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.
#
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
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.
POWER SUPPLY SCHEMATIC DIAGRAM
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