Abstract: A switching control IC outputs a rectangular wave signal from an output terminal thereof to a driving circuit. A feedback circuit compares a value of a divided voltage of a voltage across output terminals of a switching power supply device with a reference voltage, generates a feedback signal, and inputs the feedback signal into a feedback terminal of the switching control IC. A capacitor and a Zener diode are connected between the feedback terminal and a ground terminal. The Zener diode is selectively connected, and a voltage at the feedback terminal is changed in accordance with the presence of the Zener diode. A voltage at the feedback terminal is detected, and one of a latch method and a hiccup method is selected as a method for an overcurrent protection operation in accordance with the detected voltage.

Abstract: A switching power converter comprises a transformer (110), a switch (108) coupled to the transformer (110), and a switch controller (200) coupled to the switch (108) for generating a switch drive signal (207) to turn on or off the switch (108). The drive current of the switch drive signal (207) is adjusted dynamically according to line or load conditions within a switching cycle and/or over a plurality of switching cycles. The magnitude of the drive current can be dynamically adjusted within a switching cycle and/or over a plurality of switching cycles, in addition to the pulse widths or pulse frequencies of the drive current.

Abstract: A controller for controlling power to a light source includes a first sensing pin, a second sensing pin, a third sensing pin, and a driving pin. The first sensing pin receives a first signal indicating an instant current flowing through an energy storage element. The second sensing pin receives a second signal indicating an average current flowing through the energy storage element. The third sensing pin receives a third signal indicating whether the instant current decreases to a predetermined current level. The driving pin provides a driving signal to a switch to control an average current flowing through the light source to a target current level. The driving signal is generated based on one or more signals selected from the first signal, the second signal and the third signal.

Abstract: A DC-DC converter includes a power switching device and a mode control logic circuit to control the power switching device and generate an ON-pulse. A flip-flop is configured to be set by the mode control logic circuit. A current mode comparator is configured to reset the flip-flop and to compare a signal based upon current flowing through the power switching device with a signal based upon an output voltage of the dual mode flyback DC-DC converter. A transformer is driven by the current mode comparator.

Abstract: A control device includes a first terminal receiving a monitored output voltage and a second terminal transmitting a pulse width modulation (PWM) signal. A converting unit generates an A/D conversion synchronous signal, and an A/D converter samples the monitored output voltage in accordance with the A/D conversion synchronous signal. A pulse oscillator controls a position of a first edge on the PWM signal in accordance with the A/D conversion synchronous signal, and controls a position of a second edge based on the monitored voltage.

Abstract: A circuit for a switched mode power supply having a winding. The circuit comprising: an input configured to receive a winding voltage derived from the winding; a differentiation element configured to differentiate the winding voltage with respect to time in order to determine a derivative signal and compare the derivative signal with a threshold value; a steady state detector configured to set a zero derivative signal when the derivative signal has not exceeded the threshold value for a predetermined period of time, and a logic arrangement configured to identify an end of a demagnetization stroke of the switched mode power supply when the derivative signal crosses a final threshold value after the zero derivative signal has been set.

Abstract: Embodiments of circuits and methods for a switching mode power supply are described in detail herein. In one embodiment, a switching mode power supply includes a transformer having a primary winding and a secondary winding to supply power to a load, a feedback circuit that generates a feedback signal that varies in relation to the load on the secondary winding, a switching circuit coupled to the primary winding to control current flow through the primary winding, and a control circuit coupled to the switching circuit to control the on/off status of switching circuit in response to the feedback signal and the current flow through the primary winding. The control circuit comprises a spectrum shaping circuit configured to generate a spectrum shaping signal in response to the feedback signal. The spectrum shaping signal can then be used to regulate the switching frequency and the spectrum shaping range.

Abstract: A primary side current controller for a power supply is disclosed. The primary side current controller includes a waveform detection unit, a calculation unit, and a switching controller. The waveform detection unit is used for detecting a waveform signal of the power supply and generating a captured signal. The calculation unit is coupled to the waveform detection unit and used for generating a selected voltage according to the captured signal and a feedback signal of the power supply. The switching controller is coupled to the calculation unit and used for generating a modulation signal according to the selected voltage and the feedback signal.

Abstract: A switching control circuit for a switching power converter is provided. The switching control circuit is coupled to a switching device and an auxiliary winding of a transformer. The switching control circuit includes a valley detecting circuit, a valley lock circuit, and a PWM circuit. The valley detecting circuit is coupled to receive a reflected voltage signal from the auxiliary winding of the transformer for outputting a control signal in response to the reflected voltage signal. The valley lock circuit is coupled to receive the control signal for outputting a judging signal in response to the control signal during a first period and a second period following the first period. The PWM circuit outputs a switching signal in response to the judging signal.

Abstract: An integrated circuit for use in a power supply includes a drive signal generator, a first delay, a second delay, a comparator, a first logic, a first short on time detector, and a second logic. The drive signal generator generates a drive signal to control a switch in response to a clock signal. The short on time detector sets the first latch indicating that an on time of the switch is a short on time. The second logic is coupled to detect long pulses of the drive signal to reset the first latch indicating that the on time of the switch is not a short on time. An on time of the drive signal is a short on time if a switch current of the switch exceeds a current limit after a sum of a leading edge blanking period and a current limit delay time period.

Abstract: Provided are a high voltage generating apparatus controlled by a digital control code and a method thereof. The high voltage generating apparatus includes a switching unit for controlling a voltage induced at the secondary coil of a power transformer by an interrupt operation, wherein the interrupt operation interrupts the current flowing through the primary coil of the connected power transformer. A digital controller for controlling the interrupt operation of the switching unit according to the control data. A digital interface for providing the control data to the digital controller is provided. The control data is extracted from the control code transferred using one of a plurality of predetermined communication protocols. The switching unit, digital interface, and digital controller can be implemented in one ASIC (application-specific integrated circuit) chip.

Abstract: An example controller for a switched mode power supply includes a zero-crossing detector and a drive signal generator. The zero-crossing detector is coupled to generate a zero-crossing signal representative of a phase angle of a dimmer output voltage for a half line cycle of the power supply. The drive signal generator controls switching of a switch to regulate an output of the power supply in response to a feedback signal representative of the output. The drive signal generator further controls switching of the switch to adjust dimming of the output of the power supply in response to the phase angle indicated by the zero-crossing signal.

Abstract: A circuit and method of determining the power output for a converter circuit includes determining a time averaged voltage from a rectified voltage of a winding of the transformer and multiplying the time averaged voltage by a constant determined at least in part by an average current of a winding of the transformer. By one approach, a rectified voltage from a primary side of the transformer is time averaged using a filter circuit. The current can be known or preset or controlled by the converter circuit such that the time averaged voltage reading, assuming a constant current, can be compared to a preset voltage such that the voltage reading approximates a power reading for the transformer. By another approach, the time averaged voltage is multiplied by the current to obtain a power output reading.

Abstract: To detect a peak time of an exciting current of a transformer, a primary current corresponding to the peak time, or a variation time of the primary voltage, and to switch a switch after expiration of a predetermined period from the peak time, after the peak time occurs. A control apparatus 1 is applied to a power conversion circuit 2 which includes a switch circuit 23 including one switch or a plurality of switches and a transformer 21. The control apparatus includes: an output voltage detector 11 detecting a value of an output voltage of the power conversion circuit; an exciting current peak time generator 12 detecting a peak time of an exciting current of the transformer; a timing generator 13 generating a switching timing of the one switch or the plurality of switches. The timing generator 13 generates the switching timing of the one switch or the plurality of switches on the basis of the output voltage and the peak time.

Abstract: A method of controlling an output voltage of a pulse width modulation (PWM) converter with a PWM signal driving a power switch of the converter may include using a comparator to compare a reference voltage with a scaled output voltage of the converter, incrementing or decrementing an up/down counter at each pulse of a clock signal applied to the counter depending on a state of the comparator, and controlling the comparator to generate the PWM signal with a control voltage selected from a look-up table using a value of the counter.

Abstract: A circuit regulator is used to generate a pulse-width-modulation signal, so as to control a power to be selectively input or not input to a primary side of a switching power supply. The circuit regulator includes a synchronous timing pulse generation circuit, outputs a starting pulse after performing signal process of time delay, timing pulse regulation, and synchronization control on a pulse-width-modulation signal and a discharging time signal of a secondary side, and accordingly effectively controls a pulse starting time of the pulse-width-modulation signal. Therefore, the synchronous timing pulse generation circuit can be applied to the circuit regulator, so as to further effectively prevent an inductor current of the switching power supply from entering a Continuous Conduction Mode (CCM).

Abstract: A low-cost PFC converter capable of detecting an inductor current including a DC component and performing appropriate correction of a power factor with low loss includes a diode bridge that rectifies an AC voltage input from an AC input power supply Vac, a series circuit including an inductor and a switching element, a rectifying and smoothing circuit that is connected in parallel to the switching element and that includes a diode and a smoothing capacitor, and a digital signal processing circuit that performs on/off control on the switching element so that an input current input from the AC input power supply Vac has a similar waveform with respect to an AC voltage. A current flowing through the inductor during an off period of the switching element is detected using a current detecting resistor, and a decreased voltage of the current detecting resistor is sampled at the middle of the off period of the switching element, thereby detecting an average value of the input current.

Abstract: An integrated circuit for use in a power supply includes a drive signal generator, a first delay, a second delay, a comparator, a first logic, a first short on time detector, and a second logic. The drive signal generator generates a drive signal to control a switch in response to a clock signal. The short on time detector sets the first latch indicating that an on time of the switch is a short on time. The second logic is coupled to detect long pulses of the drive signal to reset the first latch indicating that the on time of the switch is not a short on time. An on time of the drive signal is a short on time if a switch current of the switch exceeds a current limit after a sum of a leading edge blanking period and a current limit delay time period.

Abstract: An embodiment provides a control method capable of controlling a switching-mode power supply to provide an output power source. The switching-mode power supply has a winding coupled to an input power source and controlled by a switch to be energized or de-energized. The maximum current peak through the winding is set to be a predetermined value. A discharge time of the winding in a switching cycle period is detected. The switching cycle period of the switch is controlled to keep the ratio of the discharge time to the switching cycle period as a constant.

Abstract: Disclosed include a control circuit adapted for a power controller powered by an operation voltage. When the operation voltage exceeds an over-voltage reference, the power controller stops power conversion provided by a power converter. The control circuit comprises a slope detector detecting a variation slope of the operation voltage. When the variation slope exceeds a drop rate, the slope detector recovers the power conversion. When the power conversion is recovered the power controller compares the operation voltage with the over-voltage reference.

Abstract: In a switching power supply device which intermittently executes a switching operation, a power loss which occurs in resumption of the switching operation is reduced. A semiconductor device works as a control circuit for the switching power supply device, and includes: an intermittent oscillation control circuit which alternately gives an instruction for execution and suspension of the switching operation of a switching element; a bottom detecting circuit which detects a bottom of a ringing voltage that develops when the switching element is OFF; a bottom-monitoring time period timing circuit which times a bottom-monitoring time period starting as soon as the instruction for the execution of the switching operation is given; and a turn-on control circuit which turns ON, before the timing of the bottom-monitoring time period ends, the switching element only when the bottom of the ringing voltage is detected.

Abstract: An example method of controlling a power supply to have a constant current output includes receiving an input current sense signal, an input voltage sense signal, and an output voltage sense signal. A control signal is then generated to control switching of a switch of the power supply to regulate an output current of the power supply. The generating of the control signal includes integrating the input current sense signal during a switching period of the control signal to generate an integrated signal representative of a charge taken from an input voltage source of the power supply. Generating the control signal also includes controlling the switching of the switch such that the integrated signal is proportional to a ratio of the output voltage sense signal to the input voltage sense signal.

Abstract: System and method for regulating a power converter. The system includes a first comparator configured to receive a first input signal and a second input signal and generate a first comparison signal based on at least information associated with the first input signal and the second input signal, a pulse-width-modulation generator configured to receive at least the first comparison signal and generate a modulation signal based on at least information associated with the first comparison signal, a driver component configured to receive the modulation signal and output a drive signal to a switch to adjust a primary current flowing through a primary winding of the power converter, and a voltage-change-rate detection component configured to sample the feedback signal to generate a first sampled signal for a first modulation period and to sample the feedback signal to generate a second sampled signal for a second modulation period.

Abstract: A digital device generates a fixed duty cycle signal with an internal oscillator after a Power-On-Reset (POR). This fixed duty cycle signal is output on a signal pin that normally is used for a PWM control signal. The fixed duty cycle signal is used to stimulate the voltage generation circuits so as to power up the digital device for initialization thereof. Once the digital device has powered-up and initialized, the digital device switches over to normal operation for control of the power system.

Abstract: A digital dynamic delay modulator and the method thereof are applied to a flyback converter. A first input voltage signal from the flyback converter is received and compared with a threshold voltage to determine whether a counting condition is matched. When the counting condition is matched, an integer predetermined count number is counted to determine a delay time. After finishing the counting, a first output signal is generated to turn on a switching device for the flyback converter. The slope of the first input voltage signal is detected when the switching device is turned on, and the slope is used to adjust the count number with integer increment/decrement. Therefore, the delay time for switching the flyback converter can be precisely controlled in digital and dynamic manner.

Abstract: A switching regulator of a power converter is provided and includes a feedback-input circuit, a programming circuit, and a peak-current-threshold circuit. The feedback-input circuit is coupled to a terminal of the switching regulator for receiving a feedback signal. The feedback-input circuit is operated in a first range of a terminal signal. The programming circuit is coupled to the terminal for generating a programming signal. The programming signal is operated in a second range of the feedback signal. The peak-current-threshold circuit generates a threshold signal in accordance with the programming signal. The feedback signal is coupled to regulate the output of the power converter, and the threshold signal is coupled to limit a peak switching current of the power converter.

Abstract: Method and system for efficient power control with multiple modes. According to an embodiment, the present invention provides a power system with selectable power modes. The power system includes a first terminal for outputting energy, and the first terminal is electrically coupled to a load. The system also includes a pulse-frequency modulation (PFM) component that is configured to adjust a pulse frequency based on the load. The system additionally includes a pulse-width modulation (PWM) component that is configured to adjust a pulse width based on the load. The system further includes a switch that is electrically coupled to the first terminal. Also, the system includes a control component, the control component being configured to provide a control signal that is capable of causing the switch to be turned on or off. The control signal is associated with an output of the PWM component and the pulse width if an output is greater than a predetermined value.

Abstract: A semiconductor device providing a control circuit for controlling a switching power supply apparatus includes: an intermittent-oscillation control circuit which outputs an enable signal providing instructions to execute and suspend switching alternately; a turn-on control circuit which changes between an execution state and a suspension state of the switching according to the enable signal, and outputs, only in the execution state, a turn-on signal which turns on the switching element with a switching period; and an intermittent-oscillation frequency control circuit which causes the turn-on control circuit to delay the changing between the execution state and the suspension state so that an intermittence period including periods during which the turn-on control circuit is in the execution state and the turn-on control circuit is in the suspension state falls outside of a specific time range. Intermittent oscillation is thus operated out of a specific frequency band within an audible frequency range.

Abstract: According to the invention, a blocking oscillator type converter circuit functions with a transformator that only comprises a primary winding and a secondary winding. Said transformator does not comprise a return coupling winding for the blocking oscillator. The control voltage of the oscillator is derived from the primary voltage of the transformator during the free-wheeling phase. The invention also relates to a voltage monitoring circuit that works independently from the oscillator, the output voltage of the oscillator being repressed when the voltage on the output of the blocking oscillator is too high. A flow monitoring circuit functions independently from the oscillator and the voltage monitoring circuit and suppresses the impulses for the power transistor when the power on the output side exceeds a predetermined measurement.

Abstract: An integrated circuit for use in a power supply includes a drive signal generator, a short on time detector, and an oscillator. The drive signal generator generates a drive signal in response to a clock signal. The short on time detector provides an output indicating that consecutive on times of the drive signal are short on times. An on time of the drive signal is a short on time if a switch current of the switch exceeds a current limit after a leading edge blanking period and if the on time of the switch is less than or equal to a sum of the leading edge blanking period and a current limit delay time period. The oscillator generates the clock signal and changes a frequency of the clock signal from a first frequency to a lower second frequency in response to the output of the short on time detector.

Abstract: An example power supply includes an energy transfer element, a switch and a controller. The controller includes a logic circuit and a constant current control circuit. The logic circuit generates a drive signal to control the switch in response to a control signal. The constant current control circuit generates the control signal in response to a received input current sense signal, input voltage sense signal, and output voltage sense signal. An integrator included in the constant current control circuit integrates the input current sense signal to generate an integrated signal representative of a charge taken from the input voltage source. The constant current control circuit is adapted to generate the control signal to provide a constant current at the output of the power supply such that the integrated signal is proportional to a ratio of the output voltage sense signal to the input voltage sense signal.

Abstract: The present invention relates to a power supply device generating an output power by using an AC line voltage generated through rectification of an AC input, and a driving method thereof. The power supply device controls the switching operation of the power switch by using a sensing voltage corresponding to the drain current flowing to the power switch and the feedback voltage corresponding to the output voltage. The power supply device controls the feedback current every switching cycle to generate a threshold voltage, and compares the sensing voltage and the threshold voltage to control the turn-off of the power switch. The feedback current includes the first current to generate the feedback voltage, and the threshold voltage follows a curved line waveform in which the increasing slope is decreased during the switching cycle.

Abstract: A switching regulator with frequency limitation comprises a switch, a current sensing circuit, a voltage feedback circuit, a control circuit and a frequency limitation circuit. The current sensing circuit senses the current flowing through the switch and generating a current sensing signal representative of it. The voltage feedback circuit senses the output signal of the switching regulator and generates a feedback signal accordingly. The control circuit compares the current sensing signal with the feedback signal and turns off the switch based on the comparison result. The frequency limitation circuit is electrically coupled to the control circuit to limit the switching frequency of the switch.

Abstract: A power supply controller is disclosed. An example power supply controller includes an input voltage sense input coupled to sense an input voltage sense signal representative of an input voltage of a power supply. An output voltage sense input is coupled to sense an output voltage sense signal representative of an output voltage of the power supply. A current limit circuit is coupled to generate a current limit signal. The current limit signal is varied relative to a first ratio representative of a ratio of a product of the input voltage and a scaled output voltage of the power supply, to a sum of the input voltage and the scaled output voltage of the power supply. A drive signal generator is coupled to generate a drive signal in response to the current limit signal to drive the power switch of the power supply to limit an output power of the power supply in response to the input voltage.

Abstract: An electronic apparatus includes, for example, a circuit board with an electronic component and a piezoelectric element, a reference potential pattern that gives a reference potential to at least one of the electronic component and the piezoelectric element, and a solder land connected to the reference potential pattern. On the circuit board, the electronic component is located on a downstream side in a transport direction of the circuit board during mounting of the piezoelectric element and the electronic component on the solder land, and the piezoelectric element is located on an upstream side in the transport direction.

Abstract: In an image forming apparatus, a monitoring unit monitors whether a returning factor required to switch an operational state of the apparatus from a power-saving mode to an operating mode is generated, an antenna unit receives external electrical wave, a power generation unit generates electricity from the received electrical wave and supplies the electricity to the monitoring unit, and a controlling unit switches the operational state of the apparatus from the power-saving mode to the operating mode when the monitoring unit detects generation of a returning factor.

Abstract: An example controller for use in a power converter includes an oscillator and a logic circuit. The oscillator is to be coupled to a switch of the power converter and determines a switching cycle period of the switch. The logic circuit is also to be coupled to the switch to control a duty cycle of the switch in response to a magnitude of a feedback signal to regulate an output of the power converter. The logic circuit controls the duty cycle of the switch such that a control loop gain of the power converter is substantially constant during a transition of the controller between duty cycle control modes.

Abstract: Disclosed are circuits and methods for use in a control circuit of a switching mode power supply for turning on a switching device in the switching mode power supply when the voltage across the switching device is at a minimum. A voltage detector is provided for detecting the voltage across the switching device to produce a detection voltage which is a function of the voltage across the switching device, and circuit arrangement is used to predict a valley timing for the voltage across the switching device by evaluating the time period that the detection voltage falls down from a first threshold to a second threshold.

Abstract: A digital signal processing circuit which performs average current control is disposed on a secondary side of a transformer of an isolated DC-DC converter, and a switching control signal output from the digital signal processing circuit is transmitted to a switching element included in a power factor correction converter through an isolated drive circuit. The digital signal processing circuit obtains an average value of currents supplied to an inductor in accordance with a voltage output from a bias winding of the inductor or an output from a secondary side of a current transformer which detects a drain current of the switching element. Furthermore, the average value of the currents corresponds to a waveform (full-wave rectification sine wave) of an input voltage Vi.

Abstract: An adaptive pulse width control power conversion device includes a pulse width adjustable pulse frequency module (PFM) control circuit, a pulse width modulation (PWM) control circuit, a PWM/PFM switching unit, a switching circuit, and a load status detection circuit. When the power conversion device is to be switched from a PWM mode to a PFM mode, pulse width of a series of PFM control signals is sequentially adjusted from a low value to a high value according to a predetermined pulse width increment until an optimum pulse width is determined and thereafter, an output voltage is supplied to a load in the PFM mode, whereby ripple of output voltage in the PFM mode can be improved and improved stability of output of the power conversion device is realized.

Abstract: A flyback converter having a leading edge blanking (LEB) element keeps detecting whether or not primary-side current of the flyback converter reaches a predetermined threshold, beyond which the flyback converter could be damaged, in a predetermined LEB time corresponding to a leading edge of primary-side current. The flyback converter is turned off when the primary-side current exceeds the predetermined threshold.

Abstract: In accordance with the teachings described herein, systems and methods are provided for a switching mode power supply. In one example, the switching mode power supply may include a transformer, a switching circuit and a switching control circuit. The transformer receives a DC input voltage on a primary winding and generates a DC output voltage on a secondary winding. The switching circuit, which may include a MOSFET switch, is coupled to the transformer and is configured to switch the transformer on and off. The switching control circuit generates a switching control signal to control the switching circuit in order to regulate the DC output voltage of the transformer.

Abstract: Control accuracy with regard to variation of output voltage is improved. A direct current converter unit (20) that steps up or steps down an input voltage (Vin) to be outputted, and a control unit (10) that controls output voltage (Vout) of the direct current converter unit (20) by a pulse width modulation signal (Sw) are provided; the direct current converter unit (20) is provided with a voltage detection circuit (24) that monitors the output voltage (Vout); the control unit (10) is provided with an A/D converter (13) that samples a monitored voltage value (Vd) of the voltage detection circuit (24); and a pulse oscillator (14) that controls the position of one edge by an A/D conversion synchronous signal (Ss) indicating the start of sampling by the A/D converter (13), and generates the pulse width modulation signal (Sw), which controls the position of the other edge based on the monitored voltage value (Vd).

Abstract: An example controller for use in a power supply regulator includes a switch signal generator, a modulation circuit, and a multi-cycle modulator circuit. The modulation circuit modulates the period of a modulation switching signal when an equivalent switching frequency is greater than a reference frequency and fixes the switching period when the equivalent switching frequency is less than the reference frequency. The multi-cycle modulator circuit enables the switch signal generator to provide a switch signal uninterrupted if the equivalent switching frequency is greater than the reference frequency and disables the switch signal generator for a first time period and then enables the switch signal generator for a second time period when the equivalent frequency is less than the reference frequency. The multi-cycle modulator circuit varies the first time period to regulate the output.

Abstract: A switch controller is disclosed that adaptively controls the operating frequency of a switching power converter in order to improve one-time load response and repetitive dynamic load responses. During a transition from a high load to low load condition, the switch controller clamps the operating frequency of the switching power converter at an intermediate frequency for a period of time before allowing the operating frequency to return to a frequency associated with the low load condition. The clamped frequency is higher than the frequency associated with the low load condition thereby allowing improved response to a subsequent load change to a high load condition. Thus, the system improves dynamic load response without compromising no-load power consumption.

Abstract: An embodiment of a power-supply controller comprises a switching-control circuit, an error amplifier, and a signal generator. The switching-control circuit is operable to control a switch coupled to a primary winding of a transformer, and the error amplifier has a first input node operable to receive a feedback signal, a second input node operable to receive a comparison signal, and an output node operable to provide a control signal to the switching-control circuit. The signal generator is operable to generate either the feedback signal or the comparison signal in response to a compensation signal that is isolated from a secondary winding of the transformer and that is proportional to a load current through a conductor disposed between the secondary winding and a load.

Abstract: This invention provides a control circuit for burst switching of a power converter comprising: an adaptive circuit generating an adaptive threshold in response to a feedback signal correlated to an output load of the power converter; and a switching circuit generating a switching signal to switch a transformer of the power converter in accordance with the adaptive threshold and the feedback signal for regulating an output of the power converter.

Abstract: An example power supply controller includes a regulation circuit, a current sense circuit, and a response circuit. The regulation circuit is coupled to regulate a sense terminal to a voltage level. The current sense circuit is coupled to the sense terminal to sense a current through the sense terminal a measurement delay period after a magnitude of the current through the sense terminal reaches a first threshold current level. The response circuit is coupled to the sense circuit and is responsive to the current through the sense terminal only after the measurement delay period.

Abstract: A frequency limitation method used in quasi-resonant control of a switching regulator is disclosed. The switching frequency is limited through setting a minimum time limit, such as a minimum switching period or a minimum OFF time. The minimum time limit may be a first time limit or a second time limit. The minimum time limit is changed into another value if the minimum voltage point approaches the minimum time limit point, so as to eliminate the audible noise.

Abstract: A flyback power system includes a rectifier and filter circuit, a pulse width modulation (PWM) controller, a feedback circuit, a master converter circuit, a slave converter circuit, and a slave converter control circuit. The master converter circuit continuously converts power signals from the rectifier and filter circuit into first direct current (DC) power signals to drive load according to PWM signals of the PWM controller when the flyback power system powered on. The slave converter circuit converts the power signals from the rectifier and filter circuit into second DC power signals according to the PWM signals, and superposes the second DC power signals to the first DC power signals to drive the load when the load is heavy. The slave converter control circuit detects whether the load is heavy, and controls the PWM signals whether to input into the slave converter circuit according to a state of the load.