|
Random Pulse-width Modulation
Random pulse-width modulation (RPWM) is a modulation technique introduced for mitigating electromagnetic interference (EMI) of power converters by spreading the energy of the noise signal over a wider Bandwidth (signal processing), bandwidth, so that there are no significant peaks of the noise. This is achieved by randomly varying the main parameters of the pulse-width modulation signal. Description Electromagnetic interference (EMI) filters have been widely used for filtering out the conducted emissions generated by power converters since their advent. However, when size is of great concern like in aircraft and automobile applications, one of the practical solutions to suppress conducted emissions is to use random pulse-width modulation (RPWM). In conventional pulse-width modulation (PWM) schemes, the Harmonics (electrical power), harmonics power is concentrated on the deterministic or known frequencies with a significant magnitude, which leads to mechanical vibration, noise, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modulation
Signal modulation is the process of varying one or more properties of a periodic waveform in electronics and telecommunication for the purpose of transmitting information. The process encodes information in form of the modulation or message signal onto a carrier signal to be transmitted. For example, the message signal might be an audio signal representing sound from a microphone, a video signal representing moving images from a video camera, or a digital signal representing a sequence of binary digits, a bitstream from a computer. This carrier wave usually has a much higher frequency than the message signal does. This is because it is impractical to transmit signals with low frequencies. Generally, receiving a radio wave requires a radio antenna with a length that is one-fourth of the wavelength of the transmitted wave. For low frequency radio waves, wavelength is on the scale of kilometers and building such a large antenna is not practical. Another purpose of modulation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Duty Cycle
A duty cycle or power cycle is the fraction of one period in which a signal or system is active. Duty cycle is commonly expressed as a percentage or a ratio. A period is the time it takes for a signal to complete an on-and-off cycle. As a formula, a duty cycle (%) may be expressed as: :D = \frac \times 100\% Equally, a duty cycle (ratio) may be expressed as: :D = \frac where D is the duty cycle, PW is the pulse width (pulse active time), and T is the total period of the signal. Thus, a 60% duty cycle means the signal is on 60% of the time and off 40% of the time. The "on time" for a 60% duty cycle could be a fraction of a second, a day, or even a week, depending on the length of the period. Duty cycles can be used to describe the percent time of an active signal in an electrical device such as the power switch in a switching power supply or the firing of action potentials by a living system such as a neuron. Some publications use \alpha as the symbol for duty cycle. As a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conducted Emissions
Conducted emissions are the effects in power quality that occur via electrical and magnetic coupling, electronic switch of semiconductor devices, which form a part of electromagnetic compatibility issues in electrical engineering. These affect the ability of all interconnected system devices in the electromagnetic environment, by restricting or limiting their intentional generation, propagation and reception of electromagnetic energy. Conducted emissions consist a part of electromagnetic interference in circuits that mainly create issues in delivered power quality, owing to interference caused by harmonics arising due to ''linear'' & ''non linear'' loads present in the electric system mainly due to increasing presence of switched mode power supply and other consumer electronics. Due to these aggregated interferences, the delivered electric power quality from the mains electricity system affects the performance of electrical home appliances. These could include a decrease in lumen ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
