Interference suppression for switched mode power supply with error correction
A switched mode power supply arranged to provide a switched supply at one terminal of an inductor, another terminal of the inductor being connected to a first input of an error amplifier having a reference signal at a second input, the error amplifier generating a corrected switched supply at an output in dependence on the difference between signals at its first and second inputs, there being provided a feedback path between the output of the error amplifier and the first input of the error amplifier, and further comprising circuitry for sensing a switcher interference current in the feedback path of the error amplifier, and for adjusting the corrected switched supply output to reduce the switcher interference current in the output.
1. A switched mode power supply comprising:
a first inductor arranged to receive a switched supply at one terminal;
an error amplifier having a first input connected to an other terminal of the first inductor and a second input connected to a reference signal, the error amplifier being configured to generate a corrected switched supply at an output of the error amplifier in dependence on a difference between signals at the first and second inputs;
an impedance connected between the output of the error amplifier and the other terminal of the first inductor;
a resistor connected between the other terminal of the first inductor and the first input of the error amplifier; and
a second inductor connected between the first input of the error amplifier and the output of the error amplifier.
2. The switched mode power supply of claim 1 , wherein the impedance has a value of 1/g m , where g m is the transconductance of the error amplifier.
3. The switched mode power supply of claim 1 , wherein the impedance comprises a reactive element.
4. The switched mode power supply of claim 1 , wherein the impedance is implemented as a printed circuit board track.
5. An envelope tracking power supply including the switched mode power supply of claim 1 .
6. A radio frequency (RF) amplification stage including the switched mode power supply according to claim 1 for providing a power supply to an RF power amplifier.