Ac-dc converters typically have two converter stages -an ac-dc stage operating with power factor correction (PFC) and an isolated dc-dc stage. Researchers have proposed various integrated converters that combine the two stages into a single converter that simultaneously performs both ac-dc conversion with PFC and dc-dc conversion. In the case of voltage-fed integrated converters, however, the primary-side dc bus voltage is left unregulated, which can result in several converter performance problems such as excessive intermediate DC bus voltage and distorted input current. A new integrated voltagefed PWM single-stage converter that does not have these problems and can be used for high output power and at the same time follow IEC1000-3-4 harmonic limits and will have excellent input power factor (>0.98) will be proposed in the paper. The paper will explain the operation of the converter in detail, discuss its features, and explain how the converter can be designed. Results obtained from an experimental prototype that confirm the feasibility of the proposed converter will be presented in the paper.
I. INT RODUCT IONConventional ac-dc rectifiers are implemented with two switch-mode converter stages. The first stage is an ac-dc boost converter that converts the input ac voltage into an intermediate dc bus voltage. This converter also performs power factor correction (PFC) as it shapes the input current so that it is sinusoidal and in phase with the input voltage. The intermediate dc bus voltage is fed into the second stage converter, which is an isolated dc-dc converter that converts the bus voltage into the desired output dc voltage. This dc-dc converter is typically a flyback or forward converter for low power applications and a full-bridge converter for higher power applications. An example of a two-stage ac-dc rectifier is shown in Fig. 1; the ac-dc rectifier front-end converter is an interleaved boost converter and the dc-dc converter is a full-bridge converter.There has been considerable interest by power electronics researchers to try to combine both ac-dc PFC and isolated dc-dc conversion into a single converter. The desire to do this stems from the cost and complexity involved in implementing two separate switch-mode converters.Initial single-stage ac-dc full-bridge converters were resonant converters [1]-[5] and/or current-fed converters with a dc bus boost inductor connected to the input of the full-bridge circuit [6]- [12]. Both these types had drawbacks: The resonant converters had to be controlled by varying the switching frequency over a wide range, which made it difficult to optimize their design, and the current-fed converters had a large low frequency component at the output that restricted their use to a limited number of applications.Pulse-width modulated (PWM) voltage-fed singe-stage converters that have a large bulk capacitor connected across the bridge do not have these problems. The main drawback with all voltage-fed single-stage converters [6]-[12] is that their primary-side dc bus voltage is ...
