An overcurrent detection circuit and a battery protection device

Abstract

The present invention is applicable to the technical field of battery protection, and provides an overcurrent detection circuit and a battery protection device. The circuit includes an overcurrent comparator, a logic control circuit, a constant current loop, and a feedback loop. The overcurrent comparator is configured to receive the sampled input voltage and output voltage as input signals, and control whether the overcurrent comparator flips according to the comparison result between the voltage difference between the input voltage and the output voltage and a first reference voltage. The logic control circuit is configured to receive the output signal of the overcurrent comparator and control the on / off of the constant current loop according to the received output signal. The constant current loop is configured to determine the current magnitude of a sampling resistor according to the magnitudes of the sampled voltage and a second reference voltage. The feedback loop is configured to sample and control the output voltage to be equal to the output detection voltage. It is possible to reduce the influence of the offset voltage of components in the constant current loop and the feedback loop on the overcurrent threshold, and obtain a high-precision overcurrent threshold.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery protection, and particularly relates to an overcurrent detection circuit and a battery protection device. Background Art

[0002] In portable current applications, lithium-ion battery-powered applications are very widespread. Due to the stability problems of lithium-ion batteries, overvoltage and overcurrent integrated circuits (ICs) are commonly used as the front-end applications of lithium-ion battery chargers to protect lithium-ion batteries and their chargers.

[0003] The overvoltage and overcurrent integrated circuit (IC) can implement various protection functions, such as input power overvoltage protection, lithium battery overvoltage protection, load current limiting protection, IC overheat protection, etc. Typical applications of the overvoltage and overcurrent integrated circuit are as follows Figure 1 , where U1 is an overvoltage and overcurrent protection IC. Among them, VBAT is used to detect the battery voltage, and R ILIM is used to set the overcurrent protection threshold. When the load current is less than the set current limit value, the current value is determined by the load; when the load current setting value is greater than the set current limit value, U1 will maintain the load current at the set current limit value for a certain period of time. If the duration is greater than the set time, U1 will turn off the internal MOSFET to cut off the backend power supply. However, the above method is commonly used for medium and above overcurrent thresholds, but is not suitable for smaller overcurrent protection thresholds because the offset of the operational amplifier will cause overcurrent threshold deviation and a large range. It can be seen that when the overvoltage and overcurrent integrated circuit in the prior art is used for a smaller overcurrent protection threshold, there are problems of overcurrent threshold deviation and a large range caused by the offset of the operational amplifier. Summary of the Invention

[0004] An embodiment of the present invention provides an overcurrent detection circuit, aiming to solve the problems that when the overvoltage and overcurrent integrated circuit in the prior art is used for a smaller overcurrent protection threshold, there are problems of overcurrent threshold deviation and a large range caused by the offset of the operational amplifier.

[0005] An embodiment of the present invention provides an overcurrent detection circuit, including: an overcurrent comparator, a logic control circuit, a constant current loop, and a feedback loop;

[0006] The overcurrent comparator is used to receive the sampled input voltage and output voltage as input signals, and control whether the overcurrent comparator flips according to the comparison result between the voltage difference of the input voltage and the output voltage and the first reference voltage;

[0007] The logic control circuit is used to receive the output signal of the overcurrent comparator and control the on / off of the constant current loop according to the received output signal;

[0008] The constant current loop is used to determine the current magnitude of the sampling resistor according to the magnitude of the sampled sampling voltage and the second reference voltage;

[0009] The feedback loop is used to sample the output voltage and the output detection voltage of the constant current loop, and control the output voltage to be equal to the output detection voltage.

[0010] Furthermore, a filter circuit is further included. One end of the filter circuit is connected to the constant current loop and the feedback loop, and the other end is grounded.

[0011] Furthermore, the filter circuit includes a first voltage dividing resistor and a filter capacitor. After being connected in parallel, one end of the first voltage dividing resistor and the filter capacitor is connected to the voltage output end of the constant current loop, and the other end is grounded.

[0012] Furthermore, the overcurrent comparator includes a positive input terminal and a negative input terminal. The positive input terminal receives the sampled input voltage, and the negative input terminal receives the sampled output voltage.

[0013] Furthermore, the constant current loop includes a first operational amplifier, a first field effect transistor, a second field effect transistor, a third field effect transistor, and the sampling resistor. The output terminal of the first operational amplifier is simultaneously connected to the logic control circuit, the control terminal of the second field effect transistor, and the control terminal of the third field effect transistor. The positive input terminal of the first operational amplifier is connected to the output terminal of the first field effect transistor and one end of the sampling resistor for sampling the sampling voltage. The negative input terminal of the first operational amplifier is used for sampling the second reference voltage. The input terminal of the second field effect transistor is connected to the input terminal of the third field effect transistor for collecting the input voltage.

[0014] Furthermore, the feedback loop includes a second operational amplifier, and the second operational amplifier and the first field effect transistor form a negative feedback loop.

[0015] Furthermore, the output terminal of the second operational amplifier is connected to the control terminal of the first field effect transistor. The positive input terminal of the second operational amplifier is connected to the output terminal of the second field effect transistor for sampling the output detection voltage. The negative input terminal of the second operational amplifier is connected to the output terminal of the third field effect transistor for sampling the output voltage. And the input terminal of the first field effect transistor is connected to the output terminal of the second field effect transistor and the positive input terminal of the second operational amplifier.

[0016] Furthermore, the first field effect transistor is an NMOS transistor, and the second field effect transistor and the third field effect transistor are PMOS transistors.

[0017] Further, the control terminals of the first field effect transistor, the second field effect transistor, and the third field effect transistor are the gates of the NMOS transistor and the PMOS transistor. The output terminal of the first field effect transistor is the source of the NMOS transistor, and the input terminal is the drain of the NMOS transistor. The output terminals of the second field effect transistor and the third field effect transistor are the drains of the PMOS transistors, and the input terminals are the sources of the PMOS transistors.

[0018] The present invention also provides a battery protection device, including the overcurrent detection circuit described in any one of the above embodiments.

[0019] The beneficial effects achieved by the present invention are as follows: Since the present invention first combines the sampled input voltage and output voltage as two input signals of the overcurrent comparator, directly calculates the voltage difference between the input voltage and the output voltage, compares the voltage difference with the first reference voltage, and controls whether the overcurrent comparator flips according to the comparison result. In this way, by detecting the voltage, the influence of the offset voltage of the components in the constant current loop and the feedback loop on the overcurrent threshold can be reduced, thereby obtaining a high-precision overcurrent threshold; and the structure is simple and easy to implement. Description of the Drawings

[0020] Figure 1 is a circuit diagram of an overcurrent detection circuit provided by the prior art;

[0021] Figure 2 is a circuit diagram of an overcurrent detection circuit provided by an embodiment of the present invention;

[0022] Figure 3 is a circuit diagram of another overcurrent detection circuit provided by an embodiment of the present invention;

[0023] Figure 4 is a circuit diagram of another overcurrent detection circuit provided by an embodiment of the present invention.

[0024] Among them, 1. Overcurrent comparator, 2. Logic control circuit, 3. Constant current loop, 4. Feedback loop, 5. Filter circuit, 6. First voltage dividing circuit, 7. Second voltage dividing circuit. Detailed Embodiments

[0025] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] In the present invention, first, the sampled input voltage and output voltage are combined as two input signals of an overcurrent comparator. By directly calculating the voltage difference between the input voltage and the output voltage, comparing the voltage difference with a first reference voltage, and controlling whether the overcurrent comparator flips according to the comparison result. In this way, by detecting the voltage, the influence of voltage caused by component offset in the constant current loop and the feedback loop on the overcurrent threshold can be reduced, thereby obtaining a high-precision overcurrent threshold; and the structure is simple and easy to implement.

[0027] Example 1

[0028] See Figure 2 as shown in Figure 2 FIG. 10 is a module connection diagram of an overcurrent detection circuit provided by an embodiment of the present invention. The overcurrent detection circuit includes: an overcurrent comparator 1, a logic control circuit 2, a constant current loop 3, and a feedback loop 4;

[0029] The overcurrent comparator 1 is configured to receive the sampled input voltage and output voltage as input signals, and control whether the overcurrent comparator 1 flips according to the comparison result between the voltage difference between the input voltage and the output voltage and a first reference voltage;

[0030] The logic control circuit 2 is configured to receive the output signal of the overcurrent comparator 1 and control the on / off of the constant current loop 3 according to the output signal;

[0031] The constant current loop 3 is configured to determine the current magnitude of the sampling resistor according to the magnitude relationship between the sampled sampling voltage and a second reference voltage;

[0032] The feedback loop 4 is configured to sample the output voltage and the output detection voltage of the constant current loop 3, and control the output voltage to be equal to the output detection voltage.

[0033] Wherein, one end of the logic control circuit 2 is connected to the overcurrent comparator 1, and the other end is connected to the constant current loop 3. One end of the above-mentioned constant current loop 3 is connected to the logic control circuit 2, and the other end is connected to the feedback loop 4. The input end of the above-mentioned feedback loop 4 is connected to the output end of the constant current loop 3 for receiving the output voltage of the constant current loop 3 and stably outputting its output voltage.

[0034] In the embodiment of the present invention, referring to Figure 3 as shown in FIG. 11, the overcurrent comparator is an OCP Comp, including a positive input terminal, a negative input terminal, and an output terminal. The positive input terminal receives the input voltage (V IN ) sampled in the circuit, and the negative input terminal receives the output voltage (V OUT ) sampled in the circuit. That is, the sampled input voltage (V IN ) and the output voltage (V OUTThey are respectively used as two input signals of the overcurrent comparator OCP Comp, and the overcurrent comparator OCP Comp can calculate the voltage difference V according to the magnitudes of the two input signals. IN -V OUT According to the voltage difference V IN -V OUT and the magnitude relationship with the first reference voltage (Vref2), it is possible to control whether the overcurrent comparator OCP Comp flips. According to the flipping situation, an accurate overcurrent threshold can be calculated. Among them, the first reference voltage Vref2 is the reference voltage provided for the overcurrent comparator.

[0035] One end of the above-mentioned logic control circuit is connected to the overcurrent comparator, and the other end is connected to the constant current loop. The logic control circuit can also be called the power switch control logic (Logic&Driver). Among them, Logic is used to control the turning on and off of the power switch tube; Driver is the gate driving circuit of the power switch tube. The power switch control logic can receive the output signal of the overcurrent comparator, that is, whether the overcurrent comparator flips / does not flip. According to the flipping / non-flipping situation, it can control the on / off situation of the power switch in the constant current loop.

[0036] One end of the above-mentioned constant current loop is connected to the logic control circuit, and the other end is connected to the feedback loop. The above-mentioned sampling resistor (Rsns) is set between the grounding ends of the constant current loop, and the sampling voltage Vsns can be obtained from the sampling resistor Rsns terminal; the above-mentioned second reference voltage (Vref3) is the reference voltage Vsns provided for the constant current loop. The sampling voltage Vsns and the second reference voltage Vref3 can be used as two input signals of the constant current loop. When the sampling voltage Vsns is less than the second reference voltage Vref3, it can indicate that the load current is less than the preset overcurrent threshold. At this time, the constant current loop does not work, and the output current (Iout) of the circuit can be determined according to the size of the load. When the sampling voltage Vsns is greater than or equal to the second reference voltage Vref3, it indicates that the load current is greater than the preset overcurrent threshold. At this time, the constant current loop starts to work, and at this time, the constant current loop can control the sampling voltage Vsns to be equal to the second reference voltage Vref3.

[0037] The input end of the above-mentioned feedback loop is connected to the output end of the constant current loop and is used to receive the output voltage of the constant current loop. And the feedback loop has two input ends, and the output voltage (Vout) and the output detection voltage (Vout-sns) can be respectively received at the two input ends. The feedback loop can control the sampled output detection voltage Vout-sns to be equal to the output voltage Vout, which is beneficial to obtaining an accurate sampling ratio.

[0038] In the embodiment of the present invention, since the sampled input voltage and output voltage are first combined as two input signals of the overcurrent comparator, and the voltage difference V between the input voltage and the output voltage is directly calculated IN -V OUT , the voltage difference V IN -V OUT is compared with the first reference voltage Vref2, and whether the overcurrent comparator flips is controlled according to the comparison result. In this way, by detecting the voltage, the influence of the voltage when the components in the constant current loop and the feedback loop are out of adjustment on the overcurrent threshold can be reduced, so as to obtain a high-precision overcurrent threshold; and the structure is simple and easy to implement.

[0039] Example 2

[0040] In the embodiment of the present invention, based on the specific embodiment 1, a filter circuit 5 is further included. One end of the filter circuit 5 is connected to the constant current loop and the feedback loop, and the other end is grounded.

[0041] Among them, the filter circuit 5 can filter out the interference waves in the circuit and ensure the stable output voltage. The filter circuit 5 includes a first voltage dividing resistor and a filter capacitor. The first voltage dividing resistor and the filter capacitor are connected in parallel, and one end is connected to the voltage output end of the constant current loop, and the other end is grounded. Refer to Figure 3 , the first voltage dividing resistor is Rout, and the filter capacitor is Cout.

[0042] Optionally, the above-mentioned constant current loop includes a first operational amplifier, a first field effect transistor, a second field effect transistor, a third field effect transistor, and a sampling resistor. The output end of the first operational amplifier is simultaneously connected to the logic control circuit, the control end of the second field effect transistor, and the control end of the third field effect transistor. The positive input end of the first operational amplifier is connected to the output end of the first field effect transistor and one end of the sampling resistor for collecting the sampling voltage. The negative input end of the first operational amplifier is used for sampling the second reference voltage Vref3; the input end of the second field effect transistor is connected to the input end of the third field effect transistor for collecting the input voltage.

[0043] Refer to Figure 3 As shown, among them, the first operational amplifier is A2, the first field effect transistor is M1, the second field effect transistor is M0-SNS, the third field effect transistor is M0, and the sampling resistor is Rsns. The first field effect transistor M1 is an NMOS transistor, the second field effect transistor M0-SNS and the third field effect transistor M0 are PMOS transistors, and the second field effect transistor M0-SNS and the third field effect transistor M0 are used as power switch transistors and sampling transistors at the same time. The gate (G pole) of the NMOS transistor and the PMOS transistor is the control end, the source (S pole) of the NMOS transistor and the drain (D pole) of the PMOS transistor are the output ends, and the drain (D pole) of the NMOS transistor and the source (S pole) of the PMOS transistor are the input ends.

[0044] Specifically, the first operational amplifier A2 includes a positive input terminal, a negative input terminal, and an output terminal. The positive input terminal of the first operational amplifier A2 is connected between the S pole of the first field effect transistor M1 and the sampling resistor Rsns for collecting the sampling voltage Vsns of the sampling resistor Rsns. The negative input terminal of the first operational amplifier A2 is the input terminal of the second reference voltage Vref3. The output terminal of the first operational amplifier A2 is connected to the G pole of the second field effect transistor M0-SNS and the G pole of the third field effect transistor M0. After amplifying the weak voltage, a voltage signal is output to both the second field effect transistor M0-SNS and the third field effect transistor M0 at the same time. The logic control circuit is also connected to the G pole of the second field effect transistor M0-SNS and the G pole of the third field effect transistor M0 to control the on and off of the third field effect transistor M0.

[0045] Optionally, the feedback loop includes a second operational amplifier, and the second operational amplifier and the first field effect transistor form a negative feedback loop.

[0046] Reference Figure 3 As shown, among them, the second operational amplifier is A1, and the second operational amplifier includes a positive input terminal, a negative input terminal, and an output terminal. The positive input terminal of the second operational amplifier A1 is connected to the S pole of the second field effect transistor M0-SNS and the D pole of the first field effect transistor M1. The negative input terminal of the second operational amplifier A1 is connected to the S pole of the third field effect transistor M0. The output terminal of the second operational amplifier A1 is connected to the G pole of the first field effect transistor M1. A negative feedback loop is formed between the second operational amplifier A1 and the first field effect transistor M1, and the negative feedback loop can be used to stabilize the output voltage or gain, and can also expand the passband.

[0047] Specifically, the connection of the positive input terminal of the second operational amplifier A1 to the S pole of the second field effect transistor M0-SNS can be used to sample the output detection voltage (Vout-sns), and the connection of the negative input terminal of the second operational amplifier A1 to the S pole of the third field effect transistor M0 can be used to sample the output voltage (Vout). And because the D pole of the first field effect transistor M1 is connected to the S pole of the second field effect transistor M0-SNS and the positive input terminal of the second operational amplifier A1, and the G pole of the first field effect transistor M1 is connected to the G pole of the first field effect transistor M1, the output voltage (Vout) can be stabilized through the negative feedback loop formed between the second operational amplifier A1 and the first field effect transistor M1, so that Vout-sns is equal to Vout. However, due to the offset voltage V of the operational amplifier A1 OS , it will cause the phenomenon of V OUT_SNS =V OUT -V OS .

[0048] More specifically, the following is the working principle of the overcurrent detection circuit provided by the embodiment:

[0049] When the input voltage and the output voltage sampled by the overcurrent comparator OCP Comp satisfy:

[0050] V IN -V OUT ≥V ref2 (1)

[0051] The overcurrent comparator OCP Comp flips and starts to work normally. The logic control circuit can output a low level to the G poles of the second field effect transistor M0 - SNS and the third field effect transistor M0, making the second field effect transistor M0 - SNS and the third field effect transistor M0 conduct (Vgs < Vt). The S pole of the second field effect transistor M0 - SNS is connected to the D pole of the first field effect transistor M1 and outputs a high level to make it conduct. At the same time, the sampling current flows through the sampling resistor Rsns to obtain the sampling voltage Vsns. When the sampling voltage and the second reference voltage satisfy Vsns ≥ Vref3, the first operational amplifier A2 starts to work normally and forms a negative feedback loop with M0_SNS and M1, making Vsns = Vref3. At this time, the load current I OUT is equal to:

[0052]

[0053] where K is the sampling ratio coefficient of the second field effect transistor M0 - SNS and the third field effect transistor M0, and the sampling ratio can be set to 1:K.

[0054] When the constant - current loop starts to work, if the overcurrent threshold I OCP is small (which means V IN -V OUT is small), at this time V IN -V OUT <V ref2 , the overcurrent comparator OCP Comp does not flip; then the constant - current loop keeps working. As the load gets heavier, the V OUT voltage drops, and when V IN -V OUT ≥V ref2 , the overcurrent comparator OCP Comp flips. At this time, the offset voltages V OS of the first operational amplifier A1 and the second operational amplifier A1 itself can be ignored. At this time, the overcurrent protection threshold I OCP is:

[0055]

[0056] If the overcurrent threshold I OCP is large (which means V IN -V OUT is large), at this time, the offset voltage V OS on the overcurrent threshold I OCPThe influence of can also obtain formula (3). Therefore, regardless of the overcurrent threshold I OCP high or low, the present invention can avoid the influence brought by the offset voltage Ios, so as to obtain a high-precision overcurrent threshold.

[0057] In the embodiment of the present invention, by using the input voltage and the output voltage as the two input signals of the overcurrent comparator, only when the electrical difference V IN -V OUT reaches the first reference voltage Vref3, the overcurrent comparator can flip. By detecting the voltage to reduce the influence of the operational amplifier offset voltage on the overcurrent threshold, it can overcome the certain offset existing in the amplifier in the circuit, so that when overcurrent protection occurs, if the V IN -V OUT is small, there will be a large deviation in the sampling current ratio; as the V OUT decreases, the problem that the sampling current ratio returns to the normal value can be avoided, so as to avoid a large deviation in the overcurrent protection threshold IOCP and a large change range of IOCP under different loads. It can obtain the advantages of high-precision overcurrent threshold, simple structure and easy implementation.

[0058] As a possible embodiment, as Figure 4 shown, Figure 4 is the circuit diagram of another overcurrent detection circuit provided by the embodiment of the present invention. On the basis of the above embodiment, it further includes a first voltage dividing circuit 6 and a second voltage dividing circuit 7. The first voltage dividing circuit 6 includes a first voltage dividing resistor R1 and a second voltage dividing resistor R2 connected in series, and the second voltage dividing circuit 7 includes a third voltage dividing resistor R3 and a fourth voltage dividing resistor R4 connected in series.

[0059] Among them, after the first voltage dividing resistor R1 and the second voltage dividing resistor R2 are connected in series, one end is connected to the S pole of the third field effect transistor M0, the positive input terminal of the second amplifier A1, and the filter circuit 5, and the other end is grounded. The output voltage Vout-div can be collected between the first voltage dividing resistor R1 and the second voltage dividing resistor R2, and the output voltage Vout-div is used as the input signal of the positive input terminal of the overcurrent comparator.

[0060] After the third voltage dividing resistor R3 and the fourth voltage dividing resistor R4 are connected in series, one end is connected to the D pole of the second field effect transistor M0-SNS and the D pole of the third field effect transistor M0, and the other end is grounded. The input voltage Vin-div can be collected between the third voltage dividing resistor R3 and the fourth voltage dividing resistor R4, and the input voltage Vin-div is used as the input signal of the negative input terminal of the overcurrent comparator.

[0061] Moreover, in this embodiment, the above-mentioned first field-effect transistor M1 can be replaced by a PMOS transistor, and the second field-effect transistor M0-SNS and the third field-effect transistor M0 can be replaced by NMOS transistors. The positive input terminal and the negative input terminal of the first amplifier A2 and the second amplifier A1 are connected reversely.

[0062] Specifically, when the following condition is satisfied:

[0063] Vin-div - Vout-div ≥ Vref3 (4)

[0064] The overcurrent comparator OCP Comp flips. When the constant current loop starts to work, if the overcurrent threshold I OCP is small (which means Vin-div - Vout-div is small), at this time Vin-div - Vout-div < Vref3, and the overcurrent comparator OCP Comp does not flip; then the constant current loop keeps working. As the load gets heavier, the OUT voltage drops, and when Vin-div - Vout-div ≥ Vref3, the overcurrent comparator OCP Comp flips. At this time, the offset voltage V OS , and the overcurrent protection threshold I OCP is as shown in the above formula (3).

[0065] If the overcurrent threshold I OCP is large (which means Vin-div - Vout-div is large), at this time the influence of the offset voltage V OS on I OCP can be ignored, and the formula (3) can also be obtained. Therefore, regardless of whether I OCP is high or low, the present invention can always obtain a high-precision overcurrent threshold.

[0066] In the embodiment of the present invention, since the sampled input voltage and output voltage are first combined as the two input signals of the overcurrent comparator, and the voltage difference between the input voltage and the output voltage is directly calculated, and the voltage difference V IN -V OUT is compared with the first reference voltage Vref2, and the flipping of the overcurrent comparator is controlled according to the comparison result. In this way, by detecting the voltage, the influence of the voltage caused by the offset of the components in the constant current loop and the feedback loop on the overcurrent threshold can be reduced, so as to obtain a high-precision overcurrent threshold; and the structure is simple and easy to implement.

[0067] Example 3

[0068] The present invention also provides a battery protection device, including the overcurrent detection circuit of any one of the above embodiments.

[0069] In this embodiment, the above battery protection device can be used for overcurrent protection of the front end of a lithium battery. Since the battery protection device includes any one of the above overcurrent detection circuits, and the current detection circuit first combines the sampled input voltage and output voltage as two input signals of an overcurrent comparator, and directly calculates the voltage difference between the input voltage and the output voltage, and compares the voltage difference V IN -V OUT with a first reference voltage Vref2, and controls whether the overcurrent comparator flips according to the comparison result. In this way, by detecting the voltage, the influence of the offset voltage of the components in the constant current loop and the feedback loop on the overcurrent threshold can be reduced, so as to obtain a high-precision overcurrent threshold; and the structure is simple and easy to implement. Therefore, the battery protection device also has the above effects.

[0070] The terms "including" and "having" and any variations thereof in the specification, claims and drawings of this application are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the specification, claims or drawings of this application are used to distinguish different objects, rather than to describe a specific order. The mention of "embodiment" in this article means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of this application. The appearance of this phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0071] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An overcurrent detection circuit, characterized in that, Comprising: An overcurrent comparator, a logic control circuit, a constant current loop, and a feedback loop; The overcurrent comparator is configured to receive the sampled input voltage and output voltage as input signals, and control whether the overcurrent comparator flips according to the comparison result between the voltage difference of the input voltage and output voltage and a first reference voltage; The logic control circuit is configured to receive the output signal of the overcurrent comparator and control the on / off of the constant current loop according to the output signal; The constant current loop is configured to determine the current magnitude of the sampling resistor according to the magnitudes of the sampled sampling voltage and a second reference voltage; The feedback loop is configured to sample the output voltage of the constant current loop and the output detection voltage, and control the output voltage to be equal to the output detection voltage; The constant current loop includes a first operational amplifier, a first field effect transistor, a second field effect transistor, a third field effect transistor, and the sampling resistor. The output end of the first operational amplifier is connected to the logic control circuit, the control end of the second field effect transistor, and the control end of the third field effect transistor at the same time. The positive input end of the first operational amplifier is connected to the output end of the first field effect transistor and one end of the sampling resistor for sampling the sampling voltage. The negative input end of the first operational amplifier is used for sampling the second reference voltage. The input end of the second field effect transistor is connected to the input end of the third field effect transistor for collecting the input voltage; The feedback loop includes a second operational amplifier, and the second operational amplifier and the first field effect transistor form a negative feedback loop; The output end of the second operational amplifier is connected to the control end of the first field effect transistor. The positive input end of the second operational amplifier is connected to the output end of the second field effect transistor for sampling the output detection voltage. The negative input end of the second operational amplifier is connected to the output end of the third field effect transistor for sampling the output voltage. And the input end of the first field effect transistor is connected to the output end of the second field effect transistor and the positive input end of the second operational amplifier.

2. The overcurrent detection circuit according to claim 1, wherein Further comprising a filter circuit, one end of the filter circuit is connected to the constant current loop and the feedback loop, and the other end is grounded.

3. The overcurrent detection circuit according to claim 2, characterized in that The filter circuit includes a first voltage dividing resistor and a filter capacitor. The first voltage dividing resistor and the filter capacitor are connected in parallel, and one end is connected to the voltage output end of the constant current loop, and the other end is grounded.

4. The overcurrent detection circuit according to claim 1, wherein The overcurrent comparator includes a positive input end and a negative input end. The positive input end receives the sampled input voltage, and the negative input end receives the sampled output voltage.

5. The overcurrent detection circuit according to claim 1, characterized in that, The first field effect transistor is an NMOS transistor, and the second field effect transistor and the third field effect transistor are PMOS transistors.

6. The overcurrent detection circuit according to claim 5, characterized in that, The control ends of the first field effect transistor, the second field effect transistor, and the third field effect transistor are the gates of the NMOS transistor and the PMOS transistors. The output end of the first field effect transistor is the source of the NMOS transistor, and the input end is the drain of the NMOS transistor. The output ends of the second field effect transistor and the third field effect transistor are the drains of the PMOS transistors, and the input ends are the sources of the PMOS transistors.

7. A battery protection device, characterized in that, An overcurrent detection circuit as described in any one of claims 1-6 is included.

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