Abstract: An ultra high voltage regulator for converting includes a rectifying circuit, a first transistor, a second transistor, an output capacitor, a first resistor, a second resistor, and a third resistor. The ultra high voltage regulator converts a received alternative current into a direct voltage to an electrical component. The ultra high voltage regulator capable of providing a larger current becomes more compact and thinner in size without cooperating with a mass transformer/high voltage capacitor, which satisfies the request for miniaturization of the electrical components.

Abstract: An AC-DC power converter includes a rectifying unit, an output stage, a controller and a soft-start circuit. The rectifying unit is configured to rectify an AC voltage to a rectified voltage. The output stage is coupled to the rectifying unit and configured to convert the rectified voltage into a DC voltage for a load. The controller is coupled to the output stage and configured to control the output stage. The soft-start circuit is coupled to the rectifying unit to receive the rectified voltage. The soft-start circuit is configured to detect whether the rectified voltage is at or below a predetermined level, and to enable the controller if the rectified voltage is detected to be at or below the predetermined level.

Abstract: A power converter startup circuit establishes an operating voltage for control circuitry during startup and is then disabled to reduce no-load power dissipation. The startup circuit has a normally on characteristic to automatically provide startup charging current for a startup capacitor. The control circuitry begins operating as the startup capacitor voltage reaches an operating value, and it generates an inhibitory signal that disables the startup circuit to stop the startup charging current and reduce power dissipation. The normally on characteristic is achieved by an emitter switched current source employing a normally on device such as a depletion-mode J-FET. A resistor divider network provides both biasing for the startup current source and a point of monitoring the power supply input voltage during steady state operation.

Abstract: A bootstrap assist circuit and a startup circuit comprising a voltage controlled switch and a startup ramp voltage generator connected to the voltage controlled switch that will control a high side switch, a dimming interface or an enable/disable input function. Said system is used to provide a bootstrap technique to continuously switch a floating high side switch (MOSFET) by continuously charging a capacitor and then “level shifting” said capacitor voltage across the gate and source of the said high side switch to turn the switch on.

Abstract: A bandgap voltage reference and voltage regulator system includes a bandgap voltage reference circuit and a voltage regulator circuit that share a single, common amplifier. The amplifier acts as a gain stage for the reference circuit and as an error amplifier for a driver stage of the regulator circuit. The regulator circuit has an input reference generated by the reference circuit, and the reference circuit acts as a load to the driver stage, obviating the need for a bias resistance network. By sharing the amplifier and obviating the need for a resistance network, the area and overall quiescent current of the system are reduced. The system can be implemented in CMOS/BiCMOS technology and is suited for low power applications.

Abstract: A semiconductor device, a start-up circuit, and an operating method for the same are provided. The start-up circuit comprises a semiconductor unit, a first circuit, a second circuit, a voltage input terminal and a voltage output terminal. The first circuit is constituted by one diode or a plurality of diodes electrically connected to each other in series. The second circuit is constituted by one diode or a plurality of diodes electrically connected to each other in series. The semiconductor unit is coupled to a first node between the first circuit and the second circuit. The voltage input terminal is coupled to the semiconductor unit. The voltage output terminal is coupled to a second node between the semiconductor unit and the first circuit.

Abstract: In a power supply device, the controller outputs a control signal specifying a voltage value. The voltage conversion unit converts a first voltage to a second voltage in response to a control signal specifying a voltage value output from the controller. The voltage conversion unit converts the first voltage to a start voltage, as the second voltage, in response to a first control signal specifying a start voltage value output from the controller and further converts the first voltage to a target voltage, as the second voltage, in response to a second control signal specifying a target voltage value output from the controller. A transition period of time is intervened between generation of the start voltage and generation of the target voltage during which the controller outputs a third control signal specifying the intermediate voltage value between the start voltage value and the target voltage value.

Abstract: Apparatus and methods operate to disable a dynamically biased apparatus and a dynamic bias current source providing dynamic bias current to the apparatus at the beginning of a static bias startup period shortly after power-on. The dynamically biased apparatus is then gradually enabled in a static bias mode of operation during the static bias startup period. Following the end of the static bias startup period, operation of the dynamically biased apparatus in a dynamic transconductance mode is gradually enabled during a dynamic bias startup period. Such startup sequence operates to prevent damaging in-rush currents in a system employing the dynamically biased apparatus in a feedback control loop.

Abstract: A control circuit for controlling a soft-start time of a DC power supply includes a digital potentiometer, a first drive circuit, and a controller. The digital potentiometer includes a first potentiometer. The first drive circuit includes a first driver, a first MOSFET, and a first charge capacitor. The first driver charges the first charge capacitor via the first potentiometer when the DC power supply is first switched on, and the first MOSFET is switched on to connect the DC power supply to the load when the first charge capacitor is fully charged. The controller regulates resistance of the first potentiometer to regulate a charge time constant of the first charge capacitor, enabling a gradual rise in voltage supplied, from approximately zero to full power, within a desired period of time.

Abstract: A signal generating circuit includes: a first signal amplifying circuit arranged to generate a first amplified signal according to a first supply current, a reference signal, and an output signal of the signal generating circuit; a soft-start circuit arranged to generate a control signal according to a soft-start signal; a current controlled circuit arranged to generate the first supply current according to the soft-start signal; and a pass transistor arranged to generate an output signal according to an error amplified signal and the control signal. The error amplified signal is derived from the first amplified signal.

Abstract: A soft start circuit includes an error amplifier for generating a control signal according to an input voltage, a feedback voltage and a reference voltage, a feedback circuit for generating the feedback voltage according to an output voltage, an internal voltage source for generating a soft start voltage, and a sink circuit including a first transformation module for generating a first transformation current according to the soft start voltage, a second transformation module for generating a second transformation current according to the feedback voltage, a comparison module coupled to the first transformation module and the second transformation module for generating a comparison result according to the first transformation current and the second transformation current, and an output module coupled to the comparison module for generating a sink current according to the comparison result, so as to control the control signal.

Abstract: The present relates to a start-up circuit, which is used for starting up a variable power supply circuit, which comprises a detection circuit and a transition circuit. The detection circuit is used for detecting an output voltage of the variable power supply and producing a detection signal. The transition circuit is coupled to the detection circuit. It transits the level of the detection signal and produces a control signal for starting up or cutting off the variable power supply. Thereby, the problem of incapability in transition can be avoided as well as achieving the purpose of low power consumption.

Abstract: At least one embodiment is directed to a semiconductor voltage controller comprising: a start-mode circuit associated with a start-mode; and an off-mode circuit associated with an off-mode, where the voltage controller can be configured to receive a feedback signal and an off-mode signal from a single input and provide an output voltage, where the voltage controller can be configured to be in the off-mode when the feedback signal is less than a skip level and the feedback signal is less than a HV control level, and where the voltage controller can be configured to be in start mode when the feedback signal is greater than HV control level and Vcc is below a Vcc-start.

Abstract: A novel integrated switched mode power supply circuit that provides supply voltages to an integrated circuit may be of minimal complexity and have the capacity for a wide range of input supply voltages. The novel power supply may include cascaded, unregulated step-down charge pumps (e.g. unregulated voltage splitters), one or more linear regulators coupled to the output of the cascaded voltage splitters, and a start-up current source to provide the IC supply current until the input supply voltage is sufficiently high for the voltage splitter(s) to be functional to provide the IC supply current. Furthermore, each voltage splitter may be activated or disabled depending on the value of the input supply voltage, and the input of a disabled voltage splitter may be shorted to its output via an integrated power switch. Using (cascaded) voltage splitters to provide the IC supply current reduces overall power dissipation in the IC.

Abstract: A startup circuit includes a MOSFET that is connected between a startup power source and an auxiliary power source made of a smoothing capacitor and passes a startup current from the startup power source to the smoothing capacitor, a JFET that has a drain terminal connected to a drain terminal of the MOSFET and a source terminal connected through a resistor to a gate terminal of the MOSFET, and a pinch-off voltage controller that controls a pinch-off voltage of the JFET to a first reference voltage at startup and to a second reference voltage, which is lower than the first reference voltage, after startup.

Abstract: A peak current controlled switching voltage regulator system and method for providing a self-power down mode. An on-chip voltage regulator integrated into an on-chip digital logic circuit provides a core supply voltage to the on-chip digital logic circuit along with an off-chip inductor. An off-chip regulator connected to the on-chip digital logic circuit provides an external core supply voltage with respect to the on-chip digital logic circuit. A start-up circuit operates the on-chip voltage regulator in a self-power down mode for a pre-determined time period when the on-chip regulator is not connected to the off-chip inductor in order to maintain an equilibrium voltage supply with respect to the on-chip digital logic circuit.

Abstract: A power control circuit includes a control circuit configured to perform a soft start operation before a power supply device performs a normal operation. The power control circuit also includes a counter circuit configured to divide a switching frequency of the power supply device in the normal operation, wherein the counter circuit measures a period of the soft start operation and when the period lasts for a set length, starts to divide the switching frequency, and wherein the power control circuit causes a comparator comprising the counter circuit to compare the frequency obtained by dividing the switching frequency with a reference frequency and corrects the switching frequency.

Abstract: A power conversion circuit of two feedback loops is disclosed that includes a feedback control circuit for ramping up or down a commanded voltage to a load (e.g., LEDs). The second feedback loop feeds into the first feedback loop, and the second feedback loop operates at a slower bandwidth than the first feedback loop. When ramping up or down the commanded voltage, a voltage overshoot results because of delay in the system. The overshoot can be compensated for by a final adjustment to the commanded voltage.

Abstract: Provided is a voltage regulator which includes an inrush current prevention circuit so that no current is consumed after the start-up of the voltage regulator. A start-up circuit of the voltage regulator includes: a constant current circuit; a first transistor connected between the constant current circuit and a constant voltage generation circuit; a second transistor including a drain connected to a gate of the first transistor, and a gate to which a voltage based on an output voltage is input; a first depletion transistor including a gate connected to the drain of the second transistor, and a source connected to a source of the second transistor; and a third transistor including a gate connected to the gate of the second transistor, and a drain connected to the drain of the second transistor.

Abstract: An integrated start-up circuit for a power supply includes a converter, which in one implementation can be a buck converter. The buck converter includes a gate driver configured to drive a power switch, where the power switch is coupled across a DC bus node and a switching node of the buck converter. The power switch is configured to provide a start-up voltage to the buck converter from the DC bus node during start-up of the buck converter. The buck converter includes a bootstrap switch coupled across the gate driver and a Vcc node and a Schottky diode coupled across the bootstrap switch and the switching node, where the start-up voltage is provided at the Vcc node through the bootstrap switch.

Abstract: In one embodiment, a method of forming a power supply controller may include configuring the power supply controller to control a pass transistor to form an output current responsively to a control signal and independently of the value of the output voltage until the control signal is less than a deviation from a desired value of the output voltage.

Abstract: A low dropout voltage regulator is provided. The low dropout voltage regulator includes a comparison unit, a buck unit, a feedback unit and a current-drawing unit. The comparison unit is used for receiving a reference voltage and a feedback voltage, and comparing the reference voltage and the feedback voltage to output a first voltage. The buck unit is used for receiving an input voltage and the first voltage and transferring the input voltage to a output voltage. The feedback unit is used for receiving the output voltage, and converting the output voltage to a feedback voltage, and then transmitting the feedback voltage to the comparison unit. The current-drawing unit determines whether to draw a portion of a first current generated by the buck unit, so as to stabilize the output voltage.

Abstract: Provided is a soft-start circuit which is capable of reducing the current consumption after the output of a switching power supply apparatus having been raised. It comprises a soft-start generation unit 30 for generating a soft-start voltage Vss gradually raised from 0V by charging an external capacitor Css connected thereto; a power supply unit 20 for detecting the termination of a soft-start for supplying power to the soft-start generation unit 30; and a power supply judgment unit 40 for causing the supply of power from the power supply unit 20 to the soft-start generation unit 30 to be shut down. The power supply judgment unit 40 causes the supply of power from the power supply unit 20 to the soft-start generation unit 30 to be shut down after the soft-start voltage Vss having reached the reference voltage Vref.

Abstract: A voltage regulator apparatus includes a first power transistor and a second power transistor connected in parallel to each other between a first power source and a second power source, and a control unit for turning on the first power transistor and the second power transistor. An aspect ratio of the first power transistor is smaller than an aspect ratio of the second power transistor. The control unit turns on the second power transistor in a predetermined period of time after the first power transistor is turned on.

Abstract: Methods of a switching mode DC/DC converter are provided in the present invention. The proposed method includes a step of causing a switching frequency of the converter to be operated at a rated value multiplied by a second predetermined value when an output voltage of the converter is not larger than a first predetermined value.

Abstract: A starter of the grid-connected inverter and a control method thereof are disclosed. The starter comprises a controller, and a first switch and a first resistor connected in parallel. The controller includes an input end, and first and second output ends. The input end inspects the DC voltage signal from the inverter. When the DC voltage exceeds a predetermined voltage threshold, the first output end sends a first control signal to turn on the first switch, and the second output end sends a second control signal to make the grid-connected inverter enter into a chopping mode. There is a delay period between the send time of the first control signal and that of the second control signal.

Abstract: According to one embodiment of the invention, there is provided a switching power supply device including a rectifying circuit and a switching operation conversion circuit. The rectifying circuit receives a phase-controlled alternating voltage to rectify to a direct voltage. The switching operation conversion circuit starts up by being applied with the direct voltage, and includes a normally on type switching element and an off driving circuit. The normally on type switching element passes an input current, and the off driving circuit turns off the switching element when the input current reaches a prescribed value. The switching operation conversion circuit converts the direct voltage to an output voltage different from the direct voltage by repeating a switching operation of turning on and off the switching element.

Abstract: A design and method for controlling the initial inductor current in a DC/DC switching regulator. The Ton or Toff time, depending upon implementation, is gradually increased such that power applied to a load is initially constrained until the system reaches a stable state, at which time normal power is connected to the load. In an embodiment, the on or off time is limited by a circuit which controls a pair of complementary transistors. The states of the transistors are controlled by the use of a startup-phase voltage and a reference voltage, which are then compared in an error amplifier. The result of the comparison is compared to a sawtooth signal in a comparator, the output of which controls the state of complementary transistors.

Abstract: A charging circuit receives electric power from a solar battery, and charges a secondary battery. A charging current detection unit generates a detection signal that corresponds to a charging current supplied from a DC/DC converter to the secondary battery. A control circuit generates a reference voltage that corresponds to the detection signal. A driving unit generates a pulse signal having a duty ratio that is adjusted such that the voltage output from the solar battery matches the reference voltage, and performs switching of a switching transistor according to the pulse signal. A control circuit adjusts the reference voltage such that the reference voltage becomes greater.

Abstract: A startup circuit in an LDO includes an operational amplifier having an inverting terminal and a non-inverting terminal and an output node. The non-inverting terminal receives a reference voltage. The startup circuit further includes a feedback capacitor coupled between an output node and the inverting terminal and a current source coupled between the inverting terminal and ground such that the current source and the feedback capacitor together control rate of change of an output voltage of the operational amplifier. A comparator is used to stop the rate of change of output voltage after the output voltage reaches a desired value.

Abstract: A method is provided. A low dropout regulator (LDO) is disabled during a first mode, and a first reference voltage is selected and applied to a switched-mode converter during the first mode. Also during the first mode, a first output voltage is generated by the switched-mode converter from a power supply, and a first capacitor is overcharged with the first output voltage. The LDO is then enabled during a second mode. During a first portion of a startup period for the second mode, a second capacitor is charged from the first capacitor, and a second reference voltage is selected and applied to the switched-mode converter. Then, during a second portion of the startup period for the second mode, the second capacitor is charged with the switched-mode converter.

Abstract: Techniques and circuits are described by which analog circuits may be quickly driven to desired states at startup in a fast and accurate manner.

Abstract: A converter unit configured to couple to a photovoltaic panel may include a controller that monitors: an output voltage and output current obtained from the photovoltaic panel by a switching power core within the converter unit, and an output voltage and output current produced by the switching power core. The controller may calculate a desired duty-cycle value based on the monitored values, and implement a mapping algorithm that translates the duty-cycle value to a pulse-width value and a modulus value. The pulse-width value and the modulus value may be used to simultaneously respectively modulate the pulse-width and pulse-period of a pulse-width modulated (PWM) signal, while maintaining an appropriate linear final duty-cycle ratio between the pulse-width and the pulse-period of the PWM signal. The PWM signal may be provided to the switching power core to control the switching of the switching power core.

Abstract: A resonant conversion system is provided, in which a resonant converter receives an input voltage to generate an output voltage, and a buck converter provides the input voltage of the resonant converter, and controls the input voltage to perform an over-current protection process.

Abstract: An improved start-up (soft-start) circuit for use with voltage regulators, and an improved regulator start-up methodology. For example, an apparatus includes a voltage regulator circuit and a start-up circuit operatively coupled to the voltage regulator circuit. The start-up circuit is configured to provide a current signal, during a start-up period, that generates a reference voltage at a reference input of the voltage regulator circuit such that the reference voltage ramps up at a rate substantially equal to a ramp-up rate of a supply voltage coupled to the start-up circuit and the voltage regulator circuit.

Abstract: For a more stable start-up procedure, a switch mode power converter has at least one inductive component including an output inductor L1 and a synchronous rectification element, said power converter comprising a control device and being characterized in that the control device is arranged, at startup of the power converter, to determine a duty-cycle of the control signal, including a normal pulse width of the control pulse, and provide an initial control signal to the at least one switch element that is designed to balance the current in the at least one inductive component of the converter. The initial control signal preferably has a duration of 50% of the normal pulse width.

Abstract: The present invention relates to a switch control device, a power supply device, and a switch control method. A switch control device controls a switching operation of a power switch by using a feedback voltage of an output voltage. In detail, the switch control device generates the feedback current according to the feedback voltage and the feedback signal corresponding to the feedback voltage by using the feedback current. The switch control device compares the sensing signal corresponding to the drain current flowing to the power switch and the feedback signal, and turns off the power switch according to the comparison result. The switch control device increases the feedback gain rather than the feedback current during the gain compensation period after a predetermined gain compensation period, and the gain compensation period is longer than a soft start period in which the output voltage is gradually increased.

Abstract: A regulating apparatus with soft-start and fast-shutdown function is applied to a voltage-supplying apparatus. The regulating apparatus includes a soft-start and fast-shutdown circuit, a regulating circuit, and a ground circuit. When voltages are supplied from the voltage-supplying apparatus to the soft-start and fast-shutdown circuit, the regulating circuit, and the ground circuit, the ground circuit is connected to ground, so that the starting time of the regulating circuit is delayed by the soft-start and fast-shutdown circuit. When voltages are not supplied from the voltage-supplying apparatus to the soft-start and fast-shutdown circuit, the regulating circuit, and the ground circuit, the ground circuit is not connected to ground, so that the regulating circuit is shut down fast by the soft-start and fast-shutdown circuit.

Abstract: In accordance with a bandgap circuit and a method of starting the bandgap circuit, a start signal is continuously supplied to a differential amplifier circuit to start up the differential amplifier circuit that controls a bandgap core circuit until the differential amplifier circuit has started up, and then the supply of the start signal to the differential amplifier circuit is discontinued after the differential amplifier circuit has started up.

Abstract: A control module includes a control unit that is configured to control an electrically adjustable item of furniture, and a switched mode power supply that is configured to supply the control unit. The control unit and power supply are integrated into a common housing. The switched mode power supply is configured to be switched to an idle operating state depending on a ready signal. The switched mode power supply includes, in a second stage, a switched mode regulator component, the supply voltage of which is made available in the idle operating state by a starting circuit in a clocked manner. The starting circuit has an energy store and a resistive element. The energy store and the resistive element are dimensioned so that, in the idle operating state, an interval for charging the energy is longer than an interval for discharging the energy store by the switched mode regulator component.

Abstract: In one embodiment, a startup circuit for a power supply is provided. The startup circuit comprises a resistance coupled between a voltage source and a first node. A first capacitor, coupled to the first node, is operable to be charged by current flowing through the resistance. A first transistor has an emitter, a base, and collector, wherein the collector is coupled to the voltage source and the base is coupled to the first node. A diac circuit, coupled to the emitter of the first transistor, is operable to fire to turn on the first transistor, thereby allowing discharge of the first capacitor through the base-emitter junction of the first transistor. A second capacitor is operable to be charged by current related to a discharge voltage resulting from the firing of the diac circuit. The second capacitor operable to store charge to provide VCC voltage to a controller of the power supply.

Abstract: A power inverter system includes a plurality of power semiconductor switching devices. Each switching device includes a corresponding gate turn off resistance configured to increase during starting up periods of the inverter system such that the open circuit voltage of a corresponding power source providing power to the power inverter system does not exceed the switching device blocking voltage ratings during the corresponding switching turn-off periods. The starting up period is the time required to bring the corresponding power source voltage from its open circuit voltage level to a predetermined voltage which constitutes a safe operating condition for the plurality of power semiconductor switching devices.

Abstract: An operation controller has a reference voltage generator, a starter circuit, and a switch element. The reference voltage generator is connected to an enable terminal to which an enable signal is supplied. After the enable signal is supplied and a start signal is generated, the reference voltage generator generates a reference voltage up to a stable value. After the reference voltage rises to the stable value, it generates a stop signal. When the enable signal is supplied, the starter circuit generates the start signal, and supplies it to the reference voltage generator. When the enable signal is no longer supplied or the stop signal is generated, the start signal is terminated. The switch element has one end connected to the enable terminal and the other end supplied with a prescribed voltage; it turns on when the start signal is generated, and turns off when the start signal is terminated.

Abstract: A DC/DC converter for use in power supply applications employing multiple parallel-connected converters employs a digital controller referenced to the secondary or output side of an isolation boundary and having non-isolated direct connections to secondary side components. The controller directly monitors output voltage and output current and uses feedback control techniques to precisely control these values in a desired manner. The DC/DC converter can implement so-called “droop” current sharing with increased accuracy arising from the secondary-side digital control, so that a desired balanced sharing of current across multiple converters can be achieved. The converter uses calibration establish accurate set points, and any of a variety of additional functions/features to attain operational goals.

Abstract: A synchronous buck regulator includes a voltage regulator, a sample unit, a switch element, a comparison unit, a time delay unit, and a control unit. The sample unit is connected to the external power source for sampling a voltage drop in the external power source. The comparison unit is connected to the sample unit for outputting a result-high signal when the current passing through the sample unit is greater than a predetermined current rating. The time delay unit is connected to the comparison unit for outputting a first result-low signal. The control unit is connected to the time delay unit and outputs a first a low level signal to the switch element according to the result-low signal. The switch element connects the sample unit and the voltage regulator and can isolate the voltage regulator from the external power source when the low level signal is received.

Abstract: Various circuits, including DC/DC converters can include an integrated soft-start circuit. The integrated soft-start circuit includes a PMOS transistor configured to receive a reference signal and control the current to a bipolar junction transistor when the reference signal is in a first state. First and second NMOS transistors are included in the soft-start circuit, and receive the reference signal to turn off (to release from reset) when the reference signal is in the first state. A capacitor coupled in parallel with one of the NMOS transistors controls the soft-start signal. Various different transistors types can be used depending on the desired implementation.

Abstract: A bandgap circuit includes a bias current generating circuit and a complementary start-up circuit. The bias current generating circuit includes a first node and a second node and is arranged to generate a bias current in response to a voltage provided at the first node or a voltage provided at the second node. The complementary start-up circuit is arranged to start-up the bias current generating circuit and includes a first start-up circuit coupled to the first node and a second start-up circuit coupled to the second node. The first and second start-up circuits operate complementarily, so that the second start-up circuit provides the voltage to the second node when the first start-up circuit is unable to provide the voltage to the first node, and the first start-up circuit provides the voltage to the first node when the second start-up circuit is unable to provide the voltage to the second node.

Abstract: A voltage regulator includes a transistor, a comparator, and a compensation circuit. The comparator has a first input terminal coupled to receive a clock signal, a second input terminal, and an output terminal coupled to a control electrode of the transistor. The compensation circuit has a first input terminal coupled to receive a reference voltage, a second input terminal coupled to the output terminal of the voltage regulator, and an output terminal coupled to the second input terminal of the comparator. The compensation circuit has a filter circuit. The filter circuit has a first RC time constant during startup of the voltage regulator, and the filter circuit has a second RC time constant during normal operation. Changing the RC time constant for startup prevents an overshoot of an output voltage of the voltage regulator.

Abstract: A power isolation system and method is disclosed. The system includes a transformer suitable for use in the power isolation system, and a semiconductor device electrically connected to the transformer to provide a reduction of the inrush current associated with powering the transformer, wherein the semiconductor device is activated upon power up based upon the previous shutdown state of the power isolation system to provide a soft start to the transformer, and after activation of the transformer, the semiconductor device is shorted in the system.

Abstract: Methods and circuits related to power regulator start-up are disclosed. In one embodiment, a start-up circuit can include: (i) a delay circuit having a resistor and a capacitor, where the capacitor is coupled between ground and a common node; and (ii) a control chip that receives a reference voltage, and includes an input pin coupled to an input source, an output pin supplying power for a device, and a multiplexed pin coupled to the resistor at the common node to receive an enable signal. The start-up circuit outputs an electrical signal at the output pin based on a comparison of a voltage at the multiplexed pin against the reference voltage, and after a delay time determined by the capacitor and the reference voltage. The voltage at the multiplexed pin can increase continuously with a rising slope determined by input current flowing through the multiplexed pin during a start-up process.