A self-driven active clamp circuit applied to a flyback converter having a transformer and a switch has a clamp switch and a resistor. The clamp switch is connected between a first capacitor and a second capacitor in series. Another terminal of the first capacitor is connected to a first terminal of a primary-side winding of the transformer. Another terminal of the second capacitor is connected to a second terminal of the primary-side winding of the transformer and the switch of the flyback converter. A terminal of the resistor is connected to a control terminal of the clamp switch. Another terminal of the resistor is connected to the second terminal of the primary-side winding of the transformer and the switch of the flyback converter.

A power transfer device includes an oscillator circuit having a first node, a second node, and a control terminal. The oscillator circuit includes a cascode circuit comprising transistors having a first conductivity type and a first breakdown voltage. The cascode circuit is coupled to the control terminal, the first node, and the second node. The oscillator circuit includes a latch circuit coupled between the cascode circuit and a first power supply node. The latch circuit includes cross-coupled transistors having the first conductivity type and a second breakdown voltage. The first breakdown voltage is greater than the second breakdown voltage. The oscillator circuit may be configured to develop a pseudo-differential signal on the first node and the second node. The pseudo-differential signal may have a peak voltage of at least three times a voltage level of an input DC signal on a second power supply node.

The power supply apparatus includes a transformer, at least one switching element provided on a primary side of the transformer and configured to perform a switching operation to output an output voltage from a secondary side of the transformer, and a control unit configured to determine a turn-on time of a pulse signal for controlling the switching element for each of first cycles, and perform a predetermined control in which a change value of the turn-on time of the pulse signal for each of second cycles each including the first cycles becomes smaller than a change value of the turn-on time of the pulse signal for each of the first cycles, to change the second cycle depending on operation states.

The power supply control unit includes an on trigger signal generating unit arranged to generate an on trigger signal for turning on the switching element on the basis of a feedback signal of flyback voltage, a first timer arranged to measure a predetermined minimum OFF time, a second timer arranged to measure time based on an ON time, a minimum OFF time setting unit arranged to compare the predetermined minimum OFF time measured by the first timer with the time measured by the second timer so as to set a longer time as a minimum OFF time, and an on timing determining unit arranged to determine timing for turning on the switching element on the basis of the set minimum OFF time and the on trigger signal.

A DC-to-AC inverter provides an AC voltage to the primary winding of an output isolation transformer having at least one secondary winding. An AC output voltage from the secondary winding is rectified to generate a DC voltage, which is applied to a load. The current flowing through the load is sensed and compared to a reference magnitude to produce a feedback signal. The feedback signal controls a voltage superposition circuit via an output stage of an optocoupler. The superposition circuit generates a superposition voltage that is applied to a current control circuit, which responds to the superposition voltage to vary a control current to a switching controller, which varies the frequency of the AC voltage to thereby vary the load current. A fault detection circuit senses a short in the output stage of the optocoupler to disable the operation of switching controller to prevent an overvoltage and an overcurrent.

A DC-to-AC inverter provides an AC voltage to the primary winding of an output isolation transformer having at least one secondary winding. An AC output voltage from the secondary winding is rectified to generate a DC voltage, which is applied to a load. The current flowing through the load is sensed and compared to a reference magnitude to produce a feedback signal. The feedback signal controls a voltage superposition circuit via an output stage of an optocoupler. The superposition circuit generates a superposition voltage that is applied to a current control circuit, which responds to the superposition voltage to vary a control current to a switching controller, which varies the frequency of the AC voltage to thereby vary the load current. A fault detection circuit senses a short in the output stage of the optocoupler to disable the operation of switching controller to prevent an overvoltage and an overcurrent.

A DC-to-AC inverter provides an AC voltage to the primary winding of an output isolation transformer having at least one secondary winding. An AC output voltage from the secondary winding is rectified to generate a DC voltage, which is applied to a load. The magnitude of a current flowing through the load is sensed and compared to a reference magnitude to produce a feedback signal. The feedback signal controls a voltage superposition circuit, which produces a superposition voltage. The superposition voltage is applied to an input node of a current control circuit. The current control circuit responds to the superposition voltage to vary a magnitude of a control current to a switching controller in the DC to-AC inverter. The switching controller is responsive to the control current magnitude to vary the frequency of the AC voltage and to thereby vary the load current.

A resonant converter, a control method of a resonant converter, and a related device. The resonant converter includes a control circuit, a drive circuit, and a switch circuit. The control circuit is configured to generate, based on a target output electrical parameter of the resonant converter, a first pulse signal and a second pulse signal that have different frequencies. The control circuit is further configured to: obtain a first drive signal based on the first pulse signal and the second pulse signal and send the first drive signal to the drive circuit. The drive circuit is configured to: convert the first drive signal into one or more second drive signals and send the one or more second drive signals to the switch circuit, to turn on or off a switch component in the switch circuit.

A resonant converter, a control method of a resonant converter, and a related device. The resonant converter includes a control circuit, a drive circuit, and a switch circuit. The control circuit is configured to generate, based on a target output electrical parameter of the resonant converter, a first pulse signal and a second pulse signal that have different frequencies. The control circuit is further configured to: obtain a first drive signal based on the first pulse signal and the second pulse signal and send the first drive signal to the drive circuit. The drive circuit is configured to: convert the first drive signal into one or more second drive signals and send the one or more second drive signals to the switch circuit, to turn on or off a switch component in the switch circuit.

Various improvements are provided to resonant DC/DC and AC/DC converter circuit. The improvements are of particular interest for LLC circuits. Some examples relate to self-oscillating circuit and others relate to converter circuits with frequency control, for example for power factor correction, driven by an oscillator.