MOSFET Battery Current Sensing With Temperature Compensation
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Solution Overview
Problem
Conventional battery current measuring devices rely on shunt resistors, which occupy significant volume and increase costs, making them inefficient for precise current measurement.
Innovation Solution
A battery current measuring device that uses a semiconductor switch, such as a MOSFET, with a temperature compensation unit featuring a diode structure to accurately measure current without a shunt resistor, by compensating for resistance changes due to temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a shunt resistor is used to measure battery current, then measurement precision is improved, but device volume increases and manufacturing cost increases
Solution Approach 1:
The patent extracts the current measurement function from the traditional shunt resistor approach and relocates it to the existing MOSFET switch. By measuring the voltage across the MOSFET's drain-source terminals and calculating current through the controller, the system eliminates the need for a separate shunt resistor, thereby reducing device volume while maintaining measurement precision
Solution Approach 2:
The MOSFET switch is given multiple functions: it serves both as the charging/discharging control switch and as the current sensing element. The same MOSFET that controls battery current flow also provides the voltage signal for current measurement, eliminating the need for dedicated shunt resistor components
2Measurement precision
If a shunt resistor is used to measure battery current, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the shunt resistor component from the bill of materials and extracts its measurement function into the controller's processing capability. The controller reads voltage across the MOSFET and calculates current, eliminating the need to purchase and assemble separate precision resistor components, thereby reducing manufacturing cost
Solution Approach 2:
The patent replaces the physical shunt resistor hardware with an electronic measurement approach using the MOSFET's inherent voltage characteristics. The controller performs digital calculation of current based on voltage measurement, substituting physical measurement hardware with electronic sensing and computational processing
3Measurement precision
If a shunt resistor is used to measure battery current, then measurement precision is improved, but assembly process complexity increases
Solution Approach 1:
The patent extracts the current measurement function from a separate shunt resistor assembly and integrates it into the existing MOSFET switch structure. This eliminates separate assembly steps for installing and wiring a shunt resistor, reducing assembly process complexity while maintaining measurement capability
Solution Approach 2:
The patent merges the current measurement function with the existing MOSFET switch assembly. The voltage measurement across the MOSFET and the current calculation are combined into a single integrated process within the controller, eliminating the need for separate shunt resistor installation and wiring assembly steps
4Measurement precision
If temperature compensation is added to compensate for resistance change, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent implements temperature compensation by measuring the MOSFET's temperature and using this information to adjust the current calculation. The controller reads temperature data and applies compensation algorithms to correct for temperature-induced resistance changes, improving measurement precision through feedback-based correction
Solution Approach 2:
The patent changes the measurement parameters by incorporating temperature as an additional measured variable. The controller adjusts calculation parameters based on temperature readings, compensating for resistance changes due to temperature variations and improving current measurement accuracy across different operating conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution reduces volume and cost while achieving precise current measurement, enabling efficient battery current monitoring without the need for shunt resistors.
Implementation Method 1
a temperature compensation unit having a diode structure capable of compensating for a resistance change according to a change of temperature of the switch
Implementation Method 2
the diode structure of the temperature compensation unit includes a plurality of diodes, and a number of the plurality of diodes and a connection configuration of the plurality of diodes are adapted to have a temperature-resistance curve matching a temperature-resistance curve of the switch
Implementation Method 3
an A/D converter configured to convert a voltage value across the switch into a digital value
Implementation Method 4
a controller configured to calculate a current flowing through the switch based on the digital value of the voltage value, and the A/D converter is configured to convert the voltage value of the switch into the digital value using a reference voltage inputted from the temperature compensation unit
Data Source
AI summary
A battery current measuring device includes a switching element configured to control charging and discharging of a battery, an A/D converter configured to convert a voltage value across the switching element into a digital value, a temperature compensation unit having a diode structure capable of compensating for a resistance change according to a change of temperature of the switching element, and a current calculation unit configured to calculate a current flowing through the switching element based on the digital value of the voltage value, and the A/D converter converts the voltage value of the switching element into the digital value using a reference voltage inputted from the temperature compensation unit.