Choosing the best operating frequency for your power supply is a complex trade-off involving size, efficiency, and cost. Generally speaking, low-frequency designs tend to be the most efficient, but they are also the largest and most expensive. While increasing the frequency can reduce size and cost, it increases circuit losses. Next, we use a simple buck power supply to illustrate these trade-offs.
Let's start with the filter components. These components take up a large portion of the power supply volume, and the size of the filter is inversely proportional to the operating frequency. On the other hand, every switching transition is accompanied by energy loss; the higher the operating frequency, the higher the switching losses and the lower the efficiency. Secondly, higher frequency operation usually means that smaller component values can be used. Therefore, higher frequency operation can bring great cost savings.
Figure 1.1 shows the relationship between frequency and size for a step-down power supply. At 100kHz, the inductor occupies the majority of the power supply volume (dark blue area). If we assume that the volume of the inductor is related to its energy, then its volume will decrease in direct proportion to the frequency. This assumption is not optimistic in this case because the core losses of the inductor will increase significantly at a certain frequency and limit further size reduction. If ceramic capacitors are used in this design, the output capacitor volume (brown area) will decrease with frequency, that is, the required capacitance will decrease. On the other hand, the input capacitor is usually selected because of its ripple current rating. This rating does not change significantly with frequency, so its volume (yellow area) can often remain constant. In addition, the semiconductor part of the power supply does not change with frequency. Thus, due to low-frequency switching, the passive components occupy a large proportion of the power supply volume. As we move to high operating frequencies, the semiconductors (i.e. semiconductor volume, light blue area) begin to occupy a larger proportion of the space.
Figure 1.1 The volume of power supply components is mainly occupied by semiconductors
This graph shows that semiconductor volume does not essentially scale with frequency, which is probably an oversimplification. There are two main types of losses associated with semiconductors: conduction losses and switching losses. Conduction losses in a synchronous buck converter are inversely proportional to the die area of the MOSFET. The larger the MOSFET area, the lower its resistance and conduction losses.
Switching losses are related to how fast the MOSFET switches and how much input and output capacitance the MOSFET has. These are all related to the size of the device. Larger devices have slower switching speeds and more capacitance. Figure 1.2 shows the relationship between two different operating frequencies (F). Conduction losses (Pcon) are independent of the operating frequency, while switching losses (PswF1 and PswF2) are directly proportional to the operating frequency. Therefore, a higher operating frequency (PswF2) will produce higher switching losses. When the switching losses and conduction losses are equal, the total losses for each operating frequency are the lowest. In addition, as the operating frequency increases, the total losses will be higher.
Figure 1.2 Increasing the operating frequency results in higher overall losses
However, at higher operating frequencies, the optimal die area is smaller, resulting in cost savings. In fact, at low frequencies, minimizing losses by adjusting the die area results in a very expensive design. However, moving to higher operating frequencies allows us to optimize the die area to reduce losses, thereby shrinking the semiconductor size of the power supply. The downside of this is that if we do not improve semiconductor technology, the power supply efficiency will decrease.
As mentioned earlier, higher operating frequencies reduce the size of the inductor; fewer inner cores are needed. Higher frequencies also reduce the output capacitor requirements. With ceramic capacitors, we can use lower capacitance values or fewer capacitors. This helps reduce the semiconductor die area, which in turn reduces cost.
Previous article:The secret that cannot be underestimated: seeing the power supply clearly from the three series capacitors
Next article:One technique and three precautions to solve the problem of power supply matching for integrated graphics card or independent graphics card
- Popular Resources
- Popular amplifiers
- New Technologies and Equipment for Communication Power Supply Series High Frequency Switching Power Supply for Communication
- First Time, Every Time – Practical Tips for Phase- Locked Loop Design
- A 25mA 0.13μm CMOS LDO Regulator with Power- Supply Rejection Better...
- Switching Power Supply Design & Optimization
- MathWorks and NXP Collaborate to Launch Model-Based Design Toolbox for Battery Management Systems
- STMicroelectronics' advanced galvanically isolated gate driver STGAP3S provides flexible protection for IGBTs and SiC MOSFETs
- New diaphragm-free solid-state lithium battery technology is launched: the distance between the positive and negative electrodes is less than 0.000001 meters
- [“Source” Observe the Autumn Series] Application and testing of the next generation of semiconductor gallium oxide device photodetectors
- 采用自主设计封装,绝缘电阻显著提高!ROHM开发出更高电压xEV系统的SiC肖特基势垒二极管
- Will GaN replace SiC? PI's disruptive 1700V InnoMux2 is here to demonstrate
- From Isolation to the Third and a Half Generation: Understanding Naxinwei's Gate Driver IC in One Article
- The appeal of 48 V technology: importance, benefits and key factors in system-level applications
- Important breakthrough in recycling of used lithium-ion batteries
- Innolux's intelligent steer-by-wire solution makes cars smarter and safer
- 8051 MCU - Parity Check
- How to efficiently balance the sensitivity of tactile sensing interfaces
- What should I do if the servo motor shakes? What causes the servo motor to shake quickly?
- 【Brushless Motor】Analysis of three-phase BLDC motor and sharing of two popular development boards
- Midea Industrial Technology's subsidiaries Clou Electronics and Hekang New Energy jointly appeared at the Munich Battery Energy Storage Exhibition and Solar Energy Exhibition
- Guoxin Sichen | Application of ferroelectric memory PB85RS2MC in power battery management, with a capacity of 2M
- Analysis of common faults of frequency converter
- In a head-on competition with Qualcomm, what kind of cockpit products has Intel come up with?
- Dalian Rongke's all-vanadium liquid flow battery energy storage equipment industrialization project has entered the sprint stage before production
- Allegro MicroSystems Introduces Advanced Magnetic and Inductive Position Sensing Solutions at Electronica 2024
- Car key in the left hand, liveness detection radar in the right hand, UWB is imperative for cars!
- After a decade of rapid development, domestic CIS has entered the market
- Aegis Dagger Battery + Thor EM-i Super Hybrid, Geely New Energy has thrown out two "king bombs"
- A brief discussion on functional safety - fault, error, and failure
- In the smart car 2.0 cycle, these core industry chains are facing major opportunities!
- The United States and Japan are developing new batteries. CATL faces challenges? How should China's new energy battery industry respond?
- Murata launches high-precision 6-axis inertial sensor for automobiles
- Ford patents pre-charge alarm to help save costs and respond to emergencies
- New real-time microcontroller system from Texas Instruments enables smarter processing in automotive and industrial applications
- LED PWM Dimming C Program
- Keil.STM32H7xx_DFP.2.2.0 installation package problem
- Drawing
- EEWORLD University Hall - Open Source Power Linux Kernel Source Code Study and Practical Exercises
- Let me show you how to calculate a current transformer!
- Theory and Implementation of Narrow-Band IF Sampling Based on DSP_C54X
- [RT-Thread reading notes] (1) Thread initialization and linked list
- Share the correct use and maintenance guide of NiMH batteries
- EEWORLD University Hall----Live Replay: The Latest Isolation Devices Compliant with USB 2.0 Standards
- EEWORLD University - Understanding PID Control (English subtitles)