Design of a digital PWM module with independent carrier amplitude modulation control

Abstract

PWM (Pulse Width Modulated) signal generation is known to be the core of power electronic circuits that enable achieve necessary control strategies. The PWM generation modules available on digital controllers offer a limited control over PWM carrier amplitude. At high switching frequencies, the vertical resolution is also reduced. In the common hardware based digital PWM implementations in microcontrollers and digital signal processors (DSPs), higher carrier frequency results in lower carrier amplitude and vice versa. This limits the resolution of the PWM generation module especially at high frequency. Some control algorithms can demand independent and dynamic control of the carrier amplitude irrespective of the duty cycle. Inverter control algorithms are easier to implement with the availability of hardware based on bipolar-carrier PWM generation module. In this paper, a new PWM generation module is proposed which leverages floating-point based implementations to give independent control over PWM carrier amplitude, irrespective of the frequency. Using this method, a PWM carrier with large range of the carrier amplitude preserving its high resolution can be achieved. This gives a large independence of choosing the vertical amplitude of the carrier signal, irrespective of its frequency. The proposed PWM module is written in Verilog Hardware Descriptive Language (HDL), simulated using Modelsim simulator, implemented on Cyclone-V FPGA and verified experimentally.