A power conversion apparatus includes a primary-side circuit, a bulk capacitor, a conversion circuit, and a master control circuit. The primary-side circuit is adapted to rectify and boost an alternating-current power and output primary-side output. The bulk capacitor is connected in parallel to two output ends of the primary-side output. The conversion circuit is configured to receive the primary-side output passing through the bulk capacitor and convert the primary-side output into secondary-side output. The master control circuit detects an electric power state of the alternating-current power, obtains a time interval, a power of the secondary-side output corresponding to the time interval, and two of the capacitor voltages corresponding to the start and the end of the time interval when the electric power state is power-off, and selectively outputs an abnormal signal according to the time interval, the power, the capacitor voltages, and a threshold.

A converter includes first and second input terminals; an integrated circuit (IC) that is a non-resonant, step-down, and point-of-load IC, that is connected to the first and second input terminals, and that includes a feedback terminal and switch-output terminal; a voltage-sense circuit connected to the feedback terminal and the switch-output terminal; a transformer that includes a primary winding connected to the switch-output terminal; a capacitor connected in series with the primary winding; a rectifier connected to a secondary winding of the transformer; and first and second output terminals connected to the rectifier. The converter is operated in a resonate mode.

Voltage converter controllers, voltage converters and methods are discussed regarding the adjustment of an on-time of an auxiliary switch of a voltage converter. First and second voltages are measured before a primary switch of the voltage converter is turned on and while the primary switch is turned on, and the on-time is adjusted based on the voltages.

The present invention discloses a power supply circuit and a UPS auxiliary power supply system having the same. The power supply circuit comprises a transformer, a primary-side switch unit and a secondary-side switch unit. When the input power supply is powered on, the second switch of the secondary-side switch unit maintains in an off state, the first switch of the primary-side switch unit performs an on-off action, and the input power supply supplies power to the load and the energy storage unit. When the input power supply is powered down, the first switch of the primary-side switch unit maintains in an off state, the second switch of the secondary-side switch unit performs an on-off action, and the energy storage unit supplies power to the load.

The present invention relates to a current loop powered DC-DC switch mode converter for use as a local isolated low power supply for electronic circuits such as current loop transmitters where the requirements for supply efficiency and cost of the implementation is critical. It is the object of the invention to provide a simple and low cost solution for driving a synchronous rectifier thereby improving the supply efficiency, especially at low output voltages.

A control circuit for an isolated power converter includes a first sensing circuit that senses a secondary side output voltage and produces a pulse wave modulation (PWM) signal having a duty cycle that is proportional to a value of the secondary side output voltage. The PWM is transferred across the converter isolation barrier to the primary side, and a primary side circuit receives the PWM signal and outputs a control signal. A controller determines the value of the secondary side output voltage from the control signal and uses the value to control primary side power switching devices of the isolated power converter to regulate the secondary side output voltage at a selected value.

A switching power conversion apparatus for converting power from an input voltage source to a load includes first and second switches connected to a switching node. An inductive element has a magnetizing current connected to the node, and the inductive element is connected to deliver energy via the first and second switches from the input voltage to the load during a succession of power conversion cycles. A capacitance connected to the node resonates with the inductive element to cause parasitic oscillation. A clamp subcircuit across the inductive element contains an auxiliary switch to trap energy and prevent parasitic oscillation, wherein the auxiliary switch is complementary to the first switch. A controlled voltage source injects energy in the inductive element, when the auxiliary switch turns off to discharge the parasitic capacitance by using trapped energy in the inductive element in addition to injected energy from the controlled voltage source.

A variable DC-DC converter includes a no-load voltage clamp in which a rectified, filtered, and loaded control signal drives a switch. The switch switches in a load resistance across the output terminals of the converter when the output terminals are unloaded or lightly loaded. Due to a combined rectification, smoothing, and filtering operation of the control signal circuit, the control signal provides a steady voltage of the output voltage selected by a user of the converter based on predetermined output requirements. The control signal is therefore not subject to the voltage spikes that the main output is subject to. The circuit compares the control signal to the output voltage, and switches in the load resistance when the voltage at the output rises above the control signal.

The power supply apparatus includes a switching element configured to drive a transformer, a primary side and a secondary side of the transformer being insulated from each other, a control unit configured to output a pulse signal for driving the switching element, and a comparing unit configured to compare a target voltage of an output voltage that is output from the secondary side of the transformer and the output voltage, and to control the output voltage to be the target voltage, wherein the comparing unit cuts off an input of the pulse signal to the switching element in a case where the output voltage is larger than the target voltage, and wherein the control unit determines a frequency or an on-duty ratio of the pulse signal according to the target voltage.

A power supply apparatus for driving a light emitting apparatus is provided. The power supply apparatus includes a lossless snubber circuit and a power converting circuit. The lossless snubber circuit has a first diode, a first inductor and a second diode coupled in series between an input end and a first reference end, and has a first capacitor coupled between the first diode and a second reference end. The power converting circuit has a switch, a transformer and a second indictor. The switch is coupled between the first and second reference ends, and is turned on or off according to a control signal. The second inductor is coupled to a first side of the transformer in parallel.