Abstract: A retrofit lamp includes at least one series circuit having a multiplicity of LEDs having a circuit arrangement. The at least one series circuit including is coupled between a first rectifier output connection and a second rectifier output connection. A breakdown apparatus is coupled between a third connection terminal and a fourth connection terminal. The breakdown apparatus may have the following properties: up to a first threshold value of the voltage drop across said breakdown apparatus during operation, the breakdown apparatus is nonconducting. If the first threshold value is exceeded, the breakdown apparatus becomes conducting. The breakdown apparatus remains conducting as long as current is supplied to it which is above a second threshold value. As soon as the current falls below the second threshold value, the breakdown apparatus becomes nonconducting again. In the conducting state, the breakdown apparatus has a forward voltage which is below a third threshold value.

Abstract: A retrofit lamp includes at least one series circuit having a multiplicity of LEDs having a circuit arrangement. The at least one series circuit including is coupled between a first rectifier output connection and a second rectifier output connection. A breakdown apparatus is coupled between a third connection terminal and a fourth connection terminal The breakdown apparatus may have the following properties: up to a first threshold value of the voltage drop across said breakdown apparatus during operation, the breakdown apparatus is nonconducting. If the first threshold value is exceeded, the breakdown apparatus becomes conducting. The breakdown apparatus remains conducting as long as current is supplied to it which is above a second threshold value. As soon as the current falls below the second threshold value, the breakdown apparatus becomes nonconducting again. In the conducting state, the breakdown apparatus has a forward voltage which is below a third threshold value.

Abstract: In an operating circuit for a low-pressure discharge lamp, the lamp current is controlled depending on the lamp temperature or the luminous flux.

Abstract: A circuit arrangement for operating a load, in which in normal operation control energy for activating the switching element or switching elements (T.sub.a, T.sub.b) is obtained from the energy content of the freewheeling current anti-parallel relative to this switching element, and the ON duration is determined by the time constants of control energy storage elements which are assigned to the switching elements, or by the storage time of bipolar transistors.

Abstract: The invention relates to a circuit arrangement for operating a lamp (EL), particular a low-pressure discharge lamp, with a load circuit which has at least one inductor (L2) and at least one capacitor (C7, C8, C9), and with an invertor which may be configured as a half-bridge arrangement with two switching elements (T1, T2), and with a drive circuit (AS) for driving the switching elements (T1, T2). The invention provides that the drive circuit (AS) has at least one LC parallel tuned circuit (L3C3, L4C4). The circuit arrangement according to the invention can be produced without separate cost-intensive wound parts.

Abstract: To eliminate the necessity for a saturated or air gap inductance to provide feedback circuit for a self-exciting oscillator including two active electronic switches (T1, T2) , for example MOSFETs, an auxiliary winding (HW1, HW2, . . . HW11) is inductively coupled to the resonance inductance (L2) present in the circuit for the discharge lamp (LP) anyway; and a pulse shaping - phase shifting network (R3, C3; R4, C4 . . . ) , devoid of inherent resonance, coupling the auxiliary winding to the active switching elements. The pulse shaping - phase shifting network is formed of a one or multiple-stage RC low-pass circuit, connected serially between the auxiliary winding and the control input, for example the gate, of the active switching element. The RC network can be constructed with variable elements, for example including PTC resistors, a varistor or the like, and may include a current source, protective circuits to protect against voltage peaks including Zener diodes.