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　　Greatly reduce the total group delay! Analysis of examples of digital power multi-frequency technology

　　Power converter topologies have been based on analog technology for decades. Although most converters use switching technology and pulse width modulation (PWM), the circuit configuration is mainly analog due to compatibility with power semiconductor devices at the processing level and cost-effectiveness considerations. However, this is changing. In the process of dramatically improving the efficiency of data centers and telecommunications systems, analog technology and its circuits have exposed their shortcomings.

　　Digital power management and control provides real-time intelligence, allowing system developers to build power systems that automatically adapt to changes in the operating environment and optimize efficiency for each specific application. Intelligent digital power ICs can automatically compensate for changes in load and system temperature, utilizing adaptive dead-time control, dynamic voltage regulation, frequency shift, phase number reduction and current discontinuity mode switching to achieve energy savings.

　　The perceived cost of digital power supplies has been an obstacle to rapid adoption, but new devices, such as Intersil's ZL8800, are quickly closing the price gap between analog and digital control. Digital power efficiency and cost are now equal to or better than analog power conversion solutions while offering more advanced capabilities.

　　Best of all, pulse-width modulation (PWM), loop control and feedback are digital. The analog signal is converted into a digital signal using an analog-to-digital converter (ADC). After the signal is digitally converted, a microcontroller, digital signal processor, or computational state machine can control the digital pulse width modulation and feedback loop. This has the important advantage of maintaining stability without the slow response speed that often occurs with analog controls.

　　Although digital control has many advantages, a large number of manufacturers do not take full advantage of this technology. In many cases, only the core analog PWM technology is adopted in digital form. Digital control allows for a more flexible control loop, using multi-frequency control to adjust each algorithm to handle events occurring at different speeds.

　　Traditional digital PWM controllers use uniform sampling. The controller collects output voltage error samples and calculates the duty cycle required for the next switching cycle based on the sampling results. The disadvantage of the uniform sampling controller is that there is a delay or group delay from the error sampling to the PWM controller switching power circuit. Group delay causes phase lag, which increases with frequency and limits the maximum closed-loop bandwidth.

　　Multi-frequency control provides stable power and can respond to sudden changes in voltage almost immediately, within a PWM switching cycle. The only way this conversion architecture can achieve this capability is by utilizing variable frequency switching technology, which employs higher frequency sampling and control when voltage changes rapidly. But this approach is not suitable for many systems. Modern telecommunications equipment and other applications with strict electromagnetic compatibility requirements need to operate at fixed frequencies to maintain a tightly controlled noise spectrum.

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