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New voltage drivers from Supertex

Posted: 17 Aug 2005 ?? ?Print Version ?Bookmark and Share

Keywords:supertex? hv839? hv841? high voltage driver? el lamp?

Designed for driving two EL lampsThe new HV839 and HV841 from Supertex are high voltage drivers designed for driving two EL lamps with a combined area of 3.5-inches?. The input supply voltage range is from 2V to 5.8V.

Designed to reduce the amount of audible noise emitted by the lamp, these devices use a single inductor and minimum number of passive components to drive two EL lamps. The nominal regulated output voltage of 90V for the HV839 and 100V for the HV841 is applied to the EL lamps. The chip can be enabled/disabled by connecting C1 and C2 (pins 1 and 4) to VEN/Ground.

The HV839 and the HV841 have an internal oscillator, a switching MOSFET and two high voltage EL lamp drivers. An external resistor connected between the RSW-OSC and the voltage supply pin VDD sets the frequency for the switching MOSFET. The EL lamp driver frequency is set by dividing the MOSFET switching frequency by 128. An external inductor is connected between the LX and the input voltage supply, VIN.

Depending on the EL lamp size, a 1nF to 10nF, 100V capacitor for the HV839, and a 1nF to 10nF, 200V capacitor for the HV841, is connected between CS and Ground. The two EL lamps are connected between EL1 to Com and EL2 to Com.

Supertex explained that the switching MOSFET charges the external inductor and discharges it into the capacitor at CS. The voltage at CS increases. Once the voltage at CS reaches a nominal regulation voltage, the switching MOSFET is turned OFF to conserve power. The outputs EL1 to Com and EL2 to Com are configured as H bridges and switch in opposite states to achieve the higher voltage (180V for the HV839 and 200V for the HV841) across the EL lamp.

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