the fifth switch is connected to one end of the sixth switch, the seventh switch and the eighth switch in sequence; One end of the third capacitor is connected to the common end between the fifth switch and the sixth switch, and the other end of the third capacitor is connected to the common end between the seventh switch and the eighth switch; One end of the first capacitor is connected to the common end between the sixth switch and the seventh switch, and the other end of the eighth switch is connected to the equipotential node; The fifth switch and the seventh switch form a third switch combination, and the sixth switch and the eighth switch form a fourth switch combination. By controlling the third switch combination to be turned off and the fourth switch combination to be turned on, the first capacitor and the second capacitor are connected in parallel, and the output voltage of the second voltage divider circuit through the first capacitor is 1 / 2 of the power supply voltage; or, by controlling the third switch combination to be turned on and the fourth switch combination to be turned off, the first capacitor and the third capacitor are connected in series; the output voltage of the second voltage divider circuit through the first capacitor is 1 / 2 of the power supply voltage; By controlling the first switch combination and the fourth switch combination to be turned on, and by controlling the second switch combination and the third switch combination to be turned off; or, by controlling the first switch combination and the fourth switch combination to be turned off, and by controlling the second switch combination and the third switch combination to be turned on, the first voltage divider sub-circuit and the second voltage divider sub-circuit can uninterruptedly monitor the voltage change of the power supply.

4. An undervoltage detection circuit as claimed in claim 1, characterized in that: The first voltage divider subcircuit includes a fourth capacitor, a fifth capacitor, a sixth capacitor, a ninth switch, a tenth switch, an eleventh switch, a twelfth switch, a thirteenth switch, a fourteenth switch, a fifteenth switch and a sixteenth switch, wherein the voltage drop of the fourth capacitor is 3 / 4 of the power supply voltage, the voltage drop of the fifth capacitor is 1 / 2 of the power supply voltage, and the voltage drop of the sixth capacitor is 1 / 4 of the power supply voltage; One end of the ninth switch is connected to the power supply, and the other end of the ninth switch is connected to one end of the tenth switch, the eleventh switch, and the twelfth switch in sequence; One end of the fourth capacitor is connected to the common end between the ninth switch and the tenth switch, one end of the fifth capacitor is connected to the common end between the tenth switch and the eleventh switch, one end of the sixth capacitor is connected to the common end between the eleventh switch and the twelfth switch, and one end of the thirteenth switch and the fourteenth switch are both connected to the common end between the twelfth switch and one end of the first capacitor; The thirteenth switch is connected in series with the fifteenth switch, the fourteenth switch is connected in series with the sixteenth switch, the other end of the fourth capacitor is connected to the common end between the thirteenth switch and the fifteenth switch, and the other end of the fifth capacitor is connected to the common end between the fourteenth switch and the sixteenth switch; The other end of the sixth capacitor is connected to the circuit where the other end of the fourth capacitor is located; The other end of the fifteenth switch, the other end of the sixteenth switch and the other end of the first capacitor are all connected to the equipotential node; The ninth switch, the eleventh switch, the thirteenth switch and the sixteenth switch form a fifth switch combination, the tenth switch, the twelfth switch, the fifteenth switch and the fourteenth switch form a sixth switch combination, and the output voltage of the second voltage divider sub-circuit through the first capacitor is 1 / 4 of the power supply voltage by controlling the fifth switch combination and the sixth switch combination to be alternately turned on and off.

5. An undervoltage detection circuit as claimed in claim 4, characterized in that: The second voltage-dividing subcircuit includes a seventh capacitor, an eighth capacitor, a ninth capacitor, a seventeenth switch, an eighteenth switch, a nineteenth switch, a twentieth switch, a twenty-first switch, a twenty-second switch, a twenty-third switch, and a twenty-fourth switch, wherein the voltage drop of the seventh capacitor is 3 / 4 of the power supply voltage, the voltage drop of the eighth capacitor is 1 / 2 of the power supply voltage, and the voltage drop of the ninth capacitor is 1 / 4 of the power supply voltage; One end of the seventeenth switch is connected to the power supply, and the other end of the seventeenth switch is connected to one end of the eighteenth switch, the nineteenth switch, and the twentieth switch in sequence; One end of the seventh capacitor is connected to the common end between the seventeenth switch and the eighteenth switch, one end of the eighth capacitor is connected to the common end between the eighteenth switch and the nineteenth switch, one end of the ninth capacitor is connected to the common end between the nineteenth switch and the twenty-tenth switch, and one end of the twenty-first switch and the twenty-second switch are both connected to the common end between the twentieth switch and one end of the fourth capacitor; The twenty-first switch and the twenty-third switch are arranged in series, the twenty-second switch and the twenty-fourth switch are arranged in series, the other end of the seventh capacitor is connected to the common end between the twenty-first switch and the twenty-third switch, and the other end of the eighth capacitor is connected to the common end between the twenty-second switch and the twenty-fourth switch; The other end of the ninth capacitor is connected to the circuit where the other end of the seventh capacitor is located; The other end of the twenty-third switch and the other end of the twenty-fourth switch are both connected to the equipotential node; The seventeenth switch, the nineteenth switch, the twenty-first switch and the twenty-fourth switch form a seventh switch combination, and the eighteenth switch, the twentieth switch, the twenty-second switch and the twenty-third switch form an eighth switch combination, and the seventh switch combination and the eighth switch combination are controlled to be alternately turned on and off, so that the output voltage of the second voltage dividing sub-circuit through the first capacitor is 1 / 4 of the power supply voltage; By controlling the fifth switch combination and the eighth switch combination to be turned on, and by controlling the sixth switch combination and the seventh switch combination to be turned off; or, by controlling the fifth switch combination and the eighth switch combination to be turned off, and by controlling the sixth switch combination and the seventh switch combination to be turned on, the first voltage divider sub-circuit and the second voltage divider sub-circuit can uninterruptedly monitor the voltage change of the power supply.

6. An undervoltage detection circuit as claimed in claim 1, characterized in that: The first voltage-dividing subcircuit includes a tenth capacitor, an eleventh capacitor, a twelfth capacitor, a thirteenth capacitor, a twenty-fifth switch, a twenty-sixth switch, a twenty-seventh switch, a twenty-eighth switch, a twenty-ninth switch, a thirtieth switch, a thirty-first switch, a thirty-second switch, a thirty-third switch, a thirty-fourth switch, a thirty-fifth switch, a thirty-sixth switch and a thirty-seventh switch; the voltage drop of the tenth capacitor is 4 / 5 of the power supply voltage, the voltage drop of the eleventh capacitor is 3 / 5 of the power supply voltage, the voltage drop of the twelfth capacitor is 2 / 5 of the power supply voltage; the voltage drop of the thirteenth capacitor is 1 / 5 of the power supply voltage; One end of the 25th switch is connected to the power supply, and the other end of the 25th switch is connected to one end of the 26th switch, the 27th switch, the 28th switch, and the 29th switch in sequence; One end of the tenth capacitor is connected to the common end between the twenty-fifth switch and the twenty-sixth switch, one end of the eleventh capacitor is connected to the common end between the twenty-sixth switch and the twenty-seventh switch, one end of the twelfth capacitor is connected to the common end between the twenty-seventh switch and the twenty-eighth switch, one end of the thirteenth capacitor is connected to the common end between the twenty-eighth switch and the twenty-ninth switch, one end of the first capacitor is connected to the other end of the twenty-ninth switch; the other end of the first capacitor is connected to the equipotential node; The other end of the tenth capacitor is connected to the first capacitor through a thirtieth switch, and the other end of the tenth capacitor is also connected to the equipotential node through a thirty-first switch; The other end of the eleventh capacitor is connected to the first capacitor through a thirty-second switch, and the other end of the eleventh capacitor is also connected to the equipotential node through a thirty-third switch; The other end of the twelfth capacitor is connected to the first capacitor through a thirty-fourth switch, and the other end of the twelfth capacitor is also connected to the equipotential node through a thirty-fifth switch; The other end of the thirteenth capacitor is connected to the first capacitor through a thirty-sixth switch, and the other end of the thirteenth capacitor is also connected to the equipotential node through a thirty-seventh switch; The 25th switch, the 27th switch, the 29th switch, the 30th switch, the 32nd switch, the 34th switch and the 36th switch form a seventh switch combination; the 26th switch, the 28th switch, the 31st switch, the 33rd switch, the 35th switch and the 37th switch form a tenth switch combination; and by controlling the ninth switch combination and the tenth switch combination to be alternately turned off and on, the output voltage of the first voltage divider sub-circuit is 1 / 5 of the power supply voltage.

7. An undervoltage detection circuit as claimed in claim 6, characterized in that: The second voltage dividing sub-circuit includes a fourteenth capacitor, a fifteenth capacitor, a sixteenth capacitor, a seventeenth capacitor, a thirty-eighth switch, a thirty-ninth switch, a forty-first switch, a forty-second switch, a forty-third switch, a forty-fourth switch, a forty-fifth switch, a forty-sixth switch, a forty-seventh switch, a forty-eighth switch, a forty-ninth switch and a fiftieth switch; The voltage drop of the fourteenth capacitor is 4 / 5 of the power supply voltage, the voltage drop of the fifteenth capacitor is 3 / 5 of the power supply voltage, the voltage drop of the sixteenth capacitor is 2 / 5 of the power supply voltage; the voltage drop of the seventeenth capacitor is 1 / 5 of the power supply voltage; One end of the thirty-eighth switch is connected to the power supply, and the other end of the thirty-eighth switch is connected to one end of the thirty-ninth switch, the fortieth switch, the forty-first switch, and the forty-second switch in sequence; One end of the fourteenth capacitor is connected to the common end between the thirty-eighth switch and the thirty-ninth switch, one end of the fifteenth capacitor is connected to the common end between the thirty-ninth switch and the fortieth switch, one end of the sixteenth capacitor is connected to the common end between the fortieth switch and the forty-first switch, one end of the seventeenth capacitor is connected to the common end between the forty-first switch and the forty-second switch, and the other end of the forty-second switch is connected to the first capacitor; the other end of the first capacitor is connected to the equipotential node; The other end of the fourteenth capacitor is connected to the first capacitor through a forty-third switch, and the other end of the fourteenth capacitor is also connected to the equipotential node through a forty-fourth switch; The other end of the fifteenth capacitor is connected to the first capacitor through a forty-fifth switch, and the other end of the fifteenth capacitor is also connected to the equipotential node through a forty-sixth switch; The other end of the sixteenth capacitor is connected to the first capacitor through a forty-seventh switch, and the other end of the sixteenth capacitor is also connected to the equipotential node through a forty-eighth switch; The other end of the seventeenth capacitor is connected to the first capacitor through a forty-ninth switch, and the other end of the seventeenth capacitor is also connected to the equipotential node through a fiftieth switch; The thirty-eighth switch, the fortieth switch, the forty-second switch, the forty-third switch, the forty-fifth switch, the forty-seventh switch and the forty-ninth switch form an eleventh switch combination; the thirty-ninth switch, the forty-first switch, the forty-fourth switch, the forty-sixth switch, the forty-eighth switch and the fiftieth switch form a twelfth switch combination; by controlling the eleventh switch combination and the twelfth switch combination to be alternately turned off and on, the output voltage of the second voltage dividing sub-circuit is 1 / 5 of the power supply voltage; By controlling the ninth switch combination and the twelfth switch combination to be turned on, and by controlling the tenth switch combination and the eleventh switch combination to be turned off; or, by controlling the ninth switch combination and the twelfth switch combination to be turned off, and by controlling the tenth switch combination and the eleventh switch combination to be turned on, the first voltage-dividing sub-circuit and the second voltage-dividing sub-circuit can uninterruptedly monitor the voltage change of the power supply.

8. An undervoltage detection circuit as claimed in claim 1, characterized in that: The comparison circuit includes a first switch tube, a second switch tube, a current mirror, a first sub-circuit and a second sub-circuit; The current mirror comprises a driving tube and a load tube connected to each other, the first sub-circuit is connected to the driving tube, and the second sub-circuit is connected to the load tube; The first switch tube is connected to a voltage divider circuit, the second switch tube is connected to a reference voltage generating circuit, the first switch tube and the second switch tube are both connected to a current source, the first sub-circuit is connected to the first switch tube, and the second sub-circuit is connected to the second switch tube; The common end between the load tube of the current mirror and the second sub-circuit is connected to the signal output circuit; When the voltage outputted by the output terminal of the voltage divider circuit is greater than the voltage outputted by the reference voltage output terminal, the first switch tube is turned off, no current flows through the first sub-circuit and the current mirror, the second switch tube is turned on, the current provided by the current source flows through the second switch tube and the second sub-circuit in sequence, and the signal output circuit outputs a signal indicating that the power supply is in a normal working state; When the voltage outputted from the output end of the voltage divider circuit is less than the reference voltage, the first switch tube and the second switch tube are turned on, and the current provided by the current source flows through the first switch tube, the second switch tube, the first sub-circuit, the second sub-circuit and the current mirror, and a signal is outputted through the signal output circuit to indicate that the power supply is in an undervoltage state.

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