897 results about "Pulse-frequency modulation" patented technology

A dual-mode pulse frequency modulation boost converter operates in a hysteretic mode during light load currents to regulate an output voltage using a substantially fixed peak switching current and operates in a continuous mode during heavy load currents to regulate the output voltage using a variable peak switching current. The boost converter senses load power to automatically switch between the hysteretic mode and the continuous mode.

A driver circuit produces variable current output for an LED lighting system providing improved dimming capability and greater power efficiency when responding to industry standard lighting dimmers, through the use of an input voltage monitoring circuit which variably controls the current output of a switching regulator. Output current modulation methods such as analog, PWM, Pulse Frequency Modulation, or other digital modulation, and combination or hybrid methods such as that disclosed in U.S. Pat. No. 7,088,059 B2 may be employed. The current invention marries such output modulation techniques with a control method which is derived through intelligent monitoring of the input voltage waveform. The circuit and method described is adapted to higher current applications such as LED lighting systems using the latest high-power LEDs.

A switching voltage regulator achieves high efficiency by automatically switching between a pulse frequency modulation (PFM) mode and a pulse-width modulation (PWM) mode. Switching between the modes of voltage regulation is accomplished by monitoring the output voltage and the output current, wherein the regulator operates in PFM mode at small output currents and in PWM mode at moderate to large output currents. PFM mode maintains a constant output voltage by forcing the switching device to skip cycles when the output voltage exceeds its nominal value. In PWM mode, a PWM signal having a variable duty cycle controls the switching device. A constant output voltage is maintained by feedback circuitry which alters the duty cycle of the PWM signal according to fluctuations in the output voltage.

A dual-mode pulse frequency modulation boost converter operates in a hysteretic mode during light load currents to regulate an output voltage using a substantially fixed peak switching current and operates in a continuous mode during heavy load currents to regulate the output voltage using a variable peak switching current. The boost converter senses load power to automatically switch between the hysteretic mode and the continuous mode.

The invention relates to a control scheme of double-module operation of a direct current switching power supply, which is used for direct current voltage stabilization and improves the efficiency whenthe power supply is in underloading. Under heavier load, a system adopts a pulse width modulation (PWM) mode. When in underloading, the system automatically enters a pulse frequency modulation (PFM)mode, and outputs stable direct current voltage according to detected current and load voltage by corresponding logic. Under the PFM mode, equivalent switching frequency of the power supply is loweredfollowing the reduction of the load, and the switching loss is reduced, thereby improving the efficiency when in underloading. When the load is jumped, the system automatically performs the smooth transition between the PFM mode and the PWM mode and ensures the rapid dynamic response of the output voltage. Under the PWM mode, the system integrates feedforward control of the input voltage and increases the capacity of resisting the jump of the input voltage by the load voltage. The invention is suitable to power supply control of a portable media player, an intelligent mobile phone, a load point power supply and the like.

Circuits and methods of LED dimming are disclosed. Frequency modulation using controlled modulation depth generates deterministic sidebands of both the fundamental frequency and its harmonics. Various filters including low-pass, band-pass, high-pass and combinations of those are used to selectively filter the deterministic frequency components generated by the frequency modulation to achieve LED dimming.

A method for controlling a switching converter is disclosed whereby the switching converter is configured to convert an input voltage into an output voltage supplied to a load in accordance with a switching signal, The switching converter is configured to operate in a pulse width modulation mode or, alternatively, in a pulse frequency modulation mode. When operating in the pulse width modulation mode, generating, as the switching signal, a pulse width modulated (PWM) signal of a pre-defined constant switching frequency. The PWM signal has a duty cycle that is regulated such that the output voltage of the switching converter matches, at least approximately, a desired output voltage under the condition that the duty cycle being regulated such that it does not fall below a predefined minimum duty cycle. The output voltage is monitored and switched over to the pulse frequency modulation mode when the output voltage exceeds a predefined first threshold. The method further comprises, when operating in the pulse frequency modulation mode, monitoring the output voltage and generating, as the switching signal, a series of pulses of a predefined constant pulse length. A pulse is generated each time the output voltage falls to a predefined second threshold and monitoring the frequency of the switching signal and switching to the pulse width modulation mode when the frequency of the switching signal exceeds a predefined frequency threshold.

Adaptive multi-mode digital control schemes that improve the light-load efficiency (and thus the overall average efficiency) in switch-mode power converters without causing performance issues such as audible noises or excessive voltage ripples. Embodiments include a switch-mode power converter that reduces current in the power converter using a second pulse-width-modulation (PWM) mode before reaching switching frequencies that generate audible noises. As the load across the output of the power converter is reduced, the power converter transitions from a first PWM mode in high load conditions to a first pulse-frequency-modulation (PFM) mode, then to a second PWM mode, and finally to a second PFM mode. During the second PFM mode, the switching frequency is dropped to audible frequency levels. Current in the power converter, however, is reduced in the second PWM mode before transitioning to the second PFM mode. Therefore, the power converter produces less or no audible noise in light load conditions where the switching frequency drops to audible frequency levels, while achieving high efficiency across varying load conditions.

A current mode buck converter is disclosed. The buck converter operates in a pulse width modulation (PWM) mode or a pulse frequency modulation (PFM) mode. To prevent an output inductor with various probable magnitudes from varying a decision boundary between the PWM mode and the PFM mode, the buck converter adaptively adjusts a triggering condition for the pulse frequency modulation mode according to an average value of an inductor current of the output inductor or AC components of the inductor current and a slope compensation current.

A hybrid constant current control system that uses both pulse width modulation (PWM) and pulse frequency modulation (PFM) control. When transitioning from constant voltage mode to constant current mode the present invention can continue to control using PWM. Thereafter, when the voltage has dropped, the present invention smoothly transitions to PFM mode. The point of transition is based upon the switching frequency and the lowest rated voltage of operation. The system and method avoids very short (narrow) Ton times which ensures accurate constant current (CC) control with bipolar junction transistor (BJT) devices. The present invention also avoids acoustic noise because the switching frequency is maintained at a high enough level to avoid such acoustic noise even when the energy transferred through the transformer is still substantial and the output voltage is not too low. In addition the output current limit is insensitive to variation in the inductance-input voltage ratio, and is minimized against leakage inductance.

The disclosed embodiments provide an AC/DC power converter that converts an AC input voltage into a DC output voltage. This AC/DC power converter includes an input rectifier stage which rectifies an AC input voltage into a first rectified voltage. The AC/DC power converter also includes a switching resonant stage which is directly coupled to the output of the input rectifier stage. The switching resonant stage converts the rectified voltage into a first high frequency AC voltage of a first amplitude. This AC/DC power converter additionally includes a transformer which is coupled to the output of the switching resonant stage and is configured to down-convert the first high frequency AC voltage into a second high frequency AC voltage of a second amplitude. Furthermore, the AC/DC power converter includes an output rectifier stage which is coupled to the output of the transformer, wherein the output rectifier stage rectifies the second high frequency AC voltage into a DC output voltage.

A DC (direct current) converter includes a PWM (pulse width modulation) pulse generation unit outputting a PWM pulse signal whose duty ratio is controlled in accordance with an output voltage, a PFM (pulse frequency modulation) pulse generation unit outputting a PFM pulse signal whose pulse output interval is controlled in accordance with an output voltage, a selection circuit selecting and outputting any one of the PWM pulse signal and the PFM pulse signal in response to a selection signal, a drive circuit unit driving a load and generating an output voltage on the basis of a signal outputted from the selection circuit, and a switching control unit outputting the selection signal. When the selection signal is in a second state, the switching control unit detects a fact that the number of pulses of the PFM pulse signal in a measurement period increases to or above a set value of the maximum number of pulses, and switches the selection signal to a first state.

A frequency jittering control circuit for a PFM power supply includes a pulse frequency modulator to generate a frequency jittering control signal to switch a power switch to generate an output voltage. The frequency jittering control circuit jitters an input signal or an on-time or off-time of the pulse frequency modulator to jitter the switching frequency of the power switch to thereby improve EMI issue.

A resonant converter includes a square wave generator including a first switch and a second switch, and generating a first square wave corresponding to an input voltage by alternately turning on/off the first and second switches; a resonator including a first coil of a primary coil of a transformer, and generating a resonance waveform corresponding to the first square wave; and an output unit including a second coil of a secondary coil of the transformer, and outputting a voltage corresponding to a current generated in the second coil corresponding to the resonance waveform. The square wave generator includes a pulse frequency modulation controller for turning on/off the first and second switches, comparing a first voltage linearly increased while the second switch maintains the turn-on state and a second voltage corresponding to an integration value on the time of the current flowing to the second switch when the second switch is turned off, and changing on/off drive frequencies of the first and second switches according to a comparison result. Therefore, a resonant converter driven with safety is realized.

An improved valley-mode switching (VMS) scheme and circuitry for implementing the improved VMS switching scheme in a switch-mode power converter are disclosed. For a given switching cycle, a desired switch turn-on time is determined based on a pulse width modulation, pulse frequency modulation, or other suitable power converter control scheme. Also, one or more times corresponding to local minimums (valleys) are predicted for the voltage across a power switch of the switching power converter. The power switch is turned on at a valley immediately subsequent or otherwise subsequent to the desired switch time determined according to the power converter control scheme. Thus, the improved VMS scheme enables low-voltage switch operation to reduce switching loss and EMI noise without restricting the control scheme of the power converter.

A synchronous DC-to-DC converter includes an inductor coupled to receive an input voltage, a first transistor having a source coupled to a first reference voltage and a drain coupled to the inductor, and a second transistor having a source coupled to an output conductor to produce an output voltage and a drain coupled to the inductor. A feedback signal representative of a value of the output voltage is generated, and a switch control signal is produced in response to the input voltage and a second reference voltage. The second transistor is turned off in response to the switch control signal each time the inductor current has decayed to zero to prevent reverse current flow through the inductor. A regulating signal indicates whether or not the feedback voltage exceeds the second reference voltage, to regulate the output voltage in a pulse-frequency modulation mode.

The invention provides primary frequency modulation control method and system of a new energy power station. The primary frequency modulation control method includes: calculating active power output regulating variables and new active power reference values on primary frequency modulation of the new energy power station; evaluating active power output margins of power generation units in the new energy power station; calculating the active power output regulating variables of the power generation units according to the active power output margins; according to the new active power reference values and the active power output regulating variables of the power generation units, calculating the active power reference values of the power generation units, and the power generation units performing active power output according to the active power output values. Compared with the prior art, the primary frequency modulation control method and system has the advantages that both the active power output regulating variables of the new energy power station and the active power output margins of the power generation units are taken into consideration, and grid-connection frequency of the new energy power station can be regulated under the premise of safe operation of the power generation units.

Provided is an apparatus for controlling lighting brightness through PFM, the apparatus including a lighting control unit that generates a control signal for controlling the brightness of a plurality of lightings; a PFM signal generating unit that is controlled by the control signal so as to generate a plurality of PFM signals having a different frequency from each other; and a driving voltage generating unit that composes the generated PFM signals in accordance with a preset combination, thereby generating driving voltages for driving the lightings.

The invention discloses an online monitoring and performance assessing method for primary frequency modulation of a thermal generator set. The method divides grid frequency changes into invalid disturbance, valid disturbance, large frequency disturbance and small frequency disturbance, wherein the large frequency disturbance and the small frequency disturbance are contained in the valid disturbance. Specific performance indexes of response time, stabilization time, diversity factors of set rotating speed and the like of the primary frequency modulation of the set are quantitatively assessed, the contributed electric quantity and the correct operation rate of the primary frequency modulation under the small disturbance of the set and the diversity factors of the set rotating speed under the large disturbance of the set can be effectively calculated, and an assessing method for the performance of the primary frequency modulation of the set is further provided. The online monitoring and performance assessing method for the primary frequency modulation of the thermal generator set has the advantages that calculation and monitoring can be carried out on the operation performance of the primary frequency modulation of the set in a long period of time, the comprehensive index of the primary frequency modulation of the set is further calculated, an assessing method is quantified, and the performance of the primary frequency modulation of sets in a network can be comprehensively learned by province professionals.