A high-precision micro-current sampling device and method

Abstract

The present invention provides a high-precision micro-current sampling device and method in the field of lithium battery technology. The device includes an MCU, a current sampling circuit, an onboard power supply, a noise-free power supply, a switch K1 and a switch K2; one end of the current sampling circuit is connected to the MCU, and the other end is connected to the switch K1 and the switch K2; the onboard power supply is connected to the switch K1; the noise-free power supply is connected to the switch K2; the switch K1, the switch K2 and the onboard power supply are all connected to the MCU. The advantages of the present invention are: the sampling accuracy of micro-current is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a high-precision micro-current sampling device and method. Background Art

[0002] Lithium batteries are a type of battery that uses lithium metal or lithium alloy as positive / negative electrode materials and non-aqueous electrolyte solutions. Due to the advantages of lithium batteries such as high energy ratio, long service life, high rated voltage, high power tolerance, light weight, strong adaptability to high and low temperatures, green environmental protection, and basically no water consumption in production, they have gradually developed into mainstream batteries and are widely used in new energy vehicles and other fields.

[0003] Since lithium batteries are equipped with BMS and other devices to monitor parameters such as voltage, current, and temperature, lithium batteries also consume power when in standby mode. With the advancement of technology, the standby power consumption of lithium batteries is getting lower and lower. In order to ensure the safety of lithium batteries during use, a series of tests need to be performed on lithium batteries using test equipment before they leave the factory. As the standby power consumption of lithium batteries is getting lower and lower, higher requirements are placed on the measurement accuracy of the test equipment, that is, higher current sampling accuracy needs to be provided to ensure the performance of the lithium battery protection board.

[0004] However, the onboard power supply of traditional test equipment has high power ripple and noise due to the multi-stage power conversion process, which in turn affects the current sampling accuracy. Therefore, how to provide a high-precision micro-current sampling device and method to improve the micro-current sampling accuracy has become an urgent problem to be solved. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a high-precision microcurrent sampling device and method to improve the sampling accuracy of microcurrent.

[0006] In a first aspect, the present invention provides a high-precision micro-current sampling device, including an MCU, a current sampling circuit, an onboard power supply, a noise-free power supply, a switch K1, and a switch K2;

[0007] One end of the current sampling circuit is connected to the MCU, and the other end is connected to the switch K1 and the switch K2; the onboard power supply is connected to the switch K1; the noise-free power supply is connected to the switch K2; the switch K1, the switch K2 and the onboard power supply are all connected to the MCU.

[0008] Further, the current sampling circuit includes an analog-to-digital conversion chip U2, an operational amplifier OPA2, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11 and a capacitor C3;

[0009] One end of the analog-to-digital conversion chip U2 is connected to the resistor R11, and the other end is connected to the MCU; after the resistor R10 is connected in parallel with the capacitor C3, one end is connected to the resistor R8 and the pin 2 of the operational amplifier OPA2, and the other end is connected to the resistor R11 and the pin 3 of the operational amplifier OPA2; one end of the resistor R7 is connected to one end of the resistor R9 and the pin 1 of the operational amplifier OPA2, and the other end is connected to the switch K1; the other end of the resistor R9 is grounded.

[0010] Furthermore, the resistor R7, the resistor R8, the resistor R9 and the resistor R10 are all high-precision and low-temperature drift resistors.

[0011] Furthermore, it also includes a ripple noise detection circuit, a charger and a switch K3;

[0012] One end of the ripple noise detection circuit is connected to the onboard power supply, and the other end is connected to the MCU; one end of the charger is connected to the switch K3, and the other end is connected to the noise-free power supply; the switch K3 is connected to the onboard power supply and the MCU respectively.

[0013] Further, the ripple noise detection circuit includes an analog-to-digital conversion chip U1, an operational amplifier OPA1, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C1 and a capacitor C2;

[0014] One end of the analog-to-digital conversion chip U1 is connected to the resistor R6, and the other end is connected to the MCU; pin 1 of the operational amplifier OPA1 is connected to one end of the resistor R2 and the resistor R4, pin 2 is connected to the resistor R3 and the resistor R5, and pin 3 is connected to the resistor R5 and the resistor R6; one end of the capacitor C1 is connected to the resistor R1 and the resistor R2, and the other end is connected to the on-board power supply; one end of the capacitor C2 is connected to the resistor R1 and the resistor R3, and the other end is connected to the on-board power supply; the other end of the resistor R4 is grounded.

[0015] Furthermore, the resistor R2, the resistor R3, the resistor R4 and the resistor R5 are all high-precision and low-temperature drift resistors.

[0016] Furthermore, the noise-free power supply is a rechargeable battery, a non-rechargeable battery or a supercapacitor.

[0017] In a second aspect, the present invention provides a high-precision micro-current sampling method, comprising the following steps:

[0018] Step S10, MCU sets a power threshold and calculates the ripple noise upper limit;

[0019] Step S20, the MCU determines the type of current signal to be sampled based on the received detection instruction. If it is a large current signal, the process proceeds to step S30; if it is a micro current signal, the process proceeds to step S40;

[0020] Step S30: The MCU closes the switch K1, supplies power to the current sampling circuit through the onboard power supply, and then uses the current sampling circuit to sample the large current signal;

[0021] Step S40, the MCU detects the real-time noise value of the onboard power supply through the ripple noise detection circuit, and determines whether the real-time noise value is less than the ripple noise upper limit value. If so, the MCU closes the switch K1, and supplies power to the current sampling circuit through the onboard power supply, and then uses the current sampling circuit to sample the micro-current signal; if not, enter step S50;

[0022] Step S50, after the power threshold of the MCU verifies the power of the noise-free power supply, the switch K2 is closed, and the current sampling circuit is powered by the noise-free power supply, and then the current sampling circuit is used to sample the micro-current signal.

[0023] Furthermore, in step S10, the calculation formula of the ripple noise upper limit value is as follows:

[0024] Vrpmax=PSRRmax*(I max -I min )*R12*G;

[0025] PSRRmax=(Z*I min ) / (I max -I min );

[0026] G = R4 / R2;

[0027] Wherein, Vrpmax represents the upper limit of ripple noise; PSRRmax represents the maximum suppression ratio of ripple noise; I max Indicates the maximum range of the current sampling device test current; I min It represents the minimum range of the sampling current of the current sampling device; R12 represents the resistance value of the equivalent resistance of the external loop to be sampled; G represents the amplification factor of the operational amplifier OPA1; Z represents the accuracy of the sampling current of the current sampling device.

[0028] Furthermore, the step S50 is specifically as follows:

[0029] The MCU detects the power of the noise-free power supply and determines whether the power is greater than the power threshold. If so, the switch K2 is closed to supply power to the current sampling circuit through the noise-free power supply, and then the current sampling circuit is used to sample the micro-current signal.

[0030] If not, close switch K3, and the charger uses the onboard power supply to charge the noise-free power supply until the power of the noise-free power supply is greater than the power threshold, and then close switch K2 to power the current sampling circuit through the noise-free power supply, and then use the current sampling circuit to sample the micro-current signal.

[0031] The advantages of the present invention are:

[0032] 1. By setting a noise-free power supply, switch K1 and switch K2, the MCU can select a noise-free power supply or an onboard power supply to power the current sampling circuit through switches K1 and K2 based on specific detection instructions. That is, the onboard power supply is used to sample large current signals, and the noise-free power supply is used to sample micro-current signals, thereby avoiding the interference of ripple noise on the sampling of micro-current signals and greatly improving the sampling accuracy of micro-currents.

[0033] 2. The real-time noise value of the onboard power supply is detected by setting a ripple noise detection circuit. When the real-time noise value is less than the upper limit of the ripple noise, the onboard power supply is used to power the current sampling circuit. When the real-time noise value is greater than the upper limit of the ripple noise, the noise-free power supply is used to power the current sampling circuit. That is, the noise-free power supply is used only when the onboard power supply cannot meet the conditions, thereby greatly extending the service life of the noise-free power supply.

[0034] 3. By setting the charger and switch K3, when the MCU detects that the power of the noise-free power supply is less than the set power threshold, the switch K3 is closed, and the charger uses the onboard power supply to charge the noise-free power supply until the power of the noise-free power supply is greater than the power threshold. That is, the noise-free power supply is ensured to be greater than the power threshold before it is allowed to power the current sampling circuit, further improving the sampling accuracy of the micro-current.

[0035] 4. By setting the resistors R2, R3, R4, R5, R7, R8, R9 and R10 to be high-precision and low-temperature drift resistors, the sampling accuracy of the micro-current is further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

[0037] Figure 1 The invention discloses a circuit principle block diagram of a high-precision micro-current sampling device.

[0038] Figure 2 It is a circuit principle block diagram of the MCU of the present invention.

[0039] Figure 3 It is a circuit diagram of the ripple noise detection circuit of the present invention.

[0040] Figure 4 It is a circuit diagram of the current sampling circuit of the present invention.

[0041] Figure 5 The present invention is a flowchart of a high-precision micro-current sampling method.

[0042] Marking Description:

[0043] 100-A high-precision micro-current sampling device, 1-MCU, 2-current sampling circuit, 3-onboard power supply, 4-noise-free power supply, 5-ripple noise detection circuit, 6-charger. DETAILED DESCRIPTION

[0044] The technical solution in the embodiment of the present application has the following overall idea: a noise-free power supply 4, a switch K1 and a switch K2 are set, so that the MCU1 can select the noise-free power supply 4 or the onboard power supply 3 to power the current sampling circuit 2 through the switch K1 and the switch K2 based on the specific detection instruction, so as to avoid the interference of ripple noise on the sampling of micro-current signals, and ensure that the power of the noise-free power supply 4 is greater than the power threshold before it is allowed to power the current sampling circuit 2, so as to improve the sampling accuracy of the micro-current.

[0045] Please refer to Figures 1 to 5 As shown, a preferred embodiment of a high-precision micro-current sampling device 100 of the present invention includes an MCU1, a current sampling circuit 2, an onboard power supply 3, a noise-free power supply 4, a switch K1 and a switch K2; the MCU1 is used to detect the amount of the noise-free power supply 4, control the on and off of the switches K1, K2 and K3, and control the work of the ripple noise detection circuit 5 and the current sampling circuit 2. In the specific implementation, it is sufficient to select an MCU that can realize this function from the prior art, and it is not limited to any model, such as the STM32F103 series MCU of ST Company, and the control program is well known to those skilled in the art, which can be obtained by those skilled in the art without creative labor; the current sampling circuit 2 is used for current sampling; the onboard power supply 3 is used to power the MCU1 and the current sampling circuit 2, and there is a certain amount of ripple noise interference; the noise-free power supply 4 is used to power the current sampling circuit 2, and performs micro-current signal sampling, and is a power supply without ripple noise; the switch K1 is used to switch on and off the connection between the onboard power supply 3 and the current sampling circuit 2; the switch K2 is used to switch on and off the connection between the noise-free power supply 4 and the current sampling circuit 2.

[0046] One end of the current sampling circuit 2 is connected to MCU1, and the other end is connected to switch K1 and switch K2; the onboard power supply 3 is connected to switch K1; the noise-free power supply 4 is connected to switch K2; the switch K1, switch K2 and onboard power supply 3 are all connected to MCU1.

[0047] The current sampling circuit 2 includes an analog-to-digital conversion chip U2, an operational amplifier OPA2, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11 and a capacitor C3; the analog-to-digital conversion chip U2 is used to convert the collected analog signal into a digital signal; the operational amplifier OPA2 is used to amplify the signal collected by the analog-to-digital conversion chip U2;

[0048] One end of the analog-to-digital conversion chip U2 is connected to the resistor R11, and the other end is connected to the MCU1; after the resistor R10 is connected in parallel with the capacitor C3, one end is connected to the resistor R8 and the pin 2 of the operational amplifier OPA2, and the other end is connected to the resistor R11 and the pin 3 of the operational amplifier OPA2; one end of the resistor R7 is connected to one end of the resistor R9 and the pin 1 of the operational amplifier OPA2, and the other end is connected to the switch K1; the other end of the resistor R9 is grounded.

[0049] The resistors R7 , R8 , R9 and R10 are all high-precision and low-temperature drift resistors to improve the sampling accuracy of micro-current.

[0050] It also includes a ripple noise detection circuit 5, a charger 6 and a switch K3;

[0051] One end of the ripple noise detection circuit 5 is connected to the onboard power supply 3, and the other end is connected to the MCU1; one end of the charger 6 is connected to the switch K3, and the other end is connected to the noise-free power supply 4; the switch K3 is connected to the onboard power supply 3 and the MCU1 respectively.

[0052] The ripple noise detection circuit 5 includes an analog-to-digital conversion chip U1, an operational amplifier OPA1, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C1 and a capacitor C2; the analog-to-digital conversion chip U1 is used to convert the collected analog signal into a digital signal; the operational amplifier OPA1 is used to amplify the signal collected by the analog-to-digital conversion chip U1;

[0053] One end of the analog-to-digital conversion chip U1 is connected to the resistor R6, and the other end is connected to the MCU1; pin 1 of the operational amplifier OPA1 is connected to one end of the resistor R2 and the resistor R4, pin 2 is connected to the resistor R3 and the resistor R5, and pin 3 is connected to the resistor R5 and the resistor R6; one end of the capacitor C1 is connected to the resistor R1 and the resistor R2, and the other end is connected to the on-board power supply 3; one end of the capacitor C2 is connected to the resistor R1 and the resistor R3, and the other end is connected to the on-board power supply 3; the other end of the resistor R4 is grounded.

[0054] The resistor R2, the resistor R3, the resistor R4 and the resistor R5 are all high-precision and low-temperature drift resistors to improve the sampling accuracy of micro-current.

[0055] The noise-free power supply 4 is a rechargeable battery, a non-rechargeable battery or a supercapacitor, providing a variety of power supply modes.

[0056] A preferred embodiment of a high-precision micro-current sampling method of the present invention comprises the following steps:

[0057] Step S10, MCU sets a power threshold and calculates the ripple noise upper limit;

[0058] Step S20, the MCU determines the type of current signal to be sampled based on the received detection instruction. If it is a large current signal, the process proceeds to step S30; if it is a micro current signal, the process proceeds to step S40;

[0059] Step S30: The MCU closes the switch K1, and supplies power to the current sampling circuit through the onboard power supply, and then uses the current sampling circuit to sample the large current signal; since the influence of ripple noise on the large current signal is minimal, the onboard power supply can be directly used for power supply;

[0060] Step S40, the MCU detects the real-time noise value of the onboard power supply through the ripple noise detection circuit, and determines whether the real-time noise value is less than the ripple noise upper limit value. If so, the MCU closes the switch K1, and supplies power to the current sampling circuit through the onboard power supply, and then uses the current sampling circuit to sample the micro-current signal; if not, enter step S50;

[0061] Step S50, after the power threshold of the MCU verifies the power of the noise-free power supply, the switch K2 is closed, and the current sampling circuit is powered by the noise-free power supply, and then the current sampling circuit is used to sample the micro-current signal.

[0062] By setting up a ripple noise detection circuit to detect the real-time noise value of the on-board power supply, when the real-time noise value is less than the ripple noise upper limit, the on-board power supply is used to power the current sampling circuit. When the real-time noise value is greater than the ripple noise upper limit, the noise-free power supply is used to power the current sampling circuit. That is, the noise-free power supply is used only when the on-board power supply cannot meet the conditions, thereby greatly extending the service life of the noise-free power supply.

[0063] In step S10, the calculation formula of the ripple noise upper limit value is as follows:

[0064] Vrpmax=PSRRmax*(I max -I min )*R12*G;

[0065] PSRRmax=(Z*I min ) / (I max -I min );

[0066] G = R4 / R2;

[0067] Wherein, Vrpmax represents the upper limit of ripple noise; PSRRmax represents the maximum suppression ratio of ripple noise; I max Indicates the maximum range of the current sampling device test current; I min It represents the minimum range of the sampling current of the current sampling device; R12 represents the resistance value of the equivalent resistance of the external loop to be sampled; G represents the amplification factor of the operational amplifier OPA1; Z represents the accuracy of the sampling current of the current sampling device.

[0068] The step S50 is specifically as follows:

[0069] The MCU detects the power of the noise-free power supply and determines whether the power is greater than the power threshold. If so, the switch K2 is closed to supply power to the current sampling circuit through the noise-free power supply, and then the current sampling circuit is used to sample the micro-current signal.

[0070] If not, close switch K3, and the charger uses the onboard power supply to charge the noise-free power supply until the power of the noise-free power supply is greater than the power threshold, and then close switch K2 to power the current sampling circuit through the noise-free power supply, and then use the current sampling circuit to sample the micro-current signal.

[0071] After the sampling is completed, the MCU turns off switch K1, switch K2, and switch K3.

[0072] In specific implementation, the switch K3, the charger and the ripple noise detection circuit are optional modules. When the switch K3, the charger and the ripple noise detection circuit are not set, the onboard power supply is directly used to sample large current signals, and the noise-free power supply is directly used to sample micro-current signals. When the power of the noise-free power supply is less than the set power threshold, since the noise-free power supply is a rechargeable battery, a non-rechargeable battery or a supercapacitor, the noise-free power supply needs to be charged or replaced.

[0073] In summary, the advantages of the present invention are:

[0074] 1. By setting a noise-free power supply, switch K1 and switch K2, the MCU can select a noise-free power supply or an onboard power supply to power the current sampling circuit through switches K1 and K2 based on specific detection instructions. That is, the onboard power supply is used to sample large current signals, and the noise-free power supply is used to sample micro-current signals, thereby avoiding the interference of ripple noise on the sampling of micro-current signals and greatly improving the sampling accuracy of micro-currents.

[0075] 2. The real-time noise value of the onboard power supply is detected by setting a ripple noise detection circuit. When the real-time noise value is less than the upper limit of the ripple noise, the onboard power supply is used to power the current sampling circuit. When the real-time noise value is greater than the upper limit of the ripple noise, the noise-free power supply is used to power the current sampling circuit. That is, the noise-free power supply is used only when the onboard power supply cannot meet the conditions, thereby greatly extending the service life of the noise-free power supply.

[0076] 3. By setting the charger and switch K3, when the MCU detects that the power of the noise-free power supply is less than the set power threshold, the switch K3 is closed, and the charger uses the onboard power supply to charge the noise-free power supply until the power of the noise-free power supply is greater than the power threshold. That is, the noise-free power supply is ensured to be greater than the power threshold before it is allowed to power the current sampling circuit, further improving the sampling accuracy of the micro-current.

[0077] 4. By setting the resistors R2, R3, R4, R5, R7, R8, R9 and R10 to be high-precision and low-temperature drift resistors, the sampling accuracy of the micro-current is further improved.

[0078] Although the specific implementation modes of the present invention are described above, those skilled in the art should understand that the specific implementation modes described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A high-precision micro-current sampling method, characterized in that: The method requires the use of a high-precision micro-current sampling device as follows, including an MCU, a current sampling circuit, an onboard power supply, a noise-free power supply, a switch K1 and a switch K2; One end of the current sampling circuit is connected to the MCU, and the other end is connected to the switch K1 and the switch K2; The onboard power supply is connected to the switch K1; the noise-free power supply is connected to the switch K2; the switch K1, the switch K2 and the onboard power supply are all connected to the MCU; The current sampling circuit includes an analog-to-digital conversion chip U2, an operational amplifier OPA2, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11 and a capacitor C3; One end of the analog-to-digital conversion chip U2 is connected to one end of the resistor R11, and the other end is connected to the MCU; after the resistor R10 is connected in parallel with the capacitor C3, one end is connected to one end of the resistor R8 and the negative input terminal of the operational amplifier OPA2, and the other end is connected to the other end of the resistor R11 and the output terminal of the operational amplifier OPA2; one end of the resistor R7 is connected to one end of the resistor R9 and the positive input terminal of the operational amplifier OPA2; the other end of the resistor R9 is grounded; the other end of the resistor R7 is connected to the positive electrode of the external loop, and the other end of the resistor R8 is connected to the negative electrode of the external loop; The resistors R7, R8, R9 and R10 are all high-precision low-temperature drift resistors; It also includes a ripple noise detection circuit, a charger and a switch K3; One end of the ripple noise detection circuit is connected to the onboard power supply, and the other end is connected to the MCU; one end of the charger is connected to the switch K3, and the other end is connected to the noise-free power supply; the switch K3 is connected to the onboard power supply and the MCU respectively; The ripple noise detection circuit includes an analog-to-digital conversion chip U1, an operational amplifier OPA1, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C1 and a capacitor C2; One end of the analog-to-digital conversion chip U1 is connected to one end of the resistor R6, and the other end is connected to the MCU; the positive input terminal of the operational amplifier OPA1 is connected to one end of the resistor R2 and the resistor R4, the negative input terminal is connected to one end of the resistor R3 and the resistor R5, and the output terminal is connected to the other end of the resistor R5 and the resistor R6; one end of the capacitor C1 is connected to one end of the resistor R1 and the other end of the resistor R2, and the other end is connected to the positive electrode of the onboard power supply; one end of the capacitor C2 is connected to the other end of the resistor R1 and the other end of the resistor R3, and the other end is connected to the negative electrode of the onboard power supply; the other end of the resistor R4 is grounded; The resistors R2, R3, R4 and R5 are all high-precision low-temperature drift resistors; The noise-free power supply is a rechargeable battery or a supercapacitor; The method comprises the following steps: Step S10, MCU sets a power threshold and calculates the ripple noise upper limit; Step S20, the MCU determines the type of current signal to be sampled based on the received detection instruction. If it is a large current signal, the process proceeds to step S30; if it is a micro current signal, the process proceeds to step S40; Step S30: The MCU closes the switch K1, supplies power to the current sampling circuit through the onboard power supply, and then uses the current sampling circuit to sample the large current signal; Step S40, the MCU detects the real-time noise value of the onboard power supply through the ripple noise detection circuit, and determines whether the real-time noise value is less than the ripple noise upper limit value. If so, the MCU closes the switch K1, supplies power to the current sampling circuit through the onboard power supply, and then uses the current sampling circuit to sample the micro-current signal; If not, proceed to step S50; In step S50, after the MCU verifies the power of the noise-free power supply based on the power threshold, the switch K2 is closed to supply power to the current sampling circuit through the noise-free power supply, and then the current sampling circuit is used to sample the micro-current signal.

2. A high-precision micro-current sampling method as claimed in claim 1, characterized in that: In step S10, the calculation formula of the ripple noise upper limit value is as follows: Vrpmax=PSRRmax*(I max -I min )*R12*G; PSRRmax=(Z*I min ) / (I max -I min ); G = R4 / R2; Wherein, Vrpmax represents the upper limit of ripple noise; PSRRmax represents the maximum suppression ratio of ripple noise; I max Indicates the maximum range of the current sampling device test current; I min It represents the minimum range of the sampling current of the current sampling device; R12 represents the resistance value of the equivalent resistance of the external loop to be sampled; G represents the amplification factor of the operational amplifier OPA1; Z represents the accuracy of the sampling current of the current sampling device.

3. A high-precision micro-current sampling method as claimed in claim 1, characterized in that: The step S50 is specifically as follows: The MCU detects the power of the noise-free power supply and determines whether the power is greater than the power threshold. If so, the switch K2 is closed to supply power to the current sampling circuit through the noise-free power supply, and then the current sampling circuit is used to sample the micro-current signal. If not, close switch K3, and the charger uses the onboard power supply to charge the noise-free power supply until the power of the noise-free power supply is greater than the power threshold, and then close switch K2 to power the current sampling circuit through the noise-free power supply, and then use the current sampling circuit to sample the micro-current signal.

Images