A DCDC converter is an electronic circuit or module that converts input DC voltage into DC outputs of different voltage levels. It is widely used in electronic devices, new energy systems, and industrial control to achieve efficient power management. Its core function is to regulate voltage to meet load requirements through the collaborative work of switching devices (such as MOSFETs) and energy storage components (inductors, capacitors). The following is a detailed analysis of its working principle, classification, and typical applications:
1、 The core principle of DCDC converter
Working principle of switch mode
Switching cycle: The input DC power is chopped into pulse signals through high-frequency switches (such as PWM control).
Energy storage and filtering: Utilizing inductive energy storage/discharge and capacitive filtering to smooth the pulse signal into a stable DC output.
Feedback control: Sample the output voltage and adjust the duty cycle to achieve voltage stabilization (such as PID control algorithm).
Key formulas
Buck: \ (V_ {out}=D \ times V_ {in} \)
Boost: \ (V_ {out}=\ frac {V_ {in}} {1 D} \)
Efficiency: \ (\ eta=\ frac {P_ {out} {P_ {in}} \ times 100 \% \), typical values range from 85% to 98%.
2、 Classification and characteristics of DCDC converters
|Type | Topology | Input/Output Relationship | Typical Application Scenarios|
|Buck | Input voltage>Output voltage | \ (V_ {out}<V_ {in} \) | Mobile phone/computer motherboard power supply, LED driver|
|Boost | Input voltage<output voltage | \ (V_{out}>V_{in} \) | Lithium battery boosts to 5V/12V, solar MPPT|
|BuckBoost | Input can be high/low output | \ (V_ {out} \) adjustable polarity | Battery powered devices (such as 3.7V lithium batteries that can be boosted to 5V or 3.3V)|
|Flyback | Isolation topology | Supports multiple isolated outputs | Adapter, offline switching power supply|
|Cuk/SEPIC | Non isolated, low-noise | Variable output polarity (Cuk) | Power supply for automotive electronics and industrial sensors|
3、 Core advantages and challenges
Advantages
Efficient and energy-saving: The efficiency of switch mode is significantly higher than that of linear regulators (such as LDO).
Wide voltage range: supports boost, buck, and negative voltage output, suitable for complex power supply requirements.
Miniaturization: High frequency switches (MHz level) allow the use of small inductors and capacitors.
Challenge
Electromagnetic interference (EMI): Switching noise needs to be suppressed through filtering and PCB layout optimization.
Design complexity: It is necessary to balance loop stability, efficiency, and cost (such as synchronous rectification vs. asynchronous rectification).
4、 Typical application scenarios
Consumer Electronics
Mobile phone/tablet: The lithium battery (3.7V) is reduced to 1.8V (CPU core voltage).
Fast charging technology: BuckBoost achieves PD protocol multi voltage output (5V/9V/12V).
New energy and automobiles
Electric vehicles: The high-voltage battery pack (400V) is stepped down to provide power to the 12V low-voltage system.
Photovoltaic system: The MPPT algorithm maximizes the output power of the solar panel through a Boost converter.
Industrial control
PLC module: The 24V industrial power supply is reduced to 5V/3.3V to supply MCU and sensors.
Motor drive: DCDC provides isolated power supply for the drive chip (such as IGBT gate drive).
Medical equipment
Portable device: The buck boost converter supports stable power supply from lithium batteries throughout the entire charging and discharging process.
Isolation power supply: flyback DCDC ensures safe isolation of patient contact parts.
5、 Key points of design selection
Key parameter selection
Input/output voltage range: Ensure that the converter covers the system requirements (e.g. Vin=5V24V, Vout=3.3V).
Output current capability: Select based on the peak load current (e.g. 3A continuous/5A peak).
Switching frequency: High frequency (2MHz+) reduces component size but increases switching losses.
Topology selection
Non isolated scenarios: Prioritize Buck/Boost (low-cost, high-efficiency).
Isolation requirements: Choose flyback or LLC resonant topology (such as medical devices, industrial communications).
Control mode
Voltage Mode: Simple and easy to use, suitable for ordinary scenarios.
Current Mode: Fast dynamic response, suitable for systems with drastic load changes.
Component selection
Inductance: low DCR, high saturation current (such as iron silicon aluminum core).
Capacitors: Low ESR ceramic capacitors (high-frequency decoupling) and electrolytic capacitors (energy storage).
Switching transistor: MOSFET with low Rds (on) (such as GaN devices to improve high-frequency efficiency).
6、 Representative chips and solutions
TI TPS5430（Buck）
Input 4.5V~28V, output 0.9V~25V/3A, efficiency 95%, suitable for industrial power supply.
ADI LT8610 (Synchronous Buck)
Input 3V~42V, output 0.8V~VIN, 5A output, 2MHz switching frequency, automotive grade certification.
ST L6983（Boost）
Input 2V~38V, output up to 60V, 2A output, supports solar MPPT applications.
Infineon IRS2980 (LLC Resonant Controller)
Isolated DCDC, suitable for server power supply and electric vehicle charging modules.
7、 Common Problems and Solutions
Output voltage oscillation
Solution: Optimize the compensation network (adjust feedback resistance/capacitance) and increase the output capacitance ESR.
Overheating protection triggered
Solution: Check the heat dissipation design (such as increasing the copper foil area), or reduce the switching frequency to reduce losses.
EMI exceeds the standard
Solution: Add a π - type filter, use shielded inductors, and optimize the ground plane layout.
DCDC converters are the "power regulators" of modern electronic systems, supporting a wide range of demands from micro watt level IoT devices to megawatt level new energy systems through efficient and flexible voltage conversion. When selecting, it is necessary to comprehensively evaluate efficiency, cost, size, and environmental adaptability, and combine advanced topology and control technologies (such as digital power supplies and GaN/SiC devices) to address the challenges of high-density and high reliability power supply design.