A peak current mode ‘PCM’ controller comprising control logic arranged to produce a series of digital control values derived from a voltage sense signal, control logic arranged to produce a digital slope compensation value, a first digital to analogue converter ‘DAC’ arranged to receive the series of digital control values and output a corresponding analogue control voltage, a second DAC arranged to receive the digital slope compensation value and output a corresponding analogue slope compensation voltage, an analogue differential integrator arranged to receive the analogue control voltage and the analogue slope compensation voltage, integrate the analogue slope compensation voltage, subtract the integrated slope compensation voltage from the analogue control voltage, and output the result of the subtraction as an analogue output voltage, a comparator arranged to compare the analogue output voltage to a voltage of an analogue current sense signal and produce an output signal when the analogue current sense signal voltage is equal to or exceeds the analogue output voltage, and control logic arranged to produce a drive signal in response to the output signal.