Abstract: A medical device with a power supply for connecting to an AC power grid in the range of >50 VAC to 264 VAC (wide range) features a circuit for only connecting at least one discharge resistor in parallel to at least one smoothing capacitor if no AC input voltage is present at the power supply. The power supply features a rectifier and at least one smoothing capacitor for smoothing a direct voltage to be supplied by the power supply, as well as at least one discharge resistor for discharging the smoothing capacitor. The power supply features a circuit electrically connected to the discharge resistor and the smoothing capacitor, designed to detect a switched-on state of the medical device with an AC input voltage present at its power supply, and to only connect the discharge resistor in parallel to the smoothing capacitor if the circuit does not detect a switched-on state.

Abstract: An electrosurgical generator for an electrosurgical instrument includes a DC voltage supply and a high-voltage inverter that generates a high-frequency AC voltage having a variable voltage and frequency that is output at an output for the connection of the electrosurgical instrument. The inverter is configured as a multilevel inverter and includes a plurality of inverter cells connected in a cascaded manner that are driven by a control device. Thanks to the cascading, switching losses incurred in the power semiconductors are reduced, both in terms of value (through the divided and thus lower voltage) and in terms of frequency (through the reduced switching frequency).

Abstract: An electrosurgical generator includes a power supply unit which, when operating, supplies a direct voltage circuit, and a high-voltage inverter supplied from it that generates a high-frequency alternating voltage that is applied to outputs for connection of the electrosurgical instrument. The inverter includes a clock-driven power switch and a zero-crossing detector that recognizes zero crossings of the oscillation generated by the inverter. A signal for the generated alternating voltage is applied to the zero-crossing detector via a voltage divider which is a capacitive voltage divider with at least one capacitor that is resistant to high voltage. Undesirable direct voltage components at the center tap in the presence of changes to the supply voltage can be avoided thereby, since charge reversals as a result of changes to the supply voltage occur on both sides, and their effects thus cancel out.

Abstract: A medical device with a power supply for connecting to an AC power grid in the range of >50 VAC to 264 VAC (wide range) features a circuit for only connecting at least one discharge resistor in parallel to at least one smoothing capacitor if no AC input voltage is present at the power supply. The power supply features a rectifier and at least one smoothing capacitor for smoothing a direct voltage to be supplied by the power supply, as well as at least one discharge resistor for discharging the smoothing capacitor. The power supply features a circuit electrically connected to the discharge resistor and the smoothing capacitor, designed to detect a switched-on state of the medical device with an AC input voltage present at its power supply, and to only connect the discharge resistor in parallel to the smoothing capacitor if the circuit does not detect a switched-on state.

Abstract: A high frequency current application apparatus for thermal sclerosing of body tissue, comprising a high frequency generator connected to at least two electrodes, one of which is to be introduced into body tissue. The apparatus includes a measuring and calculating device adapted to ascertain impedance (or ohmic resistance) between the two electrodes between which a respective therapeutic high frequency current flows. A control device is connected to the measuring and calculating device for varying the output power. During high frequency current application the measuring and calculating device forms the first derivative with respect of time of the impedance. The control device reduces output power when that derivative exceeds a positive threshold characteristic of a threat of tissue desiccation and restores output power to the original power when the first derivative exceeds in positive values a negative threshold characteristic of adequate rehydration of body tissue.

Abstract: An electrode array is used for the thermal schlerosing of body tissue. The electrode array has at least three active electrodes that, during use, are placed in electrical-conducting connection with body tissue. A high frequency generator is electrically connected for selective application of current to the active electrodes for producing a high frequency voltage. A measuring device measures impedance of the tissue between the active electrodes. In addition, a selector device selects a sub-array including at least two active electrodes from the electrode array, the selecting being effected on the basis of the measured impedance. Further, a control device is configured such that a high frequency voltage is respectively applied between the active electrodes of the selected sub-array in such a way that a high frequency current flows between the selected active electrodes through the body tissue.