PWM controlled power source and method

A method of operating a PWM controlled current source comprising a selection input, a modulation input, a switchable current source, an inverter circuit, and a voltage-to-current converter, the inverter circuit being connected on an output side to a control input of the switchable current source, the inverter circuit comprising a first inverter and a second inverter, with an input of the first inverter being connected to the input node and to an output of the second inverter, and a capacitance conditioned by elements of the circuit, the method comprising the steps of:

• providing a pulsed signal with a first pulse duration;
• providing a modulation signal;
• generating a signal derived from the pulsed signal, which activates the switchable current source through the inverter circuit, wherein the signal is supplied to the input node based on the pulsed signal, and the signal controls the switchable current source via the inverter circuit;
• latching the modulation signal during the first pulse duration or a part of it;
• generating a current signal depending on the buffered modulation signal;
• supplying the current signal to the inverter circuit so that the inverter circuit deactivates the current source after a second pulse duration.

A PWM controlled current source, comprising:

• a selection input;
• a modulation input;
• a switchable current source which can be switched by means of a signal at a control terminal and whose current output is configured for connection to a load;
• an inverter circuit comprising:
• an input node;
• and
• an output coupled to the control terminal, the inverter circuit having a capacitance conditioned by elements of the inverter circuit;
• and
• a voltage-to-current converter that generates a current derived from a modulation signal at the modulation input and supplies the current to the input node, and the supplied current disconnects the switchable current source after a time period predetermined by the conditioned capacitance,
• wherein
• a start signal is supplied to the input node based on a selection signal at the selection input, which controls the switchable current source via the inverter circuit, and
• the voltage-to-current converter is activatable in dependence on the selection signal at the selection input.