A main and standby power supply switching circuit and an electronic device

Abstract

The present invention discloses a main and standby power supply switching circuit and an electronic device, belonging to the technical field of power supplies. Among them, the main and standby power supply switching circuit includes a first switch module to a fourth switch module connected in sequence; the control end of the first switch module is connected to the main power supply, the input end of the fourth switch module is connected to the standby power supply, the output end is respectively connected to the main power supply and the system power supply output end, and the control end is connected to the third switch module. By using the main and standby power supply switching circuit of the embodiment of the present invention, under the control of the main power supply, through the mutual cooperation of the four switch modules, it can be realized that when the main power supply stops power supply, it is switched to the standby power supply instantaneously, and after a preset delay when the main power supply starts to supply power, the standby power supply stops power supply, so as to completely solve the problem of unstable operation of the electronic device caused by power supply switching. Moreover, compared with the scheme of increasing the load capacitance, the main and standby power supply switching circuit not only saves the layout space but also reduces the product cost.

Description

Technical Field

[0001] The present invention relates to the technical field of power supplies, and particularly to a main and backup power supply switching circuit and an electronic device. Background Art

[0002] Currently, many electronic devices support two power supply modes, namely a main power supply and a backup power supply. When the main power supply is present, the main power supply supplies power and the backup power supply does not work. When the main power supply is not present, the backup power supply supplies power. For example, products such as OBD (On-Board Diagnostics) and Tracker (position tracking device) are such electronic devices. The advantage of this power supply mode is that the electronic device can still work normally through the backup power supply when the main power supply is not present. Moreover, since the main power supply is supported, the requirement for the capacity of the backup power supply is reduced.

[0003] However, because two power supply modes are supported, there are switching scenarios for the two power supplies in such electronic devices, and it is necessary to ensure that the normal operation of the electronic device is not affected during the switching. Although there are corresponding solutions in the current industry to solve the problem of power supply switching, such as compensating for the voltage drop during the power supply switching process by increasing the load capacitance, this method does not substantially solve the problem, and at the same time, increasing the load capacitance increases the layout space and product cost. Therefore, there is an urgent need for a new main and backup power supply switching solution. Summary of the Invention

[0004] In view of this, the purpose of the embodiments of the present invention is to provide a main and backup power supply switching circuit and an electronic device to solve the technical problems of increasing the layout space and product cost caused by currently compensating for the voltage drop during the power supply switching process of the electronic device by increasing the load capacitance.

[0005] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0006] According to one aspect of the embodiments of the present invention, a main and backup power supply switching circuit is provided. The main and backup power supply switching circuit includes a first switch module to a fourth switch module connected in sequence;

[0007] The control end of the first switch module is connected to the main power supply, and is used to control the second switch module to be disconnected when the main power supply is present, and control the second switch module to be turned on when the main power supply is not present;

[0008] The second switch module is used to cooperate with the main power supply to jointly control the conduction and disconnection of the third switch module;

[0009] The third switch module is configured to control the fourth switch module to disconnect when the main power supply is present; control the fourth switch module to conduct instantaneously when the main power supply switches from being present to not being present; control the fourth switch module to conduct when the main power supply is not present; and control the fourth switch module to disconnect after a preset delay when the main power supply switches from not being present to being present.

[0010] The input end of the fourth switch module is connected to the backup power supply, the output end is respectively connected to the main power supply and the system power supply output end, and the control end is connected to the third switch module. It is configured to control the connection between the backup power supply and the system power supply output end when it conducts itself, and control the disconnection of the connection between the backup power supply and the system power supply output end when it disconnects itself.

[0011] Optionally, the first switch module includes a first MOS transistor, a first resistor, and a second resistor.

[0012] One end of the first resistor is connected to the main power supply, and the other end is respectively connected to the third switch module, one end of the second resistor, and the gate of the first MOS transistor. The drain of the first MOS transistor is connected to the second switch module, and the other end of the second resistor and the source of the first MOS transistor are grounded.

[0013] Optionally, the second switch module includes a second MOS transistor and a third resistor.

[0014] One end of the third resistor is connected to the first power supply, and the other end is respectively connected to the drain of the first MOS transistor and the gate of the second MOS transistor. The drain of the second MOS transistor is connected to the third switch module, and the source is grounded, where the first power supply is a power supply capable of turning on the second MOS transistor.

[0015] Optionally, the third switch module includes a third MOS transistor, a diode, a first capacitor, a fourth resistor, and a fifth resistor.

[0016] The positive electrode of the diode is connected to the other end of the first resistor, and the negative electrode is connected to one end of the fourth resistor. The other end of the fourth resistor is respectively connected to one end of the fifth resistor, the gate of the third MOS transistor, and one end of the first capacitor. The other end of the fifth resistor is connected to the drain of the second MOS transistor. The drain of the third MOS transistor is connected to the control end of the fourth switch module, and the source and the other end of the first capacitor are grounded.

[0017] Optionally, the resistance value of the fifth resistor is not greater than 100 ohms.

[0018] Optionally, the resistance value of the fourth resistor is not less than 1000 ohms.

[0019] Optionally, the fourth switch module includes a switching element, a second capacitor, and a sixth resistor;

[0020] The input end of the switching element is connected to the backup power supply, the output end is respectively connected to the main power supply and the system power output end, the control end is respectively connected to the drain of the third MOS transistor and one end of the sixth resistor, the grounding end is grounded, the other end of the sixth resistor is connected to the second power supply, and the system power output end is grounded through the second capacitor, where the second power supply is a power supply capable of turning on the switching element.

[0021] Optionally, the main and backup power supply switching circuit further includes a DCDC module (a module that converts electrical energy from one voltage value to another voltage value), and the main power supply is connected to the system power output end through the DCDC module.

[0022] Optionally, when the main power supply is at a high level, the first MOS transistor is turned on because its gate is at a high level, the second MOS transistor is turned off because its gate is pulled low by the first MOS transistor, and the third MOS transistor is turned on because its gate is pulled high through the first resistor, the diode, and the fourth resistor, thereby pulling down the control end of the switching element to turn off the switching element, so as to control the disconnection between the backup power supply and the system power output end. At this time, the main power supply connected to the system power output end supplies power;

[0023] When the main power supply switches from a high level to a low level, the first MOS transistor is turned off because its gate is at a low level, the second MOS transistor is turned on because its gate is pulled high by the first power supply, the voltage of the gate of the third MOS transistor remains at a high level instantaneously due to the presence of the first capacitor during the switching. After that, the first capacitor discharges through the fifth resistor, and the discharge is completed instantaneously. The third MOS transistor is turned off because the voltage of its gate drops to a low level, and the switching element is turned on because its control end is pulled high by the second power supply, thereby controlling the connection between the backup power supply and the system power output end. Thus, power supply is switched to the backup power supply instantaneously when the main power supply stops supplying power;

[0024] When the main power supply is at a low level, the first MOS transistor is turned off because its gate is at a low level, the second MOS transistor is turned on because its gate is pulled high by the first power supply, the third MOS transistor is turned off because its gate is pulled low by the fifth resistor, and the switching element is turned on because its control end is pulled high by the second power supply, so as to control the connection between the backup power supply and the system power output end. At this time, the backup power supply connected to the system power output end supplies power;

[0025] When the main power supply switches from a low level to a high level, the first MOS transistor conducts because its gate is at a high level, the second MOS transistor cuts off because its gate is pulled low by the first MOS transistor, and due to the presence of the first capacitor, the voltage at the gate of the third MOS transistor remains at a low level at the moment of switching. After that, the first capacitor is charged through the fourth resistor. After a preset delay, the voltage at the gate of the third MOS transistor rises to a high level due to the charging of the first capacitor, and the third MOS transistor conducts, pulling down the control terminal of the switching element, causing the switching element to disconnect, thereby controlling the disconnection between the backup power supply and the system power output terminal. Thus, after a preset delay when the main power supply starts to supply power, the backup power supply stops supplying power.

[0026] According to another aspect of the embodiments of the present invention, there is provided an electronic device, which includes the above-mentioned main and backup power supply switching circuit.

[0027] The main and backup power supply switching circuit and the electronic device provided by the embodiments of the present invention include a first switching module to a fourth switching module connected in sequence; the control terminal of the first switching module is connected to the main power supply, and is used to control the disconnection of the second switching module when the main power supply is present, and control the conduction of the second switching module when the main power supply is absent; the second switching module is used to cooperate with the main power supply to jointly control the conduction and disconnection of the third switching module; the third switching module is used to control the disconnection of the fourth switching module when the main power supply is present; control the fourth switching module to conduct instantaneously when the main power supply switches from being present to absent; control the fourth switching module to conduct when the main power supply is absent; control the fourth switching module to disconnect after a preset delay when the main power supply switches from being absent to present; the input terminal of the fourth switching module is connected to the backup power supply, the output terminal is respectively connected to the main power supply and the system power output terminal, and the control terminal is connected to the third switching module, and is used to control the connection between the backup power supply and the system power output terminal when it conducts itself, and control the disconnection of the connection between the backup power supply and the system power output terminal when it disconnects itself. By adopting the main and backup power supply switching circuit of the embodiments of the present invention, it can switch to the backup power supply for power supply at the moment when the main power supply stops supplying power, and stop the backup power supply from supplying power after a preset delay when the main power supply starts to supply power, that is, after the main power supply starts to stably supply power, thereby completely solving the problem of unstable operation of the electronic device caused by power supply switching. Moreover, compared with the scheme of increasing the load capacitance, this main and backup power supply switching circuit not only saves layout space but also reduces product cost. Further, this main and backup power supply switching scheme is completely implemented by a hardware circuit, and has high working reliability. Description of the Drawings

[0028] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0029] Figure 1 It is a schematic diagram of an implementation manner of the main and standby power supply switching circuit provided by an embodiment of the present invention;

[0030] Figure 2 It is a circuit connection schematic diagram of an implementation manner of the main and standby power supply switching circuit provided by an embodiment of the present invention;

[0031] Figure 3 It is a schematic diagram of another implementation manner of the main and standby power supply switching circuit provided by an embodiment of the present invention. Specific Embodiment

[0032] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] In subsequent descriptions, suffixes such as "module", "component", or "unit" used to represent elements are only for the convenience of explaining the present invention, and they have no specific meaning in themselves. Therefore, "module", "component", or "unit" can be used interchangeably.

[0034] Embodiment 1

[0035] In order to solve the technical problems of increasing the layout space and product cost caused by increasing the load capacitance to make up for the voltage drop during the power supply switching process of electronic devices, this embodiment provides a main and standby power supply switching circuit. Please refer to Figure 1 , Figure 1 It is a schematic diagram of an implementation manner of the main and standby power supply switching circuit provided by an embodiment of the present invention. The main and standby power supply switching circuit includes a first switch module 1 to a fourth switch module 4 connected in sequence;

[0036] The control end of the first switch module 1 is connected to the main power supply, and is used to control the second switch module 2 to be disconnected when the main power supply is present, and control the second switch module 2 to be turned on when the main power supply is absent;

[0037] The second switch module 2 is used to cooperate with the main power supply to jointly control the conduction and disconnection of the third switch module 3;

[0038] The third switch module 3 is used to control the fourth switch module 4 to be disconnected when the main power supply is present; control the fourth switch module 4 to be turned on instantaneously when the main power supply switches from being present to absent; control the fourth switch module 4 to be turned on when the main power supply is absent; control the fourth switch module 4 to be disconnected after a preset delay when the main power supply switches from being absent to present;

[0039] The input end of the fourth switch module 4 is connected to the backup power supply, the output ends are respectively connected to the main power supply and the system power supply output end OUT, and the control end is connected to the third switch module 3, and is used to control the connection between the backup power supply and the system power supply output end OUT when it is turned on itself, and control the disconnection of the connection between the backup power supply and the system power supply output end OUT when it is turned off itself.

[0040] In this embodiment, it should be noted first that the main and backup power supply switching circuit of this embodiment is applicable to electronic devices that support two power supply modes of main power supply and backup power supply.

[0041] Specifically, the control end of the first switch module 1 is connected to the main power supply, and controls the second switch module 2 to be turned off when the main power supply is present, and controls the second switch module 2 to be turned on when the main power supply is absent. The second switch module 2 cooperates with the presence state of the main power supply through the change of its own on and off states to jointly control the on and off of the third switch module 3. The third switch module 3 controls the fourth switch module 4 to be turned off when the main power supply is present; controls the fourth switch module 4 to be turned on instantaneously when the main power supply changes from present to absent; controls the fourth switch module 4 to be turned on when the main power supply is absent; controls the fourth switch module 4 to be turned off after a preset delay when the main power supply changes from absent to present. The input end of the fourth switch module 4 is connected to the backup power supply, the output ends are respectively connected to the main power supply and the system power supply output end OUT, and the control end is connected to the third switch module 3, and controls the connection between the backup power supply and the system power supply output end OUT when it is turned on itself, and controls the disconnection of the connection between the backup power supply and the system power supply output end OUT when it is turned off itself. Thus, under the control of the main power supply, through the mutual cooperation of the four switch modules, it is realized that when the main power supply stops supplying power, it switches to the backup power supply for power supply instantaneously, and after a preset delay when the main power supply starts supplying power, that is, after the main power supply starts to supply power stably, the backup power supply stops supplying power, so that the problem of unstable operation of electronic devices caused by power supply switching can be completely solved. Moreover, compared with the scheme of increasing the load capacitance, this main and backup power supply switching circuit not only saves layout space but also reduces product cost. Further, this main and backup power supply switching circuit is completely implemented by a hardware circuit, and has high working reliability.

[0042] In one implementation, please refer to Figure 2 , Figure 2FIG. 0 is a schematic circuit connection diagram of an implementation manner of the main and standby power supply switching circuit provided by an embodiment of the present invention. Herein, taking the main power supply as the KL30 power supply of an automobile as an example. The first switch module 1 includes a first MOS transistor VT1, a first resistor R1, and a second resistor R2; one end of the first resistor R1 is connected to the main power supply, and the other end is respectively connected to the third switch module 3, one end of the second resistor R2, and the gate of the first MOS transistor VT1. The drain of the first MOS transistor VT1 is connected to the second switch module 2, and the other end of the second resistor R2 and the source of the first MOS transistor VT1 are grounded.

[0043] In this embodiment, the first switch module 1 may, but is not limited to, adopt a first MOS transistor VT1, a first resistor R1, and a second resistor R2. The first MOS transistor VT1 may, but is not limited to, adopt an N-channel MOS transistor. When the main power supply is in place, the first MOS transistor VT1 is turned on because its gate is at a high level; when the main power supply is not in place, the first MOS transistor VT1 is turned off because its gate is at a low level. Among them, the first resistor R1 is a current-limiting resistor, and the second resistor R2 is used to ensure the reliable operation of the first MOS transistor VT1.

[0044] In one implementation, please refer to Figure 2 , the second switch module 2 includes a second MOS transistor VT2 and a third resistor R3; one end of the third resistor R3 is connected to the first power supply, and the other end is respectively connected to the drain of the first MOS transistor VT1 and the gate of the second MOS transistor VT2. The drain of the second MOS transistor VT2 is connected to the third switch module 3, and the source is grounded. Herein, the first power supply is a power supply capable of turning on the second MOS transistor VT2, Figure 2 In

[0045] In this embodiment, the second switch module 2 may, but is not limited to, adopt a second MOS transistor VT2 and a third resistor R3. The second MOS transistor VT2 may, but is not limited to, adopt an N-channel MOS transistor. When the main power supply is in place, the first MOS transistor VT1 is turned on because its gate is at a high level, thereby pulling down the gate of the second MOS transistor VT2, making the second MOS transistor VT2 turn off; when the main power supply is not in place, the first MOS transistor VT1 is turned off because its gate is at a low level, and the second MOS transistor VT2 is turned on because its gate is pulled up by the first power supply. Among them, the third resistor R3 is a current-limiting resistor.

[0046] In one implementation, please refer to Figure 2, the third switching module 3 includes a third MOS transistor VT3, a diode D1, a first capacitor C1, a fourth resistor R4, and a fifth resistor R5; the positive electrode of the diode D1 is connected to the other end of the first resistor R1, and the negative electrode is connected to one end of the fourth resistor R4. The other end of the fourth resistor R4 is respectively connected to one end of the fifth resistor R5, the gate of the third MOS transistor VT3, and one end of the first capacitor C1. The other end of the fifth resistor R5 is connected to the drain of the second MOS transistor VT2. The drain of the third MOS transistor VT3 is connected to the control end of the fourth switching module 4, and the source and the other end of the first capacitor C1 are grounded.

[0047] In this embodiment, the third switching module 3 may, but is not limited to, adopt a third MOS transistor VT3, a diode D1, a first capacitor C1, a fourth resistor R4, and a fifth resistor R5. The third MOS transistor VT3 may, but is not limited to, adopt an N-channel MOS transistor. When the main power supply is present, the first MOS transistor VT1 is turned on because its gate is at a high level, thereby pulling down the gate of the second MOS transistor VT2, causing the second MOS transistor VT2 to turn off. The third MOS transistor VT3 is turned on because its gate is pulled high through the first resistor R1, the diode D1, and the fourth resistor R4. When the main power supply switches from being present to not being present, the first MOS transistor VT1 is turned off because its gate is at a low level. The second MOS transistor VT2 is turned on because its gate is pulled high by the first power supply. Due to the presence of the first capacitor C1, the voltage of the gate of the third MOS transistor VT3 remains at a high level at the moment of switching. After that, the first capacitor C1 discharges through the fifth resistor R5, and the discharge is completed instantaneously. The third MOS transistor VT3 is turned off because the voltage of its gate drops to a low level. When the main power supply is not present, the first MOS transistor VT1 is turned off because its gate is at a low level. The second MOS transistor VT2 is turned on because its gate is pulled high by the first power supply. The third MOS transistor VT3 is turned off because its gate is pulled low by the fifth resistor R5. When the main power supply switches from not being present to being present, the first MOS transistor VT1 is turned on because its gate is at a high level. The second MOS transistor VT2 is turned off because its gate is pulled down by the first MOS transistor VT1. Due to the presence of the first capacitor C1, the voltage of the gate of the third MOS transistor VT3 remains at a low level at the moment of switching. After that, the first capacitor C1 is charged through the fourth resistor R4. After a preset delay, the voltage of the gate of the third MOS transistor VT3 rises to a high level due to the charging of the first capacitor C1, and the third MOS transistor VT3 is turned on. Among them, the diode D1 plays a role of unidirectional conduction. The fourth resistor R4 is the charging resistor of the first capacitor C1. By adjusting the values of the fourth resistor R4 and the first capacitor C1, the charging time of the first capacitor C1 can be adjusted, thereby realizing the adjustment of the preset delay. This preset delay can be set according to the actual usage scenario to meet different actual usage requirements. The specific value of this embodiment is not limited. The fifth resistor R5 is the discharging resistor of the first capacitor C1. By adjusting the values of the fifth resistor R5 and the first capacitor C1, the discharging time of the first capacitor C1 can be adjusted, thereby realizing the adjustment of the time for switching to the backup power supply when the main power supply loses power. In order to switch to the backup power supply as soon as possible when the main power supply loses power, the value of the fifth resistor R5 is generally small. Specifically, the fifth resistor R5 can be selected according to the actual usage scenario to meet different actual usage requirements. The specific value of this embodiment is not limited.

[0048] Optionally, the resistance value of the fifth resistor R5 is not greater than 100 ohms to shorten the discharge time of the first capacitor C1 and switch to the backup power supply as soon as possible when the main power supply loses power. For example, a 22-ohm resistor is selected as the fifth resistor R5.

[0049] Optionally, the resistance value of the fourth resistor R4 is not less than 1000 ohms to extend the charging time of the first capacitor C1 and cut off the backup power supply after a longer delay when the main power supply is powered on, leaving sufficient time for the main power supply to be stable from power-on to power supply. For example, a 330K-ohm resistor is selected as the fourth resistor R4.

[0050] In one embodiment, please refer to Figure 2 , the fourth switch module 4 includes a switching element SW, a second capacitor C2, and a sixth resistor R6; the input end of the switching element SW is connected to the backup power supply, the output end is respectively connected to the main power supply and the system power output terminal OUT, the control end is respectively connected to the drain of the third MOS transistor VT3 and one end of the sixth resistor R6, the ground terminal is grounded, the other end of the sixth resistor R6 is connected to the second power supply, and the system power output terminal OUT is grounded through the second capacitor C2, where the second power supply is a power supply capable of turning on the switching element SW. Figure 2 Taking the second power supply as a 3.3V power supply, the backup power supply as a lithium battery LI_VBAT, and the system power supply voltage as 4V as an example in

[0051] In this embodiment, the fourth switch module 4 may but is not limited to adopting a switching element SW, a second capacitor C2, and a sixth resistor R6. When the main power supply is present, the first MOS transistor VT1 is turned on because its gate is at a high level, thereby pulling down the gate of the second MOS transistor VT2, causing the second MOS transistor VT2 to turn off. The third MOS transistor VT3 is turned on because its gate is pulled high through the first resistor R1, the diode D1, and the fourth resistor R4, thereby pulling down the control terminal of the switching element SW, turning off the switching element SW, and thus controlling the disconnection of the backup power supply from the system power supply output terminal OUT. At this time, the main power supply connected to the system power supply output terminal OUT supplies power. When the main power supply switches from being present to not being present, the first MOS transistor VT1 is turned off because its gate is at a low level. The second MOS transistor VT2 is turned on because its gate is pulled high by the first power supply. Due to the existence of the first capacitor C1, the voltage of the gate of the third MOS transistor VT3 remains at a high level at the moment of switching. Subsequently, the first capacitor C1 discharges through the fifth resistor R5, and the discharge is completed instantaneously. The third MOS transistor VT3 is turned off because the voltage of its gate drops to a low level. The switching element SW is turned on because its control terminal is pulled high by the second power supply, thereby controlling the connection of the backup power supply to the system power supply output terminal OUT. Thus, at the moment when the main power supply stops supplying power, it switches to being powered by the backup power supply. When the main power supply is not present, the first MOS transistor VT1 is turned off because its gate is at a low level. The second MOS transistor VT2 is turned on because its gate is pulled high by the first power supply. The third MOS transistor VT3 is turned off because its gate is pulled low by the fifth resistor R5. The switching element SW is turned on because its control terminal is pulled high by the second power supply, thereby controlling the connection of the backup power supply to the system power supply output terminal OUT. At this time, the backup power supply connected to the system power supply output terminal OUT supplies power. When the main power supply switches from not being present to being present, the first MOS transistor VT1 is turned on because its gate is at a high level. The second MOS transistor VT2 is turned off because its gate is pulled down by the first MOS transistor VT1. Due to the existence of the first capacitor C1, the voltage of the gate of the third MOS transistor VT3 remains at a low level at the moment of switching. Subsequently, the first capacitor C1 is charged through the fourth resistor R4. After a preset delay, the voltage of the gate of the third MOS transistor VT3 rises to a high level due to the charging of the first capacitor C1, and the third MOS transistor VT3 is turned on, pulling down the control terminal of the switching element SW, turning off the switching element SW, and thus controlling the disconnection of the backup power supply from the system power supply output terminal OUT. Thus, after a preset delay when the main power supply starts supplying power, the backup power supply stops supplying power. Among them, the second capacitor C2 is a filtering capacitor, and the sixth resistor R6 is a current-limiting resistor.

[0052] Optionally, please refer to Figure 2 andFigure 3 , Figure 3 is a schematic diagram of another implementation of the main and backup power supply switching circuit provided by an embodiment of the present invention. The main and backup power supply switching circuit further includes a DCDC module 5, and the main power supply is connected to the system power supply output terminal OUT through the DCDC module 5.

[0053] Specifically, the main power supply performs voltage conversion through the DCDC module 5, changing its voltage from the voltage of the main power supply to the voltage corresponding to the system power supply of the electronic device. When the main power supply switches from being absent to being present, the DCDC module 5 uses the preset delay to complete the voltage conversion. After the output of the DCDC module 5 is stable, the backup power supply is cut off, and the main power supply starts to supply power to the electronic device through the DCDC module 5.

[0054] The working principle of the main and standby power supply switching circuit in this embodiment is as follows: When the main power supply is at a high level, the first MOS transistor VT1 is turned on because its gate is at a high level. The second MOS transistor VT2 is turned off because its gate is pulled low by the first MOS transistor VT1. The third MOS transistor VT3 is turned on because its gate is pulled high through the first resistor R1, diode D1, and fourth resistor R4, thereby pulling down the control terminal of the switching element SW, causing the switching element SW to disconnect, and thus controlling the disconnection of the standby power supply from the system power supply output terminal OUT. At this time, the main power supply connected to the system power supply output terminal OUT supplies power. When the main power supply switches from a high level to a low level, the first MOS transistor VT1 is turned off because its gate is at a low level. The second MOS transistor VT2 is turned on because its gate is pulled high by the first power supply. Due to the existence of the first capacitor C1, the voltage at the gate of the third MOS transistor VT3 remains at a high level instantaneously during the switching. Then, the first capacitor C1 discharges through the fifth resistor R5, and the discharge is completed instantaneously. The third MOS transistor VT3 is turned off because the voltage at its gate drops to a low level. The switching element SW is turned on because its control terminal is pulled high by the second power supply, and then it controls the connection of the standby power supply to the system power supply output terminal OUT. Thus, at the instant when the main power supply stops supplying power, it switches to the standby power supply for power supply. When the main power supply is at a low level, the first MOS transistor VT1 is turned off because its gate is at a low level. The second MOS transistor VT2 is turned on because its gate is pulled high by the first power supply. The third MOS transistor VT3 is turned off because its gate is pulled low by the fifth resistor R5. The switching element SW is turned on because its control terminal is pulled high by the second power supply, thereby controlling the connection of the standby power supply to the system power supply output terminal OUT. At this time, the standby power supply connected to the system power supply output terminal OUT supplies power. When the main power supply switches from a low level to a high level, the first MOS transistor VT1 is turned on because its gate is at a high level. The second MOS transistor VT2 is turned off because its gate is pulled low by the first MOS transistor VT1. Due to the existence of the first capacitor C1, the voltage at the gate of the third MOS transistor VT3 remains at a low level instantaneously during the switching. Then, the first capacitor C1 is charged through the fourth resistor R4. After a preset delay, the voltage at the gate of the third MOS transistor VT3 rises to a high level due to the charging of the first capacitor C1, and the third MOS transistor VT3 is turned on, pulling down the control terminal of the switching element SW, causing the switching element SW to disconnect, and then controlling the disconnection of the standby power supply from the system power supply output terminal OUT. Thus, after a preset delay when the main power supply starts supplying power, the standby power supply stops supplying power.

[0055] The main and standby power supply switching circuit in this embodiment includes a first switch module 1 to a fourth switch module 4 connected in sequence; the control end of the first switch module 1 is connected to the main power supply, and is used to control the second switch module 2 to be disconnected when the main power supply is present, and control the second switch module 2 to be turned on when the main power supply is absent; the second switch module 2 is used to cooperate with the main power supply to jointly control the on and off of the third switch module 3; the third switch module 3 is used to control the fourth switch module 4 to be disconnected when the main power supply is present; when the main power supply switches from being present to absent, control the fourth switch module 4 to be turned on instantaneously; when the main power supply is absent, control the fourth switch module 4 to be turned on; when the main power supply switches from being absent to present, control the fourth switch module 4 to be disconnected after a preset delay; the input end of the fourth switch module 4 is connected to the standby power supply, the output end is respectively connected to the main power supply and the system power supply output terminal OUT, and the control end is connected to the third switch module 3, and is used to control the standby power supply to be connected to the system power supply output terminal OUT when it is turned on, and control the disconnection of the connection between the standby power supply and the system power supply output terminal OUT when it is turned off. By adopting the main and standby power supply switching circuit of the embodiment of the present invention, it can switch to the standby power supply for power supply instantaneously when the main power supply stops power supply, and stop the standby power supply after a preset delay when the main power supply starts power supply, that is, after the main power supply starts to supply power stably, so as to completely solve the problem of unstable operation of electronic devices caused by power supply switching. Moreover, compared with the scheme of increasing the load capacitance, it not only saves layout space but also reduces product cost. Further, this main and standby power supply switching scheme is completely implemented by a hardware circuit, and has high working reliability.

[0056] Embodiment 2

[0057] This embodiment provides an electronic device, and this electronic device includes the main and standby power supply switching circuit of the above-mentioned Embodiment 1. The electronic device of this embodiment can switch to the standby power supply for power supply instantaneously when the main power supply stops power supply, and stop the standby power supply after a preset delay when the main power supply starts power supply, that is, after the main power supply starts to supply power stably, so as to completely solve the problem of unstable operation of electronic devices caused by power supply switching. Moreover, compared with the scheme of increasing the load capacitance, it not only saves layout space but also reduces product cost. Further, this main and standby power supply switching scheme is completely implemented by a hardware circuit, and has high working reliability. The specific structure of the main and standby power supply switching circuit is as described in the above-mentioned Embodiment 1, and will not be elaborated here.

[0058] The corresponding technical features in the above-mentioned embodiments can be used with each other on the premise that they do not cause contradictions or inapplicability of the scheme.

[0059] It should be noted that in this text, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent in such a process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including that element.

[0060] The serial numbers of the embodiments of the present invention above are only for description and do not represent the advantages or disadvantages of the embodiments.

[0061] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative rather than restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit and scope protected by the claims of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A main and standby power supply switching circuit, characterized in that, The main and backup power supply switching circuit includes a first switch module to a fourth switch module connected in sequence; The control end of the first switch module is connected to the main power supply, and is used to control the second switch module to be disconnected when the main power supply is present, and control the second switch module to be conducted when the main power supply is absent; The second switch module is used to cooperate with the main power supply to jointly control the conduction and disconnection of the third switch module; The third switch module is used to control the fourth switch module to be disconnected when the main power supply is present; control the fourth switch module to be conducted instantaneously when the main power supply switches from being present to absent; control the fourth switch module to be conducted when the main power supply is absent; control the fourth switch module to be disconnected after a preset delay when the main power supply switches from being absent to present; The input end of the fourth switch module is connected to the backup power supply, the output end is respectively connected to the main power supply and the system power supply output end, and the control end is connected to the third switch module, and is used to control the connection between the backup power supply and the system power supply output end when it is conducted, and control the disconnection of the connection between the backup power supply and the system power supply output end when it is disconnected; Among them, the first switch module includes a first MOS transistor, a first resistor and a second resistor; one end of the first resistor is connected to the main power supply, and the other end is respectively connected to the third switch module, one end of the second resistor and the gate of the first MOS transistor, the drain of the first MOS transistor is connected to the second switch module, and the other end of the second resistor and the source of the first MOS transistor are grounded; The second switch module includes a second MOS transistor and a third resistor; one end of the third resistor is connected to the first power supply, and the other end is respectively connected to the drain of the first MOS transistor and the gate of the second MOS transistor, the drain of the second MOS transistor is connected to the third switch module, and the source is grounded, where the first power supply is a power supply that can make the second MOS transistor conduct; The third switch module includes a third MOS transistor, a diode, a first capacitor, a fourth resistor and a fifth resistor; the positive electrode of the diode is connected to the other end of the first resistor, and the negative electrode is connected to one end of the fourth resistor, the other end of the fourth resistor is respectively connected to one end of the fifth resistor, the gate of the third MOS transistor and one end of the first capacitor, the other end of the fifth resistor is connected to the drain of the second MOS transistor, the drain of the third MOS transistor is connected to the control end of the fourth switch module, and the source and the other end of the first capacitor are grounded; The fourth switch module includes a switching element, a second capacitor and a sixth resistor; the input end of the switching element is connected to the backup power supply, the output end is respectively connected to the main power supply and the system power supply output end, the control end is respectively connected to the drain of the third MOS transistor and one end of the sixth resistor, and the grounding end is grounded, the other end of the sixth resistor is connected to the second power supply, and the system power supply output end is grounded through the second capacitor, where the second power supply is a power supply that can make the switching element conduct; 2. The main and standby power supply switching circuit according to claim 1, wherein The resistance value of the fifth resistor is not greater than 100 ohms.

3. The main and standby power supply switching circuit according to claim 1, characterized in that, The resistance value of the fourth resistor is not less than 1000 ohms.

4. The main and standby power supply switching circuit according to any one of claims 1-3, characterized in that, The main and standby power supply switching circuit further includes a DCDC module, and the main power supply is connected to the system power supply output terminal through the DCDC module.

5. The main and standby power supply switching circuit according to claim 1, wherein When the main power supply is at a high level, the first MOS transistor is turned on because its gate is at a high level, the second MOS transistor is turned off because its gate is pulled low by the first MOS transistor, and the third MOS transistor is turned on because its gate is pulled high through the first resistor, diode and fourth resistor, thereby pulling down the control terminal of the switching element, turning off the switching element, and controlling the disconnection of the standby power supply from the system power supply output terminal. At this time, the main power supply connected to the system power supply output terminal supplies power. When the main power supply switches from a high level to a low level, the first MOS transistor is turned off because its gate is at a low level, the second MOS transistor is turned on because its gate is pulled high by the first power supply, and the voltage of the gate of the third MOS transistor remains at a high level at the moment of switching due to the existence of the first capacitor. Then, the first capacitor discharges through the fifth resistor, and the discharge is completed instantaneously. The third MOS transistor is turned off because the voltage of its gate drops to a low level, and the switching element is turned on because its control terminal is pulled high by the second power supply, thereby controlling the connection of the standby power supply to the system power supply output terminal. Thus, at the moment when the main power supply stops supplying power, it switches to the standby power supply for power supply. When the main power supply is at a low level, the first MOS transistor is turned off because its gate is at a low level, the second MOS transistor is turned on because its gate is pulled high by the first power supply, the third MOS transistor is turned off because its gate is pulled low by the fifth resistor, and the switching element is turned on because its control terminal is pulled high by the second power supply, thereby controlling the connection of the standby power supply to the system power supply output terminal. At this time, the standby power supply connected to the system power supply output terminal supplies power. When the main power supply switches from a low level to a high level, the first MOS transistor is turned on because its gate is at a high level, the second MOS transistor is turned off because its gate is pulled low by the first MOS transistor, and the voltage of the gate of the third MOS transistor remains at a low level at the moment of switching due to the existence of the first capacitor. Then, the first capacitor charges through the fourth resistor, and after a preset delay, the voltage of the gate of the third MOS transistor rises to a high level due to the charging of the first capacitor, the third MOS transistor is turned on, pulling down the control terminal of the switching element, turning off the switching element, and further controlling the disconnection of the standby power supply from the system power supply output terminal. Thus, after a preset delay when the main power supply starts supplying power, the standby power supply stops supplying power.

6. An electronic device, characterized in that, It includes the main and standby power supply switching circuit according to any one of claims 1-5.

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