Two-stage operating device with an isolatable clocked converter as a power factor corrector and control method for the operating device

A control method for a circuit arrangement, the circuit arrangement comprising:

• an input for inputting a mains power,
• an output with a positive output connection and a negative output connection for operating a load with an output current and an associated output voltage,
• a first clocked converter with a SELV barrier between its primary side and its secondary side for generating a converter output current to generate an intermediate circuit voltage with a ripple on the secondary side and for controlling it to an adjustable mean value of the intermediate circuit voltage,
• wherein the circuit arrangement is designed to control the first clocked converter such that the mean value of the intermediate circuit voltage is configured to follow the output voltage with a distance corresponding to the headroom voltage,
• a post-regulator connected downstream of the first clocked converter for regulating the ripple on the intermediate circuit voltage generated by the first clocked converter,
• a first optocoupler for transmitting information from the primary side to the secondary side via a current setpoint of the output current,
• a second optocoupler for transmitting information via a headroom voltage from the secondary side to the primary side to enable control of the intermediate circuit voltage by the first clocked converter, the headroom voltage corresponding to a potential difference between the negative output connection and a circuit ground,
• exactly one control circuit on the primary side for controlling the circuit arrangement,
• wherein the control circuit is designed for controlling the headroom voltage to a smallest possible value in order to set a power loss in the circuit arrangement and in the post-regulator to a minimum value and at a same time configured to maintain a ripple of the output current as low as possible,
• wherein the method comprises:
• receiving a signal from the control circuit,
• controlling the first clocked converter to an intermediate circuit voltage according to a value of the signal,
• transmitting the setpoint of the output current via the first optocoupler to the post-regulator,
• regulating the ripple of the intermediate circuit voltage and controlling the output current of the circuit arrangement by the post-regulator,
• transmitting the signal from the detection circuit-to the control circuit.