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]
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]
Sam Davis writes:
Individual solar-panel systems produce dc power for remote applications while also storing energy in a rechargeable battery supported by a battery-charger IC.
In non-utility grid applications solar panels produce dc power for emergency roadside telephones, navigation buoys, and other remote loads. Virtually all 12-V-system solar panels comprise a series of photovoltaic cells that have a maximum output power of less than 25 W. In producing this power the solar-panel system uses a battery to provide power when the panel is “dark.” The rechargeable battery can supply power for long periods of time, requiring a charger that can properly operate a solar panel.
Meeting this need is Linear Technology’s LT3652 monolithic buck-charger IC, which operates with a single solar panel. The IC uses average-current-mode control-loop architecture to provide constant current/constant voltage (CC/CV) charge characteristics with a programmable charge current. The charger can be programmed to produce a 14.4-V float voltage. Housed in a 3- × 3-mm DFN-12 package, the IC can charge a variety of battery configurations, including up to three Li-Ion/Polymer cells in series, up to four Lithium Iron Phosphate (LiFePO4) cells in series, and sealed lead-acid batteries up to 14.4 V.
Power-Tracking Battery-Charger IC Supports Solar-Power Systems - [Link]
Giorgos Lazaridis writes:
Some time ago i published a theory page regarding the LED driving and controlling methods. These methods were all linear regulators, very simple to make but very inefficient -in terms of power consumption- for high current applications. The idea was to use this theory page as an entrance level for the SMPS LED drivers.
The first SMPS (Switching Mode Power Supply) LED driver that i made is a Buck-Regulating LED Driver using a chip from Allegro Microsystems, the A6210. I was provided some samples from Farnell for testing and prototyping, along with some other cool staff. Do not forget to pay a visit to Farnell on-line store and Element14 website.
The A6210 can drive up to 3A load with constant current, with switching frequencies up to 2 MHz and supply voltage from 9 to 46 volts. It has additionally an optional PWM input to control the brightness of the LED. The sense voltage is limited to 0.18 volts for higher efficiency, since the power dissipation on this sense resistor is minimal. I will be using a 10-12V 1A 10 Watt LED, powered from 24 VDC supply.
High Efficiency High Current LED Buck Driver using the A6210 - [Link]
Here is an article from Texas Instruments featured on EETimes describing how to design a buck-boost converter. These converters are used when the input voltage can be both above and below the output voltage. One example are 3.3V systems powered by lithium-ion batteries which swing from ~3V to ~4V.
This design is in effect a combination of both buck and boost reference designs. When the right switch is left open and control is applied to the left switch a buck converter is made. Vice-versa, when the left switch is left closed and control is applied to the right switch a boost converter is built.
App note: Buck-boost converter - [Link]
Michael Kleinigger writes:
If you’re like me, the first thing you do when wiring up a new circuit is to connect the power and ground rails (with the power source initially turned off… maybe). And you’ve probably got at least one power supply that’ll do the job. But what if you didn’t have the supply you needed? Perhaps all you’ve got is a 12V battery, and you’re in need of a 3.3V source. Well, if you’ve finished your chores, I hear Tosche Station will sell you some power converters. Failing that, you could always build your own. A simple buck converter will likely do the trick.
The buck converter takes a DC input voltage and reduces it by a controllable amount, much like a resistive voltage divider. But unlike your average voltage divider, the buck converter can efficiently supply a substantial output current. In fact, this circuit’s output current should be greater than its input current (on average). And no, that doesn’t violate any laws of physics; the converter’s output power will still be less than its average input power because its output voltage is lower than the voltage at its input. In mathematical terms, (PIN = VINIIN) > (POUT = VOUTIOUT), where IOUT = ILOAD above. Make sense?
Experimenting with Buck Converters - [Link]
The LM25117 is a synchronous buck controller intended for step-down regulator applications from a high voltage or widely varying input supply. The control method is based upon current mode control utilizing an emulated current ramp. Current mode control provides inherent line feed-forward, cycle-by-cycle current limiting and ease of loop compensation. The use of an emulated control ramp reduces noise sensitivity of the pulse-width modulation circuit, allowing reliable control of very small duty cycles necessary in high input voltage applications.
LM5117 / LM25117 — Powerwise Wide Input Range Synchronous Buck Controller with Analog Current Monitor - [Link]
The TPS84620EVM-692 is a fully assembled and tested circuit for evaluating the TPS84620 4.5-V to 14.5-V Input, 6-A Synchronous Buck, Integrated Power Solution. The TPS84620EVM-692 incorporates a DC/DC converter with output voltage and frequency that are adjustable using jumpers.
- Complete Integrated Power Solution Allows Small Footprint, Low-Profile Design
- Efficiencies Up To 96%
- Wide-Output Voltage Adjust (1.2 V to 5.5 V) with 1% Reference Accuracy
- Optional Split Power Rail allows input voltage down to 1.6 V
- Adjustable Switching Frequency (480 kHz to 780 kHz)
- Synchronizes to an External Clock
- Adjustable Slow-Start
- Output Voltage Sequencing / Tracking
- Power Good Output
Synchronous Buck Integrated Power Solution: TPS84620EVM-692 - [Link]
Adam introduces the LM21212-1 & LM21215 12-15A High Efficiency, Adjustable Current Synchronous Switching Regulator family, which features:
- Greater than 97% peak efficiency
- 2.95 – 5.5V input voltage range
- Resistor-programmable current (LM21215)
- Synchronous or adjustable frequency up to 1.5 MHz (LM21212-1)
- Start up into pre-biased loads
- Sub-7mΩ integrated FETs
- Output voltage tracking capability
LM21212/15 15A Adjustable Current Buck Regulator – [Link]
This ebook has a collection of Switching Regulator Circuits for a variety of input and output voltages. Using this catalog you are able to easily select which type of switching regulator fits better on you needs. There are 12 basic circuit categories: Battery, Boost, Buck, Buck-Boost, Flyback, Forward, High Voltage, Multioutput, Off Line, Preregulator, Switched Capacitor and Telecom.
Switching Regulator Circuit Collection - [Link]