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Led Driver Open Circuit Protection


The provision of robust short-circuit protection is a key feature of the company’s LT3795 boost DC/DC LED driver. Adding protection to existing designs is possible but the integration of such features in newer LED driver ICs makes life much easier. The output of the op amp 72 is connected to a terminal of the pass transistor 70, controlled by the brightness control signal, and the other terminal of the pass transistor Another aspect of the LED driver 50 is its ability to detect shorted LEDs and compensate for the shorted LEDs. http://vinaprosoft.com/led-driver/led-dc-driver-circuit.php

It also provides reverse battery/power polarity protection for greater LED reliability. Write a comment To comment please Log In Most Commented 03.26.2013 Critical guidelines for RF and microwave PCB Design 06.27.2005 Designing a custom LCD display controller Related Content 04.06.2009 | Design This makes them the DC-input cousin to the AC LED replacement bulbs. The brightness control signal 16 is divided by resistors R18 and R19. http://www.electronicproducts.com/Analog_Mixed_Signal_ICs/Drivers_Displays_LED_etc_/Understanding_protection_modes_for_LED_drivers.aspx

What Is Open Circuit Protection

It also applies to buck, SEPIC, and Cuk topologies, as well as isolated topologies such as flyback, forward, and other topologies. All Rights Reserved. Typically, VLED is a low voltage, but may spike if multiple LEDs short simultaneously. A Simple Over-Voltage Protection Circuit for LED Drivers This boost circuit implements current mode control and senses the LED current via resistor R14.

  • Chromaticity also varies with temperature.
  • VOUT will be greater than VLED by the combined forward drops of the LEDs when operating at their intended peak current.
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  • Circuitry for power-supply protection also requires line isolation from ground to protect against possible shock hazards.
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  • They are clamping devices, so they don't short the ac input line when they activate (doing so would trip the overcurrent protection), and they recover automatically when the overvoltage is gone.

Here, the most immediate threat is overvoltage failures. In these cases, the fuse may not be sensitive enough to open on faults in the switching section (DC/DC conversion block in the same block diagram.) However, a downstream fuse can An MOV is once again the guardian of the AC input, and are usually sized as a percentage of the total design cost. Led Protection Circuit CONNECT WITH EDN ON TWITTER ON FACEBOOK ON LINKEDIN EDN VAULT Latest Collections Issue Archives Loading...

The magnitude of the error amplifier output, connected to a capacitor, may be monitored by an external circuit to detect how many LEDs have shorted so that remedial action may be Overheating may occur when the forward voltage drop across the LED decreases to a value significantly less than the typical stated value. Additionally, if there is an open circuit, VLED will be zero volts. http://www.ledsmagazine.com/articles/print/volume-12/issue-2/features/developer-forum/protect-an-led-driver-against-output-shorts-to-ground.html A MOSFET 54 is shown in series with the LEDs D1-D4, selectively coupling the LEDs to ground via a low value (e.g., <1 ohm) sense resistor R56.

LED fixtures will still need replacement after an accident or failure; therefore they still come in a bulb-like form - sometimes with the driver electronics integrated into the bulb form factor, Led Driver Failure Causes Thus, the perceived brightness of the LEDs would be about half the brightness of the LEDs when fully on. Open LED protection devices usually have low on-state voltage, typically 1.5V, and a low off-state current. Let's look at five LED lighting applications with large markets and discuss the threats to the lighting system as well as the various circuit protection strategies that can be deployed to

Constant Current Boost Led Driver

The other terminal of transistor 70 is connected to the gate of MOSFET 54. The need for a slow-blow fuse here shows up in this section. What Is Open Circuit Protection High value resistors R60 and R61 form a resistor divider connected between ground and the end of the series string of LEDs. Boost Converter Open Circuit Protection Electronics Weekly is at the heart of the electronics industry and is reaching an audience of more than 120,000 people each month.

In particular, their pole-mounted outdoor location makes them vulnerable to lighting-induced overvoltages and overcurrents, two of the most common failure modes at the front end of an SMPS. http://vinaprosoft.com/led-driver/led-driver-and-circuit.php Figure 2: The LT3796 configured as a boost converter to drive a 34 W LED string from a wide input range. A zener diode 76 connected between VLED and ground protects the MOSFET 54 from any high voltage spikes caused by shorting LEDs. In contrast, conventional LED drivers detect an overvoltage condition, which takes time to occur after the open circuit is created, before shutting down the regulator. Led Boost Driver

It will further consider the efforts made by LED driver manufacturers to incorporate features that protect against damaging conditions and ensure continued safe operation with both open- and short-circuit LED strings. In this situation, the voltage across the current sense resistor drops to zero. A setback power limit reduces the drive current during overvoltage conditions. navigate to this website Once the Zener diode clamp voltage of 36V is reached and Zener current flows, regulation is reasserted.

Power line coupled transients and surges can also reduce LED lifespan, and many LED drivers are susceptible to damage resulting from improper DC voltage levels and polarity. Boost Converter Circuit Diagram in the U.S. A non-inverting input of the comparator 58 is connected to a reference voltage VREF_2, which is a fixed voltage of a magnitude above zero volts but below a normal VFB encountered

That event trig­gers the associated PLED device to turn on and maintain cur­rent through the rest of the LED string.

If an LED shorts, the boost regulator reduces its output voltage, and the duty cycle of the brightness control signal is automatically increased. The processor 66 may be any control circuit, such as a logic circuit. And if appropriate thermal design precautions can’t completely avoid excessive temperatures, then the provision of some form of overheating protection may be necessary. The invention is not limited to the boost topology.

This means fail-safe backup overcurrent protection may be required. Enter your email below, and we'll send you another email. {* #resendVerificationForm *} {* signInEmailAddress *} {* /resendVerificationForm *} Verification Email Sent Check your email for a link to verify your Any difference between VLED and the feedback voltage is dropped across the MOSFET. http://vinaprosoft.com/led-driver/led-driver-circuit-12v.php There are three problems with the above typical solution: 1.

Search Sign In | Sign Up Edit Profile | Sign Out Login Sign In With {* loginWidget *} {* #signInForm *} {* signInEmailAddress *} {* currentPassword *} Forgot your password? DC section The dc fuse in this section is for overcurrent protection. The divided voltage is connected to an inverting input of an op amp 64 (an error amplifier), and a non-inverting input is connected to a reference voltage VREF_1. Two major causes of transient overvoltage have long been recognized: system switching transients and transients triggered or excited by lightning discharges (in contrast to direct lightning discharges to the power systems,

Figure 3 shows the LED section of a typical lighting application. Initial projections from the US-based Lighting Research Center suggest that the life of an LED at 85ºC might be just 20,000 hours compared to 80,000 hours at 45°C (where "life" is Sometimes, two LEDs in series can be protected with one protection device as a way to lower costs if needed. In the event of an LED open circuit, RSET will pull the voltage sensed on pin ISEN up to VIN, which will cause the device to shut down.

However, additional overcurrent protection devices may be needed to help protect ICs and other sensitive electronic components. One particular area of concern is the SMPS front end. Close {* mergeAccounts {"custom": true} *} {| rendered_current_photo |} {| current_displayName |} {| current_emailAddress |} {| foundExistingAccountText |} {| current_emailAddress |}. {| moreInfoHoverText |} {| existing_displayName |} - {| existing_provider |} This article discusses requirements for protecting LED drivers, paying special attention to how LED overheating can be avoided by using a thermal regulator circuit with current foldback.  Background on LED operating

Enter your email below, and we'll send you another email. {* #resetPasswordForm *} {* signInEmailAddress *} {* /resetPasswordForm *} Create New Password We've sent you an email with instructions to create LED strings are widely used in a range of lighting application sectors, from domestic consumer through retail, architectural and automotive. Spread spectrum frequency modulation can be activated for improved EMC. This is because when an open LED condition occurs, the VOUT will still have to rise to the predetermined OVP level to activate the OVP circuit.

Return to Lighting Homepage QUICK EMAIL SIGNUP Subscribe CUSTOMER SERVICE OFFICE Elsenheimerstr. 1180687 MunichGermany +49 (0)89 520 462 110 COMPANY About Us Educational Sales Press Room Careers @ Mouser Quality Environmental To prevent such VOUT runaway failure from happening, a typical solution is put a resistor divider (R42 and R43) between VOUT and ground, in parallel to the LEDs and R14. The operations of the oscillator 30, PWM comparator 32, and the other boost regulator components have been discussed with reference to FIG. 1. The output of comparator 58 is connected to the MOSFET driver 39.

Such high voltages require components with a breakdown voltage well in excess of 90 volts.