Abstract: A power module includes at least two pairs of two power semiconductor units (PSUs), each of which includes a switch element and a rectifier element connected in anti-parallel. One of two PSUs in one pair and one of two PSUs in another pair are connected in series between primary and secondary positive terminals of a DC/DC voltage converter. Another of two PSUs in the one pair and another of two PSUs in the another pair are connected in series between the primary positive terminal and a secondary negative terminal in a direction reverse to a direction of the ones of two PSUs. Control is performed to suppress transient voltage fluctuations that occur in switching between the state where the polarity of a reactor current is only one of positive and negative and the state where the polarity remains one of positive and negative.

Abstract: A system and method are provided for regulating a voltage level at a load. The method configures a current control mechanism to generate a current through a first inductor and a second inductor that are coupled in series and configures a voltage control mechanism to provide a portion of the current to regulate the voltage level. The second inductor isolates the load from a parasitic capacitance of the current control mechanism. An electric power conversion device for regulating the voltage level at the load comprises the current control mechanism that is coupled to an electric power source and configured to generate a current through the first inductor and the second inductor that are coupled in series and the voltage control mechanism that is coupled to the second inductor and configured to provide a portion of the current to regulate the voltage level.

Abstract: This regulated power supply system with high input voltage dynamics, of the type having a shared inductance buck/boost transformer and having at least two controllable semiconductor switching members, one associated with the buck function of the transformer and the other with the boost function of the transformer, is characterized in that one of the controllable semiconductor switching members is driven by control means as a function of the system's input voltage, and the other is driven continuously by enslavement means on the output voltage.

Abstract: A system for regulating the output of a high-voltage, high-power DC supply, the system includes a high-voltage DC power supply, a storage capacitor, and at least one non-dissipative regulator having an output voltage range less than an output voltage range of the high-voltage DC power supply. The regulator includes an internal storage capacitance and a control circuit configured to maintain a desired high-voltage output on a load.

Abstract: A novel switching hysteretic power converter is presented. The power converter combines the function of a capacitive charge pump with the function of an inductive step down converter to obtain a switching boost converter with a much simpler control method with respect to conventional inductive boost power converters. The hysteretic control provides stable operation in all conditions with excellent load transient response. Furthermore the hysteretic control allows high frequency switching reducing the size and cost of the passive components. The Discontinuous Conduction Mode of operation provides very high efficiency even at light loads. The presented power converter can be operated as a boost converter or as a buck converter simply by changing the switching phase of one switch. In both types of operation the efficiency of the hysteretic power converter can be quite high even at high switching frequencies.

Abstract: An object of the present invention is to provide a DC/DC power conversion apparatus that can reduce the average power consumption over a wide range of DC voltage ratios. A control circuit (120) changes a switching frequency f at which IGBTs S1 to S4 perform ON/OFF operation, in accordance with a voltage ratio k (k=V2/V1) for DC voltage conversion, based on the following expressions, such that a magnitude ?I of a current ripple flowing in a reactor Lc is a predetermined constant value irrespective of the voltage ratio k.

Abstract: A DC-to-DC, buck-boost voltage converter includes a duty cycle controller configured to generate control signals for a buck driver configured to drive first and second buck switching transistors at a buck duty cycle and to generate control signals for a boost driver configured to drive first and second boost switching transistors at a boost duty cycle. The duty cycle controller includes at least a duty cycle timer and an offset timer where the duty cycle controller applies the duty cycle timer and the offset timer to control transitions between the buck, the buck-boost and the boost operation modes of the voltage converter.

Abstract: A digital average-input current-mode control loop for a DC/DC power converter. The power converter may be, for example, a buck converter, boost converter, or cascaded buck-boost converter. The purpose of the proposed control loop is to set the average converter input current to the requested current. Controlling the average input current can be relevant for various applications such as power factor correction (PFC), photovoltaic converters, and more. The method is based on predicting the inductor current based on measuring the input voltage, the output voltage, and the inductor current. A fast cycle-by-cycle control loop may be implemented. The conversion method is described for three different modes. For each mode a different control loop is used to control the average input current, and the control loop for each of the different modes is described. Finally, the algorithm for switching between the modes is disclosed.

Abstract: The present solution relates operation of a power conversion device (200, 500). A first gate (205, 505) is operated (901) to provide a voltage pulse (309,609) travelling from an input (201,501) to a wave propagation medium (105) through the first gate (205,505). The voltage pulse has duration (307,607) less than the propagation time through the medium (105) to one end of the medium (105) and back to the input (201,501). The pulse generates a reflected wave. The first gate (205,505) is operated (902) periodically providing a voltage pulse in synchronization with the reflected wave to accumulate the reflected wave travelling in the medium (105), performing the accumulation through an accumulation interval (303,603). A second gate (207,507) is operated (903) periodically to provide a discharge pulse (312,612) in synchronization with the reflected wave to discharge the wave travelling in the medium (105), performing the discharge through a discharge interval (310,610).

Abstract: A power supply device includes: a first serial circuit coupled between a first output terminal and a second output terminal, and including a first switching element and a first rectification element; a second serial circuit coupled between the first output terminal and the second output terminal, and including a second switching element and a second rectification element; a third switching element inserted between a connection point between a first inductor and a first input terminal, and a second output terminal; a fourth switching element inserted between a connection point between a second inductor and a second input terminal, and the second output terminal; a control circuit configured to control the first and second switching elements; and a synchronous rectification control circuit configured to control the third and fourth switching elements.

Abstract: A power converter is disclosed including a switching converter having a switching node, a first quasi-resonant multiplier stage having a resonant input coupled to the switching node, and a second quasi-resonant multiplier stage having a resonant input coupled to the switching node. In another embodiment, a power converter includes a switching converter having a switching node, a first quasi-resonant multiplier stage having a boost input coupled to the switching node, and a first clamp coupled to the first multiplier stage.

Abstract: There is provided a DC-DC converter circuit with which conduction loss between switching elements is lower than in the conventional art, which affords an increase in power conversion efficiency. A DC-DC converter circuit includes a first switching element including a first semiconductor switch and a first diode, a second switching element including a second semiconductor switch and a second diode, an inductor connected between the cathodes of the first and second diodes, and a third switching element and a fourth switching element provided so as to face in mutually opposite directions on the anode sides of the first and second diodes, wherein a first voltage supply is connected between the cathode side of the first diode and the anode side of the second diode, and a second voltage supply is connected between the anode side of the first diode and the cathode side of the second diode.

Abstract: Embodiments for at methods, apparatus and systems for operating a voltage regulator are disclosed. One method includes generating, by a switching controller, a switching voltage through controlled closing and opening of a series switch element and a shunt switch element. Further, the method includes generating, by a switchable output filter, a regulated output voltage by filtering the switching voltage, wherein the switchable output filter comprises a plurality of capacitors that are selectively included within the switchable output filter.

Abstract: Circuits and methods relating to the provision of a reactive current to ensure zero voltage switching in a boost power factor correction converter. A simple passive circuit using a series connected inductor and capacitor are coupled between two phases of an interleaved boost PFC converter. The passive circuit takes advantage of the 180° phase-shift between the two phases to provide reactive current for zero voltage switching. A control system for adjusting and controlling the reactive current to ensure ZVS for different loads and line voltages is also provided.

Abstract: An energy savings device, system, and method wherein a predetermined amount of voltage below a nominal line voltage and/or below a nominal appliance voltage is saved, thereby conserving energy. Phase input connections are provided for inputting analog signals into the device and system. A volts zero crossing point detector determines the zero volts crossing point of the signal. The positive half cycle and negative half cycle of the signal are identified and routed to a digital signal processor for processing the signal. The signal is reduced by pulse width modulation and the reduced amount of energy is outputted, thereby yielding an energy savings for an end user.

Abstract: A SEPIC converter with over-voltage protection includes a high-side inductor that connects a node Vw to a node Vx. The node Vx is connected, in turn to ground by a power MOSFET. The node Vx is also connected to a node Vy by a first capacitor. The node Vy is connected to ground by a low-side inductor. A rectifier diode further connects the node Vy and a node Vout and an output capacitor is connected between the node Vout and ground. A PWM control circuit is connected to drive the power MOSFET. An over-voltage protection MOSFET connects an input supply to the PWM control circuit and the node Vw. A comparator monitors the voltage of the input supply. If that voltage exceeds a predetermined value Vref the comparator output causes the over-voltage protection MOSFET to disconnect the node Vw and the PWM control circuit from the input supply.

Abstract: A direct current (DC)-to-DC conversion apparatus is provided. The provided DC-to-DC conversion apparatus is composed of two boost circuits, in which inputs of both boost circuits are connected in parallel, and outputs of both boost circuits are connected in series. Accordingly, when the provided DC-to-DC conversion apparatus is operated, the DC input power would be firstly sampled and determined, and then the operations of the first and the second switch devices disposed therein would be controlled in response to the sampled-determined result, such that both boost circuits would be respectively operated in different input conditions, for example, the input is normally-connected or the input is reverse-connected. Accordingly, regardless of the input of normal connection or the input of reverse connection, the provided DC-to-DC conversion apparatus can perform the function of DC-to-DC conversion, thereby enabling the applied product to be normally operated even the input is reverse-connected.

Abstract: Provided is a power supply switching circuit capable of suppressing a load fluctuation such as undershoot that occurs at an output terminal at the time of power supply switching. The power supply switching circuit includes: a battery connected to the output terminal; a replica current generation circuit for generating a replica current that is proportional to a current flowing from the battery to the output terminal; a voltage regulator connected to the output terminal, the voltage regulator including a reference voltage circuit, an error amplifier circuit, an output transistor, and a voltage divider circuit; and a current mirror circuit for causing the replica current to flow through the output transistor of the voltage regulator.

Abstract: A voltage balancing circuit includes (n?1)-number of voltage stabilization circuits configured between k-th reference nodes of n-number of groups of resistances and k-th output nodes of the n-number of groups of main circuit capacitors respectively where 2?k?n. The k-th voltage stabilization circuit is configured in such a manner that the first transistor is connected via a first resistance to a (k?a)-th output node serving as the source node and the second transistor is connected via a second resistance further connected to a (k+b)-th output node serving as the destination node, where 2?k?n, 1?a?k?1 and 1?b?n+1?k.

Abstract: The step-up DC/DC converter (30) of the present invention has a synchronous rectifier transistor (M1); an output transistor (M2); a first back-gate control transistor (M3) connected between an external terminal (T2) and a back gate of the synchronous rectifier transistor (M1); a discharge transistor (M6) connected between the external terminal (T2) and a ground terminal; and a control unit (X1) for controlling the on/off state of the components described above. The control unit (X1) switches off the first back-gate control transistor (M3) and switches on the discharge transistor (M6) when stopping the switching operation of the output transistor (M2) and the synchronous rectifier transistor (M1).

Abstract: The present invention provides a DC-DC converter including: a first series circuit which is connected to the two ends of a direct-current power source Vi, and in which a first switching element Q1 and a second switching element Q2 are connected together in series; a control circuit 10 configured to alternately turn on and off the first switching element and the second switching element; a second series circuit which is connected to the two ends of the first switching element, and in which a first capacitor Ci, a first reactor Ls and a second reactor Ll having a larger value than the first reactor are connected together in series; and rectifying/smoothing circuits (Do, Co) configured to rectify and smooth a voltage between the two ends of the second reactor, and to output a direct-current output voltage.

Abstract: A potential converter device with a first storage capacitor implemented to be supplied with energy from an energy source to acquire a first potential form at the first storage capacitor, and a second storage capacitor implemented to be supplied with energy from the first storage capacitor to acquire a second potential form at the second storage capacitor. The potential converter device further has a converter electrically connected between the first and second storage capacitors and implemented to execute an energy transmission from the first storage capacitor to the second storage capacitor if the first potential form reaches a first potential threshold value and until the first potential form reaches a second potential threshold value, wherein the first potential threshold value is greater regarding its magnitude than the second potential threshold value.

Abstract: Apparatus and associated methods involve a controllable supply adapted for controlling switch phasing and pulse width to substantially equalize power in adjacent quadrants of a sinusoidal source voltage waveform to regulate reactive power drawn from the source. In an illustrative example, the supply may, in some embodiments, deliver power to a load at a level responsive to a commanded input signal. In some examples, the power supplied to the load may be adjusted according to the command input signal to a selected value within an operating range. In some examples, the operating range may include a portion or all of 0 to 100% of rated load. Various embodiments may be adapted to supply unipolar or bipolar load excitation. In some embodiments, high power factor may be maintained over a substantial range of commanded power to the load. Certain embodiments may enhance supply efficiency by capturing and recycling inductive load energy.

Abstract: Embodiments of the invention relate generally to power management and the like, and more particularly, to an apparatus, a system, a method, and a computer-readable medium for providing power controlling functionality to generate configurable power signals and to deliver power during fault conditions. In at least some embodiments, a power control unit can generate power signals having configurable attributes as a function of a mode of operation, a fault type, and the like.

Abstract: An adjustable shunt regulator circuit has two current paths in parallel, with each current path having a bipolar transistor therein with the bases of the bipolar transistors of the two current paths connected in common. One of the current paths has a high impedance node. A MOS transistor has a gate connected to the high impedance node, and a source and a drain. A resistor divide circuit is connected in parallel to the source and drain of the MOS transistor and provides the output of the regulator circuit. The resistor divide circuit has a first resistor connected in series with a second resistor at a first node. A feedback connects the first node to the bases of the bipolar transistors connected in common of the two current paths.

Abstract: A DC/DC power conversion apparatus includes a reactor connected to a DC power supply and a DC voltage conversion section connected to the reactor. The DC voltage conversion section includes a plurality of switching devices, a charge-discharge capacitor which is charged or discharged by ON/OFF operations of the switching devices, a plurality of diodes which provide a charging route and a discharging route for the charge-discharge capacitor. The DC/DC power conversion apparatus also includes a smoothing capacitor on an output side, which is connected to the DC voltage conversion section and including a plurality of voltage division capacitors connected in series to each other, and a switching device for voltage equalization provided on a connection line provided between the negative terminal of the charge-discharge capacitor and a connection point between the voltage division capacitors.

Abstract: A supply arrangement, a supply unit and a method in which a switching element is connected in series to an operating voltage and an electrical load, wherein a supply unit supplies an electronic unit with power independently of the switching state of the switching element.

Abstract: A switched-mode converter includes a first magnetic circuit including a first inductive element, coupled to at least one second inductive element and electrically coupled in series with the second element and with a first diode between a first one of two input terminals and a first one of two output terminals; a first switch coupled in series with a third inductive element between a second terminal of the first inductive element and a second input terminal, a common node between the first switch and the third inductive element being connected to one of the output terminals by a second diode; and a circuit capable of canceling the voltage across the first switch before its turning-on.

Abstract: A switched-mode buck power converter includes a power source, a first switch, an inductor for storing energy, a diode or second switch, and control circuitry. The inductor has a first end connected to an output node of the power converter, wherein the first switch is connected between the power source and a second end of the inductor. The diode or second switch is connected, at the second end of the inductor, between the first switch and a common node of the power converter. The control circuitry is configured to (i) characterize per cycle energy demand of the power converter, (ii) characterize per cycle inductive energy of the power converter, and (iii) compare the characterized energy demand to the characterized inductive energy to control the first switch.

Abstract: Embodiments of the present invention may provide an improved apparatus and method for reducing distortion in analog circuits. A circuit in accordance with the present invention may include a main path comprising an analog circuit with an input impedance, a source impedance representing the impedance of an input network driving the analog circuit, and a cancellation path. The cancellation path may be in parallel to the main path and may generate a cancelling non-linear current to substantially cancel a non-linear current drawn to the input impedance, resulting in a decrease of non-liner current flowing through the source impedance.

Abstract: The present invention relates to a DC to DC converter system (100), which comprises converter means (110) and control means (120). The switching sequence of the first, second and third switching means (S1, S2, S3) is controlled by the control means (120) in such a manner that, during the on-time of the second switching device (S2), the first current (II) that flows through the inductive storage element (L) of the converter means (110) can be indirectly measured through the first voltage (VC1) across the capacitive storage element (C1), which is being charged with a second current (12) proportional to the input voltage (Vin) of the converter means (110) and provided by the current source (CS). Thus, the on-time of the second switching means (S2) varies inversely proportional to the input voltage (Vin).

Abstract: In a power supply with n interlaced conversion cells, a control device activates m paths out of n paths, 1?m?n, as a function of the power or of the current handled by the power supply. The cell may have a boost, buck, buck/boost, Cuk, or SEPIC topology.

Abstract: The present invention discloses a buck switching regulator including a power stage, a driver circuit and a bootstrap capacitor. The power stage includes an upper-gate switch, a first lower-gate switch and a second lower-gate switch. The first upper-gate switch is electrically connected between an input terminal and a switching node. The first lower-gate switch is connected in parallel with the second lower-gate switch, both of which are electrically connected between the switching node and a first node. The driver circuit controls the operation of the upper-gate switch and the first lower-gate switch. The bootstrap capacitor is electrically connected between a boot node and the switching node, wherein the boot node is electrically connected to a supply voltage. When a voltage across the bootstrap capacitor is smaller than a reference voltage, the second lower-gate switch is turned on to charge the bootstrap capacitor from the supply voltage.

Abstract: This document discusses, among other things, a circuit including a diode and a transistor. In certain examples, an integrated circuit can include the diode and the transistor. In some examples, an apparatus can include the diode having a first temperature coefficient, a bias resistor configured to bias the diode, and a bipolar junction transistor having a second temperature coefficient the bipolar junction transistor having a base coupled to the diode and the bias resistor, wherein the first temperature coefficient and the second temperature coefficient are configured to reduce at least a portion of a temperature drift effect of the diode and the bipolar transistor.

Abstract: A cascade-connected boost circuit is disclosed. The cascade-connected boost circuit includes a first-stage boost circuit, a second-stage boost circuit, an output terminal and a regulation filtering capacitor. The first-stage boost circuit includes an input terminal, a PWM generator, a first inductor and a first switch. The second-stage boost circuit includes a second inductor and a second switch. The PWM generator controls the first switch and the second switch to turn on or turn off simultaneously. A power supply from the input terminal respectively charges the two inductors via two paths when the two switches are turned on. The two inductors release energy when the two switches are turned off. The two switches share the voltage of the output terminal. The cascade-connected boost circuit according to the present invention solves the issues that the withstand voltage limit of a single switch and the limit of a duty cycle.

Abstract: An integrated circuit includes a DC-DC converter, which includes an inductor; a first transistor coupled to the inductor and configured to pass an inductor current to the inductor; and a second transistor forming a current mirror with the first transistor. The integrated circuit further includes an operational amplifier. The operational amplifier includes a first input node and a second input node. The first input node is configured to couple to a drain of the first transistor when the first transistor is turned on, and decoupled from the drain of the first transistor when the first transistor is turned off. The second input node is coupled to a drain of the second transistor.

Abstract: An electronic device is provided for switched DC-DC conversion of an input voltage level into an output voltage level. The electronic device is configured to control a control gate of a power switch and to prevent a charge of a capacitance of the control gate released during a switching operation from flowing to ground.

Abstract: A shunt regulator includes a control circuit, a bypass circuit and a protection circuit. The control circuit is coupled between a first node and a ground, and generates a gate control signal in response to a voltage of the first node and a reference voltage. The bypass circuit forms a first current path between the first node and the ground in response to the gate control signal. The protection circuit has an MOS transistor that is fully turned on in response to a current flowing through the bypass circuit, and forms a second current path between the first node and the ground. Therefore, the shunt regulator occupies a relatively small area in an integrated circuit.

Abstract: A stable, high-speed, high-efficiency constant voltage is provided without a complicated, large-scale, high-cost phase compensation circuit over a wide range of operating conditions. This voltage buck-boost switching regulator consists of a pair of voltage reducing transistors, a pair of voltage boosting transistors, inductance coil, output capacitor and controller. The controller has the following parts for performing PWM control of constant voltage for voltage reducing transistors and voltage boosting transistors: an output voltage feedback circuit, an inductor current sense circuit, a variable sawtooth wave signal generator, switching controllers, and a voltage boosting driver.

Abstract: In a buck-boost converter, the method compensates for the boost mode power switch having a minimum on-time when entering the buck-boost mode from the buck mode by immediately decreasing a duty cycle of the buck mode power switch upon entering the buck-boost mode. This prevents the inductor current from being higher at the end of the switching cycle than at the beginning of the cycle, so the output voltage stays regulated without the converter oscillating between the buck mode and the buck-boost mode. The duty cycle of the buck power switch is increased in the buck-boost mode as the input voltage further falls and the boost power switch duty cycle is increased. Upon transitioning into the boost mode, the duty cycle of the boost power switch is immediately reduced to compensate for the buck switching being stopped and the buck power switch having a minimum off-time.

Abstract: A power factor correction converter and a control method thereof are provided includes an interleaving control tube set, an interface to an alternating current power supply, a first inductor, a second inductor, a third inductor, a capacitor, a first bridge arm and a second bridge arm. Abridge arm includes a first switch tube and a second switch tube connected in series; The first bridge arm, the second bridge arm, and the capacitor are connected to each other in parallel; the alternating current power supply and the first inductor are connected in series, and the second inductor and the third inductor are connected in parallel, and then connected to the first inductor in series; the second inductor is connected to the first bridge arm, and the second inductor is connected to the second bridge arm; and the alternating current power supply and the first inductor are connected in series.

Abstract: A switching element having an electromechanical switch (such as an electrically conductive membrane switch, for example a graphene membrane switch) is disclosed herein. Such a switching element can be made and used in a switching power converter to reduce power loss and to maximize efficiency of the switching power converter.

Abstract: A brushless fan motor control circuit assembly consists of a high-frequency filter circuit, a rectifier circuit, a power factor enhancing circuit, a current-limit and voltage regulation circuit and a brushless fan motor driving circuit. By means of the high-frequency filter circuit to suppress high frequency noises, the power factor enhancing circuit to enhance the power factor and to save power consumption, the current-limit and voltage regulation circuit to limit the current and to achieve overload protection, the brushless fan motor control circuit assembly controls the operation of a motor of an electric accurately and safely, avoiding fan vibration.

Abstract: A control method implemented in a power converter, such as a variable speed drive, is disclosed. This control method is designed to make the power converter operate when the latter is connected to the network in single-phase mode. The power converter includes a controlled current source connected in series to its DC power supply bus. This controlled current source includes an electronic converter provided with two controlled switching arms. The switching arms are controlled by alternating a modulation phase with a saturation phase, the saturation phase being applied for a determined duration ? in order to make the power converter operate in discontinuous mode.

Abstract: A control circuit for controlling a DC-DC converter, with the converter including an inductor and associated switching circuitry, with the switching circuitry including a first transistor switch connected intermediate an input voltage terminal and a first terminal of the inductor, a second transistor switch connected intermediate the first terminal of the inductor and a circuit reference, a third transistor switch connected intermediate a second terminal of the inductor and an output voltage terminal and a fourth transistor switch connected intermediate the second terminal of the inductor and the circuit reference.

Abstract: A power supply circuit and a method for operating the power supply circuit are described. In one embodiment, a power supply circuit includes multiple power elements configured to convert an input voltage to an output voltage, a driver circuit coupled to the power elements and configured to drive the power elements, a regulator controller coupled to the power elements and configured to control the power elements for the conversion of the input voltage to the output voltage, and at least one bypass switch coupled to the power elements. The at least one bypass switch is used to bypass at least one of the power elements. Other embodiments are also described.

Abstract: The high-side switch has one end connected to the input terminal. The low-side switch has one end connected to other end of the high-side switch and other end connected to a ground terminal. The inductor has one end connected to the other end of the high-side switch and other end connected to the output terminal. The capacitor has one end connected to the other end of the inductor and other end connected to the ground terminal. The high-side switch controlling circuit generates and supplies a high-side switch controlling signal based on a target voltage of the output terminal, the output voltage of the output terminal, and a current flowing through the capacitor, to the high-side switch. The low-side switch controlling circuit generates and supplies a low-side switch controlling signal based on the high-side switch controlling signal and a current flowing through the inductor, to the low-side switch.

Abstract: For output current detection of a voltage regulator, a sensing circuit is coupled to a high-side element of the regulator and detects the current therein to generate a sensing current. A simulation circuit is coupled to the sensing circuit and generates a summed current by simulation with the sensing current. A setting resistor is coupled to the simulation circuit and receives the summed current to provide an output for feedback control of the voltage regulator.

Abstract: A step-down switching regulator includes a switching device coupled to an input terminal to which an input voltage is applied, an inductor having a first end and a second end, the first end being connected to the switching device, a smoothing unit having an output terminal and configured to smooth a voltage at the second end of the inductor and generate an output voltage at the output terminal, a rectifier configured to flow a current to the inductor when the switching device is in an OFF state, and a control circuit configured to drive the switching device so that the output voltage becomes equal to a set target voltage. The control circuit detects a difference voltage between the input voltage and the output voltage or a difference voltage between the input voltage and the set target voltage, and causes the switching device to be in an ON state when the difference voltage is lower than or equal to a predetermined voltage value.

Abstract: In a circuit apparatus for transformerless conversion of an electric direct voltage of a two-pole direct voltage source (1) connected to ground having a first voltage pole (+) and a second voltage pole (?) into an alternating voltage, hazardous capacitive leakage currents are avoided by connecting the direct voltage source (1) to ground and the DC-AC converter (400) is operated at a controlled intermediate circuit voltage, a DC-DC converter stage (300) being connected between the direct voltage source (1) and the DC-AC converter (400), said DC-DC converter stage providing at its output a +/? voltage that is symmetrical with respect to the grounding point, two series-connected capacitors (41, 42) having the same polarity and being connected to ground at their connecting point (V) and controlled are charged by two buck-boost choppers (100, 200) connected one behind the other.