Showing papers on "Pulse-frequency modulation published in 2005"

Generalized discontinuous carrier-based PWM modulation scheme for multi-phase converter-machine systems

Abstract: Using an expanded reference frame transformation expressed in the complex-variable form, the possibilities offered by multi-phase converters, using carrier-based, sine-triangle pulse-width modulation to generate voltages of different frequencies to actuate multi-phase electric machines are set forth. The generalized expressions for the modulation signals, including the neutral voltage component to be compared with the high frequency triangle waveform to synthesize reference voltages for both five and six-phase converter-electric machines are determined. How the inclusion of the neutral voltage affects the modulation signals and the voltage gain and waveform quality is discussed. Some experimental results of synthesized five phase converter voltage waveforms are provided to validate the voltage waveform synthesis using carrier-based generalized (dis)continuous pulse-width modulation for operation in both the under and over- modulation regimes.

A high-efficiency, dual-mode, dynamic, buck-boost power supply IC for portable applications

Abstract: Integrated power supplies are critical building blocks in state-of-the-art portable applications, where they efficiently and accurately transform a battery supply into various regulated voltages, as required by their loads. This paper presents a novel low voltage, dual-mode, buck-boost converter IC targeted for dynamic supplies of linear RF power amplifiers (PAs) in wireless handsets. Maintaining high efficiency of the converter over a wide loading range is critical for improving battery life in such systems. The use of a novel, supply-voltage adaptive, on time control for pulse-frequency-modulation (PFM) mode achieves an accurate output ripple voltage, not to mention higher efficiency under light loads. In the high-power mode, the converter is operated in a modified pulse-width-modulation (PWM) control, where its operation is changed adaptively between buck, buck-boost, and boost regions, thereby saving unnecessary switching losses. Appropriate circuit topologies are developed and designed to overcome the challenges of a low supply voltage environment requiring a wide dynamic range converter. The converter is designed and simulated using a 0.5-/spl mu/m n-well CMOS process for a supply voltage range of 1.4-4.2 V, which is compatible with state-of-the-art Li-ion batteries (2.7-4.2 V), and alternate power sources, e.g. NiCd and NiMH batteries. Simulation results show that the converter generates an output voltage of 0.5-5 V while delivering up to 0.5 A of load current with a maximum ripple of 40 mV. The converter exhibits efficiency of 60-93% in PWM mode and 80% in PFM mode. A 0.9-1 V transient control-step response in PWM mode, which refers to a change in output voltage of 4.5-5 V, from an input supply of 1.4 V, is less than 200 /spl mu/sec.

Pulse width modulation (PWM) rectifier with variable switching frequency

Abstract: A method for controlling a device including a plurality of switching devices operated in accordance with a pulse width modulation technique includes receiving a reference voltage signal associated with a first pair of the switching devices. A switching signal is generated. The first pair of switching devices are controlled based on the reference voltage signal and the switching signal in accordance with the pulse width modulation technique. A frequency of the switching signal is varied based on the value of the reference voltage signal.

Noise-shaping techniques applied to switched-capacitor voltage regulators

Abstract: A delta-sigma control loop for a buck-boost dc-dc converter with fractional gains is presented. This technique reduces the tones caused by the traditional pulse-frequency modulation regulation. The prototype regulator was fabricated in a 0.72-/spl mu/m CMOS process and clocked at 1 MHz. It achieved suppression of tones up to 55 dB in the 0-500-kHz range. The input voltage range was 3-5 V. The output voltage ranged from 1.8 to 4 V for load currents up to 150 mA.

Pulse frequency modulation methods and circuits

Abstract: A technique for voltage regulation involves switching between light load mode and PWM mode based on load conditions. Advantageously, this improves efficiency at light load. In an embodiment, error amplifier output is used to determine whether load is light. When light load is detected, extend PWM off time until the output voltage reaches a load threshold.

Two-point frequency modulation apparatus, wireless transmitting apparatus, and wireless receiving apparatus

Abstract: A two-point frequency modulation apparatus is provided that reduces input timing difference and improves modulation accuracy. Two-point frequency modulation apparatus 10 has: PLL circuit 11 ; frequency division ratio generator 13 that generates the frequency division ratio in frequency divider 111 based on first digital baseband signal S 1 and carrier signal; adder 114 that adds second digital baseband signal S 2 to the output signal of loop filter 113 ; a delay index calculator (filter coefficient calculator 17 ) that calculates the delay index based on the magnitude of change in the amplitude of the output signal of adder 114 ; and a delay adjuster (digital filter 18 ) that shifts the phase of one of first digital baseband signal S 1 and second digital baseband signal S 2 according to the delay index so as to reduce the phase difference.

High pass modulation of a phase locked loop

Abstract: A radio frequency modulator based on direct frequency/phase modulation of output signal of a controllable oscillator ( 724 ) that is a part of a phase locked loop (PLL) provides a direct modulator that is able to operate over a wide frequency range with a flat frequency response. A modulation signal is digitally processed ( 721, 730 ) before injection to a high-pass path of a direct modulator. Applicability of digital signal processing is based on the fact that the modulation signal is a base band signal. Therefore, the modulation signal ( 702 ) occupies such a band in the frequency domain so that a sufficient ratio of a sampling rate to an upper edge frequency of the modulation signal can be achieved. Digital processing is used for compensating an effect of non-flat high-pass PLL transfer function and/or to perform pre-distortion of the input signal of a controlled oscillator to compensate an effect of non-linearity of a controlled oscillator.

A 3-D generalized direct PWM algorithm for multilevel converters

Abstract: A three-dimensional (3-D) generalized direct pulse width modulation (PWM) algorithm is proposed for multilevel converters in a three-phase, four-wire system. It is proved to be equivalent to the newly proposed generalized 3-D space vector modulation (SVM). However, the direct PWM greatly simplifies the calculation process and is much easier to implement in digital controllers. The direct PWM can be used in all applications needing a 3-D control vector, such as active filters, uninterruptible power supplies, etc. Simulation and experimental results are given to show the validity of the proposed control strategy.

Frequency domain analysis of fiber bragg grating based phase modulation to intensity modulation conversion

Abstract: In this paper, optical phase modulation to intensity modulation by the use of a fiber Bragg grating (FBG) based frequency discriminator is proposed and experimentally demonstrated. In the proposed approach, the optical carrier frequency is placed at the quadrature point of the positive or negative slope of the reflection response of the FBG. The phase modulated light reflected from the two opposite slopes will have a π phase difference, which makes bipolar operation possible in an all-optical microwave signal processor or an optical code division multiple-access system. Both the frequency and phase responses of the FBG are taken into account to build a theoretical model in a frequency domain. Phase modulation to intensity modulation conversion based on a Gaussian apodized FBG is experimentally implemented. The results confirm the theoretical analysis.

Phase moulation apparatus, polar modulation transmission apparatus, wireless transmission apparatus and wireless communication apparatus

Abstract: A phase modulation apparatus is provided whereby excellent RF phase modulation signals can be obtained even when the modulation sensitivity of a voltage controlled oscillator varies. Phase modulation apparatus 100 has: phase detector 105 that performs phase detection with respect to an RF phase modulation signal outputted from VCO 101; comparator 106 that compares the phase of the detected signal with the phase of a baseband phase modulation signal and outputs the difference between the signals; variable gain amplifier 107 that controls the gain of the baseband phase modulation signal based on the output of comparator 106 and supplies the gain-controlled baseband phase modulation signal to VCO 101. By this means, the signal level of the baseband phase modulation signal that is supplied to VCO 101 can be controlled in accordance with the modulation sensitivity of VCO 101, so that phase modulation apparatus 100 can be realized whereby excellent RF phase modulation signals even when the modulation sensitivity of VCO 101 varies.

Bandpass pulse-width modulation (BP-PWM)

Abstract: New transmitter architectures utilizing nonlinear power amplifiers when transmitting linearly modulated signals are studied The emphasis is on bandpass pulse-width modulation (BP-PWM) for which both theory and implementation proposals are presented

Transmission device and radio communication device

Abstract: A transmission device having a preferable power efficiency and a wide control range of transmission output power. A pre-stage side of a high-frequency power amplifier changes an amplitude of a high-frequency phase modulation signal according to a base band amplitude modulation signal and a gain control signal. A variable gain amplifier changes the amplitude of the high-frequency phase modulation signal according to the base band amplitude modulation signal and the gain control signal, so that the base band amplitude modulation signal is supplied to an amplifier via a linear-log converter.

Polar modulator and a method for modulation of a signal

Abstract: A polar modulator contains a phase locked loop which is designed to emit a radio-frequency signal at one frequency to one output, with the frequency being derived from the reference signal and from a phase modulation signal at a control input of the phase locked loop. The modulator additionally has a second signal input for supplying an amplitude modulation signal. The second signal input is connected to a control input of a pulse width modulator, one of whose signal inputs is coupled to the output of the phase locked loop. The pulse width modulator is designed to vary the duty ratio of a signal which is applied to the signal input, with this variation being adjustable via a regulation signal at the control input. A filter can be connected downstream from the output of the pulse width modulator and suppresses higher harmonic components in a signal which can be tapped off at the output of the pulse width modulator. The amplitude of an output signal is thus modulated by carrying out pulse width modulation and by subsequent suppression of higher-level frequency components.

A Reduced Switching Frequency Modulation Algorithm for High Power Multilevel Inverters

Abstract: Multilevel inverters have emerged as the state of the art power conversion systems for high power medium voltage applications. Many topologies and modulation methods are commercially available. This paper presents a new adaptive duty cycle modulation algorithm, that reduces the switching frequency and consequently the switching losses. This can be important for high power applications, where high frequency modulation methods like PWM are not suitable. Results are shown for a nine level asymmetric cascaded inverter. Output voltage waveforms obtained for references with variable frequencies and amplitudes show a similar switching pattern, with a reduced and near constant number of commutations per cycle, regardless the reference frequency and amplitude. The proposed modulation is compared to a multiple carrier PWM method, achieving the same fundamental reference tracking performance with a reduced number of commutations

A novel multimode digital control approach for single-stage flyback power supplies with power factor correction and fast output voltage regulation

Abstract: This paper describes a novel digital control approach to achieve the unity power factor and fast output voltage regulation for single-stage single-switch AC-DC flyback power supplies This intelligent digital approach achieves the combined benefits of high performance, low cost and high reliability in a single controller In this solution, the power converter is constructed with the simplest and least expensive basic flyback topology that does not require a bulk capacitor to store energy on its primary-side The converter operates in various modes according to the line input voltage and the output load For power factor correction, there are two operation modes: critical discontinuous conduction mode (CDCM) and discontinuous conduction mode (DCM) Two other operation modes apply to the output voltage regulation: fast transient mode during load transient and pulse frequency modulation (PFM) mode at light load The IC incorporating these innovative solutions have been introduced by iWatt In addition to describing this approach, this paper gives the experimental results obtained on a 90W (195 V 462 A) prototype

PDM and PFM hybrid control of a series-resonant inverter for corona surface treatment

Abstract: A corona surface treatment based on a pulse density modulation (PDM) and pulse frequency modulation (PFM) hybrid control scheme is presented. The PDM scheme is used to regulate the output power of the inverter and the PFM scheme is used to compensate for temperature and other environmental influences on the discharge. Experimental results show that the PDM and PFM hybrid control series-resonant inverter (SRI) makes the corona discharge treatment simple and compact, thus leading to higher efficiency. The hybrid control SRI is able to realise constant frequency control and linear power adjustment and is thus becoming an ideal choice for corona discharge treatment.

Filling a spectral hole via self-phase modulation

Abstract: The effect of spectral amplitude modulation on self-phase modulation is studied. To that end we remove a small interval of frequency components from the broad spectrum of a femtosecond laser pulse. We investigate the regeneration of these missing frequency components via self-phase modulation. A water jet serves as a transparent sample. A physical model is given which explains the observation that the removed frequency components are not only replenished by self-phase modulation but can even overshoot their adjacent frequencies in power spectral density. In addition, we suggest possible applications in the field of nonlinear microscopy.

A method and system for analog to digital conversion using digital pulse width modulation (pwm)

Abstract: A system and method for analog-to-digital conversion (118) using digital pulse width modulation (PWM) is disclosed. The method and system according to the disclosed invention converts an analog input signal (104) to a digital signal in pulse code modulated (PCM) form (106). The disclosed invention uses a feedback circuit (114) to perform PWM of the analog input signal. The PWM signal is then decimated to obtain the digital signal in PCM form. The system according to the disclosed invention requires lower operating frequency and dissipates lesser power than prior art systems providing the same sampling frequency and resolution. The operation at a lower frequency is achieved by obtaining two samples from every pulse of the PWM signal; the first sample being obtained from the right duty ratio. Further the disclosed invention has lesser implementation complexity and higher signal-to-noise ratio than prior art.

Dsp with variable sample frequency

Abstract: An implantable medical device including a sampling scheme to obtain digital representation from analog signals is disclosed. The analog signals represent intracardiac activity. Generally, a detector detects the amplitude of the analog signals and generates first and second difference signals. The first difference signal is generated after detection of significant changes in the analog signal amplitude. The second difference signal is generated upon confirmation of the absence of significant changes in the analog signal amplitude over a predetermined period of time. A frequency selection is implemented to select the sampling frequency based on the first and second difference signal.

PLL modulation circuit and polar modulation apparatus

Abstract: First and second calibration signals ( 308, 309 ) are sent to a frequency divider ( 102 ) and an adder ( 116 ) of a PLL section ( 100 A), demodulated in a demodulator ( 111 ), filtered through a low pass filter ( 113 ) and a high pass filter ( 114 ) and thereafter sent to a modulation signal control circuit ( 115 ). The modulation signal control circuit ( 115 ) generates control information ( 318 ) in comparison with the phase and amplitude of the first and second calibration signals ( 308 and 309 ) and sends the control information ( 318 ) to a modulation control signal generator ( 106 ). Modulation control signal generator ( 106 ) holds the control information ( 318 ) and controls the values of the first modulation signal and second modulation signal sent to the frequency divider ( 102 ) and adder ( 116 ) on the based on the control information ( 318 ) held in modulation operation.

Controller and image display device

Abstract: The present invention discloses a control apparatus. This control apparatus has a modulation circuit, and a control circuit for setting up an amplitude setting signal and/or a pulse width setting signal to be used in the modulation circuit, on the basis of characteristic data representative of characteristics of an input image signal, the amplitude setting signal and/or the pulse width setting signal being used for setting up an amplitude and/or a time width of a pulse signal to be output from the modulation circuit in accordance with a gradient gradation value of the image signal, wherein the modulation circuit is a circuit which uses the time width setting signal and/or the amplitude setting signal as a reference signal for setting up the time width and amplitude of the pulse signal in correspondence with the gradient.

Optical frequency modulation and intensity modulation suppression in a master-slave semiconductor laser system with direct modulation of the master laser

Abstract: An injection-locked laser system where the master laser is directly modulated is analyzed using rate equations. Both quasi-static and dynamic analyses are carried out in order to ensure that the parameters lie inside the locking range. The analysis is valid for all injection levels. The quasi-static analysis provides a good basis for explaining the phenomena. It is shown that, for a given detuning frequency, maximum suppression of intensity modulation (IM) occurs at a specific value of the injection ratio. At low frequencies, the frequency modulation (FM) index of the slave laser bears a constant ratio to the FM index of the master laser of less than unity. It is illustrated that the direct FM scheme is only viable for modulation frequencies up to about 100 MHz. Large IM suppression can only be achieved for large values of the linewidth enhancement factor of the slave laser, small magnitude of the detuning frequency, and low injection ratio. The latter two conditions are associated with narrow limits on stable operation, and care should be taken to avoid instability.

A New Control Circuit Extends the Effective Duty Cycle Range of Flyback Converters

Abstract: Voltage source flyback converters in the discontinuous conduction mode with a new control strategy is presented in this paper, that is capable of operating over a wide range of input and output voltage variation Over the normal range, pulse width modulation at fixed frequency is used as in conventional system At low duty cycle demands, constant pulse width with variable frequency is used to extend the effective duty cycle range

DSP-based closed-loop control of bi-directional voltage mode high frequency link inverter with active clamp

Abstract: This paper presents a novel modulation and digital controller based on a bi-directional voltage mode high frequency link inverter with active clamp to achieve fast dynamic response and high static performance. The inverter consists of a full-bridge converter, a bi-directional active rectifier, an active clamp branch and a pulse width modulation (SPWM) inverter bridge. A novel modulation strategy is applied by modulating the triangle carrier wave and two inverse sinusoidal modulation waves, it is no need of checking the pole of the output voltage to switch the modulated signals, and it is able to weaken the distortion of the output waveform on zero passage. Double closed-loop digital control with load current feed-forward is applied to achieve good dynamic response. The modulation and control strategy is realized by using the TMS320LF2407A DSP and EPM7128 CPLD. Theoretical analysis and experimental results referring to a laboratory prototype (3 KVA) indicate that the proposed modulation and control scheme are promising for the applications of DC/AC power supply.

Pulse-width modulation signal generating device and method for generating pulse-width modulation signals

Abstract: Pulse-width modulation signal generating device and method for the same that can generate multiple pulse-width modulation signals with different overall lengths wherein only a small amount of data is stored in storage means and duty cycles are varied between individual unit pulse signals. Multiple settings are stored in storing means for three types of variables: initial duty cycle; duty change range; and number of unit pulse signals that form a single phase. Out of these, a selected initial duty cycle, a selected duty change range, and a selected number of unit pulse signals that form a single phase are retrieved. These selected values are used to represent the duty cycles for all unit pulse signals forming one phase. The unit pulse signals for which duty cycles have been determined are output to generate a pulse-width modulation signal.

On-chip boost DC-DC converter in color OLED driver & controller ICs for mobile application

Abstract: On-chip boost DC-DC converter used in color OLED driver and controller ICs for mobile application is presented in this paper. For special systematic requirement, current-limited pulse-frequency modulation (PFM) control scheme is used. This converter is designed with 0.35mum 1P4M high-voltage CMOS process. Experimental results show that, the converter can operate with supply voltage from 2.5 to 4.2V, which is suitable for single-cell lithium-ion rechargeable battery supply application, and boost voltage up to 12~18V for illuminating OLED display pixels. The output ripple voltage is about 250mV with 6.8muF off-chip capacitor and 10muH off-chip inductor. The power efficiency is over 75% for 1~300mA load current, maximum to 87% at about 200mA load current

Comparison of UWB auto-correlation and transmitted reference schemes

Abstract: This paper provides a theoretical comparison of different multi-pulse schemes for ultra-wideband (UWB) transmitted reference (TR) which utilizes correlation based receivers. The performance comparison is based on a simplified analysis of signal-to-noise ratio (SNR) derivations of receiver output for different signal repetition structures using binary pulse position modulation (BPPM) and binary pulse amplitude modulation (BPAM). The results shows that the best solution is based on pair-wise combination of pulses for which succeeding pulses form the reference for subsequent pulses, significantly outperforms other schemes. The results also show that pulse repetition scheme with equal power pulses in a doublet structure does not provide a good solution from the perspective of SNR degradation.

Spread spectrum clock generator

Abstract: Disclosed is a spread spectrum clock generator which includes: a first delay control type oscillator that variably controls an oscillation period at a control period interval according to a control signal; a control circuit; a maximum modulation value determination circuit that determines a maximum modulation value from a predetermined value, a frequency control signal, and a given modulation degree setting signal; a modulation signal generation circuit that receives the maximum modulation value from the maximum modulation value determination circuit and generates a modulation control signal within the maximum modulation value; and a second delay control type oscillator that receives a value obtained by adding the modulation control signal from the modulation signal generation circuit to the frequency control signal as a control signal and variably controls the oscillation period of an output clock signal at the control period interval according to the control signal. The control circuit outputs the frequency control signal for variably controlling the oscillation period based on the result of phase comparison between a clock signal obtained by frequency dividing the output of the first delay control type oscillator and a frequency divided clock signal of a reference clock signal, performed by a phase comparator.

Heat pump with pulse width modulation control

Abstract: A heat pump is provided with a component that has a pulse width modulation control to adjust system capacity. Thus, by utilizing a pulse width modulation technique to control this component, the present invention is able to closely tailor the delivered capacity of the heat pump to that which is demanded, without cycling the unit. In one embodiment, the component has a suction pulse width modulation valve. In another embodiment, the component which is modulated is the compressor pump unit, and, in particular, a pair of scroll members that are allowed to move into and out of contact with each other. The pulse width modulation control device can also be utilized in combination with a heat pump having an economizer function and/or an unloader function.

High-frequency heating power supply device

Abstract: There is provided a high-frequency heating power supply device for driving a magnetron such as a microwave oven. It is possible to provide a frequency modulation method for suppressing high-frequency current generated by high-frequency switching operation. When supplying a DRIVE signal for driving a first semiconductor switching element (3) and a second semiconductor switching element (4), the inverter operation frequency for each commercial power supply phase is supplied with a frequency difference (inclination) of phase 0 to 90 degrees by a triangular wave generation circuit in an oscillation circuit (16). The modulation waveform for frequency modulation control is formed by setting the upper limit clamp, the lower limit clamp, and the lowest value equivalent to the lowest frequency by the frequency modulation generation circuit (15) according to the commercial power supply division waveform after rectification. By optimally combining these, generation of higher harmonic current is suppressed while forming a frequency modulation waveform capable of absorbing various irregularities such as an inverter main circuit parts constant and a power source (Vcc) of drive control IC unit (14).