CN211630457U

CN211630457U - Multi-path LED driving circuit

Info

Publication number: CN211630457U
Application number: CN201921989576.XU
Authority: CN
Inventors: 毛昭祺; 王纪周; 柯乃泉
Original assignee: Hangzhou Upowertek Power Supply Co ltd
Current assignee: Hangzhou Upowertek Power Supply Co ltd
Priority date: 2019-11-18
Filing date: 2019-11-18
Publication date: 2020-10-02
Anticipated expiration: 2029-11-18

Abstract

The utility model discloses a multichannel LED drive circuit, including preceding Flyback main circuit, the output of preceding Flyback main circuit is connected with shunt inductance and non-isolation DC-DC sub-circuit electricity respectively, and the first output of shunt inductance is as multichannel LED drive circuit's output Vo1, and the second output of shunt inductance is as multichannel LED drive circuit's second output Vo2, non-isolation DC-DC sub-circuit's output positive end is regarded as respectively multichannel LED drive circuit's third output Vo3, the control end of sub-control circuit output as non-isolation DC-DC sub-circuit, Flyback main control circuit's input is connected with first output Vo1 and second output Vo2 electricity respectively, and non-isolation DC-DC control circuit's loop speed is faster than preceding Flyback circuit's loop speed, can reduce the ripple output.

Description

Multi-path LED driving circuit

Technical Field

The utility model relates to a LED drive technical field, it is specific, relate to a multichannel LED drive circuit.

Background

In the fierce competition of the LED driver, the LED driver develops towards low cost, high power factor and multi-path output, a single-stage Flyback circuit can realize the function of high Power Factor (PFC), and has the advantages of low cost, simple design and the like, the single-stage Flyback circuit is preferentially selected in the middle and small power LED driver, and the Flyback main control circuit needs to be designed for realizing the function of PFC, so that the loop speed of the Flyback main control circuit is very low, and the problem of large output ripple is caused. The direct current with large ripple waves can cause stroboscopic problems for the LED lamp, and further the eyesight of a user is affected and the eyes are injured. Meanwhile, the same driver can output multiple paths, so that the requirement of connecting multiple paths of LED lamps in many lighting occasions is met.

Chinese patent, publication No.: CN203193973U, published: in 2013, 9 and 11, a high-efficiency LED driving circuit comprises a direct-current power supply VIN, an LED control circuit, an overvoltage protection circuit and an LED electric appliance set. The LED control circuit comprises a driving chip and an inductor L, 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 the overvoltage protection end OVP and a Schottky diode SBD, and the LED power consumption group comprises series-connection LEDs with the number of integer values from 3 to 8. The output end of the direct-current power supply VIN is electrically connected with the power supply end VIN packaging pin, and the power supply end VIN packaging pin is electrically connected with the power supply end VIN through more than 2 gold wires. This scheme adopts driver chip to carry out the control of LED lamp, increases manufacturing cost.

SUMMERY OF THE UTILITY MODEL

The utility model aims at solving the problem that current Flyback circuit is difficult to realize multiplexed output and output ripple is big, designed a multichannel LED drive circuit, increase the output current of shunting inductance proportional distribution multiplexed output at the output of preceding level Flyback main circuit, non-isolation DC-DC sub-circuit makes according to the total current of output single-stage Flyback's multichannel output stable direct current, the non-isolated DC-DC control circuit's that designs loop speed is faster than preceding level Flyback main control circuit's loop speed, reduces output ripple.

In order to achieve the technical purpose, the utility model provides a pair of technical scheme is, a multichannel LED drive circuit, including preceding stage Flyback main circuit, non-isolation DC-DC sub-circuit, sub-control circuit, Flyback main control circuit and shunt inductance, preceding stage Flyback main circuit includes isolation transformer and switch tube S1: the isolation transformer comprises a first winding N1, a second winding N2 and a third winding N3 which are coupled with each other, wherein a first end of the first winding N1 is electrically connected with an output positive terminal of a power supply, a second end of the first winding N1 is electrically connected with a first end of a switch tube S1, a second end of the switch tube S1 is electrically connected with an output negative terminal of the power supply, a control terminal of the switch tube S1 is used as an output terminal of the Flyback main control circuit, a first end of the second winding N2 is used as an input terminal of a shunt inductor, a first output terminal of the shunt inductor is electrically connected with an anode terminal of a diode D1, a cathode terminal of the diode D1 is used as a first output terminal Vo1 of the multi-path LED driving circuit, a second output terminal of the shunt inductor is electrically connected with an anode terminal of a diode D2, and a cathode terminal of the diode D2 is used as a second output terminal Vo2 of the multi-path LED driving circuit, a first end of the third winding N3 is electrically connected with an anode end of a diode D3, a cathode end of the diode D3 is electrically connected with a first end of a capacitor C3 and serves as an input positive end of a non-isolated DC-DC sub-circuit, a second end of the third winding N3 is electrically connected with a second end of a capacitor C3 and serves as an input negative end of the non-isolated DC-DC sub-circuit, a second end of the second winding N2 is electrically connected with an output positive end of the non-isolated DC-DC sub-circuit, an output negative end of the non-isolated DC-DC sub-circuit is electrically connected with a first end of a resistor Rs, and a 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 output of the multi-path LED driving circuit; the second output end Vo2 and the third output end Vo3 are used as a second 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 output and the second output by the voltage of Rs and controlling the non-isolated DC-DC sub-circuit according to the total current so as to enable the amplitude of the total current to be 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, the front-stage Flyback main circuit is controlled according to the maximum value, and the maximum value of the first output voltage or the second output voltage amplitude of the LED driving circuit is made to be constant when the LED driving circuit is in no-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 coupled with each other, 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 serves as the output end of the Flyback main control circuit, the first end of the second winding N2 serves as the positive first output end of the Flyback main circuit, the second end of the second winding N2 serves as the negative first output end of the Flyback main circuit, the first end of the third winding N3 serves as the positive second output end of the Flyback main circuit, and the second end of the third winding N3 serves as the negative second output end of the 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 switch tube S2, and an inductor L3, wherein a first end of the switch tube S2 is electrically connected to a second end of the third winding N3, a second end of the switch 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-drive control circuit, an operational amplifier US1, a resistor RS1 and a capacitor CS 1; a first end of the capacitor CS1 is electrically connected with the negative phase input end of the resistor RS1, a first end of the capacitor CS1 is electrically connected with a first end of the resistor RS1, a second end of the resistor RS1 is electrically connected with the output end of the operational amplifier US1, a negative phase input end of the operational amplifier US1 serves as a sampling end of the sub-control circuit, and the sampling end is electrically connected with a second end of the resistor RS; the sampling end collects voltage signals on a resistor RS, the voltage signals collected by the sampling end are compared with a third reference voltage Vref3 at a positive phase input end of the operational amplifier US1 to output a third voltage comparison difference value, the third voltage comparison difference value is amplified through a compensation network composed of the resistor RS1 and a capacitor CS1 and then serves as a first control signal of the sub-drive control circuit, the sub-drive control circuit generates a first drive signal according to the first control signal, and the first drive signal is used for controlling the on-off of the switch tube S2.

Preferably, the Flyback main control circuit includes a first voltage loop circuit, a second voltage loop circuit, a photocoupler, a main driving control circuit, a diode D5 and a diode D6, a second output Vo2 of the multi-path LED driving circuit is used as a first input V1 of the first voltage loop circuit, a second output Vo2 of the multi-path LED driving circuit is used as a second input V2 of the first voltage loop circuit, 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, an output of the first voltage loop circuit is electrically connected with an anode terminal of the diode D5, a cathode terminal of the diode D5 is electrically connected with an input terminal of the photocoupler, an output of the second voltage loop circuit is electrically connected with an anode terminal of the diode D6, and a cathode terminal of the diode D6 is electrically connected with the input terminal of the photocoupler, the output end of the photoelectric coupler is electrically connected with the input end of the main drive control circuit, and the output end of the Flyback main drive control circuit is used as the control end of the switch tube S1.

Preferably, the first voltage loop circuit includes an operational amplifier US2, a resistor RS2, a resistor RS3, a resistor RS4, a capacitor CS2, a diode DS1, and a diode DS2, an anode terminal of the diode DS1 is electrically connected to the second output terminal Vo2 of the multi-way LED driving circuit, a cathode terminal of the diode DS1 is electrically connected to the first terminal of the resistor RS3, an anode terminal of the diode DS2 is electrically connected to the first output terminal Vo1 of the multi-way LED driving circuit, a cathode terminal of the diode DS2 is electrically connected to the cathode terminal of the diode DS1, a second terminal of the resistor RS3 is electrically connected to the first terminal of the resistor RS4, a second terminal of the resistor RS4 is grounded, a first terminal of the resistor RS4 is electrically connected to the negative phase input terminal of the operational amplifier US2, a negative phase input terminal of the operational amplifier US2 is electrically connected to the first terminal of the capacitor CS2, a second terminal of the capacitor CS2 is electrically connected to the first terminal of the resistor RS2, the second end of the resistor RS2 is electrically connected with the output end of the operational amplifier US2, and the output end of the operational amplifier US2 is electrically connected with the input end of a photoelectric coupler; the non-inverting input end of the operational amplifier US2 is connected with a first reference voltage Vref 1; 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 to compare with a 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.

Preferably, the second voltage loop circuit comprises an operational amplifier US3, a capacitor CS3 and a resistor RS5, a negative phase input terminal of the operational amplifier US3 is connected to a difference voltage Vx1, the difference voltage Vx1 is a difference value between an input voltage and an output voltage of the non-isolated DC-DC, a first end of the capacitor CS3 is electrically connected to the negative phase input terminal 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 terminal of the operational amplifier US3, and a positive phase input terminal of the operational amplifier US3 is connected to a second reference voltage Vref 2; the negative phase input end of the operational amplifier US3 is connected to 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 a positive phase input end to output a second comparison difference, and the second comparison difference is compared and differentially operated through a compensation network composed of resistors RS5 and CS3 to output a feedback signal V4.

Preferably, the first reference voltage Vref1 is greater than the second reference voltage Vref 2. When the first voltage loop works at output no-load, the second voltage loop works at 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 from the point B to the point A in FIGS. 3 and 4.

Preferably, the multi-path LED driving circuit further includes a short-circuit protection circuit, the short-circuit protection circuit includes a switching tube and an operational amplifier US4, a first end of the switching tube S3 is electrically connected to a second end of the resistor RS, a second end of the switching tube is used as a third output Vo3 of the multi-path LED driving circuit, a negative phase input end of the operational amplifier US4 is electrically connected to 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 pre-Flyback main circuit, the voltage signal is compared with a fourth reference voltage Vref4 at a positive phase input end of the operational amplifier US4 and then outputs a fourth comparison value V5, and an output end of the operational amplifier US4 is electrically connected to a control end of the switching tube S3.

The utility model has the advantages that: the utility model discloses a multichannel LED drive circuit increases the output current of shunt inductance proportional distribution multichannel output through the output at preceding level Flyback main circuit, and non-isolation DC-DC sub-circuit makes according to the total current of output single-stage Flyback's multichannel output is stable direct current, designs non-isolation DC-DC control circuit's loop speed is faster than preceding level Flyback main control circuit's loop speed, reduces the output ripple.

Drawings

Fig. 1 is a schematic circuit diagram of a multi-path LED driving circuit according to the present invention.

Fig. 2 is a shunt inductance circuit diagram of a multi-path LED driving circuit according to the present invention.

Fig. 3 is a schematic circuit diagram of a non-isolated DC-DC sub-circuit of the multi-path LED driving circuit of the present invention.

Fig. 4 is a schematic circuit diagram of a sub-control circuit of the multi-path LED driving circuit according to the present invention.

Fig. 5 is a schematic circuit diagram of a Flyback main control circuit of the multi-path LED driving circuit of the present invention.

Fig. 6 is a schematic circuit diagram of a first voltage loop circuit of the multi-path LED driving circuit of 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 the multi-path LED driving circuit of the present invention.

The notation in the figure is: 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-circuit breaking protection circuit, a 51-first voltage loop circuit and a 52-second voltage loop circuit.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is described in detail with reference to the accompanying drawings and examples, it should be understood that the specific embodiment described herein is only a preferred embodiment of the present invention, and is only used for explaining the present invention, and does not limit the protection scope of the present invention, and all other embodiments obtained by a person of ordinary skill in the art without creative work belong to the protection scope of the present invention.

Example (b): 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 control 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 an input end of the front-stage Flyback main circuit 1 is connected with a power supply, and the front-stage Flyback main circuit 1 includes 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 coupled with each other, wherein a first end of the first winding N1 is electrically connected with an output positive terminal of a power supply, a second end of the first winding N1 is electrically connected with a first end of a switching tube S1, a second end of the switching tube S1 is electrically connected with an output negative terminal of the power supply, a control end of the switching tube S1 is used as an output end of the Flyback main control circuit 5, a first end of the second winding N2 is used as a first output positive terminal of the Flyback 1 and is electrically connected with an input end of a shunt inductor 2, a second end of the second winding N2 is used as a first output negative terminal of the Flyback main circuit 1 and is electrically connected with an output negative terminal of a non-isolated DC-DC sub-circuit 3, a first end of the third winding N3 is used as a second output negative terminal of the Flyback main circuit 1 and is electrically connected with an anode end of a diode D3, and a second end of the Flyback main circuit 3 is used as a second output negative terminal of the Flyback main circuit 1 and is electrically connected with an anode end of a second output capacitor C3 The first output end of the shunt inductor 2 is electrically connected with the anode end of a diode D1, the cathode end of a 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 a diode D2, the cathode end of a diode D2 is used as the second output end Vo2 of the multi-path LED driving circuit, the cathode end of a diode D3 is electrically connected with the first end of a capacitor C3 and is used as the positive input end of a non-isolated DC-DC sub-circuit 3, the second end of the capacitor C3 is electrically connected with the negative input end of the non-isolated DC-DC sub-circuit 3, the positive output end of the non-isolated DC-DC sub-circuit 3 is electrically connected with the first end of a resistor Rs, and the second end of the resistor Rs is used as the third output end; the first output end Vo1 and the third output end Vo3 are used as the first output of the multi-path LED driving circuit; the second output end Vo2 and the third output end Vo3 are used as a second output of the multi-path LED driving circuit; a cathode end of the diode D1 is electrically connected with a first output negative end of the front-stage Flyback main circuit 1 through a capacitor C1, a cathode end of the diode D2 is electrically connected with a first output negative end of the front-stage Flyback main circuit 1 through a capacitor C2, a first end of the resistor Rs is electrically connected with a first output negative end of the front-stage Flyback main circuit 1 through a capacitor C4, a third output Vo3 of the multi-path LED driving circuit is used as an input end of the sub-control circuit 4, and an output end of the sub-control circuit 4 is used as a control end of the non-isolated DC-DC sub-circuit 3; a 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, a 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 an 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 total currents of the first output and the second output, and controls the non-isolated DC-DC sub-circuit 3 to make the total currents of the first output and the second output be direct currents with stable amplitudes; the Flyback main control circuit 5 detects a first output voltage V1 and a second output voltage V2 of the front-stage Flyback main circuit 1, compares the first output voltage V1 and the second output voltage V2 to obtain the maximum value of the first output voltage and the second output voltage V2, performs differential amplification operation on the maximum value and a first reference Vref1, and outputs a driving signal to control the on-off of the first switching tube during no-load, so that the maximum value of two paths of output voltages of the LED driving circuit is a value set by a first reference Verf1 during no-load; the Flyback main control circuit 5 further detects that the difference voltage Vx1 between the input voltage and the output voltage of the non-isolated DC-DC sub-circuit 3 and an internal second reference Vref2 perform differential amplification operation, outputs a driving signal to control the on-off of the first switching tube when the load is carried, and enables the front-stage Flyback main circuit 1 to provide enough conversion energy when the LED driving circuit is connected with the load.

As shown in fig. 2, the shunt inductor 2 is composed of an inductor L1 and an inductor L2 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 a 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 distribute output currents of the first output and the second output in proportion. The shunt inductor 2 distributes the output currents of the first path output and the second path output of the front-stage Flyback main circuit 1 according to the turn ratio of the first inductor L1 and the second inductor L2, when the turn ratio is 1:1, the two paths of output currents are equal, and when the turn ratio is 2:1, the output current of the first path output is equal to twice the output current of the second path output.

As shown in fig. 3, the non-isolated DC-DC sub-circuit 3 comprises a diode D4, a switch tube S2, and an inductor L3, wherein a first end of the switch tube S2 is electrically connected to a second end of the third winding N3, a second end of the switch tube S2 is electrically connected to an anode end of a 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, 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.

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 resistor RS1, 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 serves as the 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 a voltage signal on the resistor RS, the voltage signal collected by the sampling end is compared with a third reference voltage Vref3 at a positive phase input end of the operational amplifier US1 to output a third voltage comparison difference value, the third voltage comparison difference value is amplified and operated through a compensation network composed of the resistor RS1 and a capacitor CS1 to serve as a first control signal of the sub-drive control circuit, the sub-drive control circuit generates a first drive signal according to the first control signal, and the first drive signal is used for controlling the on-off of the switch 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 photocoupler, a main drive control circuit, a diode D5 and a diode D6, a second output Vo2 of the multi-path LED drive circuit is used as a first input V1 of the first voltage loop circuit 51, a second output Vo2 of the multi-path LED drive circuit is used as a second input 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 of the first voltage loop circuit 51 is electrically connected to an anode terminal of the diode D5, a cathode terminal of the diode D5 is electrically connected to an input terminal of the photocoupler, an output of the second voltage loop circuit 52 is electrically connected to an anode terminal of the diode D6, a cathode terminal of the diode D6 is electrically connected to an input terminal of the photocoupler, an output terminal of the photocoupler is electrically connected to an input terminal of the main drive control circuit, the output end of the Flyback main drive control circuit is used as the control end of the switch tube S1.

In the scheme, the first voltage loop respectively detects the output voltages of the first output and the second output, then the maximum value of the output voltages of the first output and the second output is selected, the maximum value is compared with a first reference Vref1, differential amplification operation is carried out, and then a feedback signal V3 is output; 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; feedback signals V3 and V4 are respectively connected through a diode D5 and a diode D6, and after output ends of the two diodes are connected, the two diodes are connected with the photoelectric coupler; the two diodes belong to a competitive relationship, namely which feedback signal is larger, which diode is conducted; for example: when two paths of output of the multi-path LED driving circuit are not connected with a load (namely, are in no-load state), the photoelectric coupler transmits the output feedback signal V3 to the driving control circuit, and the main driving control circuit outputs a driving signal according to the output feedback signal V3 to control the on-off of a first switching tube of the front-stage Flyback main circuit 1, so that the maximum value of two paths of output voltage of 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 load is carried), the photoelectric coupler transmits the output feedback signal V4 to the main driving control circuit, and the main driving control circuit outputs a driving signal according to the output feedback signal V4 to drive the on-off of a first switching tube of the front Flyback main circuit 1, so that the front Flyback main circuit 1 can generate enough conversion energy to supply to the non-isolated DC-DC sub circuit 3 and the LED lamp; (explain: since the output voltage on load is determined by the LED lamp, the control action of the voltage loop on load is not to bring the output voltage to a set value, but to be able to power the lamp and the non-isolated circuit).

As shown in fig. 6, the first voltage loop circuit 51 is composed of an operational amplifier US2, a resistor RS2, a resistor RS3, the LED driving circuit comprises a resistor RS4, a capacitor 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 of the resistor RS3, the anode end of the diode DS2 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 RS2, the second end of the resistor RS2 is electrically connected with the output end of; the non-inverting input end of the operational amplifier US2 is connected with a first reference voltage Vref 1; the first voltage loop circuit 51 detects output voltages of the first output terminal Vo1 and the second output terminal Vo2, selects a maximum value of the output voltages of the first output terminal Vo1 and the second output terminal Vo2, compares the maximum value with a first reference voltage Vref1 to output a first comparison difference, and outputs a feedback signal V3 after differential amplification operation of the comparison difference.

As shown in fig. 7, the second voltage loop circuit 52 includes an operational amplifier US3, a capacitor CS3 and a resistor RS5, a negative phase input terminal 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 CS3 is electrically connected to the negative phase input terminal 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 terminal of the operational amplifier US3, and a positive phase input terminal of the operational amplifier US3 is connected to a second reference voltage Vref 2; the negative phase input end of the operational amplifier US3 is connected with a difference voltage Vx1 of a non-isolated DC-DC input voltage and an output voltage, the operational amplifier US3 compares the difference voltage Vx1 with a second reference voltage Vref2 of a positive phase input end to output a second comparison difference, and the second comparison difference is compared and differentially operated through a compensation network composed 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 Vref 2. When the first voltage loop works at output no-load, the second voltage loop works at 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 FIGS. 3 and 4. When the V1 is larger than V2, the RS3 and RS4 divide the voltage of V1, and when the V1 is smaller than V2, the RS3 and RS4 divide the voltage of V2.

Embodiment 2, as shown in fig. 8, the circuit structure and connection relationship of embodiment 2 are substantially the same as those of embodiment 1, except 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 US4, a first end of the switching tube S3 is electrically connected to a second end of the resistor RS, a second end of the switching tube is used as a third output Vo3 of the multi-path LED driving circuit, a negative phase input end of the operational amplifier US4 is electrically connected to a second end of the resistor RS, a negative phase input end of the operational amplifier US4 samples a voltage signal representing a total output current of the front-stage Flyback main circuit 1, the voltage signal is compared with a fourth reference voltage Vref4 at a positive phase input end of the operational amplifier US4 to output a fourth comparison value V5, and an output end of the operational amplifier US4 is electrically connected to a control end of the switching tube S3; when the output is short-circuited, the voltage of the negative phase input end is instantaneously greater than the fourth reference voltage Vref4, at this time, the switching tube S3 is disconnected to work, and the non-isolated DC-DC cannot be damaged due to the fact that the non-isolated DC-DC bears large back pressure.

The above-mentioned embodiment does the present invention relates to a multi-path LED driving circuit, which is not limited thereto, the present invention includes but is not limited to the present embodiment, all equivalent changes made by the shape and structure according to the present invention are within the protection scope of the present invention.

Claims

1. A multichannel LED drive circuit which characterized in that:

including preceding stage Flyback main circuit, non-isolation DC-DC sub-circuit, sub-control circuit, Flyback main control circuit and shunt inductance, preceding stage Flyback main circuit includes isolation transformer and switch tube S1: the isolation transformer comprises a first winding N1, a second winding N2 and a third winding N3 which are coupled with each other, wherein a first end of the first winding N1 is electrically connected with an output positive terminal of a power supply, a second end of the first winding N1 is electrically connected with a first end of a switch tube S1, a second end of the switch tube S1 is electrically connected with an output negative terminal of the power supply, a control terminal of the switch tube S1 is used as an output terminal of the Flyback main control circuit, a first end of the second winding N2 is used as an input terminal of a shunt inductor, a first output terminal of the shunt inductor is electrically connected with an anode terminal of a diode D1, a cathode terminal of the diode D1 is used as a first output terminal Vo1 of the multi-path LED driving circuit, a second output terminal of the shunt inductor is electrically connected with an anode terminal of a diode D2, and a cathode terminal of the diode D2 is used as a second output terminal Vo2 of the multi-path LED driving circuit, a first end of the third winding N3 is electrically connected with an anode end of a diode D3, a cathode end of the diode D3 is electrically connected with a first end of a capacitor C3 and serves as an input positive end of a non-isolated DC-DC sub-circuit, a second end of the third winding N3 is electrically connected with a second end of a capacitor C3 and serves as an input negative end of the non-isolated DC-DC sub-circuit, a second end of the second winding N2 is electrically connected with an output positive end of the non-isolated DC-DC sub-circuit, an output negative end of the non-isolated DC-DC sub-circuit is electrically connected with a first end of a resistor Rs, and a 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 output of the multi-path LED driving circuit; the second output end Vo2 and the third output end Vo3 are used as a second 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 two output ends of the non-isolated DC-DC sub-circuit, the input end of the sub-control circuit is connected with one 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 output and the second output through the voltage of the resistor Rs and controlling the non-isolated DC-DC sub-circuit according to the total current so as to enable the amplitude of the total current to be 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, the front-stage Flyback main circuit is controlled according to the maximum value, and the maximum value of the first output voltage or the second output voltage amplitude of the LED driving circuit is made to be constant when the LED driving circuit is in no-load.

2. The multi-channel LED driving circuit as claimed in claim 1, wherein:

the loop speed of the sub-control circuit is faster than that of the Flyback main control circuit.

3. The multi-channel LED driving circuit as claimed in claim 2, wherein:

the shunt inductor is used for distributing the output current of the first output and the second output in proportion, the shunt inductor comprises an inductor L1 and an inductor L2 which are coupled with each other, the first end of the inductor L1 is electrically connected with the first end of the second winding N2, the second end of the inductor L1D is electrically connected with the anode end of the diode D1, the first end of the inductor L2 is electrically connected with the first end of the inductor L1, and the second end of the inductor L2 is electrically connected with the anode end of the diode D2.

4. The multi-channel LED driving circuit as claimed in claim 2, wherein:

the non-isolated DC-DC sub-circuit comprises a diode D4, a switch tube S2 and an inductor L3, wherein a first end of the switch tube S2 is electrically connected with a second end of the third winding N3, a second end of the switch tube S2 is electrically connected with an anode end of a 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 respectively, an anode end of the diode D4 is electrically connected with a first end of an inductor L3, and a second end of the inductor L3 is electrically connected with a first end of the resistor Rs.

5. The multi-channel LED driving circuit as claimed in claim 4, wherein:

the sub-control circuit comprises a sub-drive control circuit, an operational amplifier US1, a resistor RS1 and a capacitor CS 1; a first end of the capacitor CS1 is electrically connected with the negative phase input end of the resistor RS1, a first end of the capacitor CS1 is electrically connected with a first end of the resistor RS1, a second end of the resistor RS1 is electrically connected with the output end of the operational amplifier US1, a negative phase input end of the operational amplifier US1 serves as a sampling end of the sub-control circuit, and the sampling end is electrically connected with a second end of the resistor RS; the sampling end collects voltage signals on a resistor RS, the voltage signals collected by the sampling end are compared with a third reference voltage Vref3 at a positive phase input end of the operational amplifier US1 to output a third voltage comparison difference value, the third voltage comparison difference value is amplified through a compensation network composed of the resistor RS1 and a capacitor CS1 and then serves as a first control signal of the sub-drive control circuit, the sub-drive control circuit generates a first drive signal according to the first control signal, and the first drive signal is used for controlling the on-off of the switch tube S2.

6. The multi-channel LED driving circuit as claimed in claim 1 or 4, wherein:

the Flyback main control circuit is further used for detecting a difference voltage Vx1 between an input voltage and an output voltage of the non-isolated DC-DC sub-circuit, carrying out differential amplification operation with an internal second reference Vref2, and outputting 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. The multi-channel LED driving circuit as claimed in claim 1 or 4, wherein:

the Flyback main control circuit comprises a first voltage loop circuit, a second voltage loop circuit, a photoelectric coupler, a main drive control circuit, a diode D5 and a diode D6, wherein a second output end Vo2 of the multi-path LED drive 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 drive circuit is used as a second input end V2 of the first voltage loop circuit, the difference value of 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 an anode end of the diode D5, a cathode end of the diode D5 is electrically connected with the input end of the photoelectric coupler, the output end of the second voltage loop circuit is electrically connected with the anode end of the diode D6, and a cathode end of the diode D6 is electrically connected with the input end of the photoelectric coupler, the output end of the photoelectric coupler is electrically connected with the input end of the main drive control circuit, and the output end of the Flyback main drive control circuit is used as the control end of the switch tube S1.

8. The multi-channel LED driving circuit as claimed in claim 7, wherein:

the first voltage loop circuit comprises an operational amplifier US2, a resistor RS2, a resistor RS3, a resistor RS4, a capacitor CS2, a diode DS1 and a diode DS2, wherein an anode end of the diode DS1 is electrically connected with a second output end Vo2 of the multi-path LED driving circuit, a cathode end of the diode DS1 is electrically connected with a first end of the resistor RS3, an anode end of the diode DS2 is electrically connected with a first output end Vo1 of the multi-path LED driving circuit, a cathode end of the diode DS2 is electrically connected with a cathode end of the diode DS1, a second end of the resistor RS3 is electrically connected with a first end of a resistor RS4, a second end of the resistor RS4 is grounded, a first end of the resistor RS4 is electrically connected with a negative phase input end of the operational amplifier US2, a negative phase input end of the operational amplifier US2 is electrically connected with a first end of a capacitor CS2, a second end of the capacitor CS2 is electrically connected with a first end of the resistor RS2, the second end of the resistor RS2 is electrically connected with the output end of the operational amplifier US2, and the output end of the operational amplifier US2 is electrically connected with the input end of a photoelectric coupler; the non-inverting input end of the operational amplifier US2 is connected with a first reference voltage Vref 1; 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 to compare with a 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.

9. The multi-channel LED driving circuit as claimed in claim 7, wherein:

the second voltage loop circuit comprises an operational amplifier US3, a capacitor CS3 and a resistor RS5, wherein a 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 an input voltage and an output voltage of the non-isolated DC-DC, a first end of the capacitor CS3 is electrically connected with a negative phase input end of the operational amplifier US3, a second end of the capacitor CS3 is electrically connected with a first end of the resistor RS5, a second end of the resistor RS5 is electrically connected with an output end of the operational amplifier US3, and a positive phase input end of the operational amplifier US3 is connected with a second reference voltage Vref 2; the negative phase input end of the operational amplifier US3 is connected to 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 a positive phase input end to output a second comparison difference, and the second comparison difference is compared and differentially operated through a compensation network composed of resistors RS5 and CS3 to output a feedback signal V4.

10. The multi-channel LED driving circuit as claimed in claim 1 or 4, wherein: the LED driving circuit is characterized by further comprising a short-circuit protection circuit, the short-circuit protection circuit comprises a switch tube S3 and an operational amplifier US4, the first end of the switch tube S3 is electrically connected with the second end of a resistor RS, the second end of the switch 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 total output current of the pre-Flyback main circuit, the voltage signal is compared with a fourth reference voltage Vref4 at the positive phase input end of the operational amplifier US4 and then outputs a fourth comparison value V5, and the output end of the operational amplifier US4 is electrically connected with the control end of the switch tube S3.