CN112271764A - Overcurrent detection circuit and battery protection device - Google Patents

Overcurrent detection circuit and battery protection device Download PDF

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Publication number
CN112271764A
CN112271764A CN202011017821.8A CN202011017821A CN112271764A CN 112271764 A CN112271764 A CN 112271764A CN 202011017821 A CN202011017821 A CN 202011017821A CN 112271764 A CN112271764 A CN 112271764A
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China
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voltage
output
field effect
effect transistor
overcurrent
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Inventor
贺江平
王俊喜
孙晓良
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Shenzhen Siyuan Semiconductor Co ltd
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Shenzhen Siyuan Semiconductor Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
    • G01R19/16571—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing AC or DC current with one threshold, e.g. load current, over-current, surge current or fault current
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
    • G01R19/16576—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing DC or AC voltage with one threshold
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/18—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for batteries; for accumulators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • H02J7/00304—Overcurrent protection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • H02J7/00308—Overvoltage protection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • H02J7/0036—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using connection detecting circuits

Abstract

The invention is suitable for the technical field of battery protection, and provides an overcurrent detection circuit and a battery protection device, wherein the circuit comprises an overcurrent comparator, a logic control circuit, a constant current loop and a feedback loop; the overcurrent comparator is used for receiving the sampled input voltage and output voltage as input signals and controlling whether the overcurrent comparator is turned over or not according to a comparison result of a voltage difference between the input voltage and the output voltage and a first reference voltage; the logic control circuit is used for receiving the output signal of the over-current comparator and controlling the on-off of the constant current loop according to the received output signal; the constant current loop is used for determining the current of the sampling resistor according to the sampled sampling voltage and the second reference voltage; the feedback loop is used for sampling and controlling the output voltage to be equal to the output detection 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, and the high-precision overcurrent threshold can be obtained.

Description

Overcurrent detection circuit and battery protection device
Technical Field
The invention belongs to the technical field of battery protection, and particularly relates to an overcurrent detection circuit and a battery protection device.
Background
In portable current applications, lithium ion batteries are used very widely for power. Because of the stability problem of lithium ion batteries, over-voltage and over-current Integrated Circuits (ICs) are commonly used as the front-end application of lithium ion battery chargers to protect the lithium ion batteries and their chargers.
The overvoltage and overcurrent integrated circuit IC can realize various protection functions, such as input power supply overvoltage protection, lithium battery overvoltage protection, load current limiting protection, IC overheating protection and the like. An overvoltage and overcurrent integrated circuit is typically applied as shown in fig. 1, and U1 is an overvoltage and overcurrent protection IC. Where VBAT is used to detect the battery voltage, RILIMFor setting an overcurrent protection threshold. When the load current is smaller than the set current limiting value, the current value is determined by the load; when the load current setting is greater than the set current limit value, U1 holds the load current at the set current limit value for a certain time. If the duration is greater than the set time, U1 turns off the internal MOSFETs to cut off the back-end power supply. The above method is often used for medium and above overcurrent thresholds, but is not suitable for smaller overcurrent protection thresholds, because the offset of the op-amp causes the overcurrent threshold to deviate and range widely. Therefore, if the overvoltage and overcurrent integrated circuit in the prior art is applied to a smaller overcurrent protection threshold, the problems of overcurrent threshold deviation and a larger range caused by imbalance of an operation amplifier exist.
Disclosure of Invention
The embodiment of the invention provides an overcurrent detection circuit, aiming at solving the problems of overcurrent threshold deviation and large range caused by imbalance of an operation amplifier if an overvoltage and overcurrent integrated circuit in the prior art is applied to a small overcurrent protection threshold.
An embodiment of the present invention provides an overcurrent detection circuit, including: the overcurrent protection circuit comprises an overcurrent comparator, a logic control circuit, a constant current loop and a feedback loop;
the overcurrent comparator is used for receiving the sampled input voltage and output voltage as input signals and controlling whether the overcurrent comparator is turned over or not according to the comparison result of the voltage difference between the input voltage and the output voltage and the first reference voltage;
the logic control circuit is used for receiving the output signal of the over-current comparator and controlling the on-off of the constant current loop according to the received output signal;
the constant current loop is used for determining the current of the sampling resistor according to the sampled sampling voltage and the second reference voltage;
the feedback loop is used for sampling the output voltage of the constant current loop and outputting the detection voltage, and controlling the output voltage to be equal to the output detection voltage.
Furthermore, the filter circuit is further included, one end of the filter circuit is connected with the constant current loop and the feedback loop, and the other end of the filter circuit is grounded.
Furthermore, the filter circuit comprises a first voltage-dividing resistor and a filter capacitor, wherein one end of the first voltage-dividing resistor is connected to the voltage output end of the constant current loop after being connected in parallel with the filter capacitor, and the other end of the first voltage-dividing resistor is grounded.
Further, the over-current comparator comprises 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.
Furthermore, the constant current loop comprises a first operational amplifier, a first field effect transistor, a second field effect transistor, a third field effect transistor and the sampling resistor, wherein 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 and is used for sampling the sampling voltage, and the negative input end of the first operational amplifier is used for sampling the second reference voltage; and the input end of the second field effect transistor is connected with the input end of the third field effect transistor and is used for collecting the input voltage.
Furthermore, the feedback loop comprises a second operational amplifier, and the second operational amplifier forms a negative feedback loop together with the first field effect transistor.
Furthermore, 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.
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.
Furthermore, 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, the input terminal of the first field effect transistor 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 transistor, and the input terminal of the second field effect transistor and the third field effect transistor is the source of the PMOS transistor.
The invention also provides a battery protection device which comprises the overcurrent detection circuit in any one of the embodiments.
The invention achieves the following beneficial effects: according to the invention, the sampled input voltage and output voltage are firstly used as two input signals of the overcurrent comparator, the voltage difference between the input voltage and the output voltage is directly calculated, the voltage difference is compared with the first reference voltage, and whether the overcurrent comparator is overturned is controlled according to the comparison result, so that the influence of the offset voltage of components in a constant current loop and a feedback loop on the overcurrent threshold can be reduced by detecting the voltage, and the high-precision overcurrent threshold is obtained; and the structure is simple and easy to realize.
Drawings
Fig. 1 is a circuit diagram of an over-current detection circuit provided in the prior art;
fig. 2 is a circuit diagram of an over-current detection circuit according to an embodiment of the present invention;
fig. 3 is a circuit diagram of another over-current detection circuit according to an embodiment of the present invention;
fig. 4 is a circuit diagram of another over-current detection circuit according to an embodiment of the present invention.
The circuit comprises an overcurrent comparator, a logic control circuit, a constant current loop, a feedback loop, a filter circuit, a first voltage division circuit, a second voltage division circuit and a feedback loop, wherein the overcurrent comparator is 1, the logic control circuit is 2, the constant current loop is 3, the feedback loop is 4, the filter circuit is 5, the first voltage division circuit is 6, and the second voltage division circuit is 7.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
According to the invention, the sampled input voltage and output voltage are taken as two input signals of the over-current comparator, the voltage difference between the input voltage and the output voltage is directly calculated, the voltage difference is compared with the first reference voltage, and whether the over-current comparator is overturned or not is controlled according to the comparison result, so that the influence of the voltage on the over-current threshold value when the components in the constant current loop and the feedback loop are out of regulation can be reduced by detecting the voltage, and the high-precision over-current threshold value is obtained; and the structure is simple and easy to realize.
Example one
Referring to fig. 2, fig. 2 is a module connection diagram of an over-current detection circuit according to an embodiment of the present invention. The overcurrent detection circuit includes: the overcurrent comparator 1, the logic control circuit 2, the constant current loop 3 and the feedback loop 4;
the overcurrent comparator 1 is used for receiving the sampled input voltage and output voltage as input signals, and controlling whether the overcurrent comparator 1 overturns or not according to a comparison result of a voltage difference between the input voltage and the output voltage and a first reference voltage;
the logic control circuit 2 is used for receiving the output signal of the overcurrent comparator 1 and controlling the on-off of the constant current loop 3 according to the output signal;
the constant current loop 3 is used for determining the current of the sampling resistor according to the sampled sampling voltage and the second reference voltage;
the feedback loop 4 is used for sampling the output voltage of the constant current loop 3 and outputting the detection voltage, and controlling the output voltage to be equal to the output detection voltage.
One end of the logic control circuit 2 is connected with the overcurrent comparator 1, and the other end is connected with the constant current loop 3. One end of the constant current loop 3 is connected with the logic control circuit 2, the other end of the constant current loop is connected with the feedback loop 4, and the input end of the feedback loop 4 is connected with the output end of the constant current loop 3 and used for receiving the output voltage of the constant current loop 3 and stably outputting the output voltage.
In the embodiment of the present invention, referring to fig. 3, the over-current comparator is OCP Comp, and includes a positive input terminal, a negative input terminal, and an output terminal. Positive input terminal receiving input voltage (V) sampled in circuitIN) The negative input end receives the output voltage (V) sampled in the circuitOUT). I.e. the input voltage (V) to be sampledIN) And the output voltage (V)OUT) Respectively as two input signals of the over-current comparator OCP Comp, which can calculate the voltage difference V according to the magnitude of the two input signalsIN-VOUTAccording to the voltage difference VIN-VOUTThe magnitude relation between the first reference voltage (Vref2) and the second reference voltage (Vref) can control whether the over-current comparator OCP Comp is inverted or not, and an accurate over-current threshold value can be calculated according to the inversion condition. The first reference voltage Vref2 is a reference voltage provided by the over-current comparator.
One end of the logic control circuit is connected with the overcurrent comparator, and the other end of the logic control circuit is connected with the constant current loop. The Logic control circuit can also be called as a power switch control Logic (Logic & Driver), wherein the Logic is used for controlling the on and off of the power switch tube; driver is a gate drive circuit of the power switch tube. The power switch control logic can receive an output signal of the overcurrent comparator, namely the overcurrent comparator is turned over/not turned over, and the on-off condition of a power switch in the constant current loop can be controlled according to the turning over/not turning over condition.
One end of the constant current loop is connected with the logic control circuit, and the other end of the constant current loop is connected with the feedback loop. The sampling resistor (Rsns) is arranged between the grounding ends of the constant current loop, and the sampling voltage Vsns can be acquired from the end of the sampling resistor (Rsns); the second reference voltage (Vref3) is a reference voltage Vsns supplied from the constant current loop. The sampling voltage Vsns and the second reference voltage Vref3 may be used as two input signals of the constant current loop, and when the sampling voltage Vsns is smaller than the second reference voltage Vref3, it may indicate that the load current is smaller than a preset overcurrent threshold, at this time, the constant current loop does not operate, and the output current (Iout) of the circuit may 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, which indicates that the load current is greater than the predetermined overcurrent threshold, the constant current loop starts to operate, and the constant current loop may control the sampling voltage Vsns to be equal to the second reference voltage Vref 3.
The input end of the feedback loop is connected with the output end of the constant current loop and is used for receiving the output voltage of the constant current loop, and the feedback loop is provided with two input ends, and the two input ends can respectively receive the output voltage (Vout) and the output detection voltage (Vout-sns). 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 accurate sampling proportion.
In the embodiment of the invention, the sampled input voltage and output voltage are firstly used as two input signals of the overcurrent comparator, and the voltage difference V between the input voltage and the output voltage is directly calculatedIN -VOUTApplying a voltage difference VIN-VOUTThe voltage is compared with a first reference voltage Vref2, whether the overcurrent comparator is turned over or not is controlled according to the comparison result, and therefore, the influence of the voltage on the overcurrent threshold value when the components in the constant current loop and the feedback loop are out of regulation can be reduced by detecting the voltage, and the high-precision overcurrent threshold value is obtained; and the structure is simple and easy to realize.
Example two
In the embodiment of the present invention, based on the first specific embodiment, the present invention further includes a filter circuit 5, where one end of the filter circuit 5 is connected to the constant current loop and the feedback loop, and the other end is grounded.
The filter circuit 5 can guarantee stable output voltage to the interference wave in the filtering circuit. The filter circuit 5 comprises a first voltage-dividing resistor and a filter capacitor, wherein one end of the first voltage-dividing resistor is connected to the voltage output end of the constant current loop after being connected in parallel with the filter capacitor, and the other end of the first voltage-dividing resistor is grounded. Referring to fig. 3, the first voltage dividing resistor is Rout, and the filter capacitor is Cout.
Optionally, 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 a sampling resistor, an output end of the first operational amplifier is simultaneously connected to the logic control circuit, a control end of the second field effect transistor, and a control end of the third field effect transistor, an anode input end of the first operational amplifier is connected to an output end of the first field effect transistor and one end of the sampling resistor, and is configured to collect a sampling voltage, and a cathode input end of the first operational amplifier is configured to sample a second reference voltage Vref 3; the input end of the second field effect transistor is connected with the input end of the third field effect transistor and used for collecting input voltage.
Referring to fig. 3, the first operational amplifier is a2, the first fet is M1, the second fet is M0-SNS, the third fet 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 a power switch transistor and a sampling transistor at the same time. The grid electrodes (G poles) of the NMOS tube and the PMOS tube are control ends, the source electrode (S pole) of the NMOS tube and the drain electrode (D pole) of the PMOS tube are output ends, and the drain electrode (D pole) of the NMOS tube and the source electrode (S pole) of the PMOS tube are input ends.
Specifically, the first opamp 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 fet 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 a second reference voltage Vref 3. The output end 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, and after weak voltage is amplified, voltage signals are output to 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.
Optionally, the feedback loop includes a second operational amplifier, and the second operational amplifier forms a negative feedback loop in combination with the first fet.
Referring to fig. 3, 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 end of the second operational amplifier A1 is connected with 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 end of the second operational amplifier A1 is connected with the S pole of the third field effect transistor M0, and the output end of the second operational amplifier A1 is connected with the G pole of the first field effect transistor M1. The second operational amplifier forms a negative feedback loop between the a1 and the first fet M1, and the negative feedback loop can be used to stabilize the output voltage or gain, and also can extend the passband.
Specifically, the positive input terminal of the second op amp, a1, is connected to the S-pole of the second fet M0-SNS for sampling the output sense voltage (Vout-SNS), and the negative input terminal of the second op amp, a1, is connected to the S-pole of the third fet M0 for sampling the output voltage (Vout). And because the D pole of the first FET M1 is connected to the S pole of the second FET M0-SNS, and the positive input terminal of the second operational amplifier A1, the G pole of the first FET M1 is connected to the G pole of the first FET M1, the output voltage (Vout) can be stabilized by the negative feedback loop formed between the second operational amplifier A1 and the first FET M1, so that Vout-SNS is equal to Vout, but also due to the offset voltage V of the operational amplifier A1OSWill cause VOUT_SNS＝VOUT-VOSThe phenomenon of (2).
More specifically, the following is an operation principle of the over-current detection circuit provided by the embodiment:
when the input voltage and the output voltage sampled by the over-current comparator OCP Comp satisfy:
VIN-VOUT≥Vref2 (1)
over-current comparator OCP Comp flipAfter the normal operation is started, the logic control circuit can output a low level to the G electrode of the second FET M0-SNS and the third FET M0, so that the second FET M0-SNS and the third FET M0 are conducted (Vgs < Vt). The S pole of the second field effect transistor M0-SNS is connected with the D pole of the first field effect transistor M1 and outputs high level to be conducted, meanwhile, sampling current flows through a sampling resistor Rsns to obtain sampling voltage Vsns, when the sampling voltage and the second reference voltage meet the condition that the Vsns is more than or equal to Vref3, the first operational amplifier A2 starts to normally work, and a negative feedback loop formed by the sampling voltage and the second reference voltage and the M0_ SNS and the M1 enables the Vsns to be Vref3, and at the moment, the load current I is carried outOUTEqual to:
Figure BDA0002699675700000081
k is a sampling proportion coefficient of the second field effect transistor M0-SNS and the third field effect transistor M0, and the sampling proportion may be set to 1: K.
when the constant current loop starts to work, if the overcurrent threshold value I isOCPSmaller (meaning V)IN-VOUTSmaller) at this time VIN-VOUT＜Vref2The over-current comparator OCP Comp is not inverted; then the constant current loop works all the time, as the load is increased, VOUTVoltage drops and is at VIN-VOUT≥Vref2At this time, the over-current comparator OCP Comp is turned over, and the offset voltage V of the first operational amplifier a1 and the second operational amplifier a1 can be ignoredOSOver-current protection threshold I at this timeOCPComprises the following steps:
Figure BDA0002699675700000082
if the overcurrent threshold IOCPIs larger (meaning V)IN-VOUTLarge) when the offset voltage V can be ignoredOSFor over-current threshold IOCPThe formula (3) can also be obtained. So no matter the overcurrent threshold IOCPThe invention can avoid the influence caused by offset voltage Ios, thereby obtaining high precisionThe overcurrent threshold of (2).
In the embodiment of the invention, the input voltage and the output voltage are used as two input signals of the overcurrent comparator, and only when the electrical difference value V between the input voltage and the output voltageIN-VOUTThe over-current comparator can only flip when the first reference voltage Vref3 is reached. The influence of offset voltage of the operational amplifier on an overcurrent threshold is reduced through voltage detection, and certain offset of the amplifier in the circuit can be overcome, so that if the V of a power tube is subjected to overcurrent protectionIN-VOUTThe sampling current proportion has larger deviation when being smaller; with VOUTThe problem that the sampling current proportion is recovered to a normal value is reduced, and the phenomenon that the deviation of an over-current protection threshold IOCP is large and the IOCP variation range is large under different loads is avoided. The method can obtain the high-precision overcurrent threshold value, and has the advantages of simple structure, easiness in implementation and the like.
As a possible implementation manner, as shown in fig. 4, fig. 4 is a circuit diagram of another over-current detection circuit provided in an embodiment of the present invention. In addition to the above embodiments, the power supply 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.
After the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 are connected in series, one end of the first voltage-dividing resistor R1 is connected to the S pole of the third fet M0, the positive input end of the second amplifier a1, and the filter circuit 5, and the other end is grounded. An 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 can be used as an input signal of the positive input end of the over-current comparator.
After the third voltage dividing resistor R3 and the fourth voltage dividing resistor R4 are connected in series, one end of the third voltage dividing resistor R3 is connected with 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 of the third voltage dividing resistor R4 is grounded. An 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 can be used as an input signal of a negative electrode input end of the overcurrent comparator.
In this embodiment, the first fet M1 may be replaced by a PMOS transistor, and the second fet M0-SNS and the third fet M0 may 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 reversely connected.
Specifically, when:
Vin-div-Vout-div≥Vref3 (4)
the over-current comparator OCP Comp toggles. When the constant current loop starts to work, if the overcurrent threshold value I isOCPSmaller (meaning that Vin-div-Vout-div is smaller), when Vin-div-Vout-div < Vref3, overcurrent comparator OCP Comp does not flip; then the constant current loop works all the time, as the load is increased, VOUTThe voltage drops, and when Vin-div-Vout-div is not less than Vref3, the over-current comparator OCP Comp is turned over, and the voltage V can be unregulatedOSOver-current protection threshold IOCPAs shown in formula (3) above.
And if the overcurrent threshold IOCPLarger (meaning that Vin-div-Vout-div is larger), when the detuned voltage V can be ignoredOSTo IOCPThe formula (3) can also be obtained. Therefore no matter IOCPThe height of the invention can obtain the high-precision overcurrent threshold value from beginning to end.
In the embodiment of the invention, the sampled input voltage and output voltage are firstly used as two input signals of the overcurrent comparator, and the voltage difference V is obtained by directly calculating the voltage difference between the input voltage and the output voltageIN-VOUTAnd comparing the current with a first reference voltage Vref2, and controlling whether the overcurrent comparator is overturned according to the comparison result. Therefore, by detecting the voltage, the influence of the voltage on the overcurrent threshold value when the components in the constant current loop and the feedback loop are out of regulation can be reduced, and the high-precision overcurrent threshold value is obtained; and the structure is simple and easy to realize.
EXAMPLE III
The invention also provides a battery protection device which comprises the overcurrent detection circuit in any one of the embodiments.
In this embodiment, the battery protection device can be used for a lithium batteryAnd the front end carries out overcurrent protection. Since the battery protection device comprises any over-current detection circuit, the current detection circuit uses the sampled input voltage and output voltage as two input signals of the over-current comparator, and directly calculates the voltage difference between the input voltage and the output voltage to obtain the voltage difference VIN-VOUTThe voltage is compared with a first reference voltage Vref2, whether the overcurrent comparator is turned over or not is controlled according to the comparison result, and therefore, the influence of the offset voltage of components in a constant current loop and a feedback loop on the overcurrent threshold can be reduced by detecting the voltage, and the high-precision overcurrent threshold is obtained; and the structure is simple and easy to realize. The battery protection device also has the above-described effects.
The terms "including" and "having," and any variations thereof, in the description and claims of this application and the description of the figures are intended to cover non-exclusive inclusions. The terms "first," "second," and the like in the description and claims of this application or the accompanying drawings are used for distinguishing between different objects and not for describing a particular order. Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.
The present invention is not limited to the above preferred embodiments, but includes all modifications, equivalents, and improvements within the spirit and scope of the present invention.

Claims (10)

1. An over-current detection circuit, comprising: the overcurrent protection circuit comprises an overcurrent comparator, a logic control circuit, a constant current loop and a feedback loop;
the overcurrent comparator is used for receiving the sampled input voltage and output voltage as input signals and controlling whether the overcurrent comparator is turned over or not according to a comparison result of a voltage difference between the input voltage and the output voltage and a first reference voltage;
the logic control circuit is used for receiving the output signal of the over-current comparator and controlling the on-off of the constant current loop according to the output signal;
the constant current loop is used for determining the current of the sampling resistor according to the sampled sampling voltage and the second reference voltage;
the feedback loop is used for sampling the output voltage of the constant current loop and outputting the detection voltage, and controlling the output voltage to be equal to the output detection voltage.
2. The over-current detection circuit of claim 1, further comprising a filter circuit, one end of the filter circuit being connected to the constant current loop and the feedback loop, the other end being grounded.
3. The over-current detection circuit as claimed in claim 2, wherein the filter circuit comprises a first voltage dividing resistor and a filter capacitor, the first voltage dividing resistor is connected in parallel with the filter capacitor, and then one end of the first voltage dividing resistor is connected to the voltage output end of the constant current loop, and the other end of the first voltage dividing resistor is grounded.
4. The over-current detection circuit of claim 1, wherein the over-current comparator comprises a positive input terminal and a negative input terminal, the positive input terminal receiving the sampled input voltage, the negative input terminal receiving the sampled output voltage.
5. The overcurrent detection circuit according to claim 1, wherein 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, an output terminal of the first operational amplifier is simultaneously connected to the logic control circuit, a control terminal of the second field effect transistor, and a control terminal of the third field effect transistor, an anode input terminal of the first operational amplifier is connected to an output terminal of the first field effect transistor and one terminal of the sampling resistor, and is configured to sample the sampling voltage, and a cathode input terminal of the first operational amplifier is configured to sample the second reference voltage; and the input end of the second field effect transistor is connected with the input end of the third field effect transistor and is used for collecting the input voltage.
6. The over-current detection circuit of claim 1, wherein the feedback loop comprises a second op amp that forms a negative feedback loop in conjunction with the first fet.
7. The over-current detection circuit as claimed in claim 6, wherein an output terminal of the second operational amplifier is connected to the control terminal of the first fet, an anode input terminal of the second operational amplifier is connected to the output terminal of the second fet for sampling the output detection voltage, a cathode input terminal of the second operational amplifier is connected to the output terminal of the third fet for sampling the output voltage, and an input terminal of the first fet is connected to the output terminal of the second fet and the anode input terminal of the second operational amplifier.
8. The over-current detection circuit of claim 5, wherein the first field effect transistor is an NMOS transistor, and the second field effect transistor and the third field effect transistor are PMOS transistors.
9. The over-current detection circuit of claim 8, wherein the control terminals of the first, second and third fets are the gates of the NMOS and PMOS transistors, the output terminal of the first fet is the source of the NMOS transistor, the input terminal is the drain of the NMOS transistor, the output terminals of the second and third fets are the drains of the PMOS transistors, and the input terminal is the source of the PMOS transistor.
10. A battery protection device comprising the overcurrent detection circuit as set forth in any one of claims 1 to 9.
CN202011017821.8A 2020-09-24 2020-09-24 Overcurrent detection circuit and battery protection device Pending CN112271764A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112967686A (en) * 2021-02-09 2021-06-15 厦门天马微电子有限公司 Light-emitting structure, display panel, backlight module and display device
CN113092836A (en) * 2021-04-14 2021-07-09 山东英信计算机技术有限公司 Circuit and method for realizing reliable protection of load circuit
CN114204534A (en) * 2022-02-15 2022-03-18 深圳市思远半导体有限公司 Overvoltage and overcurrent protection circuit, lithium battery charger front-end circuit and starting method

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112967686A (en) * 2021-02-09 2021-06-15 厦门天马微电子有限公司 Light-emitting structure, display panel, backlight module and display device
CN113092836A (en) * 2021-04-14 2021-07-09 山东英信计算机技术有限公司 Circuit and method for realizing reliable protection of load circuit
CN114204534A (en) * 2022-02-15 2022-03-18 深圳市思远半导体有限公司 Overvoltage and overcurrent protection circuit, lithium battery charger front-end circuit and starting method

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