hello sir/Madam,
In one of our project am using Texas UCC28880.
Simple Block diagram is shown below.
Problem:
1. If we stop supplying input Voltage 250V bus, 24V output voltage is decreasing Linearly. At certain point of input voltage(24V) 3.3V off completely.
At same time Voltage at 24V bus is Decreasing to 14V, because of no load at 24V bus is tying to build the voltage from 14V to some 15.6V, at this input voltage(15.6V) am getting 3.3V.
2. Due to above issue , we have seen some reboot is at 3.3V bus,
We are using a regulators which will convert 24V to 3.3V and which will have wide input voltage range 4.5V to 42V.
Input Bus voltage 250V and we are converting to 24V by using UCC28880
Issue Description :
Input bus voltage goes to 32V, at same time 24V Vout is reducing to some 14V even 3.3V output Voltage is low at this voltage Hence there is no load on 24V bus voltage. Because of this 24V bus is trying to increase slightly higher voltage like 15.6V, Due to this voltage my 3.3V regulator is turned ON. Need your help to control the 24V Bus And UCC28880 don’t have any control pin to control the 24V bus.
Please find the Scope picture with channel description
CH1: Main Bus Voltage(250V)
CH2: 24V Main Bus Voltage
CH3:3V3 Main Bus Voltage
CH4: Vcap Voltage