Dear Specialists
My customer is considering UCC28950.
They have used UCC2895 privious model.
Could you please see attached file and advise.
The customer want to know how to operate the circuit in detail.
background
The customer was using UC2895 for previous model.
The device has tendency for defecting PWM pulse
when the COMP voltage is 2.5V and high duty
The measures is COMP voltage reduces less than 2.5V
UCC28950 is a brand new device.
So the customer was interested in UCC28950.
They wanted to confirmed about the problem of defecting PWM pulse,
I confirmed TIJ PIC(Product Information Center)
We confirmed about UCC28950 to TIJ PIC.
They told me UCC28950 was improved to UC2895, but it isn't perfect.
It should be added external curcuit.
they attached the sample circuit, but they didn't explained details.
The Customer wants to know explanation of the details of the circuit.
So could you please teach me?
The customers requirement is listed below.
Input:100VAC
Output:42V 4kW
Questions from the customer are listed below.
(1)P2. of powerpoint,
Attached circuit is not able to change output voltage.
Could you please teach me adjustable voltage circuit.
output Voltage is changed by upper components.
(2)P1. of powerpoint,
They couldn't understand what does it mean about attached circuit.
It seems to be overlapped P.2
(3)about circuit of P.2
TIJ PIC said that is duty limiting circuit, but it seems COMP Voltage limiting circuit.
Is this right?
The customer wants to know if COMP voltage is always 2.5V below, PWM is not defect even if duty is 100%.
(4)whole measures
The customer doesn't desire a big change,because their considering phase is quite progressed.
They want a simple circuit, for example shunt regulator is added or another way.
Larger power dissipation may be accepted.
(5)P.2 of the circuit
shunt REG circuit block,
They want to know the details of a circuit.
voltege of every node, current increasing and decreasing of every element,
from stable state to FB voltage lower and from stable state to FB voltage higher.
*series and pararell elements are able to bandle.
explain transfer function of the circuit and how to derive it
What does it mean of the resistance on the shunt resister.
Why is it used for constant current source.
1777.UCC28950EA feedback clamp 20140320.pptx
Best regards,