Switching power supply

A switching power supply for supplying an output voltage controlled to a desired value, comprising:

• a supply path including a switching controller, a driver configured to control the switching controller, a galvanically-isolating transformer connected after the switching controller, and, connected after the transformer, a rectifier-containing output circuit having an output to which a consumer is connectable;
• and
• a feedback path including a light source and a light receiver, wherein the light source and the light receiver are configured to feed to the driver a signal corresponding to the output voltage,
• wherein the driver is further configured to control the output voltage to the desired value via a corresponding operation of the switching controller,
• wherein the feedback path further includes a synchronous buck regulator configured to regulate a supply voltage across the light source to a fixed value below the desired value and further includes an electrical current regulator configured to regulate an electrical current flowing through the light source to an electrical current value corresponding to the output voltage and
• wherein the voltage regulator is embodied as a component of a circuit that includes an input circuit connected in front of the voltage regulator, an output circuit connected after the voltage regulator, an energy storer including a buffer capacitor connected after the voltage regulator, a fuse or a circuit breaker connected in front of the voltage regulator, a fuse or a circuit breaker connected after the voltage regulator, and/or a voltage limiter connected after the voltage regulator, wherein the voltage limiter includes diodes connected so as to oppose one another.