Control circuit for preventing output voltage from being out of control and lithium battery charger

Abstract

The invention provides a control circuit for preventing output voltage from being out of control and a lithium battery charger, the control circuit comprises a constant voltage circuit, a switching circuit, power supply voltage and a driving signal pull-down circuit, the constant voltage circuit comprises a three-terminal voltage stabilizer, and the driving signal pull-down circuit comprises an NPN type triode Q2; under the driving of the power supply voltage, the switching circuit is in an open state; the constant voltage circuit calculates a constant output voltage according to the reference voltage of the three-terminal regulator and a set voltage division ratio; when the constant output voltage is within a set range, the driving signal pull-down circuit controls the NPN type triode Q2 not to be conducted; when the constant output voltage exceeds a set range, an NPN type triode Q2 is controlled to be switched on, so that the power supply voltage is pulled down to the ground, and after the switching circuit is not switched on, the constant output voltage is reduced to a set threshold value; a switching circuit and a driving signal pull-down circuit are added on the basis of a constant voltage circuit, when the constant output voltage is out of control, the constant output voltage is reduced to a set threshold value, and the safety of a product is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of chargers, and in particular to a control circuit and a lithium battery charger for preventing output voltage from being out of control. Background Art

[0002] Currently, constant voltage control circuits include a three-terminal voltage regulator, an optocoupler, an upper bias resistor, and a lower bias resistor. By adjusting the resistance values ​​of the upper and lower bias resistors, the voltage divider ratio is changed, thereby changing the output voltage. The lower bias resistor can be divided into one resistor or two resistors.

[0003] However, in the under-bias resistor, when any one of the resistors is short-circuited, the output voltage will be out of control, that is, the output voltage will exceed the set voltage by a large margin, resulting in poor product safety. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a control circuit and a lithium battery charger that prevents output voltage from getting out of control. By adding a switching circuit and a drive signal pull-down circuit on the basis of a constant voltage circuit, when the constant output voltage gets out of control, it drops to a set threshold, thereby improving product safety.

[0005] In a first aspect, an embodiment of the present invention provides a control circuit for preventing output voltage from being out of control, the control circuit comprising a constant voltage circuit, a switching circuit, a power supply voltage, and a drive signal pull-down circuit, wherein the constant voltage circuit comprises a three-terminal voltage regulator, and the drive signal pull-down circuit comprises an NPN transistor Q2;

[0006] The power supply voltage is connected to the switch circuit and the drive signal pull-down circuit respectively, the drive signal pull-down circuit is connected to the switch circuit, and the switch circuit is connected to the constant voltage circuit;

[0007] The switch circuit is configured to be in an open state under the drive of the power supply voltage;

[0008] The constant voltage circuit is used to calculate a constant output voltage according to the reference voltage of the three-terminal regulator and a set voltage division ratio;

[0009] The drive signal pull-down circuit is used to control the NPN transistor Q2 to be non-conductive when the constant output voltage is within a set range;

[0010] When the constant output voltage exceeds the set range, the NPN transistor Q2 is controlled to be turned on so that the supply voltage is pulled down to ground, and after the switch circuit is turned off, the constant output voltage is reduced to a set threshold.

[0011] Furthermore, the control circuit further includes a current limiting resistor R6, the switch circuit includes an NPN transistor Q1 and a resistor R7, and the drive signal pull-down circuit includes a first voltage detection resistor R8, a second voltage detection resistor R9 and a resistor R10;

[0012] One end of the first voltage detection resistor R8 is connected to the constant output voltage, and the other end of the first voltage detection resistor R8 is respectively connected to one end of the first voltage detection resistor R9, one end of the resistor R10, and the base of the NPN transistor Q2;

[0013] The other end of the second voltage detection resistor R9 is grounded, and the emitter of the NPN transistor Q2 is connected to the other end of the resistor R10 and then grounded.

[0014] Furthermore, one end of the current limiting resistor R6 is connected to the power supply voltage, and the other end of the current limiting resistor R6 is respectively connected to the collector of the NPN transistor Q2, one end of the resistor R7, and the base of the NPN transistor Q1. The collector of the NPN transistor Q1 is connected to the other end of the resistor R5 in the down-bias resistor, and the emitter of the NPN transistor Q1 is connected to the other end of the resistor R7 and then grounded.

[0015] Furthermore, the switching circuit is used to place the NPN transistor Q1 in the open state under the drive of the power supply voltage.

[0016] Furthermore, the drive signal pull-down circuit is configured to calculate a first voltage of the first voltage detection resistor R8 and a second voltage of the second voltage detection resistor R9 according to the constant output voltage and the set voltage divider ratio when the constant output voltage is within a set range; and drive the NPN transistor Q2 to be non-conductive according to the second voltage;

[0017] The first voltage is greater than the driving start voltage of the NPN transistor Q2, and the second voltage is less than the driving start voltage of the NPN transistor Q2.

[0018] Furthermore, the drive signal pull-down circuit is configured to calculate a third voltage of the first voltage detection resistor R8 and a fourth voltage of the second voltage detection resistor R9 according to the constant output voltage and the set voltage divider ratio when the constant output voltage exceeds the set range; and drive the NPN transistor Q2 to conduct according to the fourth voltage;

[0019] The fourth voltage is greater than the driving turn-on voltage of the NPN transistor Q2.

[0020] Furthermore, the constant voltage circuit also includes an upper bias resistor and a lower bias resistor; the three-terminal voltage regulator is connected to one end of the upper bias resistor and one end of the lower bias resistor respectively, and the other end of the upper bias resistor is connected to the constant output voltage.

[0021] Furthermore, the upper bias resistor includes a resistor R2 and a resistor R3, and the lower bias resistor includes a resistor R4 and a resistor R5;

[0022] The three-terminal voltage regulator is connected to one end of the resistor R3 and one end of the resistor R4 respectively, the other end of the resistor R3 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to the constant output voltage;

[0023] The other end of the resistor R4 is connected to one end of the resistor R5.

[0024] Furthermore, the constant voltage circuit is used to calculate the constant output voltage based on the reference voltage and the set voltage division ratio, using the voltage stabilization point of the three-terminal regulator as the reference voltage when the upper bias resistor and the lower bias resistor form the set voltage division ratio.

[0025] In a second aspect, an embodiment of the present invention provides a lithium battery charger, comprising the control circuit for preventing output voltage from being out of control as described above.

[0026] Embodiments of the present invention provide a control circuit and a lithium battery charger for preventing output voltage runaway. The control circuit includes a constant voltage circuit, a switching circuit, a power supply voltage, and a drive signal pull-down circuit. The constant voltage circuit includes a three-terminal voltage regulator, and the drive signal pull-down circuit includes an NPN transistor Q2. The power supply voltage is connected to the switching circuit and the drive signal pull-down circuit, respectively. The drive signal pull-down circuit is connected to the switching circuit, which is connected to the constant voltage circuit. Driven by the power supply voltage, the switching circuit is in an open state. The constant voltage circuit calculates a constant output voltage based on a reference voltage of the three-terminal voltage regulator and a set voltage divider ratio. When the constant output voltage is within a set range, the drive signal pull-down circuit controls the NPN transistor Q2 to be non-conductive. When the constant output voltage exceeds the set range, the NPN transistor Q2 is controlled to be conductive, so that the power supply voltage is pulled down to ground. After the switch circuit is non-conductive, the constant output voltage drops to a set threshold. By adding the switching circuit and the drive signal pull-down circuit to the constant voltage circuit, the constant output voltage drops to a set threshold when it loses control, thereby improving product safety.

[0027] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or understood by practicing the present invention. The purposes and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 A schematic diagram of a control circuit for preventing output voltage from running out of control provided in the first embodiment of the present invention;

[0031] Figure 2 A schematic diagram of another control circuit for preventing output voltage from running out of control provided by the first embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of the control circuit structure for preventing output voltage from losing control provided in the first embodiment of the present invention.

[0033] icon:

[0034] 1-Constant voltage circuit; 2-Switching circuit; 3-Power supply voltage; 4-Drive signal pull-down circuit. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0036] To facilitate understanding of this embodiment, the embodiment of the present invention is described in detail below.

[0037] Example 1:

[0038] Figure 1 This is a schematic diagram of a control circuit for preventing output voltage from running out of control provided in the first embodiment of the present invention.

[0039] Reference Figure 1 The control circuit includes a constant voltage circuit 1, a switch circuit 2, a power supply voltage 3, and a drive signal pull-down circuit 4, wherein, Figure 2, the constant voltage circuit 1 includes a three-terminal voltage regulator, and the driving signal pull-down circuit 4 includes an NPN transistor Q2;

[0040] The power supply voltage 3 is connected to the switch circuit 2 and the drive signal pull-down circuit 4 respectively, the drive signal pull-down circuit 4 is connected to the switch circuit 2, and the switch circuit 2 is connected to the constant voltage circuit 1;

[0041] The switch circuit 2 is configured to be in an open state under the drive of the power supply voltage 3;

[0042] The constant voltage circuit 1 is used to calculate a constant output voltage according to a reference voltage of the three-terminal voltage regulator and a set voltage division ratio;

[0043] The driving signal pull-down circuit 4 is used to control the NPN transistor Q2 to be non-conductive when the constant output voltage is within a set range;

[0044] When the constant output voltage exceeds the set range, the NPN transistor Q2 is controlled to conduct, pulling the supply voltage down to ground. After the switch circuit is turned off, the constant output voltage drops to the set threshold value. The set threshold value is the reference voltage of the three-terminal regulator.

[0045] Specifically, the existing constant voltage control circuit includes a three-terminal voltage regulator, an optocoupler, an upper bias resistor, and a lower bias resistor. By adjusting the resistance values ​​of the upper and lower bias resistors, the voltage divider ratio is changed, thereby changing the output voltage. The lower bias resistor can be divided into one resistor or two resistors. However, if any of the lower bias resistors is short-circuited, the output voltage will be out of control, that is, the output voltage will exceed the set voltage by a large margin, resulting in poor product safety.

[0046] In this application, the control circuit also includes a current limiting resistor R6, the switch circuit includes an NPN transistor Q1 and a resistor R7, the drive signal pull-down circuit includes a first voltage detection resistor R8, a second voltage detection resistor R9 and a resistor R10; the constant voltage circuit includes a three-terminal voltage regulator, an upper bias resistor and a lower bias resistor. Figure 3 The supply voltage drives the NPN transistor Q1 through the current limiting resistor R6 and keeps it on. Then the upper resistors R2 and R3 form a voltage divider with the lower resistors R4 and R5. The voltage point 2.495V of the three-terminal regulator U1 is used as the reference voltage of the lower resistor. The constant output voltage is calculated based on the reference voltage and the set voltage divider ratio. Figure 3 , the constant output voltage can be obtained by formula (1):

[0047] Vout=2.495V / (R4+R5)*(R2+R3+R4+R5) (1)

[0048] Among them, 2.495V is the reference voltage of the three-terminal regulator.

[0049] The present application adds a switching circuit and a drive signal pull-down circuit on the basis of a constant voltage circuit. The constant output voltage Vout is driven by the voltage division of the first voltage detection resistor R8 and the second voltage detection resistor R9. The voltage division ratio of the first voltage detection resistor R8 and the second voltage detection resistor R9 is calculated. When the constant output voltage Vout is within a set range, the NPN transistor Q2 is controlled to be non-conductive, and the voltage divided by the first voltage detection resistor R8 and the second voltage detection resistor R9 is lower than the drive start-up voltage of the pull-down NPN transistor Q2.

[0050] When the constant output voltage Vout exceeds the set range, the pull-down NPN transistor Q2 is driven into conduction by the voltage divided by the second voltage detection resistor R9, causing the supply voltage to be directly pulled down to ground. As a result, the NPN transistor Q1 loses its drive signal and turns off. The voltage divider circuit between the upper and lower bias resistors is disconnected, and the constant output voltage drops to the set threshold, thereby improving product safety. The supply voltage can be, but is not limited to, 5V and can be set as needed.

[0051] Furthermore, one end of the current limiting resistor R6 is connected to the power supply voltage, and the other end of the current limiting resistor R6 is respectively connected to the collector of the NPN transistor Q2, one end of the resistor R7, and the base of the NPN transistor Q1. The collector of the NPN transistor Q1 is connected to the other end of the resistor R5 in the down-bias resistor, and the emitter of the NPN transistor Q1 is connected to the other end of the resistor R7 and then grounded.

[0052] One end of the first voltage detection resistor R8 is connected to the constant output voltage, and the other end of the first voltage detection resistor R8 is respectively connected to one end of the first voltage detection resistor R9, one end of the resistor R10, and the base of the NPN transistor Q2;

[0053] The other end of the first voltage detection resistor R9 is grounded, and the emitter of the NPN transistor Q2 is connected to the other end of the resistor R10 and then grounded.

[0054] Specifically, the above is the circuit connection relationship between the current limiting resistor, the switching circuit and the drive signal pull-down circuit. The switching circuit and the drive signal pull-down circuit are added on the basis of the constant voltage circuit. When the constant output voltage Vout is within the set range, the NPN transistor Q2 is controlled to be non-conductive; when the constant output voltage exceeds the set range, the NPN transistor Q2 is controlled to be conductive so that the power supply voltage is pulled down to the ground, and after the switching circuit is non-conductive, the constant output voltage is reduced to the set threshold, thereby improving the safety of the product.

[0055] Furthermore, the driving signal pull-down circuit is used to calculate the first voltage of the first voltage detection resistor R8 and the second voltage of the second voltage detection resistor R9 according to the constant output voltage and the set voltage division ratio when the constant output voltage is within the set range; and drive the NPN transistor Q2 to be non-conductive according to the second voltage;

[0056] The first voltage is greater than the driving turn-on voltage of the NPN transistor Q2 , and the second voltage is less than the driving turn-on voltage of the NPN transistor Q2 .

[0057] Furthermore, the driving signal pull-down circuit is used to calculate the third voltage of the first voltage detection resistor R8 and the fourth voltage of the second voltage detection resistor R9 according to the constant output voltage and the set voltage division ratio when the constant output voltage exceeds the set range; and drive the NPN transistor Q2 to conduct according to the fourth voltage;

[0058] The fourth voltage is greater than the driving turn-on voltage of the NPN transistor Q2.

[0059] Specifically, a switching circuit and a drive signal pull-down circuit are added to the constant voltage circuit. When the constant output voltage Vout is within the set range, the NPN transistor Q2 is driven to be non-conductive according to the second voltage of the second voltage detection resistor R9; when the constant output voltage exceeds the set range, the NPN transistor Q2 is driven to be conductive according to the fourth voltage of the second voltage detection resistor R9; so that the power supply voltage is pulled down to the ground, and after the switch circuit is non-conductive, the constant output voltage is reduced to the set threshold, thereby improving the safety of the product.

[0060] Furthermore, the constant voltage circuit also includes an upper bias resistor and a lower bias resistor; the three-terminal voltage regulator is connected to one end of the upper bias resistor and one end of the lower bias resistor respectively, and the other end of the upper bias resistor is connected to the constant output voltage.

[0061] Furthermore, the upper bias resistor includes resistor R2 and resistor R3, and the lower bias resistor includes resistor R4 and resistor R5;

[0062] The three-terminal voltage regulator is connected to one end of the resistor R3 and one end of the resistor R4 respectively, the other end of the resistor R3 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to a constant output voltage;

[0063] The other end of the resistor R4 is connected to one end of the resistor R5.

[0064] Furthermore, the constant voltage circuit is used to calculate the constant output voltage based on the reference voltage and the set voltage division ratio, using the voltage stabilization point of the three-terminal regulator as the reference voltage when the upper bias resistor and the lower bias resistor form a set voltage division ratio.

[0065] Specifically, the supply voltage passes through the current-limiting resistor R6, turning on the NPN transistor Q1. Then, the upper bias resistor and the lower bias resistor form a voltage divider ratio, and the constant output voltage Vout is calculated with the voltage regulation point 2.495V of the three-terminal regulator U1 as the reference voltage. For details, refer to formula (1).

[0066] In addition, the constant voltage circuit also includes an optocoupler, pin 1 of the optocoupler is connected to one end of the current limiting resistor R1, the other end of the current limiting resistor R1 is connected to the 12V power supply voltage, and pin 2 of the optocoupler is connected to the three-terminal voltage regulator.

[0067] An embodiment of the present invention provides a lithium battery charger including the control circuit for preventing output voltage from running out of control as described above.

[0068] The computer program product provided in the embodiments of the present invention includes a computer-readable storage medium storing program code. The instructions included in the program code can be used to execute the methods described in the previous method embodiments. For specific implementation, please refer to the method embodiments and will not be repeated here.

[0069] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described systems and devices can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0070] In addition, in the description of the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0071] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0072] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0073] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A control circuit for preventing output voltage from losing control, characterized in that: The control circuit includes a constant voltage circuit, a switch circuit, a power supply voltage, and a drive signal pull-down circuit, wherein the constant voltage circuit includes a three-terminal voltage regulator, and the drive signal pull-down circuit includes an NPN transistor Q2; The power supply voltage is connected to the switch circuit and the drive signal pull-down circuit respectively, the drive signal pull-down circuit is connected to the switch circuit, and the switch circuit is connected to the constant voltage circuit; The switch circuit is configured to be in an open state under the drive of the power supply voltage; The constant voltage circuit is used to calculate a constant output voltage according to the reference voltage of the three-terminal regulator and a set voltage division ratio; The drive signal pull-down circuit is used to control the NPN transistor Q2 to be non-conductive when the constant output voltage is within a set range; When the constant output voltage exceeds the set range, the NPN transistor Q2 is controlled to be turned on so that the supply voltage is pulled down to ground, and after the switch circuit is turned off, the constant output voltage is reduced to a set threshold.

2. The control circuit for preventing output voltage from running out of control according to claim 1, characterized in that: The control circuit further includes a current limiting resistor R6, the switch circuit includes an NPN transistor Q1 and a resistor R7, and the drive signal pull-down circuit includes a first voltage detection resistor R8, a second voltage detection resistor R9 and a resistor R10; One end of the first voltage detection resistor R8 is connected to the constant output voltage, and the other end of the first voltage detection resistor R8 is respectively connected to one end of the first voltage detection resistor R9, one end of the resistor R10, and the base of the NPN transistor Q2; The other end of the second voltage detection resistor R9 is grounded, and the emitter of the NPN transistor Q2 is connected to the other end of the resistor R10 and then grounded.

3. The control circuit for preventing output voltage from running out of control according to claim 2, wherein: One end of the current limiting resistor R6 is connected to the power supply voltage, and the other end of the current limiting resistor R6 is respectively connected to the collector of the NPN transistor Q2, one end of the resistor R7, and the base of the NPN transistor Q1. The collector of the NPN transistor Q1 is connected to the other end of the resistor R5 in the down-bias resistor, and the emitter of the NPN transistor Q1 is connected to the other end of the resistor R7 and then grounded.

4. The control circuit for preventing output voltage from running out of control according to claim 2, wherein: The switch circuit is used to enable the NPN transistor Q1 to be in the open state under the drive of the power supply voltage.

5. The control circuit for preventing output voltage from running out of control according to claim 2, wherein: The drive signal pull-down circuit is configured to calculate a first voltage of the first voltage detection resistor R8 and a second voltage of the second voltage detection resistor R9 according to the constant output voltage and the set voltage division ratio when the constant output voltage is within a set range; and drive the NPN transistor Q2 to be non-conductive according to the second voltage; The first voltage is greater than the driving start voltage of the NPN transistor Q2, and the second voltage is less than the driving start voltage of the NPN transistor Q2.

6. The control circuit for preventing output voltage from running out of control according to claim 2, characterized in that: The drive signal pull-down circuit is configured to calculate a third voltage of the first voltage detection resistor R8 and a fourth voltage of the second voltage detection resistor R9 according to the constant output voltage and the set voltage division ratio when the constant output voltage exceeds the set range; and drive the NPN transistor Q2 to conduct according to the fourth voltage; The fourth voltage is greater than the driving turn-on voltage of the NPN transistor Q2.

7. The control circuit for preventing output voltage from running out of control according to claim 1, wherein: The constant voltage circuit further includes an upper bias resistor and a lower bias resistor; the three-terminal voltage regulator is connected to one end of the upper bias resistor and one end of the lower bias resistor respectively, and the other end of the upper bias resistor is connected to the constant output voltage.

8. The control circuit for preventing output voltage from running out of control according to claim 7, characterized in that: The upper bias resistor includes a resistor R2 and a resistor R3, and the lower bias resistor includes a resistor R4 and a resistor R5; The three-terminal voltage regulator is connected to one end of the resistor R3 and one end of the resistor R4 respectively, the other end of the resistor R3 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to the constant output voltage; The other end of the resistor R4 is connected to one end of the resistor R5.

9. The control circuit for preventing output voltage from running out of control according to claim 7, characterized in that: The constant voltage circuit is configured to use the voltage stabilization point of the three-terminal regulator as the reference voltage when the upper bias resistor and the lower bias resistor form the set voltage division ratio; The constant output voltage is calculated according to the reference voltage and the set voltage division ratio.

10. A lithium battery charger, characterized in that: The control circuit for preventing output voltage from running out of control comprises the control circuit according to any one of claims 1 to 9.

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