Abstract: A DC power source device comprises a MOS-FET 5 which performs the intermittent switching operation for converting DC input from a DC power supply 1 into high frequency electric power; a control circuit 9 for turning MOS-FET 5 on and off; and a rectifying smoother 6 for converting the high frequency electric power through MOS-FET 5 into a DC power output supplied to a load 50. Control circuit 9 comprises an output current controller 11 for controlling the on-off term of MOS-FET 5 to make DC output current IO through load 50 settle toward a rated value IOMAX; a shunt regulator 24 for receiving a drive current ISH supplied from rectifying smoother 6 and producing a reference voltage VR1 to regulate the rated value IOMAX of output current controller 11; and a constant current source 32 for keeping drive current ISH on a substantially constant level under the rated output current value condition and reduced output voltage condition.

Abstract: An inventive inverter has a semiconductor switch circuit connected to the primary winding of a transformer. The semiconductor switch circuit is respectively controlled by PWM to supply a constant current to the load. connected to a secondary winding of the transformer. The inverter is capable of deliberately regulating its ac power output to the load and lowering the lower limit of the output power through control of the intermittent operation, in which an error signal for carrying out the PWM control is reduced to zero during each off-duty period. In addition, the error signal for the PWM control is slowly decreased or increased in each shift from an off-duty period to on-duty period, and vise versa, by charging or discharging the capacitor in a feedback circuit, thereby allowing slow start or slow end of the respective on-off operations for the constant current control through the PWM.

Abstract: Disclosed herein is a flyback converter with a synchronous rectifier which is applied to a power supply of a portable computer such as a notebook PC. The flyback converter is operated in a critical conduction mode to turn on/off a main switch at a zero crossing point of an output voltage. The flyback converter is also adapted to supply a driving voltage to a synchronous switch using the output voltage. Therefore, there is no need for a secondary auxiliary coil of a transformer and for a Schottky diode to be connected in parallel with the synchronous switch, resulting in simplification in circuit design.

Abstract: A power supply with high pulse width modulation gain and low noise sensitivity has been disclosed. In one example, a control current is received at a control terminal of a regulator circuit. The control current includes a consumption current of the regulator circuit and a feedback current. A duty cycle at which a power switch is switched is adjusted in response to the feedback current. The consumption current of the regulator circuit is increased during an on-time of the power switch in response to the duty cycle at which the power switch is switched.

Abstract: A high voltage power supply (HVPS) including an oscillation circuit for generating and outputting an alternating current (AC) voltage using an oscillation of a transformer, and a voltage multiplying circuit for increasing the AC voltage from the oscillation circuit using a plurality of voltage doublers, and outputting the increased AC voltage. The power supply further includes a controller for controlling the oscillation circuit.

Abstract: Overload protecting operation is performed by controlling the current peak value of a switching device 1 through the use of a comparator 8, a NAND circuit 5, and so on according to variations in feedback current being input to a feedback signal control circuit 11, internally setting the overcurrent protection of switching device 1 through the use of a clamp circuit 12, charging a capacitor 34 when having fallen below a specified current smaller than current required for the overcurrent protection for a fixed time period, and detecting rise in voltage VOL at the capacitor 34 to a constant voltage to stop switching operation. By achieving the overload protection under normal load and the overcurrent protection against peak load in a single switching power supply unit, problems such as the complexity of the unit and an increase in the element count of the control circuit are solved.

Abstract: An inventive inverter has a semiconductor switch circuit connected to the primary winding of a transformer. The semiconductor switch circuit is respectively controlled by PWM to supply a constant current to the load connected to a secondary winding of the transformer. The inverter is capable of deliberately regulating its ac power output to the load and lowering the lower limit of the output power through control of the intermittent operation, in which an error signal for carrying out the PWM control is reduced to zero during each off-duty period. In addition, the error signal for the PWM control is slowly decreased or increased in each shift from an off-duty period to on-duty period, and vise versa, by charging or discharging the capacitor in a feedback circuit, thereby allowing slow start or slow end of the respective on-off operations for the constant current control through the PWM.

Abstract: A switching power supply including an oscillator frequency tuner to enhance its load driving capability is presented. The oscillator frequency tuner includes a plurality of capacitors connected between a reference voltage output of the switching control circuit and a ground terminal, at least one bypass switch coupled across at least one of the capacitors for controlling the charging and discharging operation of the capacitor coupled therewith, and a bypass switch controller for controlling a switching state of the bypass switch. When the switching power supply is operating under a peak load condition, the bypass switch controller receives a feedback control signal and instructs the bypass switch to bypass current, and thus reducing the equivalent timing capacitance of the switching control circuit for increasing the maximum duty cycle of the switching control circuit.

Abstract: Disclosed herein is a flyback converter with a synchronous rectifier which is applied to a power supply of a portable computer such as a notebook PC. The flyback converter is operated in a critical conduction mode to turn on/off a main switch at a zero crossing point of an output voltage. The flyback converter is also adapted to control the duty cycle of a synchronous switch using a Zener diode. Therefore, there is no need for a Schottky diode to be connected in parallel with the synchronous switch, resulting in simplification in circuit design.

Abstract: The invention relates to a switched mode power supply with current mode control, in which an inductive element (7) is connected to a power source (5) by means of a controllable switch (9). During closure of the switch (9) the increasing current through the inductive element (7) is sensed by a current sensor (17) and compared with a reference signal (18). When the signal from the current sensor is equal to the reference signal, the switch (9) is opened. Due to circuitry delays the off-switching of the switch (9) occurs at a higher current level than sensed by the current sensor (17). To compensate for this effect the switched mode power supply has means (16, 19, 15) for generating a compensation signal (Ic*R15) proportional to the gradient (di/dt) of the current i through the inductive element (7). The circuitry delay can be compensated for by a suitable choice of values of components (15, 19, 16).

Abstract: A method of controlling the output voltage of a voltage regulator that uses a transimpedance block is disclosed. The method comprises measuring the voltage representative current of the output and comparing the voltage representative current to a reference current. Finally, the charging process is stopped if the voltage representative current of the secondary winding is substantially the same as the reference current.

Abstract: A control circuit controlling output current at the primary side of a power converter is provided. A waveform detector generates a current-waveform signal. A discharge-time detector detects a discharge-time of a secondary side switching current. An oscillator generates an oscillation signal for determining the switching frequency of the switching signal. An integrator generates an integrated signal by integrating an average current signal with the discharge-time. The average current signal is generated in response to the current-waveform signal. The time constant of the integrator is correlated with the switching period of the switching signal, therefore the integrated signal is proportional to the output current. An error amplifier amplifies the integrated signal and provides a loop gain for output current control. A comparator controls the pulse width of the switching signal in reference to the output of the error amplifier. Therefore, the output current of the power converter can be regulated.

Abstract: A switching power source which enables a continuous operation of an apparatus even under an overvoltage test such as a ring wave test. In a case where the sensed voltage (Vb) of the secondary winding (5b) through a diode (D6), the Zener diode (ZD3), and a resistor (R21) to the non-inverting input terminal (+) of a comparator (31), and a high-level signal is inputted to a flip-flop (35) from the comparator (31). As a result, a high-level signal outputted from the Q output terminal is held and outputted to a flip-flop (15) as a reset signal via an OR circuit (37), so that a drive signal kept outputted from the Q output terminal of the flip-flop (15) switches to a low-level one to continue the off-control of the switching element (Q1).

Abstract: There is provided with a breaking resistor R6 inserted at an arbitrary portion of a current path from the output point 21 of a primary side positive power supply IN+ to the drain of an FET 5. Supposing that a value obtained by dividing a resistance value by a rated watt is a broken index, the broken index of the breaking resistor R6 is set to be larger than that of a current detection resistor R1.

Abstract: A switching power supply that can operate in critical conduction mode as self-oscillating power supply (SOP) during moderate load, and in discontinuous conduction mode (DCM) under the control of a pulse-width modulated signal under small load, whereby the power consumption of the supply is decreases continuously as the load is decreased. A frequency modulated self-oscillating switching power supply (FMSOP) having a power switch, the switch being held OFF, after a zero-current detector detects that an output current falls to zero, until allowed to turn ON after a pulse having a load-modulated width that corresponds to the load. The FMSOP operates with a switch controller that may include a flip-flop to latch the detector's signal, a load-modulated pulse generator, and a combinatorial logic gate to combine the pulse and the latched signal.

Abstract: A circuit configuration for generating a switching signal for a current controlled switched mode power supply includes a transformer with windings, a controlled power breaker, in series with a primary winding and a supply DC voltage, a control circuit, for cycle clocked switching of the power switch, a current measuring device measuring the current flowing through the power switch and generating a measured signal as a measure of the measured current value, a reference signal source generating a time-independent constant reference signal, and a comparator circuit comparing the measured signal with the reference signal and signaling the control circuit to switch off the power switch when the measured signal is greater than the reference signal. The reference signal source is connected to a compensation signal source to generate a compensation signal changing over time, the reference signal arising from the sum of the constant reference signal and the compensation signal.

Abstract: A pulse width modulation controller is coupled to a feedback voltage that is proportional to the power supply output voltage. The controller adjusts a current sense threshold in the controller in response to the feedback voltage. An offset voltage is generated for a predetermined time after the power-up of the power supply. A sum of the offset voltage and a primary current sense node voltage is applied to a current sense input of the controller. The controller generates a switch control signal in response to the sum voltage being less than the current sense threshold. The duty cycle of an output control switch is changed by the switch control signal thus adjusting the output voltage ramp.

Abstract: A power conversion apparatus capable of reducing the conduction loss to achieve high efficiency yielding a downsized and weight-reduced apparatus and a method for driving such a power conversion apparatus is disclosed. A power conversion apparatus comprising a switching-element driving circuit which includes a current transformer having a primary coil connected to an current control type switching element, and a driving-current generating circuit formed of a secondary coil of the current transformer and a rectifying circuit connected to the secondary coil, wherein an output current generated in the driving-current generating circuit is supplied to the switching element as a driving current of the switching element, and a method for driving the switching element of such a power conversion apparatus are disclosed.

Abstract: A current-mode switching regulator that maintains a substantially constant maximum current limit over a virtually full range of duty cycles is provided. The regulator has a control circuit that includes a buffer circuit, an adjustable voltage clamp circuit, and a slope compensation circuit. The buffer circuit isolates a control signal from capacitive loading associated with control circuit. The threshold level of the adjustable voltage clamp circuit varies with respect to the amount of slope compensation provided to the voltage regulator. This allows a control voltage to increase as slope compensation increases so that a substantially constant maximum current limit is maintained.

Abstract: The invention is directed to a switched mode power supply, in particular a flyback converter, with a device for limiting the output voltage. To provide a safeguard against excessive output voltages, a Schottky diode is connected in reverse direction between the output terminals of a switched mode power supply of the invention.

Abstract: The present invention provides an apparatus and method for reducing the voltage stress in a single-stage single-switch (SSSS) converter by modulating the predetermined operating frequency of the converter lower responsive to increasing voltage stress. A control circuit (116) and associated cooperable frequency setting capacitance (CT) and resistance (RT) are coupled to the primary circuit (112) and the secondary circuit (114) of the SSSS converter via a switch (120). A frequency foldback device (180) is coupled to CT or RT and cooperable therewith to lower bus voltage stress by modulating the switch frequency. The operating frequency is modulated (i.e. reduced) from the predetermined operating frequency upon detection of a voltage threshold transition.

Abstract: The power supply for LEDs of the present invention provides power to a variable number of LEDs wired in series or in parallel. The power supply uses current feedback to adjust power to the LEDs and provides protection against open circuits and circuit malfunctions. A current controller compares sensed current to a reference current and generates a feedback signal, which is processed by a power factor corrector to adjust the current flow through the transformer supplying current to the LEDs.

Abstract: An apparatus for effecting a preload operation of an electrical converter device that includes a primary circuit section inductively coupled with at least one secondary circuit section presenting at least one output voltage at at least one output locus includes: (a) a load coupled with at least one selected output locus of the at least one output locus; (b) a switch device electrically coupling the load within the at least one secondary circuit section; and (c) a timer device coupled with the switch device. The timer device orients the switch device to electrically disconnect the load from the at least one secondary circuit section after a predetermined time interval elapses.

Abstract: A current-mode switching regulator that maintains a substantially constant maximum current limit over a virtually full range of duty cycles is provided. The regulator has a control circuit that includes a buffer circuit, an adjustable voltage clamp circuit, and a slope compensation circuit. The buffer circuit isolates a control signal from capacitive loading associated with control circuit. The threshold level of the adjustable voltage clamp circuit varies with respect to the amount of slope compensation provided to the voltage regulator. This allows a control voltage to increase as slope compensation increases so that a substantially constant maximum current limit is maintained.

Abstract: Methods and arrangements are provided for regulating low output voltages in multiple output flyback DC/DC converters that generate, in addition to a main output DC voltage, at least one additional output DC voltage. Converter arrangements include a transformer with a primary winding connected in series with a primary switch, a first secondary winding connected in series with a first rectifier to a first output capacitor for generating the main output DC voltage, and a secondary winding connected in series with a synchronous rectifier to a second output capacitor for generating the additional output DC voltage.

Abstract: A method and apparatus is arranged to produce high precision output voltage matching in a multiple output power converter. A two-output voltage converter includes a positive and a negative voltage output that are approximately equal in magnitude. The power converter includes inductors, transfer capacitance circuitry, and a controlled switching circuit. In one operating mode, the switching circuit is closed, the inductors are charged, and energy from the input signal is stored in the transfer capacitance circuitry. In a second operating mode, the switching circuit is opened, and the stored energy is transferred to the output loads. The transfer capacitance circuitry is arranged to provide improved matching in the output voltages. The two-output power converter topology may be extended to provide multiple outputs.

Abstract: A method and a power conversion apparatus having a substantially direct current input voltage, an output transformer having a primary inductor and at least a secondary winding, and a transistor for controlling the transfer of energy from the primary inductor to the secondary winding and coupled to a controller for switching the transistor on and off at a predetermined rate. A sensor for sensing the power required at the output of the conversion apparatus and for generating a voltage representative thereof is provided, as is provided a sensor for sensing the peak current in the primary inductor and for developing a voltage representative thereof.

Abstract: A multimode switched-mode power supply operates in a first control mode when the output power supplied is lower than a predetermined value, and in a second control mode when the output power supplied is higher than said predetermined value. The switched-mode power supply comprises a series arrangement of a switch (S1) and an inductor (L; Lp), the series arrangement being coupled to receive a DC input voltage (Vin). A control circuit (CC) controls the on and/or off times of the switch (S1) to generate a periodical inductor current (Ip) in the inductor (L; Lp). In the first control mode, a peak value of the inductor current (Ip) is substantially constant, independent of the power supplied. The substantially constant peak value is substantially equal to a peak value of the inductor current (Ip) at an instant when the second control mode is altered into the first control mode.