A power supply circuit includes: an anti-electromagnetic interference circuit configured to receive input alternating current power and to output filtered alternating current power; a rectifier circuit configured to rectify the filtered alternating current power; a current correction circuit configured to perform passive power factor correction on the rectified alternating current power; a single-ended flyback converter circuit coupled to the output of the current correction circuit; and a dimming control circuit coupled between the output of the single-ended flyback converter circuit and a light load, wherein the current correction circuit is configured to control a waveform of the rectified alternating current power to follow a current output to the light load in order to provide passive power factor correction.

A power supply circuit includes: an anti-electromagnetic interference circuit configured to receive input alternating current power and to output filtered alternating current power; a rectifier circuit configured to rectify the filtered alternating current power; a current correction circuit configured to perform passive power factor correction on the rectified alternating current power; a single-ended flyback converter circuit coupled to the output of the current correction circuit; and a dimming control circuit coupled between the output of the single-ended flyback converter circuit and a light load, wherein the current correction circuit is configured to control a waveform of the rectified alternating current power to follow a current output to the light load in order to provide passive power factor correction.

A power supply circuit includes: an anti-electromagnetic interference circuit configured to receive input alternating current power and to output filtered alternating current power; a rectifier circuit configured to rectify the filtered alternating current power; a current correction circuit configured to perform passive power factor correction on the rectified alternating current power; a single-ended flyback converter circuit coupled to the output of the current correction circuit; and a dimming control circuit coupled between the output of the single-ended flyback converter circuit and a light load, wherein the current correction circuit is configured to control a waveform of the rectified alternating current power to follow a current output to the light load in order to provide passive power factor correction.

A controller includes a multiplier block that is coupled to receive an input voltage signal, an input current signal, and an output voltage signal that are representative of a power conversion system. The multiplier block outputs a multiplier block output signal responsive to a product of the input voltage signal and the input current signal divided by the output voltage signal. A signal discriminator outputs a error signal responsive to the multiplier block output signal. The error signal is representative of a difference between a portion of the multiplier block output signal that is greater than a reference signal and a portion of the multiplier block output signal that is less than or equal to the reference signal. A switch controller generates a drive signal responsive to the error signal to control switching of a power switch to regulate an average output current of the power conversion system.

A controller includes a multiplier block that is coupled to receive an input voltage signal, an input current signal, and an output voltage signal that are representative of a power conversion system. The multiplier block outputs a multiplier block output signal responsive to a product of the input voltage signal and the input current signal divided by the output voltage signal. A signal discriminator outputs a error signal responsive to the multiplier block output signal. The error signal is representative of a difference between a portion of the multiplier block output signal that is greater than a reference signal and a portion of the multiplier block output signal that is less than or equal to the reference signal. A switch controller generates a drive signal responsive to the error signal to control switching of a power switch to regulate an average output current of the power conversion system.

Malfunctions of a switching device included in a power factor corrector are reduced when an instantaneous voltage drop or an instantaneous power failure occurs. If the instantaneous voltage drop or the instantaneous power failure occurs in an AC power source while the power factor corrector is performing a power factor correction operation by boosting an input voltage, an instantaneous power failure controller turns off the switching device included in the power factor corrector so that the power factor correction operation stops. When the commercial power source recovers, too, the power factor corrector suspends the power factor correction operation.

Malfunctions of a switching device included in a power factor corrector are reduced when an instantaneous voltage drop or an instantaneous power failure occurs. If the instantaneous voltage drop or the instantaneous power failure occurs in an AC power source while the power factor corrector is performing a power factor correction operation by boosting an input voltage, an instantaneous power failure controller turns off the switching device included in the power factor corrector so that the power factor correction operation stops. When the commercial power source recovers, too, the power factor corrector suspends the power factor correction operation.

A power supply system is provided including a transformer, a plurality of switches, a rectifier circuit, and a controller. The transformer includes at least one primary winding and at least one secondary winding. The plurality of switches is configured to receive an input direct current (DC) power and provide a transformer input power to the primary winding. The secondary winding is configured to provide a transformer output power based on the transformer input power. The rectifier circuit is configured to receive the transformer output power and provide an output DC power to one or more external loads. The output DC power is a product of a total load current and an output voltage. The controller is configured to determine the total load current required for the external loads and control the plurality of switches to provide a switching frequency based on the total load current required for the external loads.

A power supply system is provided including a transformer, a plurality of switches, a rectifier circuit, and a controller. The transformer includes at least one primary winding and at least one secondary winding. The plurality of switches is configured to receive an input direct current (DC) power and provide a transformer input power to the primary winding. The secondary winding is configured to provide a transformer output power based on the transformer input power. The rectifier circuit is configured to receive the transformer output power and provide an output DC power to one or more external loads. The output DC power is a product of a total load current and an output voltage. The controller is configured to determine the total load current required for the external loads and control the plurality of switches to provide a switching frequency based on the total load current required for the external loads.