Philips DVD763SA/021 Alignments, Circuit Descriptions and List of Abbreviations, Introduction

Alignments DVD763SA 8. EN 67

8. Alignments

Not applicable.

9. Circuit Descriptions and List of Abbreviations

Index of this chapter:

1.Introduction

2.Power Supply Unit (PSU).

3.Loader/Mono Board.

4.Audio Video (A/V) Board.

5.Front Display Board.

6.Abbreviations

7.IC Data

Notes:

•See also the SD4.0 SA_CH Service Manual (3122 785 12480).

•Figures can deviate slightly from the actual situation, due to different set executions.

•For a good understanding of the following circuit descriptions, please use the diagrams in chapter 6 and 7. Where necessary, you will find a separate drawing for clarification.

9.1Introduction

The DVD763SA is a model from the SACD 2002 'single disc' range. It uses a 2nd generation Philips SACD mono board, based on the Furore 2 DSD/DST decoder.

Below you will find a circuit description of the several modules.

9.2Power Supply Unit

9.2.1Introduction

This supply is a Switching Mode Power Supply (SMPS), which uses the control IC TY720xx to produce pulses to drive the power ‘switch’ (MOSFET). The TY720xx (IC7130) is a high performance, current mode controller for DC-to-DC converter applications.

The operation frequency varies with the circuit load. When the output power demand decreases, the switching frequency raises, with a maximum frequency of 125 kHz (defined by C2130 at pin 5). At this point, the internal VCO takes over and starts to decrease the switching frequency.

This has some benefits compared to a ‘fixed frequency’ flyback converter. The efficiency is better, which results in a lower power consumption.

9.2.2Output Voltages

The following output voltages are present on connector 0201:

•Pin 1 and 2: +3V3_POWER.

•Pin 4: +12V_POWER

•Pin 5: +12STBY.

•Pin 7: +5VSTBY.

•Pin 9: -12V_POWER.

•Pin 11: -32V_POWER.

Note: The suffix 'STBY' indicates that the supply is not switched 'off' during Standby Mode. Power switching is done with the STBY_CTRL signal from the slave processor.

9.2.3Operation

	EMI-FILTER	RECTIFIER			T1
		AC			300V
					+12V
MAINS	DM1				C5
			DC		etc
	CM1				Q1
		IC1
					D
		1		12	G
					S
		5		11
		4	13		RSENSE1
					C7
					+12V
					IC2
					IC3
					RSENSE2
					CL 26532053_024.eps
					010502

Figure 9-1 Power Supply

Mains Input Circuit

The bridge rectifier D6110 rectifies the mains voltage, after which C5 (2117) smoothens it. The DC voltage across this capacitor is the DC input voltage (approximately 300V), to pin 1 of transformer T1 (pin 9 of 5190) and pin 1 of IC1 (7130). The mains input also consists of a (differential mode) lightning protection DM1 (R3110) and a (common mode) lightning protection CM1 (D6114/15).

Start-up Circuitry

The rectified voltage from the bridge rectifier is connected to pin 1 of IC1. This voltage will charge the Vcc capacitor C7 (C2131). When this voltage, (at pin 13), reaches the start-up threshold of min. 15V, the control circuit starts to operate. After start-up, the control IC requires a sinking current, which the start-up circuitry cannot deliver. Therefore a take-over circuitry (a coupled winding of transformer T1) is present. The voltage at this point will take over the supply voltage at pin 13 of the IC1(7130).

If the take-over circuit does not function, IC1 (7130) will switch 'off' again at the minimal operating voltage of +8V. The whole operation cycle will repeat itself with audible hiccup sound if take-over is not present.

Secondary Voltage Sensing

The secondary voltage regulating circuit comprises of opto- coupler IC2 (7190), which isolates the error signal from the control IC on the primary side, and a reference component IC3 (7290, TL431).