A DC / DC switching power supply input with UC3843 is a 24V power supply between two power supplies is up to 200M line now the situation is DC / DC power supply at no time when the load is measured at this time DC / DC power input It is actually less than 15V if the DC / DC power supply is loaded with about 10W and the 24V power supply output is adjusted to 27V or more when the DC / DC power supply is working
In front of the wrong
In the load when the 10W when the front power output is adjusted to 27V measured when the power input voltage is 14.5V or so when the no-load time is normal
add another point
With 10W when the front of the power output is adjusted to 27V below the two power between the current is significantly increased at this time into the DC / DC power supply voltage from 15V down to 6,7V looks more like the back of the power from Excited and DC / DC of this power supply in the 9V or so input conditions can work properly
There are three problems need to be identified, 1 is the power output power in front of how much, if small, can not be changed, only for the front of the power; 2 is 200 meters diameter, if too thin, a little current Will produce a lot of pressure drop, you can change the thick line? 3 is the power requirements of the back of the input voltage is how much, if the low limit close to 24V requires the front power supply has sufficient capacity, the transmission line pressure drop as small as possible.
DC / DC no load when the input less than 15V? Look at the 24V power output is how much, if it is 15V instructions that the power supply voltage is not correct, otherwise it is DC / DC no-load power is too large
There are three problems need to be identified, 1 is the power output power in front of how much, if small, can not be changed, only for the front of the power; 2 is 200 meters diameter, if too thin, a little current Will produce a lot of pressure drop
DC power supply inside the capacitor caused by leakage can not bring the load, I have previously repair, replace the filter capacitor to solve the problem. Leakage, can only replace, you add more capacitors is useless.
The reason is obvious, one is the power cord is too long, the second is behind the power efficiency is too low, both at least one or both.
According to what you said, "when the load with 10W, when the front power output is adjusted to 27V measured after the power input voltage is about 14.5V", we can see 200 meters on the cable voltage drop as much as 12.5V! At this time the output power of the front power supply should be about 1A (assuming the efficiency of the power supply is about 80%), the power line resistance is about 12.5Ω. Because the power required for the rear is constant, the current will be greater if the transmission voltage is reduced and the efficiency of the DC / DC power supply will be lower.
This long-distance transmission power and low-voltage transmission is not appropriate, should be used AC / DC isolation module from 220V AC voltage conversion required power.
