Showing papers by "Dragan Maksimovic published in 2003"

High-frequency digital PWM controller IC for DC-DC converters

Abstract: This paper describes a complete digital PWM controller IC for high-frequency switching converters. Novel architecture and configurations of the key building blocks are A/D converter, compensator, and digital pulse-width modulator, are introduced to meet the requirements of tight output voltage regulation, high-speed dynamic response, and programmability without external passive components. The implementation techniques are experimentally verified on a prototype chip that takes less than 1 mm/sup 2/ of silicon area in a standard 0.5 /spl mu/ digital complementary metal oxide semiconductor (CMOS) process and operates at the switching frequency of 1 MHz.

Predictive digital current programmed control

Abstract: This paper explores predictive digital current programmed control for valley, peak or average current. The control laws are derived for the three basic converters: buck, boost, and buck-boost. It is found that for each variable of interest (valley, peak or average current) there is a choice of the appropriate pulse-width modulation method to achieve predictive digital current control without oscillation problems. The proposed digital control techniques can be used in a range of power conversion applications, including rectifiers with power factor correction (PFC). Very low current distortion meeting strict avionics requirements (400-800 Hz line frequency) is experimentally demonstrated on a digitally controlled boost PFC employing predictive average current programmed control.

Self-tuning digitally controlled low-harmonic rectifier having fast dynamic response

Abstract: This paper describes a completely digitally controlled high-performance low-harmonic rectifier. It is shown that the dynamics of the outer voltage loop can be significantly improved using a self-tuning digital comb filter. Low input current harmonics and fast voltage transient responses are experimentally verified on a 200 W universal-input boost rectifier operating at the switching frequency of 200 kHz.

Dead-zone digital controller for improved dynamic response of power factor preregulators

Abstract: This paper presents a simple control method for improvement of dynamic responses in a digitally controlled low-harmonic rectifier with power factor correction (PFC). The controller uses a fixed or self-adjusting dead zone in analog-to-digital conversion to eliminate the output capacitor ripple from the voltage control loop. The proposed control methods are tested in a completely digitally controlled 200 W boost PFC operating at 200 kHz switching frequency. Experimental results show that the simple controller implementation results in low current harmonics and significantly improved output voltage transient responses.

Digital controller chip set for isolated DC power supplies

Abstract: This paper describes a digital controller chip set for high-frequency DC-DC power converters with galvanic isolation. The secondary-side controller includes an A/D converter and a transmitter that sends a digital error signal as serial data through an opto-coupler. The primary-side controller includes a serial-data receiver, a programmable digital PID regulator, and a high-resolution (10-bit) digital pulse-width modulator. The digital error signal transmission through the isolation boundary eliminates the problem of gain variation when the opto-coupler is used in linear mode. The chip set is tested as a replacement for a conventional analog current-mode controller in a 3.3 V, 20 A, 400 KHz DC power supply. Experimental results with the digital controller show improved dynamic responses compared to the responses obtained with the analog controller.

High-performance front-end converter for avionics applications [aircraft power systems]

Abstract: The distributed power systems of future commercial aircraft will adopt variable frequency generation (360 to 800 Hz). Front-end converters in the system will be required to have a high efficiency and a low total harmonic distortion (THD) of the input current. This paper explains the design of a zero-voltage-switching (ZVS) active-clamped isolated low-harmonic SEPIC rectifier for such applications. Utilization of the transformer leakage inductance for ZVS and a single-layer transformer design contribute to a high efficiency. An accurate averaged switch model has been developed, which shows that the control-to-input-current transfer function of this converter does not exhibit resonances observed in the conventional SEPIC. As a result, for closed-loop operation using average current control, damping of the coupling capacitor is not required. Operating at a switching frequency of 200 kHz, an experimental 100 W, 28 V output rectifier achieves a THD of 3-4% and efficiency exceeding 90% over the entire line frequency range.

Adaptive voltage scaling clock generator for use in a large-scaledigital ntegrated circuit and method of operating the same

Abstract: There is disclosed clock control circuitry (705,710, 715) for selectively applying a clock signal to a digital processing component (100) wherein the clock signal is capable of being changed to a plurality of operating frequencies. The clock control circuitry (705,710, 715) is operable to (i) receive a command to change a first operating frequency to a second operating frequency, (ii) in response to the command, disable the applied clock signal, (iii) generate a test clock signal having the second operating frequency, (iv) apply the test clock signal to a power supply adjustment circuit (125), and (v) sense a status signal from the power supply adjustment circuit (125). The status signal indicates that a power supply level of the digital processing component (100) has been adjusted to an optimum value suitable for the second operating frequency.