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: A dual-mode switching power control device includes an electric transformer, a PWM driving controller, a switching transistor, an isolation element, an output diode and an output capacitor. The PWM driving controller is connected to the switching transistor coupled to the electric transformer. The first side inductor of the electric transformer and the switching transistor are coupled to an input power, and the second side inductor of the electric transformer is coupled to the output diode. The output capacitor and a load are connected in series. The output power is converted into a feedback signal by the isolation element. The PWM driving controller determines to perform DCM or CCM based on the feedback signal to control the current flowing through the electric transformer, and the output power is generated. Therefore, the efficiency of power conversion is improved and is suitable for high power applications.

Abstract: An example controller for use in a power converter includes an oscillator that is to be coupled to a switch of the power converter to determine a switching cycle period of the switch. The controller also includes means for controlling a duty cycle of the switch to regulate an output of the power converter and for maintaining a substantially constant rate of change of the duty cycle with respect to changes in a magnitude of a feedback signal as the controller transitions between duty cycle control modes such that a control loop gain of the power converter is substantially constant during the transition.

Abstract: A control circuit adjusts the output of a power converter by controlling a power switch, in which a primary side of a transformer, the power switch and a sensing resistor are connected in series to ground. The control circuit includes a peak current emulating unit, an error amplifier, a comparator, and a control signal generator. The peak current emulating unit samples sampling voltages from the sensing resistor and obtains a real current sensing voltage and an current sensing voltage using the sampling voltages. The error amplifier receives a fixed reference voltage and a DC voltage generated from the output of the power converter, and generates an error signal. The comparator receives the real current sensing voltage and the error signal and generates a transition signal. The control signal generator receives the transition signal and generates a control signal for controlling the power switch.

Abstract: A switch mode power supply having an output terminal configured to provide an output voltage, the switch mode power supply has a first switch and a control circuit. The control circuit is configured to provide a switching control signal to control the first switch. The control circuit is configured to provide the switching control signal based on a first pulse signal having a first frequency and a second frequency for a light load condition, and the control circuit is configured to provide the switching control signal based on a second pulse signal for a non-light load condition.

Abstract: An improved valley-mode switching (VMS) scheme and circuitry for implementing the improved VMS switching scheme in a switch-mode power converter are disclosed. For a given switching cycle, a desired switch turn-on time is determined based on a pulse width modulation, pulse frequency modulation, or other suitable power converter control scheme. Also, one or more times corresponding to local minimums (valleys) are predicted for the voltage across a power switch of the switching power converter. The power switch is turned on at a valley immediately subsequent or otherwise subsequent to the desired switch time determined according to the power converter control scheme. Thus, the improved VMS scheme enables low-voltage switch operation to reduce switching loss and EMI noise without restricting the control scheme of the power converter.

Abstract: A motor control apparatus includes a power conversion unit which supplies drive power to a motor, a current detection unit which detects the value of a current flowing from the power conversion unit to the motor, a delta-sigma modulation AD converter to which the current value detected by the current detection unit is input as analog data, and which includes a modulator and a plurality of digital low-pass filters and outputs digital data in accordance with the filter characteristics of the respective digital low-pass filters, and a command generating unit which is connected to the digital low-pass filter to be used for motor drive control among the plurality of digital low-pass filters, and which generates a drive command to the power conversion unit by using the digital data output from the motor drive controlling digital low-pass filter.

Abstract: An example controller includes a feedback circuit coupled to provide feedback information representative of an output of the power converter during at least a portion of an OFF time of a power switch. A sense input receives a sense signal that is representative of a reflected voltage representative of an input voltage of the power converter during at least a portion of an ON time of the power switch. A fault detector is to be coupled to detect a fault condition in response to the reflected voltage being below a fault threshold for a fault period of time. A control is coupled to the fault detector and the feedback circuit to control switching of the power switch to regulate the output of the power converter in response to the feedback information and inhibit the switching of the power switch in response to the fault detector detecting the fault condition.

Abstract: A controller of a power converter is provided. The controller includes a feedback circuit, an output circuit, and a clamping circuit. The feedback circuit generates a feedback signal in accordance with output of the power converter. The output circuit generates a switching signal in accordance with the feedback signal for regulating the output of the power converter. The clamping circuit limits the feedback signal under a first level for a first load condition and limits the feedback signal under a second level for a second load condition. The clamping circuit includes a timer circuit. The timer circuit determines a slew rate of the feedback signal for increasing the feedback signal from the first level to the second level, and the second level is higher than the first level.

Abstract: An example integrated circuit controller for a power converter includes a digital peak detector and a switching block. The digital peak detector is coupled to output a digital count signal representative of a peak input voltage of the power converter. The switching block is coupled to control switching of a power switch of the power converter to regulate an output of the power converter. The switching block is further coupled to control the switching of the power switch in response to the digital count signal.

Abstract: A system for testing the existing protection schemes of a power converter. The system simulates the voltage regulator producing a voltage level below an under-voltage threshold. The system simulates the voltage regulator producing a voltage level above an over-voltage threshold. The system simulates a short in the power converter pulling down the input bus. The system simulates a short in the power converter pulling down the output bus. The system measures the system responses to these simulations against responses of a properly operating system and determines if the power converter's protection schemes are operating correctly.

Abstract: System and method for regulating a power conversion system. A system controller for regulating a power conversion system includes a first controller terminal, a second controller terminal and a third controller terminal. The system controller is configured to receive an input signal at the first controller terminal and turn on or off a switch based on at least information associated with the input signal to adjust a primary current flowing through a primary winding of the power conversion system, receive a first signal at the second controller terminal from the switch, and charge a capacitor through the third controller terminal in response to the first signal.

Abstract: An on/off controller device includes a control circuit to generate a control signal to switch a power switch between an on state and an off state to transfer energy from a primary side to a secondary side of a switched mode power supply. A comparator is coupled to generate an enable signal that enables and disables the switching of the power switch by the control circuit. The comparator compares a feedback signal with a variable threshold and switches the enable signal between enabling and disabling the switching of the power switch. The variable threshold is modulated to increase a fundamental frequency of the switching of the power switch by the control circuit. The variable threshold is modulated with a fixed amplitude pulse that is combined with a second threshold to modulate the variable threshold between a first higher value and a second lower value.

Abstract: An example controller for a power converter includes a track and hold circuit, a sample and hold circuit, and drive logic. The track and hold circuit receives a signal from a terminal of the controller that is representative of an output voltage of the power converter. The track and hold circuit includes a first capacitor that provides a first voltage that tracks the signal and then holds the first voltage. The sample and hold circuit samples the first voltage when the first voltage is held on the first capacitor. The sample and hold circuit includes a second capacitor coupled to hold a second voltage representative of the first voltage after a sample period, where the second capacitor has a capacitance value larger than that of the first capacitor. The drive logic controls the first switch to regulate an output of the power converter in response to the second voltage.

Abstract: A switching power-supply device comprises: a transformer; a switching element connected in series with a primary coil; an output voltage generation circuit to generate an output voltage from a voltage generated in a secondary coil; a control circuit power-supply-voltage generation circuit to generate a power-supply voltage from a voltage generated in an auxiliary coil; a feedback control circuit to control an ON width of the switching element by using the voltage generated in the auxiliary coil; a voltage reduction detection circuit to output a pulse signal to the secondary coil when a reduction of the output voltage is detected; a voltage-reduction-signal detection circuit to detect the voltage reduction signal transmitted to the primary coil from the secondary coil; and a trigger circuit to output a trigger signal to turn on the switching element when the voltage reduction signal is detected by the voltage-reduction-signal detection circuit.

Abstract: An exemplary embodiment of a power converter is provided. The power converter includes a transformer, a power device, a switching controller, and a capacitor. The power device is coupled to the transformer for switching the transformer to product output of the power converter. The switching controller receives a feedback signal for generating a switching signal coupled to drive the power device. An input circuit of the switching controller is coupled to the transformer to sample an input signal for generating the feedback signal, and the input signal is correlated to the output of the power converter. The capacitor is coupled to the switching controller to provide frequency compensation for a feedback loop of the power converter. Input of the power converter is without an electrolytic capacitor, and a maximum output current of the power converter is a constant current.

Abstract: Disclosed is flyback converter having a controller that performs a startup switching process when the flyback converter is powered up, and then performs normal switching afterward. The controller includes a pulse generator to generate a control signal for normal switching. During startup switching, the controller may generate a control signal by output every Nth pulse from the pulse generator. In another embodiment, the controller may generate pulses based on a sense signal provided from an input section of the flyback converter.

Abstract: A power converting device includes a transformer, a first switch coupled to a primary winding of the transformer, a PWM controller which generates a first PWM signal for controlling conduction and non-conduction of the first switch and which generates a control signal that leads the first PWM signal, a rectifier-filter circuit which rectifies an induced voltage generated by a secondary winding of the transformer, a second switch coupled to the secondary winding, and a synchronous rectifier controller which controls conduction and non-conduction of the second switch, and which controls, according to the control signal, the second switch to become non-conductive prior to conduction of the first switch.

Abstract: A control circuit controlling the driving of a switching device includes an under voltage limiting operation circuit stopping the operation of the control circuit when a power supply voltage supplied from the auxiliary winding of an insulating transformer becomes lower than a predetermined power supply lower limit voltage, an FB voltage decision circuit stopping the driving of the switching device when a feedback voltage indicating the state of a load becomes lower than the predetermined threshold value, a flip-flop brought into a set state by an output of the FB voltage decision circuit and a reset state when the power supply voltage exceeds the voltage ensuring the normal operation of the control circuit, and a switching circuit to set the power supply lower limit voltage in the under voltage limiting operation circuit, lower than that of the normal operation when the flip-flop is set.

Abstract: A power converter includes an energy transfer element and a power switch coupled the energy transfer element and an input of the power converter. A control circuit is coupled to generate a switching signal to control switching of the power switch in response to a feedback signal representative of an output of the power converter. A programming interface circuit is coupled to the control circuit and a coupling switcher coupled to the programming interface circuit. A programming terminal is selectively coupled to the programming interface circuit through the coupling switcher. A programming circuit coupled to the programming terminal is coupled to the programming interface circuit through the coupling switcher during a startup programming condition and during a fault condition of the power converter, and is decoupled from the programming interface circuit by the coupling switcher during a normal operating condition of the power converter.

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: A power supply device including a transformer having a primary winding and a secondary winding, and a switching element connected to the primary winding configured to drive the switching element to output voltage from the secondary winding includes a control unit configured to drive the switching element such that the switching element is turned on and, in which, in a case where the control unit performs an intermittent drive operation which repeats a period for which the switching element is driven and a period for which the drive of the switching element is stopped, in which the control unit drives the switching element such that the switching element is turned off before the voltage according to the current flowing to the primary winding reaches the voltage output from the secondary winding in the period for which the switching element is driven.

Abstract: An example power supply controller includes a signal separator circuit that generates a feedback signal. An error signal generator generates an error signal in response to the feedback signal. A control circuit generates a drive signal in response to the error signal. The drive signal controls switching of a switch. A multi-cycle modulation circuit is included in the control circuit and generates a skip signal in response to a start skip signal, a stop skip signal and a skip mask signal. The skip mask signal is generated in response to the skip signal. The start skip and stop skip signals cause the drive signal to start skipping or stop skipping, respectively, on-time intervals of cycles. The skip mask signal disables the start skip signal from causing the drive signal to start skipping the on-time intervals of cycles.

Abstract: A control circuit of a power converter is provided. It comprises a signal generation circuit generating an oscillation signal in accordance with an output load. A PWM circuit generates a switching signal according to a voltage-loop signal, a current-loop signal and the oscillation signal for regulating an output of the power converter. A regulation circuit receives a compensation signal for an output cable compensation and a wake-up. The compensation signal is coupled to increase a switching frequency of the switching signal once the output of the power converter is lower than a low-voltage threshold. The control circuit reduces the voltage drop of the output when the output load is changed.

Abstract: A frequency limitation method used in a quasi-resonant controlled switching regulator is disclosed. The switching frequency is limited by setting a minimum time period, such as a minimum switching period or a minimum OFF time period. The minimum time period is varying according to the difference between the minimum time period of the previous cycle and an offset value, so as to eliminate the audible noise caused by the frequency hopping when the minimum OFF time period is close to the valley of a quasi-resonant signal.

Abstract: Methods, systems, and devices are described for an adjustment module that interacts with a parameter detection module to provide a threshold value for initiating switching of a switching module in a cyclical electronic system. Aspects of the present disclosure provide a switching module used in conjunction with an inductor that is coupled with the switching module. The threshold voltage for switching the switching module may be adjusted to provide switching at substantially zero volts while maintaining sufficient energy in the inductor to drive the voltage at a switching element in the switching module to zero volts. Such auto-adjustment circuits may allow for enhanced efficiency in cyclical electronic systems. The output of an up/down counter may be used to set another parameter that effects the performance of the cyclical electronic system in order to enhance the performance of the cyclical electronic system.

Abstract: A controller for regulating an output of a power supply includes a logic block and an oscillator. The logic block generates the drive signal to control switching of a power switch in response to a clock signal. The clock signal has a frequency that decreases responsive to a time period of the drive signal, where a decrease in the time period of the drive signal represents an increase in an input voltage of the power supply. The oscillator is coupled to generate the clock signal in response to a waveform having an amplitude swing. The oscillator alters the waveform in response to the time period of the drive signal.

Abstract: A pulse modulator generates a pulse modulation signal SPM having a duty ratio which is adjusted according to a feedback voltage Vfb that corresponds to the output voltage VOUT of a DC/DC converter. A second oscillator generates a second cyclic signal which is asserted with each of a predetermined second period. A light load detection circuit generates a light load detection signal which is asserted when the feedback voltage Vfb becomes lower than a first threshold voltage. A driving circuit drives a switching transistor according to the pulse modulation signal SPM, Furthermore, the driving circuit suspends the driving of the switching transistor during a period until the second cyclic signal is next asserted after the light load detection signal is asserted.

Abstract: One controller for a power supply includes an oscillator, a first circuit, a counter, and a pause circuit. The first circuit generates a drive signal to control switching of a switch to regulate an output of the power supply. The first circuit initiates an on time period of the switch in response to both a clock signal of the oscillator and an enable signal that is generated in response to a feedback signal of the power supply. The counter receives the enable signal and generates an output signal when the counter reaches a count value indicating that the enable signal has been idle for an amount of time. The pause circuit generates a pause signal in response to the output signal of the counter. The oscillator is paused in response to the pause signal and a maximum on time period of the switch is extended while the oscillator is paused.

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: In one aspect, a power supply includes an energy transfer element, a switch, a feedback circuit, a comparator, a state machine, and a control circuit. The feedback circuit generates a feedback signal representative of an output level of the power supply. The comparator provides a feedback state signal having a first feedback state that represents the output level of the power supply being above a threshold level and a second feedback state that represents the output level being below the threshold level. The state machine selectively modulates a first signal in response to the feedback state signal, where the first signal is the feedback signal or the threshold value signal. The control circuit is coupled to control switching of the switch to regulate the output level of the power supply in response to the feedback state signal.

Abstract: A power converter includes an energy transfer element coupled between a power converter input and a power converter output. A power switch is coupled to the energy transfer element and the power converter input. A feedback sampling circuit is coupled to receive a feedback signal representative of the power converter output to generate at least one feedback signal sample during each switching cycle. A switch conduction scheduling circuit is coupled to set a number of enabled cycles and a number of disabled cycles of the power switch in a plurality of future switching cycles in response to the feedback signal samples for each present switching cycle and one or more past switching cycles. A switch conduction control circuit is coupled to enable or disable conduction of the power switch during a switching cycle to control an amount of energy transferred from the power converter input to the power converter output.

Abstract: System and method for regulating an output current of a power conversion system. An example system controller for regulating an output current of a power conversion system includes a driving component, a demagnetization detector, a current-regulation component, and a signal processing component. The driving component is configured to output a drive signal to a switch in order to affect a primary current flowing through a primary winding of the power conversion system. The demagnetization detector is configured to receive a feedback signal associated with an output voltage of the power conversion system and generate a detection signal based on at least information associated with the feedback signal. The current-regulation component is configured to receive the drive signal, the detection signal and a current-sensing signal and output a current-regulation signal based on at least information associated with the drive signal, the detection signal, and the current sensing signal.

Abstract: A semiconductor control device can include a current detection signal input terminal, a feedback signal input terminal, a driving signal output terminal and a voltage adjusting circuit that delivers a voltage similar to a voltage of a primary winding of the flyback transformer to the current detection signal input terminal. The device can also include an oscillator circuit connected to the feedback signal input terminal; a one-shot circuit connected to the oscillator circuit, an RS flip-flop circuit that generates a driving signal to be delivered to the driving signal output terminal. A bottom detection section can receive a one-shot signal from the one-shot circuit, the current detection signal, and an output signal from the RS flip-flop circuit, and detect a bottom of the current detection signal to set the RS flip-flop circuit based on the detected bottom detection signal.

Abstract: A power supply control circuit includes a threshold detection circuit coupled to a first terminal to measure a signal at the first terminal during a duration of an initialization period after a fourth terminal has been charged to a supply threshold value. A regulator circuit is coupled between a second terminal and the fourth terminal to charge the fourth terminal to the supply threshold value during the initialization period of the power supply control circuit. A selection circuit is coupled to the threshold detection circuit to select a parameter/mode in response to the signal measured at the first terminal. The first terminal is further coupled to receive one or more additional signals during normal operation at times other than the initialization period to provide at least one additional function for the power supply control circuit after the initialization period is complete.

Abstract: The present invention provides a switched-mode power converter with regulation demand pulses sent across a galvanic isolation barrier.

Abstract: A control circuit and a method for controlling a power converter are provided. The method for controlling the power converter includes the following steps. A detection signal is received from the secondary side of the power transformer and a first switching signal is generated in accordance with the detection signal. A second switching signal is generated in accordance with the first switching signal. A voltage signal is generated in accordance with the second switching signal. A comparison signal is generated in accordance with the first switching signal and the second switching signal. The voltage signal and the comparison signal are compared for outputting a comparison result. A gate signal is generated in accordance with the detection signal and the comparison result to control on and off states of a synchronization switch.

Abstract: Embodiments disclose control methods and control apparatuses for a switched mode power supply. The switched mode power supply comprises a current-controllable device. A driving current is provided to turn ON the current-controllable device. A conduction current passing through the current-controllable device is detected. The driving current is controlled according to the conduction current. The higher the conduction current the higher the driving current.

Abstract: A control circuit for a switching power converter is provided. The control circuit is installed between a secondary side and an output of the power converter and coupled to control a switching device. The control circuit includes a linear predict circuit, a reset circuit, a charge/discharge circuit, and a PWM circuit. The linear predict circuit is coupled to receive a linear predict signal from the secondary side for generating a charging signal. The reset circuit is couple to receive a resetting signal for generating a discharging signal. The charge/discharge circuit is coupled to receive the charging signal and the discharging signal for generating a ramp signal. The PWM circuit is coupled to receive the linear predict signal for enabling a switching signal and receive the ramp signal for resetting the switching signal.

Abstract: A timing circuit of a controller generates a clock signal having a switching period for use by a pulse width modulation (PWM) circuit to control a switch of a power supply. The switching period of the clock signal is based on a charging time plus a discharging time of a capacitor included in the timing circuit. A first current source charges the capacitor while the timing circuit is in a normal charging mode. A second current source charges the capacitor while the timing circuit is in an alternative charging mode that is when the on time of the switch exceeds a threshold time. The current provided by the second current source is less than the current provided by the first current source such that the switching period of the clock signal is increased in response to the timing circuit entering the alternative charging mode.

Abstract: An example power supply regulator includes an energy transfer element, a switch, and a controller. The controller 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: In one embodiment, a power supply controller is configured to adjust a peak value of a primary current through a power switch responsively to a difference between a demagnetization time and a discharge time of the parasitic leakage inductance of a transformer.

Abstract: A control circuit of a power converter according to the present invention comprises an output circuit, at least one input circuit and an input-voltage detection circuit. The output circuit generates a switching signal for regulating an output of the power converter in response to at least one feedback signal. The switching signal is coupled to switch a transformer of the power converter. The input circuit samples at least one input signal for generating the feedback signal. The input signal is correlated to the output of the power converter. The input-voltage detection circuit generates an input-voltage signal in response to the level of the an input voltage of the power converter. The input circuit will not sample the input signal when the input-voltage signal is lower than a threshold. The control circuit can eliminate the need of the input capacitor for improving the reliability of the power converter.

Abstract: A switching power supply apparatus includes a PFC converter, a DC-DC converter, and primary-side and secondary-side digital control circuits that control the PFC converter and the DC-DC converter. On the basis of a voltage detected by an output voltage detection circuit, the primary-side digital control circuit transmits data about the on-time of a switching element of the DC-DC converter to the primary-side digital control circuit. On the basis of this data, the primary-side digital control circuit controls the on-time of the switching element.

Abstract: A power converter is disclosed. An example power converter includes an energy transfer element coupled between a power converter input and a power converter output. A power switch is coupled to the energy transfer element and the power converter input. A feedback sampling circuit is coupled to receive a feedback signal representative of the power converter output to generate feedback signal samples during switching cycles. A switch conduction scheduling circuit is coupled to determine enabling and disabling of the power switch in future switching cycles in response to the feedback signal samples from a present switching cycle and one or more past switching cycles. A switch conduction control circuit is coupled to enable or disable conduction of the power switch during a switching cycle to control an amount of energy transferred from the power converter input to the power converter output.

Abstract: A switching mode power supply, having: an input port; an output port; an energy storage component and a pair of power switches coupled between input port and the output port; an error amplifier configured to generate an amplified error signal based on the feedback signal and the reference signal; an error comparator configured to generate a frequency control signal based on the amplified error signal and the first sawtooth signal; a peak current generator configured to generate a peak current signal based on the frequency control signal; a peak current comparator configured to generate a current limit signal based on the peak current signal and the current sense signal; and a logic circuit configured to generate a switching signal to control the power switches based on the frequency control signal and the current limit signal.

Abstract: A method, in a power supply controller, of responding to an increase in current through a terminal of the power supply controller, is disclosed. The method includes regulating the terminal to a first voltage level and sensing a magnitude of a first current through the terminal while the controller is regulating the terminal to the first voltage level. The method also includes providing an initial response by the power supply controller in response to the magnitude of the first current exceeding a first threshold current level and then regulating the terminal to a second voltage level after the magnitude of the first current exceeds the first threshold current level. The magnitude of a second current through the terminal is sensed while the controller is regulating the terminal to the second voltage level and the controller determines a final response based on the magnitude of the second current.

Abstract: A resonance-type power supply is provided in which no short circuit occurs and driving is performed with a constant switching period by performing switching control using a change of magnetic flux of a magnetic component as a trigger. When the change of magnetic flux of the transformer is detected, the first switching control signal is caused to transition to the Hi level. The detection voltage signal is A/D-converted, a first on-time is determined from the level thereof, and a second on-time is calculated by subtracting the first on-time from the constant switching period. When the first switching control signal is caused to transition to the Low level based on the first on-time, the change of magnetic flux of the transformer is detected, and the second switching control signal is caused to transition to the Hi level and is caused to transition to the Low level after the second on-time has elapsed.

Abstract: The present technology are directed to switching mode power supplies with primary side control. In one embodiment, the switching mode power supply provides an equivalent current signal which represents a load current. The equivalent current signal is then used to control a switching circuit in the switching mode power supply.

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.