US 7,064,497 B1Granted

Dead-time-modulated synchronous PWM controller for dimmable CCFL royer inverter

AssigneeNational Taiwan University of Science and Technology

InventorGuan-Chyun Hsieh

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Abstract

A Synchronous PWM controller realized by dead-time modulation is provided for applying to the self-oscillation Royer inverter. The proposed dead-time-modulated PWM (DTM-PWM) controller is composed of a monostable circuit and a constant-current charger (CCC). The presented switching period for the buck regulation consists of a referred sawtooth having a constant-period and a dead-time. The synchronizing strategy is conducted by modulating the dead-time according to the resonant frequency of the Royer inverter. Two kinds of the control strategies in DTM-PWM controller are explored including the down-going and up-going error voltage controls. A DTM-PWM controlled dimmable Royer inverter with two-CCFL having primary-side control is designed and realized. Two kinds of the existing controllers for the Royer inverter are also experimented and compared with the proposed DTM-PWM controller. The results of the analysis and the theoretical prediction are verified with the experiments.

Claims22

Dependent claims

A controller for providing a dead-time-modulated (DTM) synchronous pulse width modulation (PWM) to a dimmable cold-cathode fluorescent lamp (CCFL) Royer inverter, wherein a first and a second voltages are applied to said controller to generate an output voltage to control a switch for dimming said CCFL, comprising:

a constant current charger (CCC) for generating said first voltage;
a first comparator for comparing said second voltage with a first reference voltage to generate a trigger signal;
a second comparator electrically connected to said first comparator for comparing said trigger signal with a second reference voltage;
a third comparator electrically connected to said CCC for comparing said first voltage with a third reference voltage;
a flip-flop electrically connected to said second comparator and said third comparator for generating a control signal in response to the outputs of said second and said third comparators;
a discharger having a first terminal for receiving said control signal, a second terminal electrically connected to said CCC, and a third terminal electrically connected to a ground;
a fourth comparator electrically connected to said CCC for comparing an error signal with said first voltage to generate a down-going error voltage;
and
a fifth comparator electrically connected to said CCC for comparing said error signal with said first voltage to generate an up-going error voltage,
wherein said output voltage is one of said down-going and said up-going voltages.

7 more elements

Dependencies are inferred from the claim text.