Cold-Cathode Fluorescent-Lamp Supply

For backlit LCD displays, this supply will drive a lamp. The LT1072 drives Q1 and Q2, while a sine wave appears across C1. L1 is a transformer that steps up this voltage to approximately 1400 V. D1 and D2 detect lamp current and form a feedback loop to the LT1072 to control lamp brightness. C1 must be a low-loss capacitor, with the recommended component being the metalized polycarbonate WIMA FPK 2 (German). L1 can be either the Sumida 6345-020 or Coiltronix CTX110092-1, with pin numbers provided for the Coiltronix unit. L2 is specified as Coiltronix CTX300-4, and a 1% film resistor is used.

This electronic circuit is designed to drive a backlit LCD display by controlling a high-voltage lamp. The core of the circuit is the LT1072, a precision switching regulator that operates in conjunction with two transistors, Q1 and Q2, to efficiently manage the power supplied to the lamp. The circuit generates a sine wave across capacitor C1, which is crucial for the operation of the lamp.

L1 functions as a transformer, stepping up the voltage to approximately 1400 V, which is necessary for the lamp to achieve optimal brightness. The feedback mechanism is implemented through diodes D1 and D2, which monitor the lamp current. This feedback is fed back to the LT1072 to adjust the output, ensuring consistent brightness and preventing overcurrent conditions that could damage the lamp.

For capacitor C1, a low-loss component is critical to minimize energy loss and improve efficiency. The WIMA FPK 2 is recommended due to its excellent performance characteristics in high-frequency applications.

Inductor L1 can be selected from either the Sumida 6345-020 or Coiltronix CTX110092-1, with specific pin configurations provided for the Coiltronix model to facilitate integration into the circuit. Inductor L2, specified as Coiltronix CTX300-4, plays a role in managing the inductor's performance and ensuring stability in the circuit.

The use of a 1% film resistor in the design contributes to the precision of the feedback loop, allowing for accurate control of the lamp's brightness and enhancing the overall reliability of the circuit. This schematic is suitable for applications requiring efficient backlighting solutions, such as in LCD displays, ensuring both performance and longevity of the components involved. For back-lit LCD displays, this supply will drive a lamp. LT1072 drives Ql and Q2, and a sine wave app ears across CI. LI is a transformer that steps up this voltage to about 1400 V. Dl and D2 detect lamp current and form a feedback loop to the LT1072 to control lamp brightness. C1 = MUST BE A LOW LOSS CAPACITOR. METALIZED POLYCARB WIMA FPK 2 (GERMAN) RECOMMENDED. L1 = SUMIDA 6345-020 OR COILTRONIX CTX110092-1. PIN NUMBERS SHOWN FOR COILTRONIX UNIT. L2 = COILTRONIX CTX300-4 * = 1 % FILM RESISTOR. 🔗 External reference