by Steven Keeping @ digikey.com
Switching DC-to-DC voltage converters (“regulators”) comprise two elements: A controller and a power stage. The power stage incorporates the switching elements and converts the input voltage to the desired output. The controller supervises the switching operation to regulate the output voltage. The two are linked by a feedback loop that compares the actual output voltage with the desired output to derive the error voltage.
The controller is key to the stability and precision of the power supply, and virtually every design uses a pulse-width modulation (PWM) technique for regulation. There are two main methods of generating the PWM signal: Voltage-mode control and current-mode control. Voltage-mode control came first, but its disadvantages––such as slow response to load variations and loop gain that varied with input voltage––encouraged engineers to develop the alternative current-based method.
Today, engineers can select from a wide range of power modules using either control technique. These products incorporate technology to overcome the major deficiencies of the previous generation.
This article describes voltage- and current-mode control technique for PWM-signal generation in switching-voltage regulators and explains where each application is best suited.
Voltage- and Current-Mode Control for PWM Signal Generation in DC-to-DC Switching Regulators - [Link]
Programme of webinar:
Linear Technology’s family of DC/DC Module products simplifies your analog design. By integrating the DC/DC controller, power switches, magnetic, and a modest amount of capacitance, uModules power products will save precious space on the PCB and reduce the solution weight, development time, BOM qualification and procurement effort.
- Product groups and parameter ranges
- uModule construction
- Reliability data
- Features: ultralow noise, output sharing, synchronizability / multi-phase operation
- Information resources
- Applications examples.
SOS Webinar – Your way to simple and efficient power supply design with Linear Technology - [Link]
IP phones require data and power on the same cable. A high voltage power source of 48V is required, to reduce the voltage drop in the cable. This project has a DC-DC step-up converter that can deliver the required 48V supply at high efficiency. The MAX668 is an excellent choice for the design of this DC-DC step-up converter. The MAX668, a current-mode controller, operates in the PWM mode at medium and heavy loads, providing high-efficiency and low-noise. With power levels greater than 20W, efficiencies of more than 90% are achievable.
MAX668 48V IP Phone Power Supply – [Link]
Adding to their ever growing family of power supply regulators Linear Technology have introduced the LTC3807 step-down switching regulator DC/DC controller driving an all N-channel external synchronous power MOSFET stage. The chip uses a constant frequency current mode architecture allowing a phase-lockable frequency of up to 750 kHz.
The chip draws just 50 μA no-load quiescent current and an OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The LTC3807 features a precision 0.8 V reference and power-good output indicator.
Low-loss Step-down Regulator - [Link]
The LT®8310 is a resonant-reset forward converter controller that drives an external low side N-channel MOSFET from an internally regulated 10V supply. The LT8310 features duty mode control to generate a stable, regulated, isolated output using a single power transformer. With the addition of output voltage feedback, via opto-coupler (isolated) or directly wired (nonisolated), current mode regulation is activated, improving output accuracy and load response. A choice of transformer turns ratio makes high step-down or step-up ratios possible without operating at duty cycle extremes.
100 V Forward Voltage Controller - [Link]
This project has been designed around Texas Instruments LM2623 IC, The LM2623 is a high efficiency, general purpose step-up DC-DC switching regulator for battery powered and low input voltage systems. It accepts an input voltage between 2.4V to 12V volts and coverts it into 5V DC. Efficiencies up to 90% are achievable with the LM2623.
2.4V to 5V Step Up DC-DC Converter - [Link]
A tutorial on feedback resistors in DC-DC converters and how to build a high current adjustable power supply using an LM2678.
Build a 2.5V to 14V 3A adjustable power supply! - [Link]
The TPS65262 is a monolithic triple synchronous step-down (buck) converter with 3-A/1-A/1-A output current. A wide 4.5- to 18-V input supply voltage range encompasses the most intermediate bus voltage operating off 5-, 9-, 12-, or 15-V power bus. The converter, with constant frequency peak current mode, is designed to simplify its application while giving designers options to optimize the system according to targeted applications.
TPS65262 – Triple Synchronous Step-Down Converter with 200mA/100mA Dual LDOs - [Link]
I explain buck converters (a type of switch mode power supply) and how to build a 5V 5A power supply using an LM2678.
How to build a switch mode power supply! DC-DC buck converter tutorial! - [Link]
Switch-mode regulator Traco TSR 0.5 will give you as much as you need. If you have an application, where 0.5A is sufficient, then the new series of DC/DC modules is ideal for you.
Maybe, it´s worth to ask a question, whether it makes sense to use a switch-mode regulator for such a low current? For sure yes, at least because of two reasons. If we need to create 3.3V from for example 12V, then at a current of 0.5A a power loss of 4.35W appears at a classic linear regulator. That´s already a quite considerable power, able to heat up a device – especially at smaller enclosures and a dense population on a PCB.
Another reason is energy saving – especially at battery powered devices. Switch mode power supplies (SMPS) have a “genial” feature, that thanks to their high efficiency we use practically whole power drawn from a source, i.e. if we need say 5V/0.5A from a 15V source – we won´t take from it 0.5A but only approx. 0,17-0,18A.
Novelty of company Traco Electronic – series TSR 0.5 is by its function very similar to well known, proven DC/DC regulators TSR1 or TSRN1. The main difference is in a smaller allowed current and a feelingly lower price . That ´s why this series is very suitable for any application, where a current of 0.5A will be sufficient. A big advantage can be a wide operating temperatures range from -40 to +90°C (power derating 5%/K at temperature above 80°C). Maximum input voltage of 32V enables a usage even at power supplying from various alternative energy sources with a big input voltage fluctuations.
This novelty is so far available in a version with 5V output voltage (TSR 0.5-2450) and soon there will be another.
Why to pay for the current, which you won’ t use? - [Link]