Digital perturbation injection technique for open loop frequency response measurement of Boost converter

The open loop response of a power converter is an important parameter in designing stable and rugged system. Open loop response can be obtained by injecting a sinusoidal signal having frequency variation from few hertz to half the switching frequency. Analog sinusoidal signal injection suffer from noise pick up due to switching action of semiconductor devices, leading to inaccurate system characteristics. This paper presents a method of injecting sinusoidal perturbation signal to the pulse width modulated signal in the digital domain to obtain open loop response of a boost converter. Digital perturbation injection technique is simulated in MATLAB and experiments are conducted on a 1kW boost converter operating in continuous conduction mode.