Abstract: A current mode controller includes: an error amplifier configured to generate an error signal that corresponds to the difference between a reference voltage and a voltage indicative of an output voltage of a power converter; a first current measurement circuit configured to measure current flowing in a high-side switch device of the power converter; a second current measurement circuit configured to measure current flowing in a low-side switch device of the power converter; a comparator configured to indicate when a voltage derived by the first current measurement circuit exceeds the error signal in a peak current control mode, and when a voltage derived by the second current measurement circuit drops below the error signal in a valley current control mode; and circuitry configured to configure the comparator in either the peak current control mode or the valley current control mode for each switching cycle of the power converter.

Abstract: A start-up circuit includes an input node, an output node, a reference node, and a depletion mode field-effect transistor (FET) having a first terminal coupled to the input node, a second terminal coupled to the output node, and a gate terminal. A Zener diode has a cathode coupled to the gate terminal of the FET and an anode coupled to the reference node. A first capacitor is coupled in parallel with the Zener diode, a first resistor is coupled between the gate terminal of the FET and the input node, and a second resistor is coupled between the second terminal of the FET and the reference node. The FET and the second resistor are configured to generate an output voltage on the output node, the output voltage being based on an input voltage on the input node and capped at a value below a peak value of the input voltage.

Abstract: For starting-up a power converter, an AC rectified voltage is generated upon power-up of the power converter. A depletion mode transistor generates a first voltage from the rectified voltage. The first voltage is inputted to a controller of the power converter to provide power for operation of the controller before an output stage of the power converter starts outputting power. A gate biasing voltage is generated from the first voltage and supplied to a gate terminal of the depletion mode transistor to bias the gate terminal of the depletion mode transistor.

Abstract: A start-up circuit includes an input node, an output node, a reference node, and a depletion mode field-effect transistor (FET) having a first terminal coupled to the input node, a second terminal coupled to the output node, and a gate terminal. A Zener diode has a cathode coupled to the gate terminal of the FET and an anode coupled to the reference node. A first capacitor is coupled in parallel with the Zener diode, a first resistor is coupled between the gate terminal of the FET and the input node, and a second resistor is coupled between the second terminal of the FET and the reference node. The FET and the second resistor are configured to generate an output voltage on the output node, the output voltage being based on an input voltage on the input node and capped at a value below a peak value of the input voltage.

Abstract: An AC-DC power converter includes a rectifying unit for generating a rectified voltage, an output stage for converting the rectified voltage into a DC voltage for a load, a controller for controlling the output stage, and a start-up circuit. The start-up circuit includes a start-up voltage generator coupled to the rectifying unit and configured to generate a start-up voltage from the rectified voltage and to output the start-up voltage to the controller to provide power for operation of the controller before the output stage starts outputting power. The start-up voltage generator includes a first depletion mode transistor having a first terminal configured to receive the rectified voltage, a second terminal configured to output at least partially the start-up voltage, and a gate terminal which is grounded.

Abstract: An AC-DC power converter includes a rectifying unit for generating a rectified voltage, an output stage for converting the rectified voltage into a DC voltage for a load, a controller for controlling the output stage, and a start-up circuit. The start-up circuit includes a first power section coupled to the rectifying unit and configured to generate a first voltage from the rectified voltage and to output the first voltage to the controller to enable the controller before the output stage starts outputting power. The first power section includes a depletion mode transistor having a first terminal configured to receive the rectified voltage and a second terminal configured to output the first voltage.

Abstract: An AC-DC power converter includes a rectifying unit, an output stage, a controller and a soft-start circuit. The rectifying unit is configured to rectify an AC voltage to a rectified voltage. The output stage is coupled to the rectifying unit and configured to convert the rectified voltage into a DC voltage for a load. The controller is coupled to the output stage and configured to control the output stage. The soft-start circuit is coupled to the rectifying unit to receive the rectified voltage. The soft-start circuit is configured to detect whether the rectified voltage is at or below a predetermined level, and to enable the controller if the rectified voltage is detected to be at or below the predetermined level.

Abstract: For starting-up a power converter, an AC rectified voltage is generated upon power-up of the power converter. A depletion mode transistor generates a first voltage from the rectified voltage. The first voltage is inputted to a controller of the power converter to provide power for operation of the controller before an output stage of the power converter starts outputting power. A gate biasing voltage is generated from the first voltage and supplied to a gate terminal of the depletion mode transistor to bias the gate terminal of the depletion mode transistor.

Abstract: An AC-DC power converter includes a rectifying unit for generating a rectified voltage, an output stage for converting the rectified voltage into a DC voltage for a load, a controller for controlling the output stage, and a start-up circuit. The start-up circuit includes a first power section coupled to the rectifying unit and configured to generate a first voltage from the rectified voltage and to output the first voltage to the controller to enable the controller before the output stage starts outputting power. The first power section includes a depletion mode transistor having a first terminal configured to receive the rectified voltage and a second terminal configured to output the first voltage.