A General Constant Frequency Pulse-Width Modulator and Its Applications
Background: Switching converters are commonly used to provide DC to DC, DC to AC, AC to DC, and AC to AC conversion of electrical waveforms. These converters are often categorized by applicable circuit configuration and/or capabilities, and include buck converters (where the load voltage is less than the source voltage), boost converters (where the load voltage is greater than the source voltage), Cuk converters, Watkins-Johnson converters, and A, B, and C quadratic converters. All of these converters rely on switching control and, furthermore, the prerformance of electrical circuits, including converters, can be improved by closed loop control of a control variable selected by the designer.Constant frequency pulse-width modulation (PWM) is a well-known method to control switching converters. However, while PWM control is often relatively simple in theory, it is not in application. While modulation equations describing the required mathematical relationships between the controlled variable and the modulation equation may be expressed in closed form, implementing these mathematical relationships in electrical circuitry to effect the desired control scheme is often a complicated, time-consuming, and expensive process, requiring extensive analysis, special electrical components, or additional circuitry. Technology: Therefore, there is a need for a pulse-width modulator which allows the system and circuit designer to implement a wide variety of constant-frequency control schemes without the need for special circuit components or specially designed circuits requiring extensive analysis and design.
Researchers at the Power Electronics Laboratory at the University of California, Irvine, have developed a constant frequency pulse-width modulator that realizes various control schemes with trailing-edge, leading-edge, or double-edge modulation. This PWM modulator, which employs one or more integrators with reset stages, can be generally applied to implement feed-forward control of a family of converters, current mode control with linear or non-linear compensation slope, and a family of unity-power-factor rectifiers at continuous or discontinuous conduction mode.
Patents:
US 5,886,586
Type of Offer: Licensing
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