Charging protection circuit and vehicle

Abstract

The present disclosure relates to the field of charging technology, and in particular to a charging protection circuit and a vehicle, wherein the charging protection circuit comprises: a charging switch (K), wherein an input end (W1) of the charging switch (K) is suitable for connecting a charging power source (BUS), an output end (W2) of the charging switch is suitable for connecting a battery (BAT), and the charging switch is used to turn on or off the charging of the battery (BAT) by the charging power source (BUS); and a switch control circuit (S1), wherein a first control end (P3) of the switch control circuit (S1) is coupled to a second control end (W3) of the charging switch (K), and the switch control circuit (S1) is used to keep the charging switch (K) turned on when the voltage of the battery (BAT) is less than a voltage threshold, and to turn off the charging switch (K) when the voltage of the battery (BAT) is greater than or equal to a voltage threshold, and the voltage threshold is greater than the voltage of the charging power source (BUS). The charging protection circuit provided by the present solution adopts a pure hardware structure and has strong stability.

Description

Technical Field

[0001] The present disclosure relates to the field of charging technology, and in particular, to a charging protection circuit and a vehicle. Background Art

[0002] At present, when charging the battery system of electric vehicles, the battery pack voltage may be unstable, resulting in the battery voltage being higher than the charging voltage. This will not only increase energy loss and reduce charging efficiency, but may also cause voltage backflow to damage the charging circuit. Therefore, how to protect the charging circuit from backflow is a technical problem that needs to be solved urgently. Summary of the invention

[0003] The purpose of the present disclosure is to provide a charging protection circuit and a vehicle, which can maintain normal charging and prevent the battery from back-feeding charging power when the voltage of the battery is less than a voltage threshold and the voltage threshold is greater than the voltage of the charging power source.

[0004] In order to achieve the above object, according to a first aspect of the present disclosure, a charging protection circuit is provided, comprising:

[0005] A charging switch K, wherein an input terminal W1 of the charging switch K is suitable for connecting to a charging power source BUS, and an output terminal W2 of the charging switch is suitable for connecting to a battery BAT, and the charging switch is used to turn on or off charging of the battery BAT by the charging power source BUS;

[0006] A switch control circuit S1, wherein a first control terminal P3 of the switch control circuit S1 is coupled to a second control terminal W3 of the charging switch K. The switch control circuit S1 is used to maintain the charging switch K turned on and prevent the battery BAT from back-feeding the charging power supply BUS when the voltage of the battery BAT is less than a voltage threshold, and to disconnect the charging switch K when the voltage of the battery BAT is greater than or equal to the voltage threshold, and the voltage threshold is greater than the voltage of the charging power supply BUS.

[0007] Optionally, the charging protection circuit further includes:

[0008] A first terminal D1 for connecting to an auxiliary power source U1, a second terminal D2 for connecting to a charging power source BUS, and a third terminal D3 for connecting to a battery BAT, wherein the voltage of the auxiliary power source U1 is greater than the voltage of the charging power source BUS;

[0009] The input terminal W1 of the charging switch K is used to connect the second terminal D2, and the output terminal W2 of the charging switch is used to connect the third terminal D3;

[0010] The first input terminal P1 of the switch control circuit S1 is connected to the first terminal D1 , the first output terminal P2 of the switch control circuit is connected to the third terminal D3 , and the second output terminal P4 of the switch control circuit S1 is connected to the input terminal W1 .

[0011] Optionally, the switch control circuit S1 includes a first transistor Q1 and a second transistor Q2, the emitter of the first transistor Q1 is connected to the collector of the second transistor Q2, and a common end of the two serves as the first input end P1, the collector of the first transistor Q1 serves as the first output end P2, the collector of the second transistor Q2 serves as the first control end P3, and the emitter of the second transistor Q2 serves as the second output end P4;

[0012] The emitter of the first transistor Q1 is connected to the base of the first transistor Q1 and the base of the second transistor Q2 respectively.

[0013] Optionally, the first transistor Q1 and the second transistor Q2 are the same, and the voltage threshold is the sum of the voltage of the charging power source BUS and a fine-tuning threshold.

[0014] Optionally, the voltage of the second control terminal W3 of the charging switch is consistent with the voltage of the collector of the second transistor Q2.

[0015] Optionally, the charging protection circuit further includes a voltage follower circuit S2, wherein the voltage follower circuit S2 includes a second input terminal T1 connected to the first terminal D1, a third output terminal T2 connected to the second control terminal W3, and a voltage follower terminal T3 connected to the collector of the second transistor Q2;

[0016] The voltage follower circuit S2 is used to keep the voltage of the second control terminal W3 of the charging switch consistent with the voltage of the collector of the second transistor Q2.

[0017] Optionally, the voltage follower circuit S2 includes a third transistor Q3 and a fourth transistor Q4, the base of the third transistor Q3 is connected to the base of the fourth transistor Q4, and the common end of the bases of the two serves as the voltage follower end T3, the collector of the third transistor Q3 serves as the second input end T1, and the collector of the fourth transistor Q4 serves as the third output end T2.

[0018] Optionally, the charging switch K is a MOS tube, the source of the MOS tube serves as the input terminal W1, the drain of the MOS tube serves as the output terminal W2, and the gate of the MOS tube serves as the second control terminal W3.

[0019] Optionally, the charging protection circuit also includes a first resistor R1 and / or a second resistor R2, one end of the first resistor R1 is connected to the first end D1, the other end of the first resistor R1 is connected to the emitter of the first transistor Q1, one end of the second resistor R2 is connected to the first end D1, and the other end of the second resistor R2 is connected to the collector of the second transistor Q2.

[0020] Optionally, the voltage follower circuit S2 further includes a third resistor R3, one end of the third resistor R3 is connected to the first end D1, and the other end of the third resistor R3 is connected to the collector of the third transistor Q3.

[0021] Optionally, the charging protection circuit further includes a capacitor C, one end of the capacitor C is connected to the auxiliary power supply U1, and the other end of the capacitor C is connected to the charging power supply BUS.

[0022] According to a second aspect of the present disclosure, a vehicle is provided, comprising a battery and the above-mentioned charging protection circuit provided by the present disclosure.

[0023] Through the above technical solution, through the pure hardware charging protection circuit, when the voltage of the battery BAT is less than the voltage threshold, and the voltage threshold is greater than the voltage of the charging power supply BUS, the charging switch K is maintained on and the battery BAT is prevented from back-feeding the charging power supply BUS, and when the voltage of the battery BAT is greater than or equal to the voltage threshold, the charging switch K is disconnected. The pure hardware circuit design requires fewer devices, which improves the economy and reliability of the charging protection circuit, and does not require software logic control, and does not require the introduction of chips and other controlled switching devices, so that the overall space volume of the charging protection circuit is small, and there is no need to consider voltage conversion and electrical isolation. It can be used in more environments and can be applied to a variety of low-voltage charging circuits. In addition, by maintaining the charging switch K on when the voltage of the battery BAT is less than the voltage threshold, and the voltage threshold is greater than the voltage of the charging power supply, the battery charging is prevented from back-feeding, and the corresponding threshold is reserved to ensure the normal battery charging function.

[0024] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0026] Figure 1 A charging protection circuit in the prior art is shown according to an exemplary embodiment.

[0027] Figure 2is a circuit diagram of a charging protection circuit according to an exemplary embodiment.

[0028] Figure 3 is a circuit diagram of a charging protection circuit according to an exemplary embodiment.

[0029] Figure 4 is a circuit diagram of a charging protection circuit according to an exemplary embodiment.

[0030] Figure 5 is a schematic diagram showing the conduction characteristics of a transistor according to an exemplary embodiment.

[0031] Figure 6 is a circuit diagram of a charging protection circuit according to an exemplary embodiment.

[0032] Figure 7 is a circuit diagram of a charging protection circuit according to an exemplary embodiment.

[0033] Figure 8 is another circuit diagram of a charging protection circuit according to an exemplary embodiment.

[0034] Description of Reference Numerals

[0035] U1: auxiliary power supply; D1: first terminal; BUS: charging power supply; BUS+: positive pole of charging power supply; BUS-: negative pole of charging power supply; D2: second terminal; BAT: battery; BAT+: positive pole of battery; BAT-: negative pole of battery; D3: third terminal; K: charging switch; S1: switch control circuit; W1: input terminal; W2: output terminal; P1: first input terminal; P2: first output terminal; P3: first control terminal; P4: second output terminal; W3: second control terminal; Q1: first transistor; Q2: second transistor; S2: voltage follower circuit; T1: second input terminal; T2: third output terminal; T3: voltage follower terminal; Q3: third transistor; Q4: fourth transistor; R1: first resistor; R2: second resistor; R3: third resistor; C: capacitor; TP1: first detection terminal; TP2: second detection terminal; TP3: third detection terminal. DETAILED DESCRIPTION

[0036] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0037] As mentioned in the background technology, currently, when the battery system of an electric vehicle is being charged, the battery pack voltage may become unstable, causing the battery voltage to be higher than the charging voltage, which in turn causes voltage backflow and damages the charging circuit.

[0038] For example, Figure 1 As shown, in the prior art, the charging circuit is protected against voltage backflow by adopting a combination of software and hardware, and the corresponding components are controlled by a comparator and a switch control circuit to achieve backflow protection for the entire circuit. It is composed of multiple modules, has high cost, and is complex in design. In addition, due to the large number of devices, there are problems with the logic coordination of software and hardware, and the reliability is not high. There is also the problem of voltage conversion control of switch elements that needs to be considered.

[0039] Figure 2 is a circuit diagram of a charging protection circuit according to an exemplary embodiment. Figure 2 As shown, the charging protection circuit includes:

[0040] A charging switch K, wherein an input end W1 of the charging switch K is suitable for connecting to a charging power source BUS, an output end W2 of the charging switch is suitable for connecting to a battery BAT, and the charging switch is used to turn on or off charging of the battery BAT by the charging power source BUS;

[0041] The switch control circuit S1 has a first control terminal P3 coupled to a second control terminal W3 of the charging switch K. The switch control circuit S1 is used to maintain the charging switch K turned on and prevent the battery BAT from back-feeding the charging power supply BUS when the voltage of the battery BAT is less than a voltage threshold, and to disconnect the charging switch K when the voltage of the battery BAT is greater than or equal to a voltage threshold. The voltage threshold is greater than the voltage of the charging power supply BUS.

[0042] In some embodiments, the switch control circuit S1 is a pure hardware circuit, the charging switch is a hardware device, and the charging protection circuit is a pure hardware circuit.

[0043] The present disclosure uses a pure hardware charging protection circuit, so that when the voltage of the battery BAT is less than the voltage threshold, and the voltage threshold is greater than the voltage of the charging power supply BUS, the charging switch K is maintained on and the battery BAT is prevented from back-feeding the charging power supply BUS, and when the voltage of the battery BAT is greater than or equal to the voltage threshold, the charging switch K is disconnected. The pure hardware circuit design requires fewer devices, which improves the economy and reliability of the charging protection circuit, and does not require software logic control, and does not require the introduction of chips and other controlled switching devices, so that the overall space volume of the charging protection circuit is small, and there is no need to consider voltage conversion and electrical isolation. It can be used in more environments and can be applied to a variety of low-voltage charging circuits. In addition, by maintaining the charging switch K on when the voltage of the battery BAT is less than the voltage threshold, and the voltage threshold is greater than the voltage of the charging power supply, the battery charging is prevented from back-feeding, and the corresponding threshold is reserved to ensure the normal battery charging function.

[0044] Figure 3 is a circuit diagram of a charging protection circuit according to an exemplary embodiment. Figure 3 As shown, Figure 2 The charging protection circuit also includes:

[0045] A first terminal D1 for connecting to an auxiliary power source U1, a second terminal D2 for connecting to a charging power source BUS, and a third terminal D3 for connecting to a battery BAT, wherein the voltage of the auxiliary power source U1 is greater than the voltage of the charging power source BUS;

[0046] The input terminal W1 of the charging switch K is used to connect to the second terminal D2, and the output terminal W2 of the charging switch is used to connect to the third terminal D3;

[0047] The first input terminal P1 of the switch control circuit S1 is connected to the first terminal D1 , the first output terminal P2 of the switch control circuit is connected to the third terminal D3 , and the second output terminal P4 of the switch control circuit S1 is connected to the input terminal W1 .

[0048] In some embodiments, the difference between the voltage of the auxiliary power supply U1 and the voltage of the charging power supply BUS is a preset value. In a possible implementation, the preset value is greater than the voltage difference for turning on the charging switch K, for example, greater than the voltage difference between the input terminal W1 and the second control terminal W3 of the charging switch K. In another possible implementation, the preset value can be specifically set according to actual needs, for example, the preset value can be 15V.

[0049] like Figure 3 As shown, the charging power supply BUS includes a positive electrode BUS+ and a negative electrode BUS-, and the negative electrode BUS- is grounded. Therefore, the difference between the voltage of the auxiliary power supply U1 and the voltage of the charging power supply BUS, that is, the difference between the voltage of the positive electrode of the auxiliary power supply U1 and the voltage of the positive electrode BUS+ of the charging power supply BUS.

[0050] In some embodiments, the voltage threshold is the sum of the voltage of the charging power source BUS and the fine-tuning threshold. The fine-tuning threshold can be specifically set according to actual conditions. For example, the fine-tuning threshold can be 0.02V.

[0051] Figure 4 is another circuit diagram of a charging protection circuit according to an exemplary embodiment. Figure 4 As shown, Figure 4 In such Figure 3 The structure of the switch control circuit is described based on Figure 4As shown, the switch control circuit S1 includes a first transistor Q1 and a second transistor Q2, the emitter of the first transistor Q1 is connected to the collector of the second transistor Q2, and the common end of the two serves as the first input end P1, the collector of the first transistor Q1 serves as the first output end P2, the collector of the second transistor Q2 serves as the first control end P3, and the emitter of the second transistor Q2 serves as the second output end P4; the emitter of the first transistor Q1 is connected to the base of the first transistor Q1 and the base of the second transistor Q2, respectively.

[0052] In some embodiments, the first transistor Q1 and the second transistor Q2 are the same. In a possible implementation, the first transistor Q1 and the second transistor Q2 being the same may include having the same model, and the same model may be understood as having the same parameters of the transistors.

[0053] In a possible implementation, the fine-tuning threshold may be obtained by the conduction characteristics of the first transistor Q1 and the second transistor Q2. In some embodiments, the fine-tuning threshold is the difference between a first inter-electrode voltage between the base and the collector of the first transistor Q1 and a second inter-electrode voltage between the base and the emitter of the second transistor Q2.

[0054] In order to explain the conduction characteristics of the transistor more clearly, the following will take the NPN transistor as an example and combine Figure 5 The conduction characteristics of the triode are explained. In order to obtain a higher emission efficiency, the high majority carrier concentration in the emitter region will cause a large number of electrons to diffuse from the emitter region to the base region. The base region is thin and has a low majority carrier concentration, so that the few electrons that diffuse into the base region recombine with holes. After a part of the electrons emitted by the emitter are diverted by the base control, the rest are emitted from the collector. To achieve the above functions, such as Figure 5 As shown in the figure, in the manufacturing process of the transistor, the small area on the left, i.e. the emitter, is doped with high-concentration N-type, the extremely small area in the middle, i.e. the base, is doped with normal-concentration P-type, and the wider area on the right, i.e. the collector, is doped with low-concentration N-type. It can be seen that there is a significant difference in the concentration of the majority carrier doping on both sides of the emitter and collector depletion layers of the transistor. When the concentration of the majority carrier doping increases, the turn-on voltage will increase accordingly, which causes the turn-on voltage of the transistor to be less than the turn-on voltage.

[0055] For example, by connecting the base and emitter of the first transistor Q1, the first transistor Q1 can be used as a diode. According to the conduction characteristics of the transistor, the collector with a lower concentration in the transistor is utilized at this time. For a single transistor, such as the first transistor Q1 or the second transistor Q2, the conduction voltage of the transistor is less than the turn-on voltage, the conduction voltage is the inter-electrode voltage between the base and the collector, and the turn-on voltage is the voltage between the base and the emitter.

[0056] For the same first transistor Q1 and second transistor Q2, the conduction voltage U of the first transistor Q1 after conduction is BC Less than the turn-on voltage U of the second transistor Q2 BE , that is, the first inter-electrode voltage U between the base and collector of the first transistor Q1 BC is less than the second inter-electrode voltage U between the base and emitter of the second transistor Q2 BE , the first inter-electrode voltage U BC The second inter-electrode voltage U BE There is a difference between them, and the difference can be used as a fine-tuning threshold. The range of the fine-tuning threshold is [0.01, 0.03]. For example, the fine-tuning threshold can be the aforementioned 0.02V.

[0057] The switch control circuit of the disclosed embodiment can obtain a fine-tuning threshold through its own first transistor Q1 and second transistor Q2, utilizing the conduction characteristics of the transistor, that is, the difference in the multi-carrier doping concentrations of the emitter, base and collector in the transistor manufacturing process, resulting in a slight voltage difference between the conduction voltages of the two PN junctions of the transistor. By using the fine-tuning threshold, the charging anti-backflow function of the circuit is realized and the fine-tuning threshold is reserved to ensure normal charging of the battery.

[0058] In some embodiments, the voltage of the second control terminal W3 of the charging switch is consistent with the voltage of the collector of the second triode Q2. In a possible implementation, the voltage of the collector of the second triode Q2 can be adjusted by controlling the on or off of the first triode Q1 and the second triode Q2 in the switch control circuit S1, thereby adjusting the voltage of the second control terminal W3 to achieve the on or off of the charging switch K.

[0059] For example, the following will be combined with Figure 4 The working principle of the charging protection circuit disclosed in the present invention is described. Figure 4 It can be seen that the voltage of the emitter of the second transistor Q2 is the same as the voltage of the charging power supply BUS, so the voltage of the base of the second transistor Q2 determines whether the second transistor Q2 can be turned on. The base and emitter of the first transistor Q1 are connected, the voltage of the base of the first transistor Q1 is greater than the voltage of its collector, and the inter-electrode voltage between its base and collector is less than the inter-electrode voltage between the base and collector when the second transistor Q2 is normally turned on. Through this characteristic, the voltage of the battery BAT is compared with the voltage of the charging power supply BUS to control the conduction or disconnection of the second transistor Q2.

[0060] When the second transistor Q2 in the switch control circuit S1 is controlled to be turned on, the voltage of the collector of the second transistor Q2 is pulled to the voltage of the charging power supply BUS. Since the voltage of the second control terminal W3 is consistent with the voltage of the collector of the second transistor Q2, and the voltage of the input terminal W1 of the charging switch K is the voltage of the charging voltage BUS, there is almost no voltage difference between the second control terminal W3 and the input terminal W1 of the charging switch K, and the charging switch K is disconnected, thereby disconnecting the charging of the battery BAT by the charging power supply BUS.

[0061] When the second transistor Q2 is controlled to be disconnected, the voltage of the collector of the second transistor Q2 is pulled to the voltage of the auxiliary power supply U1, and the voltage of the auxiliary power supply U1 is greater than the voltage of the charging power supply BUS. At this time, the voltage of the second control terminal W3 of the charging switch K is greater than the voltage of the input terminal W1, and the charging switch K is turned on, thereby turning on the charging power supply BUS to charge the battery BAT.

[0062] In a possible implementation, the charging switch K is a MOS tube, the source of the MOS tube serves as the input terminal W1, the drain of the MOS tube serves as the output terminal W2, and the gate of the MOS tube serves as the second control terminal W3. For the principle of turning on or off the MOS tube, please refer to Figure 4 The on / off principle of the charging switch K in the schematic diagram will not be described in detail here.

[0063] In some embodiments, the MOS tube can be selected with a conduction impedance less than a preset threshold, and the conduction loss can be reduced by selecting a MOS tube with a smaller conduction impedance. At the same time, based on the anti-backfeed characteristic, there is no need to consider the impact of the switching frequency on the circuit.

[0064] The present disclosure selects a MOS tube as a charging switch, which can not only realize anti-backflow protection by controlling the conduction or disconnection of the MOS tube, but also realize a second layer of anti-backflow protection through the body diode of the MOS tube. For example, when the circuit cannot work normally due to some reasons, since the body diode is unidirectionally conducted, the body diode needs to be broken down to cause the battery voltage to backflow to the power supply voltage, thus realizing double anti-backflow protection.

[0065] The charging protection circuit of the present disclosure includes multiple working conditions, for example, including working condition 1 where the voltage of the charging power source BUS is greater than the voltage of the battery BAT, working condition 2 where the voltage of the battery BAT is greater than or equal to the voltage of the charging power source BUS and less than the voltage threshold, and working condition 3 where the voltage of the battery BAT is greater than or equal to the voltage threshold. Figure 4 The working principle of the charging protection circuit of the present invention in working conditions 1-3 is explained.

[0066] Working condition 1, when the voltage of the charging power supply BUS is greater than the voltage of the battery BAT, it is assumed that the voltage of the charging power supply BUS is 12V, the voltage of the battery BAT is 11V, and the voltage difference between the voltage of the auxiliary power supply U1 and the voltage of the charging power supply BUS is 15V. Figure 4 As shown, the collector of the first transistor Q1 is connected to the positive electrode BAT+ of the battery BAT, the voltage of the collector of the first transistor Q1 is also 11V, the base and emitter of the first transistor Q1 are short-circuited, and its function is analogous to a diode, and due to the transistor manufacturing process, the inter-electrode voltage between the base and collector of the first transistor Q1 is less than the inter-electrode voltage between the base and emitter of the first transistor Q1, assuming that the inter-electrode voltage between the base and collector of the first transistor Q1 is 0.68V. At this time, since the voltage of the base and emitter of the first transistor Q1 is the same and connected to the voltage end of the auxiliary power supply U1, the voltage of the base and emitter of the first transistor Q1 is significantly higher than the voltage of its collector, and the diode is turned on, that is, the first transistor Q1 is turned on. And because the collector of the first transistor Q1 is connected to the positive electrode BAT+ of the battery BAT, the voltage of the collector of the first transistor Q1 is 11V, and the voltage between the base and the emitter is 11+0.68V=11.68V.

[0067] The emitter of the second transistor Q2 is connected to the positive electrode BUS+ of the charging power supply BUS, and the voltage of the emitter of the second transistor Q2 is the voltage of the charging power supply BUS, 12V. The base of the second transistor Q2 is connected to the base and emitter of the first transistor Q1, and the voltage of the base of the second transistor Q2 is 11.68V, which is less than the voltage of the emitter of the second transistor Q2. The transistor conduction condition is not met, and the second transistor Q2 is disconnected. The voltage of the collector of the second transistor Q2 is pulled up to the voltage of the auxiliary power supply U1. At this time, the second control terminal W3 of the charging switch K and the input terminal W1 have a voltage difference of 15V, which makes the charging switch K conduct, so that the positive electrode BUS+ of the charging power supply BUS is directly connected to the positive electrode BAT+ of the battery BAT, and the battery is charged normally. When the charging switch K is a MOS tube, the 15V voltage difference is the voltage difference between the gate and source of the MOS tube, that is, the voltage between the gate and source. This voltage is supplied to charge the gate-source capacitor of the MOS tube. When the gate voltage is reached, the MOS is turned on.

[0068] Working condition 2, when the voltage of the battery BAT is greater than or equal to the voltage of the charging power supply BUS and less than the voltage threshold, assuming that the voltage of the charging power supply BUS and the voltage of the battery BAT are both 12V, the voltage difference between the voltage of the auxiliary power supply U1 and the voltage of the charging power supply BUS is 15V, and the voltage fine-tuning threshold of the auxiliary power supply U1 is 0.02V, then the voltage threshold is 12.02V.

[0069] like Figure 4As shown, the collector of the first transistor Q1 is connected to the positive electrode BAT+ of the battery BAT, and the voltage of the collector of the first transistor Q1 is 12V. Similar to working condition 1, the voltage of the emitter of the first transistor Q1 is 12+0.68=12.68V, and the voltage of the base of the second transistor Q2 is also 12.68V. The emitter of the second transistor Q2 is connected to the positive electrode BUS+ of the charging power supply BUS, and the voltage of the emitter of the second transistor Q2 is 12V. At this time, although the voltage of the base of the second transistor Q2 is greater than the voltage of the emitter, the voltage difference has not yet reached the conduction condition of the transistor, so the second transistor Q2 is still not turned on, and the voltage of the collector of the second transistor Q2 is pulled up to the voltage of the auxiliary power supply U1. At this time, the second control terminal W3 of the charging switch K and the input terminal W1 have a voltage difference of 15V, which makes the charging switch K turn on, and the positive electrode BUS+ of the charging power supply BUS is directly connected to the positive electrode BAT+ of the battery BAT, and the battery is charged normally. When the charging switch K is a MOS tube, the 15V voltage difference is the voltage difference between the gate and source of the MOS tube, that is, the voltage between the gate and source. This voltage is supplied to the gate-source capacitor of the MOS tube to charge. After reaching the gate voltage, the MOS is turned on.

[0070] Working condition 3, when the voltage of the battery BAT is greater than or equal to the voltage threshold, assuming that the voltage of the charging power supply BUS is 12V, the voltage of the battery BAT is 12.02V, and the voltage threshold is 12.02V as described in working condition 2. Figure 4 As shown, the collector of the first transistor Q1 is connected to the positive electrode BAT+ of the battery BAT, and the voltage of the collector of the first transistor Q1 is 12.02V. At this time, the voltage of the base of the second transistor Q2 is the same as the voltage of the base and collector of the first transistor Q1, both of which are 12.7V. Assuming that the conduction condition of the second transistor Q2 is that the inter-electrode voltage between the base and the emitter is greater than or equal to 0.7V, the second transistor Q2 is just critically turned on. At this time, the voltage of the emitter of the second transistor Q2 is the same as the voltage of the charging power supply BUS, which is 12V. The voltage of the collector of the second transistor Q2 is pulled down to 12+ 0.3=12.3V due to the conduction of the transistor, where 0.3V is the conduction voltage drop of the second transistor Q2. At this time, the second control terminal W3 of the charging switch K and the input terminal W1 have a voltage difference of 0.3V, and the voltage difference cannot turn on the charging switch K. The charging switch K is turned off, and the positive electrode BUS+ of the charging power supply BUS is disconnected from the positive electrode BAT+ of the battery BAT, and the charging is completed. When the charging switch K is a MOS tube, the 0.3V voltage difference is the voltage difference between the gate and the source of the MOS tube, that is, the voltage between the gate and the source. The gate-source voltage cannot reach the gate voltage of the MOS tube, and the MOS tube is turned off.

[0071] It is worth noting that, after the transistor is turned on, the conduction voltage drop of the transistor has nothing to do with the magnitude of the turn-on voltage, but is related to the collector current and equivalent resistance in the equivalent circuit of the transistor, and depends on the model of the transistor. The disclosure exemplarily determines the conduction voltage drop of the second transistor Q2 to be 0.3V, which can also be other values, which can be determined specifically according to the model of the transistor.

[0072] Figure 6 is another circuit diagram of a charging protection circuit according to an exemplary embodiment. Figure 6 As shown, the charging protection circuit also includes a voltage follower circuit S2, which includes a second input terminal T1 for connecting to the first terminal D1, a third output terminal T2 for connecting to the second control terminal W3, and a voltage follower terminal T3 for connecting to the collector of the second transistor Q2; the voltage follower circuit S2 is used to keep the voltage of the second control terminal W3 of the charging switch consistent with the voltage of the collector of the second transistor Q2. The present disclosure uses a voltage follower circuit to ensure that the voltage of the second control terminal W3 of the charging switch is consistent with the voltage of the collector of the second transistor Q2, and uses a pure hardware circuit to ensure voltage consistency, with fewer devices and a more stable circuit.

[0073] In a possible implementation, the voltage follower circuit S2 is a push-pull emitter follower circuit, which is composed of two transistors. Figure 7 As shown, the voltage follower circuit S2 includes a third transistor Q3 and a fourth transistor Q4, the base of the third transistor Q3 is connected to the base of the fourth transistor Q4, and the common end of the bases of the two serves as the voltage follower end T3, the collector of the third transistor Q3 serves as the second input end T1, and the collector of the fourth transistor Q4 serves as the third output end T2.

[0074] The present disclosure forms a push-pull emitter follower circuit through the third transistor Q3 and the fourth transistor Q4, which has stable operation, wide frequency response, large input resistance and small output resistance, and greatly improves the frequency response.

[0075] Figure 8 is another circuit diagram of a charging protection circuit according to an exemplary embodiment. Figure 8 As shown, in some embodiments, the charging protection circuit may further include a first resistor R1 and / or a second resistor R2, one end of the first resistor R1 is connected to the first end D1, the other end of the first resistor R1 is connected to the emitter of the first transistor Q1, one end of the second resistor R2 is connected to the first end D1, and the other end of the second resistor R2 is connected to the collector of the second transistor Q2.

[0076] The first resistor R1 and the second resistor R2 are both pull-up resistors. The first resistor R1 can ensure that the voltage of the emitter of the first transistor Q1 is greater than the voltage of the collector, and the voltages of the two form a corresponding voltage difference. The second resistor R2 is used for when the second transistor Q2 is turned off, the voltage of the collector of the second transistor Q2 is pulled up by the second resistor R2 to the voltage of the auxiliary power supply U1 at the upper end.

[0077] like Figure 8 As shown, in some embodiments, the voltage follower circuit S2 may further include a third resistor R3, one end of the third resistor R3 is connected to the first end D1, and the other end of the third resistor R3 is connected to the collector of the third transistor Q3. The third resistor R3 is a pull-up resistor.

[0078] like Figure 8 As shown, in some embodiments, the charging protection circuit further includes a capacitor C, one end of the capacitor C is connected to the auxiliary power supply U1, and the other end of the capacitor C is connected to the charging power supply BUS. The capacitor C is a filter capacitor.

[0079] like Figure 8 As shown, in some embodiments, the charging protection circuit further includes a diode D, the anode of the diode D is connected to the emitter of the second transistor Q2, and the cathode of the diode D is connected to the second control terminal W3 of the charging switch K. The diode D is used to ensure that the current flows out from top to bottom.

[0080] like Figure 8 As shown, in some embodiments, the charging protection circuit further includes a first detection terminal TP1 connected to the positive electrode BAT+ of the battery BAT, a second detection terminal TP2 connected to the common terminal of the emitters of the third transistor Q3 and the fourth transistor Q4, and a third detection terminal TP3 connected to the positive electrode BUS+ of the charging power supply BUS; the first detection terminal TP1 is used to detect the voltage of the battery BAT, the second detection terminal TP2 is used to detect the collector voltage of the third transistor Q3, and the third detection terminal is used to detect the voltage of the charging power supply BUS.

[0081] It is worth noting that the third terminal D3 can also serve as the first detection terminal TP1, the first control terminal P3 can also serve as the second detection terminal TP2, and the second terminal can also serve as the third detection terminal TP3.

[0082] By detecting the collector voltage of the third transistor Q3, it is possible to determine whether the second transistor Q2 is turned on or off. By detecting the voltage of the battery BAT, the collector voltage of the third transistor Q3, and the voltage of the charging power supply BUS, it is possible to determine the working condition of the charging protection circuit. For example, under normal working conditions, the voltage of the charging power supply BUS is greater than the voltage of the battery BAT, and the voltage of the second detection terminal TP2 is the difference between the voltage of the auxiliary power supply U1 and the voltage of the charging power supply BUS.

[0083] The present disclosure also provides a vehicle, including a battery and the charging protection circuit provided in the above embodiment. For details about the charging protection circuit, please refer to the above Figure 2-Figure 8 And the related description will not be repeated here.

[0084] A pure hardware charging protection circuit is provided in the vehicle of the present disclosure, so that when the voltage of the battery BAT is less than the voltage threshold, and the voltage threshold is greater than the voltage of the charging power supply BUS, the charging switch K is maintained on and the battery BAT is prevented from back-feeding the charging power supply BUS, and when the voltage of the battery BAT is greater than or equal to the voltage threshold, the charging switch K is disconnected. The pure hardware circuit design requires fewer components, which improves the economy and reliability of the charging protection circuit, and does not require software logic control, and does not require the introduction of chips and other controlled switching components, so that the overall space volume of the charging protection circuit is small, and there is no need to consider voltage conversion and electrical isolation. It can be used in more environments and can be applied to a variety of low-voltage charging circuits. In addition, by maintaining the charging switch K on when the voltage of the battery BAT is less than the voltage threshold, and the voltage threshold is greater than the voltage of the charging power supply, the battery charging backflow prevention is achieved, and the corresponding threshold is reserved to ensure the normal battery charging function.

[0085] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0086] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0087] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A charging protection circuit, characterized in that: include: A charging switch (K), wherein an input end (W1) of the charging switch (K) is suitable for connecting to a charging power source (BUS), an output end (W2) of the charging switch is suitable for connecting to a battery (BAT), and the charging switch is used to turn on or off charging of the battery (BAT) by the charging power source (BUS); A switch control circuit (S1), wherein a first control terminal (P3) of the switch control circuit (S1) is coupled to a second control terminal (W3) of the charging switch (K), and the switch control circuit (S1) is used to maintain the charging switch (K) on when the voltage of the battery (BAT) is less than a voltage threshold, and to disconnect the charging switch (K) when the voltage of the battery (BAT) is greater than or equal to the voltage threshold, and the voltage threshold is greater than the voltage of the charging power source (BUS); The charging protection circuit further comprises: a first terminal (D1) for connecting to an auxiliary power source (U1), a second terminal (D2) for connecting to a charging power source (BUS), and a third terminal (D3) for connecting to a battery (BAT), wherein the voltage of the auxiliary power source (U1) is greater than the voltage of the charging power source (BUS); The input end (W1) of the charging switch (K) is used to connect to the second end (D2), and the output end (W2) of the charging switch is used to connect to the third end (D3); The first input terminal (P1) of the switch control circuit (S1) is connected to the first terminal (D1), the first output terminal (P2) of the switch control circuit is connected to the third terminal (D3), and the second output terminal (P4) of the switch control circuit (S1) is connected to the input terminal (W1); The switch control circuit (S1) comprises a first triode (Q1) and a second triode (Q2), the emitter of the first triode (Q1) is connected to the collector of the second triode (Q2), and the common end of the two serves as the first input end (P1), the collector of the first triode (Q1) serves as the first output end (P2), the collector of the second triode (Q2) serves as the first control end (P3), and the emitter of the second triode (Q2) serves as the second output end (P4); The emitter of the first transistor (Q1) is respectively connected to the base of the first transistor (Q1) and the base of the second transistor (Q2); The first transistor (Q1) and the second transistor (Q2) are the same, the voltage threshold is the sum of the voltage of the charging power source (BUS) and a fine-tuning threshold, and the fine-tuning threshold is obtained through the conduction characteristics of the first transistor (Q1) and the second transistor (Q2).

2. The charging protection circuit according to claim 1, characterized in that: The voltage of the second control terminal (W3) of the charging switch is consistent with the voltage of the collector of the second transistor (Q2).

3. The charging protection circuit according to claim 2, characterized in that: The charging protection circuit further comprises a voltage follower circuit (S2), wherein the voltage follower circuit (S2) comprises a second input terminal (T1) connected to the first terminal (D1), a third output terminal (T2) connected to the second control terminal (W3), and a voltage follower terminal (T3) connected to the collector of the second transistor (Q2); The voltage follower circuit (S2) is used to keep the voltage of the second control terminal (W3) of the charging switch consistent with the voltage of the collector of the second transistor (Q2).

4. The charging protection circuit according to claim 3, characterized in that: The voltage follower circuit (S2) comprises a third transistor (Q3) and a fourth transistor (Q4), the base of the third transistor (Q3) is connected to the base of the fourth transistor (Q4), and the common end of the bases of the two serves as the voltage follower end (T3), the collector of the third transistor (Q3) serves as the second input end (T1), and the collector of the fourth transistor (Q4) serves as the third output end (T2).

5. The charging protection circuit according to any one of claims 1 to 4, characterized in that: The charging switch (K) is a MOS tube, the source of the MOS tube serves as the input end (W1), the drain of the MOS tube serves as the output end (W2), and the gate of the MOS tube serves as the second control end (W3).

6. The charging protection circuit according to claim 1, characterized in that: The charging protection circuit further comprises a first resistor (R1) and / or a second resistor (R2), one end of the first resistor (R1) is connected to the first end (D1), the other end of the first resistor (R1) is connected to the emitter of the first transistor (Q1), one end of the second resistor (R2) is connected to the first end (D1), and the other end of the second resistor (R2) is connected to the collector of the second transistor (Q2).

7. The charging protection circuit according to claim 4, characterized in that: The voltage follower circuit (S2) further comprises a third resistor (R3), one end of the third resistor (R3) is connected to the first end (D1), and the other end of the third resistor (R3) is connected to the collector of the third transistor (Q3).

8. The charging protection circuit according to claim 1, characterized in that: The charging protection circuit further comprises a capacitor (C), one end of the capacitor (C) is connected to the auxiliary power supply (U1), and the other end of the capacitor (C) is connected to the charging power supply (BUS).

9. A vehicle, characterized in that: The invention comprises a battery and a charging protection circuit according to any one of claims 1 to 8.

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