A power supply system comprising: an input terminal operable to receive an input voltage; a transformer coupled to the input terminal and defining a primary side and a secondary side; an output terminal coupled to the secondary side of the transformer and connectable to a load for providing current thereto; and means for regulating the power supply system from the primary side so that the current provided to the load at the output terminal is substantially constant, wherein the means for regulating comprises: a control circuit having a power switch through which drain current flows; and the feedback circuit coupled to the control circuit; wherein the control circuit and the feedback circuit are operable to regulate a voltage at the output terminal in a steady-state operation of the power supply system and further operable to provide a constant current output to the load when a voltage at the output terminal is lower than a certain value; wherein the transformer comprises a first and second primary side winding and a secondary side winding, wherein the power switch of the control circuit is coupled to the first primary side winding, and wherein the output terminal is coupled to the secondary side winding. view more

The power supply system of claim 1 wherein the feedback circuit comprises a resistor coupled to the control circuit through which current may flow to reduce the drain current flowing through the power switch in the control circuit.

The power supply system of claim 1 wherein the feedback circuit comprises a resistor coupled to the control circuit to adjust the drain current flowing through the power switch in the control circuit.

The power supply system of claim 1 wherein the feedback circuit is coupled to the second primary side winding.

The power supply system of claim 1 wherein at least a portion of the control circuit is implemented as an integrated circuit device.

A power supply system comprising: an input trminal operable to receive an input voltage; a transformer coupled to the input terminal and defining a primary side and a secondary side; an output terminal coupled to the secondary side of the transformer and connectable to a load for providing current thereto; a control circuit coupled to the transformer and operable to control current flowing through the transformer, wherein the control circuit comprises a power switch through which drain current flows; and a feedback circuit coupled to the control circuit and the transformer, the feedback circuit operable to support regulation by the control circuit from the primary side so that the current provided to the load at the output terminal is substantially constant; wherein the transformer comprises a first and second primary side winding and a secondary side winding, wherein the power switch of the control circuit is coupled to the first primary side winding, and wherein the output terminal is coupled to the secondary side winding. view more

The power supply system of claim 8 wherein the feedback circuit comprises a resistor coupled to the control circuit through which current may flow to reduce the drain current flowing through the power switch in the control circuit.

The power supply system of claim 8 wherein the feedback circuit is coupled to the second primary side winding.

The power supply system of claim 8 wherein at least a portion of the control circuit is implemented as an integrated circuit device.

The power supply system of claim 8 wherein the feedback circuit comprises a resistor coupled to the control circuit to adjust current flowing through the control circuit.

A power supply system comprising: an input terminal operable to receive an input voltage; a transformer coupled to the input terminal and defining a primary side and a secondary side; an output terminal coupled to the secondary side of the transformer and connectable to a load for providing current thereto; a control circuit coupled to the transformer and operable to control current flowing through the transformer, wherein the control circuit comprises a power switch through which drain current flows; and a feedback circuit coupled to the control circuit and the transformer, the feedback circuit operable to support regulation by the control circuit from the primary side so that the current provided to the load at the output terminal is substantially constant; wherein the transformer comprises a first and second primary side winding and a secondary side winding, wherein the power switch of the control circuit is coupled to the first primary side winding, and wherein the output terminal is coupled to the secondary side winding. view more

The power supply system of claim 13 wherein the feedback circuit is coupled to the second primary side winding of the transformer.

NA

The power converter of claim 5, wherein the controller generates the first feedback signal by sampling a voltage from the auxiliary winding of the transformer and a discharge time of the transformer.

The power converter of claim 6, further comprising: a sense circuit to sense current through the primary winding of the transformer.

The method of claim 17, further comprising: generating the first feedback signal by sampling a voltage from an auxiliary winding of the transformer and a discharge time of the transformer.

The method of claim 18, further comprising: sensing a current through a primary winding of the transformer.

A LED controller, comprising: a control circuit, generating a LED current for controlling the LED; a control terminal of the control circuit, coupled for receiving a control signal for determining the LED current; and a sense terminal of the control circuit, coupled to the LED for detecting a LED voltage, wherein the LED voltage is coupled for adjusting the LED current. view more