Over-current protection circuit of light-emitting diode (LED) constant-current driving circuit

Abstract

An over-current protection circuit of an LED constant-current driving circuit comprises an LED, a switching tube and a switching control module, wherein an output end of the switching tube is grounded after being electrically connected with the LED, an input end of the switching control module is electrically connected between the output end of the switching tube and the LED, an output end of the switching control module is electrically connected with a control end of the switching tube, and the switching control module is used for controlling the connection and the disconnection of the switching tube by controlling of the control end of the switching tube. The peak current of the LED is limited through the design method which is simple, clear and low in complexity, so that the LED is protected.

Description

【Technical field】 [0001] The invention relates to a protection circuit, in particular to an overcurrent protection circuit of an LED constant current drive circuit. 【Background technique】 [0002] During the working process of the LED constant current source driver, when the output load is too large, the internal components of the device or the external circuit have a partial short circuit, the overcurrent protection circuit can limit the current flowing through the switch tube, so that it can be controlled within the rated range within. [0003] There are two commonly used current limiting circuits: [0004] One is a resistor current-limiting circuit. In this way, the circuit is simple. By changing the value of the current-limiting resistor R, the operating current can be changed, thereby changing the luminous intensity of the LED (Light Emitting Diode). However, this driving method also has many disadvantages: first, if the input voltage fluctuates slightly, it will dire...

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Problems solved by technology

However, this driving method also has many disadvantages: first, if the input voltage fluctuates slightly, it will directly lead to fluctuations in the driving current, thereby affecting the luminous flux output and the change in luminous brightness; second, the current limiting resistor connected in series It will consume a lot of power, especially when driving high-power LEDs, so the efficiency of the entire system will be a serious problem; finally, if the brightness of the LED is adjusted by adjusting the R value, the R value The change causes the current flowing through the LED to change, which will cause the color of the white light emitted by the LED to shift, so this driving method is mostly used in simple applications such as indicator lights.

[0005] Another protection method is to detect the current flowing through the switch tube, generally by connecting a small resistor in series with the switch tube or using the gate-source voltage of the switch tube to detect, by detecting the voltage drop of the resistor or the gate-source voltage of the switch tube, and then Compared with the reference voltage source, if the voltage drop is higher than the reference voltage source, the output voltage of the comparator will turn off the switch tube, prevent the current from rising further, and ensure that the current does not exceed the rated value. This method has higher requirements on the accuracy of the resistor. And when the ambient temperature changes, there will be errors between the detected value and the actual value, which will affect the circuit performance

[0006] Neither of the above two methods can solve the protection problem of the circuit when the current suddenly increases while improving the system efficiency.

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