An electronic converter (1) comprises a pair of input terminals (IN+, IN) particularly suitable to be connected to a power supply unit (10) with a constant electric current output, and a pair of output terminals (OUT+, OUT) particularly suitable to be connected to an electrical load (5). The electronic converter (1) further comprises an electric current conversion stage (2) connected to said input terminals (IN+, IN) and to said output terminals (OUT+, OUT), and a controller (3) connected to the electric current conversion stage (2) and particularly suitable to control the electrical energy output from the electronic converter (1).

A load control device for controlling the amount of power delivered to an electrical load (e.g., an LED light source) includes first and second semiconductor switches, a transformer, a capacitor, a controller, and a current sense circuit operable to receive a sense voltage representative of a primary current conducting through to a primary winding of the transformer. The primary winding is coupled in series with a semiconductor switch, while a secondary winding is adapted to be operatively coupled to the load. The capacitor is electrically coupled between the junction of the first and second semiconductor switches and the primary winding. The current sense circuit receives a sense voltage and averages the sense voltage when the first semiconductor switch is conductive, so as to generate a load current control signal that is representative of a real component of a load current conducted through the load.

Embodiments described herein are directed to an energy-harvesting circuit configured to harvest energy from a power converter circuit within a switch mode power supply and generate a positive, a negative or a bipolar power supply rail to power load circuitry. The energy-harvesting circuit includes a transformer, a coupling capacitor, a diode and a capacitor. The transformer has a primary winding, a secondary winding and a magnetic core shared therebetween. The primary winding is electrically connected between a drain and a source of a transistor switch connected to the power converter circuit. The coupling capacitor is electrically connected between the drain and the primary winding and configured to provide a reset mechanism for the magnetic core. The anode of the diode is electrically connected to the secondary winding. The capacitor is electrically connected in series with the cathode of the diode and in parallel with the load circuitry.

An over current protection circuit, comprising: a current transformer, having a primary winding connected in series with a primary winding of a power supply transformer and a secondary winding, of which one end is grounded and the other end is coupled to a diode anode; a first resistor, having one end coupled to a diode cathode and the other end grounded; a second resistor, having one end coupled to the diode cathode and the other end coupled to a zener diode cathode; a triode, having a base coupled to a zener diode anode, an emitter grounded and a collector coupled to a light emitter cathode; wherein a light emitter anode is coupled to a LLC chip and a first voltage output end in the power supply; an output end of a light receiver is ground, an input end is coupled to a second voltage output end and a PFC chip.

A rectifying element is connected to an auxiliary winding. The shut-down circuit receives a bias voltage output from the rectifying element. A shut-down circuit stops supply of power to a power supply terminal of the power supply control IC when the bias voltage is less than a set voltage. A power supply control IC controls a ratio of on-time to a switching cycle of the switching element, based on a current sensing voltage generated at a current sense resistor. The power supply control IC causes the switching operation of the switching element to stop when a voltage at the power supply terminal decreases to a stop voltage or less.

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.

An improved electrical power conversion system converts a high voltage (HV) from a HV electrical power supply to a low voltage. The electrical power conversion system includes at least one power converter and at least one RC network connected in series. The RC network includes a plurality of resistive components and a plurality of capacitive components electrically connected in series. The at least one RC network and at least one power converter are arranged to be connected across a line potential of the HV electrical power supply.

A multi-input voltage converter includes an output circuit, a first conversion circuit, and a second conversion circuit. The first conversion circuit includes a first voltage receiving module, a first transformer, a first switch. The second conversion circuit includes a second voltage receiving module, a second switch. When the second voltage receiving module receives the second input voltage, the second switch is turned on to operate, and the output circuit outputs the output voltage.

First, it is assumed that a low-side switching element is turned off. At this time a resonance current before-inversion time is counted. When a resonance current is inverted, a count value is held and the counting operation of a resonance current after-inversion time is begun. Next, a target value of the resonance current after-inversion time at which a high-side switching element is to be turned off is calculated based on a feedback signal and the counting operation of the resonance current after-inversion time is continued. When a count value reaches the target value, the counting operation of the resonance current after-inversion time is ended and the high-side switching element is turned off. After a high-side half cycle is controlled, a low-side half cycle is controlled in the same way. Responsiveness to a sudden change in load is improved by exercising control every half cycle.

An AC-to-DC converter circuit includes DC-to-DC converter that in turn includes a secondary side circuit. The secondary side circuit includes a secondary winding, a pair of bipolar transistor-based self-driven synchronous rectifiers, a pair of current splitting inductors, and an output capacitor. Each of the synchronous rectifiers includes a bipolar transistor and a diode whose anode is coupled to the transistor collector and whose cathode is coupled to the transistor emitter. The current splitting inductors provide the necessary base current to the bipolar transistors at the appropriate times such that the bipolar transistors operate as synchronous rectifiers. As compared to using conventional self-driven synchronous rectifiers based on field effect transistors in the secondary side, using the novel bipolar-transistor based synchronous rectifiers in the secondary side of the forward converter circuit results in lower power consumption and allows the converter to operate from a wider range of VAC input voltages.