Samsung 127cm (50-inch) plasma screen V5 module power source block diagram shown in Figure l. 107cm (42 inch) V5 Samsung plasma screen compared to the power supply module, except VS driving circuits other than some major changes, other circuits had no change.

As can be seen in the following figure, Samsung 107cm (42-inch) plasma screen power supply and 127cm (50 inch) similar to the power supply. In addition to VS circuit driver part, only changed the numbering of individual components. Below is no longer introduced the principle machine, only with 107cm (42 inches) power--VS drive circuit work principle in different places.

Samsung 127cm (50-inch) plasma screen V5 VS driving part of the power supply voltage-type PWM (pulse width modulation) integrated circuit TL494 and quad NAND gate ICS 1W4093BN, simple structure, high reliability.


Star-127cm (50-inch) plasma screen V5 module power supply diagram

1. TL494 IC introduction

TL494 is United States Texas instruments produced by a voltage-type PWM devices with superior performance, can be used as single-ended type, push-pull, full bridge, half bridge switching mode power supply controller, is widely used in switching power supply, is the core of switching power supply control device. It can output a fixed frequency, pulse width adjustable rectangular pulses to control the conduction of the output tubes. Its internal circuit consists of: an oscillator (OSC), two players, two error amplifier, single trigger, two doors, two or not, and a 5V reference voltage regulator, two NPN-type power tubes. Chip oscillator can work in an active manner, can also work in a passive way.

Excitation output can work in push-pull mode, or you can work in single-ended output. Work in push-pull mode, its two drive pulse difference of 1800; at the time of single-ended output, driven by its two pulses for synchronization phase. It not only can produce a pulse, you can also control the MOSFET turn-on and cut-off. While addressing the current in a single chip control, PWM, and maximum current limit function. These characteristics, it has been widely used in the switching power supply.

2. TL494 pin function descriptions

① foot error amplifier with 1 input. Its input and output (internal error amplifier output consisting of 1 foot):

① foot input voltage rises, ③ pin voltage at the output of the comparator is also rising. The feet are often used as voltage regulators to control inputs.

② feet for the inverse of the error amplifier with 1 input. Generally used for reference voltage input.

H foot control amplifier and the public output of the error amplifier. Characteristics of output or output control when, in which two amplifiers, the output amplitude function: when the third leg when the level is high, TL494 sent the drive pulse width narrows when ⑧ feet when the level is low, driving pulse width become wider.

Black-leg dead-level control end. TL494 black-foot dead-time control voltage can be added to control the maximum width of the driving pulse, plus 0~3.3V of voltage can make deadline for linear changes from 2% to 100%. Set dead time, the deadline in the linear range, which protects the switch transistor in the power supply circuit.

⑤ ⑥ feet used for external vibration resistance and capacitance, respectively. Adjust the vibration resistance and capacitance parameters can change the oscillation frequency of the oscillation frequency is f=l/(Ct.Rt).

⑦ feet to the earth terminal.

⑧ Krispy Kreme and ⑩ feet, (11) foot TL494 respectively c and e of the two output transistors directly from within the IC leads, e or c output output can be made. Each set of transistors up to 200mA of output current.

(12) feet for the power supply.

(13) feet for function control. Internal reset control circuit Terminal, used to control the work of the two output States: when (13) feet grounded, Krispy Kreme feet and ⑩ foot output pulses of the same frequency, phase, when (13) feet 5V voltage, Krispy Kreme feet and ⑩ foot output pulse frequency, inverse.

(14) feet for the internal 5V reference voltage output.

(15), (16) feet respectively control the amplifier's inverting input end and the noninverting input.

When TL494 ⑩ feet after working voltage, 5V reference voltage, the internal oscillator begin to work (which can be changed and ⑥ ⑤ feet foot external resistors and capacitors to change the oscillation frequency). Output and PWM oscillator signal is sent to the dead-comparator comparator, isolated to the triggers, into mutually inverse pulse signal into the back of the amplifier. Because native (13) feet grounded, Krispy Kreme feet and ⑩ foot output pulse frequency and phase, so Krispy Kreme feet and ⑩ feet in circuit connected in parallel in order to increase the output current.
3. Introduction to four NAND Gates 1W4093BN

Isolation and complementary outputs vs some of the power MOS transistor, this machine uses the 1W4093BN four NAND gates. As we all know, NAND logic is: a and b are high level, the output is low; when the input a or b one of the lower level, the output is high. Four NAND gate IC 1W4093AN pin functions as shown in the table below.
PIN character function
1 a NAND gate input terminal a
2 b gate input terminal b
NAND gate outputs 3 j j
NAND gate outputs 4 k k
5 c gate input terminal c
6 d NAND gate input terminal d
7 Vss integrated circuit internal earth terminal
8 e gate input terminal e
9 f gate input f
NAND gate outputs 10 l l
NAND gate outputs 11 m m
12 g gate input terminal 6
13 h gate input terminal h
14 k IC internal supply



U8010 (TL494) Krispy Kreme, ⑩ foot output of the PWM signal into two paths; directly at U8011 (1W4093BN) (12) feet; the other by R8061 limited, after C8061 filters out high-frequency interference, adding h in U8011, (9) foot. Added U8011 (1W4093BN) ⑧ ⑨ foot PWM signal in U8011 within "and not" logical treatment, inverting the PWM signal is output from ⑩ feet, R8103 limited flow, add Q8017 (A1281) and Q8009 (C3209) b. Q8009 and Q8017 circuit in the complementary push-pull circuits, the e phase after the PWM output signal, the signal after it has been C8099 across the straight, add T8005 primary winding.

T8005 isolation voltage in the circuit.

Added U8011 (1W4093BN) (12) pin PWM signal via R8068 to C8056 charge and U8011 ⑩ feet. Dang PWM pulse for high electric usually, C8056 Shang filling have has high of voltage (R8068 of resistance and C8056 of capacity smaller), in U8011 internal implemented "and non-" logic processing Hou, from (11) feet output pour phase Hou of PWM signal, directly added in U8011 of ①, and II feet; again in internal implemented "and non-" logic processing Hou, from ⑧ feet output again pour phase of PWM signal, and (12) feet entered of PWM pulse with frequency, and with phase. Using two-level NAND gate to signal processing, mainly to deal with the clutter of signal and plastic in order to tie in with circuit after.

4.VS drive circuit work principle

Dang J8001 (timing control module) from (22) feet issued high level of VS open signal Hou, the voltage signal by R8405 limited flow Hou, added in photoelectric coupled device IC8008 (PC123) of ① feet, photoelectric coupled device internal of glow diode glow, internal of photosensitive transistor equivalent resistance reduced, U8027 (7818CT) output of 18V voltage, by R8036, and R8037, and photoelectric coupled device internal of photosensitive transistor to to, its points pressure Hou of voltage reduced, Q8014 b voltage drop, Q8014 breakover, Q8014 c 18V output voltage. The C8035 filter, and U8020 (7812CT) input, after a three-terminal regulator U8020 voltage regulator 12V voltage for the U8010 (TL494) and U8011 (1W4093BN) power supply.

U8010 of (12) feet get work voltage Hou, from Krispy Kreme, and ⑩ feet output PWM pulse into U8011 of ⑧, and Krispy Kreme, and (13) feet, in U8011 internal for "and non-" logic operation Hou, from U8010 ③ feet output of PWM and U8010 (12) feet entered of PWM pulse for with frequency, and with believes,, from U8010 ⑩ feet output of PWM signal and U8010 (12) feet entered of PWM pulse with frequency, and pour phase.

U8011 ③ feet after R8112 current, the output of PWM pulses, added by Q8019 (C3209), Q8020 (A1281) b on complementary push-pull circuit, Q8004 (W20NM50) entered the switching State.

Meanwhile, U8011 ⑩ foot phase after the PWM output signal applied to Q8009, Q8017, composed of complementary push-pull circuits on the b, push-pull output signals via the C8009 after isolation, added T8005 on the primary winding. T8005 pulse to the subprime-induced voltage D8014, R8120, Q8021 (A1281), C8091, R8121, R8043 added Q8003 (W20NM50) gate, Q8003 enters the switching State.

Q8021, C8091, D8014 start up delay conduction road, ensure the power on instant Q8003 in as to prevent Q8003 instant misleading and damaging power turning on Q8004 (see the following figure).

Start up delay turn-on circuit works as follows: power on instant, U8011 output signal may be in secondary T8005 "is being held under" induction pulse, D8014 conduction. Pulse R8120 gate added to Q8003. While, secondary winding bottom produced of negative pulse induction signal by C8091 added to Q8021 (PNP) of b very, due to capacitor ends of voltage cannot mutation, Q8021e very Shang of voltage through Q8021 of e-b very to C8091 charging, Q8021 guide pass, makes T8005 top induction of are pulse by D8014, and R8120, and R8121, and Q8021 returned to T8005 of secondary bottom, Q8003 of gate no charge and as. Because of the smaller C8091 capacity, charging will be over soon, Q8021 enters the closing state, does not affect the Q8003 gate charge, guarantees each of the VS operation Q8004 the pilot work.

(1) VS voltage power conversion circuit work principle

When the gate has a high Q8004 level, Q8004 pass, at this time, because contrary to gate level and gate level Q8004 Q8003, so Q8003 cutoff. 08029, T8001 VPFC voltage of the primary winding, L8012, Q8004, drain, Q8004-source, R8059, capacitor C8029 charging T8001 primary current from zero according to the slope of the linear increase in capacitor voltage of C8029 increases, induced electromotive force "was on the negative." Q8004 shutdown, when Q8003 was not, resonant capacitor C8029 and T8001 primary resonance body capacitance resonance currents generated by Q8003 back to the C8029 left, due to the capacitance is very small, this process will be over soon. Resonant current from the Q8003 source and Q8003 diodes continued to discharge Q8003 VPFC until the voltage of the source voltage gradually to Q8003. At this point, the Q8003 gate with zero voltage turn-on. VPFC voltage C8029 voltage Q8003 of the left end of the drain and source, L8012, T8001 primary back to the C8029 right, C8029 discharge, T8001 primary current from zero according to the slope of a linear increase, induced electromotive force "under the negative." Q8003 shutdown, when Q8004 was not, resonant capacitor C8029 and T8001 primary resonance, resonant current capacitance, as R8059, Q8004, L8012, T8001 voltage load of primary winding, C8029, and VPFC form a loop because the capacitance is very small, this process will be over soon. Resonant current through diodes form a loop of Q8004, Q8004 of the drain-source voltage and voltage is equal to. Q8004 Q8004 pass by the gate with zero voltage driving circuit enters the next cycle-driven State. Power part of the vs voltage forming circuit as shown in the following figure.

Vs voltage forming circuit



T8001 alternating current flowing through the primary winding, T8001 secondary will produce induction voltages, while D8015 induced voltage of the cathode is positive, D8015 pass, induction voltage via the D8015, C8050, C8049, vs voltage load back to D8016 cathode, at this time, D8016 D8016 anode voltage is lower than the cathode voltage cutoff.

So, load returns the secondary winding of the current C8046 back to T8001. When D8015 anode voltage is negative, secondary sensor pulses C8046, D8016 T8001 rectifier, forming a DC voltage in the secondary winding, D8015, C8049, C8050, filter rectifier formed voltage vs.

(2) VS voltage circuit voltage regulator circuit

D8015 vs voltage output via the R8233, R8234, R8235, R8236, VR8002, R8237, after the partial pressure, added to the precision voltage reference IC U8016 the REF side. Meanwhile, 5VSB voltage via the D8011, the C8112 separation filter, by R8111 and IC8012 (opto-coupler) ① feet, foot IC8012 ② U8016 anode. When vs when the load is light, and vs voltage, U8016 REF gets voltage increases, 2.5V of the voltage with an internal reference voltage, anode