Steven Keeping writes:
Switching DC/DC converters (“regulators”) have become popular because they are highly efficient and able to step-up (boost), step-down (buck), and invert voltages with ease. However, voltage and current ripples generated by high frequency operation can cause operational problems with sensitive chips and electromagnetic interference (EMI) hassles.
One answer is to spend a lot of time and resources ‘tuning’ the PCB design to minimize parasitic inductances and capacitances, and design time consuming filter circuits to minimize voltage and current ripples. Another is to enlist the venerable linear regulator to work in tandem with the switching converter to smooth the output of the latter and provide a stable, reliable voltage output.
This latter technique requires careful design and considered component selection to get the two regulators working in harmony and eliminate those post-regulation filters. This article describes the benefits of a “hybrid” voltage regulator approach, recommends component selection criteria, and describes a low-noise analog power supply example from Texas Instruments.
Hybrid Power Supplies Deliver Noise-Free Voltages for Sensitive Circuitry - [Link]
The TPS65135 is a high-efficient, single-inductor, dual-output converter. Due to its single-inductor multiple-output (SIMO) technology, the converter uses a minimum of external components. The device operates with a buck-boost topology and generates a positive and a negative output voltage above or below the input voltage rail. The SIMO technology enables excellent line and load regulation required to avoid disturbance of a mobile phone display as a result of input voltage variations that occur during transmit periods. The device can also be used as a standard ±supply as long as the output current mismatch between the rails is smaller than 50 percent.
TPS65135 – Single-Inductor, Multiple-Output (SIMO) Regulator - [Link]
PowerXR Programmable Power Solutions
A range of serial (I2C) programmable step-down regulators for complex systems with multiple supply voltages.
- 3 or 4 completely independent PWM channels.
- One 3.3/5 V selectable linear LDO regulator.
- Programmable output voltage from 0.9 to 5.1 V.
- Programmable switch frequencies from 0.3 to 1.5 MHz.
- Up to 6 configurable GPIO pins.
- PowerArchitect™ » Free development software.
PowerXR – Programmable switching regulator - [Link]
Linear Technology Corporation introduces the latest device in its family of DC/DC uModule™ regulator systems that can regulate an output voltage from a variable input voltage greater than, less than or equal to the output voltage.
The LTM4607 is designed for higher voltage systems and operates from 4.5VIN to 36VIN, regulates an output voltage from 0.8V to 24V, and delivers output power up to 190W. The LTM4607 integrates a synchronous buck-boost DC/DC controller, four N-channel MOSFETs, input and output bypass capacitors and all compensation circuitry in a 15mm x 15mm x 2.8mm land grid array (LGA) plastic molded package. Only an inductor, feedback and sense resistors, and bulk capacitors are required to implement a very low profile, compact and high efficiency design. The LTM4607 provides a compact regulator solution for applications such as networking, industrial, automotive systems and high power battery-operated devices.
The LTM4607 is offered for operation from -40°C to 85°C temperature range.
97% Efficient, Buck-Boost DC/DC uModule Regulator - [Link]
The TL431 is a three-terminal adjustable shunt regulators, with specified thermal stability over applicable automotive, commercial, and military temperature ranges. The output voltage can be set to any value between Vref (approximately 2.5 V) and 36 V, with two external resistors.
- Operation from -40°C to 125°C
- Reference voltage tolerance at 25°C
- 1%: A grade
- 2%: standard grade
- Low output noise
- 0.2-Ω typical output impedance
- Sink-current capability: 1 mA to 100 mA
- Adjustable output voltage: Vref to 36 V
TL431: Cost-effective shunt regulator solution - [Link]
System-level hardware designers pay careful attention to selecting the right analog signal path ICs for their specific applications. Each IC needs “clean” power but often, power management is the last part of a system design. As many designers know, power supply design affects the analog signal integrity which, ultimately, impacts overall system performance.
National Semiconductor’s broad portfolio of low-noise, low dropout (LDO) regulators preserve signal fidelity in the analog signal path over a wide range of input voltages and output currents. National’s portfolio of low-noise LDOs provide maximum Power Supply Rejection Ratio (PSRR) and low output voltage noise for low-power, space-constrained applications. In contrast to switching regulators which induce a voltage ripple and other high frequency voltage spikes in their output, an LDO’s PSRR filters out unwanted noise.
Low Dropout Regulators Deliver Quiet Power for Noise-Sensitive Circuits - [Link]
An unconventional, scalable high efficiency 12V solar power system, a battery charge controller with low voltage cutout to protect the battery. www.opend.co.za writes:
Low idling current
This circuit was designed for small to medium lead acid systems and feature a lowish idle current ( 5mA ) which increases battery life on small capacity systems.
Easily obtainable parts
All the parts in this design are through hole parts and can be found from a number of sources. None of the parts need programing and only a voltmeter and an adjustable supply is needed to calibrate the board. This makes it easy and cheap to build and maintain.
This is the 3rd iteration of the design, with improvements and bug fixes at every step.
A Novel high efficiency scalable solar regulator - [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]
This device, remember, takes 80-265Vrms wall power and puts out a (relatively) clean 5V DC. According to the datasheet, the way this thing works is by monitoring the voltage of the AC waveform and charging a big electrolytic capacitor during the low voltage segments on the leading and trailing edge of the (half-rectified) wave. The controller then discharges the capacitor to sustain the 5V DC. It claims it can handle a maximum load of 35mA
Be careful working with unisolated AC voltage, that stuff will kill you in an instant. We don’t do it.
FSAR001 AC to 5volt DC regulator – [Link]
Pin-compatible regulator with high efficiency for fixed voltage [via]
For decades, the linear voltage regulator of the 78 series and its variants have been extremely popular, because these three-legged ICs allow stable supply voltages in the low voltage range to be created in a cost effective way. However if the difference between input and output voltage is considerable, efficiency decreases and the wasted heat must be dissipated which is not only costly and space consuming, but also a source of problems with thermal drift in sensitive and precision electronics. The use of switching regulators on the other hand generally requires more external parts and greater board surface. A modern replacement for the popular 3-pin voltage regulator would therefore make life easier for many electronic designers and engineers.
K78XX = switch-mode LM78XX – [Link]