Samsung PS50P2HTX Circuit Descriptions

Circuit Operation Description

Samsung Electronics 5-1

5. Circuit Description

5-1 Power supply

5-1-1 Outline(PDP SMPS)

Considering various related conditions, the switching regulator with good efficiency and allowing for its small size and light weight was used as the power supply for PDP 50inch, VS requiring high power consumption used forward converter and 12VSAMP used the simple flyback converter and other high voltage (VSCAN,VSET,VE)used DC/DC converter. To comply with the international harmonics standards and improve the power factor, active PFC(Power Factor Correction) was used to rectify AC input into +400V DC output, which in turns used as input to the switching regulator.

5-1-2 50" SMPS Specification

5-1-2(A) INPUT

The power supply shall be capable of supplying full rated output power over free voltage ranges that are rated 100 VAC - 240 VAC RMS nominal. Operating voltage : 90 VAC - 264 VAC. The power supply must be able to start up under peak loading at 90V AC. The power supply shall automatically recover from AC power loss. (Note that nominal voltages for test purposes are considered to be with +/- 1.0V of nominal). +5VSB is a SELV standby voltage that is always present when AC mains voltage present.

5-1-2(B) OUTPUT

This power supply is 13output switching power supply for PDP 50inch. The output voltage, and current requirements for continuous operation are stated below. (Table1.)

Table1. Specifications of Output Power Supplies for PDP SMPS

Output Name

Vsustain

Vaddress

Vscan

Vset

Vfan

V5(D)

Vsb

V12

Vsamp

Output Voltage

+165V ~ 200V(165V)

+58V ~ 73V(65V)

+60V ~ 78V(70V)

+195V ~ 230V(215V)

+180V ~ 210V(185V)

+1V ~ 20V(18.4V)

+10V ~ 12V(11V)

+1V ~ 10V(9.0V)

+1V ~ 8V(6.0V)

+5.1V ~ 5.9V(5.4V)

+4.8V ~ 5.4V(5.2V)

+10V ~ 12V(11V)

+10V ~ 13V(12V)

Output Current

1.8A

0.5A

0.05A

0.3A

0.8A

0.3A

1.0A

3.5A

0.4A

1.2A

1.5A

Using in PDP driving

Sustain Voltage of Drive Board

Address Voltage of Drive Board

Driving Voltage of Fet

Driving Voltage of Fan

IC Driving Voltage of Logic Board

Stand-by for Remote Control

AMP Voltage of Audio Board

Circuit Operation Description

5-2 Samsung Electronics

Table 2. Over voltage Protection.

5-1-2(C) Over voltage Protection

The over voltage sense circuitry and reference shall reside in package that are separate and distinct from the regulator control circuitry and reference. No single point fault shall be able to cause a sustained over voltage condition on any of all outputs. The supply shall provide latch-mode Over Voltage Protection as defined below. (Table2.)

Table 3. Over Current Protection.

Parameter

VS(169V)

VA(65V)

5V(D)

Min

3.0 ~

2.0 ~

10 ~

Unit

Parameter

VS(169V)

VA(65V)

5V(D)

Min

195 ~

90 ~

5.5 ~

Unit

5-1-2(D) Short Circuit and Over current Protection.

An output short circuit is defined as output impedance of less than 300mohms. The power supply shall shutdown and latch off for shorting VS DC rails to return or any other rail. Shorts between main output rails and 5VSB shall not cause any damages to the power supply. The power supply shall either shutdown and latch off for shorting is removed, the P/S shall recover. The power supply shall be capable of withstanding a continuous shot-circuit to the output without damage or over stress to the unit (components, PCB traces, connectors,etc.) under the input conditions specified in Section2 above. Current Protection as defined below. (Table3.)

5-1-2(E) Function of Board

① REMOTE CONTROL

Using a 250V/10A relay, the board makes remote control available.

➁ FREE VOLTAGE

The board is designed so that the input voltage can be used within 90VAC to 264VAC.

➂ Improvement of power factor

The board is designed using the active PFC circuit so that the Power Factor can be over 9.0.

➃ Protection

The OCP(Over current Protection), OVP(Over voltage Protection), Short Circuit Protection functions are added against system malfunction.

Circuit Operation Description

Samsung Electronics 5-3

5-1-2(F) Part Block Diagram and Part Function.

(1) AC-DC Converter

The Power supply output +400V DC from the common AC power supply using the active PFC booster converter. This converter is designed for improving the power factor and preventing the noise with high frequency and finally becomes the input power system for the switching regulator on the output side.

Picture1. PFC Drive FET(2SK2372) Drain pulse

Circuit Operation Description

5-4 Samsung Electronics

- Oscillator Frequency Oscillator Frequency is determined by the values of Rt and Ct, which determine the ramp and off-time of the oscillator output clock Oscillator Frequency is derived from the following equation

For the circuit shown in the PDP50, with the oscillator running at

Picture2. PFC Drive FET(2SK2372) Gate pulse

Circuit Operation Description

Samsung Electronics 5-5

(2) AC-DC Converter

Auxiliary Power Supply The auxiliary power supply is a block generated power of micom for remote controlling. Once the power plug is inserted, this block always comes into operation, causing micom to get into the standby state for the output. Thus, this output is called the standby voltage. And with the relay ON signal inputted through the remote controller, this block turns the mechanical switch of relay to ON for driving the main power supply.

Picture3. Standby flyback Pulse.

Circuit Operation Description

5-6 Samsung Electronics

(3) Implementation of Sustain Voltage

As the main part of a SMPS for PDP, sustain voltage must supply a high power, 180V/1.8A. To comply with the specification, the forward method was basically used. At the output stage two 90V converters are connected serially for high efficiency and reduction of system size against a single 180V converter.

Picture4. VS Driving FET(2SK2968) drain pulse.

Picture5. VS Driving FET(2SK2968) gate pulse.

Circuit Operation Description

Samsung Electronics 5-7

❏ PWM SECTION ( Pulse Width Modulator )

PDP SMPS use PWM IC ( KA3844 ) in PWM section. KA3844 is fixed frequency current-mode PWM controller. They are specially designed for Off-Line and DC-to-DC converter applications with minimum external components. These integrated circuits featurea trimmed oscillator for precise dutycycle control, a temperature compensated reference, high gain error amplifier. Current sensing comparator, and a high current totempole output Ideally suited for driving a power MOSFET. Protection circuity Includes built in under -voltage lockout and current limiting. This IC can operate with 50% duty cycle.

Picture6. KA3844 Oscillating Frequency pulse.

Oscillator timing capacitor (Ct) is charged by Vref through Rt and discharged by an internal current source. During the discharge time, the internal clock signal blanks the output to the low state. Selection of Rt and Ct therefore determines both oscillator frequency and maximum duty cycle. Charge and discharge times are determined by the formula.

Circuit Operation Description

5-8 Samsung Electronics

(4) DC-DC Converter

Input of VSCAN, VSET, VE is Sustain Voltage. This circuit use MA2820. Maximum output wattage of MA2820 is 60W.

Picture7. MA series Block Diagram

Picture8. MA2820 main pulse.

Circuit Operation Description

Samsung Electronics 5-9

(5) Output (VA,5V,12VSAMP) Pulse

Picture9. VA main pulse.

Picture10. 5V main pulse.

Circuit Operation Description

5-10 Samsung Electronics

Picture11. 12VSAMP main pulse.

Circuit Operation Description

Samsung Electronics 5-11

5-1-3 Block Diagram

Picture9. VA main pulse.

Circuit Operation Description

5-12 Samsung Electronics

5-1-4 Connector Pin Assignment

OUTPUT

+5.3V

SYM

VSB

User specification

RELAY

(INPUT)

5V/0.3A

MAX

User specification

OUTPUT

+5.3V

GND

+18.3V

GND

80V

GND

205V

N.C

GND

163V

SYM

Vcc

Vdd

Vscan

Vset

OUTPUT

+5.3V

GND

+18.3V

GND

190V

GND

80V

GND

163V

SYM

Vcc

Vdd

Vscan

OUTPUT

+6.0V

GND(A)

+9V

+12V

GND(A)

+12V

GND(AMP)

SYM

+6V(A)

V12

VSAMP

OUTPUT

+5.3V

GND(D)

+5.3V

GND(D)

SYM

Vcc

SA(Image Board) SY(Drive) SX(Drive)

Speaker SL(Logic)

OUTPUT

SYM

OUTPUT

+12V

GND

SYM

VFAN

AC(INPUT) FAN(4EA)

OUTPUT

+70V

GND

SYM

BUFFER

FAN SIGNAL

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