In the illustrated embodiment, the envelope tracking system 180 operates with a DC path delay t₁ from the MLS DC-to-DC converter 72 to a supply input of the power amplifier 71 through the DC path filter 73. Additionally, the envelope tracking system 180 operates with an AC path delay t₂ from the MLS DC-to-DC converter 72 to the supply input of the power amplifier 71 through the controllable delay circuit 98, the MLS modulator 81, and the AC path filter 91.

By including the controllable delay circuit 98, a relative delay between the AC path and the DC path can be controlled to enhance the efficiency of the envelope tracking system 180. In certain implementations, a delay of the controllable delay circuit 98 operates to substantially match the DC path delay t₁ and the AC path delay t₂ with a desired phase shift to enhance efficiency.

For example, absent compensation for the difference in delay, currents of the AC path and DC path can fight due to the control bandwidth of the DC path being smaller than the control bandwidth of the AC path. In this example, the AC path is delayed by the controllable delay circuit 98 to control a relative delay of the DC path as seen by the load. In certain implementations, a phase shift of about 90 degrees across the bandwidth where combining occurs provides relatively high efficiency. In certain implementations, a digital state machine or other suitable control circuit operates to provide control that achieves about 90 degrees of phase delay.