Envelope tracking circuit and related power amplifier apparatus

1. An envelope tracking (ET) circuit comprising:

a supply voltage circuit configured to generate a plurality of constant voltages;

a target voltage circuit configured to generate a plurality of ET target voltages based on a reference target voltage; and

an ET voltage circuit configured to:

receive the plurality of constant voltages from the supply voltage circuit;

receive the plurality of ET target voltages from the target voltage circuit; and

generate a plurality of ET modulated voltages based on the plurality of ET target voltages and a selected constant voltage among the plurality of constant voltages.

2. The ET circuit of claim 1 wherein the target voltage circuit is further configured to:

receive the reference target voltage corresponding to a dynamic voltage range;

offset the reference target voltage to a baseline reference voltage corresponding to the dynamic voltage range;

determine a plurality of slope factors;

multiply the plurality of slope factors with the dynamic voltage range to generate the plurality of ET target voltages, respectively;

adjust the plurality of ET target voltages based on a plurality of offset factors, respectively; and

provide the plurality of ET target voltages to the ET voltage circuit.

3. The ET circuit of claim 2 wherein the target voltage circuit comprises:

a first offset converter configured to offset the reference target voltage to the baseline reference voltage;

a plurality of multipliers coupled in parallel to the first offset converter and configured to:

receive the plurality of slope factors, respectively; and

multiply the plurality of slope factors with the dynamic voltage range to generate the plurality of ET target voltages, respectively; and

a plurality of second offset converters coupled to the plurality of multipliers and configured to:

receive the plurality of offset factors, respectively; and

adjust the plurality of ET target voltages based on the plurality of offset factors, respectively.

4. The ET circuit of claim 1 wherein the supply voltage circuit comprises:

an inductor-based voltage circuit configured to generate a direct current (DC) voltage based on a battery voltage;

a plurality of output ports configured to output the plurality of constant voltages, respectively, wherein:

a first selected output port among the plurality of output ports is coupled to the inductor-based voltage circuit to output the DC voltage as a first selected constant voltage among the plurality of constant voltages; and

one or more second selected output ports among the plurality of output ports are configured to output one or more second selected constant voltages among the plurality of constant voltages different from the first selected constant voltage;

a capacitor-based voltage circuit coupled to the inductor-based voltage circuit and configured to generate the one or more second selected constant voltages at the one or more second selected output ports, respectively; and

a controller configured to:

receive a feedback signal indicative of a preselected constant voltage among the plurality of constant voltages; and

control the inductor-based voltage circuit to adjust the DC voltage based on the preselected constant voltage.

5. The ET circuit of claim 4 wherein the capacitor-based voltage circuit is further configured to multiply the DC voltage with one or more predefined scaling factors to generate the one or more second selected constant voltages, respectively.

6. The ET circuit of claim 5 wherein the one or more predefined scaling factors are one or more fractional scaling factors.

7. The ET circuit of claim 6 wherein the one or more second selected output ports are further configured to output the one or more second selected constant voltages in ascending voltage values.

8. The ET circuit of claim 4 wherein the supply voltage circuit further comprising a clock generator configured to generate an operating clock for the capacitor-based voltage circuit based on a reference clock configured to operate the controller.

9. The ET circuit of claim 1 wherein the ET voltage circuit comprises:

a plurality of voltage selection circuits each configured to receive the plurality of constant voltages from the supply voltage circuit; and

a plurality of voltage controllers configured to receive the plurality of ET target voltages, respectively, each of the plurality of voltage controllers is further configured to control a respective voltage selection circuit among the plurality of voltage selection circuits to output the selected constant voltage among the plurality of constant voltages as a respective ET modulated voltage among the plurality of ET modulated voltages.

10. The ET circuit of claim 9 wherein each of the plurality of voltage controllers is further configured to:

determine the selected constant voltage as equal to minimize [V DC-j ≥(V TARGET-i +V Headroom )] (1≤i≤N) (1≤j≤M), wherein:

V DC-j represents any of the plurality of constant voltages;

V TARGET-i represents a respective ET target voltage among the plurality of ET target voltages; and

V Headroom represents a predefined headroom voltage; and

control the respective voltage selection circuit to output the selected constant voltage as the respective ET modulated voltage among the plurality of ET modulated voltages.

11. The ET circuit of claim 1 wherein the ET voltage circuit comprises:

a plurality of voltage selection circuits each configured to receive the plurality of constant voltages from the supply voltage circuit;

a plurality of voltage amplifiers configured to generate the plurality of ET modulated voltages based on the plurality of ET target voltages and a plurality of supply voltages, respectively; and

a plurality of voltage controllers configured to receive the plurality of ET target voltages, respectively, each of the plurality of voltage controllers is further configured to control a respective voltage selection circuit among the plurality of voltage selection circuits to output the selected constant voltage among the plurality of constant voltages to a respective voltage amplifier among the plurality of voltage amplifiers as a respective supply voltage among the plurality of supply voltages.

12. The ET circuit of claim 11 wherein the ET voltage circuit further comprises a plurality of linear field-effect transistors (FETs) having a plurality of gate terminals coupled to the plurality of voltage amplifiers and a plurality of drain terminals configured to output the plurality of ET modulated voltages, respectively.

13. An envelope tracking (ET) power amplifier apparatus comprising:

a plurality of amplifier circuits configured to amplify a radio frequency (RF) signal based on a plurality of ET modulated voltages, respectively; and

an ET circuit coupled to the plurality of amplifier circuits and comprising:

a supply voltage circuit configured to generate a plurality of constant voltages;

a target voltage circuit configured to generate a plurality of ET target voltages based on a reference target voltage; and

an ET voltage circuit configured to:

receive the plurality of constant voltages from the supply voltage circuit;

receive the plurality of ET target voltages from the target voltage circuit;

generate the plurality of ET modulated voltages based on the plurality of ET target voltages and a selected constant voltage among the plurality of constant voltages; and

provide the plurality of ET modulated voltages to the plurality of amplifier circuits, respectively.

14. The ET power amplifier apparatus of claim 13 wherein:

the plurality of amplifier circuits is further configured to amplify the RF signal associated with a plurality of time-variant power envelopes, respectively; and

the target voltage circuit is further configured to modulate the plurality of ET target voltages to a plurality of time-variant target voltage envelopes configured to track the plurality of time-variant power envelopes, respectively.

15. The ET power amplifier apparatus of claim 14 wherein the target voltage circuit is further configured to:

receive the reference target voltage corresponding to a dynamic voltage range;

offset the reference target voltage to a baseline reference voltage corresponding to the dynamic voltage range;

determine a plurality of slope factors corresponding to the plurality of time-variant power envelopes;

multiply the plurality of slope factors with the dynamic voltage range to generate the plurality of ET target voltages, respectively;

adjust the plurality of ET target voltages based on a plurality of offset factors, respectively; and

provide the plurality of ET target voltages to the ET voltage circuit.

16. The ET power amplifier apparatus of claim 15 wherein the target voltage circuit comprises:

a first offset converter configured to offset the reference target voltage to the baseline reference voltage;

a plurality of multipliers coupled in parallel to the first offset converter and configured to:

receive the plurality of slope factors, respectively; and

multiply the plurality of slope factors with the dynamic voltage range to generate the plurality of ET target voltages, respectively; and

a plurality of second offset converters coupled to the plurality of multipliers and configured to:

receive the plurality of offset factors, respectively; and

adjust the plurality of ET target voltages based on the plurality of offset factors, respectively.

17. The ET power amplifier apparatus of claim 13 wherein the supply voltage circuit comprises:

an inductor-based voltage circuit configured to generate a direct current (DC) voltage based on a battery voltage;

a plurality of output ports configured to output the plurality of constant voltages, respectively, wherein:

a first selected output port among the plurality of output ports is coupled to the inductor-based voltage circuit to output the DC voltage as a first selected constant voltage among the plurality of constant voltages; and

one or more second selected output ports among the plurality of output ports are configured to output one or more second selected constant voltages among the plurality of constant voltages different from the first selected constant voltage;

a capacitor-based voltage circuit coupled to the inductor-based voltage circuit and configured to generate the one or more second selected constant voltages at the one or more second selected output ports, respectively; and

a controller configured to:

receive a feedback signal indicative of a preselected constant voltage among the plurality of constant voltages; and

control the inductor-based voltage circuit to adjust the DC voltage based on the preselected constant voltage.

18. The ET power amplifier apparatus of claim 17 wherein the capacitor-based voltage circuit is further configured to multiply the DC voltage with one or more predefined scaling factors to generate the one or more second selected constant voltages, respectively.

19. The ET power amplifier apparatus of claim 18 wherein the one or more predefined scaling factors are one or more fractional scaling factors.

20. The ET power amplifier apparatus of claim 19 wherein the one or more second selected output ports are further configured to output the one or more second selected constant voltages in ascending voltage values.

21. The ET power amplifier apparatus of claim 17 wherein the supply voltage circuit further comprises a clock generator configured to generate an operating clock for the capacitor-based voltage circuit based on a reference clock configured to operate the controller.

22. The ET power amplifier apparatus of claim 13 wherein the ET voltage circuit comprises:

a plurality of voltage selection circuits each configured to receive the plurality of constant voltages from the supply voltage circuit; and

a plurality of voltage controllers configured to receive the plurality of ET target voltages, respectively, each of the plurality of voltage controllers is further configured to control a respective voltage selection circuit among the plurality of voltage selection circuits to output the selected constant voltage among the plurality of constant voltages as a respective ET modulated voltage among the plurality of ET modulated voltages.

23. The ET power amplifier apparatus of claim 22 wherein each of the plurality of voltage controllers is further configured to:

determine the selected constant voltage as equal to minimize [V DC-j ≥(V TARGET-i +V Headroom )] (1≤i≤N) (1≤j≤M), wherein:

V DC-j represents any of the plurality of constant voltages;

V TARGET-i represents a respective ET target voltage among the plurality of ET target voltages; and

V Headroom represents a predefined headroom voltage; and

control the respective voltage selection circuit to output the selected constant voltage as the respective ET modulated voltage among the plurality of ET modulated voltages.

24. The ET power amplifier apparatus of claim 13 wherein the ET voltage circuit comprises:

a plurality of voltage selection circuits each configured to receive the plurality of constant voltages from the supply voltage circuit;

a plurality of voltage amplifiers configured to generate the plurality of ET modulated voltages based on the plurality of ET target voltages and a plurality of supply voltages, respectively; and

a plurality of voltage controllers configured to receive the plurality of ET target voltages, respectively, each of the plurality of voltage controllers is further configured to control a respective voltage selection circuit among the plurality of voltage selection circuits to output the selected constant voltage among the plurality of constant voltages to a respective voltage amplifier among the plurality of voltage amplifiers as a respective supply voltage among the plurality of supply voltages.

25. The ET power amplifier apparatus of claim 24 wherein the ET voltage circuit further comprises a plurality of linear field-effect transistors (FETs) having a plurality of gate terminals coupled to the plurality of voltage amplifiers and a plurality of drain terminals configured to output the plurality of ET modulated voltages, respectively.