CN108683248B - Power supply switching circuit and switching method and power supply equipment - Google Patents

Power supply switching circuit and switching method and power supply equipment Download PDF

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Publication number
CN108683248B
CN108683248B CN201810522366.3A CN201810522366A CN108683248B CN 108683248 B CN108683248 B CN 108683248B CN 201810522366 A CN201810522366 A CN 201810522366A CN 108683248 B CN108683248 B CN 108683248B
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Prior art keywords
power supply
backup battery
resistor
switch unit
external power
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CN201810522366.3A
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CN108683248A (en
Inventor
刘均
王伟杰
白洋先
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Shenzhen Launch Technology Co Ltd
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Shenzhen Launch Technology Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
    • H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
    • H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/18—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for batteries; for accumulators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • H02J7/0031—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using battery or load disconnect circuits
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
    • H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
    • H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
    • H02J9/061—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems for DC powered loads
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • H02J7/00306—Overdischarge protection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
    • H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
    • H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
    • H02J9/068—Electronic means for switching from one power supply to another power supply, e.g. to avoid parallel connection

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Stand-By Power Supply Arrangements (AREA)

Abstract

The disclosure relates to the field of electronic circuits, and provides a power supply switching circuit and a switching method. This power supply switching circuit includes: the external power supply monitoring module is connected with an external power supply and used for monitoring the connection or disconnection of the external power supply; the backup battery monitoring module is connected with the backup battery and used for monitoring the voltage of the backup battery; and the switch module is respectively connected with the external power supply monitoring module and the backup battery monitoring module and is used for switching on or switching off according to the monitoring result of the external power supply monitoring module and/or the backup battery monitoring module so as to control the power supply and the power failure of the backup battery. The power supply switching circuit in the disclosure ensures the stability of the backup battery when switching with the external power supply, prevents the backup battery from being over-discharged, and simultaneously avoids the condition that the product is electrified when producing and storing the product.

Description

Power supply switching circuit and switching method and power supply equipment
Technical Field
The present disclosure relates to the field of electronic circuits, and in particular, to a power supply switching circuit, a power supply switching method, and a power supply device including the power supply switching circuit.
Background
In communication electronics and personal electronics, many products require the use of a battery backup to supply power. After an external power supply is turned off, the electronic products such as a general communication master control single board, a PC mainboard and a personal palm electronic product need to be switched to a backup battery to protect data in the products from power loss, so that the data cannot be lost, and the data can still be used when the electronic products are turned on again. For such products, a battery backup is therefore required to be able to power the load for a long time.
In the prior art, there are two schemes for switching between a backup battery and an external power supply: the first is to use a dedicated chip; the second is to use a field effect transistor for switching. However, the first solution is expensive to implement, and the second solution, although the switching function is simple, cannot guarantee the normal function of the circuit in some application scenarios, and cannot protect the discharge voltage of the backup battery.
In view of the above, there is a need in the art to develop a new power supply switching circuit and a switching method.
It is to be noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.
Disclosure of Invention
The purpose of the present disclosure is to provide a power supply switching circuit, a power supply switching method, and a power supply device, so as to ensure reliability of switching between a backup battery and an external power supply at least to a certain extent, avoid electrification during production and storage of products, monitor voltage of the backup battery, and prevent over-discharge of the backup battery.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows, or in part will be obvious from the description, or may be learned by practice of the disclosure.
According to a first aspect of the present disclosure, there is provided a power supply switching circuit, including:
the external power supply monitoring module is connected with an external power supply and used for monitoring the connection or disconnection of the external power supply;
the backup battery monitoring module is connected with the backup battery and used for monitoring the voltage of the backup battery;
and the switch module is respectively connected with the external power supply monitoring module and the backup battery monitoring module and is used for switching on or switching off according to the monitoring result of the external power supply monitoring module and/or the backup battery monitoring module so as to control the power supply and the power failure of the backup battery.
In an exemplary embodiment of the present disclosure, the power supply switching circuit further includes:
and the micro control module is connected with the backup battery monitoring module and used for controlling the power supply and the power failure of the backup battery when the backup battery supplies power independently.
In an exemplary embodiment of the present disclosure, the external power detection module includes a first resistor, a second resistor, a third resistor, and a fourth resistor, the first resistor is connected in parallel with the second resistor, the third resistor is connected in series with the fourth resistor, first ends of the first resistor and the second resistor are connected to the external power source, a second end of the first resistor, a second end of the second resistor and a first end of the third resistor are connected, and a second end of the fourth resistor is grounded.
In an exemplary embodiment of the present disclosure, the backup battery monitoring module includes a regulated power supply, a fifth resistor, and a sixth resistor, a first end of the fifth resistor is connected to a load, a second end of the fifth resistor is connected to a first end of the sixth resistor and a first pin of the regulated power supply, and a second end of the sixth resistor and a second pin of the regulated power supply are grounded.
In an exemplary embodiment of the present disclosure, the switch module includes a first switch unit and a second switch unit, the external power monitoring module controls on or off of the first switch unit, and the backup battery monitoring module controls on or off of the second switch unit.
In an exemplary embodiment of the present disclosure, the first switch unit and the second switch unit are metal oxide semiconductor field effect transistors, a control terminal of the first switch unit is connected to a first terminal of the third resistor, the first terminal is connected to a load, and a second terminal is connected to a second terminal of the second switch unit; and the control end of the second switch unit is connected with a third pin of the voltage-stabilized power supply through a seventh resistor, and the first end of the second switch unit is connected with the backup battery.
In an exemplary embodiment of the present disclosure, the body diode in the first switching unit is connected in parallel with a schottky diode.
In an exemplary embodiment of the present disclosure, when the external power detection module detects that the external power is connected, the first switch unit in the switch module is turned off, the second switch unit is turned on, and the external power supplies power to a load;
when the external power supply detection module detects that the external power supply is disconnected, a first switch unit and a second switch unit in the switch module are both switched on, and the backup battery supplies power to a load;
when the backup battery monitoring module monitors that the voltage of the backup battery is lower than a preset value, a second switch unit of the switch module is cut off to cut off the power supply of the backup battery;
when the product is assembled, the first switch unit and the second switch unit in the switch module are both cut off, and no electric energy is input into the load.
According to a second aspect of the present disclosure, a power supply switching method is provided, which is applied to the power supply switching circuit, and includes:
when the external power supply is connected, the first switch unit in the switch module is switched off, the second switch unit is switched on, and the external power supply supplies power to the load;
when the external power supply is disconnected, the first switch unit and the second switch unit are both switched on, and the backup battery supplies power to the load.
According to a third aspect of the present disclosure, there is provided a power supply device including the power supply switching circuit described above.
According to the technical scheme, the power supply switching circuit, the power supply switching method and the power supply device in the exemplary embodiment of the disclosure have at least the following advantages and positive effects:
the power supply switching circuit comprises an external power supply monitoring module, a backup battery monitoring module and a switch module, wherein the external power supply monitoring module is used for monitoring the connection or disconnection of an external power supply; the backup battery monitoring module monitors the voltage of the backup battery; and the switch module is switched on or switched off according to the monitoring result of the external power supply monitoring module and/or the backup battery monitoring module so as to control the power supply and the power failure of the backup battery. By the power supply switching circuit, on one hand, the switching between the backup battery and the external power supply can be carried out in time, and the stability of the backup battery and the external power supply during switching is ensured; on the other hand, the power supply and the power off of the backup battery are controlled through the on/off of the switch module according to the monitoring result of the external power supply monitoring module and/or the backup battery monitoring module, so that the over-discharge of the backup battery can be prevented, and the service life of the backup battery is prolonged; in addition, only when an external power supply is connected, the backup battery can be activated to supply power, so that the risk of electrification during production and storage of products is avoided.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure. It is to be understood that the drawings in the following description are merely exemplary of the disclosure, and that other drawings may be derived from those drawings by one of ordinary skill in the art without the exercise of inventive faculty.
Fig. 1 shows a schematic diagram of a power supply switching circuit in the related art;
fig. 2 shows a schematic structural diagram of a power supply switching circuit in an exemplary embodiment of the present disclosure;
FIG. 3 shows a schematic diagram of a power supply switching circuit in an exemplary embodiment of the present disclosure;
FIG. 4 shows a schematic structural diagram of an external power monitoring module in an exemplary embodiment of the present disclosure;
FIG. 5 shows a schematic diagram of a backup battery monitoring module in an exemplary embodiment of the present disclosure;
FIG. 6 shows an equivalent circuit diagram of a regulated power supply in an exemplary embodiment of the present disclosure;
FIG. 7 shows a schematic structural diagram of a switch module in an exemplary embodiment of the disclosure;
FIG. 8 shows a schematic diagram of a power supply switching circuit in an exemplary embodiment of the present disclosure;
FIG. 9 shows a flow chart of a power supply switching method in an exemplary embodiment of the present disclosure;
fig. 10 shows a schematic structural diagram of a power supply device in an exemplary embodiment of the present disclosure.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the subject matter of the present disclosure can be practiced without one or more of the specific details, or with other methods, components, devices, steps, and the like. In other instances, well-known technical solutions have not been shown or described in detail to avoid obscuring aspects of the present disclosure.
The terms "a," "an," "the," and "said" are used in this specification to denote the presence of one or more elements/components/parts/etc.; the terms "comprising" and "having" are intended to be inclusive and mean that there may be additional elements/components/etc. other than the listed elements/components/etc.; the terms "first" and "second", etc. are used merely as labels, and are not limiting on the number of their objects.
Further, "connected," as used in this disclosure, may include two or more elements being in direct physical or electrical contact/coupling with each other, or being in indirect physical or electrical contact/coupling with each other. Also, the drawings are merely schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus their repetitive description will be omitted. Some of the block diagrams shown in the figures are functional entities and do not necessarily correspond to physically or logically separate entities.
In the related art in this field, a device with a backup battery requires a switching circuit to be turned on quickly when an external power supply is turned off, and the backup battery supplies power to a load; when an external power supply is connected, the switching circuit is required to be opened in a delayed mode, switching is performed after the internal DC-DC conversion circuit works normally, the external power supply supplies power to a load, otherwise, when the external power supply is connected, the power supply is switched immediately due to the fact that the DC-DC conversion circuit does not work normally, voltage drops are caused, and therefore the system is restarted.
Fig. 1 shows a power supply switching circuit in the related art, which includes an external power supply VINBackup battery VBATThe load is 4V2, the first switch unit Q40, the second switch unit Q41 and the resistors R1 and R2. The resistance value of the resistor R1 can be 200K, and the resistance value of the resistor R2 can be 300K; a first terminal of the resistor R1 and an external power source VINA second terminal of the resistor R2, a first terminal of the first switch unit Q40 and a control terminal of the second switch unit Q41 are connected; a first terminal of the first switching unit Q40 is connected with the load 4V2, and a second terminal is connected with a second terminal of the second switching unit Q41; the first terminal of the second switching unit Q41 and the backup battery VBATConnecting; the second terminal of resistor R2 is connected to ground.
However, the switching circuit has the following problems when the power supply is switched: (1) external power supply VINWhen disconnected, due to the external power supply VINThe capacitor in the battery can cause the switching to slow and backup the battery VBATThe switch-on cannot be rapidly switched, and power is supplied to a load 4V 2; (2) external power supply VINWhen the DC-DC conversion circuit is not normally operated, the voltage fluctuation of the load 4V2 may be caused, and even the system reset restart may be caused; (3) when the switching circuit is produced and stored, because the external power supply V is not availableINThe first switch unit Q40 and the second switch unit Q41 are always turned on at the input, so that the defects of charged production and storage exist, and the first switch unit Q40 and the second switch unit Q41 do not have an external power supply VINThe standby battery is always on during input, so that the standby battery is always discharged until the electric quantity of the standby battery is consumed, and the service life of the standby battery is seriously influenced.
In view of the related artIn order to solve the existing problems, the present disclosure firstly proposes a power supply switching circuit, fig. 2 shows a schematic diagram of the power supply switching circuit in the present disclosure, and as shown in fig. 2, the power supply switching circuit 200 includes an external power supply monitoring module 201, a backup battery monitoring module 202 and a switch module 203, where the external power supply monitoring module 201, the external power supply V and the external power supply V are connected to each otherINConnection for monitoring an external power supply VINAccess or disconnection of; backup battery monitoring module 202, and backup battery VBATConnection for monitoring the backup battery VBATVoltage of (d); the switch module 203 is respectively connected to the external power monitoring module 201 and the backup battery monitoring module 202, and is configured to turn on or off according to the monitoring result of the external power monitoring module 201 and/or the backup battery monitoring module 202 to control the backup battery VBATPower supply and power off; when the external power monitoring module 201 monitors the external power access, the switch module 203 is turned off to turn off the backup battery VBATTo an external power source VINSupplying power to a load through a DC-DC conversion circuit; when the external power monitoring module 201 monitors the external power VINWhen the battery is disconnected, the switch module 203 is turned on to make the backup battery VBATSupplying power to a load; when the backup battery monitoring module 202 monitors the backup battery VBATWhen the voltage is lower than a preset value, the switch module 203 is turned off to turn off the backup battery VBATFor supplying power to load and preventing backup battery VBATAnd (5) over-discharging.
The power supply switching circuit in the disclosure controls the power supply and the power failure of the backup battery by switching on or off the switch module according to the monitoring result of the external power supply monitoring module and/or the backup battery monitoring module, on one hand, the power supply switching circuit can switch between the backup battery and the external power supply in time, and the stability of the backup battery and the external power supply during switching is ensured; on the other hand, the over-discharge of the backup battery can be prevented, and the service life of the backup battery is prolonged.
In an exemplary embodiment of the disclosure, fig. 3 shows another schematic structural diagram of the power supply switching circuit 200, and as shown in fig. 3, the power supply switching circuit 200 further includes a micro-control module 204 connected to the backup battery monitoring module 202 for monitoring the backup battery VBATWhen the power is supplied independently, the backup battery V is automatically controlledBATPower supply and power off.
In an exemplary embodiment of the disclosure, fig. 4 shows a schematic structural diagram of the external power monitoring module 201, and as shown in fig. 4, the external power monitoring module 201 includes a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4, wherein the first resistor R1 and the second resistor R2 are connected in parallel, and a first end of the first resistor R1 and a first end of the second resistor R2 are connected to the external power VINA second end of the third resistor R3 is connected with the first end of the third resistor R3; the second end of the third resistor R3 is connected with the first end of the fourth resistor R4, and the third resistor R3 is connected with the fourth resistor R4 in series; the second terminal of the fourth resistor R4 is connected to ground.
In an exemplary embodiment of the disclosure, fig. 5 shows a schematic structural diagram of the backup battery monitoring module 202, and as shown in fig. 5, the backup battery monitoring module 202 includes a regulated power supply, a fifth resistor R5 and a sixth resistor R6, a first end of the fifth resistor R5 is connected to the load 4V2, and a second end of the fifth resistor R6 is connected to a first end of the sixth resistor R6 and the first pin 1 of the regulated power supply; a second end of the sixth resistor R6 is grounded; the second pin 2 of the voltage-stabilized power supply is grounded, and the third pin 3 is connected with the second ends of the seventh resistor R7 and the eighth resistor R8; a first end of the eighth resistor R8 is connected to the load 4V 2.
In an exemplary embodiment of the present disclosure, the regulated power supply may be a controllable precision regulated power supply, and may be a regulated power supply with model numbers CJ431, TJ431, TL431, and the like, which is not specifically limited by the present disclosure. Taking CJ431 voltage regulator as an example, fig. 6 shows an equivalent circuit diagram of a voltage regulator, as shown in fig. 6, the voltage regulator includes a comparator, a transistor and a diode, a first pin 1 is a REF pin of the comparator, a second pin 2 is an anode, and a third pin 3 is a cathode. The voltage signal is input to the comparator through the REF pin, the comparison voltage signal is input to the comparator through a negative pin adjacent to the REF pin, and a corresponding signal is output through the operation of the comparator so as to drive the triode and the diode to work. For CJ431 regulated power supply, when the REF pin voltage is higher than 2.5V, current will flow between the cathode and the anode. Meanwhile, in order to ensure the normal operation of the voltage-stabilized power supply, the cathode requires a minimum current of 1mA to flow in.
In an exemplary embodiment of the present disclosure, fig. 7 shows a schematic structural diagram of a switch module, and as shown in fig. 7, the switch module 203 includes a first switch unit 203a and a second switch unit 203b, where the first switch unit 203a is close to a load 4V2, and is controlled to be turned on or off by the external power monitoring module 201; the second switch unit 203b is close to the backup battery VBATThe backup battery monitoring module 202 controls the battery to be turned on or off, for example, when the backup battery monitoring module 202 monitors that the battery voltage is lower than 3.3V, the second switch unit 203b is turned off, and the power supply of the backup battery is turned off. Meanwhile, the micro-control module 204 autonomously controls the backup battery V according to the monitoring result of the backup battery monitoring module 202BATPower supply and power off.
In an exemplary embodiment of the present disclosure, fig. 8 shows a schematic structural diagram of a power supply switching circuit, and as shown in fig. 8, the first switching unit 203a and the second switching unit 203b may be metal oxide semiconductor field effect transistors, wherein a control terminal of the first switching unit 203a is connected to a first terminal of a third resistor R3, the first terminal is connected to a load 4V2, and the second terminal is connected to a second terminal of the second switching unit 203 b; the control terminal of the second switch unit 203b is connected to the first terminal of the seventh resistor R7, and the first terminal is connected to the backup battery VBATAnd (4) connecting. Further, the first and second switching units 203a and 203b may be P-type MOSFETs.
Further, as shown in fig. 8, a diode D is connected in parallel to both ends of the body diode of the first switching unit 203a, and the diode D may be a general diode, a schottky diode, or the like, and is preferably a schottky diode because the schottky diode has advantages of high switching frequency and low forward voltage drop. The diode D is connected in parallel with the body diode in the first switch unit 203a, and can reduce the forward conduction voltage drop of the body diode, for example, the forward voltage drop of the body diode can reach 1V when the current is large, and the maximum voltage drop of the diode D is 0.5V; and the diode D may act as a shunt when the load 4V2 requires a large current, reducing the risk of heating of the first switching unit 203 a.
In the exemplary embodiments of the present disclosureAs shown in fig. 8, the battery _ CTRL port is a general programming input/output interface of the micro control module 204, and is connected to the switch SW1 through a resistor, so as to control the micro control module 204 to backup the battery VBATActive turn-off of backup battery V during independent power supplyBATPower supply of (1); the ADC _ BAT _ IN port is an analog-to-digital conversion interface connected to the ADC input of the MCU 204 for detecting the backup battery VBATVoltage (only when the external power supply V is present)INAccessing or backing up batteries VBATPower is supplied to the load alone, and there is a voltage when the second switching unit 203b is turned on), and it can be used to detect the backup battery V at the same timeBATWhether it is normal or not. For autonomous shutdown of the backup battery V by the micro control module 204BATThe principle of power supply specifically is as follows: when the battery V is backed upBATWhen the power is supplied separately, the micro control module 204 inputs a low level signal to the power supply switching circuit 200 through the BATTERY _ CTRL port, the switch SW1 is closed, and under the action of the low level signal, the voltage of the first pin 1 of the backup voltage monitoring module 202 is lower than 2.5V, and no current flows between the second pin 2 and the third pin 3, so that the level of the control terminal of the second switch unit 203b is pulled high, and the second switch unit 203b is cut off, and the backup BATTERY V is turned offBATTo supply power.
Further, a signal line connected to the micro control module 204 may be provided between the third resistor R3 and the fourth resistor R4 for determining the external power source V according to a voltage value between the third resistor R3 and the fourth resistor R4INWhether to access. When the external power supply V is turned onINAt this time, the voltage at the point P is increased due to the voltage division of the third resistor R3 and the fourth resistor R4, and the micro control module 204 can determine the external POWER source V by detecting the voltage increase through the signal line port POWER _ ININAccessing; when the external power supply V is turned offINIn the meantime, the voltage at the point P drops until it remains unchanged, and the microcontroller 204 can determine the external power supply V according to the voltage variation trendINAnd no access is performed.
In an exemplary embodiment of the present disclosure, a capacitor C is connected in parallel to two ends of the sixth resistor R6, and is used for protecting the voltage of the regulated power supply pin when the micro control module 204 is actively reset, and preventing the instability of the second switching unit 203b caused by the instability of the micro control module 204, so as to further improve the stability of the power supply switching circuit.
In an exemplary embodiment of the disclosure, the power supply switching circuit 200 may further include an interference filtering module to further increase the backup battery V in the power supply switching circuitBATAnd an external power supply VINStability at handover.
In an exemplary embodiment of the present disclosure, a power supply switching method is also provided, and the switching method is applied to a power supply switching circuit in the present disclosure. Fig. 9 shows a flowchart of a power supply switching method in the present disclosure, which is as follows:
s1: when an external power supply is connected, the first switch unit in the switch module is switched off, the second switch unit is switched on, and the external power supply supplies power to the load;
s2: when the external power supply is disconnected, the first switch unit and the second switch unit in the switch module are both switched on, and the backup battery supplies power to the load.
Next, the operation principle and the switching method of the power supply switching circuit will be described in detail according to the schematic structural diagram of the power supply switching circuit shown in fig. 8.
When assembling and storing the product, the external power supply VINAnd when the load is not connected, the load 4V2 has no voltage input. Meanwhile, the stabilized voltage power supply is in a non-operating state due to no voltage input, so that the voltage of the control end of the second switch unit 203b connected with the stabilized voltage power supply cannot be changed, the first switch unit 203a and the second switch unit 203b are both cut off, no current flows through the circuit, and the risk of live operation cannot occur during assembly and storage of products.
When the external power supply VINWhen the first access is made, the backup battery V is usedBATAnd no power supply is provided, and the circuit is cold started. External power supply VINWhen the voltage regulator is connected, the DC-DC conversion circuit between the voltage regulator and the load 4V2 starts to work, when the working voltage of the load 4V2 is normal, at least 2mA of current flows into the third pin 3 of the voltage regulator, and the voltage regulator works normally. Due to the fifth resistor R5 and the sixth resistorThe voltage division of the resistor R6 at the first pin 1 of the regulated power supply is greater than 2.5V, a current flows between the second pin 2 and the third pin 3 of the regulated power supply, and the potential of the control terminal of the second switching unit 203b is pulled low, so that the second switching unit 203b is turned on. At the same time, an external power supply VINIn turn, since the first resistor R1, the second resistor R2, the third resistor R3 and the fourth resistor R4 divide the voltage, the control terminal of the first switch unit 203a is higher than the source potential, and therefore the first switch unit 203a is turned off. In addition, the back-up battery V after full chargingBATIs 4.2V, the voltage difference with the load 4V2 is small, the body diode and the diode D in the first switching unit 203a are not turned on, and thus the first switching unit 203a is completely turned off, and only the external power source V is turned offINPower is supplied to the load 4V 2.
When the external power supply VINWhen disconnected, the external power supply VINDue to the presence of internal capacitance, will slowly drop, causing a voltage drop across the DC-DC converter circuit to the load 4V 2. When the voltage of the load 4V2 drops to 3.9V, the diode D is conducted, and the backup battery VBATThe load 4V2 will be supplied through the diode D or the body diode of the first switching unit 203a, ensuring that the voltage at the load end will not drop further. Since the voltage of the load 4V2 does not drop below 3.3V, the second switching unit 203b is always on. When the external power supply VINWhen the voltage of the first switching unit 203a falls to the turn-on threshold of the first switching unit (for a 24V power supply system, when the external power supply V is turned onINIs lower than 9.3V, the first switching unit 203a is turned on), the first switching unit 203a is turned on, the body diode and the diode D are disabled, and the backup battery VBATThe load 4V2 is supplied with power alone, and the voltage of the load 4V2 rises to about the backup battery VBATThe voltage of (c). Since the voltage source BAT _4V2 is present at the second switch unit 203b near the battery backup end to provide voltage for the second switch unit 203b, the second switch unit 203b is always in the on state, and thus when controlling the on or off of the switch module 203, only the first switch unit 203a needs to be controlled to switch between the on state and the off state.
When in the backup battery VBATWhen in power supply, an external power supply V is connectedINMeanwhile, the level of the control terminal of the first switching unit 203a is pulled high, and when the turn-off threshold is reached, the first switching unit 203a is turned off. At this time, the DC-DC conversion circuit may not be operated normally, and when the voltage of the load 4V2 drops to about 3.9V, the backup battery VBATThe load 4V2 continues to be supplied with power through the diode D or the body diode until the output of the DC-DC conversion circuit is normal. When the output of the DC-DC conversion circuit is normal, the voltage of the load 4V2 and the backup battery VBATThe diode D and the body diode are not turned on, the first switching unit 203a is completely turned off, and the external power supply V is turned onINPower is supplied to the load 4V 2.
When the battery V is backed upBATWhen the voltage is lower than 3.3V, the voltage of the first pin 1 of the voltage-stabilized power supply is lower than 2.5V, the second pin 2 and the third pin 3 are cut off, and no current flows through due to the voltage division of the fifth resistor R5 and the sixth resistor R6; the control terminal level of the second switching unit 203b gradually approaches the level of the source, so that the second switching unit 203b is turned off. Without external power supply V at the same timeINWhen power is supplied, the voltage of the load 4V2 drops to 0, and the first switching unit 203a is also turned off until the backup battery V is completely turned offBATTo supply power. This prevents the backup battery from over-discharging and protects the load 4V2 from short-circuiting.
The power supply switching circuit disclosed by the invention has the advantages that the stability of the system during switching between the backup battery and the external power supply is ensured by adding fewer low-cost components, the added components are all universal components in the field, the components are compatible with the same type of products produced by different manufacturers, and even if the production of the materials is stopped, only the material list of the products needs to be adaptively modified; meanwhile, the voltage monitoring function of the backup battery is considered, and when the voltage of the backup battery is lower than a protection threshold value, the power supply of the backup battery can be automatically cut off, so that the service life of the backup battery is prolonged; and this disclosure is not connecting external power supply, when inserting the backup battery alone, the backup battery can not be automatic for the load power supply, only inserts external power supply when disconnection again, just can activate the power supply of backup battery to electrified risk when having avoided product equipment and storage.
In an exemplary embodiment of the present disclosure, a power supply device is further provided, fig. 10 shows a schematic structural diagram of the power supply device, and as shown in fig. 10, a power supply device 1000 includes a power supply switching circuit 1001, where the power supply switching circuit 1001 is the power supply switching circuit in the present disclosure. The power supply device 1000 may be a vehicle-mounted power supply device, or may be other power supply devices for supplying power to equipment, such as a power supply device for supplying power to an automobile diagnostic equipment, which is not specifically limited in this disclosure.
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.
It will be understood that the present disclosure is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is to be limited only by the terms of the appended claims.

Claims (6)

1. A power supply switching circuit, comprising:
the external power supply detection module comprises a first resistor, a second resistor, a third resistor and a fourth resistor, wherein the first resistor is connected with the second resistor in parallel, the third resistor is connected with the fourth resistor in series, first ends of the first resistor and the second resistor are connected with the external power supply, second ends of the first resistor and the second resistor are connected with a first end of the third resistor, and a second end of the fourth resistor is grounded;
the backup battery monitoring module is connected with a backup battery and used for monitoring the voltage of the backup battery, wherein the backup battery monitoring module comprises a voltage-stabilizing power supply, a fifth resistor and a sixth resistor, the first end of the fifth resistor is connected with a load, the second end of the fifth resistor is connected with the first end of the sixth resistor and the first pin of the voltage-stabilizing power supply, and the second end of the sixth resistor and the second pin of the voltage-stabilizing power supply are grounded;
the switch module consists of a first switch unit, a second switch unit and a Schottky diode connected with a body diode in the first switch unit in parallel, wherein the control end of the first switch unit is connected with the external power supply monitoring module, the first end of the first switch unit is connected with a load, the control end of the second switch unit is connected with the backup battery monitoring module, the first end of the second switch unit is connected with the backup battery, and the second end of the second switch unit is connected with the second end of the first switch unit and is used for being switched on or switched off according to the monitoring result of the external power supply monitoring module and/or the backup battery monitoring module so as to control the power supply and the power failure of the backup battery;
and the micro control module is connected with the backup battery monitoring module and used for controlling the power supply and the power off of the backup battery when the backup battery supplies power independently, wherein the micro control module at least comprises a first port and a second port, the first port is connected with a first pin of a voltage-stabilized power supply in the backup battery monitoring module, and the second port is connected with a second end of the second switch unit through a voltage-dividing circuit.
2. The power supply switching circuit according to claim 1, wherein the external power monitoring module controls the first switching unit to be turned on or off, and the backup battery monitoring module controls the second switching unit to be turned on or off.
3. The power supply switching circuit according to claim 2, wherein the first switching unit and the second switching unit are metal oxide semiconductor field effect transistors, a control terminal of the first switching unit is connected to a first terminal of the third resistor, the first terminal is connected to a load, and a second terminal is connected to a second terminal of the second switching unit; and the control end of the second switch unit is connected with a third pin of the voltage-stabilized power supply through a seventh resistor, and the first end of the second switch unit is connected with the backup battery.
4. The power supply switching circuit according to claim 1,
when the external power supply detection module detects that the external power supply is connected, a first switch unit in the switch module is switched off, a second switch unit is switched on, and the external power supply supplies power to a load;
when the external power supply detection module detects that the external power supply is disconnected, a first switch unit and a second switch unit in the switch module are both switched on, and the backup battery supplies power to a load;
when the backup battery monitoring module monitors that the voltage of the backup battery is lower than a preset value, a second switch unit of the switch module is cut off to cut off the power supply of the backup battery;
when the product is assembled, the first switch unit and the second switch unit in the switch module are both cut off, and no electric energy is input into the load.
5. A power supply switching method applied to the power supply switching circuit according to any one of claims 1 to 4, comprising:
when the external power supply is connected, the first switch unit in the switch module is switched off, the second switch unit is switched on, and the external power supply supplies power to the load;
when the external power supply is disconnected, the first switch unit and the second switch unit are both switched on, and the backup battery supplies power to the load.
6. A power supply device comprising the power supply switching circuit according to any one of claims 1 to 4.
CN201810522366.3A 2018-05-28 2018-05-28 Power supply switching circuit and switching method and power supply equipment Active CN108683248B (en)

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CN109638928A (en) * 2019-01-24 2019-04-16 惠州市德赛工业研究院有限公司 A kind of power supply management circuit, method
CN110502092B (en) * 2019-07-17 2023-11-24 闻泰科技(无锡)有限公司 Power supply circuit and electronic equipment
CN117301955B (en) * 2023-12-01 2024-04-12 宁德时代新能源科技股份有限公司 Battery pack switching circuit, power battery system and battery pack switching method

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