A Self-Starting Class-E Power Oscillator With an Inverting Gate Driver

Abstract

This article presents a simple Class-E power oscillator (PO) which autonomously starts oscillating without requiring an additional start-up circuit. This has been achieved through the use of an inverting gate driver that drives the switching transistor. A resistor, connecting the input to the output of the gate driver, biases the driver at its switching threshold voltage, at which it has high ac gain. In addition, the inverting driver introduces a minimum of −180° phase shift. As a result, the Barkhausen oscillation criteria are readily satisfied and the PO starts oscillating autonomously. In order to allow the use of an inverting gate driver, a new and simple feedback network, consisting of only two resistors and a capacitor, is proposed. Due to the feedback network being a low-Q nonresonant circuit, the efficiency and the output power of the proposed circuit have negligible sensitivities to the variations in the components. A semianalytical design procedure is also presented for the proposed circuit. A prototype circuit was built and tested to prove the proposed concepts. At V DD = 4.5 V, the measured output power, efficiency, and oscillation frequency of the prototype PO are 1.02 W, 92%, and 800 kHz, respectively.