Self-oscillating switch circuit for use in a switching DC-DC converter, the self-oscillating switch circuit comprising: - a first input terminal and a second input terminal for receiving power from a power supply; - a first output terminal (Tout1) and a second output terminal (Tout2) for supplying power to a load; - a power switch semi-conductor device having a base terminal, the power switch semi-conductor device being configured for controlling a load current between the first input terminal and the first output terminal (Tout1), wherein a collector of the power switch semi-conductor device is connected to the first output terminal (Tout1) and an emitter of the power switch semi-conductor device is coupled via a sensing resistor to the first input terminal; - a first control semi-conductor device coupled to the power switch semi-conductor device for supplying a control signal to the base terminal of the power switch semi-conductor device for controlling switching of the power switch semi-conductor device, wherein the base terminal of the power switch semi-conductor device is coupled to a collector of the first control semi-conductor device, an emitter of the first control semi-conductor device is coupled to the first input terminal, and the base terminal of the first control semi-conductor device is coupled to the emitter of the power switch semi-conductor device; - a second control semi-conductor device, wherein a collector of the second control semi-conductor device is coupled to the base terminal of the power switch semi-conductor device and the collector of the first control semi-conductor device, an emitter of the second control semi-conductor device is coupled via a current-limiting resistor to the second input terminal and the second output terminal (Tout2), and a base terminal of the second control semi-conductor device is coupled to the first input terminal and connected, to the collector of the power switch semi-conductor device and to the first output terminal (Tout1); characterized by - a gain semi-conductor device coupled between the power switch semi-conductor device and the first control semi-conductor device for amplifying the control signal applied by the first control semi-conductor device to the power switch semi-conductor device, wherein the gain semi-conductor device is with its collector connected to the base terminal of the first control semi-conductor device, with its base terminal connected to the collector of the first control semi-conductor device and with its emitter connected to the base terminal of the power switch semi-conductor device. - a first input terminal and a second input terminal for receiving power from a power supply; - a first output terminal (Tout1) and a second output terminal (Tout2) for supplying power to a load; - a power switch semi-conductor device having a base terminal, the power switch semi-conductor device being configured for controlling a load current between the first input terminal and the first output terminal (Tout1), wherein a collector of the power switch semi-conductor device is connected to the first output terminal (Tout1) and an emitter of the power switch semi-conductor device is coupled via a sensing resistor to the first input terminal; - a first control semi-conductor device coupled to the power switch semi-conductor device for supplying a control signal to the base terminal of the power switch semi-conductor device for controlling switching of the power switch semi-conductor device, wherein the base terminal of the power switch semi-conductor device is coupled to a collector of the first control semi-conductor device, an emitter of the first control semi-conductor device is coupled to the first input terminal, and the base terminal of the first control semi-conductor device is coupled to the emitter of the power switch semi-conductor device; - a second control semi-conductor device, wherein a collector of the second control semi-conductor device is coupled to the base terminal of the power switch semi-conductor device and the collector of the first control semi-conductor device, an emitter of the second control semi-conductor device is coupled via a current-limiting resistor to the second input terminal and the second output terminal (Tout2), and a base terminal of the second control semi-conductor device is coupled to the first input terminal and connected, to the collector of the power switch semi-conductor device and to the first output terminal (Tout1); - a gain semi-conductor device coupled between the power switch semi-conductor device and the first control semi-conductor device for amplifying the control signal applied by the first control semi-conductor device to the power switch semi-conductor device, wherein the gain semi-conductor device is with its collector connected to the base terminal of the first control semi-conductor device, with its base terminal connected to the collector of the first control semi-conductor device and with its emitter connected to the base terminal of the power switch semi-conductor device.