Capacitor is a passibe element used to store charge, store energy and filter signals in a circuit. Capacitors play an important role in power supply design. They can be used to stabilize current, reduce noise, filter high-frequency interference, etc.
When selecting capacitance, the following factors should be considered:
1、 Selection of capacitor type
1. Electrolytic capacitor: It has high capacitance characteristics and is suitable for filtering, bypass and energy storage in low-frequency circuits. However, it is not suitable for high-precision circuits because of its large leakage current.
2. Ceramic capacitor: small size, good CDSOD323-T05C High frequency characteristics, suitable for decoupling and filtering of high frequency signals.
3. Tantalum capacitor: It has stable capacitive performance and small leakage current, and is suitable for use as the bypass capacitor of stable power supply.
4. Film capacitance: It has good temperature and frequency characteristics and is suitable for high-frequency and precision circuits.
2、 Selection of capacity value and capacity
1. It shall be determined according to the circuit demand: the selection of capacitance value shall be based on the specific requirements of the circuit, such as filtering frequency, decoupling requirements, etc.
2. Safety margin: when determining the capacity value, a certain safety margin should be considered, which is generally 1.5 to 2 times of the actual demand.
3、 Selection of voltage level
1. Selection principle: the rated voltage of capacitor shall be higher than the highest working voltage in the circuit. Generally, it is recommended that the rated voltage be at least 1.5 times of the working voltage.
2. Temperature and aging factors shall be taken into consideration: temperature rise and long-term use will lead to a decline in the capacity of the capacitor voltage, so certain reserves shall be made in the selection.
4、 Consideration of temperature characteristics
1. Temperature coefficient: the stability of capacitance value of different types of capacitors is different under temperature change, and appropriate types need to be selected according to the actual application environment.
2. Operating temperature range: ensure that the capacitor can work normally at the expected ambient temperature.
5、 Consideration of frequency characteristics
1. High frequency application: For high frequency circuits, capacitors with good high frequency characteristics, such as ceramic capacitors, should be selected.
2. Low frequency applications: electrolytic capacitors can be used for filtering and energy storage in low frequency or DC applications.
6、 Failure efficiency and reliability
1. Failure rate: selecting capacitors with low failure rate can improve the overall reliability of the circuit.
2. Brand and manufacturer: select well-known brands and reputable manufacturers, which can indirectly guarantee the quality and reliability of capacitors.
7、 Size and installation method
1. Space limitation: Select capacitors of appropriate size according to PCB layout and space limitation.
2. Installation method: according to the actual needs, select the capacitors with different installation methods, such as patch type or plug-in type.
In a word, the selection of capacitor is a complex and detailed process in power supply design, which requires comprehensive consideration of many factors such as capacitor type, capacitance value, voltage grade, temperature characteristics, frequency characteristics, failure efficiency and reliability. Through careful selection and matching, the performance, stability and reliability of the power supply design can be ensured to meet the requirements of the circuit.
