by Zhongming Ye:
Flyback converters are widely used in isolated DC/DC applications because of their relative simplicity and low cost compared to alternative isolated topologies. Even so, designing a traditional flyback is not easy—the transformer requires careful design, and loop compensation is complicated by the well known right-half plane (RHP) zero and the propagation delay of the opto-coupler.
Linear Technology’s no-opto flyback converters, such as the LT3573, LT3574, LT3575, LT3511, and LT3512, simplify the design of flyback converters by incorporating a primary-side sensing scheme and running the converter in boundary mode.
Micropower Isolated Flyback Converter with Input Voltage Range from 6V to 100V – [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]
Series 47000, designed as a direct replacement of classic transformers brings more than you might expect.
Myrra 47xxx SMPS overcome supersedes classic transformers by an overall efficiency, power as well as by a standby power consumption. With the same pinout as 1W EI30 transformers, it provides a 5W power, or up to 5,4W at some models. All this for the price comparable with a classic solution, but with smaller dimensions, without any additional components and without problems with cooling. Next to basic features represented to you in a separate article we bring you a more detailed description of particular versions.
47000 series power supplies feature a very low standby power consumption –only 200 mW or 300 mW respectively – at regulated types. With the 4000VAC isolation (input/output), they´re ready for a classs II – reinforced isolation . Operating ambient temperature is from -25°C to Ta, which can be found in a table at each type. To a simple usage also contributes a shortcut protection and a thermal shutdown with automatic recovery. More information will provide you the following tables and the Myrra 47000 datasheet.
Save energy and production costs with Myrra 47000 switch-mode power supplies – [Link]
- Complete Step-Down Switch Mode Power Supply
- Constant-Voltage Constant-Current Operation
- Selectable Output Current Up to 5A
- Parallelable for Increased Output Current, Even from Different Voltage Sources
- Wide Input Voltage Range: 6V to 36V
- 1.2V to 24V Output Voltage
- Selectable Switching Frequency: 100kHz to 1MHz
- (e4) RoHS Compliant Package with Gold Pad Finish
- Programmable Soft-Start
- Tiny, Low Profile (11.25mm × 15mm × 2.82mm) Surface Mount LGA Package
LTM8026 – 36Vin, 5A CVCC Step-Down µModule Regulator – [Link]
You may have already had an application, where it would have been suitable to use a switched power supply, but when you saw a datasheet, you rather used a classic proven linear stabilizer. With the integrated circuit L5973D it is possible to design in a short time a reliable and powerful power source, at a low cost.
Switch-mode power supplies (SMPS) are being more and more used because of their undoubted advantage – much higher efficiency than classic linear stabilisers. In contrast to linear power supplies, SMPS-es have almost the same efficiency at various input/otput voltage ratios, which uses to be 80-95%. That´s why, if we need a much lower output voltage, than input voltage (e.g. 5V from 24V), an SMPS still has a very good efficiency, unlike almost catastrophic 20% at linear stabiliser. For many applications, the best solution is to use a ready-made DC/DC module or to use switch-mode stabilisers which directly replace stabilisers of 78xx series. However, for many applications a solution from discrete components is more suitable. From our offer of switch-mode regulators, we would like to introduce you a perspective circuit L5973D from ST Microelectronics.
L5973D is a switch-mode buck regulator (step down) with the integrated 2.5A output transistor P-FET D-MOS, working at 250kHz frequency, in a HSOP-8 package. Input voltage can be 4-36V and an output voltage can be from 1,235 to 35V. For a construction of power source, only minimum of external components are necessary. Thanks to the integrated output transistor, it is easy to reach an optimal components layout and short power tracks on PCB. That´s why it is much easier to reach a minimum interference (EMI) in comparison to a solution with external switching transistor. L5973D contains a thermal protection, as well as an overcurrent protection, which limits a maximum current in every cycle. Cooling is provided by a thermal pad on the bottom side of the circuit. A big advantage is, thet the circuit is able to work even with the low drop-out (LDO) and the duty cycle 100%, i.e. if the inpout voltage is getting closer to the output voltage (for example a discharging accumulator), L5973D can carry over to the output practically the same voltage as it has on the input (voltage feedforward). This is especially useful at battery applications, when we need to ensure functionality of the device even in critical conditions. Read the rest of this entry »
The app note featured here provides basic PCB layout tips for building switch-mode DC/DC converters. As an integral part of their function, switch mode converters have square like signals in some of their traces. These signals create harmonics from the switching frequency that can cause much EMI interference, as well as decreased stability of the converter. [via]
This note by Maxim helps eliminate these and some other issues that might arise form using switch-mode converters.
- Place and route the power components. Start placing switching transistors Q1 and Q2, inductor L, and input and output capacitors CIN and COUT. Arrange them so as to minimize the distances between them, in particular the ground connections of Q2, CIN and COUT, and the CIN and Q1 connection. Next, create top-layer shapes for the power ground, input, output, and LX nodes, and route them on the top layer using wide short traces.
- Place and route the low-level signal components. The controller IC should be placed close to the switching transistors. Low-level signal components are placed on the other side of the controller. High-impedance nodes are kept small and away from the LX node.
- Create an analog ground shape on a suitable layer and connect it to power ground at one point.
App note: Board layout tips for switchmode DC/DC converters – [Link]
With transformers for switch-mode power supplies from company Myrra you can avoid a demanding high frequency transformer design and you can focus only on a design of an SMPS according to your own specific demands.
For a power supply solution it is often more effective to use ready-made DC/DC or AC/DC modules. However if you need a power source with non-standard output voltage or if you decide from any reason for your own design of an switch- mode power supply (SMPS) like flyback or push-pull, you will need a suitable high frequency transformer.
Transformers of the 740xx series from company Myrra offer advantage in a fact, that they are optimized directly for usage with a certain control circuit (chip). That´s why they eliminate a necessity of relatively demanding design of custom transformer, or extensive comparing of parameters according to which you´d have to choose a suitable type. All you need is to choose a transformer of desired power rating and in its datasheet you will find a recommended SMPS control circuit. With some transformer types you can use more types of SMPS control circuits. Transformers provide a high level of safety – they are made of exclusively UL94-V0 listed materials and they feature a high primary/secondary insulation of more than 4000V. You can find appropriate datasheets at given transformer types listed under this article.
To design your own transformer? – No! – [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]