488 results about "Active clamp" patented technology

A double-gated low power active clamp circuit for digital circuits includes a first double-gated MOSFET serially connected between an upper power supply voltage and an input terminal to be clamped, and a second double-gated MOSFET serially connected between a lower voltage power supply and the input terminal. The voltages at the gates of the first and second double-gated MOSFETs are held at constant reference voltages by a single or double reference circuits. The clamping action can be switched on or off. The double-gated active clamping network can be implemented with a single power supply voltage, or with multiple power supply voltages. The use of the back gates of the double-gated active clamping network enables additional clamping and ESD protection for smaller generations of transistors, such as, those having dimensions below 0.1 micron. The device is particularly suited for use with dynamic threshold double-gated silicon-on-insulator, FINFET, and bulk triple well technologies.

Provided is a current-source push-pull DC-DC converter using an active clamp circuit for reusing energy of leakage inductances by not only diodes on a secondary side of a transformer being zero-current switched using a series-resonant full-wave rectifier, but also the active clamp circuit on a primary side of the transformer, which provides a discharge path of the energy stored in the leakage inductances, increases power conversion efficiency even for a wide input voltage range and reduces a switch voltage stress as compared to a conventional current-source push-pull circuit by operating even for a duty ratio below 0.5 by flowing a current of an input inductor through capacitors of the active clamp circuit when both main switches are off.

The present invention discloses a forward-flyback converter with active-clamp circuit. The secondary side of the proposed converter is of center-tapped configuration to integrate a forward circuit and a flyback circuit. The flyback sub-circuit operating continuous conduction mode is employed to directly transfer the reset energy of the transformer to the output load. The forward sub-circuit operating discontinuous conduction mode can correspondingly adjust the duty ratio with the output load change. Under the heavy load condition, the mechanism of active-clamp flyback sub-circuit can provide sufficient resonant current to facilitate the parasitic capacitance of the switches to be discharged to zero. Under the light load condition, the time interval in which the resonant current turns from negative into positive is prolonged to ensure zero voltage switching function. Meanwhile, the flyback sub-circuit wherein the rectifier diode is reverse biased is inactive in order to further reduce the power losses.

The present invention is directed to an auxiliary active clamp circuit and a method of clamping a voltage of a rectifier switch associated with a power converter. The power converter includes a main active clamp circuit associated with a main power switch coupled to a primary winding of a transformer and a rectifier switch coupled to a secondary winding of the transformer. The main power switch conducts during a main conduction period of the power converter and the rectifier switch conducts during an auxiliary conduction period of the power converter. In one embodiment, the auxiliary active clamp circuit includes an auxiliary clamp capacitor, coupled across the rectifier switch, that stores a clamping voltage substantially equal to an off-state voltage of the rectifier switch. The auxiliary active clamp circuit also includes an auxiliary clamp switch, coupled in series with the auxiliary clamp capacitor, that receives a drive signal from a secondary winding and conducts during the main conduction period thereby clamping a voltage across the rectifier switch at about the clamping voltage.

The invention relates to a control method which can be applied to an active-clamp flyback miniature photovoltaic grid-connected inverter device. The active-clamp flyback miniature photovoltaic grid-connected inverter device comprises a flyback converter and a power frequency polarity conversion circuit. In the device, a current reference is used for controlling a flyback primary-side current peak value so that the device can output a half-wave sinusoidal current, and the output voltage is clamped by a grid voltage. When the instantaneous power is lower, a constant frequency current discontinuous mode in combined with a variable frequency current critical continuous mode is adopted in the flyback control method. When the flyback converter works in a variable frequency current critical discontinuous mode, an auxiliary switching tube can be conducted for a period of time when the secondary-side current of the flyback converter reaches zero, the conduction time can be accurately controlled by a digital chip, thus realizing the leakage inductance energy feedback and the soft switch of a master switching tube under the condition of wide-range output voltages and different instantaneous powers and greatly improving the efficiency under the condition of full loads.

A method for controlling an active-clamp flyback power converter is provided. The method includes comprises: generating a switching signal in response to a feedback signal for switching a low-side transistor and regulating an output of the active-clamp flyback power converter; generating an active-clamp signal after the switching signal is disabled; generating a hysteresis bias to adjust the feedback signal; and generating a pulse signal periodically to enable the switching signal. The low-side transistor is coupled to switch a transformer. The switching signal is coupled to drive the low-side transistor. The active-clamp signal is coupled to drive a high-side transistor. A pulse width of the active-clamp signal is determined by a first resistor. The high-side transistor is connected in series with a capacitor to develop an active-clamp circuit. A minimum frequency of the switching signal is determined by a second resistor during a heavy load condition.

The subject invention reveals improvement methods for circuits that use a coupled inductor wherein overshoot and ringing associated with leakage inductance of said coupled inductor is entirely eliminated by addition of non-dissipative active clamp networks that clamp each winding during each operating state of a power supply containing said coupled inductor. A further improvement applicable to zero voltage switching circuits that employ an inductor for driving a zero voltage turn on switching transition of a switch enables elimination of said inductor and preserves said zero voltage switching properties by adding leakage inductance to a coupled inductor without any adverse overshoot and ringing effects associated with said leakage inductance. The subject invention also reveals a coupled inductor with enhanced leakage inductance which can be used with said other improvements. Example circuits including zero voltage switching flyback and forward converters which require only one magnetic circuit element are revealed. Zero voltage switching tapped inductor buck and boost converters with a single magnetic circuit element are also revealed.

A photo-voltaic (PV) power generating system and a control system for PV array string-level control and PV modules serially-connected into strings of PV modules. The system includes plural parallel strings of serially-connected power-generating photovoltaic modules that form a PV array, DC / DC micro-converters that are coupled to a DC voltage buss and to the output of a corresponding photovoltaic module or to the output of a string of photovoltaic modules; a gating or central inverter; and a control system. The micro-converters are structured and arranged to include at least one of: an active clamp device, a ground fault detection device, and a fractional power converter that injects power in series or in parallel with voltage or current from the power-generating portion onto the DC buss.

The invention discloses a non-complementary flyback active clamp converter. The non-complementary flyback active clamp converter comprises a transformer, a main switching tube, a clamp switching tube, a clamp capacitor and a drive module. The drive module outputs main drive signals to the drive end of the main switching tube, and the driving signals are used for controlling the main switching tube to be alternately switched on and switched off. The drive module outputs clamp drive signals to the drive end of the clamp switching tube. The clamp drive signals and the main drive signals have the same period. Each period comprises a first pulse signal which is generated when the switching-on state of the main switching tube is converted to the switching-off state, a second pulse signal which is generated when the main switching tube is in the switching-off state, and a signal which is generated at the remaining time and used for controlling the switching-on and the switching-off of the clamp switching tube, wherein the first pulse signal and the second pulse signal are independent of each other and both used for controlling the switching-on and the switching-off of the clamp switching tube. By the adoption of the non-complementary flyback active clamp converter, it is guaranteed that a high-frequency current generated when the clamp capacitor is charged fully flows through the clamp switching tube and avoids a backward diode of the clamp switching tube.

The invention in particular relates to a flyback active-clamp, asymmetrical half-bridge switching converter control circuit and control method. According to the technical scheme of the circuit, a flyback control circuit is provided and controls an integrated control circuit controlling a switch tube and a clamping tube. The integrated control circuit comprises a driving unit of the switch tube, a driving unit of the clamping tube, and a turn-off holding driving unit. When the load is light or zero, the total of a turn-on time of the switch tube, a turn-on time of the clamping tube and a dead zone therebetween forms a single period. The time length of the single period is a fixed value. The turn-on time of the switch tube and that of the clamping tube are in a complementary relation in the single period. The time of the single period and a turn-off holding time form a total working period. Compared with the prior art, while ensuring the efficiency of a conventional circuit and the EMI advantage under a load no less than a light load, the circuit improves the light load efficiency and reduces the zero load power consumption.

A method for controlling an active-clamp flyback power converter is provided. The control method comprises: generating a first switch signal according to an output voltage and a current sensing signal, and selectively generating a second switch signal in a complementary or non-complementary control mode according to the current sensing signal and the first switch signal. The first switch signal is coupled to drive a low-side power switch for switching a transformer and the output voltage regulation of the active-clamp flyback power converter. The second switch signal is coupled to drive a high-side power switch for recycling leakage energy of the transformer and achieving a soft-switching of the low-side power switch. With the control method, the high-side power switch can adaptively switch in a complementary or non-complementary control mode depending on the output load and input voltage conditions.

The invention discloses an active clamp synchronous rectification forward converter, and belongs to the technical field of electronics. The converter comprises a direct current input power supply, an input capacitor, a main transformer T1, a synchronous rectifier circuit, a filter circuit, a voltage sampling circuit, an optical coupling feedback circuit, a PWM control circuit and an active clamp circuit; the synchronous rectifier circuit consists of a rectifier tube and a driving circuit thereof, and a freewheeling tube and a driving circuit thereof, wherein the driving voltage of the rectifying tube is generated by a secondary auxiliary winding of the main transformer, and has the same phase as that of a first switching tube of the active clamp circuit; and the driving voltage of the freewheeling tube is generated by coupling the driving voltage of a second switching tube in the active clamp circuit, so the driving voltage has the same phase as that of the second switching tube in the active clamp circuit. The synchronous rectifier circuit of the forward converter adopted the fixed driving voltage, has the dead zone time same as the active clamp circuit, and can improve the conversion efficiency and reduce the loss of the active clamp synchronous rectification forward converter.

A protection circuit for a power transistor includes a first transistor connected in parallel with the power transistor and having a control terminal connected to a first power supply voltage through a first resistive element; and a first set of diodes connected between a first terminal and a control terminal of the first transistor. In operation, the voltage at the first terminal of the first transistor is clamped to a clamp voltage and the first transistor is turned on to conduct current in a forward conduction mode when an over-voltage condition occurs at a first terminal of the power transistor.

An active clamping positive-negative excitation converter of zero voltage switch is prepared as using active clamping circuit as converter primary edge circuit, parallel-connecting switch tube to converter primary edge winding then to two ends of input voltage, parallel-connecting clamp tube to clamp capacity then to said winding, using full-bridge rectification circuit as converter secondary edge circuit, series-connecting resonant inductance in secondary edge circuit to let current of secondary edge winding flow through inductance for making current variation of secondary edge winding be current variation of inductance excitation.

This invention discloses active clamp zero-voltage soft switch high gain boost staggered parallel converters including two power switch tubes, two clamp switch tubes, two clamp capacitors, two continuing flow diodes and two coupled inductors, in which, each of the two coupled inductors includes three windings, which utilizes the second and third windings of the two coupled inductors to realize high gain output of the converter, utilizes a serial circuit composed of the two clamp switch tubes and two clamp capacitors to absorb and transfer harmlessly the leak energy of the two coupled inductors and realizes turn on of zero voltage of two power switch tubes and zero voltage turn-off of them utilizing the parallel capacitors of the two switch tubes to further realize zero-voltage turn on and off of the two clamp switch tubes.

The invention relates to the field of switching converters, and particularly relates to a flyback active clamp-type switching converter control circuit and a control method thereof. The active clamp flyback circuit of the invention can realize reduced frequency and ZVS, and comprises a main power circuit, a clamp circuit, and an output rectification filter circuit, wherein a transformer and a main switching tube are connected to form the main power circuit; a clamp switching tube and a clamp capacitor and a clamp diode are connected to form the clamp circuit; and an output rectification diode and an output capacitor are connected to form the output rectification filter circuit. In comparison with the prior art, reduced frequency in light load can be realized, and the control scheme is flexible; switching loss in no load and loss of a transformer winding and switching tube inner resistance caused by a current effective value are little, no-load power consumption is greatly reduced, and the light-load efficiency is improved.

The invention provides a soft switching conversion device based on a flyback converter. On the basis of the conventional Flyback converter power topology, a clamp branch consisting of a controllable power clamper tube and a clamp capacitor is connected to a drain end of a main power tube in series; a primary side chip of the conversion device receives information such as the peak excitation current, the valley bottom excitation current and the maximum voltage of switching nodes of a converter power loop and generates ideal drive dead time varying with an input voltage and a load condition to control the main power tube and the clamper tube, so that the voltage oscillation of the drain end of the power tube caused by leakage inductance can be completely eliminated. Owing to the basically loss-free soft switching technology of the MOS tube active clamp, the stable clamp voltage value and the primary-side and auxiliary-side full working conditions, the device can work at a high frequency(> 1MHz) and can greatly increase the power density of a power adapter when being applied to the adapter.

A power converter system is provided for supplying power to an electrical load. The power converter system includes a power converter circuit adapted to perform an AC to DC power conversion and an active clamp circuit coupled to the power converter circuit for regulating DC bus voltage overshoots. The power converter circuit is configured from a plurality of semiconductor switches having reverse voltage withstand capability.

A flyback power converter includes a hybrid clamp circuit and a corresponding power management unit that substantially optimizes the performance of the flyback power converter in its entire line and load ranges. The clamp circuit, which is connected in parallel to a primary winding of the flyback transformer, includes a parallel combination of a capacitor and resistor that is connected in series with a parallel combination of a switch and a diode. By sensing the operating conditions, the power management circuit configures the clamp circuit either as a passive clamp or as an active clamp. In the passive-clamp configuration, the switch is kept turned off. In the active-clamp configuration, the switch operates with pulse-width modulation (PWM) which enables ZVS turn-on of the main switch.

The converter includes six pieces of three phase bridge arm including full controlled main switch with diode connected in inverted parallel, input inductance connected between power source and middle point of each phase bridge arm, and output capacitance connected to output end of three phase bridge arm. Characters are that capacitance is connected to six main switches respectively. Resonant inductance is connected to DC bus of three-phase bridge arm and output capacitance. Cascaded circuit of auxiliary switch and clamping capacitance is cross-connected on two ends of resonant inductance. Two ends of the auxiliary switch are connected to diode in inverted parallel as well as connected to capacitance. Features of the converter are simple structure, restraining backward recovery of diode connected in inverted parallel, realization of soft switch and high efficiency of circuit.

Disclosed herein are a converter, a method for controlling the same, and an inverter. The converter includes: an input terminal having power input thereto; a first converter unit converting the power input to the input terminal to thereby output the converted power to an output terminal; and a second converter unit connected between the input terminal and the output terminal while being in parallel with the first converter unit, wherein each of the first and second converter units includes an active clamp unit provided at a primary side thereof and a synchronous rectifying unit provided at a secondary side thereof.

The invention provides an active clamp flyback converter self-adaptive control method and circuit, which are used for controlling a conduction time of a clamper tube. The active clamp flyback converter self-adaptive control method and circuit have the following characteristics and effects: a multiplexing auxiliary winding voltage sampling pin determines whether a main switch pipe ZVS is switched on or not, and no additional pin is needed, so that the encapsulation size is reduced; a switch node voltage proportional value in the conduction period of the main switch pipe is saved, and the conduction realization situation of ZVS is determined cycle by cycle on a rising edge of a main switch pipe driving signal, so that the self adaption can be actually realized; since the saved switch node voltage proportional value is gradually updated cycle by cycle, the determination result of the conduction realization situation of the main switch pipe ZVS is not influenced by the device precision, and the determination result is more accurate; and by virtue of the bidirectional control for the width of the clamper pipe driving signal, on the premise of realizing the conduction of the main switchpipe ZVS, the negative current flowing by a diode of the main switch pipe body can be reduced as far as possible, and the loss can be reduced.

A control circuit of a flyback power converter according to the present invention comprises a low-side transistor, an active-clamper, a high-side drive circuit, and a controller. The low-side transistor is coupled to switch a transformer. The active-clamper is coupled in parallel with the transformer. The high-side drive circuit is coupled to drive the active-damper. The controller generates a switching signal and an active-clamp signal. The switching signal is coupled to drive the low-side transistor. The switching signal is generated in accordance with a feedback signal for regulating an output voltage of the flyback power converter. The active-clamp signal is coupled to control the high-side drive circuit and the active-clamper. The active-clamp signal is generated in response to a predicted time of the transformer. The predicted time is determined in accordance with an input voltage, the output voltage and an on time of the switching signal.

A vehicle leaf spring suspension having a low spring rate is disclosed. The suspension has an axle seat secured to a vehicle axle. The leaf spring is clamped at its spring seat area to the axle seat at the clamp group mounting surface of the axle seat and with certain of the disclosed axle seats, can be clamped such that the spring seat area is asymmetrically positioned with respect to the vehicle axle centerline. Also, an active clamp group arrangement can be used to utilize the entire physical length of the leaf spring.

A control circuit of a flyback power converter according to the present invention comprises a low-side transistor, an active-damper, a high-side drive circuit, and a controller. The low-side transistor is coupled to switch a transformer. The active-damper is coupled in parallel with the transformer. The high-side drive circuit is coupled to drive the active-clamper. The controller generates a switching signal and an active-clamp signal. The switching signal is coupled to drive the low-side transistor. The switching signal is generated in accordance with a feedback signal for regulating an output of the flyback power converter. The active-clamp signal is coupled to control the high-side drive circuit and the active-damper. The active-clamp signal is generated in response to a demagnetizing time of the transformer. The pulse number of the active-clamp signal is less than the pulse number of the switching signal in a light load condition.

The invention discloses an active clamping three-level zero-voltage soft-switching converter using coupled inductor, comprising two capacitors connected in series at direct current side and a main circuit connected with the two capacitors. An auxiliary switching circuit is connected on the main circuit. The switching converter is characterized in that the main circuit comprises switching tubes T1, T2, T3 and T4 connected in series in order and diodes D1, D2, D3 and D4 connected with the switching tubes in anti-parallel, respectively; two switching tubes Tp and Tn connected in series are connected between switching tubes T1 and T2, T3 and T4 in parallel, and connected with diodes Dp and Dn in anti-parallel; and the auxiliary switching circuit comprises two resonant capacitors connected with the switching tubes T2 and T3 in parallel respectively, coupled inductors connected to output ends of the switching tubes T1 and T2 and an auxiliary switching circuit connected with output ends of main circuit diodes Dp and Dn in parallel. The switching converter has the advantages of being simple in structure and control, convenient in modular design, high in reliability, easier in application and so on.

A converter includes a transformer, a main switch, an active clamp circuit, and a control circuit. The transformer includes a primary winding and a secondary winding, and is configured to receive an input voltage and output an output voltage to a load. The main switch is coupled between the primary winding and a primary ground terminal. The active clamp circuit includes an auxiliary switch and a clamp capacitor. The auxiliary switch is coupled to the clamp capacitor in series, and the active clamp circuit is coupled in parallel to the two terminals of the primary winding or the main switch, and is configured to clamp the voltage across the main switch when it is OFF. The control circuit outputs an auxiliary switch control signal to turn on the auxiliary switch when the voltage across the main switch is at its first peak of the resonant voltage.

The invention provides a controller for a non-complementary active clamp flyback converter. The controller comprises a frequency control unit, a pulse width control unit, a sequential control unit anda driving unit, uses a multi-mode control mode, and further comprises a wave peak detecting unit and a mode a determining unit. The wave peak detecting unit detects the peaks of an oscillating voltage at the drain end of a main switching tube, and turns on a clamp tube at the troughs in the non-complementary mode of the converter. The turning off of the clamp tube is determined by internally setturn-on time. The mode determining unit, according to feedback voltage FB, gives a mode switching signal to the sequential control unit according to a mode determining result signal. By using a DCM mode, the controller prevents the clamp tube from being turned on, reduces the peak-to-peak value of the excitation current when entering a frequency hopping mode, avoids audio noise, and optimizes no-load power consumption. Since the comparison process of the mode conversion is provided with a long time delay, the influence of mode switching on a converter control loop is reduced.