Abstract: This paper proposes a pulse width modulation (PWM) control scheme based on dual-amplitude active clamp resonant DC link inverter technology to change the status quo that traditional resonant DC link inverters can only use discrete pulse modulation (DPM) control. While maintaining the advantages of simple circuit structure and soft switching, the scheme enables the inverter to have higher efficiency and significantly improves the output spectrum. The working principle of the PWM control scheme is given. The feasibility and superiority of the control scheme are proved through simulation and experiment of a 3kW experimental system. Keywords: Inverter, pulse width modulation, resonant/dual-amplitude control, resonant DC link 1 Introduction Active clamp resonant DC link inverter (ACRDCLI) realizes soft switching of inverter elements. It has the advantages of simple structure and high efficiency [1,2], but the circuit still has two problems: ① The DC link loss is too large, which limits the application of ACRDCLI in high-power applications; ② Because the inverter switch can only commutate when the bus voltage crosses zero, the control scheme can only use discrete pulse modulation (DPM) mode. Although the dynamic response of the DPM mode is good and the stability is high, the output waveform contains a lot of interharmonics, which seriously affects the accuracy of the waveform and causes a lot of harmonic loss. Traditional PWM control technology can enable the inverter to obtain the optimal output spectrum. For example, the harmonic energy is concentrated at the switching frequency and is easily filtered out by the high-frequency filter. The filter is small in size and easy to design. The obtained output waveform has high accuracy. If the PWM scheme can be adopted in the resonant DC link inverter, the interharmonic problem can be fundamentally solved. However, the resonant DC link inverter is limited by the condition that the bus voltage is zero when commutating. The dual-amplitude control scheme can solve the control accuracy problem of PWM [3]. Its principle is: the bus oscillation of the DC link has two types: large amplitude oscillation and small amplitude oscillation. When the inverter needs to commutate, the resonant DC link is controlled to achieve large amplitude oscillation. At this time, the bus voltage can oscillate to zero and the inverter switch commutates under zero voltage conditions; otherwise, only a small amplitude oscillation is maintained in the DC link to ensure that the clamping switch achieves soft switching. The amplitude of small oscillations is very small, and their losses are negligible compared to large oscillations. Moreover, the frequency of small oscillations is very high; when the oscillation frequency is much higher than the inverter's switching frequency, the inverter can achieve high modulation accuracy, thus realizing PWM control. A current instantaneous value feedback control scheme based on dual-amplitude control technology for resonant DC-loop inverters is proposed. This enables the inverter to obtain PWM output, optimizing the inverter's output performance. Simulation and experiments demonstrate the effectiveness of this control scheme. For details, please click: PWM Control Scheme for Active Clamped Resonant DC-Loop Inverters