Abstract: A high-side transistor driver including a driver circuit for generating a driving signal to drive a high-side transistor is provided. A floating supply terminal provides a supply voltage to the driver circuit. A floating ground terminal is connected to a source of the high-side transistor. A bootstrap diode is coupled between the floating supply terminal and a voltage source. A capacitor is connected to the bootstrap diode and is coupled between the floating supply terminal and the floating ground terminal. A high-voltage transistor is used for switching off the driving signal and the high-side transistor in response to an input signal. A speed-up capacitor is coupled to the driver circuit for speeding up the driving signal. Furthermore, the positive feedback circuits in the driver circuit further accelerate the driving signal and save power for the driver circuit.

Abstract: A transistor drive circuit of a power converter is developed for operating in wide voltage range. It includes an N-type high-side transistor, a P-type high-side transistor and an N-type low-side transistor. A voltage clamp device is connected to the gate of the N-type high-side transistor to limit the maximum output voltage. A detection circuit is coupled to detect the supply voltage of the transistor drive circuit to generate a disable signal in response to the voltage level of the supply voltage. The disable signal is coupled to disable the P-type high-side transistor once the voltage level of the supply voltage is higher than a threshold voltage.

Abstract: A switching regulator includes a switching device to switch a transformer from a primary-side to secondary side. A control circuit generates a switching signal for regulating output of the switching regulator. The control circuit includes a first circuit to generate a first signal and a timing signal by measuring a reflected signal of the transformer. A second circuit produces a second signal by integrating a current signal with the timing signal. The current signal represents a primary-side switching current of the transformer. A first feedback circuit produces a first feedback signal in response to the first signal and the reference signal, in which the reference signal is varied in response to the change of the second signal. Furthermore, a second feedback circuit generates a second feedback signal in response to the second signal. A switching control circuit generates the switching signal in response to the feedback signals.

Abstract: The present invention discloses a switching control circuit for a primary-side controlled power converter. A voltage-waveform detector produces a voltage-feedback signal and a discharge-time signal. A current-waveform detector generates a current-waveform signal by measuring a primary-side switching current. An integrator generates a current-feedback signal by integrating the current-waveform signal with the discharge time. A time constant of the integrator is correlated with the switching frequency, thus the current-feedback signal is proportional to an output current of the power converter. A PWM circuit controls the pulse width of the switching signal in response to the outputs of a voltage-loop error amplifier and a current-loop error amplifier. The output voltage and the maximum output current of the power converter are therefore regulated.

Abstract: A voltage-waveform detector produces a voltage-feedback signal and a discharge-time signal by multi-sampling a voltage signal of a transformer. The discharge-time signal represents a discharge time of a secondary-side switching current. A voltage-loop error amplifier amplifies the voltage-feedback signal and generates a control signal. An off-time modulator correspondingly generates a discharge-current signal and a standby signal in response to the control signal and an under-voltage signal. The under-voltage signal indicates a low supply voltage of the controller. An oscillator produces a pulse signal in response to the discharge-current signal. The pulse signal determines the off-time of the switching signal. A PWM circuit generates the switching signal in response to the pulse signal and the standby signal. The standby signal further controls the off-time of the switching signal and maintains a minimum switching frequency. The switching signal is used for regulating the output of the power supply.

Abstract: A switching regulator includes a switching device to switch a transformer from a primary-side to secondary side. A control circuit generates a switching signal for regulating output of the switching regulator. The control circuit includes a first circuit to generate a first signal and a timing signal by measuring a reflected signal of the transformer. A second circuit produces a second signal by integrating a current signal with the timing signal. The current signal represents a primary-side switching current of the transformer. A first feedback circuit produces a first feedback signal in response to the first signal and the reference signal, in which the reference signal is varied in response to the change of the second signal. Furthermore, a second feedback circuit generates a second feedback signal in response to the second signal. A switching control circuit generates the switching signal in response to the feedback signals.

Abstract: A circuit and a method for detecting a voltage of a transformer are provided. The circuit includes a current output circuit coupled to a winding of a transformer to generate a current signal. A current-to-voltage circuit is coupled to the current output circuit to generate a voltage signal in response to the current signal. A sample-and-hold circuit generates an output signal by sampling the voltage signal. An input voltage is applied to the transformer. The output signal is correlated to the input voltage of the transformer.

Abstract: A circuit for detecting an input voltage of a transformer is provided. The circuit includes a current source circuit coupled to a winding of a transformer. A current-to-voltage circuit is coupled to the current source circuit to generate a first voltage in response to a current outputted from the current source circuit. A sample-and-hold circuit generates an output voltage by sampling the first voltage. The transformer is coupled to the input voltage, and the output voltage is correlated to the input voltage of the transformer.

Abstract: 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.

Abstract: The present invention provides a switching control circuit having a valley voltage detector to achieve the soft switching and improve the efficiency of a power converter. The switching control circuit includes a control circuit coupled to the feedback signal to generate a switching signal. Through an output circuit, the switching signal drives a switching device for switching a transformer and regulating the output of the power converter. The valley voltage detector is coupled to an auxiliary winding of the transformer for generating a control signal in response to the voltage of the transformer. The control signal is used for enabling the switching signal. The switching signal further turns on the switching device in response to a valley voltage across the switching device.

Abstract: The present invention provides a power converter having a phase lock circuit for quasi-resonant soft switching. The power converter includes a first circuit coupled to the feedback signal to generate a switching signal for switching a switching device and regulating the output of the power converter. A second circuit is coupled to an auxiliary winding of the transformer for generating a voltage signal in response to the voltage of the transformer. A phase lock circuit generates a control signal to enable the switching signal in accordance with the voltage signal. The switching signal further turns on the switching device in response to a valley voltage across the switching device.

Abstract: A high-side transistor driver including a driver circuit for generating a driving signal to drive a high-side transistor is provided. A floating supply terminal provides a supply voltage to the driver circuit. A floating ground terminal is connected to a source of the high-side transistor. A bootstrap diode is coupled between the floating supply terminal and a voltage source. A capacitor is connected to the bootstrap diode and is coupled between the floating supply terminal and the floating ground terminal. A high-voltage transistor is used for switching off the driving signal and the high-side transistor in response to an input signal. A speed-up capacitor is coupled to the driver circuit for speeding up the driving signal. Furthermore, the positive feedback circuits in the driver circuit further accelerate the driving signal and save power for the driver circuit.

Abstract: A switching regulator includes a switching device to switch a transformer from a primary-side to secondary side. A control circuit generates a switching signal for regulating output of the switching regulator. The control circuit includes a first circuit to generate a first signal and a timing signal by measuring a reflected signal of the transformer. A second circuit produces a second signal by integrating a current signal with the timing signal. The current signal represents a primary-side switching current of the transformer. A first feedback circuit produces a first feedback signal in response to the first signal and the reference signal, in which the reference signal is varied in response to the change of the second signal. Furthermore, a second feedback circuit generates a second feedback signal in response to the second signal. A switching control circuit generates the switching signal in response to the feedback signals.

Abstract: The present invention discloses a switching control circuit for a primary-side controlled power converter. A voltage-waveform detector produces a voltage-feedback signal and a discharge-time signal. A current-waveform detector generates a current-waveform signal by measuring a primary-side switching current. An integrator generates a current-feedback signal by integrating the current-waveform signal with the discharge time. A time constant of the integrator is correlated with the switching frequency, thus the current-feedback signal is proportional to an output current of the power converter. A PWM circuit controls the pulse width of the switching signal in response to the outputs of a voltage-loop error amplifier and a current-loop error amplifier. The output voltage and the maximum output current of the power converter are therefore regulated.

Abstract: A voltage-waveform detector produces a voltage-feedback signal and a discharge-time signal by multi-sampling a voltage signal of a transformer. The discharge-time signal represents a discharge time of a secondary-side switching current. A voltage-loop error amplifier amplifies the voltage-feedback signal and generates a control signal. An off-time modulator correspondingly generates a discharge-current signal and a standby signal in response to the control signal and an under-voltage signal. The under-voltage signal indicates a low supply voltage of the controller. An oscillator produces a pulse signal in response to the discharge-current signal. The pulse signal determines the off-time of the switching signal. A PWM circuit generates the switching signal in response to the pulse signal and the standby signal. The standby signal further controls the off-time of the switching signal and maintains a minimum switching frequency. The switching signal is used for regulating the output of the power supply.