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This paper presents a filterless Class-D amplifier with pseudorandomized carrier frequency modulation (PRCFM) to mitigate electromagnetic interference (EMI) issue associated with the removal of an off-chip LC filter. The designed filterless Class-D amplifier occupies a total area of 1 mm2 and is fabricated in 0.18-μm CMOS process technology. The pr...
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In this article, a new model to predict the amplitude reduction of the interference harmonics in power supplies with parallel topology is presented when the switching frequency modulation with variable delay (VDFM) technique is applied. The VDFM method consists of combining the interleaving and switching frequency modulation (SFM) techniques. The n...
Citations
... Implementing SSCG with a direct modulation voltagecontrolled oscillator has shown superior EMI reduction performance [23]. The primary modulation methods include periodic signal modulation [16], [17], random signal modulation [24], [25], and chaotic signal modulation [26], [27]. However, employing chaotic signal modulation requires large-area capacitors and inductors, which may not be suitable for motor drive circuits. ...
Reducing the impact of electromagnetic interference (EMI) on switching inverters is an essential part of improving the performance of motor drives. This paper proposed a charge pump circuit with a hybrid modulation method to reduce the EMI of motor drive chips. This innovative method uses a combination of coarse modulation and fine modulation. The periodic modulation technique is used as coarse modulation to alter the spread spectrum range, while the random modulation technique is used as fine modulation to slow down switching transitions by adjusting the delay of the oscillating signal edges. Additionally, a buffer circuit is proposed to restrict the charge and discharge current of the charge pump, thus reducing the EMI due to the rapid variation of the current peak. Theoretical analysis and MATLAB simulation have confirmed that the hybrid modulation method has a pronounced effect on reducing the EMI of the circuit. The proposed motor drive system has been designed and verified by a 0.18um BCD process, and the test results show that the proposed circuit can reduce the EMI by up to 20 dB compared to the non-modulated circuit. The motor driver chip area is 0.173
mm
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, and the power consumption is 5.677mW.
... Spreadspectrum methods differ from regular PWM in that the switching frequency of the semiconductors is changed to distribute the energy of the switching distortion to a greater frequency band, decreasing the spectral peaks. The switching frequency is either modulated in fixed patterns [28], [29], or chaotically [30], [31]. ...
In automotive power electronics, distortion and electromagnetic interference (EMI) generated by the switching action of power semiconductors can be a significant challenge for the design of a compact, lightweight vehicle. As semiconductor switching frequencies increase, e.g., through the introduction of new materials, such as gallium nitride and silicon carbide, this problem becomes more severe. We present a control scheme for an automotive dc-to-dc converter that reduces the EMI generated by shaping switching distortion predictively at the run time. The multistep model-predictive control scheme chooses the subsequent switching state that optimizes the output spectrum according to predefined criteria. To achieve real-time operation, it evaluates the possible switching state candidates for the next modulation step without explicitly solving a single Fourier transform. In addition, the switching rate and voltage ripple are controlled in a single unified control law. We present and experimentally validate that the control scheme can indeed run at real time already with currently available mid-range hardware. The results demonstrate that the largest spectral peak of the switching distortion can be decreased by 48 dB compared to conventional pulse-width modulation. Furthermore, spectral gaps can be implemented in the output distortion and altered in real-time, allowing certain frequency bands -- e.g., bands used by other sensitive electronics such as sensors, communication busses, or tuners -- to be kept free of EMI from the converter's switching actions.
... Spreadspectrum methods differ from regular PWM in that the switching frequency of the semiconductors is changed to distribute the energy of the switching distortion to a greater frequency band, decreasing the spectral peaks. The switching frequency is either modulated in fixed patterns [29], [30], or chaotically [31], [32]. ...
In automotive power electronics, distortion and electromagnetic interference (EMI) generated by the switching action of power semiconductors can be a significant challenge for the design of a compact, lightweight vehicle. As semiconductor switching frequencies increase, e.g., through the introduction of new materials, such as gallium nitride and silicon carbide, this problem becomes more severe. We present a control scheme for an automotive dc-to-dc converter that reduces the EMI generated by shaping switching distortion predictively at the run time. The multistep model-predictive control scheme chooses the subsequent switching state that optimizes the output spectrum according to predefined criteria. To achieve real-time operation, it evaluates the possible switching state candidates for the next modulation step without explicitly solving a single Fourier transform. In addition, the switching rate and voltage ripple are controlled in a single unified control law. We present and experimentally validate that the control scheme can indeed run at real time already with currently available mid-range hardware. The results demonstrate that the largest spectral peak of the switching distortion can be decreased by 48 dB compared to conventional pulse-width modulation. Furthermore, spectral gaps can be implemented in the output distortion and altered in real-time, allowing certain frequency bands—e.g., bands used by other sensitive electronics such as sensors, communication busses, or tuners—to be kept free of EMI from the converter’s switching actions.
... The input signal of the power amplifier is modulated into a pulse signal by the digital modulator, and then, the power stage amplifies the pulse signal to drive the speaker. Comparing with the traditional class D power amplifier, the filterless digital class D power amplifier eliminates the LC low-pass filter circuit between the power stage and the speaker by utilizing a special modulation technique, while greatly shrinking the system size, reducing the system cost and making the system easier to integrate; meanwhile, the power efficiency will not be decreased [8,11]. ...
Filterless digital class D power amplifiers usually utilize three-level uniform sampling pulse width modulation (UPWM) technique to convert the digital input signal into a UPWM signal which is used to drive the power stage. Therefore, the spectral estimation expressions for different three-level UPWM signals obtained by modulating the digital signal can be an evaluation tool for signal distortion and electromagnetic interference when filterless digital class D power amplifiers are designed. Based on the time-domain characteristics of three-level UPWM signals, the spectral estimation expressions for six types of three-level UPWM signals are proposed in this paper by using the discrete Fourier transform technique and the frequency response of the zero-order holder. According to these expressions, the relationships among the total harmonic distortion, the pulse repetition frequency and the pulse width resolution of the UPWM signal are studied. A UPWM generator test system based on field-programmable gate array is designed and implemented to measure the spectra of different UPWM signals. The measured results are compared with the calculated results obtained by the proposed expressions to verify the correctness of the proposed expressions.
... Therefore, a pseudo-random modulation designed for a Class D amplifier (Jin, Tan, & See, 2013;Ming, Chen, Zhou, & Zhang, 2011), is transplanted into the inductor-based converter to suppress EMI without any other ancillary circuits in this paper. The pseudo-random modulation is achieved by combining LFSR and a digitally controlled oscillator (DCO). ...
This paper presents a self-powered inductor-based converter which harvests thermoelectric energy and boosts extremely-low voltage to a typical voltage level for supplying body sensor nodes. Electromagnetic interference (EMI) of the converter is reduced by spreading spectrum of fundamental frequency and harmonics via pseudo-random modulation, which is obtained via combining the linear feedback shift register and digitally controlled oscillator. Besides, the methods, namely extracting energy near MPP and reducing the power dissipation, are employed to improve the power efficiency. The presented inductor-based converter is designed and verified in CSMC CMOS 0.18um 1P6M process. The results reveal that it achieves the high efficiency and EMI reduction at the same time.
This paper presents new and original architectures and implementations of two filterless, open-loop digital Class-BD audio amplifiers with constant common mode (CM) output voltage. The first, low-power amplifier consists of four ultrahigh-current EL7158 pin drivers, the OUT pins of which form the H bridge. The drivers are controlled from the extended LBDD PWM modulator and have appropriately set voltage levels on the VL and VH pins. The second proposed amplifier consists of two cooperating H-bridge power stages (HBS) implemented on complementary MOSFET pairs and powered by two different voltages. Both HBSs are driven by four EL7158 pin drivers having appropriately adjusted voltage levels on the VL and VH pins and controlled by an extended LBDD PWM modulator. The hybrid 9 bit DPWM modulator uses a linearized Class-BD double-sided modulation scheme with pre-compensation, enabling the most faithful emulation of natural NBDD PWM and, thus, providing attractive spectral characteristics at the DM output. Basic SPICE simulations and experimental results of the proposed digital Class-BD amplifiers were compared with the conventional digital Class-BD amplifiers. The elimination of CM signals significantly contributes to the reduction in electromagnetic interference (EMI), particularly those produced on the cables connecting the loudspeaker to the HBS terminal. Proposed Class-BD amplifiers with original and new topologies, due to their simple design and easy control (no galvanic isolation of control signals and no floating bias power supplies), which generate no CM voltage and feature excellent DM performance, similar to conventional Class-BD amplifiers, are very attractive solutions for filterless Class-BD amplifiers.
In AC motor drive, the fixed-frequencies harmonic components of output voltage and current from the inverter with fixed frequency pulse width modulation (FFPWM) usually lead to electromagnetic interference (EMI). The spread spectrum clock generation (SSCG) is a widely used solution of this problem. Adjusting the switching frequency to reduce EMI is one kind of practicable scheme among SSCG methods. About this scheme, usually, how to design an optimal modulation waveform is the research emphasis of scholars. However, apart from modulation waveform, the mode and quality of carrier is also important and can be improved. In most frequency modulation methods, due to the limitation of the conventional carrier generation mode, implement of new frequency instruction has to wait for the termination of last switching period. In order to eliminate the waiting state, this paper proposes a wait-free phase-continuous carrier frequency modulation strategy (WPCFM) by combining the DDS theory and proper temporal planning of control interruptions. Besides, theoretical analysis of WPCFM including quantization error, frequency jitter, phase delay and voltage distortion are finished. Moreover, compared with conventional methods, a more convenient, feasible and simpler field-programmable gate array (FPGA) based algorithm implementation method and the control structure of WPCFM are also introduced. Analysis shows that, although WPCFM causes a slight increase of the current ripple, it can solve the partial frequency nonuniform distribution problem of conventional method and it has potential value of applications in the wide band gap (WBG) motor drive systems. The effectiveness of the WPCFM is verified by several sets of EMI reduction experiments where classical periodic carrier frequency modulations are applied1.
Audio amplifiers for portable devices need to be power efficient, therefore Class-D amplifiers are used. These amplifiers employ a switching output stage, so that they generally produce a significant amount of EMI. Filtering these frequency components usually is not an option since the amplifiers have to be small and lightweight. A reduction of EMI can be achieved by using spread-spectrum techniques that distribute the emissions over a wider frequency range. Unfortunately spread-spectrum techniques can impact the audio performance. This work presents a test setup for a Class-D prototype to evaluate different spread-spectrum methods by measurement or even by listening to the audio output. Using this setup several spread-spectrum methods are compared in terms of EMI-reduction and audio performance.
