Power switching circuit

Abstract

The utility model relates to the technical field of power supply switching, in particular to a power supply switching circuit, which comprises a metal oxide semiconductor (MOS) tube Q1, a triode Q2, a MOS tube Q3, a diode D1 and a diode D2, a grid electrode of the MOS tube Q3 is electrically connected with an external power supply, a drain electrode of the MOS tube Q3 is electrically connected with a base electrode of the triode Q2, an emitting electrode of the triode Q2 is respectively and electrically connected with the grid electrode of the MOS tube Q1, a source electrode of the MOS tube Q1 and a standby power supply, and the diode D1 is electrically connected with the diode D2. The drain electrode of the MOS tube Q1 is electrically connected with the anode of the diode D1, the cathode of the diode D1 is electrically connected with the cathode of the diode D2 and external equipment to be powered respectively, and the anode of the diode D2 is electrically connected with the grid electrode of the MOS tube Q3, so that when the voltage of the external power supply is input, the standby power supply does not output, and the external power supply supplies power to the equipment to be powered; and when no external power supply voltage is input, the standby power supply is quickly started to supply power to the to-be-powered equipment, so that the purpose of seamless switching is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply switching, and particularly relates to a power supply switching circuit. Background Art

[0002] At present, various instruments, devices, electronic devices, etc. are all inseparable from power supply. Some devices such as video monitoring and Internet of Things devices are powered by multiple power supplies. Generally, long-term power supply is provided by an external power supply. However, when an accident occurs to the external power supply, it is necessary to quickly switch to the backup power supply to supply power to the device in order to keep the device working normally. In the prior art, generally, two diodes, a dedicated IC chip module, a relay, etc. are used to realize power supply switching. However, the above several methods have the following disadvantages:

[0003] 1. The method of using two diodes to realize power supply switching:

[0004] Since the voltage of the external power supply used is only about 3.8V, and the backup power supply can reach 4.2V when fully charged, the voltage of the backup power supply is higher than that of the external power supply. Then the device is powered by the backup power supply, which will continuously consume the battery power of the backup power supply, making the backup power supply in a state of charging and discharging at the same time. In this way, the backup power supply cannot play the role of backup, and long-term frequent charging and discharging will also reduce its own service life;

[0005] 2. The method of using a dedicated IC chip module to realize power supply switching:

[0006] The cost of the dedicated IC chip solution is relatively high;

[0007] 3. The method of using a relay to realize power supply switching:

[0008] When the relay is in the normal state, the coil needs to be constantly powered. When the coil is constantly powered, heat will be generated, affecting the reliability of the relay. Summary of the Utility Model

[0009] The technical problem to be solved by the utility model is to provide a power supply switching circuit that can quickly realize the switching of the backup power supply.

[0010] To solve the above technical problems, the technical solution adopted by the utility model is:

[0011] A power switching circuit includes MOS transistor Q1, triode Q2, MOS transistor Q3, diode D1 and diode D2. The gate of MOS transistor Q3 is electrically connected to an external power supply. The source of MOS transistor Q3 is grounded. The drain of MOS transistor Q3 is electrically connected to the base of triode Q2. The emitter of triode Q2 is respectively electrically connected to the gate of MOS transistor Q1, the source of MOS transistor Q1 and a backup power supply. The collector of triode Q2 is electrically connected to the gate of MOS transistor Q1. The drain of MOS transistor Q1 is electrically connected to the anode of diode D1. The cathode of diode D1 is respectively electrically connected to the cathode of diode D2 and an external device to be powered. The anode of diode D2 is electrically connected to the gate of MOS transistor Q3. The voltage value of the backup power supply is greater than that of the external power supply.

[0012] Further, it also includes resistor R2 and resistor R4. One end of resistor R2 is respectively electrically connected to the anode of diode D2 and the external power supply. The other end of resistor R2 is respectively electrically connected to one end of resistor R4 and the gate of MOS transistor Q3. The other end of resistor R4 is grounded.

[0013] Further, it also includes resistor R1 and resistor R3. One end of resistor R1 is electrically connected to the drain of MOS transistor Q3. The other end of resistor R1 is electrically connected to the base of triode Q2. One end of resistor R3 is respectively electrically connected to the collector of triode Q2 and the gate of MOS transistor Q1. The other end of resistor R3 is grounded.

[0014] Further, it also includes capacitor C2 and capacitor C3. One end of capacitor C2 is respectively electrically connected to the emitter of triode Q2, the source of MOS transistor Q1 and the backup power supply. The other end of capacitor C2 is respectively electrically connected to the gate of MOS transistor Q1, one end of capacitor C3, one end of resistor R3 and the collector of triode Q2. The other end of capacitor C3 is electrically connected to the other end of resistor R3 and the other end of capacitor C3 is grounded.

[0015] Further, it also includes capacitor C1. One end of capacitor C1 is respectively electrically connected to the drain of MOS transistor Q1 and the anode of diode D1. The other end of capacitor C1 is grounded.

[0016] The beneficial effects of the present utility model are as follows:

[0017] In this solution, by setting MOS transistor Q1, bipolar transistor Q2, MOS transistor Q3, diode D1 and diode D2, the gate of MOS transistor Q3 is electrically connected to an external power supply, the source of MOS transistor Q3 is grounded, the drain of MOS transistor Q3 is electrically connected to the base of bipolar transistor Q2, the emitter of bipolar transistor Q2 is respectively electrically connected to the gate of MOS transistor Q1, the source of MOS transistor Q1 and a backup power supply, the drain of MOS transistor Q1 is electrically connected to the anode of diode D1, the cathode of diode D1 is respectively electrically connected to the cathode of diode D2 and an external device to be powered, the anode of diode D2 is electrically connected to the gate of MOS transistor Q3, and the voltage value of the backup power supply is greater than that of the external power supply. In this way, when there is an input of external power supply voltage, the backup power supply does not output, and the external power supply powers the device to be powered; when there is no input of external power supply voltage (i.e., the external power supply is abnormal), the backup power supply quickly turns on to power the device to be powered, thus achieving the purpose of seamless switching; the power supply switching circuit designed in this solution can avoid the situation that the backup power supply is overcharged and discharged when the voltage of the backup power supply is higher than that of the external power supply, reducing its own service life, and will not generate heat, enabling the backup power supply to operate stably and reliably for a long time. Description of the Drawings

[0018] Figure 1 is the circuit schematic diagram of the power supply switching circuit of the present invention. Detailed Embodiments

[0019] To describe in detail the technical content, the achieved objectives and the effects of the present invention, the following is described in conjunction with the embodiments and with reference to the drawings.

[0020] Please refer to Figure 1 , the technical solution adopted by the present invention is as follows:

[0021] A power supply switching circuit includes MOS transistor Q1, bipolar transistor Q2, MOS transistor Q3, diode D1 and diode D2. The gate of MOS transistor Q3 is electrically connected to an external power supply, the source of MOS transistor Q3 is grounded, the drain of MOS transistor Q3 is electrically connected to the base of bipolar transistor Q2, the emitter of bipolar transistor Q2 is respectively electrically connected to the gate of MOS transistor Q1, the source of MOS transistor Q1 and a backup power supply, the collector of bipolar transistor Q2 is electrically connected to the gate of MOS transistor Q1, the drain of MOS transistor Q1 is electrically connected to the anode of diode D1, the cathode of diode D1 is respectively electrically connected to the cathode of diode D2 and an external device to be powered, the anode of diode D2 is electrically connected to the gate of MOS transistor Q3, and the voltage value of the backup power supply is greater than that of the external power supply.

[0022] As can be seen from the above description, the beneficial effects of the present invention are as follows:

[0023] In this solution, by setting MOS transistor Q1, triode Q2, MOS transistor Q3, diode D1 and diode D2, the gate of MOS transistor Q3 is electrically connected to an external power supply, the source of MOS transistor Q3 is grounded, the drain of MOS transistor Q3 is electrically connected to the base of triode Q2, the emitter of triode Q2 is respectively electrically connected to the gate of MOS transistor Q1, the source of MOS transistor Q1 and a backup power supply, the drain of MOS transistor Q1 is electrically connected to the anode of diode D1, the cathode of diode D1 is respectively electrically connected to the cathode of diode D2 and an external device to be powered, the anode of diode D2 is electrically connected to the gate of MOS transistor Q3, and the voltage value of the backup power supply is greater than that of the external power supply. In this way, when there is an external power supply voltage input, the backup power supply does not output, and the external power supply powers the device to be powered; when there is no external power supply voltage input (i.e., the external power supply is abnormal), the backup power supply quickly turns on to power the device to be powered, thus achieving the purpose of seamless switching; the power supply switching circuit designed in this solution can avoid the situation of excessive charging and discharging of the backup power supply when the voltage of the backup power supply is higher than that of the external power supply, which reduces its own lifespan, and does not generate heat, enabling the backup power supply to operate stably and reliably for a long time.

[0024] Further, it also includes resistor R2 and resistor R4. One end of resistor R2 is respectively electrically connected to the anode of diode D2 and the external power supply, the other end of resistor R2 is respectively electrically connected to one end of resistor R4 and the gate of MOS transistor Q3, and the other end of resistor R4 is grounded.

[0025] As can be seen from the above description, resistor R2 and resistor R4 serve as resistors for detecting the external power supply voltage, and at the same time, when the external power supply is abnormal, they can quickly discharge the excess voltage on the external power supply.

[0026] Further, it also includes resistor R1 and resistor R3. One end of resistor R1 is electrically connected to the drain of MOS transistor Q3, the other end of resistor R1 is electrically connected to the base of triode Q2, one end of resistor R3 is respectively electrically connected to the collector of triode Q2 and the gate of MOS transistor Q1, and the other end of resistor R3 is grounded.

[0027] As can be seen from the above description, resistor R1 and resistor R3 play a current-limiting role, protecting triode Q2 and MOS transistor Q3 respectively.

[0028] Further, it also includes capacitor C2 and capacitor C3. One end of capacitor C2 is respectively electrically connected to the emitter of triode Q2, the source of MOS transistor Q1 and the backup power supply, the other end of capacitor C2 is respectively electrically connected to the gate of MOS transistor Q1, one end of capacitor C3, one end of resistor R3 and the collector of triode Q2, and the other end of capacitor C3 is electrically connected to the other end of resistor R3 and the other end of capacitor C3 is grounded.

[0029] As can be seen from the above description, capacitors C2 and C3 can accelerate the turn-on speed of MOS transistor Q1.

[0030] Further, it further includes capacitor C1. One end of the capacitor C1 is electrically connected to the drain of the MOS transistor Q1 and the anode of the diode D1 respectively, and the other end of the capacitor C1 is grounded.

[0031] As can be seen from the above description, the capacitor C1 plays a role in energy storage.

[0032] Please refer to Figure 1 , Embodiment 1 of the present utility model is:

[0033] A power supply switching circuit includes a MOS transistor Q1, a triode Q2, a MOS transistor Q3, a diode D1 and a diode D2. The gate of the MOS transistor Q3 is electrically connected to an external power supply, the source of the MOS transistor Q3 is grounded, the drain of the MOS transistor Q3 is electrically connected to the base of the triode Q2, the emitter of the triode Q2 is electrically connected to the gate of the MOS transistor Q1, the source of the MOS transistor Q1 and a standby power supply respectively, the collector of the triode Q2 is electrically connected to the gate of the MOS transistor Q1, the drain of the MOS transistor Q1 is electrically connected to the anode of the diode D1, the cathode of the diode D1 is electrically connected to the cathode of the diode D2 and an external device to be powered respectively, the anode of the diode D2 is electrically connected to the gate of the MOS transistor Q3, and the voltage value of the standby power supply is greater than the voltage value of the external power supply.

[0034] It further includes a resistor R2 and a resistor R4. One end of the resistor R2 is electrically connected to the anode of the diode D2 and the external power supply respectively, the other end of the resistor R2 is electrically connected to one end of the resistor R4 and the gate of the MOS transistor Q3 respectively, and the other end of the resistor R4 is grounded.

[0035] It further includes a resistor R1 and a resistor R3. One end of the resistor R1 is electrically connected to the drain of the MOS transistor Q3, the other end of the resistor R1 is electrically connected to the base of the triode Q2, one end of the resistor R3 is electrically connected to the collector of the triode Q2 and the gate of the MOS transistor Q1 respectively, and the other end of the resistor R3 is grounded.

[0036] It further includes a capacitor C2 and a capacitor C3. One end of the capacitor C2 is electrically connected to the emitter of the triode Q2, the source of the MOS transistor Q1 and the standby power supply respectively, the other end of the capacitor C2 is electrically connected to the gate of the MOS transistor Q1, one end of the capacitor C3, one end of the resistor R3 and the collector of the triode Q2 respectively, and the other end of the capacitor C3 is electrically connected to the other end of the resistor R3 and the other end of the capacitor C3 is grounded.

[0037] It also includes a capacitor C1. One end of the capacitor C1 is electrically connected to the drain of the MOS transistor Q1 and the anode of the diode D1 respectively, and the other end of the capacitor C1 is grounded.

[0038] The working principle of the above power supply switching circuit is as follows:

[0039] When an external power supply voltage VCC_3V8 is input (at this time, the voltage value of the backup power supply is greater than that of the external power supply), the gate-source voltage Vgs of the MOS transistor Q3 reaches the threshold voltage, causing the MOS transistor Q3 to conduct, and then causing the triode Q2 to conduct. Then, the gate voltage of the MOS transistor Q1 is the voltage of the backup power supply. Therefore, the gate-source voltage Vgs of the MOS transistor Q1 does not reach the threshold voltage, causing the MOS transistor Q1 to cut off, and there is no voltage output at the Li_OUT port. The voltage at the VCC_3V8 port is output to the VCC terminal to supply power to the device to be powered.

[0040] When there is no external power supply voltage VCC_3V8 input (at this time, the external power supply is abnormal), the gate-source voltage Vgs of the MOS transistor Q3 does not reach the threshold voltage, causing the MOS transistor Q3 to cut off, and then causing the triode Q2 to cut off. Then, the gate voltage of the MOS transistor Q1 is close to 0V, and the gate-source voltage Vgs of the MOS transistor Q1 reaches the threshold voltage, causing the MOS transistor Q1 to conduct. There is a voltage output at the Li_OUT port, and the voltage at the Li_OUT port is output to the VCC terminal to supply power to the device to be powered, thus achieving the purpose of seamless switching.

[0041] In summary, a power supply switching circuit provided by the present utility model, by setting the MOS transistor Q1, the triode Q2, the MOS transistor Q3, the diode D1, and the diode D2, the gate of the MOS transistor Q3 is electrically connected to the external power supply, the source of the MOS transistor Q3 is grounded, the drain of the MOS transistor Q3 is electrically connected to the base of the triode Q2, the emitter of the triode Q2 is electrically connected to the gate of the MOS transistor Q1, the source of the MOS transistor Q1, and the backup power supply respectively, the drain of the MOS transistor Q1 is electrically connected to the anode of the diode D1, the cathode of the diode D1 is electrically connected to the cathode of the diode D2 and the external device to be powered respectively, the anode of the diode D2 is electrically connected to the gate of the MOS transistor Q3, and the voltage value of the backup power supply is greater than that of the external power supply. In this way, when an external power supply voltage is input, the backup power supply does not output, and the external power supply supplies power to the device to be powered; when there is no external power supply voltage input (i.e., the external power supply is abnormal), the backup power supply is quickly turned on to supply power to the device to be powered, thus achieving the purpose of seamless switching; the power supply switching circuit designed in this solution can avoid the situation that the backup power supply is overcharged and discharged when the voltage of the backup power supply is higher than that of the external power supply, reducing its own service life, and will not generate heat, enabling the backup power supply to operate stably and reliably for a long time.

[0042] The above are only embodiments of the present utility model, and thus do not limit the patent scope of the present utility model. Any equivalent transformation made by using the content of the specification and drawings of the present utility model, or directly or indirectly applied in related technical fields, shall similarly be included within the patent protection scope of the present utility model.

Claims

1. A power switching circuit, characterized in that, It includes MOS transistor Q1, triode Q2, MOS transistor Q3, diode D1 and diode D2. The gate of the MOS transistor Q3 is electrically connected to an external power supply. The source of the MOS transistor Q3 is grounded. The drain of the MOS transistor Q3 is electrically connected to the base of the triode Q2. The emitter of the triode Q2 is respectively electrically connected to the gate of the MOS transistor Q1, the source of the MOS transistor Q1 and a standby power supply. The collector of the triode Q2 is electrically connected to the gate of the MOS transistor Q1. The drain of the MOS transistor Q1 is electrically connected to the anode of the diode D1. The cathode of the diode D1 is respectively electrically connected to the cathode of the diode D2 and an external device to be powered. The anode of the diode D2 is electrically connected to the gate of the MOS transistor Q3. The voltage value of the standby power supply is greater than the voltage value of the external power supply.

2. The power supply switching circuit according to claim 1, wherein It further includes resistor R2 and resistor R4. One end of the resistor R2 is respectively electrically connected to the anode of the diode D2 and the external power supply. The other end of the resistor R2 is respectively electrically connected to one end of the resistor R4 and the gate of the MOS transistor Q3. The other end of the resistor R4 is grounded.

3. The power supply switching circuit according to claim 1, wherein It further includes resistor R1 and resistor R3. One end of the resistor R1 is electrically connected to the drain of the MOS transistor Q3. The other end of the resistor R1 is electrically connected to the base of the triode Q2. One end of the resistor R3 is respectively electrically connected to the collector of the triode Q2 and the gate of the MOS transistor Q1. The other end of the resistor R3 is grounded.

4. The power supply switching circuit according to claim 3, wherein It further includes capacitor C2 and capacitor C3. One end of the capacitor C2 is respectively electrically connected to the emitter of the triode Q2, the source of the MOS transistor Q1 and the standby power supply. The other end of the capacitor C2 is respectively electrically connected to the gate of the MOS transistor Q1, one end of the capacitor C3, one end of the resistor R3 and the collector of the triode Q2. The other end of the capacitor C3 is electrically connected to the other end of the resistor R3 and the other end of the capacitor C3 is grounded.

5. The power supply switching circuit according to claim 1, wherein It further includes capacitor C1. One end of the capacitor C1 is respectively electrically connected to the drain of the MOS transistor Q1 and the anode of the diode D1. The other end of the capacitor C1 is grounded.

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