Abstract: A switching power source device which has main switch elements which switch a current path of the series resonant circuit, and a transformer which induces a current to a secondary side, controls the main switch elements on a primary side. Synchronous rectification switch elements are turned ON and OFF in response to one of the main switch elements. A synchronous control circuit which turns the synchronous rectification switch element ON in synchronization with an ON timing of the main switch element, or a conduction timing of internal diodes in the synchronous rectification switch elements detected by an inter-terminal voltage signal of the synchronous rectification switch element, whichever timing is later, determines a maximum ON width of the synchronous rectification switch element in accordance with a delay time of the conduction timing of the internal diodes with respect to the ON timing of the main switch element.

Abstract: The present invention includes: a plurality of switching elements connected in series and connected between two ends of a DC power supply; a first control circuit to alternately turn on and off the switching elements in response to a constant oscillation frequency signal; a series circuit including a primary winding of a transformer and a capacitor connected together in series, and being connected to a connecting point between the switching elements, and to an end of the DC power supply; a rectifying/smoothing circuit to rectify and smooth a voltage in a secondary winding of the transformer thereby to output a DC voltage; a control switching element connected to two ends of the primary or secondary winding of the transformer; and a second control circuit to control the DC voltage at a predetermined voltage by turning on and off the control switching element.

Abstract: The configurations of a resonant converter system and a controlling method thereof are provided. The proposed resonant converter system includes a resonant converter receiving an input voltage for outputting an output voltage, a rectifying device having a first rectifying switch and a synchronous rectification control circuit coupled to the resonant converter and including a signal generation apparatus generating a weighted turn-off signal to turn off the first rectifying switch at a zero crossing point of a first current flowing through the first rectifying switch.

Abstract: An embodiment apparatus comprises a secondary synchronous rectifier and a secondary gate drive controller coupled to a transformer winding. The secondary gate drive controller is configured to generate a forward gate drive signal for the forward switch and generate a freewheeling gate drive signal for the freewheeling switch, wherein the secondary gate drive controller generates a dead time between the forward gate drive signal and the freewheeling gate drive signal.

Abstract: An embodiment apparatus comprises a secondary synchronous rectifier and a secondary gate drive controller. The secondary gate drive controller coupled to a transformer winding comprises a secondary synchronous rectifier soft start signal generator configured to generate a plurality of soft start pulses, a pulse width modulation generator configured to generate a forward switch drive signal and a freewheeling switch drive signal based upon a signal across the transformer winding and a soft transition generator configured to generate a soft start freewheeling switch drive signal by gradually releasing the freewheeling switch drive signal during a soft start process.

Abstract: Novel system and methodology are provided for controlling a DC/DC forward converter having a transformer with primary and secondary windings, a reset switch, and a first switch coupled to the primary winding of the transformer. The control system involves a PWM control circuit responsive to an output signal of the converter for producing a PWM signal to control switching of the reset switch, and the first switch. A period of the PWM signal includes an on-time interval for enabling transfer of power via the transformer when the first switch is on, and a reset time interval for enabling reset of the transformer when the reset switch is on. A maximum value of the on-time interval is pre-set to provide sufficient time for the reset. The reset switch is turned off when the PWM signal goes from a first level to a second level. A first delay period is set between time when the reset switch turns off and time when the first switch turns on.

Abstract: An isolated switching power supply device includes a main transformer having a primary coil on a primary circuit side and a secondary coil on a secondary circuit side. On the primary circuit side are disposed an input smoothing capacitor, a switching control circuit, a high-side driver, a low-side power switch, a high-side power switch, capacitors, and edge signal-generating circuits. A symmetrical control half bridge converter is thus provided. The secondary circuit side has a voltage clamping circuit including a clamp capacitor, a clamp switch and a diode.

Abstract: The configurations of a compensation device configured in a circuit having a synchronous rectifier (SR), a controller and a load, and a compensation method thereof are provided in the present invention. In the proposed circuit, the SR includes a first terminal, a first inductor electrically connected to the first terminal in series, a second terminal and a second inductor electrically connected to the second terminal in series, the controller is coupled to the first and the second inductors, and the device includes a voltage source having a positive terminal coupled to the controller and a negative terminal coupled to the second inductor and providing a compensation voltage to reduce or eliminate the influence of the first and the second inductors towards a voltage value across the first and the second terminals.

Abstract: The present invention provides an AC-DC converter and AC-DC conversion method for converting an AC input provided by a power transfer winding. The AC-DC converter includes a rectifying means for rectifying the AC input into a rectified output, and a control means for controlling the rectifying means based on a comparison between a reference signal and a voltage feedback signal, the voltage feedback signal being based on the rectified output.

Abstract: An isolated power converter comprising a transformer arranged in such a way that the mirrored primary voltage on the secondary side has a positive potential relative to ground, said converter comprising a derivating net arranged to cause the second transistor to conduct in dependence of the voltage across the secondary winding, the source of the second transistor being connected to the negative end of the secondary winding, the drain of a third transistor further being connected to the positive end of the secondary winding, a second capacitor and a second resistor being connected between the gate and the source of the third transistor, a third resistor connected between the second resistor and the drain of the second transistor, a third capacitor connected between the sources of the second and third transistors to provide a first output voltage on one terminal of the third capacitor and a second output voltage on the other terminal of the third capacitor.

Abstract: A synchronous rectifier circuit (DC-DC converter) includes a CR integration circuit and a discharge circuit. The CR integration circuit outputs a voltage that varies at delayed timing as compared with a voltage induced in a secondary-side main winding. The discharge circuit discharges a gate voltage of a rectifier transistor as a result of conduction of a discharge transistor in response to the output voltage from the CR integration circuit. According to such a configuration, the rectifier transistor is turned off earlier than the timing of switching of polarity of voltages induced in the secondary-side main winding and a secondary-side auxiliary winding in response to turn-on of a primary-side transistor.

Abstract: A switching power supply device has a synchronized rectifying element that turns on and off complementarily with a main oscillation element that is connected in series with an input power supply, and a parasitic diode that is connected to the two ends of the synchronized rectifying element in a direction enabling current supply toward a smoothing circuit. The device has a control circuit that generates a control pulse according to which a time delay is set for turning on the main oscillation element after a certain period of time elapses after the synchronized rectifying element is turned off, and that drives the main oscillation element and the synchronized rectifying element. An auxiliary rectification circuit has a series circuit formed by an auxiliary switch element and an auxiliary capacitor driven by the control circuit (PW2) and which is provided between the two ends of the parasitic diode.

Abstract: A driving circuit for an opto-coupler comprising a switched mode regulator configured to convert a first voltage to a second voltage, the switched mode regulator operable in accordance with a control signal (311) representative of the first voltage, and wherein the second voltage is used to drive the diode (304a) of the opto-coupler (304), in use.

Abstract: In order to further develop a circuit arrangement (100) as well as a method for generating at least one drive signal for at least one synchronous rectification switch of at least one flyback converter in such way that an improved and simpler thermal management can be combined with a significant cost reduction as well as with a higher efficiency, it is proposed to generate the drive signal for said synchronous rectification switch as a function of at least one oscillating signal controlling the synchronous rectification switch, of at least one constant delay time, of at least one variable delay time, and of at least one Boolean OR function.

Abstract: A control circuit, a control method, and a power supply device are provided. The control circuit includes an obtaining sub-circuit, adapted to obtain a voltage signal from a reverse surge current when the reverse surge current appears on a primary side of a switch power circuit of a synchronous rectification circuit; a maintaining sub-circuit, adapted to continuously output a first control signal in a preset first time period when the voltage signal is greater than a preset first voltage threshold; and a control sub-circuit, adapted to control and switch off switch tubes of the secondary side of the switch power circuit of the synchronous rectification circuit according to the first control signal. Thus, a reverse current surge of the switch power circuit of the synchronous rectification circuit can be effectively suppressed, and the safety of a switch power supply of the synchronous rectification circuit can be effectively protected.

Abstract: Provided is a resonance converting apparatus. The resonance converting apparatus preferably includes a resonant circuit, a bridge-type converter, and a synchronous rectification circuit. In which the resonant circuit has a transformer. The bridge-type converter connects with a primary side of the transformer, and operates open or close according to a switching signal. The synchronous rectification circuit further includes a pair of rectification transistors and driving circuits. The driving circuits correspondingly connect with channels to the rectification transistors, and respectively examine the current passing through the rectification transistors. A sensing signal is then generated. In accordance with the switching signal and the sensing signal, a driving signal is generated for driving the rectification transistor. Consequently the apparatus can raise the efficiency of the resonance converting apparatus.

Abstract: The present invention relates to a DC/DC converter (1) with primary side (11) consisting of a resonant converter, which DC/DC converter (1) comprises a first and a second transformer (T1, T2), connected in series on the primary side (11) and on the secondary side (12) of the DC/DC converter. The secondary side (12) comprises an autotransformer (Tcd) consisting of a first and a second winding (Tcda, Tcdb) connected to a common center tap (Tcdc), where the first winding (Tcda) of the autotransformer (Tcd) is connected to the secondary winding (T1b) of the first transformer (T1), forming a first output connection point (P1), the second winding (Tcdb) of the autotransformer (Tcd) is connected to the secondary winding (T2b) of the second transformer (T2), forming a second output connection point (P2), and the center tap (Tcdc) of the autotransformer (Tcd) is connected to the positive output (21) of the secondary side (12).

Abstract: The present invention relates to a DC/DC converter (1) with primary side (11) consisting of a resonant converter, which DC/DC converter (1) comprises a first and a second transformer (T1, T2), connected in series on the primary side (11) and on the secondary side (12) of the DC/DC converter. The secondary side (12) comprises an autotransformer (Tcd) consisting of a first and a second winding (Tcda, Tcdb) connected to a common center tap (Tcdc), where the first winding (Tcda) of the autotransformer (Tcd) is connected to the secondary winding (T1b) of the first transformer (T1), forming a first output connection point (P1), the second winding (Tcdb) of the autotransformer (Tcd) is connected to the secondary winding (T2b) of the second transformer (T2), forming a second output connection point (P2).

Abstract: Disclosed is a power converter including a switching circuit; a transformer having a primary winding connected to the switching circuit and a secondary winding; a main control circuit connected to the switching circuit for outputting a main control signal to manipulate the switching circuit; at least one synchronous rectifier connected to the secondary winding; at least one current transformer connected to the synchronous rectifier for outputting a detecting signal according to a current flowing through the synchronous rectifier; and at least one synchronous rectification control circuit connected to a control terminal of the synchronous rectifier, the current transformer, and a control terminal of the switching circuit for receiving the detecting signal and the main control signal for manipulating the synchronous rectifier.

Abstract: Provided is a bidirectional DC/DC converter which can control a boost voltage in a wide range. The DC/DC converter includes: three series circuits formed by a first to a sixth switch, each two of which are connected in series between a plus terminal and a minus terminal of a high voltage side; two transformers in which primary windings are connected in series and input terminals of the primary windings are connected to connection points of the switching elements; and a seventh to a tenth switch. The transformers have secondary windings, each of which is divided at the middle point. The middle points are connected to a minus terminal of a low voltage side. Respective terminals of the secondary windings are connected to a plus terminal of the low voltage side by the seventh to the tenth switches.

Abstract: The present invention discloses a secondary side protection method for a switching power converter, used to turn off a secondary side switch according to a secondary side voltage signal, wherein the secondary side voltage signal has falling edges corresponding to the start instants of secondary side discharge periods, and rising edges corresponding to the end instants of the secondary side discharge periods, the method comprising the steps of: measuring the time interval between two adjacent the rising edges repeatedly to derive discharge end cycle times; and generating a first turn-off signal to turn off the secondary side switch when the relative difference of two successive the discharge end cycle times exceeds a predetermined percentage. The present invention also provides a secondary side protection apparatus according to the method.

Abstract: Zero volt switching during a light load is performed in such a manner that through an ON/OFF control of switches provided for a full bridge circuit and the synchronous rectifier switches in a rectifier and smoothing circuit, a resonant peak voltage necessary for the zero voltage switching determined by the output current flowing to output terminals, a resonant inductor and a resonant capacitor capacitance is ensured so that an energy accumulated in the rectifier and smoothing circuit is returned to the full bridge circuit so as to act as equivalent as when the output current is increased and to increase the current flowing through the full bridge circuit.

Abstract: A system and method for bi-directional voltage conversion are disclosed. A charge current is received at a first voltage on a first force commutated synchronous rectifier, and the charge current is controlled by the first force commutated synchronous rectifier. An inductor is charged by the charge current, and a discharge current from the inductor is controlled by the second force commutated synchronous rectifier.

Abstract: A synchronous rectifier circuit and a multi-output power supply device using the same include a semiconductor switch to control a current flow of the synchronous rectifier circuit, and a switching controller to control the semiconductor switch according to a synchronous rectification control signal and an output control signal generated by feeding back the output voltage of the synchronous rectifier circuit. The synchronous rectifier circuit can control an output voltage, decrease power loss so as to increase the efficiency of the synchronous rectifier circuit, and decrease the cost of the synchronous rectifier circuit.

Abstract: An apparatus, system, and method are disclosed for efficiently providing bias voltages. A first switching regulator stage that includes an inductor receives an input voltage and provides as an output an intermediate regulated output voltage. A second switching regulator stage receives as input the intermediate regulated output voltage and outputs a regulated main output voltage. The second switching regulator stage includes at least one switch controller that provides one or more signals to one or more switches in the second switching regulator stage to regulate the main output voltage of the second regulator stage. A secondary bias module utilizes a secondary winding coupled with the inductor of the first regulator stage to provide a secondary bias output voltage to the switch controller of the second switching regulator stage. The secondary bias output voltage is referenced to the main output voltage of the second switching regulator stage.

Abstract: Particular embodiments generally relate to detecting an operating mode of a flyback converter. In one embodiment, a voltage of a flyback converter is measured. A waveform for the voltage includes a first rate of change when the flyback converter is in a first mode of operation and a second rate of change when the flyback converter is in a second mode of operation. The presence of the first rate of change or the second rate of change is detected based on the waveform. The first mode of operation or the second mode of operation is determined depending on whether the first rate of change or the second rate of change is detected.

Abstract: A synchronous rectifier circuit of a switching power converter is provided and includes first and second power transistors and first and second diodes connected to a transformer and an output of the power converter for rectifying. An arbiter circuit generates a lock signal to prevent the second power transistor from being turned on when the first power transistor is turned on. A controller generates a drive signal to control the first power transistor according to an on signal and an off signal. A phase-lock circuit generates the off signal according to the on signal. The on signal is enabled once the first diode is forward biased. The one signal enables the drive signal for turning on the first power transistor. The off signal disables the drive signal for turning off the first power transistor. The off signal is enabled before the disabling of the on signal.

Abstract: A resonant converter including a primary side switching stage having high- and low-side switches series connected at a switching node and controlled by a primary side controller; a transformer having a primary coil and a secondary coil, the secondary coil having at least one pair of portions series connected at a node, a resonant tank formed by series connecting the primary coil to the switching node with a first inductor and a first capacitor; at least one pair of first and second secondary side switches connected to the at least one pair of portions, respectively, the first and second secondary side switches of each pair being used for synchronous rectification; and a secondary side controller to control and drive the first and second secondary side switches of each pair by sensing voltage across each secondary side switch and determining a turn ON and turn OFF transition for the first and second secondary side switches in close proximity to a point in time when there is zero current through the secondary s

Abstract: A synchronous rectification control circuit assembly includes a first transformer, a reference voltage generator, a first PWM control signal generating circuit, a second PWM control signal generating circuit, a first synchronous rectification circuit, and a second synchronous rectification circuit. When the output voltage rises, the conduction time of the first synchronous rectification circuit and the second synchronous rectification circuit are relatively regulated to lower the output voltage, maintaining stability of the output voltage.

Abstract: The present invention discloses a smart driving method for a secondary synchronous rectifier of an isolated converter and its apparatus thereof. The apparatus comprises: a main circuit having a secondary synchronous rectifier Q1; a differentiation filter circuit, filtering the drain-source voltage Vds of the secondary synchronous rectifier, comprising a capacitor and at least one resistor connected in series and outputting a filtered voltage Vf from either between said capacitor and said at least one resistor or between said at least one resistor; a smart driver, receiving Vf and Vds and putting out a driving signal to the gate of the secondary synchronous rectifier. The control approach is fulfilled by comparing Vds to a reference voltage Vthr2 and comparing the absolute value of Vf to another reference voltage Vthr3. When Vds<Vthr2 and |Vf|>Vthr3, Q1 is turned on. When Vds>Vthr1, Q1 is turned off, where Vthr1 is a predetermined reference voltage.

Abstract: A control circuit, a control method, and a power supply device are provided. The control circuit includes an obtaining module, adapted to obtain a voltage signal from a reverse surge current when the reverse surge current appears on a primary side of a switch power circuit of a synchronous rectification circuit; a maintaining module, adapted to continuously output a first control signal in a preset first time period when the voltage signal is greater than a preset first voltage threshold; and a control module, adapted to control and switch off switch tubes of the secondary side of the switch power circuit of the synchronous rectification circuit according to the first control signal. Thus, a reverse current surge of the switch power circuit of the synchronous rectification circuit can be effectively suppressed, and the safety of a switch power supply of the synchronous rectification circuit can be effectively protected.

Abstract: A primary winding current controlled synchronous rectifying drive circuit including a current sampling circuit that detects a current signal in a primary winding of a transformer and forwards it to a signal shaping and reset circuit, and a current compensation signal circuit that compensates a magnetizing current in the primary winding of the transformer, wherein the signal shaping and reset circuit converts a sample of the current signal into a voltage signal and shapes it into a pulse signal, and then forwards the current signal to a logic control and power drive circuit that converts the pulse signal into one or more drive signal(s) through logic control, then the drive signal(s) are amplified to drive a corresponding synchronous rectifier.

Abstract: An synchronous rectifying apparatus or synchronous rectifying circuit of a soft switching power converter is provided to improve the efficiency. The integrated synchronous rectifying circuit includes: a power transistor connected from a transformer to the output of the power converter for rectifying; a controller having a latch circuit generates a drive signal to control the power transistor in response to a switching signal generated by a winding of the transformer in response to the switching of the transformer. The controller turns off the power transistor when the switching signal is lower than a low-threshold. The power transistor is turned on when the switching signal is higher than a high-threshold. Furthermore, a maximum-on-time circuit provided in the controller is applied to generate a maximum-on-time signal for limiting the maximum on time of the power transistor.

Abstract: In one embodiment, a control circuit for a series resonant switching power supply control system is configured to disable a power switch of secondary side of the system in response to a polarity reversal of the voltage across a primary side winding of the system.

Abstract: The configurations of a resonant converter system and a controlling method thereof are provided. The proposed resonant converter system includes a resonant converter receiving an input voltage for outputting an output voltage, a rectifying device having a first rectifying switch and a synchronous rectification control circuit coupled to the resonant converter and including a signal generation apparatus generating a weighted turn-off signal to turn off the first rectifying switch at a zero crossing point of a first current flowing through the first rectifying switch.

Abstract: In a DC/DC converter comprising a transformer (10) having a primary winding Np and at least first and second secondary windings Ns1 and Ns2; a main output path connecting the first secondary winding to a main output Vp and comprising a synchronous rectifier circuit, a first inductor L1, and a first capacitor C1; and an input path connecting a DC supply voltage Ve to the primary winding and including a switch circuit (12) controlled by a first pulse width modulator PWM1 to regulate the main output voltage by switching the current in the primary winding, there is provided an auxiliary output circuit connecting the second secondary winding to an auxiliary output Va and comprising an auxiliary rectifier path having a control switch M5, a free-wheel switch M6, a rectifier switch M3, a second inductor L2, and a second capacitor C2; and a second pulse width modulator PWM2 connected to the control switch M5 and to the free-wheel switch M6 to control a conduction interval of said switches in order to regulate the auxi

Abstract: The configuration of a synchronous rectification circuit and a controlling method thereof are provided. The proposed circuit includes a converter including a first switch and a first synchronous rectifier, and a burst mode controller including a logic process module performing one of functions of delaying one of a non-integer and at least one operating periods to generate a synchronous rectification driving signal of the first synchronous rectifier counting from a beginning of a first pulse of a driving signal of the first switch during a working time of a burst period, and turning off the synchronous rectification driving signal of the first synchronous rectifier by one of the non-integer operating period and the at least one operating period ahead of an ending of a last operating period of the driving signal of the first switch during the working time of the burst period.

Abstract: A power converter nearly losslessly delivers energy and recovers energy from capacitors associated with controlled rectifiers in a secondary winding circuit, each controlled rectifier having a parallel uncontrolled rectifier. First and second primary switches in series with first and second primary windings, respectively, are turned on for a fixed duty cycle, each for approximately one half of the switching cycle. Switched transition times are short relative to the on-state and off-state times of the controlled rectifiers. The control inputs to the controlled rectifiers are cross-coupled from opposite secondary transformer windings.

Abstract: A synchronous rectifier of a resonant switching power converter is provided to improve efficiency. The synchronous rectifier includes a power transistor and a diode connected to a transformer and an output of the resonant switching power converter for ratifications. A controller generates a drive signal to control the power transistor in response to an on signal and an off signal. A causal circuit is developed to generate the off signal in accordance with the on signal. The on signal is enabled once the diode is forward biased. The on signal is coupled to enable the drive signal for switching on the power transistor. The off signal is coupled to disable the drive signal for switching off the power transistor. The off signal is enabled before the on signal is disabled.

Abstract: A controller for a power converter, and method of operating the same. The controller improves power converter operating efficiency by regulating an internal power converter operating characteristic depending on a value of a power converter parameter measured after a manufacturing step, or an environmental parameter, preferably employing a table with entries dependent on the parameter value. The internal operating characteristic may be an internal bus voltage, a voltage level of a drive signal for a power switch, a number of paralleled power switches selectively enabled to conduct, or a basic switching frequency of the power converter. The controller may regulate an internal operating characteristic of the power converter using a functional relationship dependent on the parameter value. The environmental parameter may be received as a signal from an external source. The parameter measured after a manufacturing step may be a parameter measured from representative power converter(s).

Abstract: A synchronous rectifying circuit of soft switching power converter is provided to improve the efficiency. The integrated synchronous rectifier includes a power transistor connected from a transformer to the output of the power converter for rectifying. A controller having a latch circuit generates a drive signal to control the power transistor in response to a switching-current signal. A current transformer generates the switching-current signal in response to the switching current of the transformer. The controller turns off the power transistor when the switching-current signal is lower than a second threshold. The power transistor is turned on once the switching-current signal is higher than a first threshold. Furthermore, a pulse-width detection circuit generates a pulse signal coupled to disable the drive signal and turn off the power transistor.

Abstract: In a switching power-supply apparatus, a primary-side power converter circuit includes a half bridge system and a synchronous rectifier circuit is provided as a rectifier circuit of a secondary-side power converter circuit. An on time ratio of the on time of a first switching element to the on time of a second switching element is controlled so as to provide an operation mode in which energy is regenerated from the secondary side to the primary side when the load is light.

Abstract: A synchronous rectifying circuit is provided for power converter. An integrated synchronous rectifier has a rectifying terminal, a ground terminal a first input terminal and a second input terminal. The rectifying terminal is coupled to secondary side of a transformer. The ground terminal coupled to output of the power converter. A power transistor is connected between the rectifying terminal and the ground terminal. The first input terminal and the second input terminal are coupled to receive a pulse signal for turning on/off the power transistor. A pulse-signal generation circuit includes an input terminal coupled to receive the switching signal for switching the transformer of the power converter. A first output terminal and a second output terminal of the pulse-signal generation circuit generate the pulse signal. An isolation device is coupled between the first input terminal and the second input terminal, and the first output terminal and the second output terminal.

Abstract: A current controlled synchronous rectifying drive circuit including a current transducer ST having a primary winding connected in series with a synchronous rectifier SR and having a secondary winding to detect a current signal of a synchronous rectifier SR, a signal shaping and reset circuit connected to the secondary winding of the current transducer ST to convert the synchronous rectifier SR's current signal into a voltage signal and shapes it into a pulse signal, a push-pull power amplifying circuit having an input end connected to the signal shaping and reset circuit and an output end connected to a gate of the synchronous rectifier SR to amplify a drive signal generated by the signal shaping and reset circuit to drive the synchronous rectifier SR, and a drive self-bias drive circuit having an input end connected to the secondary winding of the current transducer ST and an output end connected to the push-pull power amplifying circuit to store energy from the current transducer ST to generate a voltage so

Abstract: A synchronous rectifier control device comprises a status detecting unit, an analog circuit, a first counter, a second counter and a signal process unit. The status detecting unit receives at least one reference signal and a detecting signal to generate a first synchronous control signal. The analog circuit generates a delay signal in accordance with the first synchronous control signal. The first counter receives a clock signal and generates a first counter signal in accordance with the first synchronous control signal, the clock signal, and the delay signal. The second counter receives the clock signal and generates a second counter signal in accordance with the first synchronous control signal, the clock signal, and the first counter signal. The signal process unit generates a second synchronous control signal in accordance with the first synchronous control signal and the second signal.

Abstract: In accordance with an embodiment of the present invention, a method of operating a switched power supply is disclosed. The method comprises determining a current load on a secondary side of a transformer by measuring a ratio between a secondary side current conduction time and a primary switching period of the power supply and comparing the current load with a predetermined threshold. A synchronous rectification (SR) MOSFET coupled to the secondary side of the transformer is disabled if the current load is less than the preset threshold.

Abstract: A fly-forward converter topology for a switched-mode power supply (SMPS) that may incorporate the advantages of both a forward converter and a flyback converter into a two-stage half-wave converter is provided. The fly-forward converter may be considered as a half-wave forward converter that has been modified with the addition of another secondary winding and a second rectifier, operating as a forward converter during the on period of the primary-side switch(es) and functioning as a flyback converter during the off period. Magnetizing energy stored in the core of the converter's transformer is not lost or recirculated in the primary, but may be transferred from the primary to the secondary. By transferring the transformer magnetizing energy to the secondary during the off period, the transformer core of the fly-forward converter may be reset without additional core resetting circuitry.

Abstract: A synchronous rectifying circuit of a resonant switching power converter is provided to improve the efficiency. The synchronous rectifying circuit includes a power transistor and a diode connected to a transformer and an output ground of the power converter for rectifying. A sense transistor is coupled to the power transistor for generating a mirror current correlated to a current of the power transistor. A controller generates a driving signal to control the power transistor in response to a switching-current signal. A current-sense device is coupled to the sense transistor for generating the switching-current signal in response to the mirror current. The controller enables the driving signal to turn on the power transistor once the diode is forwardly biased. The controller generates a reset signal to disable the driving signal and turn off the power transistor once the switching-current signal is lower than a threshold.

Abstract: A synchronous rectifying circuit is provided for offline power converter. A pulse signal generator is utilized to generate a pulse signal in response to a switching current of the power transformer. An isolation device is coupled to the pulse signal generator for transferring the pulse signal through an isolation barrier of the power transformer. A synchronous rectifier includes a power switch and a control circuit. The power switch is coupled between the secondary side of the power transformer and the output of the power converter for the rectifying. The control circuit is operated to receive the pulse signal for turning on/off the power switch. The pulse signal is generated to turn on the power switch once the switching current is higher than a threshold.

Abstract: A bi-directional switch for a power converter comprises first and second transistors (SW1, SW2) and a floating supply capacitor (C2) associated with the second transistor (SW2). The drive circuit and/or gate of the first transistor (SW1) is charged by the floating supply capacitor (C2) of the second transistor (SW2). The charging takes place at a predetermined moment in the switching cycle, and in particular at a moment in the switching cycle when the voltage across the bi-directional switch is substantially a minimum.