Bias current of TL783?

Hello Stain b,

The bias current (ICC) in the TL783 flow from VIN to VOUT. This current varies with Vin-Vout potential. The highest value is 15mA (Vin-Vout=125V).
Figure 12 in the data sheet shows typical behaviour.

Regards,
Ron Michallick

Dear TI,

          Thanks for a reply.We are designing 60V e-bike controller in that one power supply section we are facing the 

         following problem.We tried 3 different circuits for 70V to 15V conversion the maximum o/p current is 90mA,

         Ambient temperature is 50'C.Can you able suggest which one is suitable for this application?

                    In the all three circuits we faced thermal issue(more heat) problem, if it's needed to use a heat sink

         how can  and where i can use?  In the third circuit TL783 bias current is more it's taking 14mA how can i 

        reduce ?how can i use TL783 efficiently in this application?

Stain,

If just linear regulators are used, the best case power dissipation with 70V input is (70V-15V)*(90mA) = 5 watts! The efficiency of this ideal supply is (15V*90mA)/(70V*90mA) = 21%. The TL783 can handle this power without needing a second regulator, but it will need a good heat sink. If the minimum load on the 15V line is greater than 15mA then the TL783 feedback resistor values can be increased to reduce current wasted.

However, I suggest adding a switching regulator to the circuit. The circuit I attached, uses the TL2575HV-15 which can handle 60V input. I added a simple voltage drop on the input. In normal operation the dropper components won't dissipate much heat, but they must support the surge current to charge the 100uF capacitor

Regards,
Ron Michallick