With the advent of cost-effective and powerful processors in the marketplace, digital solutions have entered a number of what were previously purely analog systems. For example, high-quality electric motors today are almost exclusively digitally controlled, using microcontrollers or DSPs. Motor speed and torque can be variably and precisely set due to the secondary control of current and voltage.

This isn't yet the case in related applications, such as current or voltage supply in power supplies, in which the control of amplitudes and frequencies of current and voltage must be performed. Analog control systems still dominate these areas, though the trend here also is moving toward digital control.

Full digital control of switching-mode power supplies offers a number of major advantages. The ability to control the power-supply operation through software often makes it possible for a single hardware implementation to meet the precise needs of a wide range of different products. Furthermore, designers can easily upgrade power supplies simply by installing new firmware. Digital power-supply control also offers the potential to provide much more powerful control functions, including adaptive control routines that adjust power-supply output based on operating or environmental conditions.

The advent of digitally controlled power supplies, though, raises some significant performance issues. Analog controllers are based on continuous time, so performance usually isn't a limiting factor. Digital controllers, on the other hand, must address time quantization effects. Such controllers are driven by a system clock that generates granular time steps. The steps depend on the system clock frequency and the switching frequency. The resolution (in bits) of a digital pulsewidth- modulation (PWM) controller is proportional to the system clock speed and is inversely proportional to the switching frequency, as indicated by:

A new generation of digital signal controllers (DSCs) addresses these challenges, making it practical to develop full digital power supplies for a much more demanding range of applications. These controllers typically offer a modern 32-bit DSP core with a 100- or 150-MHz clock frequency; a 16-channel, 12-bit analog-to-digital converter (ADC); flexible logic for the generation of PWM signals; and numerous serial and parallel interfaces. Such features enable the design of full digital control systems that provide analog-like PWM granularity while only requiring 30- to 100-MHz system clock rates.