Principle of high static current of lifting lamp

Time：2021-02-19 View：

High static current
Static current can be divided into two situations: one is that the current is over 1.00A, and the other is around 0.15A. What are the differences and solutions between the two:
The first is a SHORT circuit with an applied voltage of 19V, resulting in a large static current. In this case, disconnect the applied voltage (unplug the power supply) within a limited time, otherwise it will burn many related parts. Remember. The handling of this situation is simpler. Why do you say that there is a handling skill to disconnect the applied voltage within a limited time, when the applied voltage is not disconnected, you should quickly touch the parts on the whole motherboard with your hands (without knowing the load of 19v applied voltage on the motherboard, that is, 19V), see if you can feel any parts are very hot. Generally, that part is broken.

Principle of high static current
Here we introduce its principle: this is judged according to the simple principle of parallel circuit. The two resistances are connected in parallel without changing the applied voltage, if the current of the branch with a small resistance is larger than that of the other branch, then the heat generated by this branch is much larger, the formula is that heat equals current multiplied by current and then multiplied by time. As long as the current increases, the heat will increase a lot, so it can be felt quickly. The 19V load on the motherboard is connected in parallel. As long as there is a short circuit, the heat generated by that one will be very large. If you can't feel it, you must disconnect the search all the way. The search idea is that 19V is transmitted to every way through inductance, as long as you disconnect the two ends of the inductance measurement to see which end is short circuit, if it is still the main power terminal, you can follow this method to find it. If the measurement main power terminal is not short circuit, that is the short circuit of the load end of this road. As long as you find it, it will be solved and the load of this road will be removed. 19v short circuit can be used in this way, the voltage short circuit of 3V,5V,1.25V and so on can also be used in this way, which is called Burning Machine method. However, some problems should be paid attention to during maintenance and use, that is, the voltage cannot be adjusted randomly during maintenance. It should be accurately hit on the voltage value of the short circuit, and the current gear can be adjusted, but start to adjust to the minimum gear, plus-sized until it can be felt. If the voltage is not adjusted, it is likely to burn a lot of loads of this short circuit voltage. Remember.

Manifestation
Another is that the static current is about 0.15A. In this case, the phenomenon it shows is that the intuitive signal is that the main chip of the power supply is hot and very hot, and the phenomenon remains the same after replacing the main chip power chip SC1404. This should be done: disconnect the original voltage 3V_AUX,5V_AUX,12V_AUX generated by the power supply main chip SC1404 from its load, and disconnect PL8,PL6 and PJP7 connection point of 12V_AUX, however, it must be disconnected all the way, and cannot be disconnected at the same time. This is a part of the Circuit of the mainboard. As mentioned above, if there is no static current, it will also be related to these three channels. If a normal mainboard is disconnected, its static current will be zero, it depends on which way it affects. The procedure is as follows:
Disconnect the external power supply, disconnect the inductor PL8 of 3V_AUX, and then add the external power supply to see if the current value on power supply unit is zero or the original value, if it is the original value, connect the PL8 of 3V_AUX that you disconnected again, and then cut off the other two ways, which will definitely break. Then if it is zero, there is a problem with 3V_AUX along the way, which will affect the motherboard. At this time, you need to see whether the problem occurs at the generation end of 3V_AUX or the problem occurs at the load end, because the generation end is PU12, there is a problem with PU14 two N-type MOS tube, which is generally affected by virtual welding. If there is a problem with the load end, you have to remove the load one by one, only then can we judge which one is affected by the failure. Do maintenance work carefully, not careless. Otherwise, the fault point will not be found timely and accurately.
For most notebook motherboards, its static current is 0.03A-0. Between 07A. It is based on whether the original voltage 3V_AUX,5V_AUX,12V_AUX is normal. If it is normal, the static current is correct. If there is no original voltage, it is incorrect.