VGH VGL & VCOM Boost Module Circuit Diagram Using NE555 IC

How do you do a VGH VGL VCOM voltage supply module using NE555 IC? Here are complete guidelines with a schematic circuit diagram.
Dear friends, When repairing an LED TV, especially when there is a problem with the LED TV panel, such as no picture on the LED TV screen, the screen becomes black or white. There are some vertical or horizontal lines on the screen; then, we check whether VGH, VGL, AVDD, and VCOM voltage is output or not output from the DC to DC boost converter section. When such symptoms appear on the LED/LCD TV screen, in some cases, we see that any one or more of the voltages of VGH, VGL, AVDD, and VCOM are not being output. In this situation, first, we must ensure whether there is any short circuit or overload load problem in gate COF and source COF circuits.

Moreover, in some T-Con circuits, you will find that the VGH and VGL supplies are not directly connected to get a COF circuit; in such Circuits, the VGH and VGL supplies are input to the logic level shifter IC, and the flip-flop voltage is output from the output section of that IC, which is called ODD voltage and EVEN voltage. If any component is short in that logic level shifter section or shorted the logic level shifter IC, the VGL and VGH voltages will not be output.

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In that case, if we can be sure that there is no short circuit in the Get COF, Source COF, Logic Level Shifter, Gamma, and any other sections, the VGL, VGH, Gamma Reference, and VCOM voltages are not output from the DC-to-DC converter circuit, in a word- if we can be sure that the DC-to-DC converter IC itself is not working, or the DC-to-DC converter IC is damaged, then the DC to DC IC needs to be changed. But suppose the DC-to-DC converter IC is unavailable in the market, or we cannot procure it. In that case- We can use the CA508 or Gold-92 module for the VGH VGL AVDD VCOM supply. Still, unfortunately, The thing I have noticed is that these modules become damaged after a while, so I made my own VGH VGL VCOM module for LED TV repair, the schematic circuit diagram I published below.

[ RT9955 DC-to-DC converter Schematic Circuit Diagram- Click Here ]

VGH VGL VCOM Module Circuit Diagram

In this circuit, the NE555 IC is working as a pulse generator. It has a negative supply at pin 1, a positive at pins 4 and 8, and an oscillating current output from pin 3 to the base of the boost output transistor.

IC2 - KA7805 For 5 Volts VCOM, KA7806 for 6 Volts VCOM. KA7808 for 8 Volts VCOM.
R1 - 2.2K,  R2- 22K,  R3- 1K,  R4- 1K,  R5- 2.2K. VR1- 100K.
C1- 2.2µFD,  470pf,  C3- 0.1µF, C4- 0.1µF, C5- 220µF/25V, C6- 2.2µF / 100V, C7- 0.1µF.
D2- 16V Zener diode for 16 Volts VGH,  24V Zener DIode for 24 Volts VGH. 30V Zener Diode for 30 Volts VGH,  33V Zener Diode for 33 Volts VGH.

The circuit's inductor will have 90 turns on the L1 part for the VGH output and 13 turns on the L2 coil for the VGL output. 30-gauge super enamel wire coils should be wound in the same direction. As shown in Figure 2, the core size is 10 mm.
TR1- BC337.  D1,D4- IN4007, IC1 - KA7805

Figure- 2: Inductor For VGH VGL VCOM Module

L1- 90 turns,  L2- 13 turns, Ferrite core size - 10mm, Wire size- 29 SWG.
CAUTION- Before connecting VGH from the external NE555 VGH module to the T-Con board, resistors R123 and R124 should be removed.

[6861AAQ DC-to-DC converter Schematic Circuit Diagram- [HERE ]

VGH Boost Module Schematic Circuit Diagram

An LCD TV or monitor's LCD panel contains hundreds of thousands of thin-film transistors (TFTs) inside the glass. High gate (VGH) voltages are applied to the TFTs' gate terminals to activate the liquid crystal cells. Only 50mA current flows through the TFTs' gate terminals. The circuit diagram below shows the VGH voltage output through the 2.2 kOhms resistor for the TFTs.

VGH Module Circuit Diagram

List of components and values:
R1- 2.2KΩ,  R2- 22KΩ, R3- 1KΩ, R4- 1KΩ.
C1- 2.2µFD - 100V,  C2- 470PF,  C3 & C4- 0.1µFD, C5- 100µFD- 25V

D1- IN4007,  D2- 16V Zener diode for 16 Volts VGH,  24V Zener DIode for 24 Volts VGH. 30V Zener Diode for 30 Volts VGH,  33V Zener Diode for 33 Volts VGH.
IC- KA7805, IC2- NE555. L1- 400µH.

Figure 4: The inductor of the VGH Boost Module

The size and type of core of the L1 inductor are shown in Figure 4. Wire Size- 30SWG

Figere-5: VGH Boost Module

Video about VGH VGL & VCOM Boost and Bulk Converter Module.
Looking at the picture above (Figure 4) of the VGH Boost module, you can understand that it is straightforward to make because the number of components in this module is significantly less.
The NE555 IC is used in pulse generators, oscillators, TIMERS, and delay applications. Anyone who built various electronic projects with the NE555 IC can quickly make the VGH VGL VCOM AVDD module.

Once you create this VGH VGL VCOM AVDD module, you can make the next one in 15 minutes.
CAUTION—Before connecting VGH from the external NE555 VGH module to the T-Con board, resistors R123 and R124 should be removed.
If you are new to electronics, make a Delay Timer circuit with this 555-timer IC to practice your skill development.