by sajjad Haidar @ edn.com:
Power supplies with adjustable DC output ranging from 0V to 30V or 60V are on the market. Above 60V, there are not many. This Design Idea offers a solution.
There are many fixed voltage switching mode power supplies (SMPS) available, and connecting several in series can give us a higher fixed voltage. To obtain an adjustable output either from a SMPS or conventional transformer based supply, one needs to use a linear regulator or a switched mode buck converter. For a buck converter, a MOSFET or an IGBT can be used as a switching element.
Usually, for a high side switch, an IC with bootsrap operation or a pulse transformer is used. There are few photovoltaic couplers available to drive MOSFETs. As they do not provide much current to charge the gate capacitance quickly, these photovoltaic couplers are mainly used to drive low frequency MOSFET switches, such as solid state relays.
Variable HV power supply employs photovoltaic optocoupler - [Link]
By Steven Keeping @ digikey.com:
Modular DC-DC switching voltage converters (or voltage regulators) are fully integrated devices that take away most of the complexity of power supply design — but not all. One of the key areas that are still left to the design engineer’s discretion is the choice of components for, and layout of, the energy storage and filtering circuits. In principle, these look like simple circuits comprising a few resistors, capacitors, and the energy-storage element, usually an inductor.
Capacitor Selection is Key to Good Voltage Regulator Design - [Link]
An SMPS application using PIC16F785 from Microchip. [via]
In this application note, we will examine a typical buck topology intelligent SMPS design using the PIC16F785.
The design presented here shows an alternative single-chip approach to adding intelligence to SMPS designs. The basic design is really unchanged. There are current and voltage feedback loops, a counter-based PWM is used to generate the reference voltage to the voltage loop, and the microcontroller uses the reference voltage to modify the operation of the system in response to conditions sensed through the ADC.
App note: Switching power supply design with the PIC16F785 - [Link]
This project is a 8-12Vdc to +48Vdc DC-DC converter based on MC34063 switching regulator. It’s a simple project of a DC-DC converter to make a phantom power supply for professional microphones. It can deliver 15-20mA at 48VDC. It ‘s based on MC34063 DC-DC step-up, step-down and boost converter. Input is between 8-12V DC and the output +48VDC/10-20mA.
9V to 48V DC-DC Converter - [Link]
by Charlie Zhao:
The trend in automobiles and industrial systems is to replace mechanical functions with electronics, thus multiplying the number of microcontrollers, signal processors, sensors, and other electronic devices throughout. The issue is that 24V truck electrical systems and industrial equipment use relatively high voltages for motors and solenoids while the microcontrollers and other electronics require much lower voltages. As a result, there is a clear need for compact, high efficiency step-down converters that can produce very low voltages from the high input voltages.
LTC Design Note: 65V 500mA step-down converter - [Link]
by Ken Shirriff:
Disassembling Apple’s diminutive inch-cube iPhone charger reveals a technologically advanced flyback switching power supply that goes beyond the typical charger. It simply takes AC input (anything between 100 and 240 volts) and produce 5 watts of smooth 5 volt power, but the circuit to do this is surprisingly complex and innovative.
Apple iPhone charger teardown - [Link]
If we´re deciding whether to use a classic transformer or better a modern electronic switch-mode power supply (SMPS), it´s good to realize pros and cons of both technologies.
Switch mode power supplies Myrra series 47000 already found their stable place on the market and they gradually replace classic transformers. Why is it so?
Switch-mode power supplies definitely win in a perhaps the most important requirement of these days – in efficiency (in a whole load range) and in a low no-load consumption (Standby). Similarly also many other factors say in favor of switch-mode power supplies, for example power/ weight ratio, size, simple elimination of a high inrush current, silent operation, minimum stray magnetic field, …From these reasons for the majority of applications it´s better and often even cheaper to use an “electronic replacement” of transformer – for example modules series Myrra 47xxx or AC/DC modules Traco Power for higher power ratings.
Maybe it´s worth to question, whether there´s still any reason to use a classic transformer in usual applications with power demands say 1-1000W? Surely yes, for example in application very sensitive to HF radiation (HF receivers, pre-amplifiers,…) but also in applications with a demand for the highest reliability for decades. Transformer is a component which almost doesn´t age and if properly sealed in a resin, then it´s lifetime is extremely long. As a transformer doesn´t contain any semiconductors, capacitors etc, it´s also very resistant to various spikes, overvoltages and noise in a power line…
Power supplies of 47000 series have a very low no-load power consumption – only 200 mW, resp. 300 mW at unregulated types. With the 4000VAC isolation (input/output), they´re ready for a class II – reinforced isolation. With a built-in protection against shortcut and over-temperature, they´re ready for usage in a virtually any device with power demands up to approx. 5-5,4W.
Detailed information will provide you the Myrra 47000 datasheet and the article Save energy and production costs with Myrra 47000 switch-mode power supplies.
Transformer classic or an electronic one? - [Link]
by Rajan Bedi:
Today’s spacecraft subsystems require an increasing number of power rails and supply distributions with loads ranging from milliamps to tens of amps. It is important to choose the appropriate solution to meet the performance and reliability requirements for the target mission.
Switched-mode power supplies (SMPS) use energy storage elements such as inductors, capacitors or transformers to transfer energy from the input to the output at periodic intervals. In a SMPS, transistors are operated in their low-dissipative switching states instead of active mode as used by a linear regulator. When a transistor is on and conducting, the voltage drop across its power path is minimal, and when it is off, there is almost no current through the power path.
Switch-mode regulators for space applications - [Link]
by Kalle Hyvönen:
Here’s a quick project I made in couple days or so. It is a push-pull step-down laser diode driver based on LT1683 SMPS controller chip from Linear Technology. The circuit works with 12-18V input and can put out about 1A to a 2V load. I used a PL140-105L planar ferrite transformer from Coilcraft which is quite overkill for this application (it is rated for 140W).
Switchmode laser diode driver based on LT1683 - [Link]
The LT3690 is an adjustable frequency monolithic buck switching regulator that accepts input voltages up to 36V. A high efficiency 90mΩ switch is included on the device along with the boost diode and the necessary oscillator, control, and logic circuitry. The internal synchronous power switch of 30mΩ increases efficiency and eliminates the need for an external Schottky catch diode. Current mode topology is used for fast transient response and good loop stability. Shutdown reduces input supply current to less than 1μA. The low ripple Burst Mode maintains high efficiency at low output currents while keeping output ripple below 15mV in typical applications.
LT3690 – 36V, 4A, 1.5MHz Synchronous Step-Down Switching Regulator with 70μA Quiescent Current- [Link]