Thursday, January 21, 2016

PHILIPS 32HFL5382 - 37HFL5382 - 42HFL5382 - Power supply circuit diagram - l6599 - sg6961- LCD Television repair and service

Category: LCD Television Repair and Service 

Contents of this article

  • Power supply circuit digram 
  • L6599 Details 
  • SG6961 Details  

PHILIPS 32HFL5382 - 37HFL5382 - 42HFL5382

The L6599 is a double-ended controller specific for the resonant half-bridge topology. It provides 50 % complementary duty cycle: the high-side switch and the low-side switch are driven ON\OFF 180° out-of-phase for exactly the same time. Output voltage regulation is obtained by modulating the operating frequency. A fixed deadtime inserted between the turn-OFF of one switch and the turn-ON of the other one guarantees soft-switching and enables high-frequency operation.
To drive the high-side switch with the bootstrap approach, the IC incorporates a high-voltage floating structure able to withstand more than 600 V with a synchronous-driven high-voltage DMOS that replaces the external fast-recovery bootstrap diode. The IC enables the designer to set the operating frequency range of the converter by means of an externally programmable oscillator.
At start-up, to prevent uncontrolled inrush current, the switching frequency starts from a programmable maximum value and progressively decays until it reaches the steady-state value determined by the control loop. This frequency shift is non linear to minimize output voltage overshoots; its duration is programmable as well. The IC can be forced to enter a controlled burst-mode operation at light load, so as to keep converter's input consumption to a minimum. IC's functions include a not-latched active-low disable input with current hysteresis useful for power sequencing or for brownout protection, a current sense input for OCP with frequency shift and delayed shutdown with automatic restart. A higher level OCP latches off the IC if the first-level protection is not sufficient to control the primary current. Their combination offers complete protection against overload and short circuits. An additional latched disable input (DIS) allows easy implementation of OTP and/or OVP.
An interface with the PFC controller is provided that enables to switch off the pre-regulator during fault conditions, such as OCP shutdown and DIS high, or during burst-mode operation.
1 C SS
Soft start. This pin connects an external capacitor to GND and a resistor to RFmin (pin 4) that set both the maximum oscillator frequency and the time constant for the frequency shift that occurs as the chip starts up (soft-start). An internal switch discharges this capacitor every time the chip turns OFF (VCC < UVLO, LINE < 1.25 V or > 6 V, DIS > 1.85 V, ISEN > 1.5 V, DELAY > 3.5 V) to make sure it will be soft-started next, and when the voltage on the current sense pin (ISEN) exceeds 0.8V, as long as it stays above 0.75 V.
Delayed shutdown upon overcurrent. A capacitor and a resistor are connected from this pin to GND to set both the maximum duration of an overcurrent condition before the IC stops switching and the delay after which the IC restarts switching. Every time the voltage on the ISEN pin exceeds 0.8 V the capacitor is charged by an internal 150µA current generator and is slowly discharged by the external resistor. If the voltage on the pin reaches 2 V, the soft start capacitor is completely discharged so that the switching frequency is pushed to its maximum value and the 150 µA is kept always on. As the voltage on the pin exceeds 3.5 V the IC stops switching and the internal generator is turned OFF, so that the voltage on the pin will decay because of the external resistor. The IC will be soft-restarted as the voltage drops below 0.3V. In this way, under short circuit conditions, the converter will work intermittently with very low input average power.
3 CF
Timing capacitor. A capacitor connected from this pin to GND is charged and discharged by internal current generators programmed by the external network connected to pin 4 (RFmin) and determines the switching frequency of the converter.
4 RFmin
Minimum oscillator frequency setting. This pin provides a precise 2 V reference and a resistor connected from this pin to GND defines a current that is used to set the minimum oscillator frequency. To close the feedback loop that regulates the converter output voltage by modulating the oscillator frequency, the phototransistor of an optocoupler will be connected to this pin through a resistor. The value of this resistor will set the maximum operating frequency. An R-C series connected from this pin to GND sets frequency shift at start-up to prevent excessive energy inrush (soft-start).
Burst-mode operation threshold. The pin senses some voltage related to the feedback control, which is compared to an internal reference (1.25 V). If the voltage on the pin is lower than the reference, the IC enters an idle state and its quiescent current is reduced. The chip restarts switching as the voltage exceeds the reference by 50 mV. Soft-start is not invoked. This function realizes burst-mode operation when the load falls below a level that can be programmed by properly choosing the resistor connecting the optocoupler to pin RFmin (see block diagram). Tie the pin to RFmin if burst-mode is not used.
Current sense input. The pin senses the primary current though a sense resistor or a capacitive divider for lossless sensing. This input is not intended for a cycle-by-cycle control; hence the voltage signal must be filtered to get average current information. As the voltage exceeds a 0.8 V threshold (with 50 mV hysteresis), the soft-start capacitor connected to pin 1 is internally discharged: the frequency increases hence limiting the power throughput. Under output short circuit, this normally results in a nearly constant peak primary current. This condition is allowed for a maximum time set at pin 2. If the current keeps on building up despite this frequency increase, a second comparator referenced at 1.5 V latches the device off and brings its consumption almost to a “before start-up” level. The information is latched and it is necessary to recycle the supply voltage of the IC to enable it to restart: the latch is removed as the voltage on the Vcc pin goes below the UVLO threshold. Tie the pin to GND if the function is not used.
Line sensing input. The pin is to be connected to the high-voltage input bus with a resistor divider to perform either AC or DC (in systems with PFC) brownout protection. A voltage below 1.25 V shuts down (not latched) the IC, lowers its consumption and discharges the soft-start capacitor. IC’s operation is re-enabled (soft-started) as the voltage exceeds 1.25 V. The comparator is provided with current hysteresis: an internal 15 µA current generator is ON as long as the voltage applied at the pin is below 1.25 V and is OFF if this value is exceeded. Bypass the pin with a capacitor to GND to reduce noise pick-up. The voltage on the pin is top-limited by an internal zener. Activating the zener causes the IC to shut down (not latched). Bias the pin between 1.25 and 6 V if the function is not used.
Latched device shutdown. Internally the pin connects a comparator that, when the voltage on the pin exceeds 1.85 V, shuts the IC down and brings its consumption almost to a “before start-up” level. The information is latched and it is necessary to recycle the supply voltage of the IC to enable it to restart: the latch is removed as the voltage on the VCC pin goes below the UVLO threshold. Tie the pin to GND if the function is not used.
Open-drain ON/OFF control of PFC controller. This pin, normally open, is intended for stopping the PFC controller, for protection purpose or during burst-mode operation. It goes low when the IC is shut down by DIS > 1.85 V, ISEN > 1.5 V, LINE > 6 V and STBY < 1.25 V. The pin is pulled low also when the voltage on pin DELAY exceeds 2V and goes back open as the voltage falls below 0.3V. During UVLO, it is open. Leave the pin unconnected if not used.
10 GND
Chip ground. Current return for both the low-side gate-drive current and the bias current of the IC. All of the ground connections of the bias components should be tied to a track going to this pin and kept separate from any pulsed current return.
11 LVG
Low-side gate-drive output. The driver is capable of 0.3 A min. source and 0.8 A min. sink peak current to drive the lower MOSFET of the half-bridge leg. The pin is actively pulled to GND during UVLO.
12 VCC
Supply Voltage of both the signal part of the IC and the low-side gate driver. Sometimes a small bypass capacitor (0.1 µF typ.) to GND might be useful to get a clean bias voltage for the signal part of the IC.
13 N.C.
High-voltage spacer. The pin is not internally connected to isolate the high-voltage pin and ease compliance with safety regulations (creepage distance) on the PCB.
14 OUT
High-side gate-drive floating ground. Current return for the high-side gate-drive current. Layout carefully the connection of this pin to avoid too large spikes below ground.
15 HVG
High-side floating gate-drive output. The driver is capable of 0.3 A min. source and 0.8A min. sink peak current to drive the upper MOSFET of the half-bridge leg. A resistor internally connected to pin 14 (OUT) ensures that the pin is not floating during UVLO.
High-side gate-drive floating supply Voltage. The bootstrap capacitor connected between this pin and pin 14 (OUT) is fed by an internal synchronous bootstrap diode driven in-phase with the low-side gate-drive. This patented structure replaces the normally used external diode.
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 20JA and the operating current is under 4.5mA. The supply voltage can be up to 20V, maximizing application flexibility.
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.
37 AND 42 INCH