Power Supply Unit P816, Description of P816 | Marantz DR-6000, MAR770, MAR775

8.2Power Supply Unit P816

8.2.1Description of P816

MOSFET Q825 is used as a power switch controlled by the controller Q810. When the switch is closed, energy is transferred from mains to the transformer. This energy is supplied to the load when the switch is opened. Through control of the switch-on time, the energy transferred in each

cycle is regulated so that the output voltages are independent of load or input voltage variations. The controlling device MC44603 is an integrated pulse width modulator. A clock signal initiates power pulses at a fixed frequency. The termination of each output pulse occurs when a feedback signal of the inductor current reaches a threshold set by the error signal. In this way the error signal actually controls the peak inductor current on cycle-by-cycle basis.

SWITCHING POWER SUPPLY PCB. (P801)

L831

D802

S1WB

D806

L825

C819

C825

G815

C820

R819

0.1

470pF

250V

/400V

Q825

C827

J801

0.01

0.22

330k

250V

(UL/CSA,MITI)

C826

2SK2943

470pF

1M(CB)

/1kV

F820

470pF

C821

D807

L820

/400V

D803

120

R825

S815

J820

J821

/400V

2A_125V(F&U )

D804

2A_250V(N&K)

C828

R826

R827

R828

470pF

R823

J828

/400V

1.5

18k

R832

18k

R829

D832

10k

AG01

L832

C829

4.7/50V

D829 24V

C833

100/25V

R811

R801

Q810

R810

10k

82k

C801

MC44603P

VREF IREF

C811 0.1

82pF

DEMAGINETIZATION

NP0

DETECT

DEMAGNETISATION

REFERENCE

SUUPLY

UVL01

MANAGEMENT

BLOCK

INITIZLIZATION

BLOCK

SYNC

REFI

C802

820pF

OSCILLATOR

R812

100

R802

LATCH

R813

22k

STANDBY

BUFFER

R803

STANDBY

Q801

4.7k

STANDBY

C813

(REDUCED FREQUENCY)

PC123F

2200pF

C803

VSB

THERMAL

VREF

VOC

470p

2.5V

SHUTDOWN

ERROR

OUT

OVER

D836

D835

AMP

VOLTAGE

IREF

VOLTAGE

PROTECT

R805

R804

C804

VOLTAGE

MANAGEMENT

D814

15k

4700pF

FEEDBACK

R814

DMAX&

AG01

UVL01

1.8k

E/A OUT

SOFT-START

R815

CONTROL

1.8k

FOLDBACK

VREF

R816

180

C814

FOLDBACK

CURRENT

SOFTSTART

0.1

INPUT

SENSEINPUT

&DMAX

R806

R808

R807

C809

R809

C810

18k

180k

330

1500p

2.2/50V

Q851

LM317

L854

L831

10µH

D851

L853

4.7µH

C892

Q892

AG01

R853

100/25

PC123F

R852

C854

C855

C851

220

0.1

100/6.3V

0.1

C852

L851

R851

R894

330

560

4.7µH

L852

/16V

J851

+4.1V

L856

C860

C859

6.8µH

(OPTION)

-34V

0.1

D856

C856

C857

GND

2200

RK46

/10V

+5V

R861

+5V

10k

GND

L862

GND

10µH

D861

R862

GND

L861

D862

C864

+12V

1µH

AG01

Q861

220/50V

-8V

2SC

R863

C862

Q862

C861

2SA

10k

R865

10/50V

10k

+12V

R864

C869

D866

10k

L867

D868

220

RU4YX

2.2µH

/16V

C866

L866

C867

Q871

R866

C868

0.1

1000

7908

D871

/16V

AG01

L871

L872

C877

C875

C871

C872

10µH

0.1

100

0.1

C873

R881

R882

/16V

220

/16V

220

3.3k

100

/16V

L873

C876

C882

R883

0.022

1.8k

R887

D881

C881

100

TL431

R884

/25V

2.21k

J891

R885

681

C898

R886

0.1

+12V

R892

R893

22k

10k

Q891

R891

2SC2878

22k

C891

100/25

Figure 8-10 ‘Blockdiagram P816’

Description of controller MC44603

The MC44603 is an enhanced high performance controller that is specifically designed for off-line and DC-to-DC converter applications. This device has the unique ability of automatically changing operating modes if the converter output is overloaded, unloaded or shorted. The MC44603 has several distinguishing features when compared to conventional SMPS controllers. These features consist of a foldback facility for overload protection, a standby mode when the converter output is slightly loaded, a demagnetization detection for reduced switching stresses on transistor and diodes, and a high current totem pole output ideally suited for driving a power MOSFET. It can also be used for driving a bipolar transistor in low power converters. It is optimised to operate in discontinuous mode but can also operate in continuous mode. Its advanced design allows use in current mode or voltage mode control applications.