Abstract: Methods and apparatus for sensing the output current in a switch mode power supply (SMPS) using primary side sensing are described. A module senses a current in a primary winding of a transformer and a voltage on a primary or auxiliary winding of the transformer, and which includes a multiplier coupled to an output of a signal averager averaging a primary winding current and to an output of a timing signal generator using the sensed voltage to signal when a secondary winding is powering an output of the SMPS, to multiply an averaged current sense signal by a fraction of a total cycle period of said SMPS during which the secondary winding is providing power to provide a signal estimating an output current of the SMPS.

Abstract: A DC-DC converter is provided, which includes a transformer including a primary coil and a secondary coil, a boost converter connected to the primary coil of the transformer and generating a first voltage, and a flyback converter connected to the secondary coil of the transformer and generating a second voltage.

Abstract: The present invention is directed to a power supply unit that provides large power supply to the load. The voltage detector 51 generates a voltage detection signal by detecting the voltage generated at the output terminals 21, 22. The current detector 52 generates a current detection signal by detecting the current that runs through the transformer 3. The control circuit 9 uses the voltage detection signal and the current detection signal and thereby controls, in at least one of the first and second switching elements SW1, SW2, the timing with which the switching element is turned ON and the length of time that the switching element remains ON, such that the transformer current flows in a continuous mode.

Abstract: In the PWM circuit of the present invention, a PWM counter counts clock signals. A reference value setting register sets a comparative reference value for determining a duty ratio of a PWM signal. A comparator generates the PWM signals based on a comparative result of the comparative reference value and a count value of the PWM counter. A delay device delays the PWM signal. A switching device switchably outputs the output of the comparator and the output of the delay device in order of time sequence. Thereby, the pulse phase of the PWM signal can be adjusted.

Abstract: A switching power supply for achieving a constant current drooping characteristic of sufficient accuracy with low cost and the minimum number of components. In the switching power supply, a secondary duty limiter circuit outputs a clock signal from the time a switching element is turned off until the time the on duty of secondary current, which starts flowing to a secondary winding of a transformer, is fixed at a predetermined value. A clock signal selector circuit selects and outputs the clock signal when a load increases and the on duty of the secondary current reaches the predetermined value. Consequently, when the load increases, a direct current output voltage decreases and an output characteristic becomes a constant current drooping characteristic.

Abstract: A soft switching power converter includes a first switch for switching a transformer to transfer energy. A second switch is equipped to switch energy in a capacitor to the transformer to achieve soft switching for the next switching cycle. A control circuit is coupled to an output of the power converter for generating a first signal and a second signal in response to a feedback signal for regulating the output of the power converter. A first delay time is generated after the first switch is turned off and before the second signal is on. A second delay time is generated after the second switch is turned off and before the first signal is on. The second delay time is increased corresponding to a decrement of the feedback signal under light load conditions.

Abstract: A linear power controller and related circuitry may be implemented to provide linear control of a variable DC electric motor. The controller and motor are coupled to form a closed loop for controlling the speed of the motor and for adjusting or compensating for noise and other characteristics having a negative impact on performance. The circuitry is configured to have a crossover frequency that is below the motor noise frequency. The configuration of the crossover frequency may allow for the motor or the controller to be implemented without additional circuitry to filter or compensate for motor noise.

Abstract: This invention generally relates to discontinuous conduction mode switch mode power supply (SMPS) controllers employing primary side sensing. We describe an SMPS controller which integrates a feedback signal from a point determined by a target operating voltage to a peak or trough of an oscillatory or resonant portion of the feedback signal when substantially no energy is being transferred to the SMPS output. When regulation is achieved this value should be zero; the difference from zero can be used to regulate the output voltage of the SMPS.

Abstract: The present invention discloses a primary-side feedback switching power supply that uses a sample-and-hold circuit to obtain a corner voltage of a harmonic wave voltage while the primary-side auxiliary winding is operating at a discontinuous mode as a feedback control, and provides both voltage regulation and current limit functions. A stable voltage output is provided within the nominal input voltage and nominal output load, such that when the output reaches a current limit, the output voltage drops but the output current is controlled to remain unchanged, so as to provide an over-current protection.

Abstract: A control circuit 6 of a resonance type switching power source comprises a drive circuit 21 for supplying drive pulses to each gate terminal of first and second MOS-FETs 2,3; a PWM circuit 9 for causing drive circuit 21 to produce drive pulses; an input voltage detector 7 for detecting input voltage from DC power source 1 and comparing the input voltage and input reference voltage Vref1; and a frequency adjuster 8 for adjusting oscillation frequency of PWM circuit 9 in response to output level from the input voltage detector 7. With adjustment in oscillation frequency of PWM circuit 9 in response to input voltage Vin from DC power source 1, control circuit 6 can modify on-off timing of first and second MOS-FETs 2, 3 to keep good resonating action and prevent off-resonance although DC power source 1 produces fluctuating input voltages.

Abstract: Hot swappable pulse width modulation power supply circuits preferably realized in integrated circuit form. The hot swap circuits provide for de-bouncing, controlled charging of the input capacitor of the power supply circuit and soft-start of the pulse width modulator after charging the input capacitor. Other features include a low voltage lockout, and an output for coupling to a synchronous rectifier driver to synchronize synchronous rectifiers on the secondary side of a coupling transformer in isolated systems. The hot swap capability may be disabled through an enable pin, or not implemented by not connecting the integrated circuit in a manner to use the hot swap capability.

Abstract: A DC-DC converter is provided which comprises an inductance element 10 having a plurality of in-phase windings NB, NA wound around a common magnetic core and connected to a load 5; a normal power source 16 for generating a reference voltage; a comparator 18 for comparing a voltage produced across winding NA with reference voltage VR of normal power souce 16 to produce an error signal. As a same electric current IO flows through the windings NB, NA of inductance element 10 in the opposite directions to each other to produce in magnetic core of inductance element 10 opposed magnetic fluxes which countervail each other and any kind of noise such as ripple and spike noises causing voltage fluctuation.

Abstract: A switching power supply for achieving a constant current drooping characteristic of sufficient accuracy with low cost and the minimum number of components. In the switching power supply, a secondary duty limiter circuit outputs a clock signal from the time a switching element is turned off until the time the on duty of secondary current, which starts flowing to a secondary winding of a transformer, is fixed at a predetermined value. A clock signal selector circuit selects and outputs the clock signal when a load increases and the on duty of the secondary current reaches the predetermined value. Consequently, when the load increases, a direct current output voltage decreases and an output characteristic becomes a constant current drooping characteristic.

Abstract: An object of the present invention is to lower the voltage applied to the starting resistor of the starting circuit in a switching power supply circuit to reduce the power loss especially when the receiving voltage is high and thereby provide a small and inexpensive switching power supply circuit. According to the present invention, a switching power supply circuit comprises: a DC voltage section having two or more capacitors connected in series; and a PWM control circuit for receiving DC power supply from the DC voltage section and performing switching control on a primary side of a transformer in order for the switching power supply circuit to output a DC voltage of different voltage specifications; wherein the starting resistor for the PWM control circuit is connected to a connection point of the capacitors.

Abstract: System and method for protecting a power converter. The system includes a compensation system configured to receive an input signal and generate a control signal, a cycle threshold generator configured to receive the control signal and generate a cycle threshold, and a comparator configured to receive the cycle threshold and a feedback signal and generate a comparison signal. Additionally, the system includes a pulse-width-modulation generator configured to receive the comparison signal and generate a modulation signal in response to the comparison signal, and a switch configured to receive the modulation signal and control an input current for a power converter. The input current is associated with an output power for the power converter. The cycle threshold corresponds to a threshold power level for the output power. The threshold power level is constant, decreases, or increases with respect to the input signal.

Abstract: A PWM signal to DC voltage converting unit includes at least a switch section adapted to provide an on/off function; a driving section electrically connected to the switch section for driving the switch section to provide the on/off function; a first voltage stabilizing section electrically connected to the switch section for generating a voltage; a bridging section electrically connected to the first voltage stabilizing section for keeping the first voltage stabilizing section in one-direction transmission; a second voltage stabilizing section electrically connected to the bridging section for generating a voltage; and an electricity-storing section electrically connected to the second voltage stabilizing section, such that power transmitted by the first and the second voltage stabilizing section may be charged to or discharged from the electricity-storing element. By controlling a duty cycle of an input PWM signal, the output voltage can be adjusted.

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: A high voltage supply device including a power supply rectifying an externally inputted ac voltage and generating a first dc voltage and a second dc voltage, a controller generating a pulse signal having a predetermined duty ratio and a control signal having a first logic level when the first dc voltage is applied, a high voltage generator boosting the second dc voltage based on the pulse signal, and a power supply controller driven when the control signal is in the first logic level, and cutting off an application of the second dc voltage to the high voltage generator when the control signal is in a second logic level. Such a high voltage supply device, when used in electronic devices such as laser printers, facsimile machines and DC—DC converters requiring a high dc voltage, does not generate a surge voltage when the electronic devices are turned off.

Abstract: A dual-mode converter for converting power from an input voltage level to an output voltage level, the dual-mode converter including an inductor section having an input side and an output side, the input side receiving an input signal and the output side outputting at least one output signal based on a power value of the input signal, a feedback loop section which receives a feedback signal from one or more of the at least one output signals, the feedback loop section including a first transistor, a second transistor and a comparator unit which outputs a comparator output signal based on a comparison of the feedback signal to a comparator reference signal, wherein the respective states of the first and second transistors configure the feedback loop section to function as either a linear mode or a comparator mode, a current mode controller unit which receives the input signal, the feedback signal, and a current sense signal representing a sensed current flowing through the input side of the inductor section, t

Abstract: A switching power supply circuit, which can respond to a rapid and large change in a load quickly and stably and ensure a power supply output having a predetermined voltage, is provided. In the power supply circuit which supplies an input current to a load while switching the input current periodically and controls an output voltage Vo supplied to the load to a predetermined target value by controlling an ON/OFF time ratio (t1/t2) of the switching variably, a control of the ON/OFF time ratio is performed for every one current supply cycle T independently.

Abstract: A transformer has a primary winding connected between a pair of dc input terminals via a voltage regulator switch, and a secondary winding connected between a pair of dc output terminals via a rectifying and smoothing circuit. The dc output voltage being applied to the load from the dc output terminals is detected, and the detector output voltage dually divided, to provide two feedback signals of different magnitudes. One of these feedback signals is used by a mode selector circuit to provide a mode select signal for causing the voltage regulator switch to be driven continuously under normal load, and at intervals under light load. Delivered to a conduction terminator circuit, the other feedback signal is thereby used to provide conduction terminator pulses for terminating conduction through the voltage regulator switch.

Abstract: An apparatus and method thereof for measuring an output current from a primary side of a power converter are provided. A peak detector is designed to sample a peak value of a converted voltage of a primary-side switching current. A zero-current detector detects a discharge-time of a secondary-side switching current through an auxiliary winding of a transformer. An oscillator generates a switching signal for switching the power converter. An integrator generates an integrated signal by integrating the converted voltage of the primary-side switching peak current with the discharge-time. The time constant of the integrator is correlated with the switching period of the switching signal. The integrated signal is thus proportional to the output current of the power converter.

Abstract: A power-mode controlled power converter is capable of supplying a constant output voltage and output current. A PWM controller generates a PWM signal in response to a voltage sampled from a transformer auxiliary winding. A programmable current-sink and a detection resistor compensate for a voltage drop of an output rectifier. A low-pass filter integrates a switching-current voltage to an average-current signal. An attenuator produces an input-voltage signal from a line-voltage input signal. The PWM controller multiplies the average-current signal with the input-voltage signal to generate a power-control signal. An error-amplifier compares the power-control signal with a power-reference voltage to generate a limit voltage. The limit voltage controls the power delivered from a primary-side circuit to a secondary-side circuit of the power-mode controlled power converter. Since the power-reference voltage varies in proportional to output voltage variations, a constant output current is therefore achieved.

Abstract: A switching power supply includes a switch, a bias-sensor to sense the switch-voltage, and a zero-crossing detector (ZCD) to sense time instances when the bias-sensor voltage crosses zero. ZCD generates a ZCD-signal, which transitions between a first and a second level at the sensed crossing instances, with a delay. ZCD-signal is coupled to a blanking circuit, generating a blank-signal and a pulse-signal, controlling the switch. The on-time of the switch can be modified by the input voltage and load. The blank-signal between on-times is adjusted to compensate for this modification, keeping the switching frequency below a predetermined limit and reducing the switching frequency. The switching power supply further includes a pulse width modulation (PWM) signal generator, coupled to the blanking circuit and to the switch. PWM signal generator turns on the switch controlled by the pulse-signal of the blanking circuit. Blanking circuit is controlled by either the on-time or a control voltage and input voltage.

Abstract: A switching power source comprises a current comparator 27 for comparing a voltage level of signals acquired by a current detector 9 with a reference voltage level VDT to produce detection signals VCP of first or second level L or H; an edge detector 28a for sensing an edge of drive signal VG supplied to a gate terminal of MOS-FET 3 during the period of transition from turning on to off of MOS-FET 3; and a decision means 28b for receiving a current detection signal VCP from current comparator 27 to produce an output signal VLD when edge detector 28a catches an edge of drive signal VG; wherein decision means 28b produces different output signals VLD of respectively first and second voltage levels L and H under the light and heavy load conditions to precisely and certainly detect on the primary side of transformer 2 the load condition on the secondary side of transformer 2 for improvement in conversion efficiency.

Abstract: The object of the present invention is to improve the power factor and at the same time to obtain a high efficient operation.

Abstract: A driving circuit comprises an input terminal receiving an input of a PWM signal, a first output terminal connected to a main switch for outputting a low-side driving signal, a second output terminal connected to an active switch for outputting a high-side driving signal, a first branch having a voltage level shifting capacitor and a first buffer connected in series between the input terminal and the second output terminal; and a second branch having a delay circuit and a second buffer connected in series between the input terminal and the first output terminal. When the input of the PWM signal turns from a low level to a high level, the voltage level shifting capacitor transmits the input of PWM signal to the first buffer for turning off the active switch and then triggering the second buffer to turn on the main switch with a short time delay.

Abstract: A DC-DC converter circuit for stabilizing the output voltage of the secondary side by correcting the input voltage by using a simple circuit, where no state measurement circuit is necessary at the secondary side. The circuit includes a transformer; a switching circuit including a main switching element which is connected to the primary winding of the transformer in series and has a control terminal for controlling the main switching element, wherein the main switching element is PWM-controlled so as to stabilize an output voltage of the secondary side; a driving circuit for generating PWM driving pulses; and a correction circuit for outputting a voltage whose level is in inverse proportion to an input voltage of the DC-DC converter circuit. An output of the driving circuit is connected to the control terminal of the main switching element and to the correction circuit.

Abstract: A synchronous rectifier PWM (SR-PWM) controller controls a MOSFET in response to the value of a secondary current and the status of a synchronous signal for both discontinuous and continuous operation mode. The secondary current is generated in a secondary circuit and is detected by two threshold-detection terminals of the SR-PWM controller. The SR-PWM controller produces the synchronous signal by detecting a switching signal of the transformer via a detection terminal of the SR-PWM controller. Furthermore, a delay-time is inserted after the MOSFET is turned off and before the next switching cycle starts to ensure a proper operation of the MOSFET. In one embodiment, an equivalent series resistance (ESR) of an output capacitor can be used as a sensor to detect the secondary current. Therefore, no additional current sensor is required.

Abstract: A radiation tolerant electrical component is provided without a radiation hardened material FET. A p-channel MOSFET provides switching capabilities in radiated environments because its gate voltage starts at a negative value and becomes more negative with exposure to radiation. Therefore, the gate is still controllable when exposed to radiation.

Abstract: A 384X-based burst mode PWM controller includes an oscillator to generate a pulse signal of a constant frequency, an output circuit to generate an output signal based on the pulse signal, an error amplifier to generate an amplified error signal, a logic control current source connecting to a current sense input of a comparator, the comparator which compares the voltage of the current sense input with the voltage of the error signal to generate a comparison signal, a PWM latch to generate a pulse control signal corresponding to the pulse signal and based on the comparison signal. The pulse control signal controls the output circuit and the logic control current source in opposite conditions of turning on and off. The controller can replace 384X directly and save energy.

Abstract: It is an object to control the peak of drain current and control overload in a same switching device in a switching power supply which has a load of a transformer and so on, and to prevent a complicated circuit and an increase in the number of terminals of a control circuit. Overload protection is performed as follows: according to a change in a feedback current which is an input to a feedback signal control circuit, the peak value of the current of a switching element, a switching operation is performed intermittently to reduce power consumption when the feedback current decreases at a light load, and an increase in the voltage of an FB terminal is detected and the switching operation is stopped in an overload state where overload protection is performed on the switching element.

Abstract: A voltage regulator for use in a charging device of a portable electronic apparatus is disclosed. The voltage regulator includes a transformer having a primary winding and a secondary winding, a switch circuit being controlled via a control end thereof so as to result in a variable current on the primary winding, a rectification circuit electrically connected to the secondary winding, and proceeding a charging operation in response to an induced current, and a micro-controller electrically connected to the switch circuit and generating a pulse width modulation (PWM) signal to the control end in response to the charging operation. In addition, a method for operating a voltage regulator is also disclosed.

Abstract: A primary side sensing power control system and method that controls the current limit such that it is maintained within a small range for any acceptable input voltages and causes the output voltage of a PWM controller to drop as the output load increases when the current limit is reached.

Abstract: A switching power converter and method of controlling an output voltage thereof using predictive sensing of magnetic flux provides a low-cost switching power converter via primary-side control using a primary-side winding. An integrator generates a voltage that represents flux within a magnetic element by integrating a primary-side winding voltage. A detection circuit detects the end of a half-cycle of post-conduction resonance that occurs in the power magnetic element subsequent to zero energy level in the power magnetic element. The integrator voltage is stored at the end of the half-cycle and is used to determine a sampling point prior to or equal to the start of post-conduction resonance in a subsequent switching cycle of the power converter. The primary-side winding voltage is then sampled at the sampling point, providing an indication of the output voltage of the power converter by which the output voltage of the converter can be controlled.

Abstract: The use of low permeability magnetic material (NSME) with the disclosed design strategies form a two-stage isolated output converter system with the distinct advantages of superior density, efficiency, thermal operating bandwidth, service life, transient survival, and form factor flexibility over the prior art. These improvements are realized by, optimized application of NSME, efficient rectifying flyback management techniques, inclusion of switching buffers that substantially reduce switching losses. The instant invention provides power factor correction, output regulation, inrush limiting, over voltage, over current, over temperature, and transient protection, multi-converter load sharing, hot swapability, and fault signals. The disclosed system is designed, specified, and certified to function from ?40 deg. C. to +65 deg. C. from a 180 vac to 264 vac 50/60 Hz input line and supports 1000 watts of output or 600 watts from 90 vac to 120 vac 50/60 Hz line input at greater then 0.

Abstract: An object of the present invention is to provide a computer power supply in which, by improving the circuit itself, internal heat loss can be reduced, thereby greatly improving efficiency. A partial resonance circuit 8 is constituted by a primary side winding N1 of a high frequency transformer 3, a resonance condenser 7, and two switching elements Q1, Q2, a secondary side output circuit 4 for driving a load is connected to a secondary side of the high frequency transformer 3 via a winding, and a reverse converter 11 for driving and halting the first switching element and second switching element by causing the respective phases thereof to differ on the basis of a driving signal is provided.

Abstract: A switching power supply includes a control circuit disposed between a feedback winding and a switching device. The control circuit includes an on-period control circuit that, in an operation under a non-low load condition, controls an on-period of the switching device such that the on-period decreases with decreasing load, a minimum on-period setting circuit that disables the on-period control circuit in an operation under a low load condition so that the on-period of the switching device does not become shorter than a predetermined minimum on-period, and an off-period control circuit that controls an off-period of the switching device in the operation under the low load condition such that the off-period increases with decreasing load. As a result, the output voltage is maintained at a constant value in accordance with a feedback signal.

Abstract: A current detection method for an electric motor which detects phase currents of the electric motor driven by a power converter that provides ON/OFF control of bridge-connected switching elements, based on a pulse-width modulation excitation pattern, to convert a direct current into poly-phase alternating currents. The method includes connecting a current detecting element which produces a signal corresponding to a current value at the direct current side of the power converter and changing the pulse-width modulation excitation pattern by executing a shift of time of any of the phases of the pulse-width modulation excitation pattern so that a signal directly or indirectly corresponding to the phase currents is produced at the current detecting element. The method also includes detecting the phase currents of the electric motor based on the signal produced at the current detecting element and the excitation pattern which has been changed.

Abstract: A method of regulating voltage at an output of a switching power converter includes sensing an output voltage feedback signal; comparing the sensed feedback signal to a reference at a determined time during a cycling of the switch; and regulating the output voltage by either enabling or inhibiting cycling of a switch by a cycle of a drive signal produced by pulse generation circuitry in response to an output of the comparison.

Abstract: An AC adapter which reduces the amount of power drawn from an AC power source when a system is disconnected from the adapter, includes: a rectifier bridge for rectifying an AC voltage from an AC power supply; a conversion circuit coupled to the rectifier bridge for converting the rectified AC voltage to a DC voltage; and an opto-coupler coupled to the conversion circuit for monitoring an output connection of the circuit, wherein when a system is not coupled to the output connection, the opto-coupler substantially prevents the AC voltage from being drawn from the AC power supply. The adapter circuit uses an opto-coupler comprising a diode and a transistor to reduce the amount of current drawn from an AC power supply when a system is not connected to the AC adapter. In this manner, the AC adapter is prevented from becoming heated when no system is connected.

Abstract: Switching power converters for regulating voltage at an output of a load include digital control circuitry for sensing an output voltage feedback signal, comparing the sensed feedback signal to a reference at a determined time during a cycling of the switch; and regulating the output voltage by either enabling or inhibiting cycling of a switch by a cycle of a drive signal produced by pulse generation circuitry in response to the comparison.

Abstract: The present invention provides a primary-side flyback power converter that supplies a constant voltage output and a constant current output. To generate a well-regulated output voltage under varying load conditions, a PWM controller is included in the power converter in order to generate a PWM signal controlling a switching transistor in response to a flyback voltage sampled from a first primary winding of the power supply transformer. Several improvements are included in this present invention to overcome the disadvantages of prior-art flyback power converters. Firstly, the flyback energy of the first primary winding is used as a DC power source for the PWM controller in order to reduce power consumption. A double sample amplifier samples the flyback voltage just before the transformer current drops to zero. Moreover, an offset current is pulled from a detection input of the double sample amplifier in order to generate a more accurate DC output voltage.

Abstract: A flyback converter detects an output voltage at the primary coil without using a photo coupler and provides an essentially constant output voltage independent of the load size, thereby minimizing the number of additional coils used in the transformer circuit to realize simple construction and providing accurate power control. In one embodiment, the flyback converter includes: a transformer for changing an input voltage to a predetermined level according to a winding ratio; an output unit for rectifying the voltage signal output from the transformer into a DC signal to drive a load; a switch coupled to the primary coil of the transformer for controlling the on/off state of a power at the primary coil according to a switching control signal; a feedback unit generating a feedback signal and detecting a current of the switch to correct the feedback signal; and a switching controller operating according to the feedback signal.

Abstract: The present invention provides a primary-side regulated PWM controller with improved load regulation. In every PWM cycle, a built-in feedback voltage samples and holds a flyback voltage from the auxiliary winding of the transformer via a sampling switch and generates a feedback voltage accordingly. A bias current sink pulls a bias current that is proportional to the feedback voltage. Via a detection resistor, the bias current will produce a voltage drop to compensate the voltage drop of an output rectifying diode as the output load changes. According to the present invention, the bias current can enable the PWM controller to regulate the output voltage very precisely without using a secondary feedback circuit.

Abstract: Several synchronization circuits, a computer, a method of adjusting the operation of an oscillator, and method of operating a power converter are disclosed. The circuits and computer include a switch coupled to a current path. The switch receives a synchronizing signal, and is turned on by an active state of the synchronizing signal, and turned off by an inactive state of the synchronizing signal. The current path is configured to pass a current when the switch is off, and the switch is configured to pass the current when turned on. This abstract is provided to comply with the rules requiring an abstract that allow any reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A synchronous control circuit of a flyback switching power supply is connected to a secondary side of a transformer. The synchronous control circuit has several sets of power source ends and a set of induction ends. One output end of the power source ends is connected to a rectifying circuit for rectifying the voltage waveform of the power source ends. The induction ends are connected with a rectifying diode to form a detection end. A synchronous control circuit is connected with the power source ends and the detection end, and has a synchronous input end, a control end, and a waveform adjustment end. The synchronous input end is used for input of a synchronous signal. The control end is connected to the rectifying circuit. The waveform adjustment end is connected to a resistor for controlling the rectifying circuit to generate a uniform rectifying response period.

Abstract: Several synchronization circuits, a computer, a method of adjusting the operation of an oscillator, and method of operating a power converter are disclosed. The circuits and computer include a switch coupled to a current path. The switch receives a synchronization signal, and is turned on by an active state of the synchronizing signal, and turned off by an inactive state of the synchronizing signal. The current path is configured to pass a current when the switch is off, and the switch is configured to pass the current when turned on. This abstract is provided to comply with the rules requiring an abstract that allow any reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: Incorporating the PWM function with the power saving means develops the PWM controller in which the switching frequency is decreased in response to the decrease of the load. Further, the current-driven design minimizes the circuitry and reduces the cost of the PWM controller. Since most of the control signals are operated in current mode, the die size of integrated circuit of the PWM controller is greatly reduced. An off-time modulator is provided for power saving in which the discharge current of the oscillator is modulated. Keeping the maximum on-time of the PWM signal as a constant and increasing the off-time of the PWM signal extends the switching period in light load conditions. The off-time modulation is the function of a feedback current, which is derived from the feedback loop. An array of current operation is designed to generate the feedback voltage for the PWM control and meanwhile produces a modulated discharge current for power saving.

Abstract: A single input pin (48) provides multi-functional features for programming a power supply (10). By connecting the appropriate interface circuit (92, 100, or 112) to the single input pin (48), the power supply (10) is programmed for specific behaviors during power up and toggling of an on/off switch (96, 108). In one mode of operation a light emitting diode (106) in the interface circuit (100) is optically coupled to a microprocessor for signaling the closure of the on/off switch (108), allowing the microprocessor to control the power supply (10) through an opto-coupler (102). In another mode of operation, the single on/off switch (96) controls the power supply (10). In yet another mode of operation, Zener diode (118) in the interface circuit (112) controls the power supply (10) during brown-out and black-out conditions.