177 results about "Switching frequency control" patented technology

A fly-back power converter has a current-estimating control loop that senses the primary output current in a transformer to control the secondary output. A primary-side control circuit switches primary current through the transformer on and off. A discharge time when a secondary current through an auxiliary winding of the transformer is flowing is generated by sampling a voltage divider on an auxiliary loop for a knee-point. A normalized duty cycle is calculated by multiplying the discharge time by a current that is proportional to the switching frequency and comparing to a sawtooth signal having the switching frequency. The peak of a primary-side voltage is sensed from the primary current loop and converted to a current and multiplied by the normalized duty cycle to generate an estimated current. An error amp compares the estimated current to a reference to adjust the oscillator frequency and peak current to control primary switching.

A resonant switched power converter having switching frequency controlled in response to an output voltage thereof achieves over-current protection such as at start-up or under short circuit conditions using a resonant tank circuit which provides a notch filter in addition to a band pass filter. A additional band pass filter provided in the resonant tank circuit achieves increased power transfer to a load and reduced circulating resonant currents and conduction losses. The inductances of the preferred LCLCL tank circuit or other tank circuit with two pass band filters and a notch filter may be integrated into a single electrical component.

A frequency control circuit including a controlled oscillator and an amplifier circuit is disclosed for providing a clock signal to a switched capacitor circuit which divides an input voltage to provide an output voltage. The controlled oscillator has a frequency control input receiving a frequency control signal and an output for providing the clock signal at a frequency based on the frequency control signal. The amplifier circuit has an input for receiving the output voltage and an output providing the frequency control signal based on droop of the output voltage. In one embodiment, the amplifier circuit adjusts the frequency control signal to optimize efficiency of the switched capacitor circuit over a voltage range of the output voltage, which changes based on load level.

A method and apparatus for controlling power conversion. In one embodiment, the method comprises computing a voltage ratio based on a voltage conversion in a resonant converter; comparing the voltage ratio to a threshold; and controlling, independent of switching frequency of the resonant converter, power output from the resonant converter based on whether the voltage ratio satisfies the threshold.

The invention provides a PFC (power factor correction) circuit based on a delta-sigma modulation technique and a duty ratio control method thereof. The PFC circuit comprises an input voltage ADC (analog to digital converter), a duty ratio generation circuit, an output voltage processing circuit and a digital pulse width modulation circuit in electrical connection, wherein the duty ratio generation circuit comprises a switching frequency control circuit, a Ton counting circuit and a delta-sigma modulation circuit in electrical connection; and the output voltage processing circuit comprises an output voltage ADC, a digital PI (proportional integral) compensator and a rapid dynamic response circuit in electrical connection. The delta-sigma modulation technique is utilized in the PFC circuit to realize the duty ratio control method. According to the invention, the response speed of the input voltage change can be improved, the iL waveform of the input inductive current is adjusted, the frequency spectrum of the pulse width signal is shaped, the power factor is improved and the output voltage is stabilized.

The present invention provides a power supply circuit performing constant voltage control by switching frequency control and achieving minimization of a necessary control range of the switching frequency control and implementation of a configuration ready for a wide range. A switching power supply circuit includes a switching circuit, a switching driving unit, an insulating converter transformer, a primary side series resonance circuit, a secondary side series resonance circuit, a secondary side DC output voltage production unit, a constant voltage control circuit, and a composite coupling coefficient setting mechanism.

The invention discloses a current ripple real-time prediction model-based three-level voltage source variable switching frequency control method. According to the control method, a current ripple real-time prediction module and a switching cycle updating module are established; and with a current ripple peak value adopted as a control object, the switching cycle of an inverter is updated in real time through using a current ripple real-time prediction model. With the three-level voltage source variable switching frequency control method adopted, the switching frequency of the inverter changes in real time, and therefore, compared with a traditional constant switching frequency PWM control algorithm, the control method of the invention can significantly decrease average switching frequency and greatly reduce the switching loss of the inverter; and since the switching frequency change range of the inverter is wide, spectrum distribution is broader, and a harmonic current peak value can be effectively reduced, and conducted EMI (electro-magnetic interference) can be effectively improved.

The invention belongs to the field of converter control, and relates to a simplified model forecasting control method of a network voltage unbalance three-level rectifier. The simplified model forecasting control method of the network voltage unbalance three-level rectifier comprises the steps that (1) positive and negative sequence separation is carried out on three-phase network voltage and current to obtain positive and negative sequence components; (2) coordinate transformation is carried out on three-phase positive sequence voltage and current to obtain positive sequence voltage and current under a two-phase static coordinate system; (3) according to the three-phase positive sequence voltage, three levels are changed into two levels in an order reduction mode through reference voltage; (4) an active power reference value and a current reference value are calculated; (5) a current forecasting value of the rectifier, a direct current side capacitance voltage forecasting value and the changing number of switching elements are calculated; (6) current control, neutral-point potential control and switching frequency control are forecast according to a model, and the best switching state is selected. The simplified model forecasting control method of the network voltage unbalance three-level rectifier can effectively suppress double-frequency fluctuation of input power of the rectifier, lower the switching frequency of the elements, shorten circulation calculation time, control neutral-point potential balance, and improve the operation efficiency of the system.

A dimmable LED driver circuit comprises a resonant DC-DC converter coupled to an output circuit. The converter comprises a half bridge or full bridge switching circuit coupled to a resonant circuit. An output of the resonant circuit is rectified and fed to the output circuit. The output circuit may comprise at least one LED series or shunt switch for switching an LED unit on and off. A control circuit controls the switches of the switching circuit at a variable switching frequency. The control circuit is also configured for controlling the switching circuit for amplitude modulating the converter and for pulse-width modulating the converter at a first pulse-width modulation frequency lower than the switching frequency. The control circuit is may further be configured for controlling the switching of the LED switch at a second pulse-width modulation frequency lower than the switching frequency.

A method for controlling voltage crossing a power switch of a switched-mode power converter is disclosed. The method comprises the steps of: controlling a switch frequency of a power switch of a switched-mode power converter to a first frequency as activating the switched-mode power converter; and changing the switch frequency of the power switch to a second frequency after a specific amount of time; wherein the first frequency is lower than the second frequency.

A power control unit for a high-frequency dielectric heating not affected by variations in the magnetron type or characteristic, and power supply voltage fluctuation, etc., is provided. The power control unit for a high-frequency dielectric heating has an input current detection section 71, 72 for detecting input current of an inverter 10 for rectifying 31 an AC power supply voltage 20, performing high-frequency switching of the voltage, and converting the voltage to high-frequency power. The power control unit for a high-frequency dielectric heating converts a switching frequency control signal 92 provided by mixing input current waveform information 90 and power control information 91 into a drive signal of a semiconductor switching element 3, 4 of the inverter.

A wide-range compatible voltage resonant converter provides high efficiency and allows use of low-breakdown-voltage products for a circuit. The voltage resonant converter is provided with a secondary-side parallel resonant circuit and a secondary-side series resonant circuit, and a loose coupling state is established in which the coupling coefficient of an isolation converter transformer is about 0.7 or less. Thus, a constant-voltage control characteristic is obtained as a sharp unimodal characteristic, which narrows the switching frequency control region required for stabilization of an output voltage. In addition, a primary-side parallel resonant frequency, a secondary-side parallel resonant frequency and a secondary-side series resonant frequency are set so that a favorable power conversion efficiency is obtained. Moreover, an active clamp circuit is provided to suppress the peak level of a resonant voltage pulse to thereby allow use of low-breakdown-voltage products for a switching element and so on.

A converter arrangement (C.5, C.7, C.8, C.9, C.11, C.12) with at least two single LLC converters (L), a pulse generator (2) per single LLC converter (L) wherein each pulse generator (2) is configured to supply switching pulses to one single LLC converter (L) and an output controller (11) configured to use switching frequency control and/or phase-shift control to control the pulse generators (2) comprises a load balancing control (7.5, 7.7, 7.8, 7.9, 7.11, 7.12) for overcoming unbalanced loading of the converter arrangement (C.5, C.7, C.8, C.9, C.11, C.12).

The invention discloses a resonant converting device. A feedforward circuit is added into the device. The feedforward comprises a voltage sampling module and a voltage-current conversion module. The voltage sampling module samples a ripple of an input voltage of a resonant converter and provides a sampled value for the voltage-current conversion module, which converts the sampled value into a current signal. The ripple of the input voltage of the device is sampled and converted into the current signal representing a control signal for controlling switch frequency, and the current signal is fed forward to a switch frequency controller for controlling the direction of change of an output gain to be opposite to the direction of fluctuation of the input voltage, so that the device can filter the ripple, an output voltage is not affected by the ripple of the input voltage, and the ripple is relatively small.

The invention discloses a current-limiting method and a current-limiting circuit of an LLC resonant converter. According to the current-limiting method, the controlled quantity of switching frequency output in a PI adjusting step is detected so as to judge whether a frequency modulation step is added for current-limiting operation. The provided current-limiting circuit comprises a comparing trigger circuit and a current injection circuit. The current-limiting circuit can correspondingly adjust the switching frequency of the LLC resonant converter under the working condition of abruptly adding resistance-capacitance load, thus limiting the current shock of a resonant circuit, protecting the power element of the resonant circuit and solving the false triggering problem of overcurrent protection. According to the current-limiting method and the current-limiting circuit for frequency modulation, the structure is simple, the cost is low, the response speed of frequency modulation is high under the condition of abruptly adding resistance-capacitance load, and the current of the resonant circuit can be limited in an expected current set value.

The invention discloses a panoramic photographing system on an automobile. The panoramic photographing system comprises a high-speed camera, a camera support, a camera electronic switch, an automobile speed synchronous controller, a motor, a motor controller and an image processing module. The high-speed camera can take a preset quantity of pictures within a preset angle range by the aid of the camera electronic switch. The automobile speed synchronous controller is used for regulating power outputted by the motor controller according to a current automobile speed. The high-speed camera takes the pictures and then is closed according to a preset switch frequency under the control of the camera electronic switch, and the switch frequency is relevant to the rotation speed of the motor. The image processing module digitally combines the preset quantity of pictures within the preset angle range into panoramic pictures, and the panoramic pictures are stored in a memory.

The invention is applied to the field of direct current (DC) conversion, and provides a DC-DC converter. The DC-DC converter comprising a triangular wave generation module and a switch control module is adopted, the triangular wave generation module generates a triangular wave signal according to voltage across an energy storage inductor L1, and the switch control module outputs a control level according to a clock signal generated in the switch control module and the triangular wave signal to control a PMOS (P-channel Metal Oxide Semiconductor) power tube and an NMOS (N-channel Metal Oxide Semiconductor) power tube to perform switching operation according to the preset switching frequency, so that fixed switching frequency control on the PMOS power tube and the NMOS power tube is achieved; a circuit structure of the DC-DC converter is simplified on the premise that voltage conversion is performed on DC; the noise immunity is raised; a packaging area occupied by the DC-DC converter in a chip integration design process is reduced; and the cost of a chip is further lowered.

An external cavity semiconductor laser light source which comprises: an external cavity semiconductor laser light source unit; an optical filter for selecting an output beam of the external cavity semiconductor laser light source unit in a single mode; a drive unit for varying a wavelength of a transmitted light or a wavelength of a reflected light, from the optical filter; a wavelength control unit for controlling the drive unit; an optical frequency reference light source for generating a light having a reference optical frequency; an optical frequency/voltage conversion unit for generating a signal which corresponds to a difference in optical frequency between the light outputted from the optical frequency reference light source and the output beam of the external cavity semiconductor laser light source unit; a low pass filter for transmitting a low-frequency component of the signal of the optical frequency/voltage conversion unit; a switch for feeding the signal into the external cavity semiconductor light source and for interrupting the signal; and a frequency control unit for switching on and off the switch to control the drive unit.