Showing papers on "Pulse-frequency modulation published in 2011"

Analysis of THD and output voltage performance for cascaded multilevel inverter using carrier pulse width modulation techniques

Abstract: Multilevel inverter is used in applications that need high voltage and high current. The topologies of multilevel inverter have several advantages such as lower total harmonic distortion (THD), lower electro magnetic interference (EMI) generation, high output voltage. The main feature of multilevel inverter is the ability to reduce the voltage stress on each power device due to the utilisation of multilevel on the DC bus. The advent of multilevel inverter topologies has caused variety of pulse width modulation strategies. In this paper, various carrier pulse width modulation techniques are proposed, which can minimise the total harmonic distortion and enhances the output voltages from five level inverter. Three methodologies adopting the constant switching frequency (CSF), variable switching frequency (VSF), and phase shifted pulse width modulation (PSPWM) concepts are proposed in this paper. The above methodologies divided into two techniques like subharmonic pulse width modulation which minimises total harmonic distortion and switching frequency optimal pulse width modulation which enhances the output voltages. Field programmable gate array (FPGA) has been chosen to implement the pulse width modulation due its fast proto typing, simple hardware and software design. The simulation and experimental results are presented.

Analog-to-digital converter comprising dual oscillators for linearity compensation

Abstract: An analog-to-digital converter (ADC) is disclosed operable to convert a sensor signal to a digital value. A differential amplifier responsive to the sensor signal and a reference signal generates a first analog signal representing a first offset above the reference signal and a second analog signal representing a second offset below the reference signal. A first oscillator generates a first output frequency dependent on the first analog signal, and a second oscillator generates a second output frequency dependent on the second analog signal. A difference between the first output frequency and the second output frequency is generated, and the digital value representing the sensor signal is generated in response to the difference.

20 $\mu$ A to 100 mA DC–DC Converter With 2.8-4.2 V Battery Supply for Portable Applications in 45 nm CMOS

Abstract: A DC-DC buck converter capable of handling loads from 20 μA to 100 mA and operating off a 2.8-4.2 V battery is implemented in a 45 nm CMOS process. In order to handle high battery voltages in this deeply scaled technology, multiple transistors are stacked in the power train. Switched-Capacitor DC-DC converters are used for internal rail generation for stacking and supplies for control circuits. An I-C DAC pulse width modulator with sleep mode control is proposed which is both area and power-efficient as compared with previously published pulse width modulator schemes. Both pulse frequency modulation (PFM) and pulse width modulation (PWM) modes of control are employed for the wide load range. The converter achieves a peak efficiency of 75% at 20 μA, 87.4% at 12 mA in PFM, and 87.2% at 53 mA in PWM.

The Integral Pulse Frequency Modulation Model With Time-Varying Threshold: Application to Heart Rate Variability Analysis During Exercise Stress Testing

Abstract: In this paper, an approach for heart rate variability analysis during exercise stress testing is proposed based on the integral pulse frequency modulation (IPFM) model, where a time-varying threshold is included to account for the nonstationary mean heart rate. The proposed technique allows the estimation of the autonomic nervous system (ANS) modulating signal using the methods derived for the IPFM model with constant threshold plus a correction, which is shown to be needed to take into account the time-varying mean heart rate. On simulations, this technique allows the estimation of the ANS modulation on the heart from the beat occurrence time series with lower errors than the IPFM model with constant threshold (1.1% ± 1.3% versus 15.0% ± 14.9%). On an exercise stress testing database, the ANS modulation estimated by the proposed technique is closer to physiology than that obtained from the IPFM model with constant threshold, which tends to overestimate the ANS modulation during the recovery and underestimate it during the initial rest.

Radar level gauging using frequency modulated pulsed wave

Abstract: A method for measurement of a distance to a surface of a product kept in a tank method comprises transmitting a pulse train of distinct carrier wave pulses having a duration greater than 1 microsecond and shorter than 100 milliseconds, the pulse train has an average duty cycle of less than 50 percent, each pulse has a defined center frequency, selected according to a frequency scheme within a predetermined frequency range, greater than 5% of an average center frequency. The method further comprises correlating actual phase properties of received pulses with expected phase properties to provide an updated estimation of the distance. The present invention is based on transmitting a set of carrier wave pulses, each having a distinct frequency selected within a frequency range. The method is therefore referred to as a Frequency Modulated Pulsed Wave (FMPW).

An Improved Full-Bridge Dual-Output DC–DC Converter Based on the Extended Complementary Pulsewidth Modulation Concept

Abstract: This paper extends the original complementary pulsewidth modulation concept and proposes an improved dual-output dc-dc converter, in which one output branch gets the pulsewidths and is regulated by the duty cycle, while the other output branch gets the complementary pulsewidths and is regulated by the pulse-frequency modulation. The improved converter preserves all the advantages of its original version: both outputs can be fully regulated without additional switches, and all the primary-side switches can achieve the full-range zero-voltage switching. Besides, the improved converter overcomes the disadvantages of the original one: the resonant tank is moved to the primary side; the leakage and magnetizing inductances of the transformers are utilized as parts of the circuit parameters; the bulky output inductor and dissipative snubber are eliminated; both rectifiers can be clamped at the low output voltage; and they can work in the full-range zero-current switching. With these improvements, the cost and size of the proposed converter are significantly reduced, and the overall efficiency is increased. The derivation, operational principle, and circuit analysis of the proposed converter are presented in this paper, and they are verified by a prototype with 300-330 V input, and 24-V/10-A and 48-V/5-A outputs.

A Multimode Digitally Controlled Boost Converter With PID Autotuning and Constant Frequency/Constant Off-Time Hybrid PWM Control

Abstract: This paper proposes a multimode digitally controlled boost converter with PID autotuning and constant frequency/constant off-time hybrid pulsewidth modulation (PWM) control. Constant off-time PWM control is introduced in this converter for avoiding the limit cycle oscillation and maintaining a constant dc gain of the control-output transfer function for a high conversion ratio. Discrete-time modeling of constant off-time PWM is given and verified. An autotuning PID compensator based on frequency-response measurement is adopted to compensate the output stage with variable gain and variable corner frequency. PFM is also included in this controller to improve light load efficiency. A new method of automatic PWM/PFM mode switching without current sensing is proposed. Sufficient loop stability margin and optimal efficiency are obtained by using these techniques for a boost converter operating over wide ranges of output voltages, load currents, and external components. Experimental results are shown for an asynchronous boost converter with 2.5-V input voltage, 3-12 V, and 1-400 mA output.

The Variable-Bandwidth Hysteresis-Modulation Sliding-Mode Control for the PWM–PFM Converters

Abstract: This paper proposes the sliding-mode (SM) control method for the pulsewidth modulation -pulse frequency modulation (PWM-PFM) converters, in which both the duty cycle and the switching frequency are utilized as control parameters. Being different from the conventional PWM-PFM modulator, the proposed method utilizes a direct hysteresis modulation (HM) SM controller to perform the PWM, and, meanwhile, employs a quasi-indirect SM controller to control the bandwidth of the HM, so as to realize the PFM. With the proposed method, the control circuit is of low cost and is simple but the transient and steady responses are still satisfactory. The design, simplification, and implementation of the proposed SM control method are illustrated by using a typical single-switch-double-buck converter in this paper. The experimental results agree well with the analysis and show the validity of the proposed method.

Switching Regulator with Increased Light Load Efficiency

Abstract: A switching regulator includes a multiphase converter which includes a plurality of main phases configured to covert a power supply voltage to a lower voltage for application to an electronic device at different load conditions. The switching regulator also includes an auxiliary phase configured to operate in a pulse frequency modulation mode during a light load condition so that power is supplied to the electronic device by at least the auxiliary phase during the light load condition.

Power supply circuitry and adaptive transient control

Abstract: A control circuitry can be configured to receive an error signal indicating a difference between an output voltage of the power supply and a desired setpoint for the output voltage. According to one configuration, depending on the error signal, the control circuitry initiates switching between operating the control circuitry in a pulse width modulation mode and operating the control circuitry in a pulse frequency modulation mode to produce an output voltage. Operation of the control circuitry in the pulse frequency modulation mode during a transient condition, such as when a dynamic load instantaneously requires a different amount of current, enables the power supply to satisfy current consumption by the dynamic load. Subsequent to the transient condition, the control circuitry switches back to operation in the pulse width modulation mode.

A fast-transient quasi-V 2 switching buck regulator using AOT control

Abstract: A switching regulator with quasi-V2 adaptive on-time (AOT) control, that provides a fast load transient response is proposed. A feed-forward path network allows the proposed switching regulator to achieve a fast transient response and stable operation without requiring an output capacitor with a large equivalent series resistance. The proposed AOT controller makes the switching frequency pseudo fixed in continuous conduction mode and works in pulse-frequency modulation mode under ultra-light load conditions. The AOT controller adjusts the on-time according to the supply voltage load current conditions. The measurement results verify that the switching regulator can operate under load currents of 5–800 mA for supply voltages of 3.3–4.2 V and an output voltage of 1.2 V. The recovery time is 3.6μs and the voltage drop is 55 mV when the load current is increased from 5 to 750 mA.

Modulation of Individual and Mutually Synchronized Nanocontact-Based Spin Torque Oscillators

Abstract: We study current modulation of spin torque oscillators (STOs) based on single and double nano-contacts. For single nano-contact devices, we show modulation for a carrier frequency of 19-40 GHz and modulation frequencies from 50 MHz to 1 GHz. We show that the behavior of modulation and the asymmetry in the power of the modulation sidebands can be very well modeled, and predicted, using nonlinear frequency and amplitude modulation (NFAM) calculations based on the free-running STO parameters. Modulation of synchronized double nano-contact STOs is equally well modeled by NFAM theory and demonstrates the feasibility of communication applications based on arrays of synchronized STOs.

Joint brightness control and data transmission for visible light communication systems based on white LEDs

Abstract: We have proposed a variable-rate multi-pulse pulse position modulation, for visible light communication system based on white LEDs, to achieve joint brightness control and data transmission. Conventionally either pulse width modulation or pulse amplitude modulation is used for brightness control and some variants of pulse position modulation are employed for data transmission. The need for using two different modulation schemes to meet the objectives make the system design complex. Our proposed approach eliminates the use of either pulse width modulation or pulse amplitude modulation and still achieves brightness control. For the proposed modulation, achievable resolution of the brightness control depends on the number of slots used for one information symbol transfer and the resulting code-rate for data transmission depends on the number of pulsed slots per symbol. Simple iterative algorithms for encoder and decoder implementation are developed. Numerical results for performance evaluation show the effectiveness of our proposed approach. We have also obtained experimental results to analyze the effect of brightness-index on symbol error rate.

Systems and methods for flyback power converters with switching frequency and peak current adjustments

Abstract: System and method for regulating a power converter. The system includes a comparator configured to receive a first signal and a second signal and generate a comparison signal based on at least information associated with the first signal and the second signal. The first signal is associated with at least an output current of a power converter. Additionally, the system includes a pulse-width-modulation generator configured to receive at least the comparison signal and generate a modulation signal based on at least information associated with the comparison signal, and a driver component configured to receive the modulation signal and output a drive signal to a switch to adjust a primary current flowing through a primary winding of the power converter. The modulation signal is associated with a modulation frequency corresponding to a modulation period.

Digital pulse-frequency modulation controller for switch-mode power supplies with frequency targeting and ultrasonic modes

Abstract: A digital pulse controller uses digital logic to send pulses to a high side and low side switches of a switch-mode power supply converter. The digital logic uses a pulse frequency mode which includes a frequency targeting mode and an ultrasonic mode. The frequency targeting mode dynamically adjusts the size of the pulses in order to achieve a switching frequency within a desired band. The ultrasonic mode is switched into when the frequency of the pulses are at or below a threshold and the time of the pulses reaches a minimum threshold.

Data transmitting and receiving apparatus and method for visible light communication

Abstract: An apparatus for transmitting data for visible light communication sets up the pulse width control step of pulse width modulation (PWM) in a unit time interval, modulates each symbol of VLC source data input into a PWM signal in accordance with the pulse width control step, generates a visible light modulation signal by controlling the turn-on time or turn-off time of a plurality of light emitting diodes (LEDs) in response to the PWM signal, and transmits the visible light modulation signal.

A 10 MHz mixed-signal CPM controlled DC-DC converter IC with novel gate swing circuit and instantaneous efficiency optimization

Abstract: This paper introduces a mixed-signal peak current-programmed mode controlled 10 MHz dc-dc converter integrated circuit (IC) for low-power applications. The IC combines segmented power transistors, gate drivers and the main functional blocks of a multi-mode controller. Based on the information about the peak transistor current, obtained from the voltage loop, the controller instantaneously changes the number of segments, gate drive voltage, or switches to pulse-frequency modulation, such that for each operating point efficiency is optimized. To obtain reliable operation at such a high switching frequency and achieve efficiency optimization novel architecture of gate swing circuit is combined with modifications of known designs of other functional blocks. Experimental verification of a 0.6 W buck converter IC, fabricated in a 0.13 µm process, demonstrate the peak efficiency of an 83%, near time-optimal dynamic response, and up to a 20% efficiency improvement due to the action of the efficiency optimization controller.

High efficiency adaptive boost converter for LED drivers

Abstract: This paper presents the design and simulation results of an 89% power efficient CMOS adaptive controlled boost (step-up) LED driver implemented in 0.25 μm BCD (Bipolar CMOS DMOS) technology. A novel adaptive minimum frequency control provides up to 32 V from a single battery (3.6 V to 5.5 V) input supply to 10 series-connected LEDs at the output. The proposed control scheme provides an accurate load current (3–50 mA) while achieving 6%–12% higher power efficiency than conventional fixed on-time schemes. The novel control circuitry is able to switch between PWM (Pulse width modulation) and PFM (Pulse frequency modulation) automatically by calculating the feedbacks from the inductor and LED's currents. This controller is functional from light to heavy loading situations which is critical in improvement of power efficiency and battery life-time for high-boost ratio applications in order as provide accurate LED current.

Methods and apparatus for dc-dc conversion using digitally controlled adaptive pulse frequency modulation

Abstract: A method and apparatus for regulating voltage comprising calculating a first PFM on time and a second PFM on time and selecting one the PFM on times according to a selection criteria. Then activating and deactivating at least one switch according to the selected PFM on time.

Apparatus and method for measuring the distance and/or intensity characteristics of objects

Abstract: An apparatus for measuring intensity and/or range characteristics of an object(s), comprising: a signal source to emit modulation signals at a frequency(s); an illuminator to illuminate the object(s) by a first modulation signal; a sensor comprising a pixel(s), wherein the sensor creates a sampled correlated signal by sampling the correlation of a backscattered signal with a second modulation signal within the pixel; and a processor to determine range/ intensity characteristics of component returns within the pixel(s) by comparing sampled correlated signals using measurements(s), wherein the measurement(s) comprise first and second modulation signals having a characteristic(s) selected from: (a) two or more different modulation frequencies, (b) a different modulation frequency(s) and an offset of the correlation waveform, and (c) another different modulation frequency(s) and one selected from: the zeroth spatial frequency of the signal returns versus range and an approximation of the zeroth spatial frequency of the signal returns versus range.

Closed loop optical modulation amplitude control

Abstract: Systems and methods are provided for a low frequency AC comparison circuit. The low frequency AC comparison circuit includes circuitry configured to receive a monitoring signal generated by an optical detector, the monitoring signal being proportional to an amount of light generated by an optical transmission device that transmits based on a data signal that is received by an optical driver. The comparison circuit is further configured to generate a modulation current control signal that is transmitted to the optical driver based on a comparison of a low frequency AC component of the monitoring signal and a correlated low frequency AC component of the data signal.

Analysis of Output Pulse Characteristics in $Q$ -Switched Yb-Doped Fiber Laser

Abstract: Characteristics of the output pulses of a high-peak-power Q-switched Yb-doped fiber laser are presented. A Q-switched fiber laser with 1.3 kW peak power and with typical pulse duration of 240 ns at 20 kHz modulation frequency was realized, variations of pulse duration, average power, peak power, and pulse energy with variation in the modulation frequency were studied. The effect of the modulation duty cycle (DC) on the Q-switched pulse characteristics was analyzed both theoretically and experimentally. It is shown that, for a particular pump power and repetition rate, the DC of modulation needs to be optimized to achieve high-peak-power single-pulse output. If the DC of modulation is long, satellite pulses of low peak power are also observed along with the main peak, when the DC is made short enough, the satellite pulses disappear and single peak pulses appear in the output. Theoretical analysis and simulation to predict the pulse build-up time, output pulse shape, and effect of modulation window time on the output pulse characteristic were carried out. Simulation results show good agreement with experimental results. This paper reported here will be useful in the development of high-peak-power Q -switched fiber lasers.

Modulating method for noninverting Buck-Boost power inverter

Abstract: The invention relates to a modulating method for a noninverting Buck-Boost power inverter. With the modulating method, the power inverter can carry out switching work among a Buck working mode, a Buck-Boost working mode and a Boost working mode according to control amount, and the power consumption in the energy conversion process can be reduced as much as possible by adopting the combination of PWM (Pulse-Width Modulation) control and PFM (Pulse Frequency Modulation) control; meanwhile, an upper pipe bootstrap capacitance charging pulse can be generated, the traditional drive integrated chip can be conveniently adopted to drive upper and lower bridge arms, cost improvement and the complexity of design can be prevented by adopting an isolating drive power supply system, and thereby the system structure is simple.

Ac-dc converter and control circuit thereof

Abstract: The invention discloses a control circuit for an AC-DC converter. The control circuit includes a power control circuit for comparing an input current sensing signal generated by sensing an input current of the AC-DC converter and a power level control input and in response thereto generating a frequency modulation control signal, in which the frequency modulation control signal is used to control the output power of the AC-DC converter and suppress harmonics of the input current, and a square wave generator connected to the power control circuit for generating a driving signal used to drive the switch circuit of the AC-DC converter according to the frequency modulation control signal, in which the frequency of the driving signal is varied with the frequency modulation control signal, thereby suppressing harmonics of the input current and regulating the switching frequency the AC-DC converter, and regulating the output power of the AC-DC converter.

Pulse width modulation communication system

Abstract: In a PWM communication system, a sensor unit transmits as reference pulses transmission signals, which exhibit duty cycles of 100% and 0%, respectively, prior to transmission of a transmission signal, which has data items compressed thereinto by a signal processing circuit. An input capture circuit of an ECU measures the duty time and the PWM cycle of the transmission signal according to a timer clock of a timer circuit. A signal processing circuit of the ECU produces a duty cycle correction factor k based on the measured duty times and PWM cycles of the reference pulses, produces receiving data based on the duty time and the PWM cycle of the transmission signal, and the duty cycle correction factor, and separates the receiving data into sensor output values of a pressure sensor and a temperature sensor.

AM-PM synchronization unit

Abstract: One embodiment of the present invention relates to a method and apparatus for performing both phase modulation (PM) and amplitude modulation (AM) downstream of a controlled oscillator (e.g., by providing a baseband signal having no phase modulation to a controlled oscillator and performing phase modulation on a high frequency RF signal output from the oscillator), wherein the amplitude modulation is synchronized with the phase modulation. In one particular embodiment, the method and apparatus synchronize modulation of AM and PM signal paths in a manner that provides a polar modulated signal having an amplitude of zero at a symbol boundary (e.g., a transition between different symbols) having a phase of zero (e.g., a phase that crosses through a zero crossing point).

Relative efficiency measurement in a pulse width modulation system

Abstract: A pulse width modulation (PWM) power conversion system has improved efficiency over a wide operating input voltage and load range. Being able to measure relative efficiency of an analog PWM system allows enhanced control while maintaining the benefits of analog control. An analog low pass filter produces an average value of the PWM pulse train, then this analog average value is converted into digital values with an analog-to-digital converter and stored so that relative efficiencies of the PWM power conversion system may be compared for various combinations of operating parameters.

Measurement of a free spectral range of a Fabry–Perot cavity using frequency modulation and null method under off-resonance conditions

Abstract: In this paper, we discuss a method to measure the free spectral range (FSR) of a Fabry–Perot cavity (FP-cavity) using frequency modulation with one electric optical modulator (EOM) and the null method. A laser beam modulated by the EOM, to which a sine wave signal is supplied from a radio frequency (RF) oscillator, is incident on the FP-cavity. The transmitted or reflected light from the FP-cavity is observed and converted to an RF signal by a high-speed photodetector, and the RF signal is synchronously demodulated with a lock-in amplifier by referring to a cosine wave signal from the oscillator. We theoretically and experimentally demonstrate that the lock-in amplifier signal for the transmitted or reflected light becomes null with a steep slope when the modulation frequency is equal to the FSR under the condition that the carrier frequency of the laser is slightly detuned from the resonance of the FP-cavity. To reduce the measurement uncertainty for the FSR, we also discuss a selection method for laser power, a modulation index and the detuning shift of the carrier frequency, respectively.

Mode-locking and Q-switching in multi-wavelength fiber ring laser using low frequency phase modulation

Abstract: We describe experimental investigation of pulsed output from a multi-wavelength fiber ring laser incorporating low frequency phase modulation with large modulation amplitude. The Erbium-doped fiber (EDF) ring laser generated more than 8 wavelength channels with the help of a phase modulator operating at 26.2 kHz and a periodic intra-cavity filter. For most cases, the laser output is pulsed in the form of mode-locking at 5.62 MHz and/or Q-switching at harmonic and sub-harmonic of the phase modulation frequency. Chaotic pulse output is also observed. The behavior of the output pulses are described as functions of pump power and phase modulation amplitude. The relative intensity noise (RIN) value of a single wavelength channel is measured to be under −100 dB/Hz (−140 dB/Hz beyond 1.5 GHz).