Electronic ballast for e.g. coldstarting discharge lamp, has varistor, shutdown device, diode, resistors and integration capacitor connected in parallel for limiting voltage across intermediate circuit capacitor

摘要

The ballast has an intermediate circuit capacitor (C6) for supplying a DC voltage to switching units (V1, V2). A pump switch diode, capacitors and a lamp inductor charge the capacitor. A varistor (R8), a measuring resistor (R3), a shutdown device (SD), a diode (D5), integration and discharge resistors (R4, R5) and an integration capacitor (C3) are connected in parallel with the capacitor (C6) for limiting voltage across the capacitor (C6). The varistor converts electrical energy into thermal energy when a maximum value for the voltage across the capacitor is exceeded. An independent claim is also included for a method for operating an electronic ballast for a discharge lamp.