Control circuit for preventing runaway of output voltage and lithium battery charger

Abstract

The utility model provides control circuit and lithium battery charger of preventing output voltage out of control, control circuit includes constant voltage circuit, switching circuit, power supply voltage, drive signal pull -down circuit, and constant voltage circuit includes three terminal stabiliser, and drive signal pull -down circuit includes NPN triode Q2, under the drive of power supply voltage, switching circuit is the open state, constant voltage circuit calculates constant output voltage according to the reference voltage of three terminal stabiliser and the set voltage division ratio, when constant output voltage is in the set range, drive signal pull -down circuit controls NPN triode Q2 and does not conduct, when constant output voltage exceeds the set range, control NPN triode Q2 and conducts, to make power supply voltage pull -down to ground, and after switching circuit does not conduct, constant output voltage reduces to the set threshold value, on the basis of constant voltage circuit increases switching circuit and drive signal pull -down circuit, when constant output voltage is out of control, falls to the set threshold value, improves the security of product.

Description

Technical Field

[0001] This utility model relates to the field of charger technology, and in particular to a control circuit for preventing output voltage runaway and a lithium battery charger. Background Technology

[0002] Currently, constant voltage control circuits include a three-terminal regulator, an optocoupler, an upper bias resistor, and a lower bias resistor. The voltage division ratio is changed by adjusting the values ​​of the upper and lower bias resistors, thereby changing the output voltage. The lower bias resistor may consist of one or two resistors.

[0003] However, in the down bias resistors, when any one of the resistors is short-circuited, the output voltage will run out of control, that is, the output voltage will exceed the set voltage by a large margin, resulting in poor product safety. Utility Model Content

[0004] In view of this, the purpose of this utility model is to provide a control circuit and lithium battery charger to prevent output voltage runaway. By adding a switching circuit and a drive signal pull-down circuit to the constant voltage circuit, when the constant output voltage runs away, it drops to a set threshold, thereby improving the safety of the product.

[0005] In a first aspect, the present invention provides a control circuit 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 regulator, and the drive signal pull-down circuit includes an NPN transistor Q2.

[0006] 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, and the switching circuit is connected to the constant voltage circuit.

[0007] The switching circuit is used to be in the open state under the drive of the power supply voltage;

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

[0009] The drive signal pull-down circuit is used to control the NPN transistor Q2 to not conduct when the constant output voltage is within the set range;

[0010] When the constant output voltage exceeds the set range, the NPN transistor Q2 is turned on to pull the supply voltage down to ground. After the switching circuit is turned off, the constant output voltage is reduced to the set threshold.

[0011] Furthermore, the control circuit also includes a current-limiting resistor R6, the switching 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 sensing resistor R8 is connected to the constant output voltage, and the other end of the first voltage sensing resistor R8 is connected to one end of the first voltage sensing resistor R9, one end of the resistor R10, and the base of the NPN transistor Q2.

[0013] The other end of the second voltage sensing 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 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 lower bias resistor R5, 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 put the NPN transistor Q1 into the open state under the drive of the supply voltage.

[0016] Furthermore, the drive 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 based on the constant output voltage and the set voltage division ratio when the constant output voltage is within a set range; and to drive the NPN transistor Q2 to turn off based on the second voltage.

[0017] Wherein, the first voltage is greater than the drive turn-on voltage of the NPN transistor Q2, and the second voltage is less than the drive turn-on voltage of the NPN transistor Q2.

[0018] Furthermore, the drive 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 based on 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 based on the fourth voltage.

[0019] The fourth voltage is greater than the drive 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 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 resistors R2 and R3, and the lower bias resistor includes resistors R4 and R5;

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

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

[0024] Furthermore, the constant voltage circuit is used to calculate the constant output voltage based on the reference voltage, using the regulated 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; and based on the reference voltage and the set voltage division ratio.

[0025] Secondly, this utility model embodiment provides a lithium battery charger, including the control circuit described above for preventing output voltage runaway.

[0026] This utility model provides a control circuit and a lithium battery charger to prevent output voltage runaway. The control circuit includes a constant voltage circuit, a switching circuit, a supply voltage, and a drive signal pull-down circuit. The constant voltage circuit includes a three-terminal regulator, and the drive signal pull-down circuit includes an NPN transistor Q2. The supply voltage is connected to both the switching circuit and the drive signal pull-down circuit. The drive signal pull-down circuit is connected to the switching circuit, and the switching circuit is connected to the constant voltage circuit. Under the drive of the supply voltage, the switching circuit is in the open state. The constant voltage circuit calculates a constant output voltage based on the reference voltage of the three-terminal regulator and the set voltage division ratio. When the constant output voltage is within the set range, the drive signal pull-down circuit controls the NPN transistor Q2 to not conduct. When the constant output voltage exceeds the set range, the NPN transistor Q2 is controlled to conduct, so that the supply voltage is pulled down to ground. After the switching circuit is de-conducted, the constant output voltage drops to the set threshold. By adding a switching circuit and a drive signal pull-down circuit to the constant voltage circuit, when the constant output voltage runs away, it drops to the set threshold, thereby improving the safety of the product.

[0027] Other features and advantages of this invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objectives and other advantages of this invention are realized and obtained through the structures particularly pointed out in the description, claims, and drawings.

[0028] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0029] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the control circuit for preventing output voltage runaway provided in Embodiment 1 of this utility model;

[0031] Figure 2 This is a schematic diagram of another control circuit for preventing output voltage runaway provided in Embodiment 1 of this utility model;

[0032] Figure 3 This is a schematic diagram of the control circuit structure for preventing output voltage runaway provided in Embodiment 1 of this utility model.

[0033] icon:

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

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0036] To facilitate understanding of this embodiment, the following is a detailed description of the embodiment of this utility model.

[0037] Example 1:

[0038] Figure 1This is a schematic diagram of a control circuit for preventing output voltage runaway provided in Embodiment 1 of this utility model.

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

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

[0041] Switching circuit 2 is used to be in the open state under the drive of power supply voltage 3;

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

[0043] The drive signal pull-down circuit 4 is used to control the NPN transistor Q2 to not conduct when the constant output voltage is within the set range;

[0044] When the constant output voltage exceeds the set range, the NPN transistor Q2 is turned on to pull the supply voltage to ground. After the switching circuit is turned off, the constant output voltage decreases to the set threshold. The set threshold is the reference voltage of the three-terminal regulator.

[0045] Specifically, existing constant voltage control circuits include a three-terminal regulator, an optocoupler, an upper bias resistor, and a lower bias resistor. The voltage division ratio is changed by adjusting the values ​​of the upper and lower bias resistors, thereby altering the output voltage. The lower bias resistor may consist of one or two resistors. However, in the lower bias resistor, if either resistor is short-circuited, the output voltage will become uncontrollable, exceeding the set voltage significantly, resulting in poor product safety.

[0046] In this application, the control circuit further includes a current-limiting resistor R6, the switching 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 regulator, an upper bias resistor, and a lower bias resistor. (Refer to...) Figure 3 The supply voltage drives the NPN transistor Q1 to conduct through the current-limiting resistor R6, keeping it continuously open. Then, the upper bias resistors R2 and R3, along with the lower bias resistors R4 and R5, form a voltage divider. The voltage regulation point of the three-terminal regulator U1, 2.495V, is used as the reference voltage for the lower bias resistor. Based on the reference voltage and the set voltage divider ratio, a constant output voltage is calculated. (Refer to...) Figure 3 The constant output voltage can be obtained through 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] This application adds a switching circuit and a drive signal pull-down circuit to the constant voltage circuit. The constant output voltage Vout is driven by the voltage divider between the first voltage detection resistor R8 and the second voltage detection resistor R9. The voltage division ratio between the first voltage detection resistor R8 and the second voltage detection resistor R9 is calculated. When the constant output voltage Vout is within the set range, the NPN transistor Q2 is controlled to not conduct. The voltage divided by the first voltage detection resistor R8 and the second voltage detection resistor R9 is lower than the drive turn-on 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 to conduct by the voltage from the second voltage sensing resistor R9. This causes the supply voltage to be directly pulled down to ground, and NPN transistor Q1 receives no drive signal, thus not conducting. The voltage divider circuit between the upper and lower bias resistors then disconnects, and the constant output voltage drops to the set threshold, thereby improving product safety. The supply voltage can be 5V, but is not limited to the above value and can be set according to requirements.

[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 connected to the collector of NPN transistor Q2, one end of resistor R7, and the base of NPN transistor Q1. The collector of NPN transistor Q1 is connected to the other end of resistor R5 in the lower bias resistor, and the emitter of NPN transistor Q1 is connected to the other end of resistor R7 and then grounded.

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

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

[0054] Specifically, the above describes the circuit connection relationship between the current-limiting resistor, the switching circuit, and the drive signal pull-down circuit. By adding a switching circuit and a drive signal pull-down circuit to the constant voltage circuit, when the constant output voltage Vout is within the set range, the NPN transistor Q2 is controlled to not conduct; when the constant output voltage exceeds the set range, the NPN transistor Q2 is controlled to conduct, so that the supply voltage is pulled down to ground. After the switching circuit is not conducted, the constant output voltage is reduced to the set threshold, thereby improving the safety of the product.

[0055] Furthermore, the drive 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 based on the constant output voltage and the set voltage division ratio when the constant output voltage is within the set range; and to drive the NPN transistor Q2 to turn off based on the second voltage.

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

[0057] Furthermore, the drive 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 based on 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 based on the fourth voltage.

[0058] Among them, the fourth voltage is greater than the drive 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 de-conducted based on the second voltage of the second voltage detection resistor R9. When the constant output voltage exceeds the set range, the NPN transistor Q2 is turned on based on the fourth voltage of the second voltage detection resistor R9. This causes the supply voltage to be pulled down to ground, and after the switching circuit is de-conducted, 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 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 resistors R2 and R3, and the lower bias resistor includes resistors R4 and R5.

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

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

[0064] Furthermore, the constant voltage circuit is used to calculate a constant output voltage based on the voltage regulation point of the three-terminal regulator, given that the upper and lower bias resistors form a set voltage division ratio.

[0065] Specifically, the power supply voltage passes through the current-limiting resistor R6, which puts the NPN transistor Q1 in the open state; 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 of the three-terminal regulator U1 of 2.495V as the reference voltage, as shown in 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, and the other end of the current-limiting resistor R1 is connected to the 12V power supply voltage. Pin 2 of the optocoupler is connected to the three-terminal regulator.

[0067] This utility model embodiment provides a lithium battery charger, including the control circuit described above to prevent output voltage runaway.

[0068] The computer program product provided in this embodiment 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 preceding method embodiments. For specific implementation details, please refer to the method embodiments, which will not be repeated here.

[0069] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and apparatus described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0070] Furthermore, in the description of the embodiments of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0071] If the aforementioned functions are implemented as 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 this utility model, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this utility model. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0072] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. 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 merely specific implementations of this utility model, used to illustrate the technical solution of this utility model, and not to limit it. The protection scope of this utility model is not limited thereto. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the technical scope disclosed in this utility model. These modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model, and should all be covered within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the protection scope of the claims.

Claims

1. A control circuit for preventing runaway of an output voltage, characterized by comprising: 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 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, and the switching circuit is connected to the constant voltage circuit. The switching circuit is used to be in the open state under the drive of the power supply voltage; The constant voltage circuit is used to calculate a constant output voltage based on the reference voltage of the three-terminal regulator and the set voltage division ratio. The drive signal pull-down circuit is used to control the NPN transistor Q2 to not conduct when the constant output voltage is within the set range; When the constant output voltage exceeds the set range, the NPN transistor Q2 is turned on to pull the supply voltage down to ground. After the switching circuit is turned off, the constant output voltage is reduced to the set threshold.

2. The control circuit for preventing runaway of an output voltage according to claim 1, characterized by, The control circuit also includes a current-limiting resistor R6, the switching 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 sensing resistor R8 is connected to the constant output voltage, and the other end of the first voltage sensing resistor R8 is connected to one end of the first voltage sensing resistor R9, one end of the resistor R10, and the base of the NPN transistor Q2. The other end of the second voltage sensing 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 runaway of an output voltage according to claim 2, wherein, One end of the current-limiting resistor R6 is connected to the power supply voltage. The other end of the current-limiting resistor R6 is 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 lower bias resistor R5. 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 runaway of an output voltage according to claim 2, wherein The switching circuit is used to put the NPN transistor Q1 in the open state under the drive of the supply voltage.

5. The control circuit for preventing runaway of an output voltage according to claim 2, wherein The drive 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 based on the constant output voltage and the set voltage division ratio when the constant output voltage is within a set range; and to drive the NPN transistor Q2 to turn off based on the second voltage. Wherein, the first voltage is greater than the drive turn-on voltage of the NPN transistor Q2, and the second voltage is less than the drive turn-on voltage of the NPN transistor Q2.

6. The control circuit for preventing runaway of an output voltage according to claim 2, wherein The drive 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 based on 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 based on the fourth voltage. The fourth voltage is greater than the drive turn-on voltage of the NPN transistor Q2.

7. The control circuit for preventing runaway of an output voltage according to claim 1, wherein, The constant voltage circuit also includes an upper bias resistor and a lower bias resistor; the three-terminal 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 runaway according to claim 7, characterized in that, The upper bias resistor includes resistors R2 and R3, and the lower bias resistor includes resistors R4 and R5; The three-terminal regulator is connected to one end of resistor R3 and one end of resistor R4 respectively. The other end of resistor R3 is connected to one end of resistor R2, and the other end of resistor R2 is connected to the constant output voltage. The other end of resistor R4 is connected to one end of resistor R5.

9. The control circuit for preventing runaway of an output voltage according to claim 7, wherein The constant voltage circuit is used to use the voltage regulation 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 based on the reference voltage and the set voltage division ratio.

10. A lithium battery charger characterized by, Includes the control circuit for preventing output voltage runaway as described in any one of claims 1 to 9.

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