1049results about How to "Reduce switching frequency" patented technology

Switched-mode power supplies (SMPSs) and their control methods for radio frequency (RF) power amplifiers in battery-powered wireless transmitter devices involve a Boost-type SMPS and a Buck-type SMPS in cascade connection which are controlled so that high efficiency is maintained for various loads and transmission power levels. The Boost SMPS and the Buck SMPS can be controlled based on the mode of operation of the transmitter, such as the actual battery voltage, the needed output power, the selected frequency band, the selected RF power amplifier (PA), the selected modulation method of the transmission signal, and/or the selected PA voltage control method, such as the envelope elimination and restoration (EER) technique, the envelope tracking (ET) technique, or the power-level tracking (PT) technique.

A switching power converter detects low load conditions based on the ratio of a first peak current value for peak current switching in constant voltage regulation mode to a second peak current value for peak current switching in constant current regulation mode. The power supply load is considered to have a low load if the ratio is lower than a predetermined threshold. Once a low load condition is detected, the switching frequency of the switching power converter is reduced to a level that minimizes switching loss in the power converter. In addition, the switching power converter also adjusts the switching frequency according to the sensed input line voltage. An offset is added to the switching period to reduce the switching frequency of the switching power converter, as the input line voltage is increased.

An audio switching power amplifier having an output pulse voltage selected in conformity with an indication of the output signal amplitude provides lower electromagnetic interference (EMI) in class-D amplifier implementations, in particular, in inductor-less designs. The output pulse voltage may be selected by providing multiple switching circuits, such as half or fully bridge switches, with each switching circuit connected to a different power supply. One of the switching circuits is activated by the switching controller, while the others are disabled, providing selection of the output pulse voltage. Selection of a lower pulse voltage, when the maximum voltage is not required, reduces the generated EMI. The switching frequency of the class-D amplifier may also be controlled in conformity with the output signal amplitude, so that at higher output levels a lower switching rate is selected, reducing the generated EMI.

A controller generates a load control signal for pulse-width modulation control for changing the duty factor of switching transistors so that the ON period of the switching transistors is elongated when said controller determines based on an error detection amplification signal that the load-side output direct current has increased, and the ON period of the switching transistors is shortened when said controller determines based on the error detection amplification signal that the load-side output direct current has decreased, in the condition in which the switching frequency is kept constant. A driver selecting portion selects, according to the load-light/heavy detection signal, at least one switching transistor to be activated, from among the plurality of switching transistors, and supplying the load control signal to the thus-selected at least one switching transistor.

A control IC including a full-bridge circuit is disposed on a primary side and a secondary side. Bidirectional communication is performed between the primary side and the secondary side in a state in which they are isolated. A control signal output from the primary side or the secondary side earlier is preferentially processed. As a result, the authority to control a switching element can be freely given to a primary-side control IC or a secondary-side control IC, and any control processing can be performed with software.

The invention discloses an optimal pressure equalizing control method of a modular multilevel converter type direct current transmission system. By setting an upper limit and a lower limit on voltage, the pressure equalizing control is mainly carried out on submodules with out-of-limit capacitor voltage, and capacitor voltage sequencing for submodules with no out-of-limit capacitor voltage is processed by combing the charging/discharging conditions of bridge arm current so as to increase the probability of maintaining an original switching state for the submodules with no out-of-limit capacitor voltage when the next action is in triggering control and lower the switching frequency of devices. The introduction of the pressure equalizing control can not lower the working frequency of triggering control and the tracking speed of a converter by using submodule capacitor voltage sequencing and triggering control to work at different frequencies. The optimal pressure equalizing control method of the invention can greatly lower the switching frequency of the devices on the premise of having no obvious increment on submodule capacitor voltage fluctuation.

The invention provides a method for clustering districts which comprises the following steps of: dividing each district into a district marginal area and an inner area according to a wireless position of the district and organizing a plurality of adjacent district marginal areas into a virtual district. The invention also provides a wireless resource scheduling method based on the method for clustering districts, a movement management method, a district pilot frequency design method, a communication network and a resource scheduling system.

The invention discloses a low-orbit satellite constellation system cell switching method and device based on ephemeris information. The method comprises the steps of enabling a mobile terminal to receive the signal intensity of a service satellite; judging a switching triggering moment, then predicting a subsatellite point position of a low-orbit satellite according to a received satellite ephemeris parameter; calculating a coverage satellite set of the switching triggering moment according to the predicted subsatellite point position; and comparing a mobile terminal with a beam feature pointset of all beams of each satellite in the coverage satellite set to obtain an adjacent cell list. The mobile terminal calculates the visual time of each beam in the neighbor cell list, screens out thebeams of which the visual time is less than a beam visual time threshold, selects the beam with the maximum switching weight in the screened neighbor cell list as a target beam, and finally sends a request of switching to the target beam to a source beam. The method has the characteristics that the beam cell switching reliability is improved; the ping-pong switching probability is reduced; the number of system control signaling is reduced; and the network efficiency is improved.

The invention relates to a permanent magnet synchronous motor low inverter power consumption direct torque control method and device. The permanent magnet synchronous motor low inverter power consumption direct torque control method adopts predictive control strategies. Compared with the space-vector-modulation-based direct torque control and the common direct torque control, the permanent magnet synchronous motor low inverter power consumption direct torque control method has the advantages of enabling the integral inverter switching frequency to be the lowest, optimally using a power device and reducing the switching loss of the inverter due to the facts that predicted values of the torque and the stator flux linkage are predicated according to an interior model of a controller based on the given reference values of the torque and the stator flux linkage and a most suitable switching position for the inverter is obtained through a minimization objective function which comprises the flux linkage, the torque and the average switching frequency within the forecast time domain and enabling online computing time to be greatly reduced due to the fact that the control law is fed back through an offline computing state, maintaining good dynamic performance and robustness of the common direct torque control and maintaining the flux and the torque to be within a corresponding hysteresis range.

The invention discloses a modular multilevel converter modulation method based on double queues. The method includes: grouping submodules according to on-off status, and sequentially storing the same in an input queue or a remove queue from low voltage to high voltage; selecting number of the to-be-input or to-be-removed submodules according to bridge arm level variation, bridge arm current direction and maximum voltage deviation of the submodules, performing corresponding input and remove operations the selected submodules, and adjusting the two queues. By the method, only the on-off status of the submodules with the largest number or the smallest number in the two queues needs to be changed, switching frequency is kept low, voltage ordering is not required by all submodules, the queues can be adjusted by simple comparison, times and time of comparison required by ordering are reduced, system response speed is increased, and huge engineering application value is achieved.

The invention discloses a hybrid MMC capacitor voltage balance control method which comprises the following steps that (1) a positive input record library, a negative input record library and a removal record library are built, (2) the maximum voltage deviation value of a sub-module capacitor in a bridge arm is determined, (3) according to the maximum voltage deviation value of the sub-module capacitor in the bridge arm, repeated input operation of the sub-module of the bridge arm is analyzed through judgment logic, and the record libraries are updated, (4) according to the bridge arm level difference before a moment and after the moment, sub-module switching operation is carried out in the bridge arm through a logic judgment and control strategy, and the record libraries are updated. By means of the method, switch frequency of the sub-module is effectively lowered on the situation that capacitor voltage keeps stable, converter loss is reduced, and meanwhile the problem that system operation performance deteriorates due to sequencing problems can be reduced.

A power electronics device with an improved IGBT protection mechanism is provided. More specifically, systems and methods are provided for reducing the switching frequency of an inverter module based on the junction temperature variation of the IGBT.

The invention, which belongs to the power converter control field of the driving motor, relates to a method for controlling neutral point voltage balance of a three level converter, wherein the method is based on a voltage space vector pulse width modulation technology and is used for controlling a neutral point clamped three level inverter. The method comprises the following steps that: step one, an action time distribution factor of a redundant small vector is obtained; step two, an area where control on a neutral point potential balance can be realized by a nearest three vector (NTV) method is obtained; step three, an NTV action area in a mixed voltage space vector pulse width modulation method is obtained; step four, a switching condition of the mixed voltage space vector pulse width modulation method is designed; and step five, the mixed voltage space vector pulse width modulation method with a proportion of pm is realized. According to the invention, a redundant small vector distribution factor is employed to design a switching condition of a mixed voltage space vector pulse width modulation strategy; therefore, an essence of a space vector modulation method is embodied; themethod can be used flexibly and used variables are less, so that it is beneficial for analysis and development application.

A DC-DC converter system is provided to improve switching control operation of a battery charging DC-DC converter (3) in an overheat temperature state without necessitating complication of a control unit (4). The control unit (4) performs output voltage limitation as well as output current limitation when the temperature of the DC-DC converter (3) is in an overheat temperature state in the vicinity of its operation stop temperature. With this capability, the output current and the output voltage can be limited, and therefore overheating of a power switching device (32) of the DC-DC converter (3) can be inhibited. In an alternative embodiment the switching frequency of the power switching device (32) is limited.

The invention discloses a low-frequency PWM rectifier and compensation capacitor based wireless charging apparatus. The wireless charging apparatus comprises a rectifying circuit, a filtering voltage-stabilizing capacitor, an inversion power switch, a launching circuit resonant capacitor, a hall current sensor, a launching circuit resonant coil, a receiving circuit resonant coil, a compensation capacitor, a rectifying power switch, a resonant filtering capacitor, a resonant filtering inductor, a load resistor, a high frequency inversion driving circuit, a microprocessor, an analog-digital converter, a hall voltage sensor, a signal detection conditioning circuit and a PWM rectifier driving circuit. According to the wireless charging apparatus, the resonance of the launching circuit and the receiving circuit is realized; the direct current voltage output range of the charging apparatus can be adjusted by the compensation capacitor; meanwhile, the operating frequency and loss of the power switch device are greatly lowered; the operating frequency section of the system is expanded; and the design flexibility of the resonant coil is improved as well.