1. Introduction
In electronic circuit design, accurate detection of current is key to ensuring system performance and safety. Current detection technology can be divided into detection based on magnetic field and detection based on resistance shunt (sampling resistor) according to its detection principle. Detection based on magnetic fields, such as current transformers and Hall sensors, are widely used in drive technology and high current measurement situations that require high safety standards because of their excellent electrical isolation performance and low power consumption. However, disadvantages of this type of approach include larger volumes, less than ideal compensation characteristics, linearity, and temperature dependence. With the development of miniaturized high-precision low-resistance resistor technology and the advancement of data acquisition and processing technology, the current detection method based on shunts (sampling resistors) has been innovated, providing possibilities for new application fields.
The sampling resistor, as the core component of current detection, has a resistance value usually lower than 1 ohm. This type of resistor is connected in series in the circuit and uses Ohm's law to convert the current through the resistor into a voltage signal for measurement, making current monitoring easy and efficient.
2. Application fields of sampling resistors
Sampling resistors play an irreplaceable role in fields such as power management and switching power supplies (SMPS). In power monitoring systems, sampling resistors are used to accurately measure current to ensure that the system operates in a safe and optimal state. For example, in the design of lithium battery charging circuits, sampling resistors are used to control the charging current to ensure safe charging of the battery and extend its service life. Linear Technology's 4100 series lithium battery charging circuit is a typical application example, demonstrating the importance of sampling resistors in modern power management systems.
3. Select the appropriate sampling resistor
Choosing the appropriate sampling resistor is crucial to ensure the accuracy of current detection and the reliability of the circuit. The accuracy of precision resistors is usually within 1%. For applications with higher requirements, resistors with accuracy as high as 0.05% or 0.01% can be selected. In addition, the power ratings of the sampling resistors are also different according to different application requirements. Common power ratings include 0.25W, 0.5W, 1W, etc.
The selection of the standard resistance value needs to consider the actual application environment of the resistor. Common standard resistance values include 0.001 ohm (expressed as R001), 0.025 ohm (expressed as R025), etc. The choice of package form is also an important consideration, including common sizes such as 1206, 2010, and 2512 to adapt to different installation needs.