The present invention provides a method and apparatus for detecting a continuous current of a switching current. A current signal is produced in response to a switching current of the magnetic device. By sampling the waveform of the current signal in response to the enabling of a switching signal, a first current signal and a second current signal are generated. A continuous current signal is produced according to the first current signal and the second current signal. The continuous current sig...

A linear-predict sampling circuit is developed to generate a feedback signal by detecting a demagnetized voltage of the transformer. A switching signal is generated in response to the feedback signal for regulating the output of the power converter. A signal-generation circuit is used to generate a sample signal in response to a first signal, a second signal, and the switching signal. The first signal is correlated to a magnetized voltage of the transformer. The second signal is correlated to th...

A control circuit having frequency modulation is used for reducing the EMI of a power converter. A switching circuit is couple to a feedback circuit to generate a switching signal for regulating an output of the power converter. A first oscillator is equipped to determine a switching frequency of the switching signal. A second oscillator is coupled to the first oscillator to modulate the switching frequency of the switching signal for reduce the EMI of the power converter. A programmable resisto...

A method and apparatus for predicting the discharge time of magnetic device are provided. A switching circuit generates a switching signal and an auxiliary signal. The switching signal is used to regulate the switching regulator. The auxiliary signal is used to control the synchronous rectifier. An evaluation circuit generates a timing signal in response to an input signal and the switching signal. The input signal is correlated to the input voltage of the switching regulator. The timing signal ...

A control circuit for detecting the reflected voltage of a transformer is provided. A detection circuit is developed for sampling the reflected voltage. Because the pulse width of the reflected voltage is narrower at light load, a bias circuit is utilized for producing a bias signal to help the reflected voltage detection. Furthermore, a blanking circuit ensures a minimum pulse width of the reflected voltage.

An offline control circuit of LED driver controls the maximum voltage and the maximum current of a plurality of LEDs. A switching circuit generates a plurality of LED currents through a transformer. A voltage-feedback circuit generates a voltage loop signal in response to the voltage across the LEDs. A current-feedback circuit senses a plurality of LED currents for generating a current loop signal in response the maximum current of the LEDs. A buffer circuit generates a feedback signal in accord...

A low dropout (LDO) regulator operates in wide input range. The LDO includes an N-type pass transistor and a P-type pass transistor for supplying power to the output terminal. The P-type pass transistor is connected with N-type pass transistor in parallel. Two error amplifiers control the gate terminals of the N-type pass transistor and P-type pass transistor to generate a first output voltage and a second output voltage. Thus, the first output voltage is generated when the input voltage is high...

A switching regulator having an energy saving circuit and an energy saving method is provided to improve the system efficiency under light load conditions. A first control unit outputs an oscillation signal and an energy saving signal in response to the variation of a feedback signal. A second control unit receives the feedback signal and the oscillation signal to output a switching signal to control a switch. An off-time of the switching signal is increased in response to a decrement of the loa...

The invention provides a frequency modulation for a PWM controller to reduce the switching frequency in the light load and no load conditions. The frequency modulation is achieved by moderating the trip-point voltage of the oscillator. Increasing the trip-point voltage reduces the switching frequency. A feedback voltage, which is derived from the voltage feedback loop, is taken as the reference. The sense voltage in the current sense input of the PWM controller represents the information of prim...

The present invention provides an off-time modulation in PWM controller to increase the switching period for saving power consumption in the light load and no load conditions. The off-time modulation is achieved by keeping the charge current as a constant and moderating the discharge current of the saw-tooth-signal generator of the PWM controller. Decreasing the discharge current increases the switching period. A feedback voltage, which is derived from the voltage feedback loop, is taken as an i...