Low cost constant current led open short detection circuit

Abstract

This utility model discloses a low-cost constant current LED open / short circuit detection circuit, including an LED lamp unit, a voltage input unit, an LED constant current driving unit, and an LED open / short circuit detection unit. The LED open / short circuit detection unit is equipped with resistors R7, R8, and R10, realizing constant current driving control of the LED lamp unit and detecting the open / short circuit status of the LED lamp unit. It not only eliminates the need for complex microprocessors and dedicated detection chips, greatly simplifying the circuit structure, but also uses all conventional and inexpensive electronic components, effectively reducing material costs. Furthermore, it has good versatility and compatibility, and can be widely applied in various electronic devices. Compared with traditional circuits using microcontrollers, this low-cost constant current LED open / short circuit has the advantages of both simple circuit structure and low overall power consumption.

Description

Technical Field

[0001] This utility model relates to the field of LED driver circuit technology, specifically to a low-cost constant current LED open / short circuit detection circuit. Background Technology

[0002] To ensure that the brightness of LEDs remains constant and does not change with fluctuations in input voltage, a constant current circuit is generally used to drive the LEDs.

[0003] Please refer to Chinese utility model patent publication number CN219697942U, which integrates an LED constant current drive module and an ADC acquisition module within a chip to control the LED current and detect the LED status. However, this utility model patent has the following problems:

[0004] 1. Complex circuit structure and high power consumption. LED fault detection relies on a complex microprocessor (such as a microcontroller) combined with a high-precision current sampling chip. This requires building a complex hardware circuit, including a microprocessor minimum system, AD sampling circuit, signal conditioning circuit, etc. This not only increases the difficulty and cost of circuit design, but also occupies a lot of board space, which is not conducive to the miniaturization and integration of the device. Moreover, the complex hardware circuit increases the power consumption of the overall product.

[0005] 2. High cost. The use of expensive microprocessors and dedicated detection chips, along with numerous supporting resistors, capacitors, and other components, significantly increases the material cost of the entire detection circuit. This is a significant disadvantage for cost-sensitive, mass-produced electronic products, reducing their market competitiveness.

[0006] 3. Poor compatibility. Different models of microprocessors and detection chips have different requirements for hardware interfaces and software programming, making it difficult for the detection circuit to adapt to different types and specifications of LEDs, resulting in a lack of versatility and flexibility.

[0007] Solving these problems is now a top priority. Utility Model Content

[0008] To address the technical problems of complex structure, high power consumption, high cost, and poor compatibility of existing LED driver circuits, this utility model provides a low-cost constant current LED open / short circuit detection circuit.

[0009] The technical solution is as follows:

[0010] The first aspect of this application relates to a low-cost constant current LED open / short circuit detection circuit, comprising an LED lamp unit, a voltage input unit, an LED constant current driving unit, and an LED open / short circuit detection unit. The output terminal of the voltage input unit is connected to the input terminal of the LED lamp unit. The LED constant current driving unit is equipped with a transistor Q1, the collector of which is connected to the output terminal of the LED lamp unit. The base of transistor Q1 is connected in series with a resistor R12 and then connected to an LED switch signal interface PA07. The base of transistor Q1 is also connected to the collector of transistor Q2. The emitter of the transistor is grounded. The common terminal of the base of transistor Q1 and the collector of transistor Q2 is connected in series with resistor R13 and then grounded. The LED open / short circuit detection unit is equipped with resistors R7 and R10. One end of resistor R7 is connected to the common terminal of the output terminal of the voltage input unit and the input terminal of the LED lamp group unit. The other end is connected in series with resistor R8 and then connected to the open / short circuit signal output interface DETECTLED. One end of resistor R10 is connected to the common terminal of resistors R7 and R8. The other end is connected to the common terminal of the collector of transistor Q1 and the output terminal of the LED lamp group unit.

[0011] The above-described low-cost constant current LED open / short circuit, based on a common LED constant current drive unit implemented with two transistors, and further supported by an LED open / short circuit detection unit composed of resistors R7, R8, and R10, achieves constant current drive control and open / short circuit detection for the LED lamp unit. This not only eliminates the need for complex microprocessors and dedicated detection chips, greatly simplifying the circuit structure and reducing the difficulty of circuit design and debugging, but also utilizes all common, inexpensive electronic components, effectively reducing material costs and enhancing the product's price competitiveness in the market, making it particularly suitable for mass-produced electronic products. Furthermore, it only requires reasonable design of resistors R7, R8, R10, and the transistors... By adjusting the parameters of Q1 and transistor Q2, the sensitivity and detection range of the LED open / short circuit detection unit can be easily adjusted, making it adaptable to different types and specifications of LED lamp units. It has good versatility and compatibility and can be widely used in various electronic devices. Furthermore, compared with the conventional LED constant current drive unit implemented with two transistors, this low-cost constant current LED open / short circuit achieves the open / short circuit status detection function of the LED lamp unit by adding an LED open / short circuit detection unit composed of only three resistors. The power consumption is almost negligible. Therefore, this low-cost constant current LED open / short circuit has the advantages of simple circuit structure and low overall power consumption compared with the traditional circuit using a microcontroller.

[0012] In some embodiments, the voltage input unit includes at least two voltage divider resistors connected in parallel, with one end of each voltage divider resistor connected to the voltage input interface VLED and the other end connected to the input terminal of the LED lamp unit.

[0013] In some embodiments, the voltage input unit is provided with a voltage input interface VLED, which is connected to the input terminal of the LED lamp unit after the series resistor R4.

[0014] In some implementations, the resistor R12 and the common terminal of the base of the transistor Q1 are connected in series with a capacitor C7 and then grounded, and the common terminal is also connected in series with a resistor R18 and then grounded.

[0015] In some embodiments, the LED lamp unit consists of at least one light-emitting diode connected in series.

[0016] In some implementations, both transistors Q1 and Q2 are NPN transistors. Attached Figure Description

[0017] Figure 1 The circuit diagram shows the low-cost constant current LED open / short circuit detection circuit when using the voltage input unit in Embodiment 1.

[0018] Figure 2 The circuit diagram shows a low-cost constant current LED open / short circuit detection circuit when using the voltage input unit in Embodiment 2. Detailed Implementation

[0019] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0020] like Figure 1 and Figure 2 As shown, a low-cost constant current LED open / short circuit detection circuit mainly includes an LED lamp group unit, a voltage input unit, an LED constant current driving unit, and an LED open / short circuit detection unit.

[0021] An LED light assembly unit consists of at least one light-emitting diode connected in series, which can be configured according to actual needs. This embodiment uses a single light-emitting diode, LED1, as an example.

[0022] The LED constant current drive unit includes transistors Q1 and Q2, resistors R12 and R13, where transistors Q1 and Q2 are both NPN transistors. The collector of transistor Q1 is connected to the cathode of LED1. The base of transistor Q1 is connected in series with resistor R12 and then to the LED switch signal interface PA07. Resistor R12 is used as a current limiting resistor. The base of transistor Q1 is also connected to the collector of transistor Q2. The emitter of transistor Q2 is grounded. The common terminal of the base of transistor Q1 and the collector of transistor Q2 is connected in series with resistor R13 and then grounded. Resistor R13 is also used as a current limiting resistor.

[0023] The output terminal of the voltage input unit is connected to the anode of the light-emitting diode LED1. Specifically, the voltage input unit has the following two implementation methods:

[0024] Voltage input unit embodiment 1: Please refer to Figure 1 The voltage input unit has a voltage input interface VLED at its input terminal. At least two parallel voltage divider resistors are connected between the voltage input interface VLED and the anode of the light-emitting diode LED1. One end of each voltage divider resistor is connected to the voltage input interface VLED, and the other end is connected to the input terminal of the LED lamp unit. In general, when the number of light-emitting diodes in the LED lamp unit is large, a larger input power is required to avoid insufficient power of the light-emitting diodes. Therefore, embodiment 1 of the voltage input unit is used. The reason for setting multiple voltage divider resistors in this embodiment is to reduce the power consumption and heat generation of the transistor Q1. The specific number of voltage divider resistors depends on the input power; fewer voltage divider resistors are used when the input power is low, and more voltage divider resistors are used when the input power is high. It should be noted that regardless of the number of parallel voltage divider resistors, the resistance value of each voltage divider resistor is the same. In this embodiment, three voltage divider resistors, R5, R6, and R16, are connected in parallel between the voltage input interface VLED and the anode of the light-emitting diode LED1.

[0025] To ensure the normal operation of transistor Q1 and LED1, the maximum current flowing through transistor Q1 and LED1 is 0.1A. Meanwhile, the design potential difference across resistor R13 in this embodiment is 0.7V. Therefore, the minimum resistance value of resistor R13 is: 0.7V / 0.1A = 7Ω.

[0026] Accordingly, to ensure the normal operation of the circuit, the maximum lamp effect resistance of resistors R5, R6 and R16 is: (9V-0.7V-1.1V-3V) / 0.1A=42Ω. Therefore, resistors R5, R6 and R16 should all be resistors with a resistance value of less than or equal to 126Ω, such as 120Ω resistors.

[0027] Voltage input unit embodiment 2: Please refer to Figure 2 The voltage input unit has a voltage input interface VLED. A resistor R4 is connected between the voltage input interface VLED and the anode of LED1. In other words, the voltage input interface VLED is connected in series with resistor R4 and then to the anode of LED1. Generally speaking, when the number of LEDs in the LED unit is small, the input power is usually low. Even with only one resistor R4, the power consumption of transistor Q1 is still low, and therefore the heat generated by transistor Q1 is also low.

[0028] Similar to embodiment 1 of the voltage input unit: the maximum resistance value of resistor R4 is 42Ω.

[0029] The working principle of the LED constant current drive unit is as follows:

[0030] Because the voltage across resistor R13 is clamped by the base and emitter voltages of transistor Q2, the current I of transistor Q1... E When the base potential remains constant:

[0031] I E =V BE(Q2) / R 13 ;

[0032] In the above formula, V BE(Q2) R represents the potential difference between the base and emitter of transistor Q2. 13 This indicates the resistance value of resistor R13.

[0033] Because the current of LED1 is different from the current of transistor Q1, I E Since they belong to the same circuit, when the input voltage VCC connected to the voltage input interface VLED fluctuates (increases or decreases), the current of LED1 will not change with the fluctuation of the input voltage VCC. Therefore, the brightness of LED1 will not increase or decrease with the fluctuation of the input voltage VCC, thus achieving the purpose of stabilizing the brightness of LED1.

[0034] The LED switch signal interface PA07 receives the switch signal. When the input to the LED switch signal interface PA07 is low, the collector and emitter of transistor Q1 are cut off, and the collector and emitter of transistor Q2 are also cut off, so LED1 is not lit. When the input to the LED switch signal interface PA07 is high, LED1 lights up, and transistors Q1 and Q2 are mutually clamped, maintaining a balanced state.

[0035] If the circuit becomes unstable due to some factor, causing an increase in the current flowing through LED1 (and resistor R13), the potential difference across resistor R13 will increase. This will raise the base potential of transistor Q2, thus reducing the equivalent resistance between the emitter and collector of transistor Q2. The equivalent resistance between the emitter and collector of transistor Q2 controls the base voltage of transistor Q1. Its reduction will undoubtedly move transistor Q1 closer to the cutoff direction, further reducing the current flowing through resistor R13. This effect continues until the circuit reaches equilibrium. In other words, the current flowing through resistor R13 (approximately equal to that of LED1) cannot be too large or too small, but remains a constant value, thus achieving the function of a constant current power supply and ensuring the stability of the brightness of LED1.

[0036] If the circuit becomes unstable due to some factor, causing the current flowing through LED1 (and resistor R13) to decrease, the potential difference across resistor R13 will decrease. This will lower the base potential of transistor Q2, thereby increasing the equivalent resistance between the emitter and collector of transistor Q2. Consequently, this increases the current flowing through resistor R13. This effect will continue until the circuit is balanced. In other words, the current flowing through resistor R13 (approximately equal to that of LED1) cannot be too large or too small, but must remain constant. This achieves the function of a constant current power supply, thus ensuring the stability of the brightness of LED1.

[0037] The final equilibrium is that the potential difference across resistor R13 equals the base voltage of transistor Q2, and the current through resistor R13 equals the current I of transistor Q1. E When the base potential remains constant, i.e.: I E =V BE(Q2) / R 13 The potential difference between the base of transistor Q1 and ground is: V R13 +V BE(Q2) , where V R13 This represents the potential difference of resistor R13.

[0038] The LED constant current driving unit in this embodiment uses two transistors to achieve constant current control of the light-emitting diode LED1, which is not only low in cost, but also has a simple and reliable circuit structure.

[0039] Furthermore, the LED constant current drive unit also includes a capacitor C7 and a resistor R18. Resistor R12 and the common terminal of the base of transistor Q1 are connected in series with capacitor C7 and then grounded. Resistor R12 and the common terminal of the base of transistor Q1 are also connected in series with resistor R18 and then grounded. Capacitor C7 acts as a filter and voltage regulator, while resistor R18 is a pull-down bias resistor. Its resistance value is designed to be much larger than that of resistor R12. By setting resistor R18, when the LED switch signal interface PA07 switches to a low level and capacitor C7 discharges, the voltage level of the base of the input transistor Q1 can always be kept low.

[0040] The LED switch signal interface PA07 can be connected to the switch signal terminal of the microcontroller on the upper circuit board, thereby sharing the microcontroller on the upper circuit board to realize the switching control of the LED lamp group unit. At the same time, this low-cost constant current LED open and short circuit detection circuit does not require a dedicated microcontroller. Furthermore, the LED switch signal interface PA07 can also be connected to the voltage input interface VLED.

[0041] Please see Figure 1 and Figure 2 The LED open / short circuit detection unit includes resistors R7, R8, and R10. One end of resistor R7 is connected to the common terminal of the output terminal of the voltage input unit and the input terminal of the LED lamp group unit. The other end of resistor R7 is connected in series with resistor R8 and then connected to the open / short circuit signal output interface DETECTLED. One end of resistor R10 is connected to the common terminal of resistors R7 and R8. The other end of resistor R10 is connected to the common terminal of the collector of transistor Q1 and the output terminal of the LED lamp group unit. That is, one end of resistor R8 is connected to the common terminal of resistors R7 and R10, and the other end of resistor R8 is connected to the open / short circuit signal output interface DETECTLED.

[0042] The open / short circuit signal output interface DETECTLED can be connected to the AD acquisition port of the microcontroller on the upper circuit board, thus sharing the microcontroller on the upper circuit board to realize the open / short circuit detection of the LED lamp group unit. At the same time, this low-cost constant current LED open / short circuit detection circuit does not require a dedicated microcontroller.

[0043] Specifically, the LED open / short circuit detection unit consists of resistors R7, R8, and R10. One end of each resistor is connected together. One end of resistor R7 is connected to the anode of LED1, one end of resistor R8 is connected to the AD acquisition port of the microcontroller, and one end of resistor R10 is connected to the collector of transistor Q1. This allows the state of LED1 to be detected through the voltage division of the resistors.

[0044] V DETECTLED =R 10 *(V LED -V R4 –VCE(Q1) -V BE(Q2) ) / (R7+R 10 )+V CE(Q1) +V BE(Q2) ;

[0045] In the above formula, V DETECTLED This indicates the voltage value of the DETECTLED output interface for open / short circuit signals, in V. LED This indicates the voltage value of the voltage input interface VLED, V R4 This represents the potential difference across resistor R4, in V. CE(Q1) V represents the potential difference between the collector and emitter of transistor Q1. BE(Q2) R represents the potential difference between the base and emitter of transistor Q2, and R7 represents the resistance value of resistor R7. 10 This indicates the resistance value of resistor R10.

[0046] Therefore, when LED1 is working normally, the detection voltage V DETECTLED =R 10 *(V LED -V R4 –V CE(Q1) -V BE(Q2) ) / (R7+R 10 )+V CE(Q1) +V BE(Q2) When LED1 is open-circuited, due to the large resistance of R7 / R10, the detection voltage V... DETECTLED =V LED *R 10 / (R 10 +R7); When LED1 is short-circuited, the detection voltage V DETECTLED =V LED -V R4 The LED1 detects different voltage values ​​under different operating conditions, which is used to determine the operating state of the LED1.

[0047] The function of resistor R13 is to set the constant current operating current, which can be adjusted according to different operating current requirements. The main function of resistors R7 and R10 is to provide the detection voltage through voltage division; using larger resistance values ​​can reduce power consumption. In this embodiment, the resistance value of resistor R7 is 390KΩ, the resistance value of resistor R10 is 100KΩ, and the resistance value of resistor R8 is 4.7KΩ. The resistance values ​​of resistors R7 and R10 are much larger than that of resistor R13, thus giving the LED open / short circuit detection unit the advantage of lower overall power consumption compared to traditional circuits using microcontroller detection. Furthermore, by adjusting the resistance values ​​of resistors R7 and R10, different scenarios can be accommodated.

[0048] Finally, it should be noted that the above description is merely a preferred embodiment of the present utility model. Those skilled in the art, under the guidance of the present utility model, can make various similar representations without departing from the spirit and claims of the present utility model, and such modifications all fall within the protection scope of the present utility model.

Claims

1. A low-cost constant current LED open / short circuit detection circuit, comprising an LED lamp unit, a voltage input unit, an LED constant current driving unit, and an LED open / short circuit detection unit, wherein the output terminal of the voltage input unit is connected to the input terminal of the LED lamp unit, the LED constant current driving unit is equipped with a transistor Q1, the collector of the transistor Q1 is connected to the output terminal of the LED lamp unit, the base of the transistor Q1 is connected to the LED switch signal interface PA07 after series resistor R12, the base is also connected to the collector of transistor Q2, the emitter of the transistor Q2 is grounded, and the common terminal of the base of the transistor Q1 and the collector of the transistor Q2 is connected to the ground after series resistor R13, characterized in that: The LED open / short circuit detection unit is equipped with resistors R7 and R10. One end of resistor R7 is connected to the common terminal of the output terminal of the voltage input unit and the input terminal of the LED lamp group unit, and the other end is connected in series with resistor R8 and then connected to the open / short circuit signal output interface DETECTLED. One end of resistor R10 is connected to the common terminal of resistors R7 and R8, and the other end is connected to the common terminal of the collector of transistor Q1 and the output terminal of the LED lamp group unit.

2. The low-cost constant current LED open / short circuit detection circuit according to claim 1, characterized in that: The resistance of resistor R7 is 390KΩ, the resistance of resistor R10 is 100KΩ, the resistance of resistor R8 is 4.7KΩ, and the resistance of resistor R13 is 7Ω.

3. The low-cost constant current LED open / short circuit detection circuit according to claim 1 or 2, characterized in that: The voltage input unit includes at least two voltage divider resistors connected in parallel. Each voltage divider resistor has the same resistance value. One end of each voltage divider resistor is connected to the voltage input interface VLED, and the other end is connected to the input terminal of the LED lamp group unit.

4. The low-cost constant current LED open / short circuit detection circuit according to claim 1 or 2, characterized in that: The voltage input unit is equipped with a voltage input interface VLED, which is connected to the input terminal of the LED lamp group unit after a series resistor R4.

5. The low-cost constant current LED open / short circuit detection circuit according to claim 1, characterized in that: The resistor R12 and the common terminal of the base of the transistor Q1 are connected in series with a capacitor C7 and then grounded. The common terminal is also connected in series with a resistor R18 and then grounded.

6. The low-cost constant current LED open / short circuit detection circuit according to claim 1, characterized in that: The LED light unit consists of at least one light-emitting diode connected in series.

7. The low-cost constant current LED open / short circuit detection circuit according to claim 1, characterized in that: Both transistors Q1 and Q2 are NPN transistors.

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