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KDrservice manual download site
KDrservice manual download site
Second, when the power switch tube by conduction into time to electrical energy stored in the transformer load release, at this point, the transformer secondary coil end of S1 and S2 terminal is negative, positive on both ends of rectifier tube D891, D892, rectifier conduction, to C865 C864 charging. Get the standby voltage of 18.5 V. The voltage is divided into three way: the first to add all the way to the voltage sampling circuit for voltage stability. The first 2 added to DC - DC conversion circuit IC852 1 foot, to convert the power supply voltage of 18.5 V to 7 V SBT7V standby voltage. Sent to A board CPU circuit. The third way to switch tube Q843 S pole, G are extremely open voltage control from the CPU, from D output controlled 18.5 V power supply, add to A board audio power amplifier circuit. KDrservice manual download site
KDrservice manual download site
Three, T880 V1 -v2 coil, coil is feedback, V2 end grounding, V1 termination D870 rectifier, C848 filter, get 20 v voltage, add to IC851 VCC terminal 3 feet. Inside the IC, VCC to VDD power supply of 5 feet, at the same time cut off for VDD power supply IC within 7 feet. The pulse voltage at the V1, but also through R850, add to the IC 2 feet, the oscillation circuit inside the trigger and the synchronous IC, to drive the switch tube conduction and deadline. R850, R851, C868 role is to ensure that when T880 internal power to the load when the release, to trigger the switch tube conduction into the next cycle, called a quasi resonant circuit. This can make the switch tube conduction loss minimum. KDrservice manual download site
KDrservice manual download site
Four sampling and voltage control circuit, error: T880 secondary rectifier output voltage of 18.5 V, added to the first branch voltage sampling circuit, series resistance R879, R877, R892, R897 sampling circuit of pressure. In R892 top share of voltage, added to the input end of the error amplifier IC890 REF, normal voltage should be 2.48 V, the foot IC890 conduction, produces the following current: 18.5 V voltage of the positive -- -- -- -- -- -- -- R880 -- -- -- -- -- -- -- -- light coupling PC880 luminous tube in the -- -- -- -- -- -- -- -- IC890 K end -- -- -- -- -- -- -- -- -- -- -- -- A side to the ground. The current make the light inside the light coupling tube light, when 18.5 V voltage rise, IC890 input voltage of year-on-year rise, also led to the current increase, light coupling inner glow tube light stronger, photosensitive resistance decreases, through R852 will make IC851:1 foot voltage drop, which will bring down the switch tube conduction width, T880 less storage, eventually make 18.5 V voltage stable. Here, it is necessary to say once Q883 role: P plate P3 platooninsert 13 feet, came from A board within the CPU output power on command SUBON, when switched on, the foot of the voltage of 2.25 V, the R896 to Q883 B, the tube conduction, the R897 short circuit, so that the pressure drop, at the top of R892 IC890 current flow is small, light coupling inner glow tube light dimmed, photosensitive cell internal resistance, make IC851:1 feet higher voltage, switch tube conduction widen and the standby voltage output value is 18.5 V voltage. And when from A plate when the CPU SUBON is low level 0 v, Q883 cut-off, R897 will no longer be short circuit, this will make the top R892 partial pressure increases, IC890 current flow is big, make the output of standby voltage drop to 10 v.
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