A Novel Digital Architecture for Gain and Phase Measurements for DC-DC Converters

The proposed gain and phase (GAP) measurement architecture is a digitally-implemented device, which is used to measure the gain and phase of DC-DC voltage converters. The device excites the system under test with a small-signal sinusoidal test signal and measures both the time histories of the test signal and the response signal. The device sweeps different frequency points using the direct-digital-synthesis (DDS) technique. Further, to achieve a wide dynamic range, the phase and amplitude response (Bode plot) are calculated using the Lock-in amplifier technique. The device has the flexibility of sampling the response in either the off-time, the on-time or at any other time (average) sampling of the power switch for the DC-DC converter. Furthermore, the proposed system is integrated with a graphical user interface (GUI) which communicates with the device. Through the GUI the user may select to perform measurements such as the transfer function of the plant, the open loop and the closed loop of the controller, measurement of audio susceptibility, total harmonic distortion and noise (THD+N) and ripple spectrum. The GUI can also be used to design a Pulse Width Modulation (PWM) linear controller on the fly, estimating the open loop response T(s), the closed loop response T(s)/(1+T(s)) and the inverse loop response 1/T(s). Analysis of the proposed system is provided, alongside with various applications and experimental results.