Abstract: A conductive transistor switch has a collector that applies a reset pulse to an electronic circuit. A pull-up resistor is coupled between the collector of the transistor switch and a power supply voltage developed in a filter capacitor that energizes the electronic circuit. Proper reset operation requires the output supply voltage not to exceed, for example, 0.2 volts, during at least a portion of the reset operation. The user initiates the reset pulse that momentarily disables a power supply for ceasing the generation of the output supply voltage when the reset operation is performed. The value of the resistor is selected to be sufficiently low such that when the transistor switch is conductive, the discharge of the filter capacitor via the pull-up resistor is speeded up for completing the discharge of the filter capacitor in no more than, for example, 2 seconds to provide a maximum level of the output supply voltage that is no more than 5% of its normal operation voltage level.

Abstract: A power supply receives an alternating current input that is rectified by a rectifier. The rectified output voltage is coupled to a load and a microprocessor during both a run mode operation and a standby mode operation. The rectifier provides synchronous rectification by an included MOSFET, during the run mode operation and non-synchronous rectification during the standby mode operation by an included Schottky diode. The Schottky diode in rectifier is in parallel with the MOSFET and provides rectification during the standby mode operation. A source of an on/off control signal from the microprocessor is applied to the load for changing the operation mode and applied, in parallel, to the rectifier for disabling the synchronous rectification in the rectifier, during the standby mode operation. The efficiency of the power supply is improved in the standby mode operation by elimination of the power consumed to energize a synchronous rectifier controller.

Abstract: In a switched mode power supply, and in accordance with a method for operating a switched mode power supply, the magnitude of each occurrence of a current flowing during operation of a power output switch is sensed for negative feedback control. A sense voltage is generated proportional to the primary supply voltage. Whenever the sense voltage exceeds a threshold, output power of the power supply is limited by increasing the sensed magnitude of each occurrence of the flowing currents by adding to each sensed magnitude a voltage proportional to the sense voltage. Threshold voltages can be selected by using Zener diodes having different breakdown voltages. Respective ranges within the overall range of the primary supply voltage in which supplemental power limiting occurs and does not occur can thus be controlled.

Abstract: The disclosed embodiments relate to apparatus and method for reducing power losses in a power supply. There is provided an apparatus comprising means for coupling a first signal (S2) to a reference level (ground) when the coupling means is conductive, means for placing the coupling means in a conductive state during a duration of a portion of a period of a second signal (S3), and means for altering the duration of conduction of the coupling means in response to an amplitude of the second signal.

Abstract: A conductive transistor switch has a collector that applies a reset pulse to an electronic circuit. A pull-up resistor is coupled between the collector of the transistor switch and a power supply voltage developed in a filter capacitor that energizes the electronic circuit. Proper reset operation requires the output supply voltage not to exceed, for example, 0.2 volts, during at least a portion of the reset operation. The user initiates the reset pulse that momentarily disables a power supply for ceasing the generation of the output supply voltage when the reset operation is performed. The value of the resistor is selected to be sufficiently low such that when the transistor switch is conductive, the discharge of the filter capacitor via the pull-up resistor is speeded up for completing the discharge of the filter capacitor in no more than, for example, 2 seconds to provide a maximum level of the output supply voltage that is no more than 5% of its normal operation voltage level.

Abstract: The disclosed embodiments relate to apparatus and method for reducing power losses in a power supply. There is provided an apparatus comprising means (214) for coupling a first signal (S2) to a reference level (ground) when the coupling means is conductive, means (202, 204) for placing the coupling means in a conductive state during a duration of a portion of a period of a second signal (S3), and means (206) for altering the duration of conduction of the coupling means in response to an amplitude of the second signal.

Abstract: In a switched mode power supply, and in accordance with a method for operating a switched mode power supply, the magnitude of each occurrence of a current flowing during operation of a power output switch is sensed for negative feedback control. A sense voltage is generated proportional to the primary supply voltage. Whenever the sense voltage exceeds a threshold, output power of the power supply is limited by increasing the sensed magnitude of each occurrence of the flowing currents by adding to each sensed magnitude a voltage proportional to the sense voltage. Threshold voltages can be selected by using Zener diodes having different breakdown voltages. Respective ranges within the overall range of the primary supply voltage in which supplemental power limiting occurs and does not occur can thus be controlled.

Abstract: When a main switching transistor of a zero voltage switching power supply is conductive, a voltage is developed in a current sensing resistor coupled in series with the transistor. The voltage in the current sensing resistor is coupled to a control terminal of a comparator transistor. During a given conduction interval of the main switching transistor, the comparator transistor is turned on when the current sensing resistor voltage is sufficiently large to turn on the comparator transistor. An output of the comparator transistor is coupled to the control terminal of the main switching transistor for controlling the turn off instant of the main switching transistor on a current pulse-by-current pulse basis. A resonant voltage pulse developed at a main current conducting terminal of the main switching transistor is capacitively coupled to the control terminal of the comparator transistor for maintaining the comparator transistor turned on, during a transition interval of the resonant voltage pulse.

Abstract: A transformer includes a bobbin with spacers extending inwardly from the bobbin and a barrier extending outwardly from the bobbin. A ferrite core positioned within the bobbin is separated by the spacers to provide a controlled air gap. Primary windings wound around the bobbin are separated into series connected windings by the barrier. The barrier is aligned with spacers so as to prevent any wound portion of the primary windings from overlapping the air gap in the ferrite core.

Abstract: When a main switching transistor of a zero voltage switching power supply is conductive, a voltage is developed in a current sensing resistor coupled in series with the transistor. The voltage in the current sensing resistor is coupled to a first input of a comparator of the control circuit. A second input of the comparator is coupled to a capacitor that develops a voltage that varies in accordance with an output voltage of the power supply. During a given conduction interval of the transistor, the comparator is triggered in accordance with the difference between the current sensing resistor voltage and the capacitor voltage. An output of the comparator is coupled to the base of the transistor for controlling the turn off instant of the transistor on a current pulse-by-current pulse basis. Under overload condition, when the transistor is turned off, a reverse collector current flows through the base-collector junction of the transistor.

Abstract: In a tuned switch mode power supply, a supply inductance is coupled to a capacitance to form a tuned, resonant circuit. A transistor switch is coupled to the resonant circuit for generating current pulses in the inductance, coupled to a load circuit to provide an output of the power supply. Resonant voltage pulses are developed between a pair of main current conducting terminals of the transistor switch. A controller is coupled to the transistor switch for generating a switch control signal, during a run mode of operation. The transistor switch is turned on periodically, when the resonant voltage pulses reaches a zero voltage, to provide for zero voltage switching. The generation of the current pulses is disabled to provide for a burst mode operation, in a standby mode operation.

Abstract: A forward converter includes a chopper transformer having a primary winding and one or more secondary windings. A corresponding rectifier and a corresponding filter capacitor is coupled to each secondary winding. An inductor is coupled in series with the primary winding. A low impedance current path that includes the corresponding rectifier is formed between each secondary winding and the corresponding filter capacitor. The inductor limits the rate of change of the current in each current path.

Abstract: In a tuned switch mode power supply a zero voltage is maintained across a transistor switch, during both turn off and turn on switching transition intervals in the transistor switch. The tuned switch mode power supply operates in a current-mode control, on a current pulse-by-current pulse control basis. A modulator of the power supply includes a pair of transistors that form a regenerative switch to produce a portion of a control signal of the transistor switch that causes the transistor switch to turn off. A transformer-coupled input supply voltage maintains the transistor switch conductive as long as the current in the transistor switch does not exceed the threshold level of a regenerative switch. A resonant pulse is transformer-coupled from the resonant circuit to the regenerative switch for turning off the regenerative switch and for maintaining the transistor switch non conductive after the regenerative switch is turned off.

Abstract: In a tuned switch mode power supply a zero voltage is maintained across a transistor switch, during both turn off and turn of switching transition intervals in the transistor switch. The tuned switch mode power supply operates in a current-mode control, on a current pulse-by-current pulse control basis. An over-current protection circuit disables the transistor switch when an over-current condition persist longer than a first interval that is substantially longer than a period of a given current pulse in the transistor switch. The operation of the transistor switch is undisturbed, when the over-current condition lasts only a shorter interval than the first interval.

Abstract: In a tuned switch mode power supply a zero voltage is maintained across a transistor switch, during both turn off and turn on switching transition intervals in the transistor switch. The tuned switch mode power supply operates in a current-mode control, on a current pulse-by-current pulse control basis. An over-current protection circuit disables the transistor switch when an over-current condition persists longer than a first interval that is substantially longer than a period of a given current pulse in the transistor switch. The operation of the transistor switch is undisturbed, when the over-current condition lasts only a shorter interval than the first interval.

Abstract: A forward converter includes a chopper transformer having a primary winding and one or more secondary windings. A corresponding rectifier and a corresponding filter capacitor is coupled to each secondary winding. An inductor is coupled in series with the primary winding. A low impedance current path that includes the corresponding rectifier is formed between each secondary winding and the corresponding filter capacitor. The inductor limits the rate of change of the current in each current path.