Abstract: The present invention discloses a high efficiency constant current LED driver, which comprises a rectification bridge, a PFC main circuit, an isolated DC/DC converter, a PFC controller and a PFC bus control circuit. Since the input voltage is an intermediate PFC bus voltage, which varies with the output voltage of the DC/DC converter. When the isolated DC/DC converter is an LLC resonant circuit, the operating frequency of the LLC circuit is close to the resonant frequency within a wide output voltage range. Thus, the gain range and the operating frequency is narrow, and can enable the constant current module to work with a high efficiency at a wide output voltage range. When the isolated DC/DC converter is a symmetric half bridge, or an asymmetric half bridge or a full bridge circuit, the duty cycle of DC/DC circuit is close to 50% within a wide output voltage range. Thus, the changing range of the duty cycle of the DC/DC converter will be narrow and can improve the efficiency dramatically.

Abstract: A constant current control circuit with multiple outputs for a LED driver, the circuit including a single-output constant current power supply, and multiple output circuits, each output circuit comprising a current sharing circuit, a current sharing control circuit and a LED load. The LED load and the current sharing circuit are in series and form a series loop with a first terminal and a second terminal of the series loop connected to a first output terminal and a second output terminal of the constant current power supply.

Abstract: A circuit to improve the power factor of a power supply at light load, the circuit including a rectifier bridge, a filter positioned before or after the rectifier bridge, a logic control and power drive circuit, a switching transistor, a light load detecting circuit configured to output a control signal to the logic control and power drive circuit which controls the switching transistor to conduct when a heavy load is experienced and to cut off when a light load is experienced, in order to control the working status of the filter capacitor, and a power factor correction circuit.

Abstract: The present invention discloses a high efficiency constant current LED driver, which comprises a rectification bridge, a PFC main circuit, an isolated DC/DC converter, a PFC controller and a PFC bus control circuit. Since the input voltage is an intermediate PFC bus voltage, which varies with the output voltage of the DC/DC converter. When the isolated DC/DC converter is an LLC resonant circuit, the operating frequency of the LLC circuit is close to the resonant frequency within a wide output voltage range. Thus, the gain range and the operating frequency is narrow, and can enable the constant current module to work with a high efficiency at a wide output voltage range. When the isolated DC/DC converter is a symmetric half bridge, or an asymmetric half bridge or a full bridge circuit, the duty cycle of DC/DC circuit is close to 50% within a wide output voltage range. Thus, the changing range of the duty cycle of the DC/DC converter will be narrow and can improve the efficiency dramatically.

Abstract: A LED drive circuit for SCR dimming including an external controller configured to receive AC voltage from a power network to convert the AC voltage to an AC voltage with a lacked phase by phase controlling the voltage through a thyristor, and a LED driver that includes a bridge rectifier configured to shape the AC voltage with the lacked phase output into a unidirectional pulse DC voltage, and a phase angle detecting circuit configured to shape the AC voltage signal output with lacked phase from the external controller into a saw-tooth wave pulse signal.

Abstract: A PWM dimming circuit for a LED load including a LED load connected to the main LED drive circuit, a current loop configured to measure output current from the LED load, a current loop regulation circuit connected to the current loop, a main control circuit configured to receive a signal from the current loop when the LED load produces an output current, and a PWM dimming controller configured to provide a signal to control the current loop regulation circuit and to make the current loop operate in a closed-loop mode when the LED load produces the output current and to provide a shutdown signal to the main control circuit when the LED load does not produce the output current. When the output current is detected, the main control circuit controls the main LED drive circuit to set its output current at a predetermined load current.

Abstract: A circuit to improve the power factor of a power supply at light load, the circuit including a rectifier bridge, a filter positioned before or after the rectifier bridge, a logic control and power drive circuit, a switching transistor, a light load detecting circuit configured to output a control signal to the logic control and power drive circuit which controls the switching transistor to conduct when a heavy load is experienced and to cut off when a light load is experienced, in order to control the working status of the filter capacitor, and a power factor correction circuit.

Abstract: The present invention discloses a high efficiency constant current LED driver, which comprises a rectification bridge, a PFC main circuit, an isolated DC/DC converter, a PFC controller and a PFC bus control circuit. Since the input voltage is an intermediate PFC bus voltage, which varies with the output voltage of the DC/DC converter. When the isolated DC/DC converter is an LLC resonant circuit, the operating frequency of the LLC circuit is close to the resonant frequency within a wide output voltage range. Thus, the gain range and the operating frequency is narrow, and can enable the constant current module to work with a high efficiency at a wide output voltage range. When the isolated DC/DC converter is a symmetric half bridge, or an asymmetric half bridge or a full bridge circuit, the duty cycle of DC/DC circuit is close to 50% within a wide output voltage range. Thus, the changing range of the duty cycle of the DC/DC converter will be narrow and can improve the efficiency dramatically.

Abstract: A constant current control circuit with multiple outputs for a LED driver, the circuit including a single-output constant current power supply, and multiple output circuits, each output circuit comprising a current sharing circuit, a current sharing control circuit and a LED load. The LED load and the current sharing circuit are in series and form a series loop with a first terminal and a second terminal of the series loop connected to a first output terminal and a second output terminal of the constant current power supply.

Abstract: A PWM dimming circuit for a LED load including a LED load connected to the main LED drive circuit, a current loop configured to measure output current from the LED load, a current loop regulation circuit connected to the current loop, a main control circuit configured to receive a signal from the current loop when the LED load produces an output current, and a PWM dimming controller configured to provide a signal to control the current loop regulation circuit and to make the current loop operate in a closed-loop mode when the LED load produces the output current and to provide a shutdown signal to the main control circuit when the LED load does not produce the output current. When the output current is detected, the main control circuit controls the main LED drive circuit to set its output current at a predetermined load current.

Abstract: A LED drive circuit for SCR dimming including an external controller configured to receive AC voltage from a power network to convert the AC voltage to an AC voltage with a lacked phase by phase controlling the voltage through a thyristor, and a LED driver that includes a bridge rectifier configured to shape the AC voltage with the lacked phase output into a unidirectional pulse DC voltage, and a phase angle detecting circuit configured to shape the AC voltage signal output with lacked phase from the external controller into a saw-tooth wave pulse signal.