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LED power supply overvoltage protection circuit is normally what effect is there? _

by:Fuyuang     2021-01-14
LED power supply overvoltage protection circuit is normally what effect is there? 1225, 2020 - 05 - 12 16:55:35 in LED power supply protection circuit design process, the setting of over-voltage protection circuit is essential, can effectively guarantee the normal operation of the whole power system. In this article, we will be LED power supply overvoltage protection circuit, a brief introduction, and will also provide you the engineers share a kind of effective overvoltage protection circuit set. In LED power supply design process, the current domestic most of the power system adopts constant current drive solutions. For steady flow type power supply, if the load circuit, current detection of resistance at the ends of the voltage drop to zero, once a given value is not zero, controller will make a sharp surge to the maximum output voltage, the load is very dangerous for connection to the poor contact. For LED, semiconductor refrigeration load, over voltage occurs, the most urgent task is to protect the load, the second is to protect the power switch tube. In order to effectively protect the load and switch power tube, in the process of LED power supply circuit is set, we have two kinds of protection method can be used at the same time, one is placed to implement two-way, TVS for instantaneous impulse voltage protection, another way is to let the power to immediately stop work when load break. Start with the first LED power over-voltage protection measures. As is known to all, is a kind of diode TVS in the form of highly efficient protection device. When the poles TVS diode reverse transient high-energy impact, it can, at the rate of nanosecond between the poles of high impedance is a low impedance, absorb as much as several kilowatts of power surge, the voltage between the poles clamp which is located in a predetermined value, effectively protect the electronic components in a circuit from the damage of all kinds of surge pulse. Can also be resistance and TVS series, when TVS not breakdown, there is no current resistance, in case of overvoltage, TVS is punctured, the current flows through the resistor, producing pressure drop, as protection signal, the shutdown to the PWM chip, the blockade PWM pulse output. The setting of the second method, as shown in the figure below: the picture shows the LED power supply overvoltage protection circuit from the LED power supply overvoltage protection circuit set figure above we can see that in the system, and R24 R27 provide op-amp in-phase input fixed small voltage U +. R26 load current input for sampling. When the load circuit occurs, the voltage of the op-amp inverting input U - = 0, so U + & gt; U - , the op-amp output voltage of high level, no-load protection signal are presented. At the same time, the time constant R30 x C15 cooperate with the power of a given time constant adjustment, makes the no-load protection misoperation don't happen.
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