A switched mode power supply comprising: at least one power switch (12, 14) adapted to convey power between input and output terminals of said power supply; and a digital controller adapted to control operation of said at least one power switch (12, 14) responsive to an output measurement (V 0) of said power supply, said digital controller comprising: an analog-to-digital converter providing a digital error signal (VEd k) representing a voltage difference between said output measurement (V 0) and a reference value (Ref), a digital filter providing a digital control output based on a sum of current and previous error signals and previous control outputs; and a digital pulse width modulator providing a control signal (PWM k) to said at least one power switch (12, 14), said control signal (PWM k) having a pulse width corresponding to said digital control output, characterized in that the analog-to-digital converter further comprises a windowed flash analog-to-digital converter having a transfer function (G(z)) defining a relationship between said voltage difference and corresponding digital values, said transfer function (G(z)) having a substantially linear region at a center of a corresponding error window, said transfer function (G(z)) further comprises a first step size in said center of said error window and at least one additional step size in a peripheral region of said error window, each said at least one additional step size being larger than said first step size. at least one power switch (12, 14) adapted to convey power between input and output terminals of said power supply; and a digital controller adapted to control operation of said at least one power switch (12, 14) responsive to an output measurement (V 0) of said power supply, said digital controller comprising: an analog-to-digital converter providing a digital error signal (VEd k) representing a voltage difference between said output measurement (V 0) and a reference value (Ref), a digital filter providing a digital control output based on a sum of current and previous error signals and previous control outputs; and a digital pulse width modulator providing a control signal (PWM k) to said at least one power switch (12, 14), said control signal (PWM k) having a pulse width corresponding to said digital control output, characterized in that the analog-to-digital converter further comprises a windowed flash analog-to-digital converter having a transfer function (G(z)) defining a relationship between said voltage difference and corresponding digital values, said transfer function (G(z)) having a substantially linear region at a center of a corresponding error window, said transfer function (G(z)) further comprises a first step size in said center of said error window and at least one additional step size in a peripheral region of said error window, each said at least one additional step size being larger than said first step size. an analog-to-digital converter providing a digital error signal (VEd k) representing a voltage difference between said output measurement (V 0) and a reference value (Ref), a digital filter providing a digital control output based on a sum of current and previous error signals and previous control outputs; and a digital pulse width modulator providing a control signal (PWM k) to said at least one power switch (12, 14), said control signal (PWM k) having a pulse width corresponding to said digital control output, characterized in that the analog-to-digital converter further comprises a windowed flash analog-to-digital converter having a transfer function (G(z)) defining a relationship between said voltage difference and corresponding digital values, said transfer function (G(z)) having a substantially linear region at a center of a corresponding error window, said transfer function (G(z)) further comprises a first step size in said center of said error window and at least one additional step size in a peripheral region of said error window, each said at least one additional step size being larger than said first step size.