High-power LED light source driving circuit

Abstract

The utility model provides a high-power LED light source driving circuit, which comprises a direct-current power supply, an LED driver, a charging control circuit, a current sampling resistor, a capacitor bank and a discharging control circuit, a direct-current power supply is input to the LED driver, and the LED driver is connected with the current sampling resistor and the capacitor bank in series. The capacitor bank is connected with the anode of the LED light source; the charging control circuit comprises a voltage division circuit I and a voltage comparator I, and the voltage division circuit I samples the voltage output by the LED driver; the voltage comparator I is connected with the LED driver; the LED driver judges whether the capacitor bank is charged or not; the discharge control circuit comprises a controller and a switching device, the switching device is connected to the controller, and the controller controls on and off of the switching device; when the switching device is switched on, the capacitor bank releases electricity to the light source, and the light source is turned on; large current is provided for the light source through energy storage of the capacitor bank, smooth starting of the large-power light source is guaranteed, and the problems of power consumption increase and transmission cable heating are avoided.

Description

Technical Field

[0001] This utility model relates to the field of drive circuit design, specifically to a high-power LED light source drive circuit. Background Technology

[0002] In the field of machine vision image acquisition, LED light sources play a crucial role. Appropriate lighting design allows for optimal separation of target and background information in the acquired image, significantly reducing image processing difficulty and improving processing accuracy. In LED-based visual inspection applications, LED drivers are typically integrated into the main control board of the visual inspection sensor, powered by a DC power supply, usually designed to be 24V. However, in visual inspection scenarios with large fields of view and long working distances, high-power light sources (operating voltage (32V-40V), operating current (16A-28A)) are required to meet illumination demands. In these cases, the DC power supply voltage is significantly lower than the light source's operating voltage. Directly powering the light source from the sensor's power supply will prevent it from functioning properly. Furthermore, due to the high operating current of the light source, long-distance transmission of this high current (using a 20-meter cable) can create a voltage drop of up to tens of volts across the cable, reducing the voltage reaching the sensor and causing it to malfunction. Moreover, the high current can cause severe overheating of the power cable, posing a safety hazard. Summary of the Invention

[0003] To address the aforementioned technical issues, this invention provides a high-power LED light source driving circuit. This solution utilizes an LED driver with boost function to charge a capacitor bank, and the energy stored in the capacitor bank provides a high voltage for the high-power LED light source. This avoids the problems of increased power consumption and overheating of transmission cables, and is suitable for driving high-power LED light sources in visual inspection scenarios with large field of view and long working distance.

[0004] The technical solution is as follows:

[0005] A high-power LED light source driving circuit includes: a DC power supply, an LED driver, a charging control circuit, a current sampling resistor, a capacitor bank, and a discharging control circuit;

[0006] The DC power supply is input to the LED driver, which is connected in series with a current sampling resistor and a capacitor bank for boosting the voltage and charging the capacitor bank; the capacitor bank is connected to the positive terminal of the LED light source and includes multiple capacitors connected in parallel.

[0007] The charging control circuit includes a voltage divider circuit I and a voltage comparator I. The voltage divider circuit I is connected in series between the current sampling resistor and the negative input terminal of the voltage comparator I, and is used to sample the voltage output by the LED driver, divide it, and input it to the voltage comparator I. The positive input terminal of the voltage comparator I is connected to a preset reference voltage I, and the output terminal is connected to the LED driver.

[0008] The voltage comparator I outputs a high / low level based on the comparison result between the voltage input at the negative input terminal and the preset reference voltage I; the LED driver determines whether to continue charging the capacitor bank based on the high / low level, so that the voltage of the capacitor bank after charging reaches the set voltage.

[0009] The discharge control circuit includes a controller and a switching device. The switching device includes a control terminal, an output terminal, and a ground terminal. The control terminal of the switching device is connected to the controller, and the output terminal is connected to the negative terminal of the LED light source. The controller controls the switching device to turn on and off. When the switching device is turned on, the capacitor bank releases electricity to the LED light source, and the LED light source is turned on.

[0010] Preferably, it also includes a soft-start circuit, which is connected in series between the DC power supply and the LED driver.

[0011] Furthermore, the soft-start circuit includes a resistor R1, a first NMOS transistor, a second NMOS transistor, and a voltage comparator circuit;

[0012] The resistor R1 is connected in series between the DC power supply and the LED driver;

[0013] The first NMOS transistor is connected in parallel with resistor R1, and the second NMOS transistor is connected in series between the LED driver and the voltage comparator circuit to control whether the LED driver starts to boost the voltage.

[0014] The voltage comparison circuit is connected to the first NMOS transistor and the second NMOS transistor respectively. It is used to collect the voltage between the resistor R1 and the LED driver and compare it with the preset reference voltage. Based on the comparison result, it controls the conduction and turn-off of the first NMOS transistor and the second NMOS transistor.

[0015] Furthermore, the voltage comparison circuit includes a window voltage comparison chip and its peripheral circuits. The window voltage comparison chip includes two input terminals and two output terminals. The two input terminals of the window voltage comparison chip respectively collect the voltage between resistor R1 and LED driver, and the two output terminals are respectively connected to a first NMOS transistor and a second NMOS transistor to control the conduction and turn-off of the first NMOS transistor and the second NMOS transistor respectively.

[0016] Furthermore, the voltage comparison circuit includes a voltage divider circuit II, a voltage comparator II, a voltage divider circuit III, and a voltage comparator III;

[0017] The voltage divider circuit II is connected in series between the acquisition resistor R1 and the positive input terminal of the voltage comparator II. It is used to acquire the voltage between the resistor R1 and the LED driver, divide the voltage, and input it to the voltage comparator II. The negative input terminal of the voltage comparator II is connected to the reference voltage II, and the output terminal is connected to the first NMOS transistor.

[0018] The voltage divider circuit III is connected in series between the acquisition resistor R1 and the negative input terminal of the voltage comparator III. It is used to acquire the voltage between the resistor R1 and the LED driver, divide the voltage, and input it to the voltage comparator III. The positive input terminal of the voltage comparator III is connected to the reference voltage III, and the output terminal is connected to the second NMOS transistor.

[0019] Furthermore, the switching device is a MOSFET or a transistor.

[0020] Furthermore, the LED driver includes an LED driver chip with analog dimming and boost functions and its peripheral circuitry.

[0021] Furthermore, the controller is a microcontroller or an FPGA.

[0022] This utility model has the following features:

[0023] ① This solution utilizes LED driver voltage boosting, capacitor bank energy storage, and discharge to provide a large current to the LED light source, ensuring the smooth startup of high-power LED light sources. This avoids problems such as increased power consumption and overheating of transmission cables.

[0024] ② The charging control circuit can control the set voltage for charging the capacitor bank; the discharging control circuit controls the capacitor bank to provide high voltage for the high-power LED light source.

[0025] ③ Due to the large parallel capacitor, the instantaneous charging current is too large when the power supply is directly turned on, which can easily damage the device and affect its service life. A soft start circuit was designed to suppress the surge current. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the drive circuit.

[0027] Figure 2 This is a schematic diagram of the drive circuit in a specific implementation embodiment;

[0028] Figure 3 This is a schematic diagram of one design of the soft-start circuit in a specific implementation;

[0029] Figure 4This is a schematic diagram of another design for the soft-start circuit in a specific implementation. Detailed Implementation

[0030] The technical solution of this utility model will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] A high-power LED light source driving circuit, such as Figure 1 As shown, it includes: a DC power supply, an LED driver, a charging control circuit, a current sampling resistor, a capacitor bank, and a discharging control circuit;

[0032] A DC power supply is input to the LED driver, which is connected in series with a current sampling resistor and a capacitor bank for boosting the voltage and charging the capacitor bank. The capacitor bank is connected to the positive terminal of the LED light source and consists of multiple capacitors connected in parallel.

[0033] The charging control circuit includes a voltage divider circuit I and a voltage comparator I. The voltage divider circuit I is connected in series between the current sampling resistor and the negative input terminal of the voltage comparator I. It is used to sample the voltage output by the LED driver, divide it, and then input it to the voltage comparator I. That is, the voltage divider circuit I and the voltage comparator I form negative feedback. Specifically, the input terminal of the voltage divider circuit I samples the voltage between the current sampling resistor and the capacitor bank, and the output terminal is connected to the negative input terminal of the voltage comparator I.

[0034] The positive input terminal of voltage comparator I is connected to a preset reference voltage I, and the output terminal is connected to an LED driver;

[0035] The voltage comparator I outputs a high / low level based on the comparison result between the voltage input at the negative input terminal and the preset reference voltage I; the LED driver determines whether to continue charging the capacitor bank based on the high / low level so that the voltage of the capacitor bank after charging reaches the set voltage.

[0036] The discharge control circuit includes a controller and a switching device. The switching device includes a control terminal, an output terminal, and a ground terminal. The control terminal of the switching device is connected to the controller, and the output terminal is connected to the negative terminal of the LED light source. The controller (based on the external input LED light source turn-on / off trigger signal) controls the switching device to turn on and off. When the switching device is turned on, the capacitor bank releases electricity to the LED light source, and the LED light source turns on.

[0037] In practice, the reference voltage I is set through the voltage divider resistors in the peripheral circuit of the voltage comparator I; or, as... Figure 1 As shown, the settings are configured by the controller and input to voltage comparator I.

[0038] The switching devices are MOSFETs or transistors, and the controller is a microcontroller or FPGA; for example Figure 2As shown, the controller is a microcontroller and the switching device is a MOSFET. In order to improve the switching speed of the MOSFET and reduce the switching loss, a gate driver is connected in series between the microcontroller and the MOSFET in this embodiment.

[0039] For ease of understanding, the following explanation is provided:

[0040] A voltage comparator is a circuit that compares input signals and uses the high or low level of the output voltage to represent the magnitude relationship between two input voltages.

[0041] When the voltage at the "+" input terminal is higher than that at the "-" input terminal, the voltage comparator output is high.

[0042] When the voltage at the "+" input terminal is lower than that at the "-" input terminal, the voltage comparator output is low.

[0043] A voltage divider circuit includes voltage dividing resistors and performs voltage division based on the principle of resistive voltage division to process the sampled voltage. Typically, a voltage divider circuit can divide the sampled voltage value and output a fraction of the actual voltage value.

[0044] For example, if the actual voltage of 25V becomes 2.5V after voltage division, and the voltage of a high-power LED light source is 30V, then a reference voltage I = 3V can be set. The reference voltage is then output to voltage comparator I. When the voltage sampled by voltage divider circuit I is less than or equal to 3V, voltage comparator I outputs a high level to the LED driver, controlling the LED driver to continue charging the capacitor bank. When the voltage sampled by voltage divider circuit I is greater than 3V, voltage comparator I outputs a low level to the LED driver, controlling the LED driver to stop charging the capacitor bank.

[0045] When the light source needs to be turned on, such as Figure 1 As shown, the logic controller sends a high-level signal to the switching device (MOSFET / transistor), turning it on, discharging the capacitor bank, and illuminating the light source. When using a MOSFET, a MOSFET driver is also provided to enable the MOSFET to turn on quickly.

[0046] After the capacitor bank discharges, the voltage value sampled by the voltage divider circuit I decreases and falls below the reference voltage I. The voltage comparator I outputs a high level to the LED driver, controlling the LED driver to continue charging the capacitor bank so that the capacitor bank reaches 30V, preparing for the next discharge.

[0047] In practice, the number of parallel capacitors is calculated based on the required turn-on time of the LED light source, the current magnitude, and the charging time of the capacitors.

[0048] Specifically, the amount of charge required for capacitor discharge is Q = I × t, where t represents the discharge time and I represents the discharge current. Taking t = 200 μs and I = 28 A as an example, Q = 5600 μC is calculated. According to the amount of charge Q = C * ΔV, when the voltage drops by ΔV = 1 V, C = 5600 μF is calculated.

[0049] When the capacitor is charging, the voltage drop across the capacitor is less than ΔV after the light source is turned on. ΔV = I' × Δt / C, where I' represents the charging current, Δt represents the charging time, and C represents the capacitance. Taking ΔV = 1V, Δt = 20ms, and I' = 0.782A as an example, C = 15640uF is calculated.

[0050] Therefore, the capacitance should be between 5600uF and 15640uF. This can be achieved by connecting multiple capacitors in parallel.

[0051] To avoid excessive instantaneous charging current when the power supply is directly powered on, which could damage the capacitor, as a preferred implementation method, such as... Figure 2 As shown, it also includes a soft-start circuit, which is connected in series between the DC power supply and the LED driver.

[0052] In practice, the soft-start circuit includes a resistor R1, a first NMOS transistor, a second NMOS transistor, and a voltage comparator circuit.

[0053] Resistor R1 is connected in series between the DC power supply and the LED driver; when the first NMOS transistor is off, the DC power supply is input to the LED driver through R1; when the first NMOS transistor is on, the DC power supply is input to the LED driver through the first NMOS transistor.

[0054] The first NMOS transistor is connected in parallel with resistor R1, and the second NMOS transistor is connected in series between the LED driver and the voltage comparator circuit to control whether the LED driver starts to boost the voltage.

[0055] The voltage comparison circuit is connected to the first NMOS transistor and the second NMOS transistor respectively. It is used to collect the voltage between the resistor R1 and the LED driver and compare it with the preset reference voltage. Based on the comparison result, it controls the conduction and turn-off of the first NMOS transistor and the second NMOS transistor.

[0056] In practical implementation, the voltage comparator circuit can take the following two forms:

[0057] Format 1:

[0058] like Figure 3As shown, the voltage comparison circuit includes a window voltage comparison chip and its peripheral circuits. The window voltage comparison chip includes two input terminals and two output terminals. The two input terminals of the window voltage comparison chip respectively collect the voltage between resistor R1 and LED driver, and the two output terminals are respectively connected to the first NMOS transistor and the second NMOS transistor, controlling the conduction and turn-off of the first NMOS transistor and the second NMOS transistor respectively.

[0059] For example, taking the TPS3701 chip as an example of a window voltage comparator chip, the TPS3701 chip samples the voltage between the input resistor R1 and the LED driver. When the sampled voltage is lower than the reference voltage of channel B, the output terminal B outputs a high level, controlling the second NMOS transistor to turn on; the EN enable pin of the LED driver chip (such as TPS92691-Q1) is pulled low, and the LED driver chip does not boost the voltage; conversely, when the sampled voltage is higher than the reference voltage of channel B, the output terminal B outputs a low level, controlling the second NMOS transistor to turn off, the EN enable pin of the LED driver chip (such as TPS92691-Q1) is not pulled low, and the LED driver chip starts boosting the voltage.

[0060] When the sampled voltage is lower than the reference voltage of channel A, output terminal A outputs a low level, controlling the first NMOS transistor to turn off; conversely, when the sampled voltage is higher than the reference voltage, output terminal A outputs a high level, controlling the first NMOS transistor to turn on. At this time, the DC power supply is directly input to the LED driver chip through the first NMOS transistor.

[0061] Form Two:

[0062] like Figure 4 As shown, the voltage comparison circuit includes voltage divider circuit II, voltage comparator II, voltage divider circuit III, and voltage comparator III;

[0063] Voltage divider circuit II is connected in series between the sampling resistor R1 and the positive input terminal of voltage comparator II. It is used to sample the voltage between resistor R1 and LED driver, and then input the divided voltage to voltage comparator II. Specifically, the input terminal of voltage divider circuit II samples the voltage, and the output terminal is connected to the positive input terminal of voltage comparator II.

[0064] The negative input terminal of voltage comparator II is connected to the reference voltage II, and the output terminal is connected to the first NMOS transistor. Based on the comparison result between the voltage input at the positive input terminal and the preset reference voltage II, voltage comparator II outputs a high / low level to control the first NMOS transistor to turn on and off.

[0065] Specifically, when the sampling voltage is greater than the reference voltage, the first NMOS transistor is turned on.

[0066] Voltage divider circuit III is connected in series between the sampling resistor R1 and the negative input terminal of voltage comparator III. It is used to sample the voltage between resistor R1 and LED driver, and then input the divided voltage to voltage comparator III. Specifically, the input terminal of voltage divider circuit III samples the voltage, and the output terminal is connected to the negative input terminal of voltage comparator III.

[0067] Voltage comparator III has a reference voltage III input at its positive input terminal and a second NMOS transistor connected to its output terminal. Based on the comparison result between the voltage input at its negative input terminal and the preset reference voltage III, voltage comparator III outputs a high / low level to control the second NMOS transistor's on / off state.

[0068] Specifically, when the sampled voltage is lower than the reference voltage, the voltage comparator III outputs a high level, controlling the second NMOS transistor to turn on; the EN enable pin of the LED driver chip (such as TPS92691-Q1) is pulled low, and the LED driver chip does not boost the voltage; conversely, when the sampled voltage is higher than the reference voltage, the voltage comparator III outputs a low level, controlling the second NMOS transistor to turn off; the EN enable pin of the LED driver chip (such as TPS92691-Q1) is not pulled low, and the LED driver chip starts boosting the voltage.

[0069] This design does not specify the exact model of the LED driver chip. The peripheral circuit of the chip can be directly adopted from the circuit design in the chip manual. In actual implementation, select LED driver chips with analog dimming and boost functions, such as TPS962691-Q1, LT3797, LM3409, etc.

[0070] The foregoing description of specific exemplary embodiments of this testing system is for illustrative and descriptive purposes. It is not intended to be exhaustive, nor to limit the testing system to the precise form disclosed; obviously, many changes and variations are possible in accordance with the foregoing teachings.

Claims

1. A high-power LED light source driving circuit, characterized in that, include: DC power supply, LED driver, charging control circuit, current sampling resistor, capacitor bank and discharge control circuit; The DC power supply is input to the LED driver, which is connected in series with a current sampling resistor and a capacitor bank for boosting the voltage and charging the capacitor bank; the capacitor bank is connected to the positive terminal of the LED light source and includes multiple capacitors connected in parallel. The charging control circuit includes a voltage divider circuit I and a voltage comparator I. The voltage divider circuit I is connected in series between the current sampling resistor and the negative input terminal of the voltage comparator I, and is used to sample the voltage output by the LED driver, divide it, and input it to the voltage comparator I. The voltage comparator I is input to a preset reference voltage I at its positive input terminal and its output terminal is connected to the LED driver. The voltage comparator I outputs a high / low level based on the comparison result between the voltage input at the negative input terminal and the preset reference voltage I; the LED driver determines whether to continue charging the capacitor bank based on the high / low level, so that the voltage of the capacitor bank after charging reaches the set voltage. The discharge control circuit includes a controller and a switching device. The switching device includes a control terminal, an output terminal, and a ground terminal. The control terminal of the switching device is connected to the controller, and the output terminal is connected to the negative terminal of the LED light source. The controller controls the switching device to turn on and off. When the switching device is turned on, the capacitor bank releases electricity to the LED light source, and the LED light source is turned on.

2. The high-power LED light source driving circuit as described in claim 1, characterized in that: It also includes a soft-start circuit, which is connected in series between the DC power supply and the LED driver.

3. The high-power LED light source driving circuit as described in claim 2, characterized in that: The soft-start circuit includes a resistor R1, a first NMOS transistor, a second NMOS transistor, and a voltage comparator circuit; The resistor R1 is connected in series between the DC power supply and the LED driver; The first NMOS transistor is connected in parallel with resistor R1, and the second NMOS transistor is connected in series between the LED driver and the voltage comparator circuit to control whether the LED driver starts to boost the voltage. The voltage comparison circuit is connected to the first NMOS transistor and the second NMOS transistor respectively. It is used to collect the voltage between the resistor R1 and the LED driver and compare it with the preset reference voltage. Based on the comparison result, it controls the conduction and turn-off of the first NMOS transistor and the second NMOS transistor.

4. The high-power LED light source driving circuit as described in claim 3, characterized in that: The voltage comparison circuit includes a window voltage comparison chip and its peripheral circuits. The window voltage comparison chip includes two input terminals and two output terminals. The two input terminals of the window voltage comparison chip respectively collect the voltage between resistor R1 and LED driver, and the two output terminals are respectively connected to a first NMOS transistor and a second NMOS transistor to control the conduction and turn-off of the first NMOS transistor and the second NMOS transistor.

5. The high-power LED light source driving circuit as described in claim 3, characterized in that: The voltage comparison circuit includes a voltage divider circuit II, a voltage comparator II, a voltage divider circuit III, and a voltage comparator III; The voltage divider circuit II is connected in series between the acquisition resistor R1 and the positive input terminal of the voltage comparator II. It is used to acquire the voltage between the resistor R1 and the LED driver, divide the voltage, and input it to the voltage comparator II. The negative input terminal of the voltage comparator II is connected to the reference voltage II, and the output terminal is connected to the first NMOS transistor. The voltage divider circuit III is connected in series between the acquisition resistor R1 and the negative input terminal of the voltage comparator III. It is used to acquire the voltage between the resistor R1 and the LED driver, divide the voltage, and input it to the voltage comparator III. The positive input terminal of the voltage comparator III is connected to the reference voltage III, and the output terminal is connected to the second NMOS transistor.

6. The high-power LED light source driving circuit as described in claim 1, characterized in that: The switching device is a MOSFET or a transistor.

7. The high-power LED light source driving circuit as described in claim 1, characterized in that: The LED driver includes an LED driver chip with analog dimming and boost functions and its peripheral circuitry.

8. The high-power LED light source driving circuit as described in claim 1, characterized in that: The controller is a microcontroller or an FPGA.

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