Flying capacitive series battery pack voltage detection device and control method

A series battery pack and voltage detection technology, which is applied in the direction of measurement using digital measurement technology, can solve the problems of power lithium battery pack equalization effect weakening, battery pack measurement accuracy is low, and battery service life is reduced, so as to solve the problem of resistance voltage division Low precision, low power consumption, and the effect of preventing high voltage shock

Inactive Publication Date: 2015-03-04
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AI-Extracted Technical Summary

Problems solved by technology

The 2V-4.2V voltage range of lithium-ion batteries accounts for more than 95% of the battery capacity. Therefore, in order to accurately measure the battery capacity, the measurement error of the battery voltage needs to reach about 1mV. There are many voltage measurement circuits for single-cell lithium-ion batteries in 4.2V Measuring only the range error of 2V can meet the requirements. However, since each single lithium-ion battery is used in series, the simple resistance voltage division method to measure the battery voltage will lead to the lower measurement accuracy of the battery pack with higher voltage.
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The invention provides a novel battery voltage detection device and a control method. A sampling resistor can be canceled in a battery voltage detection circuit with a triode switch, so that battery voltage measuring accuracy is improved. Two ends of a flying capacitor serve as input voltage, a single-end operational amplifier is used, battery voltage can be monitored by the aid of the low-cost amplifier, and a complicated differential amplifier is omitted. The battery voltage detection circuit is used for monitoring voltage of a plurality of serial batteries and has the advantages of rapidness in detection and high detection accuracy, a battery pack selects each battery through the triode switch, so that the battery voltage is further reduced through direction correction, voltage detection ranges are further narrowed, voltage detection accuracy is improved, and the voltage of each battery is calculated.

Application Domain

Measurement using digital techniques

Technology Topic

Differential amplifierElectrical battery +9


  • Flying capacitive series battery pack voltage detection device and control method


  • Experimental program(1)

Example Embodiment

[0017] Below, this embodiment is described with reference to accompanying drawing:
[0018] figure 1 It is a circuit diagram of a battery voltage detection circuit, and the implementation method of the present invention is illustrated by taking 6 lithium-ion batteries connected in series as an example, and the circuit is applicable to more battery pack applications.
[0019] The battery voltage detection circuit is composed of an operational amplifier unit, a direction selection unit, a multi-channel selection unit, and a battery pack unit; the operational amplifier unit mainly completes the functions of impedance matching and signal amplification.
[0020] The direction correction circuit is composed of T11-T14, T15, T18, R11, R14, which mainly completes the functions of direction switching and isolation of flying capacitors.
[0021] The multi-channel selection unit is composed of T21-T26, T31-T36, and R31-R34, which mainly completes the signal gating of single-cell battery voltage measurement. The connection method takes T36, T26, and R36 as examples to illustrate the single-way switch connection: T36 is connected to the input and output, R36 is connected to both ends of T26 as a bias resistor, T26 mainly realizes the switch control of T36, and when P1.6 is high, T36 is turned on , When P1.6 is low, 36 is closed, so as to realize the switching action of T36 (the principle of T31-T36 is the same). The battery signal gating control is completed through the T31-T36 switch circuit, because the output of the triodes of T31-T36 is connected to the odd-numbered tubes (connected to the outputs of T31, T33, and T35); connected to the even-numbered tubes (connected to the outputs of T32, T34, and T36 ); so when you choose to measure the voltage of even cells, the output of even transistors is positive, and the output of odd transistors is negative; when you choose to measure the voltage of odd cells, the output of odd transistors is positive, and the output of even transistors is negative; The triode can choose to measure the battery voltage of the nth channel. If n is an even number, the output is a positive battery voltage, and if n is an odd number, the output is a negative battery voltage.
[0022] The positive and negative poles of all the batteries in the battery unit are connected end to end, and each connection terminal is connected to the switch triode (T31-T36). This connection allows the triode to select and measure the voltage of any battery.
[0023] Voltage detection control method:
[0024] 1. Turn off the switches of all direction correction units by making P2.1-P2.4 all low;
[0025] 2. Select the battery cells to be measured through the multi-channel selection unit. If an even number of battery cells is selected, the forward battery voltage will be output, and if an odd number of battery cells is selected, the reverse battery voltage will be output.
[0026] 3. Keep the control state of the multi-channel selection unit (P1.1-P1.6 determines which output), and charge the capacitor C;
[0027] 4. Turn off all control signals P1.1-P1.6 of the multiplexing unit
[0028] 5. If C is charged with positive voltage, turn on T18 and T13 (P2.1\P2.2 is turned on); if C is charged with negative voltage, turn on T15 and T12 (P2.3\P2.4 is turned on);
[0029] 6. A/D can collect VBAT to get the voltage we measured;
[0030] This measurement circuit control method; because the voltage lost on the multiplex switch is relatively fixed at 0.6V
[0031] The direction selection unit has no signal loss, so the voltage we tested is battery voltage -0.6V, so that the ADC can further narrow the sampling range and further improve the measurement accuracy.


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