A circuit includes a first rectifier having a first rectifier input and a first rectifier output. The circuit also includes a bridge circuit and a second rectifier. The bridge circuit is coupled to the first rectifier output. The bridge circuit has first, second, third, and fourth terminals. The first and second terminals are coupled to the first rectifier output, and the third and fourth terminals are adapted to be coupled to a primary winding of a transformer. The second rectifier has a second rectifier input and a second rectifier output. The second rectifier input is adapted to be coupled to a secondary winding of the transformer.

A power supply circuit configured to generate an output voltage at a target level from an input voltage thereof. The power supply circuit includes a wiring configured to receive the input voltage, a variable resistor provided between the wiring and a predetermined node, a voltage generation circuit configured to apply a voltage at a predetermined level to the predetermined node based on a current from the variable resistor, an output circuit configured to output the output voltage at the target level, in response to the voltage at the predetermined level being applied to the predetermined node, and an adjustment circuit configured to increase a resistance value of the variable resistor in response to a predetermined time period having elapsed since starting of generation of the output voltage.

Techniques and apparatus for driving a transistor gate of a switched-mode power supply (SMPS) circuit. One example gate driver for a switching transistor of an SMPS circuit generally includes a first power supply rail; a reference rail; an output node for coupling to a control input of the switching transistor; a floating supply node; a pulldown transistor having a drain coupled to the output node of the gate driver and having a source coupled to the reference rail; and a pulldown logic buffer having a first power supply input coupled to the floating supply node, having a second power supply input coupled to the reference rail, and having an output coupled to a gate of the pulldown transistor. The floating supply node is configured to selectively receive power from the first power supply rail and the output node of the gate driver.

To provide a controller for power conversion circuit which can maintain the detection value of second voltage at the target value of second voltage without depending on feedback control, when the first voltage is varied. A controller for power conversion circuit changes a control value by feedback control so that the detection value of second voltage approaches a target value of second voltage; calculates a control value for control, by correcting the control value based on the detection value of first voltage so as to correct, in feedforward manner, a change of the control value due to a change of the first voltage if correction of the control value is not performed; and controls on/off the switching device based on the control value for control.

A switched-mode power supply includes an input, an output, and a transformer including primary and secondary windings. The power supply also includes a synchronous rectifier coupled to selectively conduct current through the secondary winding of the transformer. The synchronous rectifier includes a source, a gate and a drain terminal. The power supply further includes a controller having a supply voltage terminal and a gate terminal to supply a control signal to the gate of the synchronous rectifier, and a circuit coupled between the supply voltage terminal of the controller and at least one of the gate terminal of the controller and the drain terminal of the synchronous rectifier to supply power from the gate terminal of the controller or the drain terminal of the synchronous rectifier to the supply voltage terminal of the controller. Methods of supplying power in switched-mode power supplies are also disclosed.

An embodiment provides a circuit including a transformer having a primary winding coupled to an input port configured to receive an input voltage and a secondary winding configured to provide an output voltage at an output port, controller circuitry configured to switch on and off a current through the primary winding so that energy is transferred to the secondary winding while switching and supply circuitry connected to the controller circuitry, wherein the supply circuitry is coupled to an auxiliary winding of the transformer and configured to provide a supply voltage for the controller circuitry. The controller circuitry is further configured to: transition to a burst mode to switch on and off the current through the primary winding in first bursts, wherein the first bursts are separated by intervals during which switching on and off the current through the primary winding of the transformer by the first bursts is discontinued and provide second bursts during the intervals in order to keep the supply voltage of the controller circuitry between a lower bound value and an upper bound value while the output voltage ramps down to a requested valley value or provide second bursts during the intervals after reaching a timeout limit in order to provide the supply voltage to the controller circuitry while the output voltage ramps down to a requested valley value.

A method of operating a power conversion system including converting variable frequency AC voltage to constant frequency AC voltage by a power converter, setting a first peak current reset threshold above operating currents previously observed during steady state short circuit current regulation in by a controller of the power converter, setting a second peak current reset threshold at a current lower than the previously observed steady state short-circuit regulation point observed during previous operation during steady state short circuit current regulation by the controllers of the power converter, resetting inverter converter AC output regulating voltage to 0 volts, and ramping AC output regulating voltage back up into steady-state operation when the second a peak current reset threshold is exceeded.

A power supply includes a first DC-DC converter coupled to receive power from a first power source, a second DC-DC converter coupled to receive power from a second power source, and a control block. The first DC-DC converter is operable to generate a regulated power supply voltage on an output node of the power supply. The first power source has a maximum output current limit. The second DC-DC converter is also operable to generate a regulated power supply voltage on the output node. The control block is designed to generate the regulated power supply voltage based on both of the first DC-DC converter and the second DC-DC converter.

A network communication power supply with digital signal isolation includes a transformer, a transformer drive circuit, a rectifier, and a modulation signal duty cycle detection circuit. The transformer has a primary side and a secondary side. The transformer drive circuit is coupled to the primary side, and receives a digital signal input. The transformer drive circuit converts the digital signal input into a drive signal with a duty cycle corresponding to a logic level of the digital signal input according to the logic level. The digital signal input includes a power content. The rectifier is coupled to the secondary side and converts the power content to provide a power source. The modulation signal duty cycle detection circuit is coupled to the rectifier and supplied power by the power source, and provides a digital signal output with a high or low level according to the duty cycle.

An apparatus for DC voltage—DC voltage conversion comprises connected in series a high DC voltage source, a transformer, a rectifier, and a control voltage driver. Also connected in series are a primary winding of the transformer, a controllable switch, an electronically controlled resistor (ECR), and a limiting resistor. The ECR is controlled by the control voltage driver. The controllable switch is controlled by a controllable square wave generator. The controllable square wave generator and the controlled voltage driver are fed from a low DC voltage source. The controllable square wave generator is controlled by another control voltage driver fed from the high DC voltage source. The apparatus allows for obtaining variable value of high pulse voltage across the ECR and lowers the level of electromagnetic noise radiated by the apparatus to environment.