A DC-DC converter adapted to power an OLED array, the DC-DC converter having an input receiving DC input power and an output coupled to the OLED array, the DC-DC converter comprising: first and second switching devices (Q1, Q2) coupled in series between first and second DC input terminals (110a1, 110a2), the first and second switching devices (Q1, Q2) being joined at an internal node, a driver including a driver control input, the driver operative to provide first and second switch control signals in complementary fashion to the first and second switching devices (Q1,Q2), respectively, at least partially according to a signal received at the driver control input, a filter circuit coupled between the internal node and the DC-DC converter output, and a PWM circuit, comprising: an error amplifier with a first input receiving a converter setpoint signal, a second input receiving a feedback signal representing current supplied to the driven OLED array, and an error amplifier output providing an error signal representing a difference between the converter setpoint signal and the feedback signal, characterised in that: the PWM circuit further comprises a PWM controller with an input connected to the error amplifier output to receive the error signal, the PWM controller operative to provide a pulse width modulated signal to the driver control input according to the error signal; and the DC-DC converter further comprises a waveform generator adapted to receive an input setpoint signal, the waveform generator operative to provide the converter setpoint signal to the PWM circuit at least partially according to the input setpoint signal, the converter setpoint signal having rise time finite values of 1us or more and 10ms or less, and fall time finite values of 1us or more and 10ms or less. first and second switching devices (Q1, Q2) coupled in series between first and second DC input terminals (110a1, 110a2), the first and second switching devices (Q1, Q2) being joined at an internal node, a driver including a driver control input, the driver operative to provide first and second switch control signals in complementary fashion to the first and second switching devices (Q1,Q2), respectively, at least partially according to a signal received at the driver control input, a filter circuit coupled between the internal node and the DC-DC converter output, and a PWM circuit, comprising: an error amplifier with a first input receiving a converter setpoint signal, a second input receiving a feedback signal representing current supplied to the driven OLED array, and an error amplifier output providing an error signal representing a difference between the converter setpoint signal and the feedback signal, an error amplifier with a first input receiving a converter setpoint signal, a second input receiving a feedback signal representing current supplied to the driven OLED array, and an error amplifier output providing an error signal representing a difference between the converter setpoint signal and the feedback signal, the PWM circuit further comprises a PWM controller with an input connected to the error amplifier output to receive the error signal, the PWM controller operative to provide a pulse width modulated signal to the driver control input according to the error signal; and the DC-DC converter further comprises a waveform generator adapted to receive an input setpoint signal, the waveform generator operative to provide the converter setpoint signal to the PWM circuit at least partially according to the input setpoint signal, the converter setpoint signal having rise time finite values of 1us or more and 10ms or less, and fall time finite values of 1us or more and 10ms or less.