Battery charging detection circuit

Abstract

The utility model discloses a battery charging detection circuit, which is used for detecting a charger connected to a charging interface so as to conduct a charging switch on a charging circuit, the charging switch is positioned between the cathode of a rechargeable battery and the cathode of the charging interface, the cathode of the rechargeable battery is grounded, and the battery charging detection circuit comprises a first detection unit, the first detection unit comprises a triode, one end of an emitter junction of the triode is connected with the cathode of the rechargeable battery through a first diode and a first resistor in sequence, and the other end is connected with the cathode of the charging interface through a second diode; therefore, when the voltage of the negative electrode of the rechargeable battery is greater than the preset threshold value of the voltage of the negative electrode of the charging interface, a control signal for turning on the charging switch is output, so that the preset threshold value is smaller than the positive turn-on voltage of the np junction of the triode, a lower charger voltage activation threshold value is achieved, it is more reliably guaranteed that the rechargeable battery is fully charged, and a better charging effect is achieved.

Description

Technical Field

[0001] The utility model relates to battery charging, in particular to a battery charging detection circuit. Background Art

[0002] In recent years, with the emergence of new business models such as shared bicycles, food delivery, and unmanned logistics, the demand for electric vehicles has increased rapidly. Lead-acid batteries have the advantages of low price, simple maintenance, and high reliability, so they have been widely used in the field of electric vehicles. However, due to the disadvantages of large volume, heavy weight, and short life of lead-acid batteries, and with the continuous development of technology and the increasing demand for environmental protection and safety, a "lead-to-lithium" boom has been set off. "Lead-to-lithium" means replacing traditional lead-acid batteries with lithium batteries. Compared with lead-acid batteries, lithium batteries have better reaction speed and energy density, and can provide greater power and longer usage time.

[0003] At present, the chargers on the market are mainly classified into lead-acid battery chargers and lithium battery chargers. For the existing charger detection scheme, a relatively high charger voltage activation threshold is required (for example, the charger voltage needs to be higher than the battery voltage by 1.5V). When the battery pack is interrupted during charging, since the battery power is still relatively high and the voltage value remains large, the charger often cannot be detected again, resulting in the inability to activate charging and continue charging, and the phenomenon that the battery pack cannot be fully charged occurs.

[0004] Therefore, there is an urgent need for a battery charging detection circuit that can solve the above problems. Summary of the Utility Model

[0005] The purpose of the utility model is to provide a battery charging detection circuit, which realizes a lower charger voltage activation threshold, more reliably ensures that the charging battery is fully charged, and achieves a better charging effect.

[0006] To achieve the above purpose, the utility model provides a battery charging detection circuit for detecting a charger connected to a charging interface to turn on a charging switch on a charging line. The charging switch is located between the negative electrode of a charging battery and the negative electrode of the charging interface, and the negative electrode of the charging battery is grounded. The battery charging detection circuit includes a first detection unit, and the first detection unit includes a triode. One end of the emitter junction of the triode is connected to the negative electrode of the charging battery through a first diode and a first resistor in sequence, and the other end of the emitter junction is connected to the negative electrode of the charging interface through a second diode, so as to output a control signal for turning on the charging switch when the voltage difference between the negative electrode of the charging battery and the negative electrode of the charging interface is greater than or equal to a preset threshold, and the preset threshold is less than the forward conduction voltage of the np junction of the triode.

[0007] Preferably, the triode is an npn-type triode. The B pole of the triode is connected to the negative pole of the rechargeable battery through a first diode and a first resistor in sequence, and the E pole of the triode is connected to the negative pole of the charging interface through a second diode.

[0008] Preferably, the C pole of the triode is grounded through a third diode and a second resistor in sequence. The node between the third diode and the second resistor is the output terminal for the first detection unit to output a control signal for controlling the on / off of the charging switch.

[0009] Preferably, the positive pole of the first diode is also connected to a reference voltage through a third resistor, and the C pole of the triode is also connected to the reference voltage through a fourth resistor.

[0010] Preferably, the battery charging detection circuit further includes a second detection unit. The second detection unit detects whether the charger is connected to the charging interface, and controls the control signal to remain as a control signal for turning off the charging switch when the charger is unplugged from the charging interface.

[0011] Specifically, the second detection unit includes an opto-coupler switch and a fifth resistor. The primary side of the opto-coupler switch and the fifth resistor are connected in series between the positive and negative poles of the auxiliary signal of the charger. The secondary side of the opto-coupler switch outputs the auxiliary detection electrical signal. The positive pole of the auxiliary detection electrical signal is connected to the C pole of the triode, and the negative pole is connected to the E pole of the triode. The C pole of the triode is also connected to the reference voltage through a fourth resistor.

[0012] Preferably, the battery charging detection circuit further includes a power supply unit. The power supply unit converts the electrical signal of the rechargeable battery into a reference voltage and supplies power to the first detection unit.

[0013] Preferably, the battery charging detection circuit further includes a controller. The controller receives the control signal output by the first detection unit and controls the on / off of the charging switch according to the control signal.

[0014] Specifically, the battery charging detection circuit further includes a current sensor. The current sensor detects the charging current of the charging circuit. The controller also receives the charging current and the battery detection signal output by the rechargeable battery, and controls the charging switch to turn off when the charging current and the battery detection signal exceed the threshold. Among them, the rechargeable battery has a voltage acquisition circuit and a temperature detection circuit.

[0015] Preferably, the rechargeable battery is a lithium battery, the forward conduction voltage of the np junction is 0.6V, and the preset threshold is less than 0.6V.

[0016] Compared with the prior art, when the voltage of the charger is higher than the forward conduction voltage of the np junction of the rechargeable battery, the rechargeable switch of the present utility model can be turned on to start charging, and it can adapt to various chargers with a voltage difference greater than the current rechargeable battery. The function is more comprehensive and convenient. Not only is the charging detection safe and reliable, but also it has a lower charger voltage activation threshold, wide adaptability, simple control and low cost, and better charging effect. It solves the problem that the existing charging cannot be fully charged, and improves the charging detection effect, flexibility and convenience. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the circuit diagram of the battery charging detection circuit of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] To describe in detail the technical content, structural features, achieved objectives and effects of the present utility model, the following is described in detail in conjunction with the embodiments and with reference to the drawings.

[0019] Refer to Figure 1 , the present utility model discloses a battery charging detection circuit 100 for detecting whether the charger 200 connected to the charging interface 400 is matched, and turning on the charging switch 50 on the charging line when the charger 200 is matched. The charging switch 50 is located between the negative electrode B- of the rechargeable battery 300 and the negative electrode C- of the charging interface 400, and the negative electrode of the rechargeable battery 300 is grounded. The battery charging detection circuit 100 includes a first detection unit 30, and the first detection unit 30 includes a triode Q1. One end of the emitter junction (the np junction between the B pole and the E pole) of the triode Q1 is sequentially connected to the negative electrode of the rechargeable battery 300 through a first diode D1 and a first resistor R1, and the other end of the emitter junction is connected to the negative electrode C- of the charging interface 400 through a second diode D2. When the voltage difference obtained by subtracting the negative electrode of the charging interface 400 from the negative electrode of the rechargeable battery 300 is greater than or equal to a preset threshold, it is detected that the charger 200 is matched and the rechargeable battery 300 is not fully charged, so as to output a control signal INT for turning on the charging switch 50, so that the preset threshold Vth is less than the forward conduction voltage of the np junction of the triode Q1. In this embodiment, the rechargeable battery 300 is a lithium battery, and the forward conduction voltage of the np junction is 0.6V, so that the preset threshold is less than 0.6V.

[0020] In this embodiment, the triode Q1 is an npn-type triode. The B pole of the triode Q1 is sequentially connected to the negative pole B- of the charging battery 300 through a first diode D1 and a first resistor R1. The E pole of the triode Q1 is connected to the negative pole of the charging interface 400 through a second diode. When the voltage difference obtained by subtracting the negative pole of the charging interface 400 from the negative pole of the charging battery 300 is greater than or equal to a preset threshold, a control signal INT for turning on the charging switch 50 is output from the C pole of the triode Q1.

[0021] Specifically, the C pole of the triode Q1 is sequentially grounded through a third diode D3 and a second resistor R2. The node between the third diode D3 and the second resistor R2 is the output terminal of the first detection unit 30 for outputting a control signal INT for controlling the on / off of the charging switch 50. The positive pole of the first diode D1 is also connected to a reference voltage VDD through a third resistor R3. The C pole of the triode Q1 is also connected to the reference voltage VDD through a fourth resistor R4.

[0022] Preferably, the battery charging detection circuit 100 further includes a second detection unit 40. The second detection unit 40 detects whether the charger 200 is connected to the charging interface 400, and controls the control signal to remain as a control signal for turning off the charging switch 50 when the charger 200 is unplugged from the charging interface 400.

[0023] In this embodiment, the second detection unit 40 includes an optocoupler switch U1 and a fifth resistor R5. The primary side of the optocoupler switch U1 and the fifth resistor R5 are connected in series between the positive and negative auxiliary signals A+ / A- of the charger 200. The secondary side of the optocoupler switch U1 outputs the auxiliary detection electrical signal. The positive pole of the auxiliary detection electrical signal is connected to the C pole of the triode Q1, and the negative pole is connected to the E pole of the triode Q1. The C pole of the triode Q1 is also connected to the reference voltage VDD through a fourth resistor R4.

[0024] Among them, the positive and negative auxiliary signals A+ / A- can be replaced by differential signals with communication (CAN or RS485).

[0025] Among them, the charger 200 can be a charger that directly outputs voltage, or a charger with a handshake protocol (for example, A+ / A- is a communication differential signal), or a charger with an auxiliary power supply for charging activation (such as A+ / A- outputs a 12V auxiliary power supply).

[0026] Preferably, the battery charging detection circuit 100 further includes a power supply unit 10, a controller 20, and a current sensor 60. The power supply unit 10 converts the electrical signal of the rechargeable battery 300 into a reference voltage VDD and supplies power to the first detection unit 30. The controller receives the control signal INT output by the first detection unit 30 and controls the on / off of the charging switch 50 according to the control signal INT. The current sensor 60 detects the charging current I of the charging circuit. The controller 20 also receives the charging current I and the battery detection signal output by the rechargeable battery 300, and controls the charging switch 50 to disconnect when the charging current and the battery detection signal exceed the threshold. Among them, the rechargeable battery 300 has a voltage acquisition circuit for acquiring the voltage U of the rechargeable battery 300 and a temperature detection circuit for acquiring the temperature T of the rechargeable battery 300.

[0027] Among them, the power supply unit 10 generally takes a BCUK circuit, an LDO circuit, or a flyback circuit as the core to provide a suitable operating voltage for relevant units of the system, which is a well-known technology in the industry and will not be elaborated here. The current sensor 60 is used to collect the charging current, generally a shunt or a Hall current sensor, which is a well-known technology in the industry and will not be elaborated here.

[0028] The controller 20 takes an MCU and embedded software as the core, and includes necessary peripheral devices such as a reference source, a crystal oscillator, a memory, a logic circuit, and a buzzer, etc., which is a well-known technology in the industry and will not be elaborated here. The charging switch 50 controls the charging, generally a MOS transistor switch or a relay switch, which is a well-known technology in the industry and will not be elaborated here.

[0029] Reference Figure 1 , taking the rated voltage of the rechargeable battery 300 as 12V as an example, the working principle of the battery charging detection circuit 100 of the present invention is described as follows:

[0030] (1) In the initial state, when the charger 300 is not connected, the detection signals of the first detection unit 30 and the second detection unit 40 are in the off state, that is, the triode Q1 and the opto-coupled switch U1 are both in the cut-off state at this time. The control signal INT forms a shunt circuit through R5 (such as 2MΩ) / R4 (such as 100KΩ) / D2 (such as BAV21W) to be at a high level. In this embodiment, when the control signal INT is at a high level, the charging switch 50 is controlled to be in the off state. Of course, it can also be set conversely that when the control signal INT is at a low level, the charging switch 50 is controlled to be in the off state. At this time, when the detection signals of the first detection unit 30 and the second detection unit 40 are in the off state, the control signal INT is at a low level to control the charging switch 50 to be in the off state.

[0031] (2) When the charger 200 is connected to the charging interface 400, since the charger 200 and the rechargeable battery 300 share the same positive electrode, the voltage difference V1 between the charger 200 and the rechargeable battery 300 is equivalent to the potential difference between the negative electrode B- of the rechargeable battery and the negative electrode C- of the charger 200. When V1 is greater than or equal to Vth (a preset threshold), the triode Q1 (MMBT5551 can be selected) conducts (taking the voltage Vbe as 0.6V as an example), thereby controlling the signal INT to flip to a low level, triggering the controller 20 to generate an interrupt signal for processing. For example, CHG is output as a high level, and the controller 20 controls the charging switch 50 to conduct for charging. The reference voltage VDD (such as 3.3V) is divided by the first resistor R1 (such as 47KΩ) and the third resistor R3 (such as 510KΩ) to obtain VF. The first diode D1 and the second diode D2 are Schottky diodes of the same model (such as BAV21W), symmetrically eliminating the reverse flow voltage drop. Thus, the calculation formula is Vth = Vbe - VF, where Since VF is greater than 0V, Vth < Vbe (for example, 0.6V), achieving a lower charger voltage activation threshold, more reliably ensuring that the rechargeable battery is fully charged, and achieving a better charging effect.

[0032] (3) After the charging switch 50 conducts, the charger 200 can charge the rechargeable battery 300, and the current sensor 60 monitors the charging current I. At the same time, the controller 20 synchronously monitors the state of the rechargeable battery 300, such as the single-cell voltage U and the temperature T. When the charging conditions are not met, it controls the CHG signal to output a low level to turn off the charging switch 50 and stop charging. When the controller 20 monitors that the charging current I is greater than the preset over-current protection value for charging (usually 1.5 times the rated charging current), it controls CHG to output a low level to turn off the charging switch 50 and stop charging after a delay (such as 1 second). Through the above method, more lithium battery chargers can be applied, preventing safety risks such as voltage mismatch of lithium battery chargers or excessive charging current when using lead-acid battery chargers mixedly, and ensuring the safety of charging.

[0033] (4) When the controller 20 monitors that the single-cell voltage of the rechargeable battery 300 reaches the full charge threshold or the charging current CC is continuously less than the preset current value (such as 1A) for a period of time (such as 10 seconds), it is calibrated that the rechargeable battery 300 is fully charged, and it controls CHG to output a low level to turn off the charging switch 50 and stop charging.

[0034] (5) After charging stops, if the controller 20 detects that the control signal INT is still at a low level, it is determined that the charger 200 has not been removed. The second detection unit 40 can detect the auxiliary power signal A+ / A− or the communication (preferably CAN or RS485) differential signal. When the charger 200 has not been removed, the high-level signal output by A+ / A− forms a loop through the fifth resistor R5 (e.g., 1KΩ) and the optocoupler switch U1, thereby turning on the optocoupler switch U1, and thus the control signal INT remains at a low level.

[0035] (6) After the charger 200 is removed, the controller 20 detects that the control signal INT is at a high level.

[0036] Compared with the prior art, the present utility model can turn on the charging switch 50 to start charging when the voltage of the charger 200 is higher than the forward conduction voltage of the np junction of the triode Q1, and can adapt to chargers 200 with a voltage difference greater than that of the current charging battery 300 of various types. The function is more comprehensive and convenient. Not only is the charging detection safe and reliable, but also it has a lower charger 200 voltage activation threshold, wide adaptability, simple control and low cost, and better charging effect. It solves the problem that the existing charging cannot be fully charged, and improves the charging detection effect, flexibility and convenience.

[0037] The foregoing disclosure is only the preferred embodiment of the present utility model, and of course it cannot be used to limit the scope of rights of the present utility model. Therefore, equivalent changes made according to the scope of the patent application of the present utility model still fall within the scope covered by the present utility model.

Claims

1. A battery charging detection circuit for detecting a charger connected to a charging interface to turn on a charging switch on a charging line, characterized in that: The charging switch is located between the negative electrode of the charging battery and the negative electrode of the charging interface, and the negative electrode of the charging battery is grounded. The battery charging detection circuit includes a first detection unit, and the first detection unit includes a triode. One end of the emitter junction of the triode is connected to the negative electrode of the charging battery through a first diode and a first resistor in sequence, and the other end of the emitter junction is connected to the negative electrode of the charging interface through a second diode, so as to output a control signal for turning on the charging switch when the voltage difference between the negative electrode of the charging battery and the negative electrode of the charging interface is greater than or equal to a preset threshold, and the preset threshold is less than the forward conduction voltage of the np junction of the triode.

2. The battery charging detection circuit according to claim 1, wherein: The triode is an npn-type triode. The B pole of the triode is connected to the negative electrode of the charging battery through a first diode and a first resistor in sequence, and the E pole of the triode is connected to the negative electrode of the charging interface through a second diode.

3. The battery charging detection circuit according to claim 1, wherein: The C pole of the triode is grounded through a third diode and a second resistor in sequence, and the node between the third diode and the second resistor is the output end of the first detection unit for outputting a control signal for controlling the on-off of the charging switch.

4. The battery charging detection circuit according to claim 1, wherein: The positive electrode of the first diode is also connected to a reference voltage through a third resistor, and the C pole of the triode is also connected to the reference voltage through a fourth resistor.

5. The battery charging detection circuit according to claim 1, wherein: It further includes a second detection unit. The second detection unit detects whether the charger is connected to the charging interface, and controls the control signal to remain as a control signal for turning off the charging switch when the charger is unplugged from the charging interface.

6. The battery charging detection circuit according to claim 5, wherein: The second detection unit includes an opto-coupler switch and a fifth resistor. The primary side of the opto-coupler switch and the fifth resistor are connected in series between the positive and negative auxiliary signals of the charger. The secondary side of the opto-coupler switch outputs the auxiliary detection electrical signal. The positive pole of the auxiliary detection electrical signal is connected to the C pole of the triode, and the negative pole is connected to the E pole of the triode. The C pole of the triode is also connected to the reference voltage through a fourth resistor.

7. The battery charging detection circuit according to claim 1, wherein: It further includes a power supply unit. The power supply unit converts the electrical signal of the charging battery into a reference voltage and supplies power to the first detection unit.

8. The battery charging detection circuit according to claim 1, characterized in that: It further includes a controller. The controller receives the control signal output by the first detection unit and controls the on-off of the charging switch according to the control signal.

9. The battery charging detection circuit according to claim 8, characterized in that: It further includes a current sensor. The current sensor detects the charging current of the charging circuit. The controller also receives the charging current and the battery detection signal output by the charging battery, and controls the charging switch to turn off when the charging current and the battery detection signal exceed the threshold.

10. The battery charging detection circuit according to claim 1, wherein: The charging battery is a lithium battery, and the forward conduction voltage of the np junction is 0.6V.

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