Showing posts with label LG TV. Show all posts
Showing posts with label LG TV. Show all posts
Tuesday, June 21, 2016
LG 42LG5000 - SMPS Power supply LGP42-08H - EAY4050530 - Power supply schematic diagram - NCP1207 - NCP1396A - SG6961 - LCD Television repair and service - Tips manual
Category: LCD Television Repair and Service
Contents of this article
- NCP1207 AC-DC Converter
- NCP1396 Resonant mode controller
- SG6961 PFC Controller
- Power supply schematic diagram
LG 42LG5000
NCP1207 AC−DC Converter
The NCP1207 is a controller dedicated for driving the current−mode free running quas −resonant Flyback offline converter. This converter is designed for consumer products like notebooks, offline battery chargers, consumer electronics (DVD players, set−top boxes, TVs), etc. The growing interest for EMI pollution reduction, efficiency improvement, and maximum safety has been taken into account while designing the NCP1207. By implementing the NCP1207 one can build a power supply that can meet all those requirements. This can be achieved with help of the following NCP1207 main features:
# Current−Mode Control: Cycle−by−cycle primary current observation is helping to prevent any significant primary overcurrent which would cause transformer’s core saturation and consequent serious power supply failure.
# Current−Mode Control: Cycle−by−cycle primary current observation is helping to prevent any significant primary overcurrent which would cause transformer’s core saturation and consequent serious power supply failure.
# Critical Mode Quasi−resonant Operation: Prevents the converter operation in Continuous Conduction Mode inany input and output condition. It is provided by the zero crossing detection of the auxiliary winding’s voltage.
# By addition of the reasonable delay the switch turn−on instant can be shifted to the minimum (valley) of drain voltage. This improves EMI noise and efficiency.
# Dynamic Self−Supply: Ensures IC proper operation in applications where the output voltage varies during operation like battery chargers. The DSS also supplies the IC when the overvoltage event is being latched and converter operation is stopped.
# Overvoltage Protection: By sampling the plateau voltage on the auxiliary winding, the NCP1207 enters into latched fault condition whenever the overvoltage is detected. The controller stays fully latched until the VCC decreases below 4.0 V, e.g. when the user unplugs the power supply from the mains outlet and re−plugs it. The OVP threshold can be adjusted externally.
# Over−Load Protection: by continuously monitoring the feedback loop activity, NCP1207 enters hiccup operation as soon as the power supply is overloaded. As soon as overload condition disappears, the NCP resumes operation.
NCP1396A Resonant Mode Controller
The NCP1396 A/B offers everything needed to build a reliable and rugged resonant mode power supply. Its unique architecture includes a 500 kHz Voltage Controlled Oscillator whose control mode brings flexibility when an ORing function is a necessity, e.g. in multiple feedback paths implementations. Thanks to its proprietary high--voltage technology, the controller welcomes a bootstrapped MOSFET driver for half--bridge applications accepting bulk voltages up to 600 V. Protections featuring various reaction times, e.g. immediate shutdown or timer--based event, brown--out, broken opto--coupler detection etc., contribute to a safer converter design, without engendering additional circuitry complexity. An adjustable deadtime also helps lowering the shoot--through current contribution as the switching frequency increases.
Applications
# Flat Panel Display Power Converters
# High Power AC/DC Adapters for Notebooks
# Industrial and Medical Power Sources
# Offline Battery Chargers
# Flat Panel Display Power Converters
# High Power AC/DC Adapters for Notebooks
# Industrial and Medical Power Sources
# Offline Battery Chargers
PIN COFIGURATION
1 CSS - Soft--start Select the soft--start duration
2 Fmax - Frequency clamp A resistor sets the maximum frequency excursion
3 Ctimer - Timer duration Sets the timer duration in presence of a fault
4 Rt - Timing resistor Connecting a resistor to this pin, sets the minimum oscillator frequency reached for VFB = 1 V
5 BO - Brown--Out Detects low input voltage conditions. When brought above Vlatch, it fully latches off the controller.
6 FB - Feedback Injecting current in this pin increases the oscillation frequency up to Fmax.
7 DT - Dead--time A simple resistor adjusts the dead--time width
8 Fast - Fault Quick fault detection Fast shut--down pin. Upon release, a clean startup
sequence occurs. Can be used for skip cycle purposes
9 Slow - Fault Slow fault detection When asserted, the timer starts to countdown and shuts down the controller at the end of its time duration.
10 GND - Analog ground --
11 Mlower - Low side output Drives the lower side MOSFET
12 VCC - Supplies the controller The controller accepts up to 20 V
13 -- -- --
14 HB - Half--bridge connection Connects to the half--bridge output
15 Mupper - High side output Drives the higher side MOSFET
16 Vboot - Bootstrap pin The floating VCC supply for the upper stage
2 Fmax - Frequency clamp A resistor sets the maximum frequency excursion
3 Ctimer - Timer duration Sets the timer duration in presence of a fault
4 Rt - Timing resistor Connecting a resistor to this pin, sets the minimum oscillator frequency reached for VFB = 1 V
5 BO - Brown--Out Detects low input voltage conditions. When brought above Vlatch, it fully latches off the controller.
6 FB - Feedback Injecting current in this pin increases the oscillation frequency up to Fmax.
7 DT - Dead--time A simple resistor adjusts the dead--time width
8 Fast - Fault Quick fault detection Fast shut--down pin. Upon release, a clean startup
sequence occurs. Can be used for skip cycle purposes
9 Slow - Fault Slow fault detection When asserted, the timer starts to countdown and shuts down the controller at the end of its time duration.
10 GND - Analog ground --
11 Mlower - Low side output Drives the lower side MOSFET
12 VCC - Supplies the controller The controller accepts up to 20 V
13 -- -- --
14 HB - Half--bridge connection Connects to the half--bridge output
15 Mupper - High side output Drives the higher side MOSFET
16 Vboot - Bootstrap pin The floating VCC supply for the upper stage
SG6961 PFC CONTROLLER
Description
The SG6961 is an 8-pin boundary mode PFC controller IC intended for controlling PFC pre regulators. The SG6961 provides a controlled on-time to regulate the output DC voltage and achieve natural power factor correction. The maximum on-time of the external switch is programmable to ensure safe operation during AC brownouts. An innovative multi-vector error amplifier is built in to provide rapid transient response and precise output voltage clamping. A built-in circuit disables the controller if the output feedback loop is opened. The startup current is lower than 20|JA and the operating current is under 4.5mA. The supply voltage can be up to 20V, maximizing application flexibility.
PIN CONFIGURATION
1 INV - lnverting Input of the Error Amplifier. INV is connected to the converter output via a resistive divider. This pin is also used for over-voltage clamping and open-loop feedback protection.
2 COMP - The Output of the Error Amplifier. To create a precise clamping protection, a compensation network between this pin and GND is suggested.
3 MOT - Maximum On Time. A resistor from MOT to GND is used to determine the maximum on-time of the external power MOSFET. The maximum output power of the converter is a function of the maximum on time.
4 CS - Current Sense. lnput to the over-current protection comparator. When the sensed voltage across the sense resistor reaches the internal threshold (O.8V), the switch is turned off to activate cycle-by-cycle current limiting.
5 ZCD - Zero Current Detection. This pin is connected to an auxiliary winding via a resistor to detect the zero crossing of the switch current. When the zero crossing is detected, a new switching cycle is started. If it is connected to GND, the device is disabled.
6 GND - Ground. The power ground and signal ground. Placing a O.1pF decoupling capacitor between VCC and GND is recommended.
7 GD - Driver Output. Totem-pole driver output to drive the external power MOSFET. The clamped gate output voltage is 16.5V.
8 VCC - Power Supply. Driver and control circuit supply voltage.
2 COMP - The Output of the Error Amplifier. To create a precise clamping protection, a compensation network between this pin and GND is suggested.
3 MOT - Maximum On Time. A resistor from MOT to GND is used to determine the maximum on-time of the external power MOSFET. The maximum output power of the converter is a function of the maximum on time.
4 CS - Current Sense. lnput to the over-current protection comparator. When the sensed voltage across the sense resistor reaches the internal threshold (O.8V), the switch is turned off to activate cycle-by-cycle current limiting.
5 ZCD - Zero Current Detection. This pin is connected to an auxiliary winding via a resistor to detect the zero crossing of the switch current. When the zero crossing is detected, a new switching cycle is started. If it is connected to GND, the device is disabled.
6 GND - Ground. The power ground and signal ground. Placing a O.1pF decoupling capacitor between VCC and GND is recommended.
7 GD - Driver Output. Totem-pole driver output to drive the external power MOSFET. The clamped gate output voltage is 16.5V.
8 VCC - Power Supply. Driver and control circuit supply voltage.
POWER SUPPLY SCHEMATIC DIGRAM
CLICK ON THE IMAGE TO ZOOM IN
Wednesday, June 15, 2016
LCD TV TCON BOARD Troubleshooting – T-con failure – LVDS cable failure - LCD panel failure – T-con replacement
Category: LCD Television Repair and Service
Contents of this article
- T-con Board failure
- LVDS cable failure
- LCD panel failure
LCD TV T-CON BOARD
DIAGNOSING A FAILED T-CON BOARD
All video inputs received by the video process circuits are handled on a frame-by-frame basis. The video frames are converted and scaled to 8 to 10 bit RGB information. It is virtually impossible for the video process circuit to cause a problem on a specific area of the screen. Failures on this board usually appear as distortions, color level shifts, video level shifts or noise that involves the entire picture. The T-Con can generate symptoms that appear to be video process related, but the video process circuit cannot produce the symptoms of a failed T-Con board circuit.
All video inputs received by the video process circuits are handled on a frame-by-frame basis. The video frames are converted and scaled to 8 to 10 bit RGB information. It is virtually impossible for the video process circuit to cause a problem on a specific area of the screen. Failures on this board usually appear as distortions, color level shifts, video level shifts or noise that involves the entire picture. The T-Con can generate symptoms that appear to be video process related, but the video process circuit cannot produce the symptoms of a failed T-Con board circuit.
T -CON FAILURES
Failures in the timing control circuits of the T-Con can produce symptoms of absolutely no video or generate lines and patterns that usually cover all or a substantial part of the screen. Determining if the T-Con is the cause of a ‘No Video’ condition is a bit more difficult since there are no indications on the screen to analyze. Many of the Sony TV models over the last few years will detect a T-Con that has completely failed. The communications data between the video process circuits and the T-Con will cease to communicate, if the T-Con fails completely. This will cause the TV to shut down and display a diagnostic code, indicating a failure of the T-Con. Not all chassis designs have this feature and it is not found on older models. The typical scenario when this failure arises is for the technician to bring a video process board to the repair location. It is usually safe to assume that the problem lies on the T-Con board, if the replacement video board dos not give a solution to the problem since it is highly unlikely that a replacement board with the same failure was received. One trick to check most T - Cons for functionality is to loosen the LVDS connector at the T-Con while unit is turned ON. Handle the LVDS connector with care and be certain to fully release the lock tabs. Gently rock the cable in and out of the connector while observing the screen for any response. Depending on the chassis, the symptoms of the screen ma be gentle white flashes, intermittent coloured lines, or a screen full of random patterns. The idea at this point is to provoke some kind of response on the screen. Another helpful procedure is to rapidly heat and/cool the T-Con with a hot air devices or circuit coolant and watch for patterns appear on the screen.
Failures in the timing control circuits of the T-Con can produce symptoms of absolutely no video or generate lines and patterns that usually cover all or a substantial part of the screen. Determining if the T-Con is the cause of a ‘No Video’ condition is a bit more difficult since there are no indications on the screen to analyze. Many of the Sony TV models over the last few years will detect a T-Con that has completely failed. The communications data between the video process circuits and the T-Con will cease to communicate, if the T-Con fails completely. This will cause the TV to shut down and display a diagnostic code, indicating a failure of the T-Con. Not all chassis designs have this feature and it is not found on older models. The typical scenario when this failure arises is for the technician to bring a video process board to the repair location. It is usually safe to assume that the problem lies on the T-Con board, if the replacement video board dos not give a solution to the problem since it is highly unlikely that a replacement board with the same failure was received. One trick to check most T - Cons for functionality is to loosen the LVDS connector at the T-Con while unit is turned ON. Handle the LVDS connector with care and be certain to fully release the lock tabs. Gently rock the cable in and out of the connector while observing the screen for any response. Depending on the chassis, the symptoms of the screen ma be gentle white flashes, intermittent coloured lines, or a screen full of random patterns. The idea at this point is to provoke some kind of response on the screen. Another helpful procedure is to rapidly heat and/cool the T-Con with a hot air devices or circuit coolant and watch for patterns appear on the screen.
LVDS cable failures
Although the problem with LVDS cable or connectors can generate symptoms of T-Con failures this usually tends to be intermittent and wiggling of the connectors will usually provoke a change in the symptom on the screen. LVDS cable and connectors have became rather robust over the past few years. Technicians who damage them cause most problems and this is generally quite oblivious upon close examination.
LCD panel failures
Some LCD panel failures could possibly mistaken for T-Con board issues. Other than damage to the LCD glass, most panel failures are isolated to a particular area of the screen. Since the T-Con disperses the pixel data to groups of line and column dirve IC’s situated on the outer edges of the panel, it is unlikely that more than one of these IC’s would fail at the same time. Multiple columns of struck on or stuck off pixels are therefore, more likely to be the fault of the T-Con circuits. The same applies to a single row of lit or unlit pixels. The T-Con simply cannot cut out a single line of information.
Although the problem with LVDS cable or connectors can generate symptoms of T-Con failures this usually tends to be intermittent and wiggling of the connectors will usually provoke a change in the symptom on the screen. LVDS cable and connectors have became rather robust over the past few years. Technicians who damage them cause most problems and this is generally quite oblivious upon close examination.
LCD panel failures
Some LCD panel failures could possibly mistaken for T-Con board issues. Other than damage to the LCD glass, most panel failures are isolated to a particular area of the screen. Since the T-Con disperses the pixel data to groups of line and column dirve IC’s situated on the outer edges of the panel, it is unlikely that more than one of these IC’s would fail at the same time. Multiple columns of struck on or stuck off pixels are therefore, more likely to be the fault of the T-Con circuits. The same applies to a single row of lit or unlit pixels. The T-Con simply cannot cut out a single line of information.
Burn in
Negative picture
T-CON REPLACEMENT
In many instances, replacement of the T-Con board will be relatively straight forward. In some case, the other boards may have to be loosened or removed to allow access to the mounting screws and clearance to remove the T-Con board. The issue of most concern is keeping track of the heat transfer pads, stand offs and insulators. The T-Con is heavily shielded and it si ease to have one or more of these components accidentally fall out of the assembly when removing. T-Con assemblies that use multiple heat transfer pads must be removed slowly and every attempt must be made to keep the shield and circuit board together as they are removed from the unit. Check for any service bulletins pertaining to the model and panel design that contain the subject lie of ‘T-Con heat transfer pad locations’ for pictures to show the proper location of these components. This site itself has covered disassembly procedure to some model LCD TVs, here. Pull up older posts here, or see the site in Time slide option, which can be accessed by the drop down at the top left side of the display window. It will make search the easily. Remove the screw from the LVDS cable ground strap so the cable can be moved away. Unplug the connector to inverter board and remove harness from the retainer. Remove all screws securing the board sub-chassis to the panel. Pull the top of the board toward you and downward to allow access to the bottom screws securing T-Con. The position of screws, and disassembly method may vary set to set. Carefully unpeel the conductive tape from the top bracket taking care not to tear them. Leave the tape attacked to the T-Con shield. Remove the top bracket covering the gate and source driver components. This will allow access to the upper flat cable connectors, if any. Carefully lift the locking tabs securing the flat cables. Leave the fat cables attached to the T-Con and shield assy. the T-Con board will have an insulating pad between it and the LCD panel that will cause the board to stick. Not much effort is required to release it. The goal at this point is to remove the board and shield together so as to avoid dropping heat transfer pads and insulators located between the front of the board and the shield. If successful, Both components should stay together as insulated. Note the spaces mounted on the backside of the board. These will need to be transferred to the replacement board. Lift the circuit board upward slowly while observing the location of the heat transfer and insulating pads. In most cases the heat transfer pad will remain attached to their appropriate ICs and the insulating pads will be struck to the shield. If anything falls off, use the instruction to return them to their proper position. Transfer all heat and insulating pads along with the flat cables to the replacement board. Once the components have been transferred to the front of the circuit board, attach the shield and flip the assembly. Transfer any spacers or insulating pads to the replacement bard. Temporarily secure the T-Con board to the shield with electrical tape. This helps in preventing movements of the circuit bard while installing the assembly back into the LCD panel. Once the T-Con ass’y is secured to the panel, insert and lock the flat cables. Plug in all connectors and secure the board sub chassis. Do not forget about the wire harness that was removed from its retainer.
In many instances, replacement of the T-Con board will be relatively straight forward. In some case, the other boards may have to be loosened or removed to allow access to the mounting screws and clearance to remove the T-Con board. The issue of most concern is keeping track of the heat transfer pads, stand offs and insulators. The T-Con is heavily shielded and it si ease to have one or more of these components accidentally fall out of the assembly when removing. T-Con assemblies that use multiple heat transfer pads must be removed slowly and every attempt must be made to keep the shield and circuit board together as they are removed from the unit. Check for any service bulletins pertaining to the model and panel design that contain the subject lie of ‘T-Con heat transfer pad locations’ for pictures to show the proper location of these components. This site itself has covered disassembly procedure to some model LCD TVs, here. Pull up older posts here, or see the site in Time slide option, which can be accessed by the drop down at the top left side of the display window. It will make search the easily. Remove the screw from the LVDS cable ground strap so the cable can be moved away. Unplug the connector to inverter board and remove harness from the retainer. Remove all screws securing the board sub-chassis to the panel. Pull the top of the board toward you and downward to allow access to the bottom screws securing T-Con. The position of screws, and disassembly method may vary set to set. Carefully unpeel the conductive tape from the top bracket taking care not to tear them. Leave the tape attacked to the T-Con shield. Remove the top bracket covering the gate and source driver components. This will allow access to the upper flat cable connectors, if any. Carefully lift the locking tabs securing the flat cables. Leave the fat cables attached to the T-Con and shield assy. the T-Con board will have an insulating pad between it and the LCD panel that will cause the board to stick. Not much effort is required to release it. The goal at this point is to remove the board and shield together so as to avoid dropping heat transfer pads and insulators located between the front of the board and the shield. If successful, Both components should stay together as insulated. Note the spaces mounted on the backside of the board. These will need to be transferred to the replacement board. Lift the circuit board upward slowly while observing the location of the heat transfer and insulating pads. In most cases the heat transfer pad will remain attached to their appropriate ICs and the insulating pads will be struck to the shield. If anything falls off, use the instruction to return them to their proper position. Transfer all heat and insulating pads along with the flat cables to the replacement board. Once the components have been transferred to the front of the circuit board, attach the shield and flip the assembly. Transfer any spacers or insulating pads to the replacement bard. Temporarily secure the T-Con board to the shield with electrical tape. This helps in preventing movements of the circuit bard while installing the assembly back into the LCD panel. Once the T-Con ass’y is secured to the panel, insert and lock the flat cables. Plug in all connectors and secure the board sub chassis. Do not forget about the wire harness that was removed from its retainer.
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