CN103108472B - Intermittent service dimming light-emitting diode (LED) lamp drive circuit - Google Patents

Abstract

The invention discloses an intermittently working dimming LED lamp drive circuit, which is arranged between an electronic transformer and an LED lamp, and includes a single-chip microcomputer, a rectifier bridge circuit, a boost circuit, an input signal detection circuit, a power supply circuit, and a main electrolytic capacitor voltage detection circuit. circuit and LED voltage detection circuit, buck step-down driving circuit and dimming signal receiving circuit, wherein, the front stage of the intermittently working dimming LED lamp driving circuit adopts a boost circuit with a fixed duty ratio, and adopts an intermittent working mode to stabilize The voltage of the main electrolytic capacitor, turning on and off the boost circuit is performed at the bottom of the low-frequency envelope of the input voltage. In this way, the electronic transformer can provide the same current to the load every time it works, which can ensure its own stable and normal operation without adding additional circuit loss. At the same time, this circuit only needs to use a relatively large electrolytic capacitor without adding additional expensive devices, and can achieve the required purpose almost without increasing the cost.

Description

Intermittent work dimming LED lamp drive circuit

technical field

The invention relates to an LED lamp driving circuit, more specifically, relates to an LED lamp driving circuit in a dimmable intermittent working mode compatible with an electronic transformer.

Background technique

At present, many LED lamps are required to be compatible with traditional power supply devices. For example, traditional halogen lamps usually use electronic transformers as power supply devices, and MR16 LED lamps that replace halogen lamps are usually also required to be compatible with electronic transformers for halogen lamps. Because MR16 spotlights The concentrated beam of light is difficult to be replaced by fluorescent lamps, so MR16 lamps using LED light sources have extremely wide demand. However, the characteristic impedance of LED lamps and traditional halogen lamps in the prior art is very different, and many problems will be caused in the process of replacing halogen lamps with LED lamps, especially the problem that is difficult to solve is that the power consumption of LED lamps is much smaller than that of traditional halogen lamps , and the electronic transformer requires a certain load current to maintain normal work, and the power consumption of the LED lamp itself is much lower than that of the halogen lamp, and the power consumption after dimming is lower. When the brightness is low, many LED lights have the problem of flickering. In order to solve this problem, some solutions are to add a parallel resistive load to the existing LED lamps to increase the overall consumption current, but this will waste electric energy, making the energy-saving advantages of replacing LED lamps meaningless.

Contents of the invention

Aiming at the problem of unstable operation, especially flickering, in the prior art when the dimmable LED lamp is connected to the electronic transformer, the purpose of the present invention is to provide an intermittently working dimming LED lamp driving circuit, which can keep the output current of the electronic transformer A certain value can work stably without adding additional power consumption circuits to reduce efficiency.

To achieve the above object, the present invention adopts the following technical solutions:

An intermittently working dimming LED lamp driving circuit is provided between an electronic transformer and an LED lamp, including:

MCU;

A rectifier bridge circuit is connected to the output terminal of the electronic transformer, and the high-speed rectifier bridge circuit is composed of a first Schottky diode, a second Schottky diode, a third Schottky diode and a fourth Schottky diode;

A boost boost circuit, the input end of which is connected to the output end of the rectifier bridge circuit, the boost boost circuit includes a second inductance, a fifth Schottky diode and a first MOS field effect transistor; the first MOS field The effect tube is connected with the microcontroller;

Input signal detection circuit, its input end is connected with the output end of described rectifier bridge circuit, described input signal detection circuit comprises the low-pass filter that is made up of first resistance and first electric capacity, and described low-pass filter is connected with single-chip microcomputer ;

A power supply circuit, the input terminal of which is connected to the output terminal of the boost voltage boosting circuit, is composed of a linear regulated power supply and a sixth resistor;

The main electrolytic capacitor voltage detection circuit and the LED voltage detection circuit, the input end of which is connected to the output end of the boost circuit, includes the main electrolytic capacitor, a voltage divider circuit for the single-chip microcomputer to measure the voltage of the main electrolytic capacitor, and a voltage divider circuit for the single-chip microcomputer to measure the main electrolytic capacitor voltage. The voltage divider circuit of the voltage difference between the electrolytic capacitor and the LED; the voltage divider circuit for the single-chip microcomputer to measure the main electrolytic capacitor voltage is composed of the second resistor and the third resistor; the voltage difference for the single-chip microcomputer to measure the main electrolytic capacitor and the LED The voltage divider circuit is composed of the fourth resistor and the fifth resistor;

buck step-down drive circuit, the input end of which is connected to the output end of the boost step-up circuit, the buck step-down drive circuit includes a third inductor, a sixth Schottky diode and a second MOS field effect transistor, the first step-down drive circuit Two MOS field effect tubes are connected to the microcontroller;

The dimming signal receiving circuit includes a phototransistor, and the phototransistor is connected to the external interrupt pin of the single-chip microcomputer;

Wherein, the front stage of the intermittently working dimming LED lamp driving circuit adopts a boost boost circuit with a fixed duty ratio, adopts an intermittent working mode to stabilize the voltage of the main electrolytic capacitor, and turns on and off the boost boost circuit at the same time as the input power voltage of the microcontroller The low-frequency envelope bottoms out.

The cut-off frequency of the low-pass filter is located between the high-frequency and low-frequency signal components output by the electronic transformer, and the high-frequency signal components are filtered out while the low-frequency is retained, and the phase and frequency of the low-frequency signal remain unchanged.

The cut-off frequency of the low-pass filter is 800Hz.

The single-chip microcomputer performs AD conversion on the analog signal output by the low-pass filter to obtain the low-frequency signal phase and frequency information of the input power supply voltage of the single-chip microcomputer, and is used to ensure that the opening and closing of the boost boost circuit is carried out at the bottom of the low-frequency signal.

The intermittent working duty cycle of the boost boost circuit is controlled by the main electrolytic voltage. When the voltage of the main electrolytic capacitor reaches the set upper limit, the boost boost circuit is allowed to be turned off, and when the main electrolytic capacitor voltage reaches the set lower limit, the boost boost circuit is allowed to be turned on. voltage circuit.

The single-chip microcomputer detects the main electrolytic capacitor voltage at the low end, and the single-chip microcomputer detects the difference between the main electrolytic capacitor voltage and the LED voltage at the low end, and the single-chip microcomputer obtains the LED voltage through calculation, and all voltage detections are low-end detections.

The power supply of the intermittently working dimming LED lamp driving circuit is obtained from the main electrolytic capacitor through the step-down of the sixth resistor by the linear regulated power supply.

The intermittently working dimming LED lamp driving circuit also includes an enhanced driving current circuit, and the enhanced driving current circuit is located between the boost voltage boosting circuit and the single-chip microcomputer or/and between the buck step-down driving circuit and the single-chip microcomputer; The enhanced driving current circuit is composed of a PNP transistor and an NPN transistor. Take the buck step-down driving circuit as an example. The buck step-down driving circuit works in voltage mode, and uses the single-chip CCP module as the driving control. The driving signal passes through the buffer circuit composed of PNP transistor and NPN transistor to the second MOS field effect transistor. gate as a control signal.

Compared with the prior art, by adopting an intermittently working dimming LED lamp drive circuit of the present invention, the electronic transformer can provide the same current to the load every time it works, which can ensure its own stable and normal work without increasing additional circuit losses. At the same time, this circuit only needs to use a relatively large electrolytic capacitor without adding additional expensive devices, and can achieve the required purpose almost without increasing the cost.

Description of drawings

Fig. 1 is a schematic diagram of an intermittently working dimming LED lamp driving circuit of the present invention;

Fig. 2 is a circuit diagram of an intermittently working dimming LED lamp driving circuit of the present invention.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Please refer to Figure 1 and Figure 2, in which the microcontroller U1 is STC12C5208AD, the linear regulated power supply U2 is 78L05, the first Schottky diode D1, the second Schottky diode D2, the third Schottky diode D3, the fourth The model of Schottky diode D4, fifth Schottky diode D5 and sixth Schottky diode D6 is SS110, the first inductance L1 is 2.2uH, the second inductance L2 is 10uH, the third inductance L3 is 47uH, the first Capacitor C1 is 10nF, second capacitor C2, third capacitor C3, fifth capacitor C5 are 1uF, main electrolytic capacitor C4 is 220uF, sixth capacitor C6 is 6.8uF, first resistor R1, third resistor R3, fifth resistor R5 is 1kΩ, the second resistor R2 is 10kΩ, the fourth resistor R4 is 8.2kΩ, the sixth resistor R6 is 2kΩ, the NPN transistors Q2 and Q5 are NPN transistors 2N5551, and the PNP transistors Q3 and Q6 are PNP transistors BC817. The first MOS field effect transistor Q4 and the second MOS field effect transistor Q7 are field effect transistors FDC5661, the photoelectric transistor Q1 is 3DU5C, and the fuse F1 is 2A.

In Figure 2, the first Schottky diode D1, the second Schottky diode D2, the third Schottky diode D3, and the fourth Schottky diode D4 form a high-speed rectifier bridge. The operating frequency of the electronic transformer is generally between 40kHZ and Between 100kHZ, the rectifier bridge composed of Schottky diodes has a high switching speed, and its performance is enough to work with the electronic transformer. The first inductor L1 and the first capacitor C1 are EMI filter elements, and the fuse F1 is a protection element. The first resistor R1 and the first capacitor C1 form a low-pass filter circuit, and the cut-off frequency of the circuit is set at 800HZ. This feature can ensure that the high-frequency signal frequency components of the electronic transformer are filtered out while retaining its low-frequency signal frequency components. The frequency component of the low-frequency signal is input to the microcontroller for AD conversion as time information. The phototransistor Q1 is connected to the external interrupt INT0 pin of the single-chip microcomputer, and the dimming signal can be sent to the single-chip microcomputer by means of an interrupt. The second inductor L2, the fifth Schottky diode D5, and the first MOS field effect transistor Q4 form a boost circuit. The NPN transistor Q2 and the PNP transistor Q3 are circuits for enhancing the driving current. The boost circuit can ensure the continuity of the input current. Therefore, the electronic transformer oscillation circuit maintains a certain current without stopping the oscillation. The drive of this stage circuit comes from the CCP module of the single-chip microcomputer, and its duty cycle is fixed, so that each working cycle can output a fixed energy to the energy storage capacitor C4. More importantly, the boost circuit with a fixed duty cycle absorbs a stable current. This feature can ensure that the output current of the electronic transformer remains consistent in each low-frequency working cycle, and the vibration will not stop due to too small current. The work of the Boost module is controlled by the voltage of the main electrolytic capacitor C4. When the voltage of the C4 capacitor drops to the set lower limit, the boost circuit starts to work before the next turn-on cycle of the electronic transformer begins. When the capacitance voltage of the main electrolytic capacitor C4 rises to the set upper limit, the boost circuit stops working. This boost circuit works in a fixed duty cycle, intermittent mode of operation, to adapt to the work of electronic transformers. The third inductor L3, the sixth Schottky diode D6, and the second MOS field effect transistor Q7 form a buck step-down circuit to supply power to the LED. The NPN transistor Q5 and the PNP transistor Q6 are circuits for enhancing the driving current. Using a buck circuit can reduce the ripple current flowing through the LED. The drive of this stage circuit also comes from the CCP module of the single-chip microcomputer, and its working mode is a continuous working mode with variable duty ratio. The duty cycle of the buck circuit in this stage is jointly determined by the dimming degree set by the user, the voltage of the main electrolytic capacitor C4 and the LED voltage. The second resistor R2 and the third resistor R3 form a voltage divider circuit to measure the voltage of the main electrolytic capacitor for the microcontroller, and the fourth R4 and fifth resistor R5 form a voltage divider circuit for the microcontroller to measure the voltage difference between the main electrolytic capacitor and the LED. The two measurements The resulting voltage difference is the LED voltage. The step-down voltage stabilization circuit composed of the sixth resistor R6 and the linear voltage stabilization power supply U2 provides a stable power supply for the entire working circuit. The function of the sixth capacitor C6 is to provide current to the single chip microcomputer when starting.

The overall operating principle of the circuit is that when power is turned on, the current charges the main electrolytic capacitor C4 through the second inductor L2 and the fifth Schottky diode D5. Due to the existence of the sixth capacitor C6, when the voltage of the main electrolytic capacitor C4 rises, the microcontroller can obtain enough voltage through the 78L05 to start the program. The program starts to work after the single-chip microcomputer is powered on. Since the measured voltage of the main electrolytic capacitor C4 is relatively low, which is lower than the minimum set value of 25V, the single-chip microcomputer will make the first MOS field effect transistor Q4 work. In order to cope with the initial stage of the program, when the main electrolytic capacitor C4 is lower than 25V, regardless of whether the output voltage of the electronic transformer reaches the bottom of the electronic transformer, the boost circuit is turned on. The backward output energy of the boost stage is greater than the maximum energy consumed by the buck circuit, that is, the LED part. The Boost stage stops working when the voltage of the main electrolytic capacitor C4 exceeds 45V, and then restarts when the voltage of the main electrolytic capacitor C4 is less than 25V. The opening time is performed at the bottom of the input voltage, and the input voltage waveform can pass the AD conversion result of the low-pass filter circuit To obtain, use this as a basis to set the opening time of boost. When the main electrolytic capacitor C4 voltage exceeds 25V, the buck circuit starts to work. The microcontroller will read the EEPROM to obtain the set brightness of the lamp and the voltage value of the LED when the power was last turned off. The Buck circuit will comprehensively set the duty ratio of the second MOS field effect transistor Q7 according to the brightness value set last time, the voltage of the main electrolytic capacitor C4 and the terminal voltage of the LED. After 2 seconds of normal operation, read the new LED voltage through the microcontroller and update it regularly, and set the duty cycle with the new LED voltage. The Buck circuit has been working continuously. During normal operation, the voltage of the main electrolytic capacitor C4 is between 25V and 45V, which can ensure the normal operation of the 78L05, and the existence of the sixth resistor R6 can protect the safety of the 78L05. The user can remotely update the brightness value of the lamp by receiving the light signal through the phototransistor Q1, and also realize standby.

Those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the purpose of the present invention, rather than as a limitation to the present invention, as long as within the scope of the present invention, the above-described embodiments All changes and modifications will fall within the scope of the claims of the present invention.

Claims (8)

1. An intermittently working dimming LED lamp driving circuit, which is located between the electronic transformer and the LED lamp, is characterized in that it includes: MCU; A rectifier bridge circuit connected to the output terminal of the electronic transformer; A boost boost circuit, the input end of which is connected to the output end of the rectifier bridge circuit, the boost boost circuit includes a second inductance, a fifth Schottky diode and a first MOS field effect transistor; the first MOS field The effect tube is connected with the microcontroller; Input signal detection circuit, its input end is connected with the output end of described rectifier bridge circuit, described input signal detection circuit comprises the low-pass filter that is made up of first resistance and first electric capacity, and described low-pass filter is connected with single-chip microcomputer ; A power supply circuit, the input terminal of which is connected to the output terminal of the boost voltage boosting circuit, is composed of a linear regulated power supply and a sixth resistor; The main electrolytic capacitor voltage detection circuit and the LED voltage detection circuit, the input end of which is connected to the output end of the boost circuit, includes the main electrolytic capacitor, a voltage divider circuit for the single-chip microcomputer to measure the voltage of the main electrolytic capacitor, and a voltage divider circuit for the single-chip microcomputer to measure the main electrolytic capacitor voltage. The voltage divider circuit of the voltage difference between the electrolytic capacitor and the LED; the voltage divider circuit for the single-chip microcomputer to measure the main electrolytic capacitor voltage is composed of the second resistor and the third resistor; the voltage difference for the single-chip microcomputer to measure the main electrolytic capacitor and the LED The voltage divider circuit is composed of the fourth resistor and the fifth resistor; buck step-down drive circuit, the input end of which is connected to the output end of the boost step-up circuit, the buck step-down drive circuit includes a third inductor, a sixth Schottky diode and a second MOS field effect transistor, the first step-down drive circuit Two MOS field effect tubes are connected to the microcontroller; The dimming signal receiving circuit includes a phototransistor, and the phototransistor is connected to the external interrupt pin of the single-chip microcomputer; Wherein, the front stage of the intermittently working dimming LED lamp driving circuit adopts a boost boost circuit with a fixed duty ratio, adopts an intermittent working mode to stabilize the voltage of the main electrolytic capacitor, and turns on and off the boost boost circuit at the same time as the input power voltage of the microcontroller The low-frequency envelope bottoms out. 2. The intermittently working dimming LED lamp drive circuit according to claim 1, characterized in that: The cut-off frequency of the low-pass filter is located between the high-frequency and low-frequency signal components output by the electronic transformer, and the high-frequency signal components are filtered out while the low-frequency is retained, and the phase and frequency of the low-frequency signal remain unchanged. 3. The intermittently working dimming LED lamp drive circuit according to claim 2, characterized in that: The cut-off frequency of the low-pass filter is 800Hz. 4. The intermittently working dimming LED lamp driving circuit according to claim 1, characterized in that: The single-chip microcomputer performs AD conversion on the analog signal output by the low-pass filter to obtain the low-frequency signal phase and frequency information of the input power supply voltage of the single-chip microcomputer, and is used to ensure that the opening and closing of the boost boost circuit is carried out at the bottom of the low-frequency signal. 5. The intermittently working dimming LED lamp drive circuit according to claim 1, characterized in that: The intermittent working duty cycle of the boost boost circuit is controlled by the main electrolytic voltage. When the voltage of the main electrolytic capacitor reaches the set upper limit, the boost boost circuit is allowed to be turned off, and when the main electrolytic capacitor voltage reaches the set lower limit, the boost boost circuit is allowed to be turned on. voltage circuit. 6. The intermittently working dimming LED lamp drive circuit according to claim 1, characterized in that: The single-chip microcomputer detects the main electrolytic capacitor voltage at the low end, and the single-chip microcomputer detects the difference between the main electrolytic capacitor voltage and the LED voltage at the low end, and the single-chip microcomputer obtains the LED voltage through calculation, and all voltage detections are low-end detections. 7. The intermittently working dimming LED lamp driving circuit according to claim 1, characterized in that: The power supply of the intermittently working dimming LED lamp driving circuit is obtained from the main electrolytic capacitor through the step-down of the sixth resistor by the linear regulated power supply. 8. The intermittently working dimming LED lamp driving circuit according to any one of claims 1 to 7, characterized in that: The intermittently working dimming LED lamp driving circuit also includes an enhanced driving current circuit, and the enhanced driving current circuit is located between the boost voltage boosting circuit and the single-chip microcomputer or/and between the buck step-down driving circuit and the single-chip microcomputer; The enhanced driving current circuit is composed of a PNP transistor and an NPN transistor.