LD7750EGR View Datasheet(PDF) - Unspecified

Part Name

Description

Manufacturer

LD7750EGR

High Voltage Green-Mode PWM Controller with Over Temperature Protection

Unspecified 

LD7750E

R-C filter (as shown in Fig. 16) for higher power

applications to avoid the CS pin being damaged by the

negative turn-on spike.

Fig. 14

Current Sensing, Leading-edge Blanking

and the Negative Spike on CS Pin

The typical current mode PWM controller feedbacks both

current signal and voltage signal to close the control loop

and achieve regulation. The LD7750E detects the primary

MOSFET current from the CS pin, which is not only for the

peak current mode control but also for the pulse-by-pulse

current limit. The maximum voltage threshold of the

current sensing pin is set as 0.85V. Thus the MOSFET

peak current can be calculated as:

IPEAK(MAX)

=

0.85V

RS

A 250nS leading-edge blanking (LEB) time is included in

the input of CS pin to prevent false-trigger caused by the

current spike. For low power applications, if the total pulse

width of the turn-on spike is less than 250nS and the

negative spike on the CS pin is above -0.3V, the R-C filter

(as shown in Fig.15) is eliminable.

However, the total pulse width of the turn-on spike is

related to the output power, circuit design and PCB layout.

Nevertheless, it is strongly recommended to add a small

Leadtrend Technology Corporation

LD7750E-DS-00 February 2012

10

www.leadtrend.com.tw

Fig. 15

Fig. 16

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