阅读说明：本技术 一种宽电压输入、功率自适应的led恒流驱动电路 (Wide-voltage-input and power-adaptive LED constant-current driving circuit ) 是由 刘海辉 于 2018-06-12 设计创作，主要内容包括：本发明公开了一种宽电压输入、功率自适应的LED恒流驱动电路,该电路包括电源电压测量电路、MCU控制单元、恒流驱动电路、LED负载。电源电压测量电路用于测量LED负载的开关电源VCC。MCU控制单元用于检测并计算LED负载的功率,并与设定的阈值功率进行比对,通过PID算法,调整PWM脉宽至合适的参数,使LED负载功率以最短的时间恢复到设定的阈值功率以内。恒流驱动电路由BUCK降压回路、增强电路、二阶低通滤波电路、采样反馈电路构成。本发明提供的LED恒流驱动电路,具有宽范围电压输入能力,且能够自动调整参数,适应于不同功率的LED负载灯具,可广泛用于各种LED产品的驱动。(The invention discloses a wide-voltage-input and power-adaptive LED constant-current driving circuit which comprises a power supply voltage measuring circuit, an MCU (microprogrammed control unit), a constant-current driving circuit and an LED load. The power supply voltage measuring circuit is used for measuring a switching power supply VCC of the LED load. The MCU control unit is used for detecting and calculating the power of the LED load, comparing the power with the set threshold power, and adjusting the PWM pulse width to a proper parameter through a PID algorithm to recover the power of the LED load within the set threshold power in the shortest time. The constant current driving circuit consists of a BUCK voltage reduction loop, a reinforcing circuit, a second-order low-pass filter circuit and a sampling feedback circuit. The LED constant current driving circuit provided by the invention has wide-range voltage input capability, can automatically adjust parameters, is suitable for LED load lamps with different powers, and can be widely used for driving various LED products.)

1. A wide-voltage-input and power-adaptive LED constant-current driving circuit comprises a power supply voltage measuring circuit, an MCU control unit, a constant-current driving circuit and an LED load. The power supply voltage measuring circuit is used for measuring a switching power supply VCC of the LED load. The MCU control unit is used for detecting the power of the LED load, comparing the power with the set threshold power, and adjusting the PWM pulse width to a proper parameter through a PID algorithm to recover the power of the LED load within the set threshold power in the shortest time. The constant current driving circuit consists of a BUCK voltage reduction loop, a reinforcing circuit, a second-order low-pass filter circuit and a sampling feedback circuit.

2. The LED constant current drive circuit according to claim 1, wherein: and the MCU control unit reversely calculates the VCC value measured and calculated by the power supply voltage measuring circuit and the current value fed back by the sampling feedback circuit to calculate the power of the LED load.

3. The LED constant current drive circuit according to claim 1, wherein: the MCU control unit calculates the power of the LED load through detection, compares the power with a set threshold power, and adjusts the PWM pulse width to a proper parameter through a PID algorithm so that the power of the LED load is recovered to be within the set threshold power in the shortest time.

4. The constant current drive circuit according to claim 1, wherein: the BUCK loop is composed of an NMOS tube Q1, an inductor L1 and a Schottky diode D1.

5. The constant current drive circuit according to claim 1, wherein: the boost circuit is composed of an inverter U1A. The inverter U1A is mainly used to increase the driving current and voltage and accelerate the on/off speed of the NMOS transistor Q1, so that the NMOS transistor Q1 is basically in the on/off state, thereby reducing MOS heat generation and improving the reliability of the driving board.

6. The constant current drive circuit according to claim 1, wherein: the second-order low-pass filter circuit is composed of a resistor R5, a resistor R6, a capacitor C2 and a capacitor C3. According to a cut-off frequency formula, the frequency f is 1/(2 pi RC), so that the cut-off frequency is 1.59K, the frequency (above 20 KHz) of the PWM output is far greater than the cut-off frequency, so that a good filtering effect can be obtained, and the filtered direct-current voltage signal is supplied to the MCU control unit for detecting the LED load current CUR _ R.

7. The constant current drive circuit according to claim 1, wherein: the sampling feedback circuit is composed of a resistor R7. The resistor R7 is used for sampling current, and a direct-current voltage signal filtered by a second-order low-pass filter circuit can be supplied to the MCU control unit and is used for detecting the LED load current CUR _ R.

Technical Field

The invention relates to an LED constant current driving circuit, in particular to an LED constant current driving circuit with wide voltage and self-adaptive power.

Background

As LEDs are used more and more widely in life, research and design on LED driving circuits are getting hotter. In the method, the constant current output by the constant current driving circuit depends on the size of a sampling resistor and is limited to a fixed voltage value.

In addition, most of the current LED constant-current driving circuits limit the maximum working current of an LED in a PWM pulse width regulation mode, so that the driving circuit needs to be measured and adjusted again when one LED is replaced, thereby wasting time and labor and having lower working efficiency.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a wide-voltage and power self-adaptive LED constant-current driving circuit.

In order to realize the purpose, the invention adopts the technical scheme that: a wide-voltage-input and power-adaptive LED constant-current driving circuit comprises a power supply voltage measuring circuit, an MCU control unit, a constant-current driving circuit and an LED load. The power supply voltage measuring circuit is used for measuring a switching power supply VCC of the LED load. The MCU control unit is used for detecting the power of the LED load, comparing the power with the set threshold power, and adjusting the PWM pulse width to a proper parameter through a PID algorithm to recover the power of the LED load within the set threshold power in the shortest time. The constant current driving circuit consists of a BUCK voltage reduction loop, a reinforcing circuit, a second-order low-pass filter circuit and a sampling feedback circuit.

And the MCU control unit reversely calculates the VCC value measured and calculated by the power supply voltage measuring circuit and the current value fed back by the sampling feedback circuit to calculate the power of the LED load. And comparing the power with the set threshold power, and adjusting the PWM pulse width to a proper parameter through a PID algorithm to recover the LED load power within the set threshold power in the shortest time.

The BUCK loop is composed of an NMOS tube Q1, an inductor L1 and a Schottky diode D1.

The boost circuit is composed of an inverter U1A. The inverter U1A is mainly used to increase the driving current and voltage and accelerate the on/off speed of the NMOS transistor Q1, so that the NMOS transistor Q1 is basically in the on/off state, thereby reducing MOS heat generation and improving the reliability of the driving board.

The second-order increasing low-pass filter circuit is composed of a resistor R5, a resistor R6, a capacitor C2 and a capacitor C3. According to the formula of the cut-off frequency, the frequency f is 1/(2 pi RC), so the cut-off frequency is 1.59K, the frequency (above 20 KHz) of the PWM output is far greater than the cut-off frequency, so a better filtering effect can be obtained, and the filtered direct-current voltage signal can be supplied to the MCU control unit for detecting the LED load current CUR _ R.

The sampling feedback circuit is composed of a resistor R7. The resistor R7 is used for sampling current, and a direct-current voltage signal filtered by a second-order low-pass filter circuit can be supplied to the MCU control unit and is used for detecting the LED load current CUR _ R.

After the scheme is adopted, the LED load lamp has wide-range voltage input capability, can automatically adjust parameters, is suitable for LED load lamps with different powers, and can be widely used for driving various LED products.

Drawings

Fig. 1 is a schematic block diagram of the present invention.

Fig. 2 is a schematic diagram of a power supply voltage measurement circuit.

Fig. 3 is a schematic diagram of a constant current driving circuit.

Detailed Description

Embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

Referring to fig. 1, the invention provides a wide-voltage-input and power-adaptive LED constant-current driving circuit, which includes a power supply voltage measuring circuit, an MCU control unit, a constant-current driving circuit, and an LED load. The power supply voltage measuring circuit is used for measuring a switching power supply VCC of the LED load. The MCU control unit is used for detecting the power of the LED load, comparing the power with the set threshold power, and adjusting the PWM pulse width to a proper parameter through a PID algorithm to recover the power of the LED load within the set threshold power in the shortest time. The constant current driving circuit consists of a BUCK voltage reduction loop, a reinforcing circuit, a second-order low-pass filter circuit and a sampling feedback circuit.

And the MCU control unit reversely calculates the VCC value measured and calculated by the power supply voltage measuring circuit and the current value fed back by the sampling feedback circuit to calculate the power of the LED load. And comparing the power with the set threshold power, and adjusting the PWM pulse width to a proper parameter through a PID algorithm to recover the LED load power within the set threshold power in the shortest time.

The BUCK loop is composed of an NMOS tube Q1, an inductor L1 and a Schottky diode D1.

The boost circuit is composed of an inverter U1A. The inverter U1A is mainly used to increase the driving current and voltage and accelerate the on/off speed of the NMOS transistor Q1, so that the NMOS transistor Q1 is basically in the on/off state, thereby reducing MOS heat generation and improving the reliability of the driving board.

The second-order increasing low-pass filter circuit is composed of a resistor R5, a resistor R6, a capacitor C2 and a capacitor C3. According to the formula of the cut-off frequency, the frequency f is 1/(2 pi RC), so the cut-off frequency is 1.59K, the frequency (above 20 KHz) of the PWM output is far greater than the cut-off frequency, so a better filtering effect can be obtained, and the filtered direct-current voltage signal can be supplied to the MCU control unit for detecting the LED load current CUR _ R.

The sampling feedback circuit is composed of a resistor R7. The resistor R7 is used for sampling current, and a direct-current voltage signal filtered by a second-order low-pass filter circuit can be supplied to the MCU control unit and is used for detecting the LED load current CUR _ R.

The working principle of the invention is as follows:

the power supply voltage measuring circuit in fig. 2 comprises two precise resistors R1 and R2, wherein the ADC measuring range of the MCU control unit is 0-3.3V, and the voltage is divided by a voltage dividing formula V_{POW_VOL}VCC R2/(R1+ R2) can be used to reverse the measured VCC voltage range from 0 to 59.4V. In this way, the LED switching power VCC may have a suitable wide voltage input range, such as 12V voltage class, when it is higher than the load voltage: voltage grades of 12-16V and 24V: voltage grades of 24-32V and 36V: 36-48V.

The constant current driving circuit of fig. 3 is a BUCK voltage-reducing loop composed of an NMOS transistor Q1, an inductor L1 and a schottky diode D1.

The PWM _ R output by the MCU control unit enhances the driving current through the inverter U1A, and reduces the on and off time of the NMOS tube Q1, thereby reducing the loss. The inverter U1A is mainly used to increase the driving current and voltage and accelerate the on/off speed of the NMOS transistor Q1, so that the NMOS transistor Q1 is basically in the on/off state, thereby reducing MOS heat generation and improving the reliability of the driving board.

R5, R6, C2 and C3 form a second-order low-pass filter circuit, according to a cut-off frequency formula, the frequency f is 1/(2 pi RC), then the cut-off frequency is 1.59K, the frequency (more than 20 KHz) of PWM output is far greater than the cut-off frequency, then a good filtering effect can be obtained, and the filtered direct-current voltage signal is supplied to an MCU control unit for detection.

The PWM output by the MCU control unit is supplied to the gate of the NMOS transistor Q1 through the inverter U1A, so that the circuit is turned on, and the sampling resistor R7 obtains the current value at that time, and then calculates the power of the load LED through the measured voltage VCC.

The MCU control unit is internally provided with a power threshold value, and the PWM pulse width is adjusted to a proper parameter through a PID algorithm to reach the set threshold value power without considering the parameters of the LED load. Since the power of the LED load at this time is detected in real time.

The resistor R3 mainly has the function of enabling the output of the U1A to be low level when the MCU is not started or the MCU fails, and the NMOS tube Q1 is in an off state to protect the LED from being damaged by impact.

The present invention is not limited to the above-mentioned preferred embodiments, and any other products in various forms can be obtained by anyone with the teaching of the present invention, but any changes in the shape or structure thereof, which have the same or similar technical solutions as the present invention, are within the protection scope.