An amplifier circuit acting as a line driver in a line between a central station and field devices connected thereto comprising: a DC/DC converter integrated in the circuit as a power stage comprising a DC/pulse converter with two electrically isolated switching stages; a logic block preceding the converter, generating control signals for the switches from a PWM signal and feeding them into the converter in an electrically isolated manner using drivers; a priority block generating the PWM signal; a first and a second controller. The priority block forwards output from the first or second controller. The first controller generates a fault signal based on a voltage limit and an output voltage fed back within the amplifier circuit via a feedback path. The second controller generates a fault signal based on a current limit and the output current. The central station defines the current limit and the voltage limit.

A method to control a synchronous rectifier (SR) switch in a switching power supply circuit having an energy storage component coupled to the SR switch, the method is: generating a turning-ON control signal by comparing a drain-source sensing voltage of the SR switch with a turn ON threshold voltage; limiting an ON-time of the SR switch at least not less than a minimum on-time when the turning-ON control signal is asserted and an indicium signal having a first level indicating a fast mode; and removing the minimum on-time limitation to the SR switch and turning OFF the SR switch responsive to the drain-source sensing voltage of the SR switch exceeding a turn OFF threshold voltage when the turning-ON control signal is asserted and the indicium signal having a second level indicating a slow mode.

The present application provides a synchronous rectification circuit, which adopts a multiplexer that selectively inputs a first reference signal or a second reference signal to a comparator by coupling the first and second reference signal. A comparing signal is generated to a switch element by comparing a switch input signal. Hereby, the switch element is under control for synchronous rectification.

A synchronized rectification control method for use in a flyback converter is provided. The flyback converter includes a transformer including a secondary winding, a synchronous rectifier switch and a synchronous rectifier controller. The synchronous rectifier switch is coupled to the secondary winding and the synchronous rectifier controller, and is used to output a voltage difference signal and receive a control voltage. The method includes the synchronous rectifier controller detecting a rapid falling edge of the voltage difference signal to generate a rapid falling edge signal, generating an envelope signal according to the voltage difference signal, generating a time length control signal according to the voltage difference signal and the envelope signal, generating a blanking time signal according to the voltage difference signal and the time length control signal, and performing a logic operation on the blanking time signal and the rapid falling edge signal to generate the control voltage.

A control circuit comprising an output controller coupled to an output side of a power converter. The output controller comprises a switch control signal generator to receive a feedback signal representative of an output of the power controller and to communicate a control signal to an input controller coupled to an input side to control a turn ON of a power switch. The control signal is generated in response to the feedback signal and is communicated in response to an enable signal. The output controller comprises an extremum locator to generate the enable signal in response to a winding signal representative of an instantaneous voltage on an output terminal of an energy transfer element and the extremum locator enables the switch control signal generator such that the transition of the power switch from the OFF state to the ON state occurs substantially when the winding signal reaches an extremum.

Disclosed herein is an improved flyback converter that separates the magnetic components of the converter into a transformer and a separate, discrete energy storage inductor. This arrangement can improve the operating efficiency of the converter by reducing the commutation losses as compared to a conventional flyback converter. The magnetic components may be constructed on separate magnetic cores or may be constructed on magnetic cores having at least one common element, thereby allowing for at least partial magnetic flux cancellation in a portion of the core, reducing core losses.

A flyback converter with secondary-side control includes a secondary-side controller configured to emulate a primary-winding current. Based upon the emulated primary-winding current, the secondary-side controller signals a primary-side controller through at least one isolation capacitor to switch off a power switch transistor.

The present disclosure provides a power conversion circuit including positive and negative input terminals, a clamping branch circuit, a first primary switch, a transformer, a rectifier circuit, a resonant inductor, a resonant capacitor, and positive and negative output terminals. The clamping branch circuit includes a clamping capacitor and a second primary switch serially connected between the first and second terminals thereof. The first terminal is coupled to the positive input terminal. The first primary switch is connected between the second terminal and the negative input terminal. The primary winding of the transformer is connected to the clamping branch circuit in parallel. The rectifier circuit includes first and second bridge arms connected in parallel. Connection terminals in the first and second bridge arms are coupled to two terminals of the secondary winding of the transformer correspondingly. The first and second bridge arms are coupled between the positive and negative output terminals.

An LLC resonance converter includes a switching circuit, a resonance tank, a transformer, a synchronous rectification unit, and a control unit. The switching circuit includes a first switch controlled by a first control signal and a second switch controlled by a second control signal. The synchronous rectification unit includes a first synchronous rectification switch controlled by a first rectification control signal and a second synchronous rectification switch controlled by a second rectification control signal. The first control signal, the first rectification control signal, the second control signal, and the second rectification control signal include an operation frequency and a phase shift amount. When the operating frequency is lower to a specific value or the phase shift amount is higher to a specific value, the control unit fixes one of them to extend a hold-up time of the LLC resonance converter.

A synchronous rectifier control apparatus includes a continuous conduction mode detection circuit configured to receive a voltage across a synchronous rectifier switch and determine whether the synchronous rectifier switch operates in a continuous conduction mode based on a rising slope of the voltage across the synchronous rectifier switch, a turn-off timer control circuit configured to measure a conduction time of the synchronous rectifier switch and turn off the synchronous rectifier switch after the conduction time of the synchronous rectifier switch in a current cycle is substantially equal to the conduction time measured in an immediately previous cycle, and a drive voltage control circuit configured to reduce a gate drive voltage of the synchronous rectifier switch after the conduction time of the synchronous rectifier switch in the current cycle is substantially equal to the conduction time measured in the immediately previous cycle multiplied by a predetermined percentage.