Category: LCD Television Repair and service
Contents of this article
- Power supply schematic diagram
- FAN 7930 Pin configuration
- L6599 Pin configuration
SANYO 55CE590A1
FAN7930
Description
The FAN7930 is an active power factor correction (PFC) controller
for boost PFC applications that operate in critical conduction mode (CRM). It
uses a voltage-mode PWM that compares an internal ramp signal with the error
amplifier output to generate a MOSFET turn-off signal. Because the voltage-mode
CRM PFC controller does not need rectified AC line voltage information, it saves
the power loss of an input voltage sensing network necessary for a current-mode
CRM PFC controller. FAN793O provides over-voltage protection, open- feedback
protection, over-current protection, input- voltage-absent detection, and
under-voltage lockout protection. The PFC-ready pin can be used to trigger other
power stages when PFC output voltage reaches the proper level with hysteresis.
The FAN7930 can be disabled if the INV pin voltage is lower than O.45\/ and the
operating current decreases to a very low level. Using a new variable on-time
control method, THD is lower than the conventional CRM boost PFC ICs.
PIN
CONFIGURATION
1
INV
This pin is the inverting input of the error amplifier.
The output voltage of the boost PFC converter should be resistively divided to
2.5V.
2
RDY
This pin is used to detect PFC output voltage reaching a
pre-determined value. When output voltage reaches 89% of rated output voltage,
this pin is pulled HIGH, which is an (open drain) output type.
3
COMP
This pin is the output of the transconductance error
amplifier. Components for the output voltage compensation should be connected
between this pin and GND.
4 CS
This pin is the input of the over-current protection
comparator. The MOSFET current is sensed using a sensing resistor and the
resulting voltage is applied to this pin. An internal RC filter is included to
filter switching noise.
5
ZCD
This pin is the input of the zero-current detection
block. If the voltage of this pin goes higher than 1.5V, then goes lower than
1.4V, the MOSFET is turned on.
6
GND
This pin is used for the ground potential of all the
pins. For proper operation, the signal ground and the power ground should be
separated.
7
OUT
This pin is the gate drive output. The peak sourcing and
sinking current levels are +500mA and - 800mA, respectively. For proper
operation, the stray inductance in the gate driving path must be minimized.
8
Vcc
This is the IC supply pin. IC current and MOSFET drive
current are supplied using this pin.
L6599
Description
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.
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.
PIN CONFIGURATION
1 Css
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.
2 DELAY
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.
1 Css
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.
2 DELAY
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).
5 STBY
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.
6 ISEN
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.
7 LINE
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.
8 DIS
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.
9 PFC_STOP
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.
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).
5 STBY
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.
6 ISEN
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.
7 LINE
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.
8 DIS
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.
9 PFC_STOP
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.
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.
16 VBOOT
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.
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.
16 VBOOT
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.
POWER SUPPLY BOARD SCHEMATIC DIAGRAM
CLICK ON THE IMAGES TO ZOOM IN
