AL1692

Document number: DS39008 Rev. 2 - 2

9 of 15

www.diodes.com

September 2017

© Diodes Incorporated

AL1692

Thermal Foldback Protection (TFP)

AL1692 has a thermal foldback protection (TFP) function and adopts self-adaptive control method, which can prevent the system breaking down

caused by high temperature. The overheating temperature is set at +145°C typical, when the junction temperature of the IC is higher than +145°C

typical, the device will linearly decrease the internal reference voltage to decrease the output current. As a result of this feature, the device can

control the system

’s output power at high ambient temperature, to control the quantity of heat of the system. This enhances the safety of the

system at high temperature.

Thermal foldback waveform is shown below:

100%

50%

Junction Temperature/

°C

Output Current

OTP

Figure 1. Thermal Foldback Waveform

Over-Temperature Protection (OTP)

The AL1692 has over temperature protection (OTP) function. When the junction temperature reach to +160°C typical, the IC will trigger an over-

temperature protection, which causes the device to shut down and latched condition. Once OTP triggered, the system need to be resumed after

the system

’s AC source supply has been reset and power up.

Design Parameters

Setting the Current Sense Resistor R5

The AL1692 adopts boundary conduction mode, the output current is calculated as below,

_

0

11

2

OFF

O MEAN

PEAK

ON

OFF

DELAY

t

I

I

dt

t

t

t





 









Where,

The AL1692 is a closed loop constant current control with the relationship between output current and current sense voltage follows this equation

0

1

R5

OFF

REF

PEAK

ON

OFF

DELAY

t

V

I

dt

t

t

t





 









Where,

R5 is the current sense resistor

So we can get the output current equation as below,

_

1

=

25

REF

O MEAN

V

I

R

