Abstract: In a controller (CC2) for controlling a synchronous rectification switch (S2), the controller (CC2) comprises a sensing circuit (SRL) for sensing an output (D2) of the synchronous rectification switch (S2) at an end of a blanking time to obtain a sense signal (Q), and a control signal generating circuit (AND1) for generating a control signal (G2) for the synchronous rectification switch (S2) in dependence on the sense signal (Q).

Abstract: A power converter includes at least one electric control switch, an electric current detecting and converting unit, a power controller, and a voltage detecting and controlling unit at the primary side; and a synchronous rectifying circuit, two MOSFETs, and an oscillating loop. During the actual operation, electric current detecting and converting unit outputs an AC voltage signal to the power controller and outputs a DC voltage signal to the voltage detecting and controlling unit, and then voltage detecting and controlling unit compares with a reference voltage to turn off the synchronous rectifying circuit at the no-load mode and to rectify via a body diodes of the MOSFETs. Accordingly, the power converter can reduce the power wastage at the no-load mode to be energy-saving.

Abstract: A power converter includes at least one electric control switch, an electric current detecting and converting unit, a power controller, and a voltage detecting and controlling unit at the primary side; and a synchronous rectifying circuit, two MOSFETs, and an oscillating loop. During the actual operation, electric current detecting and converting unit outputs an AC voltage signal to the power controller and outputs a DC voltage signal to the voltage detecting and controlling unit, and then voltage detecting and controlling unit compares with a reference voltage to turn off the synchronous rectifying circuit at the no-load mode and to rectify via a body diodes of the MOSFETs. Accordingly, the power converter can reduce the power wastage at the no-load mode to be energy-saving.

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: The present invention relates to a forward converter with self-driven synchronous rectifiers, which utilizes a secondary driving winding and a secondary driving circuit to drive the synchronous rectifiers in the secondary power loop. The secondary driving circuit, which is composed of a level shifter and a signal distributor, can shift the voltage waveform across the secondary driving winding by a predetermined level and distribute proper driving signals to the synchronous rectifiers to reduce the rectifier conduction loss. Specially, the channel of the freewheeling synchronous rectifier still can be turned on during the dead interval to further reduce the body diode conduction loss.

Abstract: A control circuit for soft switching and synchronous rectifying is provided for power converter. A switching-signal circuit is used for generating drive signals and a pulse signal in response to a leading edge and a trailing edge of a switching signal. The switching signal is developed for regulating the power converter. Drive signals are coupled to switch the power transformer. A propagation delay is developed between drive signals to achieve soft switching of the power converter. An isolation device is coupled to transfer the pulse signal from a primary side of a power transformer to a secondary side of the power transformer. A controller of the integrated synchronous rectifier is coupled to the secondary side of the power transformer for the rectifying operation. The controller is operated to receive the pulse signal for switching on/off the power transistor. The pulse signal is to set or reset a latch circuit of the controller for controlling the power transistor.

Abstract: A buck-boost PFC converter is provided and includes an inductor, first and second transistors, a first diode, and a control circuit. The inductor has a first terminal and a second terminal. The first transistor is coupled to a positive-power rail and the first terminal of the inductor. The second transistor is coupled to the second terminal of the inductor and a negative-power rail. The first diode is connected from the second terminal of the inductor to an output of the buck-boost PFC converter. The control circuit generates a first signal and a second signal coupled to control the first transistor and the second transistor respectively. The first signal is utilized to turn on the first transistor for conducting the positive-power rail to the inductor. The second signal is utilized to turn on the second transistor for conducting the inductor to the negative-power rail.

Abstract: The present invention discloses a forward converter with secondary side post-regulation and zero voltage switching, where the primary side power loop may adopt a single or a dual transistor structure, driven by a primary side driving circuit with a constant duty ratio so that the voltage waveform across the secondary side power winding has a constant pulse width; the secondary side power loop uses a controllable switch, a magnetic amplifier (MA) or an N channel metal oxide semiconductor field transistor (NMOS), to blank the leading edge of the voltage waveform across the secondary side power winding, regulate the output voltage, and achieve zero voltage switching of primary side switch transistors.

Abstract: A switched mode power converter is provided which includes a transformer (2) having a primary winding (2a) and at least one secondary winding (2b); a primary side active switch device (S1) coupled to the primary winding for selectively applying an input voltage to the primary winding; and a secondary side rectifier circuit including an output filter (6, 12) coupled to the at least one secondary winding (2), and first and second active switch devices (16, 14) coupled between the at least one secondary winding (2b) and the output filter. The switch devices are arranged such that each one is operable independently of the other to block current between the at least one secondary winding and the output filter in an opposite direction to the other. This facilitates better regulation of the converter and avoids the occurrence of voltage spikes encountered in existing configurations.

Abstract: A power supply module to power the control circuit of a switching mode power supply is provided. Based on the determination of whether the switching mode power supply is under a light or open load condition, the power supply module can dynamically provide the power to the control circuit of the switching mode power supply. Therefore, the performance of the power supply can be increased and the power loss can be decreased when the switching mode power supply is under a light or open load.

Abstract: The subject invention reveals a new coupled inductor boost converter which achieves zero voltage turn on switching for all four circuit switches. The coupled inductor of the circuit is fully clamped and thereby achieves excellent noise performance with neither snubbers nor clamps. The new coupled inductor boost converter is outstanding for isolated high voltage applications because the voltage stress of the secondary switches does not exceed the output voltage, it requires only one magnetic circuit element, and the average voltage stress of the secondary winding is equal to or less than half the output voltage.

Abstract: Disclosed are a synchronous rectifier control device and a forward synchronous rectifier circuit. The synchronous rectifier control device is coupled with the secondary side of the forward synchronous rectifier circuit, comprising a condition detecting unit, a reference time circuit and a synchronous signal generator. The condition detecting unit receives at least one reference signal and a detecting signal in response to the condition of the secondary side of the forward synchronous rectifier circuit, and accordingly generates a first synchronous control signal. The reference time circuit is coupled with the condition detecting unit, and generates a reference time signal in response to the first synchronous control signal. The synchronous signal generator generates a second synchronous control signal in response to the first synchronous control signal and the reference time signal.

Abstract: An insulated transfer device with particular topology, comprising on the primary, a switched-mode voltage step-up circuit, with a step-up inductance (LB) and an active buffer stage (DT, MT, CT) supplying a peak voltage greater than the peak voltage supplied by the input voltage source (vE) and two pairs of controlled switches controlling the application of the voltage supplied by the switched-mode voltage step-up circuit, to the terminals (Ep1, Ep2) of the primary winding and to the secondary, a full-wave rectifier with diodes (Ds1, Ds2) and controlled switches (Ms1, Ms2). On the primary, the voltage at the terminals of the capacitor CT of the active buffer stage used to apply a controlled AC voltage between the terminals Ep1 and Ep2 is regulated by controlling the time for which the controlled switches of the pairs are simultaneously in the closed state. On the secondary, VS is regulated by controlling the time for which the secondary switches are simultaneously in the closed state.

Abstract: A secondary circuit for a DC/DC converter, the secondary circuit having a main outlet and an auxiliary outlet, the secondary circuit comprising a main automatically controlled synchronous rectifier circuit receiving a voltage from the secondary winding of a transformer having an intermediate tap and delivering firstly a fullwave first rectified voltage for the main outlet and secondly a halfwave second rectified voltage, and an auxiliary synchronous rectifier circuit controlled by a synchronous post regulation control circuit receiving the halfwave second rectified voltage V2 and delivering a halfwave third rectified voltage for the auxiliary outlet.

Abstract: A synchronous rectifier type SRC for operating in an intermittence mode, which includes: an input power for supplying an input DC voltage; an input-side switching unit; a transformer with a primary winding and a secondary winding; an output-side switching unit for switching; and a gate driving circuit for detecting. According to the synchronous rectifier type SRC, a no-load characteristic can be controlled with an easy scheme and a simple construction. In addition, a simple resistor is added, and thus dead time can be generated. Consequently, it is possible to simply reduce switching loss that may occur in zero voltage switching.

Abstract: The present invention provides a transient suppression circuit for use with a rectifier coupled to a transformer. In one embodiment, the transient suppression circuit includes a triggering section configured to provide a timing signal corresponding to a dead time of the rectifier. Additionally, the transient suppression circuit also includes a biasing section coupled to the triggering section and configured to apply a reverse bias voltage to the rectifier based on the timing signal.

Abstract: An offline synchronous switching regulator is proposed for improving the efficiency thereof. Switches are coupled to switch a transformer and generate a switching signal at a secondary side of the transformer. A switching circuit is coupled to an output of the regulator to generate pulse signals in response to the switching signal and a feedback signal. Pulse signals are utilized to control a synchronous switch for rectifying and regulating the regulator. The synchronous switch includes a power-switch set and a control circuit. The control circuit receives pulse signals for turning on/off the power-switch set. The power-switch set is connected in between the transformer and the output of the regulator. A flyback switch freewheels an inductor current and can be turned on in response to the off state of the power-switch set whose on-time is correlated to the on-time of the power-switch set.

Abstract: A synchronous regulation circuit is provided to improve the efficiency for an offline power converter. A secondary-side switching circuit is coupled to the output of the power converter to generate a synchronous signal and a pulse signal in response to an oscillation signal and a feedback signal. An isolation device transfers the synchronous signal from the secondary side to the primary side of the power converter. A primary-side switching circuit further receives the synchronous signal to generate a switching signal for soft switching a transformer. The pulse signal is utilized to control a synchronous switch for rectifying and regulating the power converter. The synchronous switch includes a power switch and a control circuit. The control circuit receives the pulse signal for turning on/off the power switch. The power switch is connected in between the transformer and the output of the power converter.

Abstract: The present invention discloses a half-bridge LLC resonant converter with self-driven synchronous rectifiers, which utilizes a primary IC controller and a gate driver to drive the secondary synchronous rectifiers. In correspondence with the gate drive output voltages of the primary IC controller to the primary switch transistors, the gate driver for the secondary synchronous rectifiers comprises a differential transformer if the primary IC controller outputs two ground-referenced gate drive voltages, which cannot directly drive the primary switch transistors but can be imposed on the differential transformer; or comprises a DC shifter, a DC restorer and a differential transformer if the primary IC controller outputs two gate-source voltages, which can directly drive the primary switch transistors but cannot be imposed on the differential transformer. The drive voltages of the primary switch transistors are unipolar; however the drive voltage of the secondary synchronous rectifiers can be bipolar or unipolar.

Abstract: Embodiments of the present invention relate to a method and device for regulating a series resonant inverter with controlled rectification. It also relates to a resonant inverter equipped with such a device. The synchronous series resonant inverter includes a primary winding having across its terminals a periodic voltage V(t) of period T, this primary winding being coupled to at least one secondary winding providing the output voltage Vs. The establishment of the current IT(t) in the secondary winding is controlled within the period T. The output voltage Vs is regulated as a function of the phase shift angle ? between the zero crossing of the voltage V(t) across the terminals of the primary winding and the instant of establishment of the current IT(t) in the secondary winding. Embodiments include the production of isolated switched power supplies having a high level of integration, operating at a switching frequency of several megahertz.

Abstract: Disclosed is a flyback converter with a synchronous rectifier, in which the synchronous rectifier includes a synchronous switch, a current transformer connected in series between a drain terminal of the synchronous switch and an output terminal, and a secondary synchronous rectification driver connected to the gate terminal of the synchronous switch. Furthermore, a shunt resistor is connected in parallel with the current transformer for providing a current bypass path for a secondary current flowing through the synchronous switch and the current transformer, and thereby reducing the current flowing through the current transformer. Thus, the overall efficiency of the flyback converter can be enhanced and the life of the current transformer can be prolonged.

Abstract: A synchronous rectifying circuit is provided for flyback power converter. A pulse generator is utilized to generate a pulse signal in response to a leading edge and a trailing edge of a switching signal. The switching signal is used for switching the transformer of the power converter. An isolation device such as pulse transformer or small capacitors is coupled to the pulse generator for transferring the pulse signal through an isolation barrier of a transformer. A synchronous rectifier includes a power switch and a control circuit. The power switch is connected in between the secondary side of the transformer and the output of the power converter for the rectifying operation. The control circuit having a latch is operated to receive the pulse signal for controlling the power switch.

Abstract: The control apparatus for controlling a voltage transforming apparatus having a transformer, power switching elements disposed in a primary side, and synchronous-rectifying switching elements disposed in a secondary side includes a judging circuit making a judgment as to whether or not an output current of the voltage transforming apparatus is smaller than a specified current on the basis of a primary-side current of the transformer and an inhibition circuit inhibiting the synchronous-rectifying switching elements from performing their synchronous-rectifying control operation when the judging circuit judges that the output current is smaller than the specified current. The judging circuit makes the judgment on the basis of the primary-side current flowing through the primary coil of the transformer immediately before the power switching elements are turned off.

Abstract: A DC power source device is provided which comprises conduction detectors 17, 18 for producing detection signals VP1, VP2 during the detective period of rectification MOS-FETs 15, 16 and timer circuits 19, 20 connected to polarity detectors 17, 18. Timer circuits 19, 20 count output time of detection signal VP1, VP2 from polarity detectors 17, 18 until electric current through one of rectification MOS-FETs 15, 16 comes to zero, and turns the other of rectification MOS-FETs 15, 16 off immediately before termination of the counted time so that timer circuits 19, 20 can reliably turn rectification MOS-FETs 15, 16 off during the conductive period of forward current flow for efficient synchronous rectification.

Abstract: A current resonant DC-DC converter of multi-output type is provided which comprises an output-regulatory MOS-FET 40 connected between a secondary winding 5c of a transformer 5 and a smoothing capacitor 16 in a second rectifying smoother 17, and an output control circuit 41 for controlling the on-off operation of output-regulatory MOS-FET 40 based on voltage VO2 from smoothing capacitor 16 in second rectifying smoother 17. By turning the on-off operation of output-regulatory MOS-FET 40 in synchronization with switching frequency of first or second MOS-FETs 1, 2, an ideal cross regulation among respective DC outputs can be obtained, providing the inexpensive converter with simple circuit alteration capable of producing highly stable DC outputs with high power conversion efficiency, high accuracy and less power conversion loss.

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: A synchronous regulation circuit is provided. A secondary-side switching circuit is coupled to the output of the power converter to generate a synchronous signal and a pulse signal in response to an oscillation signal and a feedback signal. An isolation device transfers the synchronous signal from the secondary side to the primary side of the power converter. A primary-side switching circuit receives the synchronous signal to generate a switching signal for soft switching a transformer. The pulse signal is utilized to control a synchronous switch for rectifying and regulating the power converter. The synchronous switch includes a power switch and a control circuit. The control circuit receives the pulse signal for turning on or off the power switch. The power switch is connected between the transformer and the output of the power converter. A flyback switch is operated as a synchronous rectifier to freewheel the inductor current of the power converter.

Abstract: A self-driven synchronous DC-DC converter (100) includes an input circuit (101) having a switching device (110) for selectively generating a pulsed DC input voltage responsive to an input switch control signal, the pulsed DC input voltage being one of a plurality of DC voltage pulses; an output circuit (113) coupled to the input circuit (101) and including an active device (114) having device input, device output, and device control nodes, the device control node responsive to a control voltage for selectively varying the conductivity between the device input node and the device output node; and a control circuit (115) coupled to the device control node and configured for generating the control voltage responsive to the pulsed DC input voltage. In the converter (100), the control voltage is synchronized with the pulsed DC input voltage and varies non-linearly during an interval between the DC voltage pulses for selectively reducing the conductivity in accordance with a non-linear function.

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

Abstract: A synchronous rectifying circuit is provided for power converter. A pulse signal generator is utilized to generate a pulse signal in response to the leading edge and the trailing edge of a switching signal. The switching signal is used for switching the transformer of the power converter. An isolation device such as pulse transformer or small capacitors is coupled to the pulse signal generator for transferring the pulse signal through an isolation barrier of a transformer. A synchronous rectifier includes a power switch and a control circuit. The power switch is equipped in between the secondary side of the transformer and the output of the power converter for the rectifying. The control circuit having a latch is operated to receive the pulse signal for turning on/off the power switch.

Abstract: A switching power source device for supplying power to a load includes a series resonant circuit, a plurality of main switch elements or main switch element groups for switching a current. path of the series resonant circuit, a transformer for inducing a secondary current from the series resonant circuit, a plurality of synchronous rectification switch elements for rectifying the secondary current, a maximum on width control circuit for ordering a start and a completion of a maximum on width to the synchronous rectification switch element in synchronization with a timing of turning on the main switch elements Or the main switch element groups, and a synchronous control circuit. The circuit controls an on period of the synchronous rectification switch element so as to turn on the synchronous rectification switch element in synchronization with a particular timing, and turn off in synchronization with another timing.

Abstract: An AC to DC converter circuit includes a main circuit including a first circuit and a second circuit connected to an AC power supply in parallel to each other, the first circuit including diodes and a switching device, the second circuit including diodes and a switching device. The switching devices are controlled to be ON and OFF corresponding to the input voltage polarity discriminated with an input voltage polarity discriminator such that two DC outputs are obtained from one AC power supply. The AC to DC converter circuit reduces the semiconductor devices, through which a current flows, facilitates reducing the losses caused therein, improving the conversion efficiency thereof, and reducing the size, weight and manufacturing costs of the cooling means thereof.

Abstract: An apparatus for synchronous rectifying of a soft switching power converter is provided. An integrated synchronous rectifier includes a power transistor coupled between a transformer and the output of the soft switching power converter, and a controller receiving a pulse signal to switch on/off the power transistor. A switching control circuit generates the pulse signal in response to a current signal, and generates drive signals to switch the transformer in response to a switching signal. An isolation device is coupled to transfer the pulse signal between the switching control circuit and the integrated synchronous rectifier. The switching signal is used for regulating the power converter and the current signal is correlated to the switching current of the transformer.

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 multi-output dual polarity inductive boost converter includes an inductor, a first output node, a second output node, and a switching network, the switching network configured to provide the following modes of circuit operation: a first mode where the positive electrode of the inductor is connected to an input voltage and the negative electrode of the inductor is connected to ground; 2) a second mode the negative electrode of the inductor is connected to ground and the positive electrode of the inductor is connected in sequence to one or more of the fourth and fifth output nodes; and 3) a third mode where the positive electrode of the inductor is connected to the input voltage and the negative electrode of the inductor is connected in sequence to one or more of the first, second and third output nodes.

Abstract: Circuit and method for controlling a synchronous power converter in discontinuous conduction mode with increased efficiency is disclosed. Circuitry is provided outputting gating signals to a high side driver and a synchronous rectifier responsive to a pulse width modulated input signal, an inhibit circuit for inhibiting the gating signal to the synchronous rectifier upon detection of a zero crossing condition; a comparator receiving a measured circuit value from the synchronous converter and a reference value and outputting a zero crossing condition; and a duty cycle observer circuit for determining the average duty cycle of the pulse width modulated input signal and for varying the reference value. A method is disclosed determining if the average duty cycle in the pulse width modulated input signal is increasing in response to varying a reference value, and inhibiting a synchronous rectifier control signal when the comparator indicates a zero crossing condition.

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: According to an exemplary embodiment a method of operating a resonant power supply comprises controlling the resonant power supply in a discontinuous way. According to an exemplary embodiment a resonant power supply comprises a first switching element, and at least one energy storing element, wherein the resonant power supply is adapted to be controlled in a discontinuous way.

Abstract: An AC/DC intermediate-circuit converter has a very wide AC input voltage range with a ZVS three-level DC/DC resonant converter with an LLC series-resonant circuit. Two intermediate-circuit capacitors are connected in series between DC intermediate-circuit connections with their common connection point forming a DC intermediate-circuit centre connection (5). The DC intermediate-circuit connections are connected to the DC connections of a rectifier whose AC input connections have an AC input voltage applied thereto. A range changeover switch is arranged between an AC input connection and the DC intermediate-circuit centre connection. The range changeover switch is closed in a lower AC input voltage range, when the ZVS three-level DC/DC resonant converter is operated on the basis of a “two-level operating mode” modulation strategy, such that the LLC series-resonant circuit has the full DC input voltage present between the DC intermediate-circuit connections applied to it.

Abstract: A power converter apparatus for receiving an input voltage and produces an output voltage by converting includes a switching-type voltage converting circuit circuit and a voltage level tuning circuit. The switching-type voltage converting circuit circuit includes an inductor, a switch and a synchronous rectifier, wherein the switch is for disabling/enabling the energy-storing operation conducted by the inductor. The synchronous rectifier produces the output voltage by using the stored electrical energy during the above-mentioned energy-storing operation. Besides, the voltage level tuning circuit is across coupled onto the switch for reducing the voltage difference between the two terminals of the switch.

Abstract: A rectification switch control switch element (Q7) is provided between a gate and a source of a rectification switch element (Q2). The rectification switch control switch element (Q7) is turned ON in response to a signal on a secondary side of a pulse transformer (T2) at a turn OFF timing of a main switch element (Q1) to forcedly turn OFF the rectification switch element (Q2). As a result, the rectification switch element (Q2) can be turned OFF in synchronism with an OFF of the main switch element at a time of a backflow. With use of a free resonance between a capacitance between a gate and a source of the rectification switch element (Q2) and a commutation switch element (Q3) and a choke coil (L2), an excitation state of the choke coil (L2) can be reset. Then, it is possible to stabilize a detection voltage of a tertiary rectification smoothing circuit (22) which uses a tertiary winding (N13) of a transformer (T1), thus stabilizing control of the circuit functions.

Abstract: Methods for selecting between the two modes (states) of operation, continuous conduction and discontinuous conduction, are disclosed. Systems that are capable of selecting the operating mode and operating in the continuous conduction mode or the discontinuous conduction mode are also disclosed.

Abstract: Disclosed a switching power source apparatus including: a transformer including a primary winding and a secondary winding; a switching element to intermittently apply a voltage to the primary winding by an on-off operation; and a synchronous rectifying element to rectify a current in the secondary winding, wherein the switching power source apparatus is a flyback system switching power source apparatus to receive input of electric power from a primary winding side to perform voltage output to a secondary wiring side, and the switching power source apparatus further comprises a load detection circuit to compare an output voltage to be output onto the secondary winding side with a voltage at a node between the synchronous rectifying element and the transformer by adding predetermined weighting to the voltages to be compared so as to generate a signal indicating a magnitude of an output load.

Abstract: A primary-side switching circuit generates switching signals for switching a transformer. A secondary-side switching circuit is coupled to an output of the power converter to generate pulse signals in response to the switching signals and an output voltage of the power converter. Pulse signals are generated to rectify and regulate the power converter. A synchronous switch includes a power-switch set and a control circuit. The control circuit receives the pulse signals via capacitors for turning on/off the power-switch set. The power-switch set is connected in between the transformer and the output of the power converter. Furthermore, a flyback switch is operated to freewheel the inductor current of the power converter. The flyback switch is turned on in response to the off state of the power-switch set. The on time of the flyback switch is programmable and correlated to the on time of the power-switch set.

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 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: Methods and apparatus for regulating a synchronous rectifier DC-to-DC converter by adjusting one or more existing synchronous rectifiers in the converter are provided. By regulating an existing synchronous rectifier, the rectifier may function as a modulator for post regulation over a limited range of output voltages suitable for load regulation, without introducing an additional conversion stage for post regulation, which typically decreases efficiency and power density. Independent post regulation of an existing synchronous rectifier may improve the load regulation, reduce output voltage ripple, and improve the transient response of the converter. By operating independently from the main control loop, post regulation may most likely avoid the limitations of the main control loop, such as limited gain bandwidth and a relatively slow transient response. Such post regulation may be added to isolated or non-isolated switched-mode power supplies, such as forward or buck converters.

Abstract: A synchronous rectifier DC/DC converter is provided. The synchronous rectifier DC/DC converter includes a power transformer, a first diode, a first MOSFET, and a first controller. The power transformer includes a core, a primary winding, a secondary winding, and a sense winding. The primary winding is wrapped around the core and receives an input voltage of the synchronous rectifier DC/DC converter. The secondary winding is wrapped around the core and provides the energy of an output current of the synchronous rectifier DC/DC converter. The sense winding is wrapped around the core and provides a sense signal. The first diode is coupled to the secondary winding for rectifying the output current. The first MOSFET is coupled in parallel with the first diode. The first controller is coupled to the sense winding and the first MOSFET for turning on and turning off the first MOSFET according to the sense signal.

Abstract: A resonance converter and a synchronous rectification driving method thereof are provided. The resonance converter includes a switch circuit having at least two first switches, a resonance circuit having a resonance frequency, a transformer, and a full-wave rectification circuit having two second switches each of which has a drain and a source and generates a channel resistance voltage when a current flows through the drain and the source. The synchronous rectification driving method includes steps as follow.

Abstract: A synchronous rectifying apparatus suitable for use in a forward synchronous converter having a transforming unit with a primary and secondary side, and a first and second rectifying switches coupled to the secondary side is provided. The synchronous rectifying apparatus has a condition detecting unit and a synchronous rectifying controller. The condition detecting unit; coupled to the secondary side of the transforming unit, for detecting if the operation condition of the forward synchronous converter is at boundary between discontinuous current mode and continuous current mode or under discontinuous current mode based on the rising slope of the secondary side voltage of the transforming unit. If so, the condition detecting unit outputs a reset signal. The synchronous rectifying controller, coupled to the secondary side of the transforming unit and the condition detecting unit, to turn off the second rectifying switch for a predetermined time period in response to the reset signal.