Abstract: A power converter in one aspect limits the magnetic flux in a transformer. A control circuit included in the power converter includes a pulse width modulator, logic circuits and saturation prevention circuits. The saturation prevention circuits assert a first signal when a first integral value of the input voltage reaches a first threshold value and assert a second signal after a delay time that begins when a difference between the first integral value and a second integral value of a reset voltage of the transformer falls to a second threshold value. The logic circuits turn off the switch when the first signal is asserted, and allow the switch to turn on and off in accordance with the pulse width modulator when the second signal is asserted.

Abstract: A single-cycle charge regulator (SCCR) may be used in operating a power converter at a constant frequency without requiring compensation. The SCCR may include a first control loop to generate an error value based on the output voltage of the power converter and a reference voltage, and to generate a first control value based on the error value to control steady-state behavior of the output of the power converter. A second control loop may generate a second control value based on the error value, to regulate response of the power converter to a transient deviation on the output voltage.

Abstract: A transformer-based power conversion system includes a primary coil is provided in a current path that includes a single energy switch. An oscillator is coupled to a control input of the energy switch. The design conserves switch-based losses as compared to prior designs because a single switch is provided in a current path occupied by the primary coil. The design also provides improved conversion efficiency because parasitic capacitances associated with the energy switch cooperate with charge transfers generated by the oscillator.

Abstract: A pulse width modulator (PWM) includes a driver and a two-way integrator. The driver is coupled to output a first and a subsequent period of a PWM signal. Both the first and the subsequent periods include the PWM signal changing between first and second states. The two-way integrator is coupled to integrate an input current and coupled to generate a duty ratio signal in response to integrating the input current. The driver determines a duty factor of both the first and the subsequent periods by setting the PWM signal to the second state in response to the duty ratio signal. The two-way integrator includes a capacitor that integrates the input current during the first period by charging the capacitor and integrates the input current during the subsequent period by discharging the capacitor.

Abstract: A controller for use in a power supply regulator is disclosed. One controller includes a feedback circuit coupled to generate a feedback current signal that corresponds to a peak switching current in response to a sense signal from a power supply regulator output. A comparator is coupled to compare the feedback current signal with a reference voltage. A modulation circuit is coupled to the feedback circuit to generate a pulse width modulated switching signal with fixed switching frequency in response to the feedback current signal and the reference voltage. A multi-cycle modulator circuit is coupled to the output of the comparator. The multi-cycle modulator circuit is coupled to enable or disable a switch signal from the controller to be coupled to a switch of the power supply regulator. A group of two or more consecutive switching cycles is separated from a next group having two or more switching cycles by a time of no switching.

Abstract: A controller is adapted for controlling a switch of a resonant direct current/direct current converter, and includes: a pulse width modulation controlling unit for detecting an output voltage of the resonant direct current/direct current converter, and for generating a pulse width modulation signal according to the output voltage detected thereby; a fixed frequency signal generating unit for generating a fixed frequency signal; and a logic synthesizing unit for synthesizing the pulse width modulation signal and the fixed frequency signal so as to generate a driving signal that is adapted to drive the switch of the resonant direct current/direct current converter.

Abstract: A control circuit selectively energizes a load, such as an elevator or escalator brake (28). The circuit includes a transformer (12) with a primary-winding connected to a series with a semiconductor switch (40) that is driven by a pulse width modulation (PWM) controller. Power to the PWM controller is supplied through safety relay contacts (52A, 52B). When the load is to be energized, the safety relay contacts are closed and the PWM controller drives the semiconductor switch to supply energy through the transformer to the secondary circuit. A command signal to secondary circuitry (64) causes power in the secondary to be applied to the load (12). If the safety relay contacts open, the PWM controller turns off and power is no longer delivered to the secondary circuit and the load.

Abstract: A control device for controlling a switch unit of a resonant direct current/direct current converter includes a frequency modulation controller and a pulse selector. The frequency modulation controller is adapted to be coupled electrically to the converter for receiving a correcting threshold value and output information of the converter, and for generating a synchronization signal according to the correcting threshold value and the output information received thereby. The pulse selector is adapted to be coupled electrically to the converter and the frequency modulation controller for receiving the correcting threshold value, the output information and the synchronization signal, and for generating a driving signal according to the correcting threshold value, the output information and the synchronization signal received thereby. The driving signal is adapted to drive the switch unit and has a working period.

Abstract: A power supply for a computer includes a transformer, a rectifier, a pulse width modulation (PWM) controller, a relay, a power switch, and a battery. The PWM controller includes a voltage terminal and a pulse terminal. The relay includes a switch and an inductance coil. An alternating current (AC) power supply is connected to a primary inductance coil of the transformer via the rectifier. A secondary inductance coil of the transformer provides a standby voltage. A positive voltage terminal of the rectifier is connected to the pulse terminal of the PWM controller via the primary inductance coil of the transformer. The switch is connected between the positive voltage terminal of the rectifier and the voltage terminal of the PWM controller. The inductance coil and the power switch are connected in series between the battery and ground. The power switch is controlled by powering on or off the computer.

Abstract: An electronic ballast including a rectifying circuit to provide a signal representative of the current signal associated with a buck inductor, a monitoring circuit to provide a monitoring circuit signal when the signal representative of the buck inductor is within a specified range, and a comparing circuit coupled to the rectifying circuit and the monitoring circuit and operable to alter the output of the power converter circuit driving the lamps in response to comparisons between the signals from the rectifying circuit and the monitoring circuit to control power conditions in the ballasts.

Abstract: A controller for use in a power supply regulator is disclosed. One controller includes a feedback circuit coupled to generate an equivalent switching frequency signal in response to a sense signal from a power supply regulator output. A comparator is coupled to compare the equivalent switching frequency signal with a reference signal. A period modulation circuit is coupled to the feedback circuit to generate a period modulation switching signal in response to the equivalent switching frequency signal. A multi-cycle modulator circuit is coupled to the output of the comparator. The multi-cycle modulator circuit is coupled to enable or disable a switch signal from the controller, which is to be coupled to a switch of the power supply regulator. A group of two or more consecutive switching cycles is separated from a next group having two or more switching cycles by a time of no switching.

Abstract: A switching mode power supply includes a transformer which includes a primary winding and two secondary windings. One secondary winding and the primary winding constitute a forward circuit. The other secondary winding and the primary winding constitute a flyback circuit. The switching mode power supply also includes a power storing circuit and an output terminal. The power storing circuit is interposed between the forward circuit, the flyback circuit, and the output terminal.

Abstract: A frequency jittering circuit modulates a hysteretic band of an oscillator such that the clock generated by the oscillator has a jitter frequency, and thus a switching mode power supply operative on the clock will have a jittering switching frequency.

Abstract: A power converter for compensating a maximum output power includes a power switch, a control circuit, an oscillator and a frequency modulator. The control circuit generates a PWM signal in response to the pulse signal generated by the oscillator. The frequency modulator generates a second discharge signal to the oscillator for controlling the maximum output power of the power converter. The second discharge signal is decreased for prolonging a switching period of the PWM signal under a high-line voltage of the power converter.

Abstract: The switched mode power supply contains a transformer, which has a primary winding and at least one secondary winding, a switching transistor in series with the primary winding and a control circuit for controlling an output voltage of the switched mode power supply. The control circuit contains an oscillator, whose oscillation frequency can be set via a terminal, and which is coupled to a secondary winding of the transformer. The wiring for the terminal is connected such that the switched mode power supply starts up at a relatively low oscillation frequency once it has been connected, and, during operation when an additional voltage is supplied to the input via the secondary winding, the oscillation frequency of the switched mode power supply is increased. The terminal is connected in particular via a bandpass filter to a voltage generated by the secondary winding.

Abstract: A power equalization circuit in a transformer-based device having a plurality of isolated voltage outputs is provided. The circuit comprises: a threshold detection circuit configured to receive an error signal derived from a selected voltage at one of the isolated voltage outputs, and to determine whether the selected voltage is above a voltage threshold based on the error signal; a timer circuit configured to activate a wait signal after a maximum voltage drift time has expired since the selected voltage rose above the voltage threshold, and to activate a wink signal coincident with the wait signal; an overdrive current source configured to drive an error current to an overdriven value in response to the wait signal; and a commutator circuit connected to a transistor winding associated with the selected isolated voltage output, the commutator being configured to connect a transformer secondary winding to ground in response to the wink signal.

Abstract: A digital timing read back and an adaptive feedforward compensation algorithm to reduce harmonic distortion is disclosed. More specifically, the approach generates harmonic components digitally with the same magnitude but at an opposite phase to the output harmonic distortion. An anti-distortion signal is generated and added to the input signal. The magnitude and phase of the harmonic distortion change with the modulation level or index and the frequency of the input signal. In addition, the harmonic distortion level varies significantly with different timing error statistics in different power devices. The inventive method takes the modulation level or index, the frequency of the input signal and the timing error statistics acquired through a digital read back circuit as input variables to determine the magnitude and phase of the anti-distortion signal.

Abstract: A telephone terminal includes: a main unit; an optional unit that performs an arbitrary additional communication function and detachably attached to the main unit; a distribution unit that distributes a drive power supplied through a communication network into a first channel and a second channel when a power of the telephone terminal is turned on; a first power supplying unit that supplies the first channel of the drive power to the main unit at a first timing; and a second power supplying unit that supplies the second channel of the drive power to the optional unit at a second timing shifted from the first timing.

Abstract: A DC voltage converter used for producing a driving voltage to drive a load comprising a step-up circuit and a modulation circuit is provided. The step-up circuit is used for receiving an input voltage and boosting the input voltage to produce an output voltage. The output voltage is controlled according to a feedback voltage indicative of state of the load. The modulation circuit is electrically connected to the step-up circuit and transforms the output voltage into the driving voltage with a higher voltage level so as to further increase the voltage level of the already boosted output voltage.

Abstract: A voltage controller (150), the controller comprising: a voltage comparator (700) operative to provide a digital error signal (152); a compensator (300) operative to determine a digital control signal (154) based on said provided error signal; and a modulator (400) operative to provide a power control signal (156) based on said determined digital control signal, wherein said comparator, said compensator, and said modulator are implemented entirely with digital logic gates.

Abstract: This invention relates to methods and apparatus for sensing the output current in a switch mode power supply (SMPS) using primary side sensing. We describe a module which senses a current in a primary winding of a transformer and a voltage on a primary or auxiliary winding of the transformer, and which includes a multiplier coupled to an output of a signal averager averaging a primary winding current and to an output of a timing signal generator using the sensed voltage to signal when a secondary winding is powering an output of the SMPS, to multiply an averaged current sense signal by a fraction of a total cycle period of said SMPS during which the secondary winding is providing power to provide a signal estimating an output current of the SMPS.

Abstract: A power converter includes: a transformer controlled by a main switch to receive an input power according to a driving signal; a switching circuit outputting a sync signal; and a driving circuit including a dead time controller that includes first and second switches operating according to the sync signal, and an inverse phase generator that includes third and fourth switches and that generates a switching signal. A circuit switch of the switching circuit operates according to the switching signal. Transition of the driving signal from high to low causes the switching signal to transition from low to high with a dead time between a falling edge of the sync signal and a rising edge of the switching signal. Transition of the driving signal from low to high causes the switching signal to transition from high to low with a dead time between a falling edge of the switching signal and a rising edge of the sync signal.

Abstract: Methods and apparatus for sensing the output current in a switch mode power supply (SMPS) using primary side sensing are described. A system includes a primary current sense input, a charge input to sense a charging time of an SMPS transformer; a discharge input to sense a discharging time of the transformer; at least one averager; and a calculator. The primary current is averaged by the averager over at least a switching cycle of the SMPS and the calculator estimates the output current of the SMPS using the averaged primary current, the charge signal and the discharge signal.

Abstract: According to one embodiment, a voltage regulator includes a switch configured to selectively conduct electrical energy according to a signal, and circuitry configured to provide the signal to implement a soft start procedure comprising varying frequency and duty cycle of the signal.

Abstract: The adaptive synchronous rectification control circuit and its controlling method for a power converter are provided. The proposed control circuit having a transformer with a primary and a secondary sides, a switch coupled to the primary side and a synchronous rectification transistor (SRT) coupled to the secondary side and having a parasitic diode includes a preprocessor receiving a source-drain voltage of the SRT and outputting a first signal, and a control set receiving the first signal, a pre-determined voltage and a pulse signal synchronized to the switch and generating a second signal synchronized to the switch for controlling the SRT, in which a selection of the pre-determined voltage makes the source-drain voltage of the SRT ranged from 0 to a conducting voltage of the parasitic diode of the SRT.

Abstract: A DC-to-DC converter comprises a converter section and a controller section. The converter section comprises a primary section and a secondary section. The primary and secondary section includes MOSFET switches. The controller section is coupled to the converter section and comprises a pulse width modulation (PWM) section and a delay section. The PWM section comprises an error amplifier configured to generate an error signal representative of a variance between an output voltage of the converter section and a reference voltage and a PWM configured to produce a PWM signal based on the error signal. The delay section comprises of delay circuits configured to generate delayed output signals from the PWM signal and power switching device drivers coupled to the delay circuits and configured to receive the delay output signals and generate a controlled signals to control the on/off state of the MOSFET switches.

Abstract: The provided switching power supply includes an auxiliary circuit having an auxiliary switch and a auxiliary capacitor, a transformer having a primary side coupled to the auxiliary circuit in parallel and a secondary side, an auxiliary switch control circuit coupled to the auxiliary switch and the primary side and fixing a turn-on time of the auxiliary switch, a main switch coupled to the primary side, a ZVS detector coupled to the main switch, a first and a second rectifying switches coupled to the secondary side and a filter circuit coupled to the second rectifying switch in parallel. The provided method includes the steps of: (a) fixing the turn-on time of the auxiliary switch; and (b) generating a fixed turn-off time of the main switch accordingly so as to accomplish ZVS of the main switch.

Abstract: A method is disclosed for generating pulse width modulated pulse control signals for controlling switches in a switching power supply. First, a count value is determined of a master clock within a switching cycle of the power supply from beginning to end thereof. A separate state machine providing for each edge in each of pulse control signals and each is operated to generate the associated edge as a function of the sum of a fixed reference count value from the beginning of the switching cycle and a determined count value when the sum is determined to equal the actual count value.

Abstract: A new pulse width modulation return scheme in which the source of PWM FET is directly connected to the 48 Volt return and therefore Ids of PWM FET does not pass through the hot-swap FET which therefore significantly reduce the power dissipation on the die of PD chip.

Abstract: A switching regulation system and control scheme efficiently enables driving multiple loads from a common energy storage element, such as an inductor. The control scheme operates to store energy in the energy storage element over a first portion of a cycle, such as by ramping up current through an inductor, according to energy requirements of the multiple loads. After storing the energy in the storage element during the first portion of the cycle, the stored energy is delivered consecutively to each of the multiple loads over a subsequent portion of the cycle.

Abstract: An inventive inverter has a semiconductor switch circuit connected to the primary winding of a transformer. The semiconductor switch circuit is respectively controlled by PWM to supply a constant current to the load connected to a secondary winding of the transformer. The inverter is capable of deliberately regulating its ac power output to the load and lowering the lower limit of the output power through control of the intermittent operation, in which an error signal for carrying out the PWM control is reduced to zero during each off-duty period. In addition, the error signal for the PWM control is slowly decreased or increased in each shift from an off-duty period to on-duty period, and vise versa, by charging or discharging the capacitor in a feedback circuit, thereby allowing slow start or slow end of the respective on-off operations for the constant current control through the PWM.

Abstract: A synchronous DC-to-DC converter includes an inductor coupled to receive an input voltage, a first transistor having a source coupled to a first reference voltage and a drain coupled to the inductor, and a second transistor having a source coupled to an output conductor to produce an output voltage and a drain coupled to the inductor. A feedback signal representative of a value of the output voltage is generated, and a switch control signal is produced in response to the input voltage and a second reference voltage. The second transistor is turned off in response to the switch control signal each time the inductor current has decayed to zero to prevent reverse current flow through the inductor. A regulating signal indicates whether or not the feedback voltage exceeds the second reference voltage, to regulate the output voltage in a pulse-frequency modulation mode.

Abstract: A switching regulator has an input voltage detection circuit which inputs a voltage applied to a rectifier diode 7 connected in series with the secondary side of a transformer and generates a voltage signal Vvp corresponding to the voltage, and a calculation unit which calculates a voltage value Vin inputted to the primary side of the transformer based on a voltage value of the voltage signal generated by the input voltage detection circuit.

Abstract: A switching power supply is disclosed for improving the no-load power drain of low-power mains operated supplies. The power converter utilizes a cascoded switch arrangement with a conventional high voltage power MOSFET and a low voltage, low gate charge MOSFET. Driving only the small low voltage device reduces the power required for gate drive. The disclosed configuration is also capable of generating a non-isolated auxiliary rail for powering its control circuitry utilizing the parasitic capacitance of the high voltage power devices as an element in a charge pump. The resulting power supply requires significantly fewer components.

Abstract: Methods and apparatus for sensing the output current in a switch mode power supply (SMPS) using primary side sensing are described. A module senses a current in a primary winding of a transformer and a voltage on a primary or auxiliary winding of the transformer, and which includes a multiplier coupled to an output of a signal averager averaging a primary winding current and to an output of a timing signal generator using the sensed voltage to signal when a secondary winding is powering an output of the SMPS, to multiply an averaged current sense signal by a fraction of a total cycle period of said SMPS during which the secondary winding is providing power to provide a signal estimating an output current of the SMPS.

Abstract: An inventive inverter has a semiconductor switch circuit connected to the primary winding of a transformer. The semiconductor switch circuit is respectively controlled by PWM to supply a constant current to the load connected to a secondary winding of the transformer. The inverter is capable of deliberately regulating its ac power output to the load and lowering the lower limit of the output power through control of the intermittent operation, in which an error signal for carrying out the PWM control is reduced to zero during each off-duty period. In addition, the error signal for the PWM control is slowly decreased or increased in each shift from an off-duty period to on-duty period, and vise versa, by charging or discharging the capacitor in a feedback circuit, thereby allowing slow start or slow end of the respective on-off operations for the constant current control through the PWM.

Abstract: In accordance with the switching operation of a switching section, current is made to flow from a battery to an inductor repeatedly. A voltage generated at the inductor is smoothed by a condenser and then input to a regulator. A D/A converter within a CPU monitors the input to the regulator, and an output voltage of the regulator stabilizes a reference voltage of the D/A converter.

Abstract: A timing control circuit (70) generates staggered signals from a pulse width modulated signal (68) providing lossless switching in a DC to DC power converter (10). The DC to DC power converter (10) comprises two input MOSFET switches (22, 28) coupled to primary windings (34) of an isolation transformer (36) and two output MOSFET switches (38, 50) coupled to secondary windings (48) of the isolation transformer. The timing circuit (70) comprises an input terminal (90) for receiving a pulse width modulated signal (68) that switches low at time t1 and high at time t4. A first timing output signal circuit (92) is responsive to the pulse width modulated signal (68) and provides a first timing output signal (72) that switches low at time t1 and high at time t7 to control one of the input MOSFET switches (22).

Abstract: In the PWM circuit of the present invention, a PWM counter counts clock signals. A reference value setting register sets a comparative reference value for determining a duty ratio of a PWM signal. A comparator generates the PWM signals based on a comparative result of the comparative reference value and a count value of the PWM counter. A delay device delays the PWM signal. A switching device switchably outputs the output of the comparator and the output of the delay device in order of time sequence. Thereby, the pulse phase of the PWM signal can be adjusted.

Abstract: A light emitting element drive circuit and a display system able to simultaneously perform constant current control and PWM control and able to perform a stable adjustment of luminance over a wide dynamic range, including a constant voltage source having an output voltage adjustment unit able to be changed in output voltage according to a signal from the outside, a switch circuit connected to the cathode side of the LED and ON/OFF controlled in accordance with a PWM signal from the outside, a current detection unit for detecting the current flowing in the circuit, and a sample and hold circuit for maintaining the current input value from the current detection unit for a constant period, and the output voltage adjustment unit receives as input the output of the sample and hold circuit, that is, the current value when the switch circuit is ON, and adjusts the output of the constant voltage source so that this value becomes a previously determined set value, to thereby make the current flowing in the LED constan

Abstract: The present invention discloses a method for controlling transformer excitation cycles and a circuit for controlling the same, wherein the excitation cycle and the demagnetization cycle, which determine the rise and fall of the excitation current, are modified to prevent the coil from being saturated. In the present invention, a sense current is acquired from the excitation current of the transformer coil, and a demagnetization reference value is set. The sense current is used to determine whether the excitation current is lowered to the demagnetization reference value in the demagnetization cycle. A cycle modifying circuit is used to modify the duty cycle signal output by a pulse control unit until the excitation current is lowered to a preset level.

Abstract: A closed loop power converter circuit of a UPS or other power supply includes a pulse width modulator circuit in a forward path of the closed loop power circuit. A compensation circuit provides pulse width commands to the pulse width modulator at a first rate. A feedback circuit digitally filters samples of an output of the closed loop power converter at a second rate greater the first rate and that provides the filtered samples to the compensation circuit. In some embodiments, the compensation circuit may be operative to compensate for the phase lag associated with a low pass output filter.

Abstract: An inventive inverter has a semiconductor switch circuit connected to the primary winding of a transformer. The semiconductor switch circuit is respectively controlled by PWM to supply a constant current to the load. connected to a secondary winding of the transformer. The inverter is capable of deliberately regulating its ac power output to the load and lowering the lower limit of the output power through control of the intermittent operation, in which an error signal for carrying out the PWM control is reduced to zero during each off-duty period. In addition, the error signal for the PWM control is slowly decreased or increased in each shift from an off-duty period to on-duty period, and vise versa, by charging or discharging the capacitor in a feedback circuit, thereby allowing slow start or slow end of the respective on-off operations for the constant current control through the PWM.

Abstract: According to one embodiment, the switching power supply device comprises a DC-DC converter, an alternating current driver circuit, a smoothing capacitor and control circuitry. The control circuitry operates for adjusting a phase of an oscillation signal from the alternating current driver circuit to coincide start time points of current conducting periods between the output stage of the DC-DC converter and an input stage of the alternating current driver circuit.

Abstract: A switching power source device can enhance the power factor by increasing the conduction angle of an input current in a wide input voltage range, while obviating the increase of size and the increase of cost thereof, and lower the switching loss by removing higher harmonic waves from the input current. The device includes at least first, second, and third series circuits constituted of a rectifying circuit, at least first and second primary windings, a plurality of diodes, a smoothing capacitor, and first and second switching elements.

Abstract: Hot swappable pulse width modulation power supply circuits preferably realized in integrated circuit form. The hot swap circuits provide for de-bouncing, controlled charging of the input capacitor of the power supply circuit and soft-start of the pulse width modulator after charging the input capacitor. Other features include a low voltage lockout, and an output for coupling to a synchronous rectifier driver to synchronize synchronous rectifiers on the secondary side of a coupling transformer in isolated systems. The hot swap capability may be disabled through an enable pin, or not implemented by not connecting the integrated circuit in a manner to use the hot swap capability.

Abstract: An object of the present invention is to lower the voltage applied to the starting resistor of the starting circuit in a switching power supply circuit to reduce the power loss especially when the receiving voltage is high and thereby provide a small and inexpensive switching power supply circuit. According to the present invention, a switching power supply circuit comprises: a DC voltage section having two or more capacitors connected in series; and a PWM control circuit for receiving DC power supply from the DC voltage section and performing switching control on a primary side of a transformer in order for the switching power supply circuit to output a DC voltage of different voltage specifications; wherein the starting resistor for the PWM control circuit is connected to a connection point of the capacitors.

Abstract: The present invention relates to a control circuit for controlling the output power of a primary-controlled switched mode power supply unit, which comprises a primary switch and a transformer with an auxiliary winding. Within the auxiliary winding, voltage pulses are induced by primary-sided switching operations, which can be taken into account when controlling the output power. In order to provide an improved control and an enhanced flexibility with respect to the operational parameters, the sampling instance is determined based on the duration of the voltage pulse at the auxiliary winding during a previous switching cycle. In order to detect a defective contact between the auxiliary winding and the control circuit in a particularly simple and secure manner, the negative voltage pulse at the auxiliary winding occurring when the switch is closed may be used for confirming a proper connection.

Abstract: A PWM signal to DC voltage converting unit includes at least a switch section adapted to provide an on/off function; a driving section electrically connected to the switch section for driving the switch section to provide the on/off function; a first voltage stabilizing section electrically connected to the switch section for generating a voltage; a bridging section electrically connected to the first voltage stabilizing section for keeping the first voltage stabilizing section in one-direction transmission; a second voltage stabilizing section electrically connected to the bridging section for generating a voltage; and an electricity-storing section electrically connected to the second voltage stabilizing section, such that power transmitted by the first and the second voltage stabilizing section may be charged to or discharged from the electricity-storing element. By controlling a duty cycle of an input PWM signal, the output voltage can be adjusted.

Abstract: A PWM controller has a line voltage input that allows using a start-up resistor for both start-up and power-limit compensations so that it can save the power consumption, ease the PCB layout, and shrink the power supply size. In the integrated circuit, a current switch used for both start-up and line voltage sensing is composed of a diode and a switch transistor. A current multiplier is used to improve the precise by canceling the impact of the integrated resistor's absolute value, which is composed of a transistor loop, a constant current and a reference current. Thus, by properly selecting the value of the start-up resistor, an identical output power limit for low line and high line voltage input can be achieved.