TLE4305 Datasheet, PDF (12/15 Pages) Infineon Technologies AG – Voltage-Current Regulator

TLE 4305
Current Control Loop
Current Loop TLE 4305
from Voltage Loop
V_REF
R_I1
25 kΩ
Control
Logic
Driver
1 kΩ _OUT
D2
CSE ^RI1
C-OTA
R_Sense
25 kΩ
CRE
R_{CC CCO}
1 kΩ
C_CCO
10 nF
AES02880
Figure 7 Current Control Loop
To detect the current a sense resistor R_sense is placed in the current back-path to the
transformer (see Figure 4 and Figure 7).
The control operational amplifier compares the voltage at pin CRE to the voltage at the
inverting input of the OTA. In an overcurrent condition, the overall closed loop through
current loop, opto isolator, primary regulator, transformer and the application reduces the
PWM duty cycle to meet the closed loop condition.
V_CSE - V_CRE is typical 200 mV.
The current limit is defined by
I_Qmax = 200 mV / R_sense
(6)
To compensate the overall closed current loop a 10 nF capacitor should be connected
to pin VCO. With the internal 1 kΩ resistor it reduces the voltage loop’s bandwidth.
As already explained for the voltage loop, the capacitor can be modified according to the
overall loop’s bandwidth.
To further improve the current control in addition a compensation can be added at pin
CRE as shown in Figure 8.
Data Sheet
12
Rev. 2.1, 2004-01-01