A constant power control circuit based on MCU software control and automatic following

Abstract

The invention discloses a constant power control circuit based on MCU software control and automatic following, comprising a rectifier B, a power factor correction circuit PFC1, a resonant switch converter K, a low voltage DC conversion circuit DL3, a resonant conversion control circuit DL1, an output voltage and current control circuit DL2, an output filter energy storage capacitor C1, a current detection resistor R1, an MCU control circuit DL4, a dimming control input signal circuit DL5, an output current signal detection circuit DL6, a soft switch circuit DL7, a STB12V output circuit DL8 and a load LED. The invention adopts MCU to automatically calculate and realize current and voltage sampling and output PWM signals, and the PWM signals are provided to the output voltage and current control circuit as a reference signal source; the MCU also has multiple detection protection functions, and can realize low power standby and soft switching when lighting is not needed, so as to achieve energy saving; and realize wide range constant power output.

Description

Technical Field

[0001] The invention relates to the technical field of electric power, and in particular to a constant power control circuit based on MCU software control and automatic following. Background Art

[0002] Existing constant power technologies are roughly divided into two types. One is that a pure hardware circuit samples the output voltage and current signals, and inputs them into an op amp IC for analog calculation control to achieve constant power. The disadvantages of this circuit are complex circuit structure, multiple components, cumbersome debugging, etc., wide range constant power output is difficult to achieve, and the output constant power accuracy is poor. The second is that the hardware circuit samples the output voltage and current signals, inputs them into MCUAD for sampling, and realizes constant power through software calculation of voltage and current control reference signals written by the host computer. This technology has complex circuits, cumbersome production processes, slow constant power response speed, and expensive cost to achieve constant power. Summary of the invention

[0003] The present invention is mainly to solve the problem of the complexity of the existing constant power control circuit, and provides a constant power control circuit based on MCU software control and automatic following, adopts MCU to automatically calculate and realize current and voltage sampling and output PWM signal, PWM signal is provided to output voltage and current control circuit as reference signal source, and driver power supply automatically adjusts output voltage according to current requirement of LED lamp to meet voltage change requirement of LED lamp; MCU also has multiple detection protection function, and can realize low power standby and soft switch when lighting is not needed, so as to achieve energy saving. The present invention has simple circuit, realizes wide range constant power output, high output constant power precision and fast constant power response speed.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A constant power control circuit based on MCU software control and automatic following, comprising a rectifier B, a power factor correction circuit PFC1, a resonant switch converter K, a low-voltage DC conversion circuit DL3, a resonant conversion control circuit DL1, an output voltage and current control circuit DL2, an output filter energy storage capacitor C1, a current detection resistor R1, an MCU control circuit DL4, a dimming control input signal circuit DL5, an output current signal detection circuit DL6, a soft switch circuit DL7, an STB12V output circuit DL8 and a load LED, wherein the output end of the dimming control input signal circuit DL5 is connected to the input end of the MCU control circuit DL4, and the output end of the MCU control circuit DL4 is connected to the input end of the output voltage and current control circuit DL2. The present invention proposes a constant power control circuit based on MCU software control and automatic following, comprising a rectifier B, a power factor correction circuit PFC1, a resonant switch converter K, a low-voltage DC conversion circuit DL3, a resonant conversion control circuit DL1, an output voltage and current control circuit DL2, an output filter energy storage capacitor C1, a current detection resistor R1, an MCU control circuit DL4, a dimming control input signal circuit DL5, an output current signal detection circuit DL6, a soft switch circuit DL7, an STB12V output circuit DL8 and a load LED, wherein the input end of the rectifier B is connected to an AC power supply, the output end of the rectifier B is connected to the input end of the power factor correction circuit PFC1 and the input end of the low-voltage DC conversion circuit DL3, the output end of the power factor correction circuit PFC1 is connected to the input end of the resonant switch converter K, and the output end of the resonant switch converter K is connected to the output filter energy storage capacitor C1. C1, one end of the current sensing resistor R1 is connected to the anode of the load LED; the output end of the low-voltage DC conversion circuit DL3 is connected to the STB12V output circuit DL8, the dimming control input signal circuit DL5 and the resonant conversion control circuit DL1, and the output end of the resonant conversion control circuit DL1 is connected to the resonant switch converter K; one end of the output filter energy storage capacitor C1, the other end of the current sensing resistor R1 and the output end of the MCU control circuit DL4 are all connected to the output voltage and current control circuit DL2, and the output end of the output voltage and current control circuit DL2 is connected to the resonant conversion control circuit DL1; the other end of the current sensing resistor R1 is connected to the input end of the output current signal detection circuit DL6 and the cathode of the load LED, and the output end of the dimming control input signal circuit DL5, the output end of the soft switch circuit DL7 and the output end of the output current signal detection circuit DL6 are all connected to the MCU control circuit DL4.

[0006] This embodiment adopts AC power supply. After rectification by rectifier B, one path is converted into stable DC power of about 400V by power factor correction circuit PFC1 and output to resonant switch converter K; another path is directly output to low voltage DC conversion circuit DL3. Low voltage DC conversion circuit DL3 outputs three paths, one path supplies power to resonant conversion control circuit DL1; one path supplies power to dimming control input signal circuit DL5, and another path supplies power to external control system through independent isolated output STB12V output circuit DL8. The operation of resonant switch converter K is controlled according to output voltage and current control circuit DL2 and resonant conversion control circuit DL1. Output voltage and current control circuit DL2 adjusts output voltage and current according to reference voltage set by MCU control circuit DL4, thereby controlling current flowing through load LED. MCU control circuit DL4 also detects output related information, including output overvoltage, overtemperature of external LED module, overtemperature of power device on power board, output short circuit protection, and primary input AC undervoltage, etc. Except for short circuit protection, all protections above are to reduce output current to ensure stable operation of load LED. The MCU control circuit DL4 completes the conversion of the corresponding constant power control signal according to the control command of the dimming control input signal circuit DL5, and outputs it to the output voltage and current control circuit DL2. The dimming control input signal circuit DL5 can also output a dimming signal, and control the MCU control circuit DL4 in the dimming mode. The MCU control circuit DL4 converts the dimming signal into a PWM signal and transmits it to the output voltage and current control circuit DL2 to achieve the dimming function.

[0007] Preferably, the input end of the rectifier B is connected to an AC power source, and the output end of the rectifier B is connected to the input end of the power factor correction circuit PFC1 and the input end of the low-voltage DC conversion circuit DL3; the output end of the power factor correction circuit PFC1 is connected to the input end of the resonant switch converter K, and the output end of the resonant switch converter K is connected to the output filter energy storage capacitor C1, one end of the current detection resistor R1 and the anode of the load LED. The present invention adopts an AC power supply, and after rectification by the rectifier B, one path is converted into a stable DC power of about 400V by the power factor correction circuit PFC1, and output to the resonant switch converter K; the other path is output to the low-voltage DC conversion circuit DL3.

[0008] Preferably, the output end of the low voltage DC conversion circuit DL3 is connected to the STB12V output circuit DL8, the dimming control input signal circuit DL5 and the resonant conversion control circuit DL1, and the output end of the resonant conversion control circuit DL1 is connected to the resonant switch converter K. The low voltage DC conversion circuit DL3 outputs three paths, one path supplies power to the resonant conversion control circuit DL1; one path supplies power to the dimming control input signal circuit DL5; and the other path supplies power to the external control system through the STB12V output circuit DL8 with independent isolated output. The present invention controls the operation of the resonant switch converter K according to the output voltage and current control circuit DL2 and the resonant conversion control circuit DL1.

[0009] Preferably, one end of the output filter energy storage capacitor C1 is connected to the output voltage and current control circuit DL2, and the output end of the output voltage and current control circuit DL2 is connected to the resonant conversion control circuit DL1.

[0010] Preferably, the other end of the current sensing resistor R1 is connected to the input end of the output voltage and current control circuit DL2 , the input end of the output current signal detection circuit DL6 , and the cathode of the load LED.

[0011] Preferably, the output end of the soft on / off circuit DL7 and the output end of the output current signal detection circuit DL6 are both connected to the MCU control circuit DL4.

[0012] Preferably, the MCU control circuit DL4 includes a chip MU1, wherein the pin 17 of the chip MU1 is used for output undervoltage and short circuit protection, and the pin 11 of the chip MU1 is used for output overvoltage protection. The pin 17 of MU1 is used for output undervoltage and short circuit protection and is connected to an optocoupler. When MU1 is powered on, the pin 17 is synchronized to a high level and preferably maintains 500mS-1S; the low level of the pin 17 is effective, and the conversion is controlled by the pin 19. When the voltage of the pin 19 is lower than the set value, the pin 17 drops to a low level, and the reaction is less than 1uS. When 12VVDD rises to a certain value, the pin 19 controls the state change of the pin 17. Pin 19 of MU1 is connected to the output undervoltage and short-circuit detection circuit. In the output undervoltage and short-circuit detection circuit, resistors R27, R68, R206, and R207 form a minimum maintenance voltage circuit, and diode D31 and resistor R205 form a reverse isolation circuit. V+ is connected to the output end. When the output end is undervoltage or short-circuited, the intersection voltage of resistors R206 and R207 is pulled down by the output end by diodes D31, R205, and R27. When the intersection voltage is lower than the set value, pin 17 of MCU becomes low level. Since pin 17 of MU1 is connected to pin 2 of integrated diode D36, diode OP4A of optocoupler OP4 is turned on, and phototransistor OP4B turns off the primary resonant switch power supply to achieve the protection purpose. Pin 11 of MU1 is used for output overvoltage protection. After MU1 is powered on, when the power output is unloaded or normally loaded, pin 11 is high level, and the state conversion of pin 11 is controlled by pin 6. The output overvoltage protection shares an optocoupler with the output undervoltage and short-circuit protection. The output V+ is connected to resistors R35, R143, and R144 in sequence for voltage division and then connected to pin 6 of MU1. When the voltage signal at pin 6 is higher than the set value, pin 11 is converted to a low level within 1uS. Pin 11 of MU1 is connected to pin 1 of the integrated diode D36. The current of OP4A flows from pin 11 of MU1 to the negative pole of MU1 through the integrated diode D36. OP4B turns off the primary resonant switch power supply to achieve the protection purpose.

[0013] Preferably, when the input signal of pin 1 of the chip MU1 is higher than a preset value, the output signal of pin 13 of the chip MU1 changes accordingly with the input signal of pin 14 of the chip MU1. Pin 1 of MU1 has two detection functions. First, when the voltage signal of pin 1 is lower than the set value, pin 2 becomes low level to ensure that the current of the optocoupler reaches the negative pole; second, when the potential of pin 1 is lower than the preset value, the change of pin 13 needs to be terminated. Regardless of the potential signal of pin 14, as long as the potential of pin 1 is lower than the preset value, the output signal (PWM signal) of pin 13 no longer changes with the input signal of pin 14, that is, the information of the previous state of pin 14 is locked, which not only ensures the reference voltage required for constant power, but also takes into account the closing function of the minimum signal during dimming.

[0014] Preferably, the output voltage and current control circuit DL2 includes a resistor R158 and a chip U12, one end of the resistor R158 is connected to the reference voltage +2.5V, and the other end of the resistor R158 is connected to the 6th pin of the chip U12 after being connected to the resistor R159 for voltage division. Because the isolation diode D27 of the voltage and current loop reference circuit has a certain conduction voltage difference, the voltage signal of the current detection input needs to be appropriately raised according to the voltage drop of the isolation diode D27 to achieve deep dimming.

[0015] Preferably, the output voltage and current control circuit DL2 further includes a resistor R164 and a resistor R165, and a current reference input CB point is set between the resistor R164 and the resistor R165, and the CB point is connected to the output end of the voltage and current loop reference circuit. In the voltage and current loop reference circuit, the resistor R191, the capacitor C102, the resistor R192, the capacitor C111, the resistor R171, the capacitor C112, and the resistor R210 form an RC rectifier circuit, and the +5V voltage is connected to the CB point of the output voltage and current control circuit DL2 through the RC rectifier circuit, and is connected to the 5th pin of the chip U12 after voltage division, and is set as the current loop reference voltage.

[0016] Therefore, the advantages of the present invention are:

[0017] (1) The driver voltage can be automatically adjusted over a wide range by simply setting the current according to the number of LED lamps in parallel;

[0018] (2) The constant power control circuit is simple and does not require a multi-unit analog operational amplifier combination, which reduces the application of components and improves the reliability of device use;

[0019] (3) Multiple protection circuits are highly integrated into one MCU control, further reducing the use of detection circuits, following the design principle of fewer components and more reliability, and improving reliability;

[0020] (4) External programmable expansion is strong. Through the dimming control input signal circuit DL5, other functions can be realized by slightly changing it, such as one-key offline programming function;

[0021] (5) It has communication function, and can realize brightness adjustment, current adjustment when LED lights are lit, enable or disable functions through corresponding commands;

[0022] (6) When lighting is not needed, low-power standby and soft switching can be achieved to achieve energy saving;

[0023] (7) Achieve wide range constant power output, high output constant power accuracy, and fast constant power response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1The present invention is a schematic diagram of a constant power control circuit based on MCU software control and automatic following in an embodiment of the present invention.

[0025] Figure 2 4 is a schematic diagram of the output voltage and current control circuit DL2 in an embodiment of the present invention.

[0026] Figure 3 It is a schematic diagram of the MCU control circuit DL4 in an embodiment of the present invention.

[0027] Figure 4 4 is a schematic diagram of a voltage-current loop reference circuit in an embodiment of the present invention.

[0028] Figure 5 It is a schematic diagram of a current sampling signal amplifying circuit in an embodiment of the present invention.

[0029] Figure 6 4 is a schematic diagram of a dimming control input signal circuit DL5 in an embodiment of the present invention.

[0030] Figure 7 1 is a schematic diagram of an output undervoltage and short-circuit detection circuit in an embodiment of the present invention.

[0031] Figure 8 It is a schematic diagram of an output undervoltage, short circuit and overvoltage protection circuit in an embodiment of the present invention.

[0032] Fig. 9 is a schematic diagram of an external LED temperature detection circuit in an embodiment of the present invention.

[0033] Fig.10 4 is a schematic diagram of an internal system temperature detection circuit in an embodiment of the present invention.

[0034] Fig.11 It is a schematic diagram of a low power consumption control circuit in an embodiment of the present invention.

[0035] Fig.12 It is a standard data table of MCU signal acquisition and corresponding output PWM in the implementation of the present invention. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0037] like Figure 1As shown, a constant power control circuit based on MCU software control and automatic following includes a rectifier B, a power factor correction circuit PFC1, a resonant switch converter K, a low-voltage DC conversion circuit DL3, a resonant conversion control circuit DL1, an output voltage and current control circuit DL2, an output filter energy storage capacitor C1, a current detection resistor R1, an MCU control circuit DL4, a dimming control input signal circuit DL5, an output current signal detection circuit DL6, a soft switch circuit DL7, a STB12V output circuit DL8 and a load LED, wherein the input end of the rectifier B is connected to an AC power supply, the output end of the rectifier B is connected to the input end of the power factor correction circuit PFC1 and the input end of the low-voltage DC conversion circuit DL3, the output end of the power factor correction circuit PFC1 is connected to the input end of the resonant switch converter K, and the output end of the resonant switch converter K is connected to the output filter energy storage capacitor C1. , one end of the current sensing resistor R1 is connected to the anode of the load LED; the output end of the low-voltage DC conversion circuit DL3 is connected to the STB12V output circuit DL8, the dimming control input signal circuit DL5 and the resonant conversion control circuit DL1, and the output end of the resonant conversion control circuit DL1 is connected to the resonant switch converter K; one end of the output filter energy storage capacitor C1, the other end of the current sensing resistor R1 and the output end of the MCU control circuit DL4 are all connected to the output voltage and current control circuit DL2, and the output end of the output voltage and current control circuit DL2 is connected to the resonant conversion control circuit DL1; the other end of the current sensing resistor R1 is connected to the input end of the output current signal detection circuit DL6 and the cathode of the load LED, and the output end of the dimming control input signal circuit DL5, the output end of the soft switch circuit DL7 and the output end of the output current signal detection circuit DL6 are all connected to the MCU control circuit DL4.

[0038] This embodiment adopts AC power supply. After rectification by rectifier B, one path is converted into stable DC power of about 400V by power factor correction circuit PFC1 and output to resonant switch converter K; another path is directly output to low voltage DC conversion circuit DL3. Low voltage DC conversion circuit DL3 outputs three paths, one path supplies power to resonant conversion control circuit DL1; one path supplies power to dimming control input signal circuit DL5, and another path supplies power to external control system through independent isolated output STB12V output circuit DL8. The operation of resonant switch converter K is controlled according to output voltage and current control circuit DL2 and resonant conversion control circuit DL1. Output voltage and current control circuit DL2 adjusts output voltage and current according to reference voltage set by MCU control circuit DL4, thereby controlling current flowing through load LED. MCU control circuit DL4 also detects output related information, including output overvoltage, overtemperature of external LED module, overtemperature of power device on power board, output short circuit protection, and primary input AC undervoltage, etc. Except for short circuit protection, all protections above are to reduce output current to ensure stable operation of load LED. The MCU control circuit DL4 completes the conversion of the corresponding constant power control signal according to the control command of the dimming control input signal circuit DL5, and outputs it to the output voltage and current control circuit DL2. The dimming control input signal circuit DL5 can also output a dimming signal, and control the MCU control circuit DL4 in the dimming mode. The MCU control circuit DL4 converts the dimming signal into a PWM signal and transmits it to the output voltage and current control circuit DL2 to achieve the dimming function.

[0039] like Figure 2As shown, the output voltage and current control circuit DL2 includes a chip U12, and the 8th pin of the chip U12 is connected to an independent power supply; a resistor R159 is connected to the 6th pin of the chip U12 to realize the current detection input; a resistor R151 is connected in parallel with a resistor R152 and then connected in series with a resistor R149 and a resistor R148 to form a voltage divider circuit, and a lower voltage is formed at one end of the resistor R149 and sent to the 2nd pin of the chip U12 for detecting the output voltage; a resistor R161 and a capacitor C90 are connected in series with the 2nd pin and the 1st pin of the chip U12 to form a negative feedback; Resistor R157 and capacitor C83 are connected in series to pins 6 and 7 of chip U12, and capacitor C84 is connected between pins 6 and 7 of chip U12 to play an integrating role; one end of resistor R158 is connected to the reference voltage +2.5V, and is connected to pin 6 of chip U12 after voltage division with resistor R159, raising the current signal reference value to achieve deep dimming (because the isolation diode D27 of the voltage and current loop reference circuit has a certain conduction voltage difference, so the voltage signal of the current detection input needs to be appropriately raised according to the voltage drop of the isolation diode D27). Resistor R163, resistor R164, resistor R165, resistor R166, resistor R229 and CVR1 form a resistor network under the current reference voltage division setting, which is connected to capacitor C87 to filter out noise and then connected to pin 5 of chip U12. Between resistor R164 and resistor R165 is the current reference input CB point, which is connected to the output end of the voltage and current loop reference circuit, such as Figure 4 As shown in the voltage and current loop reference circuit, resistor R191, capacitor C102, resistor R192, capacitor C111, resistor R171, capacitor C112, and resistor R210 form an RC rectifier circuit. The +5V voltage is connected to the RC rectifier circuit. Figure 2 The CB point in the circuit is connected to the 5th pin of the chip U12 after voltage division, and is set as the reference voltage of the current loop; the resistors R160 and R222 are the voltage and current loop reference setting resistors used for debugging when the MCU is not powered on, and will be removed after debugging. CVREF is the reference signal input of the MCU voltage loop, the resistor R156 supplies power to OP3A, and the diode D25 is an integrated diode, which is connected to the 1st pin of the voltage control loop of the chip U12 and to the 7th pin of the chip U12 through the resistor R154 to form a current control loop. The voltage control loop and the current control loop form a feedback circuit, which acts on the resonant conversion control circuit DL1.

[0040] like Figure 3As shown, the MCU control circuit DL4 includes a chip MU1 (MCU), which realizes PWM changes accordingly with the input signal. Pin 17 of MU1 is used for output undervoltage and short-circuit protection and is connected to an optocoupler. When MU1 is powered on, pin 17 is synchronized to a high level and is preferably maintained for 500mS-1S; pin 17 is valid at a low level, and the conversion is controlled by pin 19. When the voltage of pin 19 is lower than the set value, pin 17 drops to a low level, and the reaction is less than 1uS. When 12VVDD rises to a certain value, pin 19 controls the state change of pin 17. Pin 19 of MU1 is connected to the output undervoltage and short-circuit detection circuit, as shown in Figure 7 As shown in the output undervoltage and short-circuit detection circuit, resistors R27, R68, R206 and R207 form a minimum maintenance voltage circuit, diode D31 and resistor R205 form a reverse isolation circuit, V+ is connected to the output end, when the output end is undervoltage or short-circuited, the intersection node voltage of resistors R206 and R207 is pulled down by the output end by diode D31, resistor R205 and resistor R27. When the intersection node voltage is lower than the set value, pin 17 of the MCU becomes a low level, as shown in FIG. Figure 8 As shown, the 17th foot of MU1 is connected to the 2nd foot of the integrated diode D36, the diode OP4A of the optical coupler OP4 is turned on, and the phototransistor OP4B turns off the primary resonant switch power supply to achieve the protection purpose.

[0041] Pin 10 of MU1 is used for soft switch control. It is high level when powered on and in normal state. The working state of pin 10 is controlled by pin 3 of MU1. Pin 3 is high level when the whole system is working normally. When pin 3 receives the shutdown signal and is pulled to low level, pin 10 also becomes low level, and the current of the optocoupler flows from MU1 to the negative pole through pin 10. Fig.11 As shown, OP2A is turned on and starts working, OP2B acts to lower the voltage of the control electrode of Q20, Q8 disconnects the primary side VDD, stops supplying power to the resonant conversion control circuit DL1, and the power supply stops working, thereby achieving low power standby.

[0042] Pin 11 of MU1 is used for output overvoltage protection. After MU1 is powered on, when the power supply output is unloaded or normally loaded, pin 11 is high level, and the state transition of pin 11 is controlled by pin 6. Figure 8 As shown, the output overvoltage protection shares an optocoupler with the output undervoltage and short-circuit protection. The output V+ is connected to resistors R35, R143, and R144 in sequence for voltage division and then connected to pin 6 of MU1. When the voltage signal at pin 6 is higher than the set value, pin 11 is converted to a low level within 1uS, and pin 11 of MU1 is connected to pin 1 of the integrated diode D36. The current of OP4A flows from pin 11 of MU1 to the negative pole of MU1 through the integrated diode D36. OP4B turns off the primary resonant switch power supply to achieve the protection purpose.

[0043] Pin 1 of MU1 is used to detect the lowest dimming. After MU1 is powered on, when the voltage signal of pin 1 is higher than the set value, pin 2 outputs a high level. When the signal of pin 1 is lower than the set value, pin 2 becomes a low level, and the current of the optocoupler diode flows from pin 2 of MU1 to the negative pole of MU1. Fig.11 As shown, OP2A turns on another diode of the integrated diode D37, so that when the voltage is lower than the minimum dimming point, the entire power system is turned off and the system enters the standby mode with the lowest power consumption, thus meeting the energy saving requirements. Pin 1 of MU1 has two detection functions. First, when the voltage signal of pin 1 is lower than the set value, pin 2 becomes low level to ensure that the current of the optocoupler reaches the negative pole; second, when the potential of pin 1 is lower than the preset value, the change of pin 13 needs to be terminated. Regardless of the potential signal of pin 14, as long as the potential of pin 1 is lower than the preset value, the output signal (PWM signal) of pin 13 will no longer change with the input signal of pin 14, that is, the information of the previous state of pin 14 is locked, which not only ensures the reference voltage required for constant power, but also takes into account the shutdown function of the lowest signal during dimming.

[0044] The focus of this embodiment is constant power control, which is specifically implemented as follows: MU1's 14-pin ISET is used to sample the main input signal, and is connected to the current sampling signal amplifier circuit. When the signal is input, the corresponding PWM is output from pin 13, and the PWM output accuracy error is less than 5%. The output PWM amplitude is 5V, which is also controlled by pin 1. The voltage signal input to pin 1 must be greater than the preset value. When it is lower than the preset value, the output PWM remains in the previous state. The specific implementation is as follows Figure 5 As shown, the current reference input CB point signal is connected to the positive terminal of U13B by resistor R162 for amplification. The current signal setting of CB point is Figure 2 The resistors R164, R165, R166, R229, CVR1 and Figure 4 The resistors R191, R192, R171, R210, C112, C111, C102 and other resistors and capacitors of the voltage and current loop reference circuit are determined by the gain. Figure 5 The resistors R30, R202 and R29 of the (current sampling signal amplifier circuit) are determined. The resistors R203, R204 and R208 are used for differential compensation and filtering interference signals. The output signal of the 7-pin of the operational amplifier U13B is filtered by the resistor R183 and the capacitor C101 and then transmitted to the 14-pin of MU1. The 13-pin of MU1 outputs the signal according to the 14-pin input signal as shown below: Fig.12 The corresponding PWM signal shown in the figure is rectified and filtered by resistor R178, resistor R177, resistor R141, capacitor C49 and capacitor C123 and then output to Figure 2Pin 3 of U12 of (output voltage and current control circuit DL2) changes the voltage loop reference, thereby achieving the purpose of changing the output voltage to achieve constant power. In addition, when the input voltage signal of pin 1 is lower than the preset value, the output of pin 13 maintains the normal state corresponding to the current pin 14, that is, when a certain voltage signal is input to pin 14, the corresponding PWM duty cycle needs to be maintained, and the output PWM signal does not change with the change of the ISET signal input to pin 14; when the input voltage signal of pin 1 is higher than the preset value, the output signal (PWM signal) of pin 13 changes accordingly with the input information of pin 14.

[0045] Pin 5 of MU1 is connected to the internal system temperature detection circuit, such as Fig.10 As shown in the figure, in the internal system temperature detection circuit, resistors R176, R179 and NTC2 form a voltage divider circuit. When the resistance of NTC2 decreases with the increase of temperature, the voltage at the voltage divider point (i.e., the input voltage of MU1's 5th pin) is lower than the set value, MU1's 15th pin outputs a high level of about the MCU power supply VDD, which Figure 2 Q29 on the pin is turned on, and the resistor R163 is divided by Q29 to the ground. The voltage signal at the CB point is pulled down by a certain proportion, reducing the output current; when the input voltage at pin 5 is higher than the set value, pin 15 returns to a low level of 0V, Q29 turns off the resistor, and the resistor R163 is left floating and does not participate in the voltage division. The voltage at the CB point is the set value, and the output current works normally.

[0046] Pin 20 of MU1 is connected to an external LED temperature detection circuit, such as Fig. 9 As shown in the figure, in the external LED temperature detection circuit, resistors R34, R71 and NTC1 form a voltage divider circuit. When the resistance of NTC1 decreases with the increase of temperature, when the voltage at the voltage divider point (i.e. the input voltage of MU1's 20-pin) is lower than the set value, MU1's 15-pin outputs a high level of about the MCU power supply VDD, which Figure 2 Q29 on the pin is turned on, and the resistor R163 is divided by Q29 to the ground. The voltage signal at the CB point is pulled down by a certain proportion, reducing the output current; when the input voltage at pin 20 is higher than the set value, pin 15 returns to a low level of 0V, Q29 is turned off, and the resistor R163 is left suspended and does not participate in the voltage division. The voltage at the CB point is the preset value, and the output current works normally.

[0047] like Figure 4 As shown in the voltage and current loop reference circuit, the upper end of resistor R191 is connected to the reference voltage +5V, and the lower end is connected to capacitor C102 for filtering. Resistors R192, R171, and R210 are connected in series, and capacitors C111 and C112 form an RC rectifier circuit. The output is connected to Figure 2 The output voltage and current control circuit DL2 has a CB point, and one end of the resistor R191 is also connected to a diode D27, and the cathode of the diode D27 is connected to Figure 6At the DIM terminal of the dimming control input signal circuit DL5, when the voltage at the DIM terminal is higher than the node voltage of the resistors R191 and R192, the diode D27 is cut off, and the voltage at the CB terminal provides a current reference signal to the 5th pin of U12 according to the set value, and the power supply outputs a constant current according to the set value; when the voltage at the DIM terminal is lower than the node voltage of the resistors R191 and R192, the diode D27 proportionally pulls down the node voltage, thereby reducing the reference voltage at the CB point, and reducing the output current according to IO=Vcb / Rsen, thereby achieving the purpose of dimming.

[0048] like Figure 5 As shown, the current sampling signal amplifier circuit not only amplifies weak current signals, but also has the function of anti-interference and improving output accuracy. When the dimming brightness is very low, the signal at the CB point is very low. Because the detection resolution of MU1 is weak, an amplifier is used to amplify the signal to a certain extent. The voltage signal at the CB point is connected by resistor R162, and the amplification factor is determined by resistors R30, R202, and R29. A reference signal is connected to resistors R208, R204, and R203 to form a differential compensation circuit to improve the accuracy of the amplifier circuit. The 7th pin of U13B outputs the amplified voltage signal ISET to the 14th pin of MU1. MU1 adjusts the output corresponding PWM signal according to this signal.

[0049] like Figure 6 As shown, in the dimming control input signal circuit DL5, OP5 is a photoelectric isolation device, resistor R168 is connected to the external PWM dimming signal, one end of resistor R169 is connected to the +5V reference voltage, and the other end is connected to the negative electrode of D27 after being connected in series with resistor R172. Resistor R172 is used to fine-tune the correction signal ratio, capacitor C97 and capacitor C98 are used to filter out noise, and U14 and R170 modulate the 12V voltage into a 2.5V reference for the subsequent stage as a voltage reference.

Claims

1. A constant power control circuit based on MCU software control and automatic following, characterized in that: The invention comprises a rectifier B, a power factor correction circuit PFC1, a resonant switch converter K, a low voltage DC conversion circuit DL3, a resonant conversion control circuit DL1, an output voltage and current control circuit DL2, an output filter energy storage capacitor C1, a current detection resistor R1, an MCU control circuit DL4, a dimming control input signal circuit DL5, an output current signal detection circuit DL6, a soft switch circuit DL7, an STB12V output circuit DL8 and a load LED, wherein the output end of the dimming control input signal circuit DL5 is connected to the input end of the MCU control circuit DL4, and the output end of the MCU control circuit DL4 is connected to the output voltage and current control circuit DL6. The MCU control circuit DL4 is connected to the input end of the circuit DL2; the MCU control circuit DL4 completes the conversion of the corresponding constant power control signal according to the control command of the dimming control input signal circuit DL5, and outputs it to the output voltage and current control circuit DL2; the MCU control circuit DL4 converts the dimming signal output by the dimming control input signal circuit DL5 into a PWM signal and transmits it to the output voltage and current control circuit DL2 to achieve the dimming function; the MCU control circuit DL4 integrates multiple protection circuits, and the MCU control circuit DL4 includes a chip MU1, and the 17th pin of the chip MU1 is used for output undervoltage and short-circuit protection, and the 11th pin of the chip MU1 is used for output overvoltage protection.

2. A constant power control circuit based on MCU software control automatic following according to claim 1, characterized in that: The input end of the rectifier B is connected to an AC power supply, and the output end of the rectifier B is connected to the input end of the power factor correction circuit PFC1 and the input end of the low-voltage DC conversion circuit DL3; the output end of the power factor correction circuit PFC1 is connected to the input end of the resonant switching converter K, and the output end of the resonant switching converter K is connected to the output filter energy storage capacitor C1, one end of the current sensing resistor R1 and the anode of the load LED.

3. A constant power control circuit based on MCU software control and automatic following according to claim 1, characterized in that: The output end of the low voltage DC conversion circuit DL3 is connected to the STB12V output circuit DL8, the dimming control input signal circuit DL5 and the resonant conversion control circuit DL1, and the output end of the resonant conversion control circuit DL1 is connected to the resonant switching converter K.

4. A constant power control circuit based on MCU software control automatic following according to claim 1, characterized in that: One end of the output filter energy storage capacitor C1 is connected to the output voltage and current control circuit DL2 , and the output end of the output voltage and current control circuit DL2 is connected to the resonant conversion control circuit DL1 .

5. A constant power control circuit based on MCU software control automatic following according to claim 2, characterized in that: The other end of the current detection resistor R1 is connected to the input end of the output voltage and current control circuit DL2 , the input end of the output current signal detection circuit DL6 , and the cathode of the load LED.

6. A constant power control circuit based on MCU software control and automatic following according to claim 1, characterized in that: The output end of the soft on / off circuit DL7 and the output end of the output current signal detection circuit DL6 are both connected to the MCU control circuit DL4.

7. A constant power control circuit based on MCU software control and automatic following according to claim 1, characterized in that: Pin 19 of chip MU1 is connected to the output undervoltage and short circuit detection circuit; pin 5 of chip MU1 is connected to the internal system temperature detection circuit; and pin 20 of chip MU1 is connected to the external LED temperature detection circuit.

8. A constant power control circuit based on MCU software control and automatic following according to claim 7, characterized in that: Pin 1 of the chip MU1 is used to detect the lowest dimming. When the input signal of pin 1 of the chip MU1 is higher than the preset value, the output signal of pin 13 of the chip MU1 changes accordingly with the input signal of pin 14 of the chip MU1. When the input signal at the pin 1 of the chip MU1 is lower than a preset value, the output signal at the pin 13 of the chip MU1 no longer changes correspondingly with the input signal at the pin 14 of the chip MU1.

9. A constant power control circuit based on MCU software control and automatic following according to claim 1, characterized in that: The output voltage and current control circuit DL2 includes a resistor R158 and a chip U12. One end of the resistor R158 is connected to a reference voltage +2.5V, and the other end of the resistor R158 is connected to a resistor R159 and then to pin 6 of the chip U12.

10. A constant power control circuit based on MCU software control and automatic following according to claim 1 or 9, characterized in that: The output voltage and current control circuit DL2 further includes a resistor R164 and a resistor R165 , a current reference input point CB is set between the resistor R164 and the resistor R165 , and the CB point is connected to the output end of the voltage and current loop reference circuit.

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