Power supply applications with digital control implementation
Kevin Huang / TWMW
Translated by Dr. Wen Wu
Translated by Dr. Wen Wu
There are many figures of merit to evaluate the performance of power supply system such as efficiency, power density, voltage regulation, reliability, price / supplying power ratio, electromagnetic interference…etc.
The control of the conventional power supply is mainly realized in analogous way which has advantages of low cost, simple circuity design and fast response. However, limited application or single purpose of an analog power supply is quite controversial due to simple interface not easy or suitable to be integrated into complex power system and challengeable fine-tuning process for control loop compensation during the design phase and so on.
The solution is a programmable power converter which is digitally designed and with different operating modes and/or control parameters via software settings to meet the needs from different applications.
The main purpose of power management is to get an optimized operating procedure between the various and fast-changing type of loads and demands. To achieve it, the microprocessor is implemented to realize the dynamic needs of power management function through software control. Hence, a power supply with digital control design is recently becoming important.
MEAN WELL has been developing products with digital control for a while and a lot of selections is available now.
Digital power supply design type and its definition
Digital power supply can be divided into two categories:
First one is analog power supply with digital interface communication [power management] design. The examples are the management of bus (PMBus) and I2C power management solutions. It provides digital interface functions that depend on user requirements. The basic functions including voltage/current/temperature reading up to complex instructions that can change the output power of the internal analog power supply.
Second category is 100% digital control of the [power product] design.
The design of pure digital power supply can further be divided into three types:
- Use of digital signal processor (DSP) to design the digital power solutions.
- Use of microcontroller (MCU) as the core of the digital power solutions.
- Use of programmable logic gate array (FPGA) to design the digital power solutions.
The output voltage and current adjustment of the power supply is realized by controlling the pulse width modulation(PWM) signal from the controller implemented by DSP, MCU or FPGA to the analog switching components.
Various circuitry topology, for example, full bridge, half bridge, forward, flyback and so on can be implemented to AC-DC converter s depending on power level. Also, power factor correction is required in case the output power is higher and is defined by the relevant standard. For such type of design, it is suggested to select DSP platform due to its faster computing capability and achieve the flexibility required by the digital power system.
For general DC-DC converter applications, it is more focusing on power conversion efficiency and real-time monitoring. For such type of design, it is suggested to select MCU chip to achieve low-cost requirements.
As for the design selecting of FPGA, it tends to be DC-DC converter applications with more focus on data processing. In case FPGA is selected for AC-DC converter application, it would need additional Analog / Digital converting device which makes the limitation on the flexibility.
MEAN WELL digital power product roadmap
According to market demand, MEAN WELL has been developed digital control product development since 2007, which is more than ten years from now. The product categories include AC-DC converter, DC-AC inverter, battery charger, LED driver and other types of products.
Programmable LED lighting control products (DALI)
Digital Addressable Lighting Interface (DALI) is the digitized addressable dimming interface. Currently MEAN WELL has completed a quite a lot series with DALI function on various product family. The design is quite well-established for us.
A lighting system conforming to the DALI standard is sending a command to the bus at each electrical control gear (ECG) which makes the appropriate response, such as dimming, adjustment parameters or returning the status. User can control the light to meet all kind of needs based on different applications.
Intelligent battery charger
MEAN WELL has launched a series of intelligent chargers with features including false voltage connection, reverse battery protection, no battery detection and battery failure detection. The MCU is used to perform the power management providing two-stage (simple fast charging), three-stage (floating after fast charging) or eight-stage (optimized charging) charging functions. The user can select the appropriate charging curve based on the needs.
A specific charging curve may be required due to different types or brands of batteries (lead-acid batteries such as flooded cells, gelled electrolyte, absorbed glass mat (AGM); lithium batteries such as lithium iron phosphate, lithium ion manganese and others). The user-changeable curve and relevant parameters settings can be done through the internal firmware changes which is perfect to achieve various needs for customization.
It is also possible to modify any charging stage which could be charging voltage, charging current, cut-off voltage / current and other parameters. Moreover, the specific protection mechanism can be cancel via firmware.
True sine wave converter (Inverter)
DC-AC true sine wave inverter series has been implemented with MCU for digital control. The output voltage, frequency, turn on/off the power saving mode, switch between the uninterruptible power mode or the power saving mode can be parameterized through the panel buttons or via the monitoring software by PC.
Some products have built-in with AC charger and solar charger. When an external battery pack and solar panel are installed, a green energy-saving stand-alone power supply station can be constructed to meet the green energy saving demands.
MEAN WELL has also developed single-phase grid-connected solar energy converter which can effectively convert the energy from solar modules to feed into the power grid. This approach achieves best efficiency in terms of power generation and energy saving.
This grid type inverter uses DSP as internal processor which uses advanced digital control technology and data-processing to improve the conversion efficiency and provide the additional features. The software provides the remote monitoring function which is quite convenient for user to monitor and data-logging without using additional component or system.
New generation of power supply with high power density (1U profile)
New power supply implements the DSP to provide the fully digital design such that several key features can be considered during the planning of design. These features including thermal distribution, programmable functions and energy saving can be further improved and optimized to meet the requirement of various applications and fulfil expectations from users. For instance, the programmable output voltage and current setting function for certain applications is one of features provided by power supply with fully digital control design.
In addition, for high power demands, the parallel function by digital control makes it still stable while the number of parallel unit is greatly increased. Combined features of programmable output voltage/current setting and parallel functions can fully meet the needs of different users and provide for the best choice for power equipment solution.
The product with digital design provides the complete monitoring parameter, the accurate output voltage, and current control and the flexible control of energy sharing.
MEAN WELL has been developing of digital intelligent product with quite fruitful results in terms of wide and deep product range. We commit to continuous put the effort focusing on power supply system, intelligent lighting, and building automation to ensure our competence and full product category in the future.