Sanyo VPC-E7 Service Manual

Contents

– 7 –1-3. PWA POWER CIRCUIT DESCRIPTION1. OutlineThis is the main power circuit, and is comprised of the follow-ing blocks.Switching power control IC (IC501)Analog 13 V (A) output system (L5003, Q5001)Analog -7.5 V (A) output system (L5005, Q5005, IC502)Analog 3.5 V (A) output system (IC503)Digital 3.25 V (D) output system (L5001)Digital 1.20 V (D) output system (L5002)Backlight output system (L5006, Q5007)Boost power (L5301)2. Switching Power Controller (IC501)This is the basic circuit which is necessary for controlling thepower supply for a PWM-type switching regulator, and is pro-vided with eight built-in channels.PWM/PFM switching step-up circuit …… 1 (ch_1)PWM drive step-up/step-down circuit …… 1 (ch_2)PWM drive step-up and step-down circuit …… total 4 (ch_3and ch_5~ch_7)PWM drive inverter circuit …… 1 (ch_4)Variable regulator …… 1 (ch_8)Only ch_1 (starting IC, lens drive, 8-bit microprocessor andch_3 source), ch_2 (digital 3.25 V), ch_3 (digital 1.20 V), ch_4(analog -7.5 V), ch_5 (analog 13 V), ch_6 (not used), ch_7(backlight) and ch_8 (not used) are used. Feedback from 3.8V (ch_1), 3.25 V (ch_2), 1.20 V (ch_3), -7.5 V (ch_4) and 13.0V (ch_5) power supply outputs are received, and the PWMduty is varied so that each one is maintained at the correctvoltage setting level.Feedback for the backlight power (ch_7) is provided so thatregular current can be controlled to be current (approximately20 mA) that was setting.PWM/PFM switching can be carried out for ch_1, so that PFMoperation is enabled when the DSC is stopped (when thepower is off) which provides greater efficiency at times of lowloads (only the 8-bit microprocessor is driven).2-1. Damage Prevention CircuitWhen a short-circuit is generated for a constant period of time,the capacitor that is connected to pin (1) of IC501 turns alloutput off. It is also equipped with an overheating protectioncircuit, so that when the element temperature becomes higherthan a certain temperature, all output is turned off in the sameway as for a short-circuit. To reset output, remove the causeof the problem and then resend a control signal.3. ch_1 Output System3.6 V is output. Feedback for the 3.8 V output is provided tothe switching controller (Pin (36) of IC501) so that PWM con-trol can be carried out. Also, it is the source for 3.5 V (A).While DSC is stopped, control switches to PFM control.4. ch_2 Output System3.25 V (D) is output. Feedback for the 3.25 V (D) output isprovided to the switching controller (Pin (45) of IC501) so thatPWM control can be carried out.5. ch_3 Output System1.20 V (D) is output. Feedback for the 1.20 V (D) output isprovided to the swiching controller (Pin (44) of IC501) so thatPWM control can be carried out.6. ch_4 Output System-7.5 V is output. Feedback for the inverter circuit output isprovided to the switching power controller (Pin (38) of IC501)so that PWM control can be carried out. This output is highprecision by IC503, and get to -7.5 V.7. ch_5 Output System13.0 V (A) is output. Feedback for the 13.0 V (A) is providedto the switching power controller (Pin (39) of IC501) so thatPWM control can be carried out.8. ch_7 Output SystemRegular current is being transmitted to LED for backlight. Step-down in the voltage from the LED are feedback to the switch-ing power controller (Pin (42) of IC501) so that PWM controlcan be carried out.The control signal (LCD PWM) from the 8-bit system can beused to adjust the backlight illumination.