Browse Prior Art Database

Combined Dimmer and Voltage Regulator Circuit for Fluorescent Lamp Inverter

IP.com Disclosure Number: IPCOM000110499D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Nakano, M: AUTHOR

Abstract

This article describes a circuit with combined dimmer and voltage regulator for fluorescent lamp inverter.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 79% of the total text.

Combined Dimmer and Voltage Regulator Circuit for Fluorescent Lamp Inverter

       This article describes a circuit with combined dimmer and
voltage regulator for fluorescent lamp inverter.

      Recently, a back light inverter for a Liquid Crystal Display
(LCD) requires a wide range of dimming function to be able to be used
in any environment.  Also, a wide input voltage range is required for
battery operation.

      In a conventional inverter circuit, a DC-DC converter is
applied to a chopped dimming circuit, as shown in Fig. 1 to implement
those requirements, the chopped dimming circuit has wide range
dimming capability because the dimming ratio depends only on its
chopping on/off ratio.  DC-DC converter is working to stabilize input
voltage.  This configuration works well except for power consumption.
Because the input current flows through two switching devices, power
loss is generated twice in the same object which means a current
switching.

      The disclosed circuit combines those switching devices.  Fig. 2
shows this circuit diagram. A PWM control circuit which works as
DC-DC converter with switching device is chopped by a chop control
circuit for dimming.  The PWM control circuit watches an inverter's
average input voltage (VCHOP in Fig. 2) to keep fixed output current
of the inverter (IOUT).  The PWM control circuit is switched by the
chop control circuit.  The chop control circuit turns the DC-DC
converter on/off to change the ratio o...