CN104037737A - Current overcurrent and undervoltage protection circuit - Google Patents
Current overcurrent and undervoltage protection circuit Download PDFInfo
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- CN104037737A CN104037737A CN201410304203.XA CN201410304203A CN104037737A CN 104037737 A CN104037737 A CN 104037737A CN 201410304203 A CN201410304203 A CN 201410304203A CN 104037737 A CN104037737 A CN 104037737A
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Abstract
The invention provides a current overcurrent and undervoltage protection circuit. The current overcurrent and undervoltage protection circuit aims to solve the technical problem that a current overcurrent and undervoltage protection circuit in the prior art is complex in design and high in circuit cost. The current overcurrent and undervoltage protection circuit comprises a battery input end, an input place, a battery output end, an output place, a control circuit and an NMOS transistor, and the control circuit comprises three electronic switches and seven resistors. The battery input end is connected with the battery output end, a source electrode and a drain electrode of the NMOS transistor are connected between the input place and the output place in series, and the control circuit controls the NMOS transistor to be switched off to achieve connection and disconnection of a power supply circuit. The three electronic switches are in linkage and matched, and when output currents are higher than a set threshold value or output voltages are lower than the set threshold value, the protection circuit can switch off the power supply circuit to protect a battery against damage of overcurrents and undervoltages. The circuit is achieved only by depending on the electronic switches and the resistors, is simple in design and low in cost, is protected through a hardware circuit, and is high in reaction speed.
Description
Technical Field
The invention relates to the field of circuit design, in particular to a battery overcurrent and undervoltage protection circuit.
Background
The battery is an indispensable component of the electronic product, and the quality of the battery directly determines the quality of the whole electronic product. And improper use of the battery may cause damage to the battery.
Two of the most common conditions of damage to the battery are over-current and under-voltage. When the battery works in an overcurrent and undervoltage state for a long time, irreversible damage can be caused to the battery. Therefore, protecting the battery from over-current and under-voltage is a problem that must be considered by modern electronic engineers during product development. However, the battery protection circuit in the prior art is usually complex in circuit design, or a circuit formed by an integrated circuit and peripheral components is adopted, so that the circuit cost is high, and the battery protection circuit is not suitable for being widely applied to electronic products.
Disclosure of Invention
The embodiment of the application provides a battery overcurrent and undervoltage protection circuit to solve the technical problems that the battery overcurrent and undervoltage protection circuit in the prior art is complex in design and high in circuit cost.
In order to solve the above technical problem, the embodiment of the present application is implemented by using the following technical solutions:
the battery overcurrent and undervoltage protection circuit comprises a battery input end, an input ground, a battery output end, an output ground, a control circuit and an NMOS (N-channel metal oxide semiconductor) tube, wherein the battery input end is connected with the battery output end, a source electrode and a drain electrode of the NMOS tube are connected between the input ground and the output ground in series, and the control circuit controls the on-off of the NMOS tube to realize the connection and the disconnection of a power supply loop; the control circuit comprises a first electronic switch, a second electronic switch, a third electronic switch, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor and a seventh resistor; wherein,
the first resistor and the second resistor are connected in series between the battery input end and the input ground; the third resistor and the fourth resistor are connected in series between the battery output end and the output ground; the first end of the first electronic switch is connected with the source end of the NMOS tube, the second end of the first electronic switch is connected with the input ground, and the third end of the first electronic switch is connected with the first end of the sixth resistor; the first end of the sixth resistor is connected to the third end of the first electronic switch, and the second end of the sixth resistor is connected to the connection end of the third resistor and the fourth resistor; the first end of the second electronic switch is connected to the connecting end of the first resistor and the second resistor, the second end of the second electronic switch is connected to the input end of the battery, and the third end of the second electronic switch is connected to the grid electrode of the NMOS tube; the first end of the fifth resistor is connected with the third end of the second electronic switch, and the second end of the fifth resistor is connected with the source electrode of the NMOS tube; the seventh resistor is connected between the input ground and the source terminal of the NMOS tube in series; and the first end of the third electronic switch is connected to the connecting end of the third resistor and the fourth resistor, the second end of the third electronic switch is connected to the output end of the battery, and the third end of the third electronic switch is connected to the connecting end of the first resistor and the second resistor.
Further, the first electronic switch is an NPN triode, a first end of which is a base, a second end of which is an emitter, and a third end of which is a collector; the second electronic switch and the third electronic switch are PNP triodes, wherein the first end is a base electrode, the second end is an emitting electrode, and the third end is a collector electrode.
Furthermore, the first electronic switch is an NMOS transistor, a first end of the NMOS transistor is a gate, a second end of the NMOS transistor is a source, and a third end of the NMOS transistor is a drain; the second electronic switch and the third electronic switch are PMOS tubes, wherein the first end is a grid electrode, the second end is a source electrode, and the third end is a grid electrode.
Further, the product of the resistance value of the seventh resistor and the current protection threshold is greater than or equal to the on-state voltage of the first electronic switch.
Further, the voltage division of the first resistor and the second resistor enables the voltage drop across the first resistor to be greater than or equal to the on-state voltage of the second electronic switch, the voltage division of the third resistor and the fourth resistor enables the voltage drop across the third resistor to be smaller than the on-state voltage of the third electronic switch, and the voltage division of the third resistor and the sixth resistor enables the voltage drop across the third resistor to be greater than or equal to the on-state voltage of the third electronic switch.
The embodiment of the application also provides a battery overcurrent and undervoltage protection circuit, which comprises a battery input end, an input ground, a battery output end, an output ground, a control circuit and a PMOS (P-channel metal oxide semiconductor) tube, wherein the input ground is connected with the output ground, a source electrode and a drain electrode of the PMOS tube are connected in series between the battery input end and the battery output end, the control circuit controls the conduction and the cut-off of the PMOS tube to realize the connection and the cut-off of a power supply circuit, and the control circuit comprises a first electronic switch, a second electronic switch, a third electronic switch, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor and a seventh resistor; wherein the first and second resistors are connected in series between the input ground and the battery input terminal; the third resistor and the fourth resistor are connected in series between the battery output end and the output ground; the first end of the first electronic switch is connected with the source end of the PMOS tube, the second end of the first electronic switch is connected with the input end of the battery, and the third end of the first electronic switch is connected with the first end of the sixth resistor; the first end of the sixth resistor is connected to the third end of the first electronic switch, and the second end of the sixth resistor is connected to the connection end of the third resistor and the fourth resistor; the first end of the second electronic switch is connected to the connecting end of the first resistor and the second resistor, the second end of the second electronic switch is connected to the input ground, and the third end of the second electronic switch is connected to the grid electrode of the PMOS tube; the first end of the fifth resistor is connected with the third end of the second electronic switch, and the second end of the fifth resistor is connected with the source electrode of the PMOS tube; the seventh resistor is connected between the battery input end and the source end of the PMOS tube in series; and the first end of the third electronic switch is connected to the connecting end of the third resistor and the fourth resistor, the second end of the third electronic switch is connected to the output ground, and the third end of the third electronic switch is connected to the connecting end of the first resistor and the second resistor.
Furthermore, the first electronic switch is a PNP triode, the first end of the PNP triode is a base, the second end of the PNP triode is an emitter, and the third end of the PNP triode is a collector; the second electronic switch and the third electronic switch are NPN triodes, wherein the first end is a base electrode, the second end is an emitting electrode, and the third end is a collector electrode.
Furthermore, the first electronic switch is a PMOS transistor, a first end of the PMOS transistor is a gate, a second end of the PMOS transistor is a source, and a third end of the PMOS transistor is a drain; the second electronic switch and the third electronic switch are NMOS tubes, wherein the first end is a grid electrode, the second end is a source electrode, and the third end is a grid electrode.
Further, the product of the resistance value of the seventh resistor and the current protection threshold is greater than or equal to the on-state voltage of the first electronic switch.
Further, the voltage division of the first resistor and the second resistor enables the voltage drop across the first resistor to be greater than or equal to the on-state voltage of the second electronic switch, the voltage division of the third resistor and the fourth resistor enables the voltage drop across the third resistor to be smaller than the on-state voltage of the third electronic switch, and the voltage division of the third resistor and the sixth resistor enables the voltage drop across the third resistor to be greater than or equal to the on-state voltage of the third electronic switch.
Compared with the prior art, the technical scheme provided by the embodiment of the application has the following technical effects or advantages: according to the overcurrent and undervoltage protection circuit for the battery, through linkage coordination among the first electronic switch, the second electronic switch and the third electronic switch, when the output current is larger than a set threshold value, the current on the seventh resistor is increased, so that the first electronic switch is switched on, the voltage drop on the third resistor is increased through voltage division of the third resistor and the sixth resistor, the third electronic switch is switched on, the current on the second resistor is increased, the voltage drop on the first resistor is reduced, the second electronic switch is switched off, and the NMOS tube is switched off, so that the circuit automatically cuts off a power supply loop to protect the battery from overcurrent damage; when the output voltage is lower than a set threshold value, the voltage drop on the first resistor is reduced, the second electronic switch is switched off, the NOMS tube is switched off, and the circuit can also automatically switch off the power supply loop to protect the battery from being damaged by undervoltage; compared with the overcurrent and undervoltage protection circuit in the prior art, the overcurrent and undervoltage protection circuit is realized only by the electronic switch and the resistor, is simple in design and low in cost, completely realizes protection by a hardware circuit, and is high in reaction speed.
Drawings
Fig. 1 is a circuit diagram of a battery overcurrent and undervoltage protection circuit according to a first embodiment of the present application;
fig. 2 is a circuit diagram of a battery over-current and under-voltage protection circuit according to a first embodiment of the present application;
fig. 3 is a circuit diagram of a battery over-current and under-voltage protection circuit according to a first embodiment of the present application;
fig. 4 is a circuit diagram of a battery overcurrent undervoltage protection circuit according to a second embodiment of the present application;
fig. 5 is a circuit diagram of a battery over-current and under-voltage protection circuit according to a second embodiment of the present application;
fig. 6 is a circuit diagram of a battery over-current and under-voltage protection circuit according to a second embodiment of the present application.
Detailed Description
The embodiment of the application provides a battery overcurrent and undervoltage protection circuit to solve the technical problems of complex design and high circuit cost of the battery overcurrent and undervoltage protection circuit in the prior art; the technical effects of simple circuit design, low cost and high reaction speed are realized.
In order to better understand the technical solutions, the technical solutions will be described in detail below with reference to the drawings and specific embodiments.
Example one
Fig. 1 is a circuit diagram of a battery overcurrent and undervoltage protection circuit according to an embodiment of the present application, and the circuit diagram includes a battery input terminal Vin and an input ground Gin, a battery output terminal Vout and an output ground Gout, and a control circuit 10 and an NMOS transistor Q4, where the battery input terminal Vin is connected to the battery output terminal Vout, a source and a drain of the NMOS transistor Q4 are connected in series between the input ground Gin and the output ground Gout, and the control circuit 10 controls on and off of the NMOS transistor to implement connection and disconnection of a discharge circuit.
The control circuit 10 includes a first electronic switch Q1, a second electronic switch Q2, and a third electronic switch Q3, as well as a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7.
The first resistor R1 and the second resistor R2 are connected in series between the battery input terminal Vin and the input ground Gin; the third resistor R3 and the fourth resistor R4 are connected in series between the battery output terminal Vout and the output ground Gout; a first terminal of the first electronic switch Q1 is connected to the source terminal of the NMOS transistor Q4, a second terminal is connected to the input ground Gin, and a third terminal is connected to the first terminal of the sixth resistor R6; a first end of the sixth resistor R6 is connected to the third end of the first electronic switch Q1, and a second end is connected to the connection end of the third resistor R3 and the fourth resistor R4; a first end of the second electronic switch Q2 is connected to the connection end of the first resistor R1 and the second resistor R2, a second end is connected to the battery input terminal Vin, and a third end is connected to the gate of the NMOS transistor Q4; a first end of the fifth resistor R5 is connected with a third end of the second electronic switch Q2, and a second end is connected with the source electrode of the NMOS transistor Q4; the seventh resistor R7 is connected in series between the input ground Gin and the source terminal of the NMOS transistor Q4; the third electronic switch Q3 has a first terminal connected to the connection terminal of the third resistor R3 and the fourth resistor R4, a second terminal connected to the battery output terminal Vout, and a third terminal connected to the connection terminal of the first resistor R1 and the second resistor R2.
When the battery does not generate overcurrent and undervoltage, the Q2 is ensured to be conducted, the Q3 is not conducted, and the Q2 is conducted, so that the Q4 is conducted, the conduction of a battery power supply circuit and a power supply loop is realized, and the battery can normally supply power to the electronic product; when the output current is greater than a set threshold value, the current of R7 is increased, the voltage drop of R7 is increased, Q1 is conducted, the voltage division of R3 and R6 is used for increasing the voltage drop of R3, Q3 is conducted, the current of R2 is increased, the voltage drop of R1 is reduced, Q2 is not conducted, an NMOS tube is disconnected, and a power supply loop is automatically cut off by the circuit to protect the battery from overcurrent; when the output voltage is lower than the set threshold value, so that the voltage drop on the R1 is reduced, the Q2 is not conducted, the NOMS tube is disconnected, and the circuit can also automatically cut off the power supply loop to protect the battery from the damage of undervoltage.
Compared with the overcurrent and undervoltage protection circuit in the prior art, the overcurrent and undervoltage protection circuit for the battery is realized only by three electronic switches and seven resistors, is simple in design and low in cost, completely realizes protection by a hardware circuit, and is high in reaction speed.
As shown in fig. 2, the first electronic switch Q1 may be an NPN transistor, and the second electronic switch Q2 and the third electronic switch Q3 may be PNP transistors.
When the battery does not generate overcurrent and undervoltage, the Q2 is ensured to be conducted, and the Q3 is ensured to be not conducted, which is realized by adjusting the resistance values of the resistors R1, R2, R3 and R4. Normally, the on-state voltage of the transistor is about 0.7V (specifically, determined by the parameters of the transistor), and in order to ensure that Q2 is turned on, assuming that the voltage of the battery normally operating is 12V, the resistances of R1 and R2 need to satisfy:the pressure drop on R1 is more than or equal to 0.7V; to ensure that Q3 does not conduct, the resistances of R3 and R4 need to satisfy:i.e., a pressure drop across R3 of less than 0.7V; thus, when Q2 is turned on, a current flows through the resistor R5, a voltage drop occurs in R5, and since the gate and the source of the NMOS transistor Q4 are connected to both ends of R5, respectively, the voltage drop occurring in R5 satisfies the requirement between the gate and the source of Q4 Then, as long as the voltage drop across R5 meets the threshold voltage for Q4 to turn on, Q4 turns on, and Q4 turns on to turn on the discharge circuit of the battery, so that the battery can normally supply power to the electronic product. It is assumed here that R2=200，R4=500Then R1 and R3 take on the value of 12.4And R5 takes the value 5And (4) finishing.
When overcurrent occurs, for example, if the set overcurrent threshold is 1A, and the voltage drop across the resistor R7 is greater than or equal to 0.7V (usually equal to 0.7V), the voltage difference between the base and emitter of Q1 may be greater than or equal to 0.7V, so that Q1 is turned on, after Q1 is turned on, the voltage drop across R3 and R6 needs to be greater than or equal to 0.7V across R3, so that Q3 is turned on, after Q3 is turned on, the current across R2 is increased, the voltage drop across R1 is reduced, Q1 is turned off from on, after Q2 is turned off, there is no voltage drop across R5, and then NMOS Q4 is turned off, so that the power supply circuit is turned off, and overcurrent protection for the battery is achieved. As mentioned above, the partial pressure of R3 and R6 needs to make the voltage drop of R3 be 0.7V or more, and the partial pressure of R3 and R4 needs to make the voltage drop of R3 be less than 0.7V, when R4 takes 500 valueAnd R3 takes the value 12.4And R6 takes the value 200The above conditions can be satisfied.
In order to adapt the circuit to batteries with different voltages, variable resistors may be used for R1 and R3.
It is noted that the value of R7 is related to the threshold current of the protection circuit, if R7 is 0.7If the current of R7 is 1A, the voltage drop of R7 is 0.7V, and the condition of Q1 being turned on can be satisfied, then the current protection threshold of the circuit is 1A; if R7 is 1.4Then, when the voltage difference between the base and the emitter of the Q1 is 0.7V when the circuit on the R7 is 0.5A, the current protection threshold of the circuit is 0.5A; it can be seen that by adjusting the resistance value of the seventh resistor R7, the current protection threshold of the circuit can be set, so that the protection threshold of the protection circuit can be controlled.
As shown in fig. 3, the first electronic switch Q1 may be an NMOS transistor, and the second electronic switch Q2 and the third electronic switch Q3 may be PMOS transistors.
When the battery does not generate overcurrent and undervoltage, only Q2 is ensured to be conducted and Q3 is ensured to be not conducted, and when the conduction voltage of the PMOS tube is known (usually, the conduction voltage can be referred to a parameter manual of PMOS), the resistance values of the resistors R1, R2, R3 and R4 can be adjusted to realize the overvoltage and undervoltage protection. Assuming that the voltage of the battery is 12V for normal operation, in order to ensure that Q2 is conducted, the resistances of R1 and R2 need to satisfy:the voltage difference between the voltage applied to the source electrode of the PMOS tube Q2 and the voltage applied to the grid electrode is greater than or equal to the conduction voltage of the PMOS tube, namely the voltage drop of R1 is greater than or equal to the conduction voltage of the PMOS tube, so that the Q2 is conducted; to ensure that Q3 does not conduct, the resistances of R3 and R4 need to satisfy:less than the conduction voltage of the PMOS transistor, namely, the voltage drop of R3 is less than the conduction voltage of the PMOS transistor Q3, the voltage difference between the voltage applied to the source electrode of the PMOS transistor Q3 and the voltage applied to the grid electrode is less than the conduction voltage of the PMOS transistor, so that the Q3 is not conducted; thus, when Q2 is turned on, a current flows through the resistor R5, a voltage drop occurs in R5, and since the gate and the source of the NMOS transistor Q4 are connected to both ends of R5, respectively, the voltage drop occurring in R5 satisfies the requirement between the gate and the source of Q4 Then, as long as the voltage drop across R5 meets the threshold voltage for Q4 to turn on, Q4 turns on, and Q4 turns on to turn on the discharge circuit of the battery, so that the battery can normally supply power to the electronic product.
When overcurrent occurs, for example, the set overcurrent threshold is 1A, at this time, the voltage drop across the resistor R7 is equal to or greater than the on-state voltage of the NMOS transistor Q1, the voltage difference between the voltage across the gate of the NMOS transistor Q1 and the voltage across the source is equal to or greater than the on-state voltage of the NMOS transistor Q1, so that the Q1 is turned on, after the Q1 is turned on, the voltage drop across the R3 is equal to or greater than the on-state voltage of the PMOS transistor due to the partial pressure of the R3 and the R6, so that the Q3 is turned on, after the Q3 is turned on, the current across the R2 is increased, the voltage drop across the R1 is reduced, the Q1 is switched from on to off, after the Q2 is turned off, there is no voltage drop across the R5, the NMOS transistor Q4. As mentioned above, the voltage division of R3 and R6 needs to make the voltage drop of R3 equal to or greater than the PMOS transistor turn-on voltage, and the voltage division of R3 and R4 needs to make the voltage drop of R3 less than the PMOS transistor turn-on voltage.
In order to adapt the circuit to batteries with different voltages, variable resistors may be used for R1 and R3.
It should be noted that the value of R7 is related to the threshold current of the protection circuit, assuming that the turn-on voltage of the NMOS transistor Q1 is a, if R7 is aIf the current at R7 is 1A, and the voltage drop at R7 is AV, the condition of Q1 conduction can be satisfied, and the current protection threshold of the circuit is 1A; if R7 is 2AIf the current protection threshold of the circuit is 0.5A, the circuit on R7 can meet the condition that Q1 is turned on; it can be seen that by adjusting the resistance of the seventh resistor R7, the current protection threshold of the circuit can be set such thatThe protection threshold of the protection circuit is controllable.
In summary, the overcurrent and undervoltage protection circuit for the battery provided by the embodiment of the application can realize overcurrent and undervoltage protection of the battery through linkage coordination among the first electronic switch Q1, the second electronic switch Q2 and the third electronic switch Q3 and proper values of the first resistor, the second resistor and the seventh resistor. When the output current is greater than a set threshold value, the current on R7 is increased, so that Q1 is conducted, the voltage division of R3 and R6 is used for increasing the voltage drop on R3, then Q3 is conducted, so that the current on R2 is increased, the voltage drop on R1 is reduced, so that Q2 is cut off, and then an NMOS tube Q4 is cut off, so that the circuit automatically cuts off a power supply loop to protect the battery from overcurrent damage; when the output voltage is lower than a set threshold value, the voltage drop on the R1 is reduced, the Q2 is cut off, the NOMS tube Q4 is cut off, and the circuit can also automatically cut off the power supply loop to protect the battery from being damaged by undervoltage; compared with the overcurrent and undervoltage protection circuit in the prior art, the overcurrent and undervoltage protection circuit is realized only by the electronic switch and the resistor, is simple in design and low in cost, completely realizes protection by a hardware circuit, and is high in reaction speed.
Example two
Fig. 4 is a circuit diagram of a battery overcurrent and undervoltage protection circuit according to an embodiment of the present application, and the circuit includes a battery input terminal Vin and an input ground Gin, a battery output terminal Vout and an output ground Gout, and a control circuit 10 and a PMOS transistor Q4, where the input ground Gin is connected to the output ground Gout, a source and a drain of an NMOS transistor Q4 are connected in series between the battery input terminal Vin and the battery output terminal Vout, and the control circuit 10 controls on and off of the PMOS transistor to implement connection and disconnection of a discharge circuit.
The control circuit 10 includes a first electronic switch Q1, a second electronic switch Q2, and a third electronic switch Q3, as well as a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7.
The first resistor R1 and the second resistor R2 are connected in series between the input ground Gin and the battery input terminal Vin; the third resistor R3 and the fourth resistor R4 are connected in series between the output ground Gout and the battery output terminal Vout; a first end of the first electronic switch Q1 is connected with a source terminal of the PMOS transistor Q4, a second end is connected with a battery input terminal Vin, and a third end is connected with a first end of the sixth resistor R6; a first end of the sixth resistor R6 is connected to the third end of the first electronic switch Q1, and a second end is connected to the connection end of the third resistor R3 and the fourth resistor R4; a first end of the second electronic switch Q2 is connected to the connection end of the first resistor R1 and the second resistor R2, a second end is connected to the input ground Gin, and a third end is connected to the gate of the PMOS transistor Q4; a first end of the fifth resistor R5 is connected with a third end of the second electronic switch Q2, and a second end is connected with a source electrode of the PMOS transistor Q4; the seventh resistor R7 is connected in series between the battery input terminal Vin and the source terminal of the PMOS transistor Q4; the third electronic switch Q3 has a first terminal connected to the connection terminal of the third resistor R3 and the fourth resistor R4, a second terminal connected to the output ground Gout, and a third terminal connected to the connection terminal of the first resistor R1 and the second resistor R2.
When the battery does not generate overcurrent and undervoltage, the Q2 is ensured to be conducted, the Q3 is not conducted, and the Q2 is conducted, so that the Q4 is conducted, the conduction of a battery power supply circuit and a power supply loop is realized, and the battery can normally supply power to the electronic product; when the output current is greater than a set threshold value, the current of R7 is increased, the voltage drop of R7 is increased, Q1 is conducted, the voltage division of R3 and R6 is used for increasing the voltage drop of R3, Q3 is conducted, the current of R2 is increased, the voltage drop of R1 is reduced, Q2 is not conducted, a PMOS (P-channel metal oxide semiconductor) tube is disconnected, and a circuit automatically cuts off a power supply path to protect a battery from overcurrent; when the output voltage is lower than the set threshold value, so that the voltage drop on the R1 is reduced, the Q2 is not conducted, the POMS tube is disconnected, and the circuit can also automatically cut off the power supply path to protect the battery from the undervoltage.
Compared with the overcurrent and undervoltage protection circuit in the prior art, the overcurrent and undervoltage protection circuit for the battery is realized only by three electronic switches and seven resistors, is simple in design and low in cost, completely realizes protection by a hardware circuit, and is high in reaction speed.
As shown in fig. 5, the first electronic switch Q1 may be a PNP transistor, and the second electronic switch Q2 and the third electronic switch Q3 may be NPN transistors.
When the battery does not generate overcurrent and undervoltage, the Q2 is ensured to be conducted, and the Q3 is ensured to be not conducted, which is realized by adjusting the resistance values of the resistors R1, R2, R3 and R4. Normally, the on-state voltage of the transistor is about 0.7V (specifically, determined by the parameters of the transistor), and in order to ensure that Q2 is turned on, assuming that the voltage of the battery normally operating is 12V, the resistances of R1 and R2 need to satisfy:the pressure drop on R1 is more than or equal to 0.7V; to ensure that Q3 does not conduct, the resistances of R3 and R4 need to satisfy:i.e., a pressure drop across R3 of less than 0.7V; thus, when Q2 is turned on, a current flows through the resistor R5, a voltage drop is generated across R5, and since the source and gate of the PMOS transistor Q4 are connected to both ends of R5, respectively, the voltage drop generated across R5 satisfies the requirement that the source and gate of Q4 are connected to each other Then, as long as the voltage drop across R5 meets the threshold voltage for Q4 to turn on, Q4 turns on, and Q4 turns on to turn on the power supply path of the battery, so that the battery can normally supply power to the electronic product. It is assumed here that R2=200，R4=500Then R1 and R3 take on the value of 12.4And R5 takes the value 5And (4) finishing.
When overcurrent occurs, for example, if the set overcurrent threshold is 1A, and the voltage drop across the resistor R7 is equal to or greater than 0.7V (usually equal to 0.7V), the voltage difference between the emitter and the base of Q1 is equal to or greater than 0.7V, so that Q1 is turned on, after Q1 is turned on, the voltage drop across R3 and R6 needs to be equal to or greater than 0.7V across R3, so that Q3 is turned on, after Q3 is turned on, the current across R2 is increased, the voltage drop across R1 is reduced, Q1 is turned off from on, after Q2 is turned off, there is no voltage drop across R5, and then the PMOS transistor Q4 is turned off, so that the power supply path is cut off, thereby achieving overcurrent protection of the battery. As mentioned above, the partial pressure of R3 and R6 needs to make the voltage drop of R3 be 0.7V or more, and the partial pressure of R3 and R4 needs to make the voltage drop of R3 be less than 0.7V, when R4 takes 500 valueAnd R3 takes the value 12.4And R6 takes the value 200The above conditions can be satisfied.
In order to adapt the circuit to batteries with different voltages, variable resistors may be used for R1 and R3.
It is noted that the value of R7 is related to the threshold current of the protection circuit, if R7 is 0.7If the current of R7 is 1A, the voltage drop of R7 is 0.7V, and the condition of Q1 being turned on can be satisfied, then the current protection threshold of the circuit is 1A; if R7 is 1.4Then the voltage difference between the base and emitter of Q1 is 0.7V when the circuit at R7 is 0.5A, and thenThe current protection threshold of the circuit is 0.5A; it can be seen that by adjusting the resistance value of the seventh resistor R7, the current protection threshold of the circuit can be set, so that the protection threshold of the protection circuit can be controlled.
As shown in fig. 6, the first electronic switch Q1 may be a PMOS transistor, and the second electronic switch Q2 and the third electronic switch Q3 may be NMOS transistors.
When the battery does not generate overcurrent and undervoltage, only Q2 is ensured to be conducted and Q3 is ensured to be not conducted, and when the conducting voltage of the NMOS tube is known (usually, refer to a parameter manual of NMOS), the resistance values of the resistors R1, R2, R3 and R4 can be adjusted to realize the overvoltage and undervoltage protection. Assuming that the voltage of the battery is 12V for normal operation, in order to ensure that Q2 is conducted, the resistances of R1 and R2 need to satisfy:when the voltage drop of R1 is greater than or equal to the NMOS tube breakover voltage, the voltage difference between the voltage applied to the source of the NMOS tube Q2 and the voltage applied to the gate is greater than or equal to the NMOS tube breakover voltage, and the Q2 is conducted; to ensure that Q3 does not conduct, the resistances of R3 and R4 need to satisfy:less than the NMOS transistor turn-on voltage, i.e., such that the voltage drop across R3 is less than the turn-on voltage of NMOS transistor Q3, the voltage difference between the voltage applied to the source and the voltage applied to the gate of NMOS transistor Q3 is less than the NMOS transistor turn-on voltage, and thus Q3 is not turned on; thus, when Q2 is turned on, a current flows through the resistor R5, a voltage drop is generated across R5, and since the source and gate of the PMOS transistor Q4 are connected to both ends of R5, respectively, the voltage drop generated across R5 satisfies the requirement that the source and gate of Q4 are connected to each other If the voltage drop of the R5 meets the threshold voltage of Q4 conduction, Q4 is conducted, Q4 is conducted, and the discharge loop of the battery is connectedTherefore, the battery can normally supply power to the electronic product.
When overcurrent occurs, for example, the set overcurrent threshold is 1A, at this time, the voltage drop across the resistor R7 is equal to or greater than the on voltage of the PMOS transistor Q1, the voltage difference between the voltage across the source and the voltage across the gate of the PMOS transistor Q1 is equal to or greater than the on voltage of the PMOS transistor Q1, so that Q1 is turned on, after Q1 is turned on, the voltage division of R3 and R6 needs to make the voltage drop across R3 equal to or greater than the on voltage of the NMOS transistor Q3, so that Q3 is turned on, after Q3 is turned on, the current across R2 is increased, the voltage drop across R1 is reduced, so that Q1 is turned from on to off, after Q2 is turned off, there is no voltage drop across R5, then Q4 is turned off, so that the power supply path is cut off, and overcurrent protection. It is mentioned above that the voltage division of R3 and R6 is required to make the voltage drop of R3 equal to or greater than the turn-on voltage of NMOS transistor, and at the same time, the voltage division of R3 and R4 is required to make the voltage drop of R3 less than the turn-on voltage of NMOS transistor.
In order to adapt the circuit to batteries with different voltages, variable resistors may be used for R1 and R3.
It should be noted that the value of R7 is related to the threshold current of the protection circuit, assuming that the turn-on voltage of the PMOS transistor Q1 is a, if R7 is aIf the current at R7 is 1A, and the voltage drop at R7 is AV, the condition of Q1 conduction can be satisfied, and the current protection threshold of the circuit is 1A; if R7 is 2AIf the current protection threshold of the circuit is 0.5A, the circuit on R7 can meet the condition that Q1 is turned on; it can be seen that by adjusting the resistance value of the seventh resistor R7, the current protection threshold of the circuit can be set, so that the protection threshold of the protection circuit can be controlled.
In summary, the overcurrent and undervoltage protection circuit for the battery provided by the embodiment of the application can realize overcurrent and undervoltage protection of the battery through linkage coordination among the first electronic switch Q1, the second electronic switch Q2 and the third electronic switch Q3 and proper values of the first resistor, the second resistor and the seventh resistor. When the output current is greater than a set threshold value, the current on R7 is increased, so that Q1 is conducted, the voltage division of R3 and R6 is used for increasing the voltage drop on R3, then Q3 is conducted, so that the current on R2 is increased, the voltage drop on R1 is reduced, so that Q2 is cut off, and then a PMOS tube Q4 is cut off, so that the circuit automatically cuts off a power supply path to protect the battery from overcurrent damage; when the output voltage is lower than a set threshold value, the voltage drop on the R1 is reduced, the Q2 is cut off, the POMS tube Q4 is cut off, and the circuit can also automatically cut off a power supply path to protect the battery from undervoltage damage; compared with the overcurrent and undervoltage protection circuit in the prior art, the overcurrent and undervoltage protection circuit is realized only by the electronic switch and the resistor, is simple in design and low in cost, completely realizes protection by a hardware circuit, and is high in reaction speed.
It should be noted that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make variations, modifications, additions or substitutions within the spirit and scope of the present invention.
Claims (10)
1. A battery over-current and under-voltage protection circuit comprises a battery input end, an input ground, a battery output end, an output ground, a control circuit and an NMOS (N-channel metal oxide semiconductor) tube, wherein the battery input end is connected with the battery output end, a source electrode and a drain electrode of the NMOS tube are connected between the input ground and the output ground in series, the control circuit controls the on-off of the NMOS tube to realize the connection and the disconnection of a power supply loop, and the battery over-current and under-voltage protection circuit is characterized in that,
the control circuit comprises a first electronic switch, a second electronic switch, a third electronic switch, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor and a seventh resistor; wherein,
the first resistor and the second resistor are connected in series between the battery input end and the input ground; the third resistor and the fourth resistor are connected in series between the battery output end and the output ground;
the first end of the first electronic switch is connected with the source end of the NMOS tube, the second end of the first electronic switch is connected with the input ground, and the third end of the first electronic switch is connected with the first end of the sixth resistor; the first end of the sixth resistor is connected to the third end of the first electronic switch, and the second end of the sixth resistor is connected to the connection end of the third resistor and the fourth resistor;
the first end of the second electronic switch is connected to the connecting end of the first resistor and the second resistor, the second end of the second electronic switch is connected to the input end of the battery, and the third end of the second electronic switch is connected to the grid electrode of the NMOS tube;
the first end of the fifth resistor is connected with the third end of the second electronic switch, and the second end of the fifth resistor is connected with the source electrode of the NMOS tube; the seventh resistor is connected between the input ground and the source terminal of the NMOS tube in series;
and the first end of the third electronic switch is connected to the connecting end of the third resistor and the fourth resistor, the second end of the third electronic switch is connected to the output end of the battery, and the third end of the third electronic switch is connected to the connecting end of the first resistor and the second resistor.
2. The battery overcurrent undervoltage protection circuit of claim 1, wherein the first electronic switch is an NPN transistor having a base at a first end, an emitter at a second end, and a collector at a third end;
the second electronic switch and the third electronic switch are PNP triodes, wherein the first end is a base electrode, the second end is an emitting electrode, and the third end is a collector electrode.
3. The battery overcurrent undervoltage protection circuit of claim 1, wherein the first electronic switch is an NMOS transistor, and has a gate at a first end, a source at a second end, and a drain at a third end;
the second electronic switch and the third electronic switch are PMOS tubes, wherein the first end is a grid electrode, the second end is a source electrode, and the third end is a grid electrode.
4. The battery over-current and under-voltage protection circuit of claim 1, wherein a product of a resistance value of the seventh resistor and a current protection threshold is greater than or equal to a turn-on voltage of the first electronic switch.
5. The battery overcurrent and undervoltage protection circuit of claim 1, wherein the voltage division of the first resistor and the second resistor causes a voltage drop across the first resistor to be equal to or greater than a turn-on voltage of the second electronic switch, the voltage division of the third resistor and the fourth resistor causes a voltage drop across the third resistor to be less than a turn-on voltage of the third electronic switch, and the voltage division of the third resistor and the sixth resistor causes a voltage drop across the third resistor to be equal to or greater than a turn-on voltage of the third resistor switch.
6. A battery over-current and under-voltage protection circuit comprises a battery input end, an input ground, a battery output end, an output ground, a control circuit and a PMOS tube, wherein the input ground is connected with the output ground, a source electrode and a drain electrode of the PMOS tube are connected between the battery input end and the battery output end in series, the control circuit controls the conduction and the cut-off of the PMOS tube to realize the connection and the cut-off of a power supply path, and is characterized in that,
the control circuit comprises a first electronic switch, a second electronic switch, a third electronic switch, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor and a seventh resistor; wherein,
the first resistor and the second resistor are connected in series between the input ground and the battery input terminal; the third resistor and the fourth resistor are connected in series between the battery output end and the output ground;
the first end of the first electronic switch is connected with the source end of the PMOS tube, the second end of the first electronic switch is connected with the input end of the battery, and the third end of the first electronic switch is connected with the first end of the sixth resistor; the first end of the sixth resistor is connected to the third end of the first electronic switch, and the second end of the sixth resistor is connected to the connection end of the third resistor and the fourth resistor;
the first end of the second electronic switch is connected to the connecting end of the first resistor and the second resistor, the second end of the second electronic switch is connected to the input ground, and the third end of the second electronic switch is connected to the grid electrode of the PMOS tube;
the first end of the fifth resistor is connected with the third end of the second electronic switch, and the second end of the fifth resistor is connected with the source electrode of the PMOS tube; the seventh resistor is connected between the battery input end and the source end of the PMOS tube in series;
and the first end of the third electronic switch is connected to the connecting end of the third resistor and the fourth resistor, the second end of the third electronic switch is connected to the output ground, and the third end of the third electronic switch is connected to the connecting end of the first resistor and the second resistor.
7. The battery overcurrent undervoltage protection circuit of claim 6, wherein the first electronic switch is a PNP triode having a base at a first end, an emitter at a second end, and a collector at a third end;
the second electronic switch and the third electronic switch are NPN triodes, wherein the first end is a base electrode, the second end is an emitting electrode, and the third end is a collector electrode.
8. The battery overcurrent undervoltage protection circuit of claim 6, wherein the first electronic switch is a PMOS transistor, and has a gate at a first end, a source at a second end, and a drain at a third end;
the second electronic switch and the third electronic switch are NMOS tubes, wherein the first end is a grid electrode, the second end is a source electrode, and the third end is a grid electrode.
9. The battery over-current and under-voltage protection circuit of claim 6, wherein a product of a resistance value of the seventh resistor and a current protection threshold is greater than or equal to a turn-on voltage of the first electronic switch.
10. The battery overcurrent and undervoltage protection circuit of claim 6, wherein the voltage division of the first resistor and the second resistor causes a voltage drop across the first resistor to be equal to or greater than a turn-on voltage of the second electronic switch, the voltage division of the third resistor and the fourth resistor causes a voltage drop across the third resistor to be less than a turn-on voltage of the third electronic switch, and the voltage division of the third resistor and the sixth resistor causes a voltage drop across the third resistor to be equal to or greater than a turn-on voltage of the third resistor switch.
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| CN104037737B CN104037737B (en) | 2017-01-18 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN118630710A (en) * | 2024-08-09 | 2024-09-10 | 博瑞集信(西安)电子科技股份有限公司 | ESD protection circuit |
Citations (3)
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|---|---|---|---|---|
| US20120092801A1 (en) * | 2010-10-15 | 2012-04-19 | Hon Hai Precision Industry Co., Ltd. | Under-voltage protection circuit for battery |
| CN103683266A (en) * | 2013-12-20 | 2014-03-26 | 青岛歌尔声学科技有限公司 | Rechargeable battery protection circuit |
| CN203932985U (en) * | 2014-06-30 | 2014-11-05 | 青岛歌尔声学科技有限公司 | A kind of battery overcurrent under-voltage protecting circuit |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120092801A1 (en) * | 2010-10-15 | 2012-04-19 | Hon Hai Precision Industry Co., Ltd. | Under-voltage protection circuit for battery |
| CN103683266A (en) * | 2013-12-20 | 2014-03-26 | 青岛歌尔声学科技有限公司 | Rechargeable battery protection circuit |
| CN203932985U (en) * | 2014-06-30 | 2014-11-05 | 青岛歌尔声学科技有限公司 | A kind of battery overcurrent under-voltage protecting circuit |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118630710A (en) * | 2024-08-09 | 2024-09-10 | 博瑞集信(西安)电子科技股份有限公司 | ESD protection circuit |
| CN118630710B (en) * | 2024-08-09 | 2024-10-18 | 博瑞集信(西安)电子科技股份有限公司 | ESD protection circuit |
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