Abstract: A method for operating a switch in a power converter, a drive circuit for operating a switch in a power converter, and a power converter are disclosed. The method includes: driving an electronic switch coupled to an inductor in a power converter based on a feedback signal (SFB) and a crossing detection voltage, wherein the feedback signal is dependent on an output parameter of the power converter and the crossing detection voltage is dependent on a voltage across an auxiliary winding coupled to the inductor; clamping the crossing detection voltage; monitoring an auxiliary current (IAUX) associated with clamping the crossing detection voltage; and detecting an overvoltage when the monitored current reaches a predefined threshold.

Abstract: A power converter, comprising an energy transfer element, an output of the power converter, a power switch, an active clamp circuit, and a first controller. The active clamp circuit comprising a capacitance, a steering diode network coupled to the capacitance and configured to transfer a charge to the capacitance, a clamp switch coupled to the capacitance and configured to transfer the charge stored in the capacitance to the energy transfer element, and an offset element coupled to the clamp switch and configured to provide a path to discharge a capacitance associated with the clamp switch. The first controller configured to output a clamp drive signal to control the turn on and turn off of the clamp switch and a primary drive signal to control the turn on and turn off of the power switch.

Abstract: A power conversion apparatus with oscillation reduction control supplies power to a load through an output end. The power conversion apparatus includes a transformer, a power switch, a control module, and an oscillation reduction control module. A primary side of the transformer receives an input voltage, and a secondary side of the transformer is coupled to the output end. The power switch is coupled to the primary side. The control module is coupled to the power switch, controls the power switch continuously turning on and turning off, and converts the input voltage into an output voltage. When the oscillation reduction control module detects a resonance voltage through the secondary side, the oscillation reduction control module performs an oscillation reduction operation to the resonance voltage to reduce an amplitude of the resonance voltage by a damper.

Abstract: A power converter, comprising an energy transfer element, an output of the power converter, a power switch, an active clamp circuit, and a first controller. The active clamp circuit comprising a capacitance, a steering diode network coupled to the capacitance and configured to transfer a charge to the capacitance, a clamp switch coupled to the capacitance and configured to transfer the charge stored in the capacitance to the energy transfer element, and an offset element coupled to the clamp switch and configured to provide a path to discharge a capacitance associated with the clamp switch. The first controller configured to output a clamp drive signal to control the turn on and turn off of the clamp switch and a primary drive signal to control the turn on and turn off of the power switch.

Abstract: An active clamp flyback controller includes first and second input terminals, a clamp voltage detection circuit, and an overvoltage protection circuit. The first input terminal is adapted to be coupled to a terminal of a clamp capacitor. The second input terminal receives a feedback signal proportional to a voltage across an auxiliary winding of a flyback transformer. The clamp voltage detection circuit is coupled to the first and second input terminals, and detects a clamp voltage as a difference between a voltage at the first input terminal and an input voltage, the clamp voltage detection circuit calculating the input voltage using a signal from the second input terminal. The overvoltage protection circuit is coupled to the clamp voltage detection circuit for comparing the clamp voltage to a threshold and triggering a protection operation if the clamp voltage is greater than the threshold.

Abstract: To operate a switching power supply again automatically (automatic return) after the switching power supply is stopped for protection. A protection circuit 6 includes a bipolar transistor Q1 that becomes ON state and sets current that flows to a photo coupler 62 larger in case that a temperature detection element 63 supplies a detection signal, a control IC 4 that controls a switching element 3, and a protection power supply circuit 66 that includes a condenser C3 that is charged by output voltage from the switching power supply 1. Power supply voltage form the protection power supply circuit 66 is supplied to the temperature detection circuit 63 and the photo coupler 62. Further, in case that voltage value that is changed by the photo coupler 62 is not more than a predetermined value, the control IC 4 stops the switching element 3.

Abstract: A power converter and a control method therefor are provided. The power converter includes a transformer, a primary-side control circuit and a secondary-side control circuit. A primary side of the transformer receives an input voltage, and a secondary side of the transformer generates an output voltage. The primary-side control circuit controls a current switch of a primary winding and switching thereof. The secondary-side control circuit is disposed at the secondary side of the transformer. The secondary-side control circuit comprises a latch circuit. The latch circuit clamps a feedback signal and maintains a clamped status of the feedback signal when an fault event occurs. The primary-side control circuit stops switching the current switch of the primary winding when the feedback signal is clamped, and the latch releases the feedback signal when the output voltage is lower than a default latch voltage value.

Abstract: A controller for use in a power converter includes logic circuits to turn on and off a switch to regulate an output quantity. A first integrating capacitor is charged with a combination of a first current and a second current while the switch is turned on. The first current is proportional to a reset voltage and the second current is proportional to an input voltage. A reference generation circuit including a second integrating capacitor is charged with the first current during a previous switching cycle of the switch. The reference generation circuit generates a reference voltage in response to the second integrating capacitor. A comparator provides a stop signal to the logic circuits to turn off the switch in response to a comparison of a voltage across the first integrating capacitor with the reference voltage.

Abstract: A controlled start-up circuit mechanism in a linear voltage regulator can handle a higher supply voltage at start-up and limits the voltage seen at the devices to be lower than the maximum allowed operation voltage. The circuit may regulate voltage for operating a device coupled to a host when the host supply exceeds that necessary for device operation. The controlled start-up mechanism handles a sudden ramp up or spike of supply voltage relative to the device's operational voltage.

Abstract: A DC-DC converter includes a power conversion circuit for converting a DC input voltage to a DC output voltage; and an active clamp circuit for soft switching a first active switching element of the power conversion circuit and recovering leakage inductance energy of a main transformer of the power conversion circuit. As such, the present disclosure provides a DC-DC converter that reduces the switching loss of the switching elements and effectively recovers the leakage inductance energy, thus increasing the conversion efficiency of the converter.

Abstract: A wireless power transmission device includes a power transmitter, a first transmission unit, a power receiver, a feedback regulator, a receive controller, and a second transmission unit. The power transmitter is for generating power, and the first transmission unit is for wirelessly transmitting power generated by the power transmitter. The power receiver is for receiving and rectifying the power from the first transmission unit. The feedback regulator is for receiving a feedback signal from the power receiver to generate an AC control signal. The receive controller is for receiving the control signal to generate a driving signal. The second transmission unit is for wirelessly transmitting the control signal to the receive controller.

Abstract: Systems and methods are provided for protecting a power conversion system. A system controller includes a first controller terminal and a second controller terminal. The first controller terminal is configured to provide a drive signal to close and open a switch to affect a first current flowing through a primary winding of a power conversion system. The second controller terminal is configured to receive first input signals during one or more first switching periods and receive second input signals during one or more second switching periods. The system controller is configured to determine whether a temperature associated with the power conversion system is larger than a predetermined temperature threshold, and in response to the temperature associated with the power conversion system being larger than the predetermined temperature threshold, generate the drive signal to cause the switch open and remain open to protect the power conversion system.

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 isolated DC-DC converter includes a transformer, a main switch, an active clamp circuit and a control unit. The transformer has a primary winding. The main switch and the active clamp circuit are connected to the primary winding. The active clamp circuit has an auxiliary switch and a clamp capacitor connected in series. The control unit is provided for controlling the main switch and the auxiliary switch. The control unit performs a soft start operation of the converter before a normal operation. The control unit performs anti-saturation control before starting the soft start operation. The anti-saturation control includes an act of controlling the main switch and the auxiliary switch so that the auxiliary switch performs ON-OFF operation with the main switch kept OFF until voltage of the clamp capacitor drops below a level at which the transformer is to be magnetically saturated after starting the soft start operation.

Abstract: A novel system and methodology for providing a volt-second clamp. A DC/DC conversion system configured for producing an output voltage in response to an input voltage has a transformer with a primary winding responsive to the input voltage and a secondary winding for producing the output voltage. The conversion system has a power switch coupled to the primary winding of the transformer and controlled with a converter control signal, such as a PWM control signal. The power switch is further controlled by a comparator that compares an input value supplied to its input with a variable reference value so as to prevent magnetic flux density of the transformer from increasing to an undesired level. The input value of the comparator is produced by a comparator input circuit as a function of the input voltage and an on-time of the power switch. A reference circuit produces the reference value that varies as a function of the input voltage.

Abstract: To make it possible to avoid an unstable state with a simple configuration even one of the phases of the motor fails. A motor drive system in accordance with the present invention includes a motor to which a plurality of phase coils of five phases or more are connected in a star connection, an inverter connected to one end of each of the phase coils, the inverter being configured to convert a DC power into an AC power and supply the AC power to each phase of the motor, a power relay disposed at another end of each of the phase coils, the power relay being configured so as to be able to cut off a supply power to at least one phase coil among the plurality of phase coils of the motor by using a plurality of contact points interposed between the star-connected coils, and a control unit that generates a control signal for the inverter and thereby controls driving of the motor.

Abstract: System and method for regulating an output voltage of a power conversion system. The system includes an error amplifier coupled to a capacitor. The error amplifier is configured to receive a reference voltage, a first voltage, and an adjustment current and to generate a compensation voltage with the capacitor. The first voltage is associated with a feedback voltage. Additionally, the system includes a current generator configured to receive the compensation voltage and generate the adjustment current and a first current, and a signal generator configured to receive the first current and a second current. The signal generator is further configured to receive a sensing voltage and to generate a modulation signal. Moreover, the system includes the gate driver directly or indirectly coupled to the signal generator and configured to generate a drive signal based on at least information associated with the modulation signal.

Abstract: An electrical circuit for manipulating at least one of a voltage and a current on a bus wire comprises a first switch having a first gate, a first source, and a first potential reduction unit. The first potential reduction unit is suitable for lowering a potential difference between the first gate and the first source of the first switch, wherein the lowering of the potential difference is caused by a shutting-off of a first control voltage.

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: A switching mode power supply apparatus includes a transformer, a main switch to adjust power supplied to a primary coil of the transformer, a passive clamp circuit to suppress a voltage stress of the main switch, and a control circuit to disable a clamping operation of the passive clamp circuit in a standby mode of the switching mode power supply apparatus. Power is not consumed in the passive clamp circuit in a standby mode so that power consumed in the standby mode can be remarkably reduced.

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

Abstract: A power converter system includes a converter, a DC link, an inverter, a damping circuit, and a control system. The converter includes an input to couple to a power generation unit and an output to provide a direct current (DC) DC power output. The DC link includes a capacitor coupled to the converter output. A voltage across the capacitor defines a DC link voltage. The inverter includes an input coupled to the DC link. The damping circuit is coupled between the converter and the inverter in parallel with the DC link capacitor. The damping circuit includes a normally closed switching device, and a resistor coupled in series with the normally closed switching device. The control system is coupled to the damping circuit and configured to control the normally closed switching device as a function of at least one operating parameter of the power converter system.

Abstract: A switching power supply device including: a power transformer including a primary winding, a secondary winding, and an auxiliary winding; a switching element which is connected to the primary winding; an output voltage generation circuit which converts, into a direct-current voltage, a voltage induced in the secondary winding; a secondary-side on-time signal generation circuit which generates a secondary-side on-time signal indicating a secondary-side on-time; and a switching control circuit which controls a switching operation of the switching element so that the second direct-current voltage falls within a specified range, wherein the switching control circuit controls the switching operation so that the direct-current voltage becomes equal to or below an overvoltage specified value when the secondary-side on-time becomes smaller than a set value.

Abstract: An energy output circuit and its control method includes a switch device (2), a transformer (4) and a controller (1). The switch device (2) is connected between a primary of the transformer (4) and an input power source in series. The controller (1) calculates an energy output waveform and sends a command according to a request or a level to control the switch device (2), to control the on/off time of the primary of the transformer (4). The transformer (4) is an ordinary low-frequency transformer.

Abstract: A soft-stop overvoltage protection circuit, into which a soft-stop overvoltage detection voltage proportional to a direct current output voltage is input, reduces the output of a multiplier in accordance with the soft-stop overvoltage detection voltage when the soft-stop overvoltage detection voltage exceeds a first threshold value. An overvoltage protection circuit, a second threshold value higher than the first threshold value being set, compulsorily turns off a switching element by outputting an overvoltage detection signal when the soft-stop overvoltage detection voltage exceeds the second threshold value. The soft-stop overvoltage protection circuit compulsorily increases the output of a voltage error amplifier circuit on the output voltage decreasing. When the output of the voltage error amplifier circuit increases suddenly, and the output voltage rises excessively, the soft-stop overvoltage protection circuit decreases the output of the multiplier, thus curbing the rise of the output voltage.

Abstract: System and method for regulating an output voltage of a power conversion system. The system includes an error amplifier coupled to a capacitor. The error amplifier is configured to receive a reference voltage, a first voltage, and an adjustment current and to generate a compensation voltage with the capacitor. The first voltage is associated with a feedback voltage. Additionally, the system includes a current generator configured to receive the compensation voltage and generate the adjustment current and a first current, and a signal generator configured to receive the first current and a second current. The signal generator is further configured to receive a sensing voltage and to generate a modulation signal. Moreover, the system includes the gate driver directly or indirectly coupled to the signal generator and configured to generate a drive signal based on at least information associated with the modulation signal.

Abstract: A voltage reduction detection circuit for a switching power supply includes a first rectifier diode having an anode connected to the output terminal of a secondary winding; a second rectifier diode connected in parallel with the first rectifier diode and having a cathode connected to the output terminal; and resistors arranged to divide the voltage between the cathode side of the first rectifier diode and the anode side of the second rectifier diode. The circuit detects a voltage reduction in an AC power supply (feeding AC power to the switching power supply) based on variation in a voltage resulting from voltage division by the resistors.

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

Abstract: In one embodiment, a PWM controller is configured to inhibit a drive signal responsively to a bulk input voltage remaining at a low value for a time interval.

Abstract: A voltage converter transmits energy in multiple stages using a charge pump so as to decrease the voltage rating of the secondary side of the transformer and reduce the size of the transformer. Meanwhile, the voltage converter stores and recycles the leakage inductance energy by using a snubber circuit so as to increase the efficiency.

Abstract: An example controller for a switched mode power supply includes a zero-crossing detector, a feedback reference circuit, and a drive signal generator. The zero-crossing detector is coupled to generate a zero-crossing signal representative of a length of time that a zero-crossing condition of an input voltage of the power supply exists. The feedback reference circuit is to be coupled to receive a feedback signal and a reference signal, where the feedback signal is representative of an output of the power supply and where the controller is adapted to adjust the reference signal in response to the length of time that the zero-crossing condition exists. The drive signal generator is to be coupled to control switching of a switch included in the power supply in response to an output of the feedback reference circuit to regulate an output of the power supply.

Abstract: In one embodiment, a PWM controller includes a circuit operably coupled to inhibit a drive signal responsively to a bulk input voltage remaining at a low value for a time interval and to re-enable the drive signal subsequently to the time interval responsively to the bulk input voltage increasing to greater than the first value subsequently to the time interval. In another embodiment, a method of forming a PWM controller includes configuring the PWM controller to use a clock signal to form a drive signal and to sense a bulk input voltage decreasing to no greater than a first value and to disable the drive signal without disabling the clock signal responsively to the bulk input voltage remaining no greater than the first value for a time interval.

Abstract: A low-cost integrated circuit is used as a secondary side constant voltage and constant current controller. The integrated circuit has four terminals and two amplifier circuits. A first amplifier circuit is used to sense a voltage on a FB terminal and in response to cause a first current to flow through an OPTO terminal. A second amplifier circuit is used to sense a voltage between a SENSE terminal and a SOURCE terminal and in response to cause a second current to flow through the same OPTO terminal. The FB terminal is used for output voltage feedback and is also used to supply power onto the integrated circuit. The SOURCE terminal is used for output current feedback and is also used as power supply return for the integrated circuit. The cost of the integrated circuit is reduced by having only four terminals.

Abstract: To provide a power supply circuit which can be applied worldwide without using a high withstand voltage switching element and can supply a load device with stable power. A charging section is arranged between a turn-off capacitor and a load coil. The charging section has the anode connected to the positive terminal of a feedback coil and the cathode connected to the cathode of a zener diode. Thus, when a voltage of a commercial power supply is high, the charging section operates, the turn-off capacitor is quickly charged, an on-period of a transistor is shortened, and an excessive voltage is prevented from being applied between the drain and the source of the transistor. At the same time, an output characteristic indicating relationship between the voltage of the commercial power supply and a current flowing in the load device is permitted to be flat.

Abstract: In one embodiment, a power converter system comprises an input terminal operable to connect to a DC power source and an output terminal at which an output voltage can be provided. An active clamped forward converter is operable to provide forward power flow from the DC power source to the output terminal. A flyback converter is operable to provide backward power flow from the output terminal to the DC power source. The active clamped forward converter and the flyback converter cooperate to generate a rectified sinusoidal waveform at the output terminal.

Abstract: A hysteretic buck converter provides improved regulation control, in particular for buck converter standby operation. A comparison circuit compares the output voltage of the buck converter to a waveform that is generated from an indication of the output current of the converter, so that the turn-on time of the converter is advanced as the output current demand increases. The resulting action anticipates a reduction in output voltage due to the increased current, preventing an excursion of the output voltage below the ripple voltage minimum. The turn-off time of the converter is controlled by an upper threshold that limits the ripple voltage maximum. The output current indication may be a measurement of output current, or may be a dynamic value calculated from the input voltage and the output voltage waveform.

Abstract: An example power supply includes a controller and a detection circuit. The controller includes a sense terminal coupled to provide a sense terminal current representative of an input voltage of the power supply during normal operation. The detection circuit is external to the controller and is coupled to the sense terminal. The detection circuit includes a Zener diode coupled to conduct a current to adjust the sense terminal current during a fault condition, where during the fault condition the controller is responsive to a measured impedance of the detection circuit which is determined in response to the sense terminal current.

Abstract: Subject of the invention is a multi-resonance power supply with integral quality factor limiter, designated for transformation of direct voltages, characterised by high immunity to overload and rapid load changes. The power supply has the (TS) isolating transformer, with its primary winding connected to the main (OR) resonant circuit having at least one node connected with the set of (K1), (K2) current switches, via the serial resonant circuit, whereby at least one component of the serial resonant circuit is connected to the (DON) diode voltage limiter.

Abstract: A flyback converter having an active snubber includes a transformer to receive input power. The transformer has a primary winding at a first side. The active snubber is coupled in parallel with two ends of the primary winding and has a first circumferential circuit coupling in parallel with the primary winding, a second circumferential circuit and a zero voltage switch unit. The second circumferential circuit is controlled by the zero voltage switch unit and incorporated with the first circumferential circuit to form double damping paths to reduce current and prevent resonance that might otherwise occur to a single circumferential circuit and the secondary side of the transformer.

Abstract: A converter and a driving method thereof are provided. The converter can determine the output short state of the converter after the soft start is finished by using a detection signal that corresponds to an input signal while a switched is turned on and that corresponds to an output signal while the switch is turned off, so as to convert the input signal into the output signal according to a switching operation of the switch. The converter can determine the overload state of the converter by using a feedback voltage corresponding to the output signal, and terminate the switching operation when the converter is in an output short state or overload state.

Abstract: The invention concerns a circuit for detecting an overload in a load supplied by a switched-mode power supply, comprising: a first comparator of a first voltage based on the supply voltage of the load relative to a first threshold, supplying a regulating signal to a pulse generator controlling the switched-mode power supply; a second comparator of a second voltage relative to a second threshold, supplying a signal indicating the presence of an overload; and means for automatically controlling said second voltage by a third threshold lower than the second and higher than the first, and for deactivating the second comparator as long as said automatic control is maintained.

Abstract: Provided is a high voltage power supply which includes a controller to provide a PWM signal and a power signal, an input unit to receive the PWM signal provided from the controller, a comparison unit to control output of the power signal supplied from the controller by comparing a signal filtered to a DC voltage by the input unit to a voltage reference signal, a transformation unit to transform the power signal output from the comparison unit, and a rectification unit to rectify the signal output by the transformation unit, wherein the high voltage power supply further includes a power input delay unit to delay the supply of the power signal to the comparison unit by a predetermined time from when the power supplied from the controller for input into the comparison unit.

Abstract: The present invention provides a switching power supply device including a switching element, a control circuit controlling the switching element, a transformer having an auxiliary winding, a potential clamp circuit connected to one of outputs of the transformer, a delay capacitor connected to an output of the potential clamp circuit, a potential detection circuit detecting a potential at the delay capacitor, and an overload protection actuation circuit realizing overload protection. During an overload, the delay capacitor is charged only by ringing of the auxiliary winding, generated immediately after the switching element is turned off, through the potential clamp circuit. Then, the potential detection circuit supplies an actuation signal to a latch stop circuit by detecting that the potential at the delay capacitor rises. The latch stop circuit latches and stops the switching operation of the switching element to realize the overload protection when the actuation signal is fed into the latch stop circuit.

Abstract: A plurality of arrangements for detecting an overload of energy supplied to an output part enables selecting latch-off or auto-recovery overload protection by the operation of a switching device. When the drain current peak of the switching device exceeds a predetermined level denoting an overload, the FB pin voltage also rises to latch off, and when the drain current peak then reaches a maximum level, the CC pin voltage drops to a predetermined level and limits the oscillation period of the switching device because output power cannot be increased even if the load increases further. Latch-off overload protection can be applied when the drain current peak exceeding a predetermined level is detected, and auto-recovery overload protection can be applied when the CC pin voltage is detected to drop to a predetermined level.

Abstract: A protection scheme to protect pulse width modulated drives is described. The scheme is implantable in both hardware and software and combinations thereof. The semiconductor devices of the drive are protected from transient signals such as power line spikes and loss of line. The present scheme uses an adaptive technique to determine the normal or steady state distortion (transients and harmonics) value in an unfiltered power signal. The present distortion value is compared to the normal distortion. If the present distortion exceeds the steady state value by a given amount, then the drive is placed in freewheel mode to protect the semiconductor devices in the drive.

Abstract: An AC/DC power supply with over-voltage protection includes a voltage converting circuit and a digital latch control circuit. The voltage converting circuit has a first-side winding, a second-side winding, and an auxiliary winding for providing a supply voltage according to the AC input voltage. The digital latch control circuit is coupled to the voltage converting circuit and utilized for latching a voltage level of the supply voltage at a first predetermined level according to an over-voltage protection (OVP) trigger signal, where the voltage converting circuit is disabled when the voltage level is latched at the first predetermined level.

Abstract: The present invention provides an overpower-protection circuit and a power supply apparatus having the same. The power supply apparatus comprises a rectifier, a transformer and an overpower-protection circuit The overpower-protection circuit comprises a converter having a converter input electronically coupled to the rectifier and a converter output, a photo coupler having at least a first terminal coupled with the converter output, and having an output terminal, and a clipper electrically coupled across said terminals of the photo coupler for keeping the converter output below a predetermined voltage.

Abstract: A DC-DC converter for overvoltage protection is provided with a primary control circuit 12 which comprises an impedance controller 31 and a protective circuit 41 for ceasing operation of primary control circuit 12 when power source voltage VCC on primary control circuit 12 exceeds a predetermined voltage level. Impedance controller 31 comprises a potential detector 32 for picking out power source voltage VCC to primary control circuit 12 to produce a detection signal; and an impedance adjuster 33 for adjusting power input impedance Z in primary control circuit 12 in response to the detection signal from potential detector 32 to repress rapid rise in power source voltage on primary control circuit 12.

Abstract: The present invention discloses an active peak voltage-limiting clamp circuit, which comprises a primary switch unit and a secondary switch unit that are used to control the coil current of a transformer, wherein a signal acquisition unit, a zero-point decision unit, a feedback unit and a pulse control unit are used to control the turn-on periods of the primary switch unit and the secondary switch unit; thus, the turn-on period of the primary switch unit is separated from the turn-on period of the secondary switch unit, and a buffer interval for the transient voltage variation is formed therebetween.

Abstract: A system for transferring an alternating voltage into a direct voltage includes a rectifier, a filter, a transformer, a switch, a switch control circuit and a voltage feedback circuit. The rectifier connects to a main power supply device and rectifies the alternating voltage into a transient direct voltage. The filter filters out a noise from the transient direct voltage and produces a filtering direct voltage. The transformer transfers the filtering direct voltage into a working direct voltage. The switch which has a turn-on status and a cutoff status is used to control the current which goes through the transformer. The switch control circuit is used to control the switch be in the turn-on status or the cutoff status. The voltage feedback circuit drives the switch controlling circuit in accordance with the transformer's voltage and diminishes a switching loss from the switch.