Conventional boost PFC suffers from the high conduction loss in the input rectifier-bridge. Higher efficiency can be achieved by using the bridgeless boost topology. This new circuit has issues such as voltage sensing, current sensing and EMI noise. In this paper, one cycle control technique is used to solve the issues of the voltage sensing and current sensing. Experimental results show efficiency improvement and EMI performance

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Bridgeless PFC implementation using one cycle control technique

A major consideration in designing controllers for boost converters is the existence of a right-half-plane zero in the control-to-output transfer function. This property makes the controller impossible to be designed in classical frequency-domain approach to achieve fast dynamic response over wide bandwidth of supply and load variations. In this paper, a time-domain boundary control concept for large-signal control of boost converters is proposed. By transforming the conventionally used state plane into the newly proposed state-energy plane to dictate the switching instants, a well-defined switching surface is derived. The converter can ideally revert to the steady state in two switching actions when it is subject to external disturbances. Of particular importance, experiments show that the same controller is applicable for controlling converters operating in continuous conduction mode, critical conduction mode, or discontinuous conduction mode. Sensitivities of the switching surface to parametric variations will be studied. Theoretical predictions will be verified with the experimental results of a 55 W, 48 V/110 V prototype.

Boundary Control of Boost Converters Using State-Energy Plane

The small-signal control-to-output transfer function of boost converters consists of a right-half-plane zero, which is typically the main consideration in designing the controller with classical control theories. Instead of designing the controller in frequency domain, a time-domain boundary control method for large-signal control of boost converters will be presented in this paper. By transforming the state plane into a state-energy plane to dictate the switching instants, a well-defined switching surface is derived. The converter has good output regulation, as well as good dynamic behaviors. The converter can revert to the steady state in two switching actions during the external disturbances. Of particular importance, the same controller is applicable for converter operating in all three modes, including continuous conduction mode, critical conduction mode, and discontinuous conduction mode. Theoretical predictions are verified with the experimental results of a 100W prototype.

This paper proposes a new nonlinear control technique that has one-cycle response, does not need a resetable integrator in the control path, and has nearly constant switching frequency. It obtains one-cycle response by forcing the error between the switched variable and the control reference to zero each cycle, while the on and off pulses of the controller are adjusted each cycle to ensure near constant switching frequency. The small switching frequency variation due to changes in the reference signal and supply voltage and delays in the circuit are quantified. Using double-edge modulation, the switching frequency variation is further reduced, thus, the associated signal distortion is minimized. An experimental 0-20 kHz bandwidth 95 W RMS power audio amplifier using the control method demonstrates the applicability of this control technique for high-fidelity audio applications. The amplifier has a power supply ripple rejection (PSRR) of 63 dB at 120 Hz. Additionally, the total harmonic distortion plus noise (THD+N) is less than 0.07% measured with a power supply ripple of 15%.

A new PWM controller with one-cycle response

An important distortion mechanism in hysteretic self-oscillating (SO) class-D (switch mode) power amplifiers-carrier distortion-is analyzed and an optimization method is proposed. This mechanism is an issue in any power amplifier application where a high degree of proportionality between input and output is required, such as in audio power amplifiers or xDSL drivers. From an average-mode point of view, carrier distortion is shown to be caused by nonlinear variation of the hysteretic comparator input average voltage with the output average voltage. This easily causes total harmonic distortion figures in excess of 0.1-0.2%, inadequate for high-quality audio applications. Carrier distortion is shown to be minimized when the feedback system is designed to provide a triangular carrier (sliding) signal at the input of a hysteretic comparator. The proposed optimization method is experimentally proven in an audio power amplifier leading to THD figures that are comparable to the state of the art. Experimental hardware is a hysteretic SO bandpass current-mode-controlled single-ended audio power amplifier capable of 45 W into 8 Omega or 80 W into 4Omega from a plusmn34 V supply with less than 0.03% THD from 100 Hz to 6.7 kHz. Carrier distortion is shown to account for this limitation in THD performance.

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Carrier Distortion in Hysteretic Self-Oscillating Class-D Audio Power Amplifiers: Analysis and Optimization

This paper proposes a new nonlinear control technique that has one cycle response, does not need a resettable integrator in the control path, and has nearly constant switching frequency. It obtains one cycle response by forcing the error between the switched-variable and the control reference to zero, each cycle. The on-pulse of the controller is adjusted each cycle by a simple circuit to ensure almost constant switching frequency. The small switching frequency variation due to variations in the reference signal and supply voltage and delays in the circuit are quantified. An additional improvement is achieved by using double edge modulation. An experimental 10 kHz bandwidth 100 Watt RMS power audio amplifier using the control method shows THD+N less than 0.62% and power supply ripple rejection (PSRR) of 56 dB demonstrating the applicability of this control technique for high fidelity audio applications.

Z. Lai

Papers

A new PWM controller with one-cycle response

A new PWM controller with one cycle response