Power module: Comparative analysis and application of LDO and DC-DC

2024-01-17 15:39:25 35

Power modules are used in many scenarios in life, such as communications, industrial automation, power control, railways, mining, military industry and other fields. DC power conversion modules are divided into two types: low voltage dropout linear power supply (LDO) and switching power supply (DC-DC).

1.LDO


Traditional linear voltage regulators, such as the 78xx series of chips, require the input voltage to be more than 2V~3V higher than the output voltage, otherwise they will not work properly. But in some cases, such conditions are obviously too harsh. For example, when converting 5V to 3.3V, the voltage difference between the input and output is only 1.7v, which obviously does not meet the conditions. In response to this situation, LDO power conversion chips are available.

Linear power supplies mainly use LDO (low dropout regulator), which is a low-voltage linear DC regulated power supply module.

LDO maintains a stable output voltage by adjusting the impedance change of the circuit tube. When the output voltage increases from the input voltage or the load current decreases, and there is a tendency for the output voltage to deviate from the set value and increase, the impedance of the adjustment tube is adjusted through negative feedback. Increase, reduce the output voltage to restore the set value and maintain stability. When the input voltage decreases or the load current increases, and the output voltage tends to deviate from the set value and decrease, the impedance of the adjustment tube is reduced through negative feedback, and the output voltage is increased to restore the set value and remain stable.

Today's LDOs are highly integrated and generally only require 2 capacitors (usually 2 1uF) and an LDO chip. The circuit is simple, as shown below:

2. DC-DC


The switching power supply DC-DC (Directcurrent-Directcurrent) converter is composed of a regulating chip, a pole electromagnetic coil, a diode, a transistor and a capacitor. The switching power supply DC-DC is a voltage that can effectively output a stable working voltage after being converted into an input working voltage. converter. A switching regulated power supply (DC-DC) is a pulse generator that uses a switching power supply circuit to output an adjustable duty cycle or operating frequency. It uses high-frequency voltage regulator tubes, inductors, and capacitors to form a DC output voltage. By changing the duty cycle or The output voltage is adjusted according to the operating frequency.

Switching power supply DC-DC includes three types: BUCK (step-down), BOOST (step-up), and BUCK/BOOST (step-up and step-down). Three types of adjustment can be selected according to market demand. The PWM adjustment type has high working efficiency and good output voltage ripple and noise. The PFM adjustment type has the characteristics of low power consumption even when used for a long time, especially at small loads. PWM/PFM conversion implements PFM regulation when the load is small, and the system automatically switches to PWM regulation when the load is heavy.

A typical DC-DC BUCK circuit includes input and output capacitors, FREQ frequency setting, EN enable pin, FB feedback resistor, freewheeling diode and inductor on SW, BST capacitor, COMP frequency compensation, etc., as shown in the figure below:

3. Selection criteria


The main difference in performance indicators between LDO and DC-DC is that the output voltage ripple of a linear regulated power supply (LDO) is small. However, when the input operating voltage and output voltage are relatively large, the conversion efficiency is low, and only the voltage reduction is insufficient. Can boost. The ripple of the switching regulated power supply (DC-DC) is large. However, when the distance between the input operating voltage and the output voltage is relatively large, the conversion efficiency is higher and the voltage can be increased or decreased. The specific details of the difference are as follows:

LDO has few peripheral components, simple circuit, and low cost; DC-DC has many peripheral components, complex circuit, and high cost;
LDO load response is fast and the output ripple is small; DC-DC load response is slower than LDO and the output ripple is large;
LDO efficiency is low, and the input-output voltage difference cannot be too large; DC-DC efficiency is high, and the input voltage range is wide;
LDO can only step down; DC-DC supports step-down and step-up;
The quiescent current of LDO and DC-DC is both small, depending on the specific chip;
LDO output current is limited, the highest may be a few A, and reaching the highest output is related to the input and output voltage; DC-DC output current is high and the power is high;
LDO has small noise; DC-DC switching noise is large. In order to improve the accuracy of switching DC-DC, many applications will connect LDO at the back end of DC-DC;
LDO is divided into adjustable and fixed types; DC-DC is generally adjustable and adjusted through FB feedback resistor.
For boosting, you must choose DC-DC. For bucking, whether to choose DC-DC or LDO must be compared in terms of cost, efficiency, noise and performance.

Tags:#Power module

Tags

STMicroelectronics (ST)sensordiodecapacitormemoryVariable Inductormagnetic beadsPower moduleEmbedded product developmentEmbedded hardware development processTL064CDTMCUSTM32F070CBT6Power management (PMIC)ThyristorMOS tubeHardware designElectric heaterEmbedded systemresistorOperational amplifierDigital power supplyPCBThin film capacitanceElectrolytic capacitancecircuitLithium batteryLithium-ion batteryICPower sourceHisilicon chipKirin chipPower chipPower amplifierNTC thermistorPower capacitorPassive filterExcitation transformerApple M series chipsBuck circuitAC/DC converterIGBTAluminum electrolytic capacitorTantalum capacitorAluminium polymer capacitorsupercapacitorDouble electric layer capacitorCeramic capacitorFilm capacitorSurge suppression icElectrostatic Discharge (ESD)PTC resets the fuseEMIBuck circuit optimizationEMCSwitching Mode Power Supply (SMPS)inductorPhotoetching machineCircuit protectionLightning arresterGas discharge tubeInrush current limiter (ICL)Circuit breakerSwitching power supplyGFCIFuse wireThermal fuseChip resistance/patch resistanceCircuit designcouplerCircular connectorCasing connectorESDTerminal connectorModular connectorCoaxial connectorRS-485AvagoRenesasPCB LayoutCreepage distanceElectrical clearanceSamsung ElectronicsRegulated power supplyDC-DC converterCharging circuitComplete circuit diagramMemory connectorLaminated inductorsMagnetic beadChip manufacturing processTVS diodeLot NumberPassive elementCircuit analysis methodSwitching power supplyHeavy-duty connectorTerminal blockElectrical connectionRENESASAltiumpurchaseSignal isolatorSafety fencedistinctioninfineonQ3 Financial revenueD-sub connectorType D connectorBackplane connectorAC power connectorBlade power connectorOptical fiber connectorRussiaSemiconductor silicon wafersAdvanced Micro-Fabrication Equipment Inc.ChinaElectronic components industry trendsPassive electronic componentsTIBasic electronic componentWelded electronicsElectronic componentprincipleHow electronic components workCircuit Board (PCB)Test elementLight-emitting diodePerformance parameterWhat electronic components were used in the first generation of computersFirst-generation computerRectangular connectorElectronic component distributorElectronic components online mallVCOVoltage-controlled oscillatorVoltage-controlled oscillatorencoderCommon encoder typesEncoder applicationElectronic component procurementoscillatorProgrammable oscillatorresonatorHow the resonator worksThe role of the resonatorCrystal oscillatorCrystal vibration basic knowledge introductionCrystal vibration selection guideProximity sensorsensorSensor installation and maintenanceUltrasonic sensorThe use of ultrasonic sensorsColor sensorSelection guideMotion sensorHow motion sensors workThe role of motion sensorsType of motion sensorPressure sensorHow to choose a pressure sensorPressure sensor maintenance skillsMethod of turning off proximity sensorCurrent sensorCPUThe CPU approaches the average temperature of the sensorInductive proximity sensorFiber optic current sensoradvantagepeculiarityHow to choose the right sensorTouch sensorPrinciple of touch sensorTouch sensor BenefitsExample programming interface for touch sensorTroubleshooting method of touch sensorThe purchase guide for touch sensorsWhat are the brand suppliers of touch sensorsTouch sensor switchCapacitive touch sensorPosition sensorCommon types of position sensorsHow the position sensor worksInstallation of position sensorsHUAWEIThrottle position sensorHow do I install a humidity sensorDaily maintenance of humidity sensorCalibration of humidity sensorsHumidity sensorType of the humidity sensorHumidity sensor selectionWorking principle of the humidity sensorAdvantages and disadvantages of humidity sensorsThe humidity sensor is faulty. ProcedureCleaning and maintenance of humidity sensorMethod of measuring humidityWet and dry bulb thermometer methodDew point meter methodLithium chloride hygrometer methodCrankshaft position sensorThe crankshaft position sensor is faultyCrankshaft position sensor detectionWhat is a Wago connectorWago connector and sleeve comparisonWhat is a wire connector sleeveCommon types of wire connector sleeves

Hot Sale Parts