Multi-level envelope tracking systems with separate DC and AC paths
Multi-level envelope tracking systems are disclosed. In certain embodiments, a method of envelope tracking includes amplifying a radio frequency signal using a power amplifier, supplying power to the power amplifier using a power amplifier supply voltage, generating a plurality of delay-controlled regulated voltages based on controlling a delay of a plurality of regulated voltages using a controllable delay circuit, generating a modulator output voltage at a modulator output of a modulator, providing filtering using a first filter coupled between the modulator output and the power amplifier supply voltage, and controlling activation of a plurality of switches of the modulator based on an envelope of the radio frequency signal. The plurality of switches are each coupled between the modulator output and a corresponding one of the plurality of delay-controlled regulated voltages.
1. An envelope tracking system comprising:
a power amplifier configured to amplify a radio frequency signal and to receive power from a power amplifier supply voltage;
a controllable delay circuit configured to generate a plurality of delay-controlled regulated voltages based on controlling a delay of a plurality of regulated voltages;
a modulator including a modulator output configured to generate a modulator output voltage, a plurality of switches each coupled between the modulator output and a corresponding one of the plurality of delay-controlled regulated voltages, and a modulator control circuit configured to control activation of the plurality of switches based on an envelope of the radio frequency signal; and
a first filter coupled between the modulator output and the power amplifier supply voltage.
2. The envelope tracking system of claim 1 further comprising a second filter coupled between a DC voltage and the power amplifier supply voltage.
3. The envelope tracking system of claim 2 wherein the controllable delay circuit is operable to control a relative delay between an AC path through the first filter and a DC path through the second filter.
4. The envelope tracking system of claim 2 further comprising a DC-to-DC converter configured to generate the DC voltage and the plurality of regulated voltages.
5. The envelope tracking system of claim 2 wherein the second filter includes at least one series inductor and at least one shunt capacitor.
6. The envelope tracking system of claim 1 wherein each of the plurality of regulated voltages has a different voltage level.
7. The envelope tracking system of claim 1 wherein the first filter includes at least one series inductor and at least one shunt capacitor.
8. The envelope tracking system of claim 1 wherein the first filter further includes a DC blocking capacitor in series between the modulator output voltage and the power amplifier supply voltage.
9. The envelope tracking system of claim 1 wherein the controllable delay circuit includes a plurality of controllable delay buffers each configured to control a delay of a respective one of the plurality of regulated voltages.
10. The envelope tracking system of claim 1 further comprising a DC-to-DC converter configured to generate the plurality of regulated voltages.
11. A mobile device comprising:
a transceiver configured to generate a radio frequency signal;
a front end circuit including a power amplifier configured to amplify the radio frequency signal and to receive power from a power amplifier supply voltage; and
a power management circuit including a controllable delay circuit configured to generate a plurality of delay-controlled regulated voltages based on controlling a delay of a plurality of regulated voltages, a modulator including a modulator output configured to generate a modulator output voltage, and a first filter coupled between the modulator output and the power amplifier supply voltage, the modulator further including a plurality of switches each coupled between the modulator output and a corresponding one of the plurality of delay-controlled regulated voltages and a modulator control circuit configured to control activation of the plurality of switches based on an envelope of the radio frequency signal.
12. The mobile device of claim 11 wherein the power management circuit further includes a second filter coupled between a DC voltage and the power amplifier supply voltage.
13. The mobile device of claim 12 wherein the controllable delay circuit is operable to control a relative delay between an AC path through the first filter and a DC path through the second filter.
14. The mobile device of claim 12 wherein the second filter includes at least one series inductor and at least one shunt capacitor.
15. The mobile device of claim 11 wherein each of the plurality of regulated voltages has a different voltage level.
16. The mobile device of claim 11 wherein the first filter includes at least one series inductor and at least one shunt capacitor.
17. The mobile device of claim 11 wherein the first filter further includes a DC blocking capacitor in series between the modulator output voltage and the power amplifier supply voltage.
18. The mobile device of claim 11 wherein the controllable delay circuit includes a plurality of controllable delay buffers each configured to control a delay of a respective one of the plurality of regulated voltages.
19. The mobile device of claim 11 wherein the power management circuit further includes a DC-to-DC converter configured to generate the plurality of regulated voltages.
20. A method of envelope tracking, the method comprising:
amplifying a radio frequency signal using a power amplifier;
supplying power to the power amplifier using a power amplifier supply voltage;
generating a plurality of delay-controlled regulated voltages based on controlling a delay of a plurality of regulated voltages using a controllable delay circuit;
generating a modulator output voltage at a modulator output of a modulator;
providing filtering using a first filter coupled between the modulator output and the power amplifier supply voltage; and
controlling activation of a plurality of switches of the modulator based on an envelope of the radio frequency signal, the plurality of switches each coupled between the modulator output and a corresponding one of the plurality of delay-controlled regulated voltages.