Abstract: A system includes an electrical component, a MOV, a voltage sensor, and a circuit. The MOV is connected in parallel to the electrical component. The voltage sensor detects a voltage over the MOV and the electrical component. The circuit removes power in response to the voltage sensor detecting the voltage over the MOV and the electrical component being greater than a threshold voltage for a length of time greater than a threshold length of time. Removing power prevents the MOV from releasing one or more of smoke, smell, and sound. The MOV is thus not damaged as a result of a power surge. The system may be a power supply, or another type of electrical system. The electrical component may be a capacitor, or another type of electrical component.

Abstract: Aspects of the disclosure provide a circuit. The circuit includes a transistor configured to control energy entering the circuit from a power supply, a capacitor coupled with the transistor to store the energy that enters the circuit, and a protection circuit configured to counteract a voltage change of the transistor that is caused by a step voltage change in the power supply. In an embodiment, the protection circuit operates independent of the stored energy on the capacitor.

Abstract: An offline AC-DC converter circuits including an overvoltage detection module, a current limiting module, a PWM module and a switch control module coupled to the above modules. The overvoltage detection module, the current limiting module and the PWM module share a common input terminal. The sampled current signal and the sampled voltage signal are provided at the common input terminal by way of time-division multiplexing. With the time-multiplexed terminal, overvoltage detection for the output voltage is performed during the period when the power transistor is cut off and a current through the power transistor is detected during the period when the power transistor conducts. The two signals are input by way of time-division multiplexing, which are not affected by each other. Accordingly, overvoltage in the output voltage can be precisely detected without additional terminals, and thus the overvoltage can be controlled.

Abstract: A current-driven synchronous rectifying drive circuit designed for a T-type voltage doubler rectifier with an energy feedback circuit including a clamp and energy feedback circuit, a high frequency transformer, a current transducer, an energy storage capacitor, an output capacitor, a first and a second synchronous rectifier, and a first drive circuit connected to the first synchronous rectifier and a second drive circuit connected to the second synchronous rectifier.

Abstract: Owing to the property of bidirectional conduction under the saturation mode, synchronous rectifiers in conventional power converters usually suffer from a reverse current under light loads or a shoot-through current under heavy loads. The reverse current may degrade the converter efficiency and the shoot-through current may damage synchronous rectifiers. The present invention discloses a unidirectional metal oxide semiconductor field effect transistor (UMOS), which comprises a metal oxide semiconductor field effect transistor (MOS), a current detection circuit and a fast turn-off circuit. The current detection circuit detects the direction of the current flowing through the MOS. When a forward current is detected, the fast turn-off circuit is disabled and the channel of the MOS can be formed. When a reverse current is detected, the fast turn-off circuit is enabled and the channel of the MOS cannot be formed.

Abstract: A method and a device to compensate for an asymmetrical DC bias current in a multi-phase transformer. The transformer is connected between an AC power system and an AC/DC or DC/AC high voltage converter. For each phase of the AC side of the transformer a current quantity is determined. The current quantity reflects the time dependent behavior of the magnetizing current in the phase. Time intervals in the current quantity are determined during which the current quantity reaches a positive or a negative maximum, respectively. A DC magnetizing quantity is determined from a difference between the amplitude of the positive maximum and the amplitude of the negative maximum.

Abstract: A method for protecting a converter device comprises the steps of: detecting an alternating current signal; when the alternating current signal is abnormal, generating an activating signal according to the abnormal alternating current signal; generating a control signal according to the activating signal; and controlling at least one synchronous rectifying power switch of the converter device according to the control signal. Furthermore, a converter device which implements the method is provided.

Abstract: A power supply protection device for an electric appliance includes a switching circuit for establishing an electrical connection to receive an external voltage from the external power supply and output the external voltage to the electric appliance, a detecting circuit for disabling the switch circuit to break the electrical connection when determining the external voltage is equal to or higher than a predetermined value, and an alert circuit for generating an alert signal when the electrical connection is broken and outputting the alert signal to a user.

Abstract: An inrush current protection circuit for a polyphase alternating current power system may include a plurality of current limiting resistors, each of which is electrically coupled in series between a respective one of a plurality of phases of the polyphase alternating current power source and a respective input of a polyphase transformer rectifier unit. The circuit may also include a plurality of power switches, each of which is electrically coupled in parallel with a respective one of the current limiting resistors, such that when each of the power switches is closed, essentially no electrical current flows through the respective current limiting resistor. The circuit may also include a power switch controller configured to control each of the power switches to be open such that an inrush current passes through the respective current limiting resistor rather than the power switch, and to be closed after a time delay has passed.

Abstract: Disclosed is a power regulating apparatus, which is connected between an AC power and a load, for supplying the regulated AC power to the load. The power regulating apparatus includes a first regulating means provided to regulate the input AC power source when the AC power is at a normal power level, and a second regulating means provided to transmit an electric power to the load from a power storage means when the AC power is at a power level lower than the normal power level. Thus, the power regulating apparatus is capable of providing the load with an expected high quality electric power in all cases of AC power variation.

Abstract: An electric power transmission system includes at each end of a high voltage direct current transmission line including three conductors, a converter station for conversion of an alternating voltage into a direct voltage for transmitting direct current between the stations in all three conductors. Each station has a voltage source converter and an extra phase leg connected between the two pole conductors of the direct voltage side of the converter. A third of the conductors is connected to a midpoint between current valves of the extra phase leg. An arrangement is adapted to control the current valves of the extra phase leg to switch for connecting the third conductor either to the first pole conductor or the second pole conductor for utilizing the third conductor for conducting current between the stations.

Abstract: A DC electrical power system has a power generator converter system, a positive supply rail extending from the converter system, a negative supply rail extending from the converter system, and a midpoint earthing arrangement operatively connecting to the supply rails. The earthing arrangement is connected to earth by a solid earth connection. The network further has a first protective device on one of the supply rails which in case of a fault is operable to interrupt current flowing on that rail, and a second protective device on the earthing arrangement which in case of a fault is operable to interrupt current flowing to earth through the solid earth connection.

Abstract: The present invention relates to a switch control device and a converter including the same. According to an exemplary embodiment of the present invention, the switch control device includes a PWM controller for forcing a power switch to turn on when the power switch is turned off during a predetermined period, a current sensor for determining whether a current flows through the power switch, and a conditional counter for determining that an input voltage is input to a power transmission element by using a sense result of the current sensor and a number of times that the PWM controller turns on the power switch by force.

Abstract: Systems and methods are presented for an improved high power density power adapter. On one potential embodiment, an improved power adapter includes an AC input; a rectifier coupled to the AC input; a power factor correction circuit coupled to the rectifier; and a burst switch circuit coupled to the power factor correction circuit. The burst switch circuit provides power to a DC output via a set of FET drivers, a set of FETs, and a transformer and may provides power exclusively in a burst mode using a feedback input from the DC output. The transformer may be composed of windings coupled to the set of FETs, and additional windings embedded in the PCB and coupled to the first winding. Certain windings may comprise a conductive ribbon that loops around a transformer core. Additional embodiments may include monitoring circuits and multiple outputs.

Abstract: A method, voltage source converter and computer program product for limiting the current in a DC power transmission system are disclosed. The voltage source converter has an AC side and a DC side and a fault current path between these sides. It furthermore includes a control unit and at least one switching unit of a first type provided in the fault current path and that includes a primary switching element together with an anti-parallel secondary controllable rectifying element. Based on a fault being detected in the DC power system when the primary switching elements of the converter are blocked, the control unit changes the control of the controllable rectifying element from acting as a non-controllable rectifying to acting as a controllable rectifying element.

Abstract: An output voltage monitoring circuit monitors an output voltage of a capacitor charging circuit. A first sample-and-hold circuit samples and holds a voltage of a connection point of a primary coil of a transformer and a switching transistor. A first monitoring comparator compares output of the first sample-and-hold circuit with a predetermined first reference voltage. When the output of the first sample-and-hold circuit exceeds the first reference voltage, a signal processor executes predetermined signal processing. The first sample-and-hold circuit starts a sampling period after a predetermined first time has elapsed after the switching transistor is turned OFF. When a voltage drop across a detection resistor reaches a third reference voltage, the first sample-and-hold circuit ends the sampling period.

Abstract: A high-power modulation system includes drive circuitry that receives input signals from the signal source via a series of transformers. The drive circuitry amplifies the input signals and provides the resulting amplified signals to the high-power switch. The switch includes a series of stacked switching elements, each with a control terminal, first and second current-handling terminals, and feedback path extending between the first current-handling terminal and the control terminal. The feedback paths work in concert to turn the switches on and off together to prevent excessive voltage from developing across one or a subset of the switching elements. The feedback path includes a resistor that dampens the bandwidth of the feedback path to reduce turn-off and turn-on ringing and oscillation. The damping resistor may be coupled in series with a diode that holds charge against the control terminal of the switching element.

Abstract: A method for controlling a voltage transformer for operating a switchable load having at least one inductance and a switch, which is activated by a digital control device. When the switch is closed, a magnetizing current flows through the inductance. When the switch is open, a demagnetizing current flows through the inductance. The method comprises the steps of measuring the demagnetizing time of the inductance and, when a maximum value of the demagnetizing time of the inductance is exceeded, storing such an ocurrence as a fault. The load is disconnected by the control device when a predetermined maximum frequency of faults is exceeded.

Abstract: A switch mode power supply (15) employs a rectifier (20), a converter (50) and converter driver (60). The rectifier (20) generates a rectified supply voltage (VRS) based on an in-line voltage (VLN), and the converter driver (60) generates one or more driving voltages (VDR) to facilitate a conversion by the converter (50) of the rectified supply voltage (VRS) to a DC bus voltage (VDC) based on the driving voltage(s) (VDR). The converter (50) may include a transient voltage suppression device (52) to suppress the rectified supply voltage (VRS) in response to an abnormal line condition of the switch mode power supply (15), and the converter driver (60) may include a free-oscillating suppression device (61) to suppress the one or more driving voltages (VDR) in response to a free-oscillating condition of the converter driver (60).

Abstract: A fault tolerant DC power system includes a permanent magnet generator (PMG), a first contactor in electrical communication with the PMG, an active rectifier in electrical communication with the first contactor, a second contactor in electrical communication with the first contactor, and a motor drive in electrical communication with the second contactor. The first contactor is configured to sever electrical communication between the PMG and the active rectifier and the second contactor is configured to establish electrical communication between the PMG and the motor drive.

Abstract: [Problem] To provide a power converter capable of suppressing voltage dropping of the smoothing capacitor and suppressing a rush current at the time of power recovery, [Means for Resolution] When it is determined that a bus voltage Vdc detected by a DC voltage detecting unit 24 is equal to or less than a predetermined reference voltage, a control device 20 allows a DC load control unit 23 to stop an operation of a DC load 30.

Abstract: Methods and apparatus are provided for operation of a voltage source inverter. A method of operating a voltage source inverter having an output with multiple voltage phases having a DC voltage level, the method comprising sensing a low output frequency condition; determining a DC voltage offset responsive to the low output frequency condition; and applying the DC voltage offset when operating the voltage source inverter resulting in a change to the DC voltage level of the multiple voltage phases.

Abstract: The present invention relates to a thermal shutdown unit, a switch controller including the same, and a method controlling a thermal shutdown protection operation. The present invention determines the operation state of an SMPS to vary a reference temperature for controlling a thermal shutdown protection operation according to an operation state of the SMPS.

Abstract: An apparatus comprises: a voltage monitoring unit for monitoring input direct-current voltages of first and second converters whose output ends are connected in parallel to each other; and a judgment control unit for judging that an output diode of the first converter is short-circuited, when an input direct-current voltage monitored by the voltage monitoring unit with respect to the first converter rises up to a post-step-up voltage stepped up by the second converter during a step-up operation of the second converter.

Abstract: A device has a converter which is connected to a direct voltage circuit through a short-circuit protection unit. The short-circuit protection unit is arranged at least partially in the direct voltage circuit and is provided in the direct voltage circuit to suppress short-circuit current flowing through the converter. The device contains one or more controllable power semiconductors, wherein a protection element is arranged in parallel to at least one of the controllable power semiconductors. The device prevents the negative effects of a short circuit occurring in the direct voltage network in a particularly reliable manner. For this purpose, the protection element is an energy store.

Abstract: An output protection circuit used for a power converter having an operational amplifier, a diode, a number of voltage-dividing resistors, and a switch tube. In this circuit, the voltage-dividing resistors are connected in series to form a voltage-dividing network, of which one node is connected to a reference level end Vref of a PWM control module of the converter, while the other node is grounded. A voltage dividing point M is coupled to an inverting input end of the operational amplifier AR1.

Abstract: The power input stabilizing circuit provides a first resistor at the input terminals to suppress impulse current. Then, the power passes through a power input limiting circuit including a non-polarity capacitor, a rectifier circuit formed by diodes, and a polarity capacitor so as to provide a current within a specific range to a load. A constant current circuit including a third resistor, a diode, a fourth resistor, and a transistor is then employed to stabilize the load current. The performance and durability of the electrical or electronic appliance using the power input stabilizing circuit are therefore enhanced significantly.

Abstract: An embodiment of the invention relates to a switch-mode power converter including an inductor and an external rectifying diode. A series arrangement of a resistor and a switch are coupled in parallel with the external rectifying diode. The resistor and the switch enable continuous conduction mode, even at substantially no output current. A comparator senses a current level in the resistor. When the current level crosses a threshold level, the power converter is shut down. The current level is sensed with a second resistor coupled to a current source to produce a current sensing arrangement dependent on a ratio of resistances. Advantageously, the current level is sensed with clamp circuits coupled to the comparator, each clamp circuit including a series circuit arrangement of a field-effect transistor with a gate coupled to a voltage source.

Abstract: A power supply employs an error detecting circuit to output an error signal when detecting an overvoltage or overcurrent occurred in one of output powers and employs a latch trigger circuit to cause the power supply to enter a latch mode when receiving the error signal. The power supply will keep the latch mode when entering the latch mode until the AC power VAC is removed. In addition, the power supply employs the error detecting circuit to provide the accurate safety threshold value by the constant current source with temperature compensation function and stable constant current output.

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: A circuit arrangement for a power-supply unit for generating at least one DC voltage from an AC voltage of a power grid includes a switching element that switches a load current of the power-supply unit, a current-limiting element connected in series to the switching element that limits a current surge when the switching element is turned on, a bistable first relay connected in parallel to the switching element and the current-limiting element that retains the load current, and a control circuit that switches the power-supply unit from a first operating state, in which no load current flows from the power grid to the power-supply unit, to a second operating state in which a load current for generating a DC voltage flows from the power grid to the power-supply unit, wherein the control circuit turns on the switching element for a first time period during switching of the power-supply unit from the first to the second operating state, to turn the bistable relay on during the first time period, and to turn the s

Abstract: Power conversion systems and diagnostic techniques are presented for detecting suspected converter faults when a pre-charge circuit is engaged during system startup, in which known or estimated system characteristics are used to derive expected converter voltage values or rate of change values and the levels are measured during startup to ascertain whether the pre-charge circuit or other converter components are faulted.

Abstract: An uninterruptible power supply (“UPS”) has a phase-controlled rectifier coupled to a source of AC power and having an output providing a DC bus, the output of the phase-controlled rectifier coupled to an inverter. A first controller generates a firing angle for the rectifier and a fuzzy logic controller generates a firing angle for the rectifier. In an aspect, the rectifier is controlled by the firing angle generated by the first controller during normal operating conditions of the UPS and the rectifier is controlled by the firing angle generated by the fuzzy logic controller during abnormal operating conditions of the UPS. The abnormal operating conditions can include loss of a direct DC bus voltage measurement and or a period of time after the UPS experiences a large load change.

Abstract: A synchronous rectification control circuit is connected with a secondary-side rectification circuit and includes a driving circuit, a dead-time acquisition circuit, and a zero-voltage detection circuit. The driving circuit includes a differentiating circuit, a first comparator, and a capacitor, wherein the differentiating circuit generates a signal to the first comparator and the capacitor functions to charge and discharge to form a cycle. The dead-time acquisition circuit includes a second comparator and a third comparator, wherein the second comparator has a positive input connected to an output of the first comparator of the driving circuit, the second comparator has an output connected to a positive input of the third comparator, and the third comparator has a negative input connected to the output of the first comparator to acquire a dead-time signal.

Abstract: A single-stage integrated circuit drives LED sources in a constant power mode to eliminate the need for LED current sensing, while reshaping the waveform of the inductor current near line zero crossing to achieve high power factor. The integrated circuit achieves substantially constant input power my maintaining a constant voltage at a power factor corrector controller through an input voltage feedforward system. Accordingly, the disclosed circuit provides a high power factor, high efficiency, simple, and cost-effective solution with substantially consistent input power for both isolated and non-isolated offline LED applications.

Abstract: A welding power supply includes an input rectifier that receives sinusoidal or alternating line voltage and provides a rectified voltage. A pre-regulator provides a dc bus and a convertor, such as a boost convertor, provides a welding output. The pre-regulator is an SVT (slow voltage transition) and an SCT (slow current transition) switched convertor. It may include a snubber circuit having a diode that is SVT switched. Also, the boost convertor may be SVT and SCT switched. The pre-regulator preferably includes a power factor correction circuit. The power source includes, in one embodiment, an inverter having a snubber circuit having a first switch in anti-parallel with a first diode, and a second switch in anti-parallel with a second diode. The first switch and first diode are connected in series with the second switch and the second diode, and the first and second switches are connected in opposing directions, to form a switched snubber.

Abstract: A controller for controlling a controlled switching device functioning as a synchronous rectifier of alternating current, the controller comprising a control circuit for sensing the direction of current through the controlled switching device, the controlled switching device comprising a MOSFET having a conduction channel and a parasitic body diode and having two main current carrying terminals and a control terminal, the control circuit generating a control signal provided to the control terminal to turn on the controlled switching device approximately when current begins to flow in a first direction through the controlled switching device and turn off the controlled switching device approximately when current begins to flow in a second opposite direction through the controlled switching device, further wherein the control circuit for sensing the direction of current through the controlled switching device main current carrying terminals comprises a sensing circuit coupled across the controlled switching dev

Abstract: A driver circuit included in a power supply having a rectifier coupled to a single phase AC input voltage is disclosed. An example driver circuit includes a drive signal generator to generate a drive signal to be coupled to a variable impedance element. A voltage sensor is coupled to the drive signal generator and is to be coupled to sense a voltage across a high voltage capacitance. The driver circuit is to be coupled to control the variable impedance element in response to the voltage sensor. A low voltage capacitance is allowed to receive current from the input if the sensed voltage is less than a second threshold value. The low voltage capacitance is prevented from receiving current from the input if the sensed voltage is greater than a first threshold value.

Abstract: Provided is a power conversion device capable of detecting a short circuit failure and protecting from the same securely. The power conversion device includes: a three-phase bridge type power conversion circuit including a semiconductor switch including a first main terminal, a second main terminal, and a control terminal; a control circuit for controlling an operation of the semiconductor switch; and a voltage detection circuit for monitoring a voltage between DC terminals of the power conversion circuit, in which the control circuit has a protection function of turning off the semiconductor switch if the voltage between the DC terminals of the power conversion circuit, which is detected by the voltage detection circuit, is lower than a predetermined value for a predetermined period of time or longer.

Abstract: Each of three-phase arm of an inverter has first and second switching elements connected in series together at a connection point to the corresponding phase coil of the three-phase motor. Control device turns on the first switching element of the i-th (i is a natural number smaller than four) for a predetermined time period, and determines that the second switching element of the i-th arm has a short fault, when an overcurrent exceeding a predetermined threshold is detected within the predetermined time period. The predetermined time period is shorter than a time period from a time point of turning on the first switching element of the i-th arm to a time point of attaining the predetermined threshold by a current flowing through a path extending from a power supply line through the second switching element of the remaining arm other than the i-th arm to a ground line.

Abstract: DC power for low power loads is provided for vehicles such as snowmobiles where the electrical system includes primarily AC power. DC voltage is provided for gauges and similar loads even though the peak value of the AC is below a desired level. Rectification and regulation of some energy from the alternator is used for supplying the DC power at a desired DC voltage that is above an alternator zero to peak value. A capacitor and a diode are connected in parallel from the alternator with rectifying circuit portions for supplying power to the DC load. A DC voltage monitor senses the DC voltage supplied to the DC load and prevents the DC voltage from rising above the desired voltage by controlling the first rectification, the second rectification, or both.

Abstract: A device for converting an electric current has a phase module, which in turn has an alternating current connection and at least one direct current connection connected to an intermediate direct current circuit. The device further has an energy accumulator. A phase modulation path is formed between each direct current connection and each alternating current connection. Each phase modulation path has a series connection of submodules, which each have a power semiconductor. A semiconductor protective device is provided in parallel connection to power semiconductors of each submodule. A control unit actuates the semiconductor protective device, and energy accumulator(s) are equipped for supplying energy to the control unit. The device safely prevents damage from a short circuit on the direct-current side, even when the supply grid is connected, because a direct current connection of each phase module is connected to the intermediate direct current circuit via a direct-current switch.

Abstract: Power conversion systems and diagnostic techniques are presented for detecting suspected converter faults when a pre-charge circuit is engaged during system startup, in which known or estimated system characteristics are used to derive expected converter voltage values or rate of change values and the levels are measured during startup to ascertain whether the pre-charge circuit or other converter components are faulted.

Abstract: An output protection circuit used for a power converter having an operational amplifier, a diode, a number of voltage-dividing resistors, and a switch tube. In this circuit, the voltage-dividing resistors are connected in series to form a voltage-dividing network, of which one node is connected to a reference level end Vref of a PWM control module of the converter, while the other node is grounded. A voltage dividing point M is coupled to an inverting input end of the operational amplifier AR1.

Abstract: An apparatus for synchronous rectifying of a soft switching power converter is provided. An integrated synchronous rectifier includes a power transistor coupled between a transformer and the output of the soft switching power converter, and a controller receiving a pulse signal to switch on/off the power transistor. A switching control circuit generates the pulse signal in response to a current signal, and generates drive signals to switch the transformer in response to a switching signal. An isolation device is coupled to transfer the pulse signal between the switching control circuit and the integrated synchronous rectifier. The switching signal is used for regulating the power converter and the current signal is correlated to the switching current of the transformer.

Abstract: A rectifier filter control device for a power supply that includes: A saturable inductor (swing choke), capacitors; and rectifiers connected to a rectifier filter circuit. The rectifier filter circuit further includes two electronic switches, which are respectively connected to two terminals of each of the two rectifiers. Should a reverse current flow back into the rectifier filter circuit, then the two electronic switches assume off states at different time sequences, thereby preventing the reverse current flow from burning out the two electronic switches.

Abstract: A clamp circuit for use in a DC/DC voltage converter having a first converter output including a first node and a second node, and a second converter output including a third node a fourth node. The clamp circuit includes a positive voltage output node coupled to the first node, a negative voltage output node coupled to the fourth node, a neutral voltage output node, a first diode coupled between the positive voltage output node and the third node, a second diode coupled between the negative voltage output node and the second node, a first inductor coupled between the second diode and the neutral voltage output node, and a second inductor coupled between the first diode and the neutral voltage output node.

Abstract: The present invention reliably reduces output power during an overload, due to overload protection in which an on-time of a switching element 1 is reduced or the peak value of a switching current is lowered by reducing the minimum value of the on-period of the switching element 1.

Abstract: An objective is to provide a pressure-contact type rectifier in which solder that increases the environmental load is not used, and neither burning nor breakage of a rectifying device occurs, even if temperature of the rectifying device increases due to current flowing or force towards outside the rectifying device is applied to a lead end, etc. By providing an electrically conductive friction reducer on at least one electrode face of the rectifying device, the temperature increase can be prevented, and the friction at the contact face can be reduced. Moreover, by providing a flexible portion on the lead end outside a cap, and fixing the flexible portion to the cap, the contact area between the lead and the rectifying device can be kept constant. As a result, a pressure-contact type rectifier in which neither burning nor breakage of the rectifying device occurs can be obtained.

Abstract: A circuit (20) for powering a load (50) includes a rectifier circuit (200), a voltage clamping circuit (300), and a DC-to-DC converter (400) such as a buck-boost converter. Voltage clamping circuit (300) is coupled between the rectifier circuit (200) and the DC-to-DC converter (400), and functions to prevent the input voltage (VIN) of the DC-to-DC converter (400) from exceeding a predetermined acceptable level, so as to protect the DC-to-DC converter (400) from damage due to transients in a voltage (VAC) provided by an AC line source (40). Preferably, voltage clamping circuit (300) is realized by an arrangement that includes a voltage divider circuit (320), a voltage sensing circuit (340), and an energy-limiting circuit (360), and is well-suited for use in power supplies and in electronic ballasts for powering gas discharge lamps.