A power converter delivers electrical power from an electrical power source to a load according to a plurality of operation modes corresponding to different levels of input voltage or output current. The power converter comprises a power stage for delivering the electrical power from the power source to the load, a switch in the power stage that electrically couples or decouples the load to the power source, and a switch controller coupled to the switch for controlling the on-times and off-times of the switch according to the plurality of operation modes. Each of the operation modes correspond to associated ranges of at least one of an input voltage to the power converter and an output current from the power converter, where the associated ranges are different for each of the operation modes.

System and method for input current shaping in a power converter

A power factor controller or corrector is provided in a regulated power supply circuit, in which the load and line regulation circuitry is separate from one another and in which the line regulation is provided with a 1/x2 modulator in which the switching frequency is inversely proportional to the square of the line voltage.

Power factor controller

An adaptive off-time modulator of a PWM controller is provided for power saving in the light-load and no-load conditions. The maximum on-time is kept as a constant and a bias current of the oscillator in the PWM controller is moderated to achieve the off-time modulation. Reduction of the bias current increases the off-time of the switching period. The bias current is a function of the supply voltage and the feedback voltage, which is derived from a voltage feedback loop. A threshold voltage defines the level of the light load. A limit voltage defines the low level of the supply voltage. A bias current synthesizer generates the bias current. Once the feedback voltage is decreased lower than the threshold voltage, the bias current is reduced linearly and the off-time of the switching period is increased gradually. When the supply voltage is lower than the limit voltage, the bias current increases and determines a maximum off-time of the switching period. The maximum on-time and off-time of the switching period determines the PWM frequency. As the limit voltage varies in every switching cycle, the frequency spectrum of PWM signal spreads in light-load and no-load conditions; and therefore, the acoustic noise is suppressed. The feedback voltage and the supply voltage determine the switching period of the PWM signal. The maximum on-time is kept constant and the switching period is increased by increasing the off-time, such that the magnetic components, such as inductors and transformers, are prevented from being saturated.

PWM controller having adaptive off-time modulation for power saving

A method and apparatus to implement parallel current mode control that is suitable for digital and analog implementation. A duty cycle algorithm is composed of a voltage term and a parallel current term which depends on the inductor current change between the inductor current value at the beginning of a switching cycle and the reference inductor current value at the end of that switching cycle. Parallel current mode control can be applied to all DC-DC converters, including both non-isolated and isolated topologies. It can also be applied to AC-DC converters with power factor correction.

Parallel Current Mode Control Using a Direct Duty Cycle Algorithm with Low Computational Requirements to Perform Power Factor Correction

An example controller includes first, second and third inputs, a delayed ramp generator and a drive signal generator. The first, second and third inputs are coupled to receive an input voltage sense signal, an output voltage sense signal, and an input current sense signal, respectively. The drive signal generator is coupled to receive an input charge control signal generated by an input charge control signal generator and a delayed ramp signal generated by a delayed ramp generator. The input charge control signal is generated responsive to an integral of the input current sense signal multiplied by a ratio of the input voltage sense signal to the output voltage sense signal, where the drive signal generator produces a drive signal responsive to the input charge control signal and the delayed ramp signal, the drive signal to be coupled to control a switch of a power supply to regulate an output of the power supply.

Single-stage power supply with power factor correction and constant current output

Methods and apparatus are disclosed for suppressing or eliminating nonlinear current drawing characteristics, while at the same time substantially eliminating high order current harmonics. In accordance with various aspects of the present invention, an energy transfer system, for example a pulse width modulator (PWM) flyback converter ( 22 ), comprises an inductor (L) interposed between the AC line voltage and the load (R load ), with a controllable switch ( 26 ) provided between the inductor (L) and the negative supply leg of a rectifier circuit ( 10 ). The duty cycle of the converter switch ( 26 ) is suitably controlled to produce a substantially constant DC output from the converter ( 22 ). Proper synchronization of the converter switch ( 26 ) ensures that the current through the inductor (L) and the output current through the load (R load ) remains in phase with the AC supply voltage. Thus, a power factor on the order of unity is maintained while substantially eliminating nonlinear current drawing characteristics.

Apparatus for suppressing nonlinear current drawing characteristics

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Apparatus for suppressing nonlinear current drawing characteristics