• 中文 | ENGLISH
Welcome to Shenzhen Jasencan Electronics Co., Ltd.
Digi-Key Electronics - Electronic Components Distributor
  • Product
    Back
    • Recommended
    • Passive device
      Back
      • Capacitor
      • Resistor
      • microphone
      • Inductor
      • Air flow sensor
      • Field effect transistor
      • Two transistor
      • Rectifier Bridge Stack
      • Crystal oscillator
      • filter
    • Active device
      Back
      • integrated circuit
    • Module solution
      Back
      • Module solution
  • About
    Back
    • Company Profile
    • Company Culture
    • Company History
  • News
    Back
    • Company News
    • Industry News
    • Product Knowledge
  • Customer Info
  • Contact
  • Join us
RMB | USD
您的项目
查看购物车
登录 注册 退出
News > DC/DC Converters Research Guide - Serial 4

DC/DC Converters Research Guide - Serial 4

By:JASENCAN

Time:2023.03.23

View:

7. Coil selection
 
The optimum L value varies for different switching frequencies because the coil current is proportional to the ON time of the FET and inversely proportional to the L value. The loss caused by the coil is the sum of the coil winding resistance RDC and the loss caused by the ferrite core. However, for a switching frequency of about 2MHz, it can be assumed that most of the losses of the coil are caused by the RDC, and the coil with small RDC should be selected first. However, if a coil with a small L value is selected to reduce the RDC, the current value is too large during the time when the FET is ON, and the heat loss generated by the FET, SBD, and coil becomes large, and the efficiency decreases. Moreover, the ripple increases due to the increase of current.
 
On the contrary, if the L value is too large, the RDC becomes large, not only the efficiency at heavy load becomes poor, but also the ferrite core becomes magnetically saturated, and the L value decreases rapidly, so that the performance of the coil cannot be realized, and it falls into the dangerous state of overheating caused by excessive current. Therefore, in order to flow large currents in coils with large L-values, the shape must be of a certain size to avoid magnetic saturation.
 
In summary, the appropriate L-value has been limited in terms of both form factor and efficiency relative to the switching frequency. Table 5 shows the standard L-values for each switching frequency value.
 
Translated with www.DeepL.com/Translator (free version)



Figure 12 and Figure 13 show examples of how the efficiency and ripple of the XC9104D093 (boost) circuit shown in Figure 14 change only the L value.
 
Similarly, Figures 15 and 16 show examples of the efficiency and ripple of the XC9220A093 (buck) circuit shown in Figure 17.
 
In both examples, the maximum output current value decreases by increasing the L value, and the efficiency increases and ripple decreases at light loads when the coil structure is the same. This shows that it is important to choose the L value that is appropriate for the output current.
 
Translated with www.DeepL.com/Translator (free version)







8. Selection of SBD
The SBD loss is the sum of the forward heat loss VF×IF and the heat loss caused by the reverse leakage current IR for the same reason as the FET. Therefore, it is ideal to choose a product with small VF and IR. However, VF is inversely proportional to IR, and generally depends on the load current, VF is large at heavy loads, and considering that IR is independent of the load for a certain value, it is better to choose products with small IR at light loads to improve efficiency, and to choose products with small VF at heavy loads. The above contents are summarized in Table 6 below.


Figure 18 shows the efficiency change in the XC9220A093 circuit shown in Figure 19 with only the SBD change shown in Table 7. It can be seen that compared to XBS203V17, XBS204S17 has good efficiency at light load and poor efficiency at heavy load due to large VF and small IR.



The above content is from Tris Semiconductor Co., LTD. In the series...

New Sort

Company News Industry News Product Knowledge

Products Recommended
Hot News
• MOS Huashuo brand selection recomm…
• Comprehensive interpretation of co…
• Multimeter measuring capacitance m…
• Knowledge of electronic components…
• Knowledge of safety capacitors
keep in touch!

Thanks!

Stay tuned to the news and updates of Jiushengchang in your inbox!

Please input your email

Shenzhen Jasencan Electronics Limited
Contact: Manager Hu
Phone: 86-18778283739
Tel: 86-755-8328-5269
Fax: 86-755-8328-6455
QQ:2881718760
Email: sales@jasencan.com
Url:  www.jasencan.com
Add:1307, Building A, Chuangzhiyun Center, No. 1, Guangxia Road, Meiting Community, Meilin Street, Futian District, Shenzhen, Guangdong Province
,518046


Follow us
0755-83285269