CN110798947B - Multipath LED driving circuit - Google Patents
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Abstract
The invention discloses a multipath LED driving circuit, which comprises a front-stage Flyback main circuit, wherein the output end of the front-stage Flyback main circuit is respectively and electrically connected with a shunt inductor and a non-isolated DC-DC sub-circuit, the first output end of the shunt inductor is used as the output end Vo1 of the multipath LED driving circuit, the second output end of the shunt inductor is used as the second output end Vo2 of the multipath LED driving circuit, the positive end of the output end of the non-isolated DC-DC sub-circuit is respectively used as the third output end Vo3 of the multipath LED driving circuit, the output end of the sub-control circuit is used as the control end of the non-isolated DC-sub-circuit, the input end of the Flyback main circuit is respectively and electrically connected with the first output end Vo1 and the second output end Vo2, the loop speed of the non-isolated DC-DC control circuit is faster than that of the loop speed of the front-stage Flyback main circuit, and the output ripple can be reduced.
Description
Technical Field
The invention relates to the technical field of LED driving, in particular to a multipath LED driving circuit.
Background
In the strong competition of the LED driver, the LED driver is developed to low cost, high power factor and multiple output, and the single-stage Flyback circuit can realize the high Power Factor (PFC) function, has the advantages of low cost, simple design and the like, is preferentially selected among the small and medium power LED drivers, and has the problems of large output ripple because the Flyback main control circuit is required to be designed for realizing the PFC function and has very low loop speed. The direct current with large ripple waves can cause stroboscopic problems for the LED lamp, so that the eyesight of a user and the damage to eyes are affected. Meanwhile, the same driver can output multiple paths, so that the connection of multiple paths of LED lamps is a requirement of many lighting occasions.
Chinese patent, bulletin number: CN203193973U, bulletin day: a high-efficiency LED driving circuit comprises a direct-current power supply VIN, an LED control circuit, an overvoltage protection circuit and an LED electrical appliance group, wherein the LED driving circuit is arranged on the day of 9 and 11 of 2013. The LED control circuit comprises a driving chip and an inductor L, wherein the driving chip comprises a power supply end VIN, a power switch end SW, an overvoltage protection end OVP, a feedback input end FB, an enabling end EN and a grounding end GND, the overvoltage protection circuit comprises an overvoltage protection end OVP and a Schottky diode SBD, and the LED electricity utilization set comprises serial LED electricity utilization devices of which the number is an integer value from 3 to 8. The output end of the direct current power supply VIN is electrically connected with the encapsulation pin of the power supply end VIN, and the encapsulation pin of the power supply end VIN is electrically connected with the power supply end VIN through more than 2 gold wires. The scheme adopts the driving chip to control the LED lamp, and increases the manufacturing cost.
Disclosure of Invention
The invention aims to solve the problems that the existing Flyback circuit is difficult to realize multi-output and large in output ripple, and designs a multi-channel LED driving circuit, wherein a shunt inductor is added at the output end of a front-stage Flyback main circuit to proportionally distribute multi-channel output current, a non-isolated DC-DC sub-circuit enables the multi-channel output end of the single-stage Flyback to output stable direct current according to the output total current, and the loop speed of the designed non-isolated DC-DC control circuit is faster than that of the front-stage Flyback main circuit, so that the output ripple is reduced.
In order to achieve the technical purpose, the technical scheme provided by the invention is that the multipath LED driving circuit comprises a front-stage Flyback main circuit, a non-isolated DC-DC sub circuit, a sub-control circuit, a Flyback main circuit and a shunt inductor, wherein the front-stage Flyback main circuit comprises an isolation transformer and a switching tube S1: the isolation transformer comprises a first winding N1, a second winding N2 and a third winding N3 which are mutually coupled, wherein the first end of the first winding N1 is electrically connected with the output positive end of the power supply, the second end of the first winding N1 is electrically connected with the first end of the switch tube S1, the second end of the switch tube S1 is electrically connected with the output negative end of the power supply, the control end of the switch tube S1 is used as the output end of the Flyback main control circuit, the first end of the second winding N2 is used as the input end of the shunt inductor, the first output end of the shunt inductor is electrically connected with the anode end of the diode D1, the cathode end of the diode D1 is used as the first output end Vo1 of the multi-path LED driving circuit, the second output end of the shunt inductor is electrically connected with the anode end of the diode D2, the cathode end of the diode D2 is used as the second output end Vo2 of the multi-path LED driving circuit, the first end of the third winding N3 is electrically connected with the anode end of the diode D3, the cathode end of the diode D3 is electrically connected with the first end of the capacitor C3 and is used as an input positive end of a non-isolated DC-DC sub-circuit, the second end of the third winding N3 is electrically connected with the second end of the capacitor C3 and is used as an input negative end of the non-isolated DC-DC sub-circuit, the second end of the second winding N2 is electrically connected with the output positive end of the non-isolated DC-DC sub-circuit, the output negative end of the non-isolated DC-DC sub-circuit is electrically connected with the first end of a resistor Rs, and the second end of the resistor Rs is used as a third output end Vo3 of the multi-path LED driving circuit; the first output end Vo1 and the third output end Vo3 are used as a first path of output of the multi-path LED driving circuit; the second output end Vo2 and the third output end Vo3 are used as a second path output of the multi-path LED driving circuit; the capacitor C1 is connected between the first output end Vo1 and the second end of the second winding N2, the capacitor C2 is connected between the second output end Vo2 and the second end of the second winding N2, the capacitor C4 is connected between the two output ends of the non-isolated DC-DC sub-circuit, the input end of the sub-control circuit is connected with the second end of the resistor Rs, the output end of the sub-control circuit is connected with the control end of the non-isolated DC-DC sub-circuit, and the sub-control circuit is used for obtaining the total current of the first path of output and the second path of output through the voltage of Rs and controlling the non-isolated DC-DC sub-circuit according to the total current so as to make the amplitude of the total current constant; the first input end of the Flyback main control circuit is connected with the first output and the second output, the output end of the Flyback main control circuit is connected with the control end of the front-stage Flyback main circuit, the Flyback main control circuit is used for detecting the first output voltage and the second output voltage, the maximum value of the first output voltage and the second output voltage is obtained by comparing the two output voltages, and the front-stage Flyback main circuit is controlled according to the maximum value, so that the maximum value of the first output voltage or the second output voltage amplitude is constant when the LED driving circuit is in idle load.
Preferably, the front-stage Flyback main circuit comprises an isolation transformer and a switching tube S1: the isolation transformer comprises a first winding N1, a second winding N2 and a third winding N3 which are mutually coupled, wherein the first end of the first winding N1 is electrically connected with the positive output end of a power supply, the second end of the first winding N1 is electrically connected with the first end of a switching tube, the second end of the switching tube S1 is electrically connected with the negative output end of the power supply, the control end of the switching tube S1 is used as the output end of a Flyback main circuit, the first end of the second winding N2 is used as the positive output end of a front-stage Flyback main circuit, the second end of the second winding N2 is used as the negative output end of the front-stage Flyback main circuit, the first end of the third winding N3 is used as the positive output end of the front-stage Flyback main circuit, and the second end of the third winding N3 is used as the negative output end of the front-stage Flyback main circuit.
Preferably, the loop speed of the sub-control circuit is faster than the loop speed of the Flyback main control circuit.
Preferably, the non-isolated DC-DC sub-circuit includes a diode D4, a switching tube S2, and an inductor L3, where a first end of the switching tube S2 is electrically connected to a second end of the third winding N3, a second end of the switching tube S2 is electrically connected to an anode end of the diode D4, a cathode end of the diode D4 is electrically connected to a cathode end of the diode D3 and a second end of the second winding N2, respectively, an anode end of the diode D4 is electrically connected to a first end of the inductor L3, and a second end of the inductor L3 is electrically connected to a first end of the resistor Rs.
Preferably, the sub-control circuit comprises a sub-driving control circuit, an operational amplifier US1, a resistor RS1 and a capacitor CS1; the first end of the capacitor CS1 is electrically connected with the negative phase input end of the US1, the first end of the capacitor CS1 is electrically connected with the first end of the resistor RS1, the second end of the resistor RS1 is electrically connected with the output end of the operational amplifier US1, the negative phase input end of the operational amplifier US1 is used as a sampling end of the sub-control circuit, and the sampling end is electrically connected with the second end of the resistor Rs; the sampling end collects voltage signals on the resistor RS, the voltage signals collected by the sampling end are compared with a third reference voltage Vref3 of a normal phase input end of the operational amplifier US1 to output a third voltage comparison difference value, the third voltage comparison difference value is used as a first control signal of the sub-driving control circuit after being amplified through a compensation network formed by the resistor RS1 and the capacitor CS1, and the sub-driving control circuit generates a first driving signal according to the first control signal and is used for controlling on-off of the switching tube S2.
Preferably, the Flyback main control circuit includes a first voltage loop circuit, a second voltage loop circuit, a photoelectric coupler, a main driving control circuit, a diode D5 and a diode D6, wherein a second output end Vo2 of the multi-path LED driving circuit is used as a first input end V1 of the first voltage loop circuit, a second output end Vo2 of the multi-path LED driving circuit is used as a second input end V2 of the first voltage loop circuit, a difference value between an input voltage and an output voltage of the non-isolated DC-DC is used as an input voltage Vx1 of the second voltage loop circuit, an output end of the first voltage loop circuit is electrically connected with an anode end of the diode D5, an output end of the diode D5 is electrically connected with an anode end of the photoelectric coupler, an output end of the diode D6 is electrically connected with an input end of the photoelectric coupler, and an output end of the non-isolated DC-DC is electrically connected with an input end of the main driving control circuit, and the output end of the photodiode D5 is used as an output end of the Flyback control circuit.
Preferably, the first voltage loop circuit includes an operational amplifier US2, a resistor RS3, a resistor RS4, a resistor CS2, a diode DS1 and a diode DS2, where an anode end of the diode DS1 is electrically connected to a second output end Vo2 of the multi-path LED driving circuit, a cathode end of the diode DS1 is electrically connected to a first end Vo1 of the multi-path LED driving circuit, an anode end of the diode DS2 is electrically connected to a cathode end of the diode DS1, a second end of the resistor RS3 is electrically connected to a first end of the resistor RS4, a second end of the resistor RS4 is grounded, a first end of the resistor RS4 is electrically connected to a negative phase input end of the operational amplifier US2, a negative phase input end of the capacitor CS2 is electrically connected to a first end of the capacitor CS2, a second end of the capacitor CS2 is electrically connected to a first end of the resistor RS5, and a second end of the resistor RS5 is electrically connected to an output end of the operational amplifier US 2; the non-inverting input end of the operational amplifier US2 is connected with a first reference voltage Vref1; the first voltage loop circuit detects output voltages of the first output end Vo1 and the second output end Vo2 respectively, selects a maximum value of the output voltages of the first output end Vo1 and the second output end Vo2, compares the maximum value with a first reference voltage Vref1, outputs a first comparison difference value, and outputs a feedback signal V3 after differential amplification operation.
Preferably, the second voltage loop circuit includes an operational amplifier US3, a capacitor CS3 and a resistor RS5, where a negative phase input end of the operational amplifier US3 is connected to a differential voltage Vx1, the differential voltage Vx1 is a difference between an input voltage and an output voltage of the non-isolated DC-DC, a first end of the capacitor CS1 is electrically connected to the negative phase input end of the operational amplifier US3, a second end of the capacitor CS3 is electrically connected to a first end of the resistor RS5, a second end of the resistor RS5 is electrically connected to an output end of the operational amplifier US3, and a positive phase input end of the operational amplifier US3 is connected to a second reference voltage Vref2; the negative phase input end of the operational amplifier US3 is connected with a difference voltage Vx1 of the input voltage and the output voltage of the non-isolated DC-DC, the operational amplifier US3 compares the difference voltage Vx1 with a second reference voltage Vref2 of the positive phase input end to output a second comparison difference value, and the second comparison difference value is subjected to comparison and difference operation through a compensation network formed by the resistors RS5 and CS3 to output a feedback signal V4.
Preferably, the first reference voltage Vref1 is greater than the second reference voltage Vref2. When the first voltage loop works at an output idle load, the second voltage loop works at a normal load; when the non-isolated DC-DC is a buck circuit, the difference Vx1 between the input voltage and the output voltage of the non-isolated DC-DC is the voltage drop between point B and point a in fig. 3 and 4.
Preferably, the multi-path LED driving circuit further includes a short-circuit protection circuit, the open-circuit protection circuit includes a switching tube and an operational amplifier S4, a first end of the switching tube S3 is electrically connected with a second end of the resistor RS, a second end of the switching tube is used as a third output end Vo3 of the multi-path LED driving circuit, a negative phase input end of the operational amplifier US4 is electrically connected with a second end of the resistor RS, a negative phase input end of the operational amplifier US4 samples a voltage signal representing an output total current of the front-stage Flyback main circuit, the voltage signal is compared with a fourth reference voltage Vref4 of a positive phase input end of the operational amplifier US4, and then a fourth comparison value V5 is output, and an output end of the operational amplifier S4 is electrically connected with a control end of the switching tube S3.
The invention has the beneficial effects that: according to the multi-channel LED driving circuit designed by the invention, the output current of multi-channel output is distributed in proportion by adding the shunt inductance at the output end of the front-stage Flyback main circuit, the non-isolated DC-DC sub-circuit enables the multi-channel output end of the single-stage Flyback to output stable direct current according to the total output current, and the loop speed of the non-isolated DC-DC control circuit is designed to be faster than that of the front-stage Flyback main circuit, so that the output ripple is reduced.
Drawings
Fig. 1 is a schematic circuit diagram of a multi-channel LED driving circuit according to the present invention.
Fig. 2 is a circuit diagram of a shunt inductor of a multi-channel LED driving circuit according to the present invention.
Fig. 3 is a schematic circuit diagram of a non-isolated DC-DC sub-circuit of a multi-channel LED driver circuit according to the present invention.
Fig. 4 is a schematic circuit diagram of a sub-control circuit of a multi-channel LED driving circuit according to the present invention.
Fig. 5 is a schematic circuit diagram of a Flyback main control circuit of a multi-channel LED driver circuit of the present invention.
Fig. 6 is a schematic circuit diagram of a first voltage loop circuit of a multi-path LED driving circuit according to the present invention.
Fig. 7 is a schematic circuit diagram of a second voltage loop circuit of the multi-path LED driving circuit according to the present invention.
Fig. 8 is a schematic circuit diagram of a circuit breaking protection circuit of a multi-path LED driving circuit according to the present invention.
The figure indicates: the circuit comprises a 1-front-stage Flyback main circuit, a 2-shunt inductor, a 3-non-isolated DC-DC sub-circuit, a 4-Flyback control circuit, a 5-Flyback main control circuit, a 6-open circuit protection circuit, a 51-first voltage loop circuit and a 52-second voltage loop circuit.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and examples, it being understood that the detailed description herein is merely a preferred embodiment of the present invention, which is intended to illustrate the present invention, and not to limit the scope of the invention, as all other embodiments obtained by those skilled in the art without making any inventive effort fall within the scope of the present invention.
Examples: as shown in fig. 1, a multi-path LED driving circuit is composed of a front-stage Flyback main circuit 1, a non-isolated DC-DC sub-circuit 3, a sub-control circuit 4, a Flyback main circuit 5, a shunt inductor 2, a diode D1, a diode D2, a diode D3, a capacitor C1, a capacitor C2, a capacitor C3 and a capacitor C4, wherein the input end of the front-stage Flyback main circuit 1 is connected with a power supply, and the front-stage Flyback main circuit 1 comprises an isolation transformer and a switching tube S1: the isolation transformer comprises a first winding N1, a second winding N2 and a third winding N3 coupled to each other, the first end of the first winding N1 is electrically connected with the output positive end of the power supply, the second end of the first winding N1 is electrically connected with the first end of the switch tube S1, the second end of the switch tube S1 is electrically connected with the output negative end of the power supply, the control end of the switch tube S1 is used as the output end of the Flyback main control circuit 5, the first end of the second winding N2 is used as the first output positive end of the front-stage Flyback main circuit 1 and is electrically connected with the input end of the shunt inductor 2, the second end of the second winding N2 is used as the first output negative end of the front-stage Flyback main circuit 1 and is electrically connected with the output negative end of the non-isolated DC-DC sub circuit 3, the first end of the third winding N3 is used as the second output positive end of the front-stage Flyback main circuit 1 and is electrically connected with the anode end of the diode D3, the second end of the third winding N3 is used as the second output negative end of the front-stage Flyback main circuit 1 and is electrically connected with the second end of the capacitor C3, the first output end of the shunt inductor 2 is electrically connected with the anode end of the diode D1, the cathode end of the diode D1 is used as the first output end Vo1 of the multi-path LED driving circuit, the second output end of the shunt inductor 2 is electrically connected with the anode end of the diode D2, the cathode end of the diode D2 is used as the second output end Vo2 of the multi-path LED driving circuit, the cathode end of the diode D3 is electrically connected with the first end of the capacitor C3 and is used as an input positive end of the non-isolated DC-DC sub-circuit 3, the second end of the capacitor C3 is electrically connected with the input negative end of the non-isolated DC-DC sub-circuit 3, the output positive end of the non-isolated DC-DC sub-circuit 3 is electrically connected with the first end of the resistor Rs, and the second end of the resistor Rs is used as a third output end Vo3 of the multi-path LED driving circuit; the first output end Vo1 and the third output end Vo3 are used as a first path of output of the multi-path LED driving circuit; the second output end Vo2 and the third output end Vo3 are used as a second path output of the multi-path LED driving circuit; the cathode end of the diode D1 is electrically connected with the first output negative end of the front-stage Flyback main circuit 1 through a capacitor C1, the cathode end of the diode D2 is electrically connected with the first output negative end of the front-stage Flyback main circuit 1 through a capacitor C2, the first end of the resistor Rs is electrically connected with the first output negative end of the front-stage Flyback main circuit 1 through a capacitor C4, the third output end Vo3 of the multi-path LED driving circuit is used as the input end of the sub-control circuit 4, and the output end of the sub-control circuit 4 is used as the control end of the non-isolated DC-DC sub-circuit 3; the first output end Vo1 of the multi-path LED driving circuit is used as a first input end of the Flyback main control circuit 5, the second output end Vo2 of the multi-path LED driving circuit is used as a second input end of the Flyback main control circuit 5, and the output end of the Flyback main control circuit 5 is used as a control end of the front-stage Flyback main circuit 1; the loop speed of the sub-control circuit 4 is faster than the loop speed of the Flyback main control circuit 5.
In this embodiment, the sub-control circuit 4 detects the total current of the first output and the second output, and controls the non-isolated DC-DC sub-circuit 3 to make the total current of the first output and the second output be a direct current with a stable amplitude; the Flyback main control circuit 5 detects a first output voltage V1 of the front-stage Flyback main circuit 1 and an output voltage V2 of the second output, compares the first output voltage V1 with the second output voltage V2 to obtain a maximum value, performs differential amplification operation on the maximum value and a first reference Vref1, and outputs a driving signal to control on-off of the first switching tube when no-load is performed, so that the maximum value of the two output voltages of the LED driving circuit is a value set by the first reference Verf1 when no-load is performed; the Flyback main control circuit 5 also detects that the difference voltage Vx1 between the input voltage and the output voltage of the non-isolated DC-DC sub-circuit 3 and the internal second reference Vref2 perform differential amplification operation, and outputs a driving signal to control the on-off of the first switching tube when the load is carried, so that when the LED driving circuit is connected with the load, the front-stage Flyback main circuit 1 provides enough conversion energy.
As shown in fig. 2, the shunt inductor 2 is composed of an inductor L1 and an inductor L2 that are coupled to each other, a first end of the inductor L1 is electrically connected to a first end of the second winding N2, a second end of the inductor L1D is electrically connected to an anode end of the diode D1, a first end of the inductor L2 is electrically connected to the first end of the inductor L1, a second end of the inductor L2 is electrically connected to an anode end of the diode D2, and the shunt inductor 2 is configured to proportionally distribute output currents of the first output path and the second output path. The shunt inductor 2 distributes output currents of the first output and the second output of the front stage Flyback main circuit 1 according to the turn ratio of the first inductor L1 to the second inductor L2, when the turn ratio is 1:1, the two output currents are equal, and when the turn ratio is 2:1, the output current of the first output is equal to twice the output current of the second output.
As shown in fig. 3, the non-isolated DC-DC sub-circuit 3 is composed of a diode D4, a switching tube S2 and an inductor L3, wherein a first end of the switching tube S2 is electrically connected with a second end of the third winding N3, a second end of the switching tube S2 is electrically connected with an anode end of the diode D4, a cathode end of the diode D4 is electrically connected with a cathode end of the diode D3 and a second end of the second winding N2, an anode end of the diode D4 is electrically connected with a first end of the inductor L3, and a second end of the inductor L3 is electrically connected with a first end of the resistor Rs.
As shown in fig. 4, the sub-control circuit 4 is composed of a sub-drive control circuit, an operational amplifier US1, a resistor RS1 and a capacitor CS 1; the first end of the capacitor CS1 is electrically connected with the negative phase input end of the US1, the first end of the capacitor CS1 is electrically connected with the first end of the resistor RS1, the second end of the resistor RS1 is electrically connected with the output end of the operational amplifier US1, the negative phase input end of the operational amplifier US1 is used as a sampling end of the sub-control circuit 4, and the sampling end is electrically connected with the second end of the resistor Rs; the sampling end collects voltage signals on the resistor RS, the voltage signals collected by the sampling end are compared with a third reference voltage Vref3 of a normal phase input end of the operational amplifier US1, and then a third voltage comparison difference value is output, the third voltage comparison difference value is amplified through a compensation network formed by the resistor RS1 and the capacitor CS1 and then is used as a first control signal of the sub-driving control circuit, the sub-driving control circuit generates a first driving signal according to the first control signal, and the first driving signal is used for controlling on-off of the switching tube S2.
As shown in fig. 5, the Flyback main control circuit 5 includes a first voltage loop circuit 51, a second voltage loop circuit 52, a photo-coupler, a main driving control circuit, a diode D5 and a diode D6, wherein a second output terminal Vo2 of the multi-channel LED driving circuit is used as a first input terminal V1 of the first voltage loop circuit 51, a second output terminal Vo2 of the multi-channel LED driving circuit is used as a second input terminal V2 of the first voltage loop circuit 51, a difference between an input voltage and an output voltage of the non-isolated DC-DC is used as an input voltage Vx1 of the second voltage loop circuit 52, an output terminal of the first voltage loop circuit 51 is electrically connected with an anode terminal of the diode D5, an output terminal of the diode D5 is electrically connected with an input terminal of the photo-coupler, an output terminal of the second voltage loop circuit 52 is electrically connected with an input terminal of the main driving control circuit, and an output terminal of the Flyback main driving control circuit is used as a control terminal of the switch S1.
In this scheme, the first voltage loop detects output voltages of the first output and the second output respectively, then selects a maximum value of the output voltages of the first output and the second output, compares the maximum value with a first reference Vref1, and outputs a feedback signal V3 after differential amplification operation; the second voltage loop detects a difference value Vx1 between the input voltage and the output voltage of the non-isolated DC-DC, compares the difference value Vx1 with the second reference Vref2, and outputs an output feedback signal V4 after differential amplification operation; the feedback signals V3 and V4 are respectively connected through a diode D5 and a diode D6, and after the output ends of the two diodes are connected, the photoelectric coupler is connected; the two diodes belong to a competition relationship, namely, which feedback signal is larger, and which diode is conducted; for example: when two paths of outputs of the multi-path LED driving circuit are not connected with a load (i.e. no load), the photoelectric coupler transmits the output feedback signal V3 to the driving control circuit, and the main driving control circuit controls the on-off of a first switching tube of the front-stage Flyback main circuit 1 according to the output feedback signal V3 output driving signal, so that the maximum value of the two paths of voltages output by the LED driving circuit is a value set by a first reference Verf 1; when two paths of outputs of the multi-path LED driving circuit are connected with a load (namely, when the multi-path LED driving circuit is loaded), the photoelectric coupler transmits the output feedback signal V4 to the main driving control circuit, and the main driving control circuit drives the on-off of a first switching tube of the front-stage Flyback main circuit 1 according to the output feedback signal V4 output driving signal, so that the front-stage Flyback main circuit 1 generates enough conversion energy and can supply the non-isolated DC-DC sub-circuit 3 and an LED lamp; (explaining: since the output voltage on load is determined by the LED lamp, the control action of the voltage ring on load is not to bring the output voltage at the set value, but to energize the lamp and non-isolated circuits).
As shown in fig. 6, the first voltage loop circuit 51 is composed of an operational amplifier US2, a resistor RS3, a resistor RS4, a resistor CS2, a diode DS1 and a diode DS2, wherein the anode end of the diode DS1 is electrically connected with the second output end Vo2 of the multi-path LED driving circuit, the cathode end of the diode DS1 is electrically connected with the first output end Vo1 of the multi-path LED driving circuit, the cathode end of the diode DS2 is electrically connected with the cathode end of the diode DS1, the second end of the resistor RS3 is electrically connected with the first end of the resistor RS4, the second end of the resistor RS4 is grounded, the first end of the resistor RS4 is electrically connected with the negative phase input end of the operational amplifier US2, the negative phase input end of the operational amplifier US2 is electrically connected with the first end of the capacitor CS2, the second end of the capacitor CS2 is electrically connected with the first end of the resistor RS5, and the second end of the resistor RS5 is electrically connected with the output end of the operational amplifier US 2; the non-inverting input end of the operational amplifier US2 is connected with a first reference voltage Vref1; the first voltage loop circuit 51 detects output voltages of the first output end Vo1 and the second output end Vo2, selects a maximum value of the output voltages of the first output end Vo1 and the second output end Vo2, compares the maximum value with the first reference voltage Vref1 to output a first comparison difference value, and outputs a feedback signal V3 after differential amplification operation of the comparison difference value.
As shown in fig. 7, the second voltage loop circuit 52 includes an operational amplifier US3, a capacitor CS3 and a resistor RS5, wherein a negative phase input end of the operational amplifier US3 is connected to a differential voltage Vx1, the differential voltage Vx1 is a difference between an input voltage and an output voltage of a non-isolated DC-DC, a first end of the capacitor CS1 is electrically connected to the negative phase input end of the operational amplifier US3, a second end of the capacitor CS3 is electrically connected to a first end of the resistor RS5, a second end of the resistor RS5 is electrically connected to an output end of the operational amplifier US3, and a positive phase input end of the operational amplifier US3 is connected to a second reference voltage Vref2; the negative phase input end of the operational amplifier US3 is connected with a difference voltage Vx1 of the input voltage and the output voltage of the non-isolated DC-DC, the operational amplifier US3 compares the difference voltage Vx1 with a second reference voltage Vref2 of the positive phase input end to output a second comparison difference value, and the second comparison difference value is subjected to comparison and difference operation through a compensation network consisting of resistors RS5 and CS3 to output a feedback signal V4.
In this embodiment, the first reference voltage Vref1 is greater than the second reference voltage Vref2. When the first voltage loop works at the output no-load state, the second voltage loop works at the normal load state; when the non-isolated DC-DC is a buck circuit, the difference Vx1 between the input voltage and the output voltage of the non-isolated DC-DC is the voltage drop between point B and point a in fig. 3 and 4. When V1 is larger than V2, the RS3 and the RS4 divide the V1, otherwise when V1 is smaller than V2, the RS3 and the RS4 divide the V2.
In embodiment 2, as shown in fig. 8, the circuit structure and connection relationship of embodiment 2 are basically the same as those of embodiment 1, and the difference is that the multi-path LED driving circuit further includes a short-circuit protection circuit, the open-circuit protection circuit 6 includes a switching tube S3 and an operational amplifier S4, the first end of the switching tube S3 is electrically connected with the second end of the resistor RS, the second end of the switching tube is used as a third output end Vo3 of the multi-path LED driving circuit, the negative phase input end of the operational amplifier US4 is electrically connected with the second end of the resistor RS, the negative phase input end of the operational amplifier US4 samples a voltage signal representing the output total current of the front-stage Flyback main circuit 1, the voltage signal is compared with a fourth reference voltage Vref4 of the positive phase input end of the operational amplifier US4, and then a fourth comparison value V5 is output, and the output end of the operational amplifier S4 is electrically connected with the control end of the switching tube S3; the fourth reference voltage Vref4 is larger than the voltage of the negative phase input end of the operational amplifier US4 during normal operation, the switching tube S3 is normally operated, when the output is short-circuited, the voltage of the negative phase input end is instantaneously larger than the fourth reference voltage Vref4, at the moment, the switching tube S3 is disconnected for operation, and the non-isolated DC-DC cannot be damaged due to bearing of large back pressure.
The above embodiments are preferred embodiments of a multi-channel LED driving circuit according to the present invention, and are not limited to the embodiments, but the scope of the invention includes equivalent variations according to the shape and structure of the invention.
Claims (10)
1. A multipath LED driving circuit is characterized in that:
The Flyback main circuit comprises a front-stage Flyback main circuit, a non-isolation DC-DC sub circuit, a sub control circuit, a Flyback main control circuit and a shunt inductor, wherein the front-stage Flyback main circuit comprises an isolation transformer and a switching tube S1: the isolation transformer comprises a first winding N1, a second winding N2 and a third winding N3 which are mutually coupled, wherein the first end of the first winding N1 is electrically connected with the output positive end of a power supply, the second end of the first winding N1 is electrically connected with the first end of a switching tube S1, the second end of the switching tube S1 is electrically connected with the output negative end of the power supply, the control end of the switching tube S1 is used as the output end of a Flyback main control circuit, the first end of the second winding N2 is used as the input end of a shunt inductor, the first output end of the shunt inductor is electrically connected with the anode end of a diode D1, the cathode end of the diode D1 is used as the first output end Vo1 of the multi-path LED driving circuit, the second output end of the shunt inductor is electrically connected with the anode end of a diode D2, the cathode end of the diode D2 is used as the second output end Vo2 of the multi-path LED driving circuit, the first end of the third winding N3 is electrically connected with the anode end of a diode D3, the cathode end of the diode D3 is electrically connected with the first end of a capacitor C3 and used as the input positive end of a non-isolation DC-DC sub-circuit, the second end of the third winding N3 is electrically connected with the second end of the capacitor C3 and serves as an input negative end of a non-isolated DC-DC sub-circuit, the second end of the second winding N2 is electrically connected with an output positive end of the non-isolated DC-DC sub-circuit, the output negative end of the non-isolated DC-DC sub-circuit is electrically connected with a first end of a resistor Rs, and the second end of the resistor Rs serves as a third output end Vo3 of the multi-path LED driving circuit; the first output end Vo1 and the third output end Vo3 are used as a first path of output of the multi-path LED driving circuit; the second output end Vo2 and the third output end Vo3 are used as a second path output of the multi-path LED driving circuit; a capacitor C1 is connected between the first output end Vo1 and the second end of the second winding N2, a capacitor C2 is connected between the second output end Vo2 and the second end of the second winding N2, a capacitor C4 is connected between the two output ends of the non-isolated DC-DC sub-circuit, an input end of the sub-control circuit is connected with one end of the resistor Rs, an output end of the sub-control circuit is connected with a control end of the non-isolated DC-DC sub-circuit, the sub-control circuit is used for obtaining total current output by the first path of output and the second path of output through the voltage of the resistor Rs and controlling the non-isolated DC-DC sub-circuit according to the total current, so that the magnitude of the total current is constant; the first input end of the Flyback main control circuit is connected with the first output and the second output, the output end of the Flyback main control circuit is connected with the control end of the front-stage Flyback main circuit, the Flyback main control circuit is used for detecting the voltage output by the first output voltage and the second output voltage, the maximum value of the first output voltage and the second output voltage is obtained by comparing the two output voltages, the front-stage Flyback main circuit is controlled according to the maximum value, the maximum value of the amplitude of the first output voltage or the second output voltage is kept constant when the LED driving circuit is in idle load, the Flyback main control circuit also detects the difference voltage Vx1 between the input voltage and the output voltage of the non-isolated DC-DC sub-circuit to perform differential amplification operation with the internal second reference Vref2, and a driving signal is output to control the on-off of the switch tube S1 during load, so that the front-stage Flyback main circuit provides enough conversion energy when the LED driving circuit is connected with a load.
2. The multiplexing LED driver circuit of claim 1 wherein:
The loop speed of the sub-control circuit is faster than that of the Flyback main control circuit.
3. The multiplexing LED driver circuit of claim 2 wherein:
The shunt inductor is used for distributing output current of the first output and the second output according to a proportion, the shunt inductor comprises an inductor L1 and an inductor L2 which are mutually coupled, a first end of the inductor L1 is electrically connected with a first end of the second winding N2, a second end of the inductor L1 is electrically connected with an anode end of the diode D1, a first end of the inductor L2 is electrically connected with the first end of the inductor L1, and a second end of the inductor L2 is electrically connected with an anode end of the diode D2.
4. The multiplexing LED driver circuit of claim 2 wherein:
The non-isolated DC-DC sub-circuit comprises a diode D4, a switching tube S2 and an inductor L3, wherein a first end of the switching tube S2 is electrically connected with a second end of the third winding N3, a second end of the switching tube S2 is electrically connected with an anode end of the diode D4, a cathode end of the diode D4 is respectively electrically connected with a cathode end of the diode D3 and a second end of the second winding N2, an anode end of the diode D4 is electrically connected with a first end of the inductor L3, and a second end of the inductor L3 is electrically connected with a first end of the resistor Rs.
5. The multiplexing LED driver circuit of claim 4 wherein:
The sub-control circuit comprises a sub-drive control circuit, an operational amplifier US1, a resistor RS1 and a capacitor CS1; the first end of the capacitor CS1 is electrically connected with the negative phase input end of the US1, the first end of the capacitor CS1 is electrically connected with the first end of the resistor RS1, the second end of the resistor RS1 is electrically connected with the output end of the operational amplifier US1, the negative phase input end of the operational amplifier US1 is used as a sampling end of the sub-control circuit, and the sampling end is electrically connected with the second end of the resistor Rs; the sampling end collects voltage signals on the resistor RS, the voltage signals collected by the sampling end are compared with a third reference voltage Vref3 of a normal phase input end of the operational amplifier US1 to output a third voltage comparison difference value, the third voltage comparison difference value is used as a first control signal of the sub-driving control circuit after being amplified through a compensation network formed by the resistor RS1 and the capacitor CS1, and the sub-driving control circuit generates a first driving signal according to the first control signal and is used for controlling on-off of the switching tube S2.
6. A multi-channel LED driving circuit according to claim 1 or 4, wherein:
The Flyback main control circuit is further configured to detect a difference voltage Vx1 between an input voltage and an output voltage of the non-isolated DC-DC sub-circuit, perform differential amplification operation with an internal second reference Vref2, and output a driving signal to control the front-stage Flyback main circuit, so that the front-stage Flyback main circuit provides enough conversion energy when the LED driving circuit is connected with a load.
7. A multi-channel LED driving circuit according to claim 1 or 5, wherein:
The Flyback main control circuit comprises a first voltage loop circuit, a second voltage loop circuit, a photoelectric coupler, a main driving control circuit, a diode D5 and a diode D6, wherein a second output end Vo2 of the multi-path LED driving circuit is used as a first input end V1 of the first voltage loop circuit, a second output end Vo2 of the multi-path LED driving circuit is used as a second input end V2 of the first voltage loop circuit, the difference value between the input voltage and the output voltage of the non-isolated DC-DC is used as an input voltage Vx1 of the second voltage loop circuit, the output end of the first voltage loop circuit is electrically connected with the anode end of the diode D5, the cathode end of the diode D5 is electrically connected with the input end of the photoelectric coupler, the cathode end of the diode D6 is electrically connected with the input end of the photoelectric coupler, and the output end of the photoelectric coupler is electrically connected with the input end of the main driving control circuit as an output end of the main driving control circuit S1.
8. The multiplexing LED driver circuit of claim 7 wherein:
The second voltage loop circuit comprises an operational amplifier US3, a capacitor CS3 and a resistor RS5, wherein the negative phase input end of the operational amplifier US3 is connected with a difference voltage Vx1, the difference voltage Vx1 is the difference value between the input voltage and the output voltage of the non-isolated DC-DC, the first end of the capacitor CS1 is electrically connected with the negative phase input end of the operational amplifier US3, the second end of the capacitor CS3 is electrically connected with the first end of the resistor RS5, the second end of the resistor RS5 is electrically connected with the output end of the operational amplifier US3, and the positive phase input end of the operational amplifier US3 is connected with a second reference voltage Vref2; the negative phase input end of the operational amplifier US3 is connected with a difference voltage Vx1 of the input voltage and the output voltage of the non-isolated DC-DC, the operational amplifier US3 compares the difference voltage Vx1 with a second reference voltage Vref2 of the positive phase input end to output a second comparison difference value, and the second comparison difference value is subjected to comparison and difference operation through a compensation network formed by the resistors RS5 and CS3 to output a feedback signal V4.
9. The multiplexing LED driver circuit of claim 8 wherein:
The first voltage loop circuit comprises an operational amplifier US2, a resistor RS3, a resistor RS4, a resistor CS2, a diode DS1 and a diode DS2, wherein the anode end of the diode DS1 is electrically connected with the second output end Vo2 of the multi-path LED driving circuit, the cathode end of the diode DS1 is electrically connected with the first end Vo1 of the resistor RS3, the anode end of the diode DS2 is electrically connected with the cathode end of the diode DS1, the second end of the resistor RS3 is electrically connected with the first end of the resistor RS4, the second end of the resistor RS4 is grounded, the first end of the resistor RS4 is electrically connected with the negative phase input end of the operational amplifier US2, the negative phase input end of the operational amplifier US2 is electrically connected with the first end of a capacitor CS2, the second end of the capacitor CS2 is electrically connected with the first end of the resistor RS5, the second end of the resistor RS5 is electrically connected with the output end of the operational amplifier US2, and the output end of the operational amplifier US2 is coupled with the output end of the operational amplifier; the non-inverting input end of the operational amplifier US2 is connected with a first reference voltage Vref1; the first voltage loop circuit detects output voltages of the first output end Vo1 and the second output end Vo2 respectively, selects a maximum value of the output voltages of the first output end Vo1 and the second output end Vo2, compares the maximum value with a first reference voltage Vref1, outputs a first comparison difference value, and outputs a feedback signal V3 after differential amplification operation.
10. A multi-channel LED driving circuit according to claim 1 or 4, wherein: the short-circuit protection circuit comprises a switching tube S3 and an operational amplifier US4, wherein a first end of the switching tube S3 is electrically connected with a second end of a resistor RS, a second end of the switching tube is used as a third output end Vo3 of the multi-path LED driving circuit, a negative-phase input end of the operational amplifier US4 is electrically connected with a second end of the resistor RS, a negative-phase input end of the operational amplifier US4 samples a voltage signal representing the output total current of the front-stage Flyback main circuit, a fourth comparison value V5 is output after the voltage signal is compared with a fourth reference voltage Vref4 of a positive-phase input end of the operational amplifier S4, and an output end of the operational amplifier US4 is electrically connected with a control end of the switching tube S3.
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| CN205546103U (en) * | 2016-04-22 | 2016-08-31 | 浙江英飞特光电有限公司 | Flyback drive circuit |
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| CN211630457U (en) * | 2019-11-18 | 2020-10-02 | 杭州优特电源有限公司 | Multi-path LED driving circuit |
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| AU2008204723A1 (en) * | 2007-01-10 | 2008-07-17 | Pakton Developments Pty Ltd | A DC/DC converter |
| CN205546103U (en) * | 2016-04-22 | 2016-08-31 | 浙江英飞特光电有限公司 | Flyback drive circuit |
| CN108040399A (en) * | 2018-01-03 | 2018-05-15 | 欧普照明股份有限公司 | A kind of overvoltage crowbar and constant current driver circuit for LED |
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