[introduction] use sensor measures the different power in circuit when relevant parameter, can encounter different challenge. Main challenge is to maintain the electric segregation between sensor and power source circuit, affect in order to prevent wave motion of power source circuit to what measure. Efficient segregation still conduces to the measurement in maintaining circuit of high frequency switch precision, this circuit is carried the influence of the noise that road of ground connection annulus produces extremely easily by these high frequency switch.

Because world each country develops prospective attention to can lasting, mixture motivation car and pure electric car appeared to grow quickly nearly. A lot of electron component and power cell synchronism work to run electric car in order to succeed in coordination. Power source module is located in the different position all round car, the segregation voltage that needs to measure these module in real time and electric current in order to undertake continuous monitoring. A few main module in EV include a car to hold system of charger, batteries management (inverter of system of BMS) , HVAC, drawing and DC/DC converter. Must the accurate electric current that monitor and voltage value move normally with ensuring.

The article is the speech summary of John Wilson of manager of Skyworks product line. Wilson explained measure the value that moves with ensuring with the voltage in monitoring EV and electric current effectively. He undertakes metrical layinged a foundation to how be in high-pressured circuit above all.

Measure reach its goal

To monitor module the voltage of two end is mixed the electric current that has shed it, electric current and voltage sensor are placed the proper place in circuit. For example, to measure the electric current that has circulated batteries set, voltaic sensor measures resistor of series connection billabong the voltage of two end generates output signal, this signal and the voltaic size of the flow in circuit become direct ratio. Same, to survey batteries group the voltage of two end, voltage sensor can detect voltage of this bits is generated output with voltage proportionate. Send these sensor reading BMS next, what make efficient operation by BMS next is decision-making. The different module in car needs to come from what node differs all round car to measure, charge in order to undertake feedback, control, safety is mixed the level is evaluated.

Use sensor measures the different power in circuit when relevant parameter, can encounter different challenge. Main challenge is to maintain the electric segregation between sensor and power source circuit, affect in order to prevent wave motion of power source circuit to what measure. Efficient segregation still conduces to the measurement in maintaining circuit of high frequency switch precision, this circuit is carried the influence of the noise that road of ground connection annulus produces extremely easily by these high frequency switch. Low the temperature that answers time and wave motion also can affect measured accuracy. Segregation still conduces to n changeover, going up to run two logistic n independently with a circuit board namely. Most module uses the capacitance coupling that is based on CMOS to cross segregation border to undertake signal coupling.

Measure a process to understand better, wilson showed group of batteries of ion of lithium of monitoring of a BMS, among them the voltage of two batteries and electric running water make the same score monitoring of IC of two batteries management. An extra voltage and voltaic supervisory system allow whole system to maintain safety and redundant. Advocate BMS measures systematic voltage through voltage divider circuit and voltage sensor, if pursue,1 is shown. Single cell measured value also is sent go in order to enter to BMS farther monitoring. All sensor and each BMS are segregation.

Graph 1: The voltage in BMS and electric current are measured

Measure wrong consequence

The accuracy when deciding all sorts of system parameter is very important to the function of EV. Inaccurate is measured can cause inconvenience, cause danger and accident even. Because voltage and electric current are measured not accurate and a few common problems that cause include travel course of development and batteries to charge wrong estimation of the level, complete temperature of the wrong estimation of odd time, practical railroad car and place require railroad car temperature between do not match, and to batteries be pressed too or owe the module after pressing DC/DC to change. Although withhold a few functions such as charge level and bracer to be able to be helped,solve these problems, but the solution that they are not a gender, be necessary to solve the prime cause of the problem.

What may produce two kinds of main types is wrong: Static mistake and trends are wrong. When difference exists between real value and the measured value that measure the sensor of static state or slow change parameter, can appear static receiver error. When sensor measures the parameter that suffers noise effect lack fidelity or easily, error of meeting occurrence trends. Static receiver error includes gain error, maladjusted sum of errors nonlinear. To measure the different component of static receiver error effectively, need is their changeover standard unit, in the BMS of EV, standard unit is the full scale per cent of batteries n. Beg to these errors square root and, represent data with the exact pattern on statistic.

The main system that other need surveys is the car carries charge inverter of converter of system, DC/DC, drawing and HVAC system. To these systems each medium, the different level that changes in power measures power parameter, mix in order to keep redundant accuracy.

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