Data Sheet

12

Rev. 2.1, 2004-01-01

TLE 4305

Current Control Loop

Figure 7

Current Control Loop

To detect the current a sense resistor

R

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

The current limit is defined by

I

(6)

To compensate the overall closed current loop a 10 nF capacitor should be connected

to pin VCO. With the internal 1 k

Ω 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.

AES02880

C-OTA

R

I1

25 k

Ω

C

CCO

10 nF

V

REF

CSE

CRE

Current Loop TLE 4305

Control

Logic

from Voltage Loop

1 k

Ω

R

CC

1 k

Ω

OUT

CCO

R

I1

25 k

Ω

R

Sense

D2

Driver