Samsung DVD-905, Service Manual

Page: 25 / 136

Reference Information
2-6 Samsung Electronics
4. PIC1 function : PWM control (Refer to Switch ON/OFF Control of Fig. 2-6)
- 0.56V
- -
OFF voltage 0.75V
SHUT OFF voltage 2.8V
DUTY MAX voltage 2.3V
LIMIT voltage 0.24V
- -
- -
Maximum DUTY 70%
ON voltage 16V
OFF voltage 8.7V
- -
OFF voltage 0.42V
ON voltage 0.56V
3.6V
SHUT OFF voltage 7V
MAX DUTY voltage 2.3V
1 RT
2 F/B
3 IS
4 GND
5 OUT
6 VCC
7 CT
8 CS
PIN NAME CLASS SPEC. FEATURES
* Resistance to determine OUT terminal(pin5) ON/OFF control frequency
- Determined with CT terminal(pin7) and for DVDP, 50KHz
RT : PR24, CT : PC13
* OUT terminal duty is determined by F/B potential
(Duty control : 2st output constant-voltage control)
* The voltage of PIC2(Output voltage freedback) is input to F/B terminal.
* If F/B terminal potential decreases below 0.75V, OUT duty is zero.
- SMPS 2st output voltage is zero.
* If F/B potential is above 2.8V, CS terminal(8pin) potential ascends in IC.
If CS potential rises above 7V, SHUT OFF mode is maintained.
* SHUT OFF mode : IC internal bias OFF state.(Operation stop)
* If IS terminal potential is above 0.24V, maintain on time only when IS
terminal potential is 0.24V without holding OUT duty determined in F/B
terminal(Duty limit).
* PQ1(F,E,T) current is distributed to PR22, PR21 in voltage, and input to IS
terminal.
* Purpose : Limit the overcurrent of PQ1(Current waveform : See Fig. 2-10)
* Ground(SMPS 1st ground)
* ON/OFF control pulse output terminal(f : fixed, ON TIME : variable)
* Maximum duty is 70% (Maximum).
* IC power supply terminal. IC function starts at exceeding 16V. Vcc less than
8.7V will be OFF after IC working.(See Clause 3. Vcc circuit)
- Vcc voltage is 10-12V at normal operation.
* ON/OFF frequency determining terminal(Refer to 1 pin RT terminal)
* OS potential setting : Connect the condenser to OS terminal(PC14)
* ON/OFF control : If CS potential is above 0.56V, IC function starts and if
below 0.42V, IC function stops.
* At normal operation : Maintain 3.6V in IC
* SHUT OFF mode : If CS potential is above 7V, shut off.(Overload
prevention)
- SHUT OFF function : When IS, F/B, CS terminal are all operated normally.
(Refer to Clause 6. MAX. POWER limiting circuit)
* SOFT START : Switch protection at initial starting
- F/B potential is 3.6V internally at initial starting.(Duty max.)
- PQ1 damage occurs due to overcurrent on switch at duty max.
- CS terminal sets the duty with F/B terminal
- Connect PC14 to CS terminal and set the voltage charging time at initial
starting.
- Increase the duty by raising the voltage gradually via PC14 at initial starting
for normal operation.
(Duty max. is limited by F/B potential at initial starting)
Normal operation
voltage