High-efficiency LED lamp driving power supply with controllable pulse energy

Abstract

The invention discloses a pulse energy controllable high-efficiency LED lamp driving power supply, which comprises an LED lamp driving power supply, the LED lamp driving power supply comprises a Buck main power loop, an LED, a differential amplification circuit and a digital signal processor DSP, the PWM end pin of the digital signal processor DSP is connected with one end of the Buck main power loop, the other end of the Buck main power loop is connected with one end of the LED, and the other end of the LED is connected with the other end of the differential amplification circuit. According to the invention, DEMPT control and PID control are combined, a DEMPT-PID control mode is provided, the rise time of output LED current is shortened, so that the pulse light period and the duty ratio adjustable range are improved, and meanwhile, the control mode is switched into PID control, so that low-frequency oscillation caused by DEMPT control is eliminated, the stability of LED current is improved, and current ripples are reduced; on the basis of meeting the rising time of the output current, the overshoot is suppressed, and the influence of low-frequency ripples generated by the DEMPT mode in a steady state is avoided by switching to the PID control mode.

Description

Technical Field

[0001] The present invention relates to the technical field of LED lamp drive power supplies, and specifically provides a high-efficiency LED lamp drive power supply with controllable pulse energy. Background Art

[0002] As the fourth-generation electric light source, light-emitting diodes have the advantages of high efficiency, cold light source, pure light quality, high adjustability, etc. compared with past electric light sources such as high-pressure sodium lamps and fluorescent lamps, making LEDs widely concerned and applied in various industries.

[0003] Common LED dimming methods are divided into analog dimming and PWM dimming. Analog dimming controls the forward voltage of the LED, adjusts the LED current, and outputs continuous light. PWM dimming is achieved by connecting the dimming switch in series or parallel with the LED, using a PWM signal to drive the dimming switch, and changing the duty cycle of the PWM signal to adjust the average value of the LED drive current. The LED actually operates in a pulsed state.

[0004] The adopted PWM dimming method cannot directly adjust the instantaneous value I of the pulsed current. ref , and it is necessary to additionally adjust the V of the pre-stage drive power supply. OUT or I. OUT , a single-tube Buck circuit is used to directly drive the LED. The duty cycle of the Buck circuit switch tube is controlled in the bright area to adjust the instantaneous value I of the current. ref , and the switch tube is turned off in the dark area to ensure accurate adjustment of the pulsed current and reduce the cost of the driver at the same time.

[0005] However, traditional LED lamp drive power supplies have the following disadvantages:

[0006] Although the DEMPT control method can suppress the starting overshoot of the PT control, compared with the PID control, the output ripple in the steady state is still large, and since the preset pulses of different energy levels cannot be changed, the adjustable range of the output voltage is limited and cannot meet people's usage requirements. Summary of the Invention

[0007] The purpose of the present invention is to provide a high-efficiency LED lamp drive power supply with controllable pulse energy to solve the problem that although the DEMPT control method can suppress the starting overshoot of the PT control, compared with the PID control, the output ripple in the steady state is still large, and since the preset pulses of different energy levels cannot be changed, the adjustable range of the output voltage is limited and cannot meet people's usage requirements as mentioned in the above background art.

[0008] To achieve the above object, the present invention provides the following technical solution: A high-efficiency LED lamp drive power supply with controllable pulse energy, including an LED lamp drive power supply. The LED lamp drive power supply includes a Buck main power circuit, an LED, a differential amplifier circuit, and a digital signal processor DSP. The PWM pin of the digital signal processor DSP is connected to one end of the Buck main power circuit. The other end of the Buck main power circuit is connected to one end of the LED. The other end of the LED is connected to one end of the differential amplifier circuit. The other end of the differential amplifier circuit is connected to the AD pin of the digital signal processor DSP.

[0009] As a preferred technical solution of the present invention, the Buck main power circuit includes a DC power supply DC, a switching transistor Q, a freewheeling diode D, a filter inductor L, an output filter capacitor C, and a current sampling resistor R1. One end of the DC power supply DC is respectively connected to one end of the freewheeling diode D and one end of the output filter capacitor C. The other end of the DC power supply DC is connected to the source electrode of the switching transistor Q. The drain electrode of the switching transistor Q is respectively connected to the other end of the freewheeling diode D and one end of the filter inductor L. The other end of the filter inductor L is respectively connected to the other end of the output filter capacitor C and one end of the current sampling resistor R1. The other end of the current sampling resistor R1 and the surface of the output filter capacitor C are both connected to the LED. The gate electrode of the switching transistor Q is connected to the PWM terminal of the digital signal processor DSP.

[0010] As a preferred technical solution of the present invention, the LED includes an equivalent diode D LED , an equivalent DC source V F , and an equivalent resistor R LED . One end of the equivalent DC source V F is connected to one end of the equivalent diode D LED . The other end of the equivalent DC source V F is connected to one end of the equivalent resistor R LED . The other end of the equivalent diode D LED and the other end of the equivalent resistor R LED are both connected to the Buck main power circuit. The connection point of the equivalent resistor R LED and the Buck main power circuit is connected to the differential amplifier circuit.

[0011] As a preferred technical solution of the present invention, the differential amplifier circuit includes a resistor R2, a resistor R3, a resistor R4, a resistor R5, and an amplifier. The negative terminal pins of the amplifier are respectively connected to one end of the resistor R2 and one end of the resistor R3. The other end of the resistor R3 is connected to the output terminal of the amplifier. The positive terminal pins of the amplifier are respectively connected to one end of the resistor R5 and one end of the resistor R4. The other end of the resistor R5 is grounded. The other end of the resistor R4 is connected to the LED. The output terminal of the amplifier is connected to the AD terminal of the digital signal processor DSP.

[0012] As a preferred technical solution of the present invention, the I of the digital signal processor DSP ref is connected to a reference power supply I ref .

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] 1. By combining DEMPT control and PID control, a DEMPT-PID control method is proposed to shorten the rising time of the output LED current, thereby increasing the pulse light period and the adjustable range of the duty cycle. At the same time, by switching the control mode to PID control, the low-frequency oscillation caused by DEMPT control is eliminated, the stability of the LED current is improved, and the current ripple is reduced;

[0015] 2. On the basis of satisfying the rising time of the output current, overshoot is suppressed, and the influence of the low-frequency ripple generated by the DEMPT mode in the steady state is avoided by switching to the PID control mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the circuit diagram of the present invention;

[0017] Figure 2 is the PWM waveform and actual current waveform diagram of the present invention;

[0018] Figure 3 is the trailing edge modulation PT control and DEMPT control start waveform diagram of the present invention;

[0019] Figure 4 is the parameter change schematic diagram of the present invention;

[0020] Figure 5 is the control program flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] Please refer to Figures 1-5 , the present invention provides a high-efficiency LED lamp drive power supply with controllable pulse energy, including an LED lamp drive power supply. The LED lamp drive power supply includes a Buck main power circuit, an LED, a differential amplifier circuit, and a digital signal processor DSP. The PWM pin of the digital signal processor DSP is connected to one end of the Buck main power circuit, the other end of the Buck main power circuit is connected to one end of the LED, the other end of the LED is connected to one end of the differential amplifier circuit, and the other end of the differential amplifier circuit is connected to the AD pin of the digital signal processor DSP.

[0023] The Buck main power circuit includes a DC power supply DC, a switching tube Q, a freewheeling diode D, a filter inductor L, an output filter capacitor C, and a current sampling resistor R1. One end of the DC power supply DC is respectively connected to one end of the freewheeling diode D and one end of the output filter capacitor C. The other end of the DC power supply DC is connected to the source electrode of the switching tube Q. The drain electrode of the switching tube Q is respectively connected to the other end of the freewheeling diode D and one end of the filter inductor L. The other end of the filter inductor L is respectively connected to the other end of the output filter capacitor C and one end of the current sampling resistor R1. The other end of the current sampling resistor R1 and the surface of the output filter capacitor C are both connected to the LED. The gate electrode of the switching tube Q is connected to the PWM terminal of the digital signal processor DSP.

[0024] The LED includes an equivalent diode D LED , an equivalent DC source V F , and an equivalent resistor R LED . One end of the equivalent DC source V F is connected to one end of the equivalent diode D LED . The other end of the equivalent DC source V F is connected to one end of the equivalent resistor R LED . The other end of the equivalent diode D LED and the other end of the equivalent resistor R LED are both connected to the Buck main power circuit. The connection point of the equivalent resistor R LED and the Buck main power circuit is connected to the differential amplifier circuit.

[0025] The differential amplifier circuit includes resistor R2, resistor R3, resistor R4, resistor R5 and an amplifier. The negative terminal pins of the amplifier are respectively connected to one end of resistor R2 and one end of resistor R3. The other end of resistor R3 is connected to the output terminal of the amplifier. The positive terminal pins of the amplifier are respectively connected to one end of resistor R5 and one end of resistor R4. The other end of resistor R5 is grounded. The other end of resistor R4 is connected to the LED. The output terminal of the amplifier is connected to the AD terminal of the digital signal processor DSP.

[0026] The I of the digital signal processor DSP ref is connected with a reference power supply I ref .

[0027] In the present invention, in combination with the accompanying drawings of the specification Figure 1 , in the Buck circuit, constant current drive is adopted in the pulse bright area. By feeding back the voltage of R1 and obtaining the LED current value through conversion, VIN is the DC input of the circuit. The digital signal processor DSP is used as the control core, and the switching drive PWM is adjusted according to the feedback signal. The digital signal processor DSP, based on the preset values in the bright area and the dark area, turns on the drive signal in the bright area and turns off the drive signal in the dark area;

[0028] In combination with the accompanying drawings of the specification Figure 2 , where, T SW is the period of the PWM, corresponding to the frequency f SW , corresponding to the duty cycle D SW . By adjusting D SW , the output current i of the Buck circuit is regulated LED , thereby controlling the instantaneous PPFD generated by the LED in the bright area. T L and T D are respectively the bright area time and the dark area time, corresponding to adjusting the pulse light period T DIM and the duty cycle D DIM . When entering the bright area, there is a rise time t r for the output current of the Buck circuit. If T L is less than t r , the output current has not stabilized before switching to the dark area, and the circuit cannot work properly. In order to increase the adjustable range of the output pulse light frequency f DIM , it is necessary to shorten the rise time t r . At the same time, in order to ensure the stability of the light intensity in the bright area, the current overshoot when the LED enters the bright area should be suppressed and the steady-state ripple should be reduced;

[0029] When the Buck circuit operates in the steady state of constant current output, PID control is usually adopted to adjust the driving waveform of the switching tube. However, for the Buck circuit in the pulse switching state, PID control cannot achieve good dynamic response speed and robustness at the same time. PT control is a non-linear control that presets two duty cycle parameters, that is, the pulse sequence with a high duty cycle is P H , with a duty cycle of D H , and the pulse sequence with a low duty cycle is P L , with a duty cycle of D L . When the feedback signal is less than the target parameter, a P H pulse is issued, and when it is greater than the target parameter, a PL pulse is issued. The switching drive duty cycle is:

[0030]

[0031] If the switching tube conducts first and then turns off within a switching cycle, the modulation method is trailing-edge modulation, otherwise it is leading-edge modulation. In PT control, trailing-edge modulation is used for the high-duty-cycle pulse P H , and leading-edge modulation is used for the low-duty-cycle pulse P L . This control method is called dual-edge modulation pulse sequence control. Combining with the attached Figure 3 of the specification, the waveforms of the starting circuits of PT control with trailing-edge modulation and DEMPT control are given. The state with the smallest ripple in the steady state of DEMPT control is when the pulse sequence is combined in the way of 1P H -1P L . At this time, the ripple size is:

[0032]

[0033] The steady-state ripple size of the Buck circuit using PID control is:

[0034]

[0035] It is obtained that the steady-state ripple of PID control is smaller than that of DEMPT control.

[0036] Combining with the attached Figure 4 of the specification, at the end node of each switching cycle, it will be judged whether to switch to PID control according to the above conditions; after switching to the PID control mode, in order to make the output current reach the steady state as soon as possible and reduce the ripple during the switching process, it is necessary to reasonably select the initial duty cycle D M of the PID mode. The value of D M is in the steady state of the PID-controlled Buck circuit. The response of each switching cycle is divided into a zero-state response controlled by the steady-state duty cycle and the inductance current i L and the output capacitor voltage v CThe determined zero-input response is obtained by assigning the steady-state duty cycle of the previous cycle to D M , making the PID circuit state closer to the steady-state circuit state and reducing the output ripple;

[0037] Combined with the attached instructions Figure 5 , when the LED drive system starts, soft start is first used to suppress the overshoot generated during system startup, and the initial steady-state duty cycle is obtained after the system stabilizes. During the soft start process, the duty cycle D SW rises slowly until the output current i LED reaches the target current value I ref . At this stage, the LED outputs continuous light. After the soft start ends, the steady-state duty cycle is read and brought into D M (1), D H (1) and D L (1), entering the pulse dimming stage. Parameter adjustment will be performed once for each pulse light pulse cycle. According to the D H and D L parameters, DEMPT control is carried out until the T ST time node switches to PID control. The starting duty cycle under PID control is the D M of the steady-state duty cycle corresponding to this cycle. The output current is stabilized through PID adjustment, and the steady-state duty cycle of this cycle is read after the circuit enters a stable state. When the bright area time ends, the driver enters the dark area state. At this time, the controller turns off the PWM output, causing the LED current to drop to 0. After each pulse dimming ends, for each dimming cycle, according to the rising time t r of this cycle and the current overshoot value i max , the D H and D L of the next cycle are calculated, and the D M value is updated;

[0038] The rising time t r in the PT-PID control mode is 19 μs, and i max is 1.1 A. The rising time t r in the DEMPT-PID control mode is 15 μs, and i max is 1.1 A. In terms of optimizing the rising time t r , the PT-PID control and the DEMPT-PID control are more likely to reach the set required time T ref , while the PID control not only has difficulty meeting the rising time requirement but also generates a large overshoot and is difficult to enter a stable state in a short time. In terms of the overshoot value i maxIn terms of optimization, when the overshoot magnitude is satisfied, PT-PID control will cause the output current to decrease, while DEMPT-PID control suppresses the overshoot while meeting the requirements of the rise time, generating a relatively ideal output current waveform, and the experimental results are basically consistent with the simulation.

[0039] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-efficiency LED lamp driving power supply with controllable pulse energy, comprising an LED lamp driving power supply, characterized in that: The LED lamp driving power supply includes a Buck main power circuit, an LED, a differential amplifier circuit and a digital signal processor DSP, wherein a PWM end pin of the digital signal processor DSP is connected to one end of the Buck main power circuit, the other end of the Buck main power circuit is connected to one end of the LED, the other end of the LED is connected to one end of the differential amplifier circuit, and the other end of the differential amplifier circuit is connected to an AD end pin of the digital signal processor DSP.

2. A high-efficiency LED lamp driving power supply with controllable pulse energy according to claim 1, characterized in that: The Buck main power circuit includes a DC power supply DC, a switch tube Q, a freewheeling diode D, a filter inductor L, an output filter capacitor C and a current sampling resistor R1. One end of the DC power supply DC is respectively connected to one end of the freewheeling diode D and one end of the output filter capacitor C, and the other end of the DC power supply DC is connected to the source of the switch tube Q.

3. A high-efficiency LED lamp driving power supply with controllable pulse energy according to claim 2, characterized in that: The drain of the switch tube Q is respectively connected to the other end of the freewheeling diode D and one end of the filter inductor L, the other end of the filter inductor L is respectively connected to the other end of the output filter capacitor C and one end of the current sampling resistor R1, the other end of the current sampling resistor R1 and the surface of the output filter capacitor C are both connected to the LED, and the gate of the switch tube Q is connected to the PWM end of the digital signal processor DSP.

4. The high-efficiency LED lamp driving power supply with controllable pulse energy according to claim 1, characterized in that: The LED includes an equivalent diode D LED , equivalent DC source V F And the equivalent resistance R LED , the equivalent DC source V F One end of the equivalent diode D LED One end of the equivalent DC source V F The other end of the equivalent resistor R LED one end of the .

5. A high-efficiency LED lamp driving power supply with controllable pulse energy according to claim 4, characterized in that: The equivalent diode D LED The other end and the equivalent resistance R LED The other end is connected to the Buck main power circuit, the equivalent resistance R LED The connection with the Buck main power loop is connected to the differential amplifier circuit.

6. The high-efficiency LED lamp driving power supply with controllable pulse energy according to claim 1, characterized in that: The differential amplifier circuit includes resistors R2, R3, R4, R5 and an amplifier, wherein the negative terminal of the amplifier is respectively connected to one end of the resistor R2 and one end of the resistor R3, and the other end of the resistor R3 is connected to the output end of the amplifier.

7. A high-efficiency LED lamp driving power supply with controllable pulse energy according to claim 6, characterized in that: The positive terminal of the amplifier is connected to one end of the resistor R5 and one end of the resistor R4 respectively, the other end of the resistor R5 is grounded, the other end of the resistor R4 is connected to the LED, and the output end of the amplifier is connected to the AD end of the digital signal processor DSP.

8. The high-efficiency LED lamp driving power supply with controllable pulse energy according to claim 1, characterized in that: The digital signal processor DSP is ref Connected with reference power supply I ref .

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