Power conversion is the basis of various electronic product designs. In order to meet different applications and product requirements, power conversion, voltage regulation, isolation and other treatments are needed to ensure the stable operation of devices, modules and systems. This article will show you the important applications and development directions of power conversion and the power conversion solutions introduced by ADI.
Three DC-DC converter types and performance differences
There are various types of power conversion, including alternating current (AC) to direct current (DC) power conversion, AC to AC power conversion, and DC to DC power conversion. Take DC-DC conversion as an example. There are three basic DC-DC converter types: unregulated switching power supply or module, regulated switching power supply or module, and chip-scale power converter. Adopting these power supply structures will increase the complexity of the control circuit, while the first two types also require an increase in the number of components and the size of solutions.
An unregulated power supply is a relatively simple solution. The cost of this kind of solution is mainly from a transformer. If the quantity is appropriate, the cost of a discrete solution is less than $1.00. Although the cost is very low, the output voltage in the load and temperature range may vary greatly, making the selection of analog solutions more difficult. All analog solutions must have excellent power supply rejection performance, and the load cannot change rapidly. Otherwise, the power supply will change greatly. Therefore, the efficiency of unregulated power supply may be quite high, but the power supply quality is very low.
Regulated power supplies and modules provide better output characteristics. Similar to the unregulated power supply solution, the controller switches power to the transformer. The power efficiency of such a solution is very good at high loads and poor at low loads. There are many active regulated power supply solutions that can improve the efficiency in the full load range. Still, they require much more complex control circuits, and most of them require a feedback channel on the isolation barrier, which greatly increases the design cost and size.
The chip-scale converter technology developed by ADI for iCoupler® digital isolator products has resulted in a new class of DC-DC converters. This technology is very suitable for low power consumption and high performance power supply design. Because the transformer is tiny enough to be integrated into the standard IC package with internal split lead frame, the chip-scale power converter can integrate all the functions of a fully regulated DC-DC power supply, and has compact voltage regulation characteristics and good efficiency at low load.
Chip-scale converters have better power conversion advantages
Most designers need to achieve high power efficiency designs. Unregulated solutions are usually efficient, but their efficiency will decrease rapidly when the output voltage is significantly higher than the rated value. The second most efficient is the voltage regulator module, which is designed for light loads and has good characteristics. However, when compared with chip-scale converters, the efficiency of chip-scale converters can rise to the final value faster because they integrate active feedback regulation. It is still a better choice, although the maximum efficiency of chip-scale solutions is low.
The size is the next point of comparison of these solutions. The area of the modular solution on the PCB is 180 mm2. The height of the unregulated module is 10 mm, so it not only takes up board space, but is probably the highest part of the board, which determines the theoretical housing size of the module. The wise choice is also a chip-scale module with a thin SSOP20 JEDEC standard package, 55 mm2 in size, some bypass capacitors, and two resistors.
The last factor that differentiating modular/discrete solutions from chip-scale solutions is the frequency of operation. Switching current will bring noise and ripple to the power supply. In many cases, modules operate in the frequency range of 200 kHz to 1 MHz, and data must be properly filtered or anti-aliased to prevent it from being affected by power supply noise. The primary power oscillator of the chip-scale solution operates at 125 MHz. Although the PWM control of the power oscillator still causes a ripple, the maximum noise source is higher than the bandwidth of the ADC, which can be easily filtered out.
Small-sized and completely isolated integrated DC/DC converter
ADI’s chip-scale solution, the ADuM5010, is an isoPower integrated isolated DC/DC converter based on ADI’s iCoupler® technology that delivers regulated isolated power supplies adjustable between 3.15 V and 5.25 V for up to 150 mW of output power. The input power supply voltage can be slightly lower than the required output or much higher than the required output. Using iCoupler chip-scale transformer technology, the logic signal can be isolated from the magnetic components of a DC/DC converter. Therefore, a small form factor and completely isolated solution can be provided.
The ADuM5010 is available in a 20-lead SSOP package with a creepage of 5 mm and operating temperatures up to 105℃. With high common-mode transient immunity greater than 25 kV/μs, it can be widely used in power start-up bias and gate drives, isolated sensor interface and industrial PLC.
Ideal for isolated analog inputs, the ADuM5010 consumes 150 mW and offers a combination of features typically available only in high-power DC-DC converters. This device is a power-only model in the family of devices that combine power with isolated data channels. In this family, devices with higher channel numbers will continue to be introduced, so that engineers can safely and easily apply power supply with little design work.
ADI has also introduced the ADuM5010 evaluation kit, the EVAL-ADuM5010EBZ, which supports the ADuM5010 and ADuM6010 150 mW isolated power modules. It provides a JEDEC standard SSOP20 pad layout and supports setting the required output voltage, setting enable controls, and providing multiple positions for onboard loads and bypass capacitors. isoPower devices use high-frequency and high-power switching circuits to realize power transmission across chip-scale and air-core transformers. The PCB and power module of the evaluation board can meet the requirements of CISPER22 Class A or Class B, depending on the voltage and load range.
Analog sequence generator provides reliable power-on and power-off sequences
Today's electronic applications usually require more than one 5 V or 3.3 V supply voltage. It is also common to require 10, 20 or more voltages. In addition, there are voltage domains that have the same voltage level but must be generated separately as domains. That is, these voltages must be generated twice. One example is to implement two identical voltages to power analog and digital load. This separation can prevent mutual interference and supplies energy for various loads at various times.
In systems with multiple supply voltages, the ability to monitor different voltages will be important. What seems trivial in a system with only two voltage domains will become very complicated for many voltages. Therefore, many sequencing devices must also have built-in supervisor or voltage monitoring functions.
ADI's ADM1186-1 analog sequence generator IC can control and monitor four voltage domains. The voltage is powered on and off by controlling the enable (on/off) pin of the corresponding voltage converter. The turn-on time of the voltage converter can be adjusted by using the time delay of small capacitors, and the corresponding monitoring pins monitor the corresponding output voltage. After all the voltages are established, the sequence generator circuit will generate a power-good signal.
Analog sequencing solutions such as the ADM1186-1 are fairly easy to use and have all the functionality required for multi-voltage systems. They differ from digital sequence generators because they are less complex in design and require fewer digital monitoring functions in the system. For example, they can work without PMBus or similar protocols. When sequencing and monitoring systems with more than four voltage domains, multiple ADM1186-1 circuits can be combined in sequence, and any number of ADM1186-1 sequence generators can be connected.
The ADM1186-1 stands out in that it also supports complete sequencing during power-on and power-off when used in linked applications. Similar solutions can provide the possibility of linking various sequencer ICs. Still, they only provide a controlled ramp-up of a single voltage, not a controlled down-sequencing order, that is, turning off the voltage in this daisy-chain constellation.
Highly configurable, multi-output cascade buck converter
Since the acquisition of Linear by ADI, combining Linear's power products with ADI's power management products can bring customers the best power solution. LTC3372, for example, is a highly integrated DC-DC converter solution for automotive, telecommunications, industrial and other applications requiring multiple low-voltage rails from input voltages up to 60V. The LTC3372 consists of both high and low voltage converter systems in its heat-resistant, enhanced 48-lead, 7 mm × 7 mm package. The high voltage (HV) buck controller can buck input voltages up to 60V to pin-programmed 5V or 3.3 V and then use the 5V or 3.3V output as a configurable, multi-output, multi-phase supply low voltage (LV) monolithic buck regulator of the LTC3372.
This low voltage portion of the LTC3372 consists of eight 1 A, parallelable power stages. These stages can be arranged in a variety of ways to provide two, three, or four channels, each of which consists of one to four stages, depending on the load requirements of each channel, and up to eight different configurations can be set up. This level of flexibility allows designers to use one IC for various designs with minimal external components and a small overall footprint. In addition, the output of each channel can be set to 0.8 V to LVIN. The switching frequency ranges from 1 MHz to 3 MHz.
The LTC3372 provides designers with a flexible, highly integrated solution for delivering multiple outputs from high input voltages. Its HV converter can provide an output of 5 V or 3.3 V from input voltages up to 60 V. From this intermediate rail, the monolithic LV regulator can provide up to four outputs, with the maximum output current range from 1 A to 4 A and the voltage as low as 0.8 V.
Conclusion
Power conversion is the key work of electronic product design. Adopting good power design and suitable power conversion devices will be the foundation of successful product design. The various ADI power conversion devices introduced in this article will meet your various needs in different applications, and deserve your further understanding and adoption.