Primary-side feedback flyback LED drive protection circuit and protection method thereof
阅读说明：本技术 一种原边反馈的反激led驱动保护电路及其保护方法 (Primary-side feedback flyback LED drive protection circuit and protection method thereof ) 是由 汪菊龙 于 2020-06-15 设计创作，主要内容包括：本发明涉及原边反馈的反激LED驱动领域,公开了一种原边反馈的反激LED驱动保护电路及其保护方法,包括：电流过零检测单元、电压谷底检测单元、采样保持单元、峰值电流控制单元、以及比较输出单元；本发明主要通过电流过零检测单元进行原边反馈的反激LED驱动电路工作时,对电路进行电流过零检测,同时将检测信号发送至控制端；同时电压谷底检测单元,对输入直流电压过大时,将谐振电压转换成与之对应的电流,从而可以防止电路误检,从而提高电路的稳定；在进行恒流输出时,对电压进行比较,从而消除误触发隐患,从而提高了输出的稳定性,从而对恒流输出时,输出精度不会出现误差,从而提高了LED灯的使用寿命。(The invention relates to the field of primary-side feedback flyback LED drive, and discloses a primary-side feedback flyback LED drive protection circuit and a protection method thereof, wherein the protection method comprises the following steps: the device comprises a current zero-crossing detection unit, a voltage valley bottom detection unit, a sampling and holding unit, a peak current control unit and a comparison output unit; when the flyback LED driving circuit which is fed back from the primary side mainly works through the current zero-crossing detection unit, current zero-crossing detection is carried out on the circuit, and meanwhile, a detection signal is sent to the control end; meanwhile, the voltage valley bottom detection unit converts the resonance voltage into the current corresponding to the resonance voltage when the input direct-current voltage is overlarge, so that the false detection of the circuit can be prevented, and the stability of the circuit is improved; when the constant current is output, the voltage is compared, so that the hidden danger of false triggering is eliminated, the output stability is improved, and the output precision is free from errors when the constant current is output, so that the service life of the LED lamp is prolonged.)
1. A primary side feedback flyback LED drive protection circuit is characterized by comprising:
the current zero-crossing detection unit is used for carrying out current zero-crossing detection on the circuit when the flyback LED drive circuit for primary side feedback works and sending a detection signal to the control end;
the voltage valley bottom detection unit is used for converting the resonance voltage into current corresponding to the resonance voltage due to overlarge input direct-current voltage of the flyback LED driving circuit, reducing the voltage, increasing the output current, increasing the reverse-positive voltage and reducing the output current, so that the false detection of the circuit can be prevented, and the stability of the circuit is improved;
the sampling and holding unit is used for carrying out data acquisition on the flyback LED drive circuit, converting from analog signal input to digital signal output, and ensuring that the analog quantity signal degree is kept unchanged after a certain time in the analog quantity conversion period, so that the input signal is kept unchanged in the A/D conversion period, and the conversion precision is ensured;
the peak current control unit is used for comparing the output inductor current detection signal directly used by the person input end with the output signal of the error amplifier to realize the control of the duty ratio of the output pulse, so that the peak current of the output inductor changes along with the error voltage, the dynamic response of a power supply can be well improved, and on the other hand, the rapid over-current protection can be realized, and the reliability of the flyback LED drive circuit is improved to a great extent;
in the primary side feedback current control circuit, because the switch is turned on and has pulse peak current, if the current value at the moment is sampled and controlled, the error triggering action can be generated due to the peak of the leading edge of the pulse, and the comparison output unit is used for eliminating the error triggering hidden trouble.
2. The primary feedback flyback LED drive protection circuit of claim 1, wherein the current zero crossing detection unit comprises: the bidirectional thyristor U3, the resistor R1, the resistor R2, the resistor R3, the photoelectric coupler U1 and the photoelectric coupler U2; pin 1 of the photocoupler U1 is connected with pin 1 of the photocoupler U2 and one end of the resistor R2, pin 2 of the photocoupler U1 is connected with pin 2 of the photocoupler U2 and one end of the triac U3, the other end of the triac U3 is connected with the other end of the resistor R2, pin 3 of the photocoupler U1 is connected with one end of the resistor R1 and the control end, the other end of the resistor R1 is grounded, pin 4 of the photocoupler U1 inputs working voltage, pin 4 of the photocoupler U2 is connected with one end of the resistor R3 and the control end, pin 3 of the photocoupler U2 inputs working voltage, and the other end of the resistor R3 is grounded.
3. The primary feedback flyback LED drive protection circuit of claim 1, wherein the valley detection unit comprises: MOS tube Q1, MOS tube Q2, MOS tube Q3, MOS tube Q4, MOS tube Q5, MOS tube Q6, MOS tube Q7 and inverter U4; the gate of the MOS transistor Q1 is connected to the gate of the MOS transistor Q2, the source of the MOS transistor Q1 is connected to the gate of the MOS transistor Q3, the drain of the MOS transistor Q1 is connected to the drain of the MOS transistor Q2 and grounded, the source of the MOS transistor Q2 is connected to the source and the gate of the MOS transistor Q4 and the gate of the MOS transistor Q7, the drain of the MOS transistor Q4 is connected to the source and the gate of the MOS transistor Q5 and the gate of the MOS transistor Q6, the drain of the MOS transistor Q1 is connected to the drain of the MOS transistor Q6 and grounded, the source of the MOS transistor Q6 is connected to the drain of the MOS transistor Q7, the source of the MOS transistor Q7 is connected to the source of the MOS transistor Q3 and the pin No. 1 of the inverter U4, the drain of the MOS transistor Q3 is connected to the drain INV end, and the pin No. 2 of the inverter U4 outputs the pin No. 2.
4. The primary feedback flyback LED drive protection circuit of claim 1, wherein the sample-and-hold unit comprises: an amplifier U6, an amplifier U7, an analog switch and multiplexer U5, a capacitor C1, a capacitor C2, a capacitor C3 and a resistor R4; wherein, the No. 1 pin of the analog switch and multiplexer U5 is connected with the No. 1 pin and the No. 2 pin of the amplifier U6, the No. 3 pin of the amplifier U6 inputs signals, the No. 4 pin of the amplifier U6 inputs-15V voltage, the No. 8 pin of the amplifier U6 inputs +15V voltage, the No. 2 pin and the No. 15 pin of the analog switch and multiplexer U5 are connected with one end of the capacitor C1, one end of the capacitor C2 and the No. 3 pin of the amplifier U7, the No. 3 pin and the No. 14 pin of the analog switch and multiplexer U5 are connected with the other end of the capacitor C1 and the No. 1 pin of the amplifier U7, the No. 6 pin and the No. 11 pin of the analog switch and multiplexer U5 are connected with the No. 7 pin, the No. 10 pin of the analog switch and multiplexer U5 is connected with one end of the resistor R4, One end of the capacitor C3 is connected with the pin No. 2 of the amplifier U7, the pin No. 13 of the analog switch and the multiplexer U5 inputs +15V voltage, the pin No. 5 of the analog switch and the multiplexer U5 is grounded, the pin No. 4 of the analog switch and the multiplexer U5 inputs-15V voltage, the pin No. 8 of the amplifier U7 inputs +15V voltage, the pin No. 4 of the amplifier U7 inputs-15V voltage, and the pin No. 1 of the amplifier U7 outputs.
5. The primary feedback flyback LED drive protection circuit of claim 1, wherein the comparison output unit comprises: the LED driving circuit comprises an inverter U11, an inverter U12, an inverter U13, an inverter U14, an adjustable resistor RV1, a resistor R7, an LED diode D3, a resistor R6, a capacitor C5 and a crystal oscillator tube X1; wherein, pin 1 and pin 2 of the inverter U13 are connected to and input into one end of the adjustable resistor RV1, pin 3 of the inverter U13 is connected to pin 1 of the inverter U12 and pin 1 and pin 2 of the inverter U11 at the same time, pin 3 of the inverter U11 is connected to one end of the resistor R7 and the cathode of the LED diode D3, the other end and the control end of the adjustable resistor RV1 are connected to the anode of the resistor LED diode D3, pin 3 of the inverter U12 is connected to one end of the resistor R6 and pin 1 and pin 2 of the inverter U14 at the same time, pin 2 of the inverter U12 is connected to the other end of the resistor R6 and one end of the capacitor C5 at the same time, pin 3 of the inverter U14 is connected to the other end of the capacitor C5 and pin 1 of the crystal tube X1 at the same time and inputs-9V voltage, and a No. 2 pin of the crystal oscillator tube X1 inputs a signal.
6. The primary feedback flyback LED drive protection circuit as claimed in claim 5, wherein the opto-coupler U1 and the opto-coupler U2 are both of PC817D type, and the analog switch and multiplexer U5 is of ADG1211 type.
7. The primary feedback flyback LED drive protection circuit of claim 1, wherein the peak current control unit comprises: an error amplifier U8, a voltage comparator U9, a latch U10, a triode Q8, a resistor R5, a capacitor C4, a diode D1, a diode D2, an inductor L1 and a transformer TR 1; wherein, the pin 3 of the error amplifier U8 inputs a reference voltage, the pin 2 of the error amplifier U8 inputs and outputs a voltage and is simultaneously connected with one end of the capacitor C4 and one end of the inductor L1, the pin 1 of the error amplifier U8 is connected with the pin 3 of the voltage comparator U9, the pin 2 of the voltage comparator U9 is simultaneously connected with the emitter of the transistor Q8 and one end of the resistor R5, the pin 1 of the voltage comparator U9 is connected with the pin 3 of the latch U10, the pin 1 of the latch U10 is connected with the base of the transistor Q8, the collector of the transistor Q8 is connected with the input end of the transformer TR1, the output end of the transformer TR1 is connected with the anode of the diode D1, the cathode of the diode D1 is simultaneously connected with the other end of the inductor L1 and the cathode of the diode D2, the anode of the diode D2 is connected to the common terminal, the other end of the capacitor C4 is connected to the common terminal, and the other end of the resistor R5 is connected to the common terminal.
8. The protection method of the primary side feedback flyback LED drive protection circuit according to any one of claims 2 to 5, wherein when the flyback LED drive circuit operates, it is necessary to electrically isolate the input signal from the output signal, and when the isolation is performed, it is necessary to perform voltage circuit detection of the signal, so as to implement constant current output, thereby performing protection output of the circuit, and the specific steps are as follows:
s1, firstly, signal collection is carried out through a sampling and holding unit, signals are input through a pin 3 of an amplifier U6, working voltage is input through a pin 4 and a pin 8 of the amplifier U6, the signals are output to a pin 1 of an analog switch and a multiplexer U5 through operational amplification of the amplifier, working voltage is input through a pin 13 and a pin 4 of the analog switch and the multiplexer U5, and the analog switch and a pin 5 of the multiplexer U5 are protected and grounded; during sampling, the analog switch is connected with the No. 3 pin and the No. 14 pin of the multiplexer U5 to close the internal switch, so that signals are connected and output to the No. 3 pin of the amplifier U7 through the No. 2 pin and the No. 15 pin of the analog switch and the multiplexer U5, and then are operated and output through the No. 1 pin of the amplifier U7; if the circuit is in a holding circuit, the analog switch is connected with the No. 11 pin and the No. 4 pin of the multiplexer U5 so as to be internally closed, so that the analog switch is connected with the No. 10 pin and the No. 7 pin of the multiplexer U5 for output, and the capacitor C3 is used for holding; when the circuit collects, the resistor R4 and the capacitor C2 are connected in series, so that the error can be reduced, the peak of the time base can be reduced, and the collection time is stabilized;
meanwhile, the output signal is sent to a peak current control unit for controlling and outputting, so that:
s2, inputting a signal voltage in the peak current control unit through a pin 2 of an amplifier U8, inputting a reference voltage through a pin 3, performing error output to a voltage comparator U9 through a pin 1 of an error amplifier U8, comparing and outputting the result to a latch through a pin 1 of the voltage comparator U9, and outputting the result to a trigger latch, so that the base of a triode Q8 is electrified, the collector of a triode Q1 is subjected to voltage transformation output through a transformer TR1, and meanwhile, a diode D1 is electrified and conducted, so that the result is output to an inductor L1 and a capacitor C4 to be connected in series for output, thereby avoiding a harmonic resonance point and avoiding harmonic amplification and over-current damage of the capacitor;
and simultaneously, the frequency conversion signal is input into the current zero-crossing detection unit and the voltage valley bottom detection unit to carry out voltage and current detection, so that the following steps are further obtained:
s4, when the current value is equal to zero in the process of input and output change of the current, the voltage on the bidirectional thyristor U1 is zero, the pin No. 3 of the photoelectric coupler U1 and the pin No. 4 of the photoelectric coupler U2 output descending and negative pulse to the control unit, when the input instruction of the control unit exists, the pulse passes through a series of links to generate a pulse string to trigger the bidirectional thyristor U1, so that the bidirectional thyristor U1 is conducted, and the current zero-crossing detection output is performed; when the current value is not equal to zero in the process of changing the input and the output of the current, the voltage of the bidirectional thyristor U1 is not zero, the photoelectric coupler U1 and the photoelectric coupler U2 are electrified and conducted, the control unit inputs the high level of the pin No. 3 of the photoelectric coupler U1 and the pin No. 4 of the photoelectric coupler U2, the circuit does not generate trigger pulse, and the bidirectional thyristor U1 is disconnected and does not work;
s5, in the voltage valley bottom detection unit, the MOS tube Q1, the MOS tube Q2 and the MOS tube Q3 are in a current mirror structure; when the drain input voltage of the MOS transistor Q3 is 0, the source current of the MOS transistor Q3 is equal to the source current value of the MOS transistor Q7; when the drain input voltage of the MOS transistor Q3 is greater than 0, the source current value of the MOS transistor Q7 is greater than that of the MOS transistor Q3; when the drain input voltage of the MOS transistor Q3 is less than 0, the source current value of the MOS transistor Q7 is larger than that of the MOS transistor Q3; therefore, when the source current of the MOS transistor Q3 crosses zero, the output of the circuit is inverted to generate a valley signal; the circuit is thus turned on and output through inverter U4.
9. The protection method of the primary side feedback flyback LED drive protection circuit as claimed in claim 8, wherein the LED drive performs constant current output, performs logic output through logic voltage, firstly needs to perform comparison output to eliminate false triggering hidden danger, and when the output voltage is input through an inverter U13, the input level is determined by the adjustable resistor RV1 and the input working voltage through voltage division; when the input resistance is small, the input is low level, so that the high level output by the inverter U13 is output to the input ends of the inverter U12 and the inverter U11, the inverter U11 is prompted to carry out reverse output, the LED diode D3 is electrified and emits light, the inverter U12 and the inverter U14 form a multi-resonant circuit, and the electrification conducted by the crystal oscillator tube X1 is conducted and output; when the input resistance is large, the input terminal of the inverter U13 is at a high level, causing the input terminals of the inverter U11 and the inverter U12 to be turned off, so that the LED diode D3 is extinguished and no output is made.
Technical Field
The invention relates to the field of primary side feedback flyback LED drive, and discloses a primary side feedback flyback LED drive protection circuit and a protection method thereof.
Background
With the improvement of scientific technology, power equipment not only needs faster and more stable output conditions, but also needs more energy-saving output effect, and the LED lamp serving as a solid-state light source has the characteristics of long service life, excellent effect and environmental protection, so that the LED lamp is widely applied; currently, LEDs are replacing existing lighting sources, such as incandescent, fluorescent, and HID lamps; to light the LED, a constant current is required for operation and a high power factor is required, so that a flyback LED driving circuit has been developed.
In the flyback LED drive circuit, input and output can be electrically isolated, and the flyback LED drive circuit has the advantages of simple control, few external elements, safe use and the like, and is widely applied to medium and low power LEDs. The traditional flyback LED driving circuit adopts a secondary side feedback structure, and a peripheral circuit comprises an optical coupler, an error amplifier and other elements, but the circuit is complex, high in cost, large in size and limited in switching frequency.
Disclosure of Invention
The purpose of the invention is as follows: the invention provides a primary-side feedback flyback LED drive protection circuit and a protection method thereof, which aim to solve the problems.
The technical scheme is as follows: a primary side feedback flyback LED drive protection circuit and a protection method thereof comprise the following steps:
the current zero-crossing detection unit is used for carrying out current zero-crossing detection on the circuit when the flyback LED drive circuit for primary side feedback works and sending a detection signal to the control end;
the voltage valley bottom detection unit is used for converting the resonance voltage into current corresponding to the resonance voltage due to overlarge input direct-current voltage of the flyback LED driving circuit, reducing the voltage, increasing the output current, increasing the reverse-positive voltage and reducing the output current, so that the false detection of the circuit can be prevented, and the stability of the circuit is improved;
the sampling and holding unit is used for carrying out data acquisition on the flyback LED drive circuit, converting from analog signal input to digital signal output, and ensuring that the analog quantity signal degree is kept unchanged after a certain time in the analog quantity conversion period, so that the input signal is kept unchanged in the A/D conversion period, and the conversion precision is ensured;
the peak current control unit is used for comparing the output inductor current detection signal directly used by the person input end with the output signal of the error amplifier to realize the control of the duty ratio of the output pulse, so that the peak current of the output inductor changes along with the error voltage, the dynamic response of a power supply can be well improved, and on the other hand, the rapid over-current protection can be realized, and the reliability of the flyback LED drive circuit is improved to a great extent;
in the primary side feedback current control circuit, because the switch is turned on and has pulse peak current, if the current value at the moment is sampled and controlled, the error triggering action can be generated due to the peak of the leading edge of the pulse, and the comparison output unit is used for eliminating the error triggering hidden trouble.
In one embodiment, the current zero-crossing detection unit includes: the bidirectional thyristor U3, the resistor R1, the resistor R2, the resistor R3, the photoelectric coupler U1 and the photoelectric coupler U2;
In one embodiment, the voltage valley bottom detecting unit includes: MOS tube Q1, MOS tube Q2, MOS tube Q3, MOS tube Q4, MOS tube Q5, MOS tube Q6, MOS tube Q7 and inverter U4; the gate of the MOS transistor Q1 is connected to the gate of the MOS transistor Q2, the source of the MOS transistor Q1 is connected to the gate of the MOS transistor Q3, the drain of the MOS transistor Q1 is connected to the drain of the MOS transistor Q2 and grounded, the source of the MOS transistor Q2 is connected to the source and the gate of the MOS transistor Q4 and the gate of the MOS transistor Q7, the drain of the MOS transistor Q4 is connected to the source and the gate of the MOS transistor Q5 and the gate of the MOS transistor Q6, the drain of the MOS transistor Q1 is connected to the drain of the MOS transistor Q6 and grounded, the source of the MOS transistor Q6 is connected to the drain of the MOS transistor Q7, the source of the MOS transistor Q7 is connected to the source of the MOS transistor Q3 and the pin No. 1 of the inverter U4, the drain of the MOS transistor Q3 is connected to the drain INV end, and the pin No. 2 of the inverter U4 outputs the pin No. 2.
In one embodiment, the sample-and-hold unit comprises: an amplifier U6, an amplifier U7, an analog switch and multiplexer U5, a capacitor C1, a capacitor C2, a capacitor C3 and a resistor R4; wherein, the No. 1 pin of the analog switch and multiplexer U5 is connected with the No. 1 pin and the No. 2 pin of the amplifier U6, the No. 3 pin of the amplifier U6 inputs signals, the No. 4 pin of the amplifier U6 inputs-15V voltage, the No. 8 pin of the amplifier U6 inputs +15V voltage, the No. 2 pin and the No. 15 pin of the analog switch and multiplexer U5 are connected with one end of the capacitor C1, one end of the capacitor C2 and the No. 3 pin of the amplifier U7, the No. 3 pin and the No. 14 pin of the analog switch and multiplexer U5 are connected with the other end of the capacitor C1 and the No. 1 pin of the amplifier U7, the No. 6 pin and the No. 11 pin of the analog switch and multiplexer U5 are connected with the No. 7 pin, the No. 10 pin of the analog switch and multiplexer U5 is connected with one end of the resistor R4, One end of the capacitor C3 is connected with the pin No. 2 of the amplifier U7, the pin No. 13 of the analog switch and the multiplexer U5 inputs +15V voltage, the pin No. 5 of the analog switch and the multiplexer U5 is grounded, the pin No. 4 of the analog switch and the multiplexer U5 inputs-15V voltage, the pin No. 8 of the amplifier U7 inputs +15V voltage, the pin No. 4 of the amplifier U7 inputs-15V voltage, and the pin No. 1 of the amplifier U7 outputs.
In one embodiment, the comparison output unit includes: the LED driving circuit comprises an inverter U11, an inverter U12, an inverter U13, an inverter U14, an adjustable resistor RV1, a resistor R7, an LED diode D3, a resistor R6, a capacitor C5 and a crystal oscillator tube X1; wherein,
In one embodiment, the peak current control unit includes: an error amplifier U8, a voltage comparator U9, a latch U10, a triode Q8, a resistor R5, a capacitor C4, a diode D1, a diode D2, an inductor L1 and a
In one embodiment, the opto-coupler U1 and the opto-coupler U2 are both PC817D and the analog switch and multiplexer U5 is ADG 1211.
A protection method of a primary-side feedback flyback LED drive protection circuit is characterized in that when the flyback LED drive circuit works, the flyback LED drive circuit needs to be electrically isolated from an input signal and an output signal, and meanwhile, the isolation is carried out, voltage circuit detection of the signals needs to be carried out, so that constant current output is realized, and the protection output of the circuit is carried out, and the protection method comprises the following specific steps:
meanwhile, the output signal is sent to a peak current control unit for controlling and outputting, so that:
and simultaneously, the frequency conversion signal is input into the current zero-crossing detection unit and the voltage valley bottom detection unit to carry out voltage and current detection, so that the following steps are further obtained:
In one embodiment, the LED is driven to perform constant current output, logic output is performed through logic voltage, comparison output is required to be performed firstly, so that the hidden danger of false triggering is eliminated, and when the output voltage is subjected to voltage division through an adjustable resistor RV1 and input working voltage through an inverter U13, the input level is high or low; when the input resistance is small, the input is low level, so that the high level output by the inverter U13 is output to the input ends of the inverter U12 and the inverter U11, the inverter U11 is prompted to carry out reverse output, the LED diode D3 is electrified and emits light, the inverter U12 and the inverter U14 form a multi-resonant circuit, and the electrification conducted by the crystal oscillator tube X1 is conducted and output; when the input resistance is large, the input terminal of the inverter U13 is at a high level, causing the input terminals of the inverter U11 and the inverter U12 to be turned off, so that the LED diode D3 is extinguished and no output is made.
Has the advantages that: when the flyback LED driving circuit with primary side feedback works through the current zero-crossing detection unit, current zero-crossing detection is carried out on the circuit, and meanwhile, a detection signal is sent to the control end; meanwhile, the voltage valley bottom detection unit converts the resonance voltage into the current corresponding to the resonance voltage when the input direct-current voltage is overlarge, so that the false detection of the circuit can be prevented, and the stability of the circuit is improved; meanwhile, the sampling and holding unit is used for acquiring data, and can ensure that the analog quantity signal degree is kept unchanged during the analog quantity conversion period, thereby ensuring the conversion precision; at the moment, the peak current control unit realizes the control of the duty ratio of the output pulse, so that the dynamic response of a power supply can be well improved, and on the other hand, the rapid overcurrent protection can be realized, so that the reliability of the flyback LED drive circuit is improved to a great extent; finally, the false triggering hidden danger is eliminated through the comparison output unit, so that the stability of output is improved, errors cannot occur in output precision during constant current output, and the service life of the LED lamp is prolonged.
Drawings
FIG. 1 is a flow chart of the present invention.
Fig. 2 is a circuit diagram of the current zero-crossing detection unit of the present invention.
Fig. 3 is a circuit diagram of a valley detection unit according to the present invention.
Fig. 4 is a circuit diagram of a sample-and-hold cell of the present invention.
Fig. 5 is a circuit diagram of a peak current control unit of the present invention.
Fig. 6 is a circuit diagram of a comparison output unit of the present invention.
Fig. 7 is a circuit diagram of the present invention.
Detailed Description
As shown in fig. 1, in this embodiment, a primary-side feedback flyback LED driving protection circuit and a protection method thereof include: the device comprises a current zero-crossing detection unit, a voltage valley bottom detection unit, a sampling and holding unit, a peak current control unit and a comparison output unit.
In a further embodiment, the current zero crossing detection unit comprises: the circuit comprises a bidirectional thyristor U3, a resistor R1, a resistor R2, a resistor R3, a photoelectric coupler U1 and a photoelectric coupler U2.
In a further embodiment, the voltage valley bottom detecting unit includes: MOS transistor Q1, MOS transistor Q2, MOS transistor Q3, MOS transistor Q4, MOS transistor Q5, MOS transistor Q6, MOS transistor Q7 and inverter U4.
In a further embodiment, the sample-and-hold unit comprises: amplifier U6, amplifier U7, analog switch and multiplexer U5, capacitor C1, capacitor C2, capacitor C3, and resistor R4.
In a further embodiment, the comparison output unit comprises: the LED driving circuit comprises an inverter U11, an inverter U12, an inverter U13, an inverter U14, an adjustable resistor RV1, a resistor R7, an LED diode D3, a resistor R6, a capacitor C5 and a crystal oscillator tube X1.
In a further embodiment, the peak current control unit comprises: the circuit comprises an error amplifier U8, a voltage comparator U9, a latch U10, a triode Q8, a resistor R5, a capacitor C4, a diode D1, a diode D2, an inductor L1 and a
As shown in fig. 2, pin No. 1 of the photocoupler U1 is connected to pin No. 1 of the photocoupler U2 and one end of the resistor R2, pin No. 2 of the photocoupler U1 is connected to pin No. 2 of the photocoupler U2 and one end of the triac U3, the other end of the triac U3 is connected to the other end of the resistor R2, pin No. 3 of the photocoupler U1 is connected to one end of the resistor R1 and a control end, the other end of the resistor R1 is grounded, pin No. 4 of the photocoupler U1 inputs an operating voltage, pin No. 4 of the photocoupler U2 is connected to one end of the resistor R3 and a control end, pin No. 3 of the photocoupler U2 inputs an operating voltage, and the other end of the resistor R3 is grounded.
As shown in fig. 3, the gate of the MOS transistor Q1 is connected to the gate of the MOS transistor Q2, the source of the MOS transistor Q1 is connected to the gate of the MOS transistor Q3, the drain of the MOS transistor Q1 is connected to the drain of the MOS transistor Q2 and grounded, the source of the MOS transistor Q2 is connected to the source and the gate of the MOS transistor Q4 and the gate of the MOS transistor Q7, the drain of the MOS transistor Q4 is connected to the source and the gate of the MOS transistor Q5 and the gate of the MOS transistor Q6, the drain of the MOS transistor Q1 is connected to the drain of the MOS transistor Q6 and grounded, the source of the MOS transistor Q6 is connected to the drain of the MOS transistor Q7, the source of the MOS transistor Q7 is connected to the source of the MOS transistor Q3 and the pin No. 1 of the inverter U4, the drain of the MOS transistor Q3 is connected to the drain of the
As shown in fig. 4,
As shown in fig. 5, pin No. 1 and pin No. 2 of the inverter U13 are connected to and input at one end of the adjustable resistor RV1, pin No. 3 of the inverter U13 is connected to pin No. 1 of the inverter U12 and pin No. 1 and pin No. 2 of the inverter U11 at the same time, pin No. 3 of the inverter U11 is connected to one end of the resistor R7 and the negative electrode of the LED diode D3, the other end and the control end of the adjustable resistor RV1 are connected to the positive electrode of the resistor LED diode D3, pin No. 3 of the inverter U12 is connected to one end of the resistor R6 and pin No. 1 and pin No. 2 of the inverter U14 at the same time, pin No. 2 of the inverter U12 is connected to the other end of the resistor R6 and one end of the capacitor C5 at the same time, pin No. 3 of the inverter U14 is connected to the other end of the capacitor C5 and pin No. 1 of the crystal tube X1 at the same time and inputs the voltage of V9-V36, and a No. 2 pin of the crystal oscillator tube X1 inputs a signal.
As shown in fig. 6, the reference voltage is input to pin No. 3 of the error amplifier U8, the reference voltage is input to pin No. 2 of the error amplifier U8, and is simultaneously connected to one end of the capacitor C4 and one end of the inductor L1, the pin No. 1 of the error amplifier U8 is connected to pin No. 3 of the voltage comparator U9, the pin No. 2 of the voltage comparator U9 is simultaneously connected to the emitter of the transistor Q8 and one end of the resistor R5, the pin No. 1 of the voltage comparator U9 is connected to pin No. 3 of the latch U10, the pin No. 1 of the latch U10 is connected to the base of the transistor Q8, the collector of the transistor Q8 is connected to the input terminal of the transformer TR1, the output terminal of the transformer TR1 is connected to the positive terminal of the diode D1, the negative terminal of the diode D1 is simultaneously connected to the other end of the inductor L1 and the negative terminal of the diode D2, the anode of the diode D2 is connected to the common terminal, the other end of the capacitor C4 is connected to the common terminal, and the other end of the resistor R5 is connected to the common terminal.
The utility model provides a protection method of flyback LED drive protection circuit of primary side feedback, when flyback LED drive circuit carries out work, need carry out input signal and output signal's electrical isolation, when keeping apart simultaneously, need carry out the voltage circuit detection of signal to realize constant current output, thereby carry out the protection output of circuit, concrete step is as follows:
meanwhile, the output signal is sent to a peak current control unit for controlling and outputting, so that:
and simultaneously, the frequency conversion signal is input into the current zero-crossing detection unit and the voltage valley bottom detection unit to carry out voltage and current detection, so that the following steps are further obtained:
Preferably, the LED is driven to perform constant current output, logic output is performed through logic voltage, comparison output is required to be performed firstly, so that the hidden danger of false triggering is eliminated, and when the output voltage is input through the inverter U13, the level is determined by the adjustable resistor RV1 and the input working voltage in a voltage division mode; when the input resistance is small, the input is low level, so that the high level output by the inverter U13 is output to the input ends of the inverter U12 and the inverter U11, the inverter U11 is prompted to carry out reverse output, the LED diode D3 is electrified and emits light, the inverter U12 and the inverter U14 form a multi-resonant circuit, and the electrification conducted by the crystal oscillator tube X1 is conducted and output; when the input resistance is large, the input terminal of the inverter U13 is at a high level, causing the input terminals of the inverter U11 and the inverter U12 to be turned off, so that the LED diode D3 is extinguished and no output is made.
According to the working principle, when primary side feedback flyback LED driving work is carried out, constant current output is carried out, meanwhile, an output signal is subjected to gas isolation, and meanwhile, voltage circuit detection of the signal is required to be carried out during isolation, so that constant current output is realized, and protection output of the circuit is carried out; meanwhile, signal collection is carried out through a sampling and holding unit, signals are input through a
the variable frequency signal is input into the current zero-crossing detection unit and the voltage valley bottom detection unit to carry out voltage and current detection, when the current value is equal to zero in the process of input and output change of the current, the voltage on the bidirectional thyristor U1 is zero, the
finally, the LED is driven to carry out constant current output, logic output is carried out through logic voltage, comparison output is needed firstly, so that the hidden danger of false triggering is eliminated, and when the output voltage is input through the inverter U13, the level is determined by the voltage division of the adjustable resistor RV1 and the input working voltage; when the input resistance is small, the input is low level, so that the high level output by the inverter U13 is output to the input ends of the inverter U12 and the inverter U11, the inverter U11 is prompted to carry out reverse output, the LED diode D3 is electrified and emits light, the inverter U12 and the inverter U14 form a multi-resonant circuit, and the electrification conducted by the crystal oscillator tube X1 is conducted and output; when the input resistance is large, the input terminal of the inverter U13 is at a high level, causing the input terminals of the inverter U11 and the inverter U12 to be turned off, so that the LED diode D3 is extinguished and no output is made.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.
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