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The LT3651 enables fast charging of Li-Ion/Polymer batteries by delivering up to 4A of continuous charge current with minimal power loss. This is due to its high efficiency switchmode topology, including on-chip synchronous MOSFETs. Its autonomous operation means no microcontroller is necessary and the device integrates an onboard C/10 or timer charge termination. The LT3651’s programmable input current limit with PowerPathTM control regulates charge current to maintain a constant supply current, preventing the input supply from collapsing.

• Wide Input Voltage Range: Up to 32V (40V Absolute Maximum)
• Programmable Charge Current Up to 4A
• Selectable C/10 or Onboard Timer Termination
• Dynamic Charge Rate Programming/Soft-Start
• Programmable Input Current Limit

LT3651 – Monolithic 4A High Voltage 1 Cell Li-Ion Battery Charger - [Link]

Publitek European Editors writes:

Many security and motion detector systems rely on small, semi-autonomous nodes that are easy and simple to install. This implies the use of a battery-based power source and low-power operation in order to minimize the number of battery changes during the lifetime of the product.

Over its lifetime, the output voltage of a battery falls, with the biggest decline when the charge is nearing full depletion. A converter type that can accommodate this change in voltage but can still provide relatively high voltages for sensors and RF transmitters is the buck-boost converter – it operates the buck part of the circuit when the battery is fresh, moving to boost operation when the voltage falls below the threshold of the electronic circuitry it powers. A number of vendors have developed integrated buck-boost converters optimized for battery systems

Buck-Boost Converters Help Extend Battery Life for Motion Detection - [Link]

Jason Frels wrote an excellent article on his experience working with LTC3731 based switchmode power supply. The article is focused on stability testing and performance tweak of the power supply. To test the stability of a control loop we have to measure the frequency where the gain is 0dB and the phase margin on that point. For a stable design the phase margin should be 45° or better. Also the frequency on 0dB point shouldn’t be to low (even with good phase margin) as this drives to slow response of output on load changes. To make such measurements specialized equipment is used. Check the great graphs on the link below.

Stability Testing a Switching Mode Power Supply - [Link]

by Publitek European Editors:

Small, flexible, low-cost but high-performance microcontrollers, and the off-the-shelf boards built around them, are revolutionizing the world of electronics design for small systems. Products such as the Microchip PIC16, the Atmel AVR and Texas Instruments MSP430, and ready-made modules based around these and similar microcontrollers such as the Arduino and Basic Stamp, provide a range of flexible, programmable I/Os that lend themselves to a wide variety of different applications.

Many of these systems are powered by batteries, which have a strongly variable output voltage as they discharge. For example, the voltage output by a rechargeable lithium-ion battery will typically fall as it discharges from 4.2 V to around 3 V, with a wide plateau in the 3.5 V region. This is where most of the stored power will be delivered.

Flexible Power for Versatile Micros - [Link]

The LM22670 switching regulator provides all of the functions necessary to implement an efficient high voltage step-down (buck) regulator using a minimum of external components. This easy to use regulator incorporates a 42V N-channel MOSFET switch capable of providing up to 3A of load current. Excellent line and load regulation along with high efficiency (>90%) are featured.

3A SIMPLE SWITCHER, step-down voltage regulator with synchronization or adjustable switching frequency - [Link]

Min Chen writes:

 The non-synchronous flyback topology is widely used in isolated power supplies ranging from sub watt power levels to tens of watts. With more green-mode standards emerging around the world, improving light load efficiency and reducing no-load input standby current are more demanding than ever. Unfortunately, the traditional isolated power supplies using optocouplers can no longer achieve the performance requested.

The new LT®8300 builds a 5V/300mA low IQ isolated power supply from a 36V to 72V input with only five external components (input capacitor, output capacitor, transformer, feedback resistor and output diode). Without skimping any performance, the simple LT8300 solution achieves 85% peak efficiency, less than 250µA no-load input standby current, ±1% output load and line regulation, less than 50mV peak-to-peak output voltage ripple and well-behaved transient and startup performance.

Simple and Efficient Sub-2W Isolated Power Supply - [Link]

Maxim describes various SMPS regulator topologies for battery powered systems. Isolated and non-isolated topologies are covered:

This tutorial presents an overview of regulator topologies for battery-powered equipment. The discussion covers linear regulators, charge pumps, buck and boost regulators, inverters, and flyback designs. The importance of peak current is explained, and schematics of each topology are shown.

Switch mode regulators for battery powered systems - [Link]

The TPS53014 is a single, adaptive on-time D-CAP2 mode synchronous buck controller. The TPS53014 enables system designers to complete the suite of various end equipment’s power bus regulators with cost effective low external component count and low standby current solution. [...]

The device provides convenient and efficient operation with input voltages from 4.5 V to 28 V and output voltage from 0.77 V to 7.0 V.

TPS53014 – Single Synchronous Step-Down Controller for Low Voltage Power Rails - [Link]

If we compare a power consumption of classic adapters to switch-mode ones in a no load condition (standby), we will come to surprising values. The difference can be up to tens of kWh per year.

If we take as an example a relatively common 12W 12V/1A adapter, we can suppose about 2W power consumption in a standby mode. Modern switch-mode adapters have this power consumption only 0.5W (often even below 0.3W). It is 1.5W, in other words over 13 kWh a year. If we compared an overall efficiency at a real load, we would very probably count even bigger difference, because the efficiency of a switch-mode adapter is mostly 70-90%, while the efficiency of a classic circuit (transformer + a linear stabilizer) is often below 50%.

From this point of view, switch-mode adapters Minwa , clearly win over classic adapters. They are available directly from our stock, providing all benefits of switch-mode power supplies and they are a suitable substitution for classic adapters. In the MW3 series can be found types with an adjustable output voltage in a range of 3-12V and with exchangeable output DC connectors. In the Nx series, types with a fixed output voltage can be found and with a fixed 5.2/2.1 mm output DC connector. New adapters are resistant to shortcut and overload and they meet the most recent requirements about energy efficiency (EuP/ErP 2). A relatively stable – regulated output voltage enables to directly power many devices, without any additional (LDO) stabilizers – linear regulators, what further simplifies a target device design. Thanks to small dimensions, low weight and last but not least – also thanks to a very competitive price, they represent a suitable solution of a power supply for various devices.

Don’t throw away 13 kWh per year! Switch-mode adapters Minwa will help you with it - [Link]

A Switch Mode Power Supply circuit collection from Linear Technology. It covers 12 basic SMPS circuit categories: Battery, Boost, Buck, Buck-Boost, Flyback, Forward, High Voltage, Multioutput, Off Line, Preregulator, Switched Capacitor and Telecom. [via]

Switching regulator circuit collection - [Link]