Current sources which are based on a switched-mode converter topology are commonly known. Current sources of this type include at least one inductive storage element, such as a choke, coupled to a load, and a pulse-width modulator. The pulse-width modulator from a constant supply voltage generates a pulse-width modulated (PWM) voltage which is applied to the inductive storage element. In this type of controller, the mean value of a current through the inductive storage element and, therefore, through the load can be adjusted by varying a duty cycle of the PWM voltage.
Producing the PWM voltage applied to the inductive storage element may involve switching processes which cyclically connect a voltage source providing the constant supply voltage to the inductive storage element. These switching processes may cause electromagnetic interferences (EMI). This is, in particular, an issue when there is a long supply line between the voltage source and a controller including the inductive storage element, like in automotive applications in which the voltage source is, for example, a battery and in which controllers can be distributed throughout the car with supply lines of several meters between the controllers and the battery.
There is, therefore, a need to provide a controlled current source in which EMI problems can be prevented or at least reduced.