Abstract: An electric lamp (1) comprising a socket (2), a lamp bulb (4) mounted on the socket, in which bulb at least one semiconductor light source (5) is arranged. Cooling means (6) comprise at least two facing cooling fins (7,8) which are separated by at least one spacing (9). Said spacing being open to the environment and extending from the heart of the lamp bulb to the outer surface of the bulb. The lamp comprises a light redistributing, light transmittable wall (13) for redistributing light; optionally said light redistributing wall comprises separate, discernable wall parts (14,15). For example, each discernable bulb part is shaped like a surface of a half prolate or half oblate ellipse. Thus, a desired double beam or homogeneous, omni-directional light distribution is obtainable.

Abstract: An electric lamp (1) comprising a socket (2), a lamp bulb (4) mounted on the socket, in which bulb at least one semiconductor light source (5) is arranged. Cooling means (6) comprise at least two facing cooling fms (7,8) which are separated by at least one spacing (9). Said spacing being open to the environment and extending from the heart of the lamp bulb to the outer surface of the bulb. The lamp comprises a light redistributing, light transmittable wall (13) for redistributing light; optionally said light re-distributing wall comprises separate, discernable wall parts (14,15). For example, each discernable bulb part is shaped like a surface of a half prolate or half oblate ellipse. Thus, a desired double beam or homogeneous, omni-directional light distribution is obtainable.

Abstract: A ballast circuit for a compact fluorescent lamp includes a down-converter for operating the lamp with a DC current during stationary operation. The ballast circuit is equipped with an additional inductor. The choke of the down-converter and the additional inductor jointly ignite the lamp. During stationary operation, the additional inductor conveys no current.

Abstract: A ballast circuit for a compact fluorescent lamp includes a down-converter for operating the lamp with a DC current during stationary operation. First and second input terminals provide a DC supply voltage and first and second output terminals connect to the lamp. The down-converter has a first switch and a diode serially connected to the input terminals and an inductor coupled to the first switch and to one output terminal. A second switch is coupled to the output terminal. A control circuit operates the first switch at a high frequency. During the preheating and ignition phase, the down-converter is operated in the continuous mode and during stationary operation in the discontinuous mode by control of the switching frequency of the first switch.

Abstract: A ballast for a compact fluorescent lamp includes a down-converter for operating the lamp with a DC current during stable operation and a charge pump for igniting the lamp. The converter includes an inductor and a first series circuit of a first diodie and a first switching element. An output capacitor shunts the lap terminals. The charge pump includes a second series circuit of second diodie and a second switching element coupled to the lamp terminals with the second diode polarized to prevent the discharge of the output capacitor when the second switching element is conductive. The inductor cooperates with the first and second diodes and the second switching element to build up the voltage across the outpout capacitor to the ignition voltage level of the lamp.

Abstract: An integrated circuit (1) includes a voltage-sensing circuit (2) and a current mirror (3) for sensing both a voltage (Vi) and a current (Ii) at one input terminal (T) of the integrated circuit. The voltage-sensing circuit (2) has an input which is connected to the input terminal (T) and an output which supplies a voltage level indication (Vu). The current mirror (3) has an input which is also connected to the input terminal (T), a reference terminal which is connected to a reference potential, and an output which supplies an output current (Iu). The input of the current mirror has a high impedance as long as the voltage level (Vi) is below a threshold voltage (Vth) of the current mirror (3). Within a voltage range determined by this threshold voltage (Vth), the voltage level indication (Vu) is a measure of the voltage level (Vi). The current mirror (3) becomes active and the output current (Iu) is a mirrored input current (Ii) if the voltage level (Vi) exceeds the threshold voltage (Vth).

Abstract: The power supply apparatus serves to convert an electric direct voltage, acting as an input voltage, into an output voltage and comprises positive and negative input terminals (1, 3) which are arranged to receive the input voltage.

Abstract: In a standby mode, a switched-mode power supply circuit may be operated in a burst mode with reduced secondary voltages (Vo1, Vo2) for supplying a standby voltage (Vo1) at a very high efficiency. In a normal operating mode of the power supply, a control circuit (1) is maintained in its on-state by a power supply voltage (Vcc) generated by the power supply. The control circuit (1) supplies control pulses (Vd) for switching the power supply. The burst mode is obtained by decreasing the power supply voltage (Vcc) generated for the control circuit (1) to such an extent that, without any further provisions, the control circuit (1) reaches an off-state in which no control pulses (Vd) are generated. In the standby mode, the control circuit (1) is supplied with current by a power supply circuit (4).

Abstract: A power supply circuit for generating a stabilized power supply generally comprises a series arrangement of a primary winding of a transformer and a switch. The switch is controlled by a control circuit, an input of which receives a signal related to the output voltage of the power supply circuit. The control circuit determines the duty cycle of the switch. Dependent on the power consumption of the lead connected to the output of the power supply circuit, the duty cycle is either increased or decreased. The duty cycle has a given minimum value which is caused by the inertia of the switch upon switching on and switching off. The minimum duty cycle may be reached, inter alia, when the power supply circuit works in an apparatus using a standby mode.

Abstract: Switched-mode power supplies in which a series arrangement of a bipolar transistor and a MOS field effect transistor is used are known and referred to as cascode circuits. In these circuits the bipolar transistor is switched (with the MOS field effect transistor) via the emitter instead of with the base. Since the collector current of the bipolar transistor may vary over a large range, the base should be proportionally driven to prevent the bipolar transistor from getting either above or below its normal operating range. By making use of an extra winding on a transformer arranged in series with the cascode circuit, a non-dissipative proportional drive of the base of the bipolar transistor is obtained. The extra winding is coupled to the base via an inductance.

Abstract: In switched-mode power supply circuits the switch is rendered conducting for a longer period (or more frequently), dependent on the load connected to the power supply circuit, so as to ensure that the transformer can transfer enough energy to the secondary side for charging the output capacitor to a sufficient extent. To ensure that the transformer can always supply all energy stored in the transformer to the secondary side, a demagnetizing detection circuit detects the demagnetization of the transformer. If the load decreases (for example, in standby operation) the on-time of the switch is reduced. However, this on-time may achieve a minimum value so that the power supply circuit no longer functions properly. To obtain an efficiently operating power supply circuit, both in normal operation and in a low-load state, the control circuit of the power supply circuit has at least two modes, i.e.

Abstract: A switched mode power supply circuit includes a controllable switch for controlling the current in the supply transformer of the power supply circuit. During normal operation of the power supply, its DC output voltage is maintained at a substantially constant, first value in spite of variations of the DC input voltage and of the load on the output voltage by controlling the duration of the conductivity time of the switch. A function generator supplies a signal, which is a given function of the output voltage, to a control input of a pulse duration modulator for determining the duration of the conductivity time. At an output voltage which is considerably lower than the first value, the signal of a starting circuit is passed on by a selection circuit to the said control input in order to increase the conductivity time of the switch. This signal corresponds to a shorter switch conductivity time than does the signal of the function generator.

Abstract: A switched mode power supply circuit includes a controllable switch in series with an inductive element between the terminals of a DC input voltage. A control circuit renders the switch alternately conductive and non-conductive. A rectifier for deriving a DC output voltage is coupled to the inductive element. To prevent the inductive element from becoming saturated, a switching element is coupled to the control circuit for maintaining the controllable switch in its blocked state only during a time interval which immediately follows an interval of conductance of the controllable switch and during which the voltage across the inductive element has the same polarity as when the rectifier is conductive.

Abstract: A switched-mode power supply circuit having a transformer and a first controllable switch on the primary side of the transformer. A first section is in the form of a flyback d.c. converter including a first secondary winding of the transformer for generating a first d.c. output voltage which is stabilized, by a control, against d.c. input voltage variations of the circuit and of a first load. A second section including a second secondary winding of the transformer constitutes a forward d.c. converter having a second controllable switch for generating a second d.c. output voltage. The ratio between the period of conductance of the second switch and the period of the control signal of the first switch is independent of the frequency of this signal.

Abstract: A switched-mode power supply circuit for converting a DC input voltage into a DC output voltage comprises a series arrangement of a controllable power switch and an inductive element coupled between the input voltage terminals. Control means are provided for rendering the power switch alternately conducting and non-conducting and a rectifier is coupled to the inductive element for making the output voltage available. The inductive element and a capacitor coupled thereto form a part of a resonant circuit in which a voltage oscillation is present in the time periods when the switch and the rectifier are currentless. The circuit further comprises means for interrupting the oscillation present in the resonant circuit at an instant when the voltage across the inductive element or the current through the capacitor is substantially zero. In one embodiment, the dissipation in the circuit is reduced and the circuit is synchronized.

Abstract: A switched-mode power supply circuit with having an operating state and a stand-by state in which the value of a first output voltage is considerably lower than in the operating state, whereas the value of a second output voltage is substantially the same. With the aid of a duration-determining circuit (Tr7, Tr8, R17, C12) which is controlled by a switch (Tr6) operative during the stand-by state, a low-frequency burst mode is maintained during this state in which the switch of the supply circuit conducts a number of consecutive times and subsequently becomes non-conductive during a given period. As a result the dissipation in the circuit is reduced.

Abstract: A switched-mode power supply circuit having an operating state and a stand-by state in which the value of a first output voltage is considerably lower than in the operating state, whereas the value of a second output voltage is substantially the same. With the aid of a duration-determining circuit (Tr7, Tr8, R17, C12) which is controlled by a switch (Tr6) operative during the stand-by state, a low-frequency burst mode is maintained during this state in which the switch of the supply circuit conducts a number of consecutive times and subsequently becomes non-conductive during a given period. As a result the dissipation in the circuit is reduced.

Abstract: A switched-mode self-oscillating supply voltage circuit for converting an input voltage into an output d.c. voltage which is substantially independent of variations of the input voltage and/or a load connected to the output voltage. The circuit comprises a first controllable switch connected in series with a transformer winding and a second controllable switch for turning-off the first switch. The conduction period of the first switch is controlled by means of a control voltage present on a control electrode of the second switch. The circuit can be switched-over to a stand-up state in which the energy supplied to the load is reduced to zero. A starting network is connected between the input voltage and the second switch so that the current therein flows through the second switch during the period of time this switch conducts and does not flow to the control electode of the first switch in the stand-by state.