Three-channel isolation control feedback loop circuit

Abstract

The invention discloses a three-channel isolation control feedback loop circuit. The isolation type LED power supply power conversion and output circuit comprises a dimming control circuit, a signal generation unit, a signal conversion and integration feedback loop and an isolation type LED power supply power conversion and output circuit, a traditional non-isolation and single dimming control design is changed into a design that a dimming control circuit and an output and feedback loop have electrical isolation performance; and meanwhile, the isolation control functions of three channels of voltage isolation control, current isolation control and dimming isolation control are realized.

Description

Technical Field

[0001] The invention relates to the field of LED power supplies, and in particular to a three-channel isolation control feedback loop circuit. Background Art

[0002] In the traditional design of LED industry driver power supply, the dimming control circuit is non-isolated from the output and feedback loop, and only has dimming signal control. With the upgrading of regulations in countries around the world, the dimming control circuit needs to be electrically isolated from the output and feedback loop. Summary of the invention

[0003] In order to solve the above problems, the present technical solution provides a three-channel isolation control feedback loop circuit.

[0004] To achieve the above purpose, the technical solution is as follows:

[0005] A three-channel isolation control feedback loop circuit, comprising:

[0006] A signal generating unit, used for outputting a voltage PWM signal, a current PWM signal and a dimming PWM signal;

[0007] A signal conversion integration feedback loop includes an optocoupler U1, wherein the positive electrode of the light-emitting end of the optocoupler U1 receives a voltage PWM signal, the negative electrode is grounded, the collector receives a voltage VCC, the emitter is connected to the positive phase end of the operational amplifier unit U4, and the negative phase end is used to receive the collected voltage at the output end. The output end of the operational amplifier unit U4 is sequentially connected to the negative electrode of the light-emitting end of the optocoupler U7 through a reverse diode D2 and a resistor R12, and the positive electrode of the light-emitting end of the optocoupler U7 receives the voltage VCC;

[0008] The signal conversion integration feedback loop also includes an optocoupler U2, the positive electrode of the light-emitting end of the optocoupler U2 receives the current PWM signal, the negative electrode is grounded, the collector receives the voltage VCC, the emitter is connected to the positive phase end of the operational amplifier unit U5, the positive phase end of the operational amplifier unit U5 is connected to the output end, the output end is connected to the positive phase end of the operational amplifier unit U6, the inverting end of the operational amplifier unit U6 receives the collection current of the output end, and the output end of the operational amplifier unit U6 is connected to the resistor R12 through the reverse diode D3;

[0009] The signal conversion integration feedback loop also includes an optocoupler U3, the positive electrode of the light-emitting end of the optocoupler U3 receives the dimming PWM signal, the negative electrode is grounded, the collector is connected to the positive phase end of the operational amplifier unit U6, and the emitter is grounded;

[0010] The isolated LED power supply power conversion output circuit includes a control unit U8, the receiving end of the control unit U8 is connected to the emitter and collector of the optical coupler U7 for collecting the current control signal, and the control unit U8 is also used to send a control signal to the output end.

[0011] In some embodiments, the emitter of the optical coupler U1 is connected to a resistor R2, and the resistor R2 is grounded through a resistor R3 and a capacitor C2;

[0012] The emitter of the optical coupler U2 is connected to a resistor R9, and the resistor R9 is grounded via a resistor R11 and a capacitor C4 respectively;

[0013] A resistor R15 is connected between the collector of the optical coupler U3 and the output end of the operational amplifier unit U5 , and a resistor R16 is further connected between the collector and the positive phase end of the operational amplifier unit U6 . The resistor R16 is grounded via a capacitor C6 .

[0014] In some embodiments, a resistor R5 and a capacitor C3 are disposed between the output terminal and the inverting terminal of the operational amplifier unit U4 , and a resistor R14 and a capacitor C5 are disposed between the output terminal and the inverting terminal of the optical coupler U6 .

[0015] In some embodiments, the isolated LED power supply power conversion output circuit further includes a transformer T1, one end of the primary coil of the transformer T1 receives the voltage Vin, the other end is connected to the drain of the MOS tube Q1, the source is grounded, and the gate is connected to the main control unit U8;

[0016] One end of the secondary coil of the transformer T1 is connected to the positive electrode of the output terminal through a diode D1, and the other end is connected to the negative electrode of the output terminal through a resistor R4.

[0017] In some embodiments, the positive electrode of the output terminal is grounded through resistors R6 and R10 in sequence, and the resistor R6 and R10 are used to collect voltage signals for the operational amplifier unit U4.

[0018] In some embodiments, the negative electrode of the output terminal collects a current signal for the operational amplifier unit U6 through a resistor R7.

[0019] The beneficial effects of this application are:

[0020] This application transforms the traditional non-isolated and single dimming control design into a design in which the dimming control circuit has electrical isolation performance from the output and feedback loop, and simultaneously has isolation control functions for three channels: voltage isolation control, current isolation control, and dimming isolation control. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below.

[0022] Figure 1 It is a schematic structural diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] Please refer to Figure 1 As shown, a three-channel isolation control feedback loop circuit includes:

[0025] A signal generating unit, used for outputting a voltage PWM signal, a current PWM signal and a dimming PWM signal;

[0026] A signal conversion integration feedback loop includes an optocoupler U1, wherein the positive electrode of the light-emitting end of the optocoupler U1 receives a voltage PWM signal, the negative electrode is grounded, the collector receives a voltage VCC, the emitter is connected to the positive phase end of the operational amplifier unit U4, and the negative phase end is used to receive the collected voltage at the output end. The output end of the operational amplifier unit U4 is sequentially connected to the negative electrode of the light-emitting end of the optocoupler U7 through a reverse diode D2 and a resistor R12, and the positive electrode of the light-emitting end of the optocoupler U7 receives the voltage VCC;

[0027] The signal conversion integration feedback loop also includes an optocoupler U2, the positive electrode of the light-emitting end of the optocoupler U2 receives the current PWM signal, the negative electrode is grounded, the collector receives the voltage VCC, the emitter is connected to the positive phase end of the operational amplifier unit U5, the positive phase end of the operational amplifier unit U5 is connected to the output end, the output end is connected to the positive phase end of the operational amplifier unit U6, the inverting end of the operational amplifier unit U6 receives the collection current of the output end, and the output end of the operational amplifier unit U6 is connected to the resistor R12 through the reverse diode D3;

[0028] The signal conversion integration feedback loop also includes an optocoupler U3, the positive electrode of the light-emitting end of the optocoupler U3 receives the dimming PWM signal, the negative electrode is grounded, the collector is connected to the positive phase end of the operational amplifier unit U6, and the emitter is grounded;

[0029] The isolated LED power supply power conversion output circuit includes a control unit U8, the receiving end of the control unit U8 is connected to the emitter and collector of the optical coupler U7 for collecting the current control signal, and the control unit U8 is also used to send a control signal to the output end.

[0030] In this embodiment, the emitter of the optical coupler U1 is connected to a resistor R2, and the resistor R2 is grounded through a resistor R3 and a capacitor C2;

[0031] The emitter of the optical coupler U2 is connected to a resistor R9, and the resistor R9 is grounded via a resistor R11 and a capacitor C4 respectively;

[0032] A resistor R15 is connected between the collector of the optical coupler U3 and the output end of the operational amplifier unit U5 , and a resistor R16 is further connected between the collector and the positive phase end of the operational amplifier unit U6 . The resistor R16 is grounded via a capacitor C6 .

[0033] In this embodiment, a resistor R5 and a capacitor C3 are provided between the output terminal and the inverting terminal of the operational amplifier unit U4 , and a resistor R14 and a capacitor C5 are provided between the output terminal and the inverting terminal of the optical coupler U6 .

[0034] In this embodiment, the isolated LED power supply power conversion output circuit further includes a transformer T1, one end of the primary coil of the transformer T1 receives the voltage Vin, the other end is connected to the drain of the MOS tube Q1, the source is grounded, and the gate is connected to the main control unit U8;

[0035] One end of the secondary coil of the transformer T1 is connected to the positive electrode of the output terminal through a diode D1, and the other end is connected to the negative electrode of the output terminal through a resistor R4.

[0036] In this embodiment, the positive electrode of the output terminal is grounded through the resistor R6 and the resistor R10 in sequence, and the resistor R6 and the resistor R10 are used to collect voltage signals for the operational amplifier unit U4.

[0037] In this embodiment, the negative electrode of the output terminal collects the current signal for the operational amplifier unit U6 through the resistor R7.

[0038] The circuit of the present invention is composed of a voltage / current / brightness control unit, an isolation optocoupler, a feedback loop, a primary-secondary isolation optocoupler, and an LED power supply power conversion circuit;

[0039] Among them, the voltage / current / brightness control unit generates three PWM signals corresponding to the voltage / current / dimming control signals required by the LED power supply. The PWM duty ratios of these three signals determine the voltage / current and brightness values ​​respectively; the optocoupler is responsible for isolating and transmitting these three PWM signals to the feedback loop as a reference. The feedback loop samples the voltage and current signals at the output end of the LED power supply, compares them with the reference through the operational amplifier, and then controls the operation of the LED power conversion circuit through the primary and secondary optocoupler isolation to achieve the control of the predetermined output voltage, output current, and dimming brightness;

[0040] This application meets the safety regulations of various countries and greatly improves the safety of application products; the control signal is physically isolated from the output power level circuit, has a stronger ability to resist impact interference, and better protects the control signal end equipment; it has 3 independent channel isolation signal control, which makes the output characteristic parameter variability of the LED power supply more flexible and the applicability of the product is wider.

[0041] Specifically, the present application consists of three parts: A, B, and C. A is a voltage / current / dimming signal generation unit, B is a signal conversion integration feedback loop of three channels, and C is an isolated LED power supply power conversion output circuit. The specific working principle is as follows:

[0042] The control unit in part A generates three PWM signals corresponding to voltage / current / brightness according to application requirements. The voltage PWM signal drives the optocoupler U1 through R1, the current PWM signal drives the optocoupler U2 through R8, and the brightness PWM signal drives U3 through R13, and transmits the three PWM signals to the circuit in part B.

[0043] In the circuit of part B, the voltage PWM signal transmitted by U1 is filtered and divided by resistors and capacitors through R2, R3, and C2 to form a voltage reference signal to U4; U4, C3, and R5 form a voltage feedback loop to compare the output voltage divided signal collected by R6 and R10 from part C with the voltage reference signal. When the output voltage is higher than the reference voltage, U4 outputs a low level and forms a feedback current through D2, R12, and U7, driving the optocoupler U7 to conduct and the signal U8 fed back to part C rises, controlling the change of the power conversion circuit and causing the output voltage to drop; conversely, when the output voltage is lower than the reference voltage, U4 outputs a high level, no current passes through D2 in the reverse direction, the driving current of R12 and U7 drops, the signal coupled from U7 to U8 drops and controls the change of the power conversion circuit to cause the output voltage to drop, thereby realizing voltage control;

[0044] Similarly, in the circuit of part B, the current PWM signal transmitted by U2 is filtered and divided by resistors and capacitors through R9, R11, and C4 to form a current reference signal to U5. The inverting phase of U5 is connected to the output to form a voltage follower circuit. The amplitude of the current reference signal of the same phase input is equal to the output, and the current reference is given to U6 through R15, R16, and C6; U6, R14, and C5 form a current feedback loop, and the output current signal collected by R4 in part C and transmitted through R7 is compared with the current reference. When the output current is higher than the reference, U6 outputs a low level and forms a feedback current through D3, R12, and U7, driving the optocoupler U7 to conduct and feedback to the U8 signal of part C to rise, controlling the change of the power conversion circuit to reduce the output current; conversely, when the output current is lower than the reference, U6 outputs a high level, D3 has no current flowing in the reverse direction, the driving current of R12 and U7 decreases, and the signal coupled to U8 by U7 decreases and controls the change of the power conversion circuit to reduce the output current, thereby realizing the control of constant current;

[0045] Similarly, in the circuit of part B, the brightness PWM signal transmitted by U3 is reflected in the conduction and cutoff of the triode inside U3, that is, after the current signal output by U5 passes through R15, the PWM signal transmitted by U3 will be loaded onto the current signal for the second time, and a current reference PWM signal with the same duty cycle as the brightness PWM signal will be generated at the R15 end, that is: the current signal transmitted by U2 will be modulated by the brightness signal transmitted by U3, so as to achieve the modulation of the 0-100% duty cycle of the dimming signal based on the current established current value, realize the 0-100% ratio division under a certain current value, and finally reflect the 0-100% dimming range;

[0046] The circuit of Part C is a currently common isolated power conversion circuit, in which U8 is a rate conversion control IC. U8 drives Q1 to work, transmits energy to the secondary through T1 isolation, and outputs it after rectification and filtering through D1 and C1; R6 and R10 detect the output voltage, divide the voltage to get a signal of appropriate amplitude and feed it back to U4; R4 is a current sampling resistor, and the sampled current signal is fed back to U6 through R7.

[0047] According to actual application requirements, the control unit of part A generates three PWM signals with independent duty cycle values, corresponding to voltage / current / brightness values ​​respectively, and then transmits them to the circuit of part B through R1, U1, R8, U2, R13, and U3 for isolation.

[0048] The circuit of Part B is divided into 5 parts: a voltage feedback loop composed of R2, R3, C2, U4, C3, R5, and D2, a current signal follower circuit composed of R9, R11, C4, U5, and R15, a dimming signal modulation filter circuit composed of U3, R16, and C6, a current feedback loop composed of U6, C5, R14, and D3, and a primary-secondary isolation feedback circuit composed of R12 and U7.

[0049] The circuit of part C is divided into 4 parts: the primary side power conversion circuit is composed of U8, Q1, and T1, the secondary side power rectification and filtering output circuit is composed of D1 and C1, the output voltage sampling and voltage divider circuit is composed of R6 and R10, and the output current detection sampling circuit is composed of R4 and R7.

[0050] The voltage PWM signal transmitted by U1 is given to the non-inverting input of U4 after RC filtering and voltage division. The voltage signal sampled by R6 and R10 is given to the inverting input of U4 for comparison with the non-inverting end. The output of U4 drives U7 through D2 and R12 to feed back to the primary side U8 to control the output voltage of Q1 and T1. The current PWM signal transmitted by U2 is given to the follower composed of U5 after RC filtering and voltage division. The output of the current reference signal of equal value is output to R15, and then modulated by the transistor inside U3 to form a current reference signal with the same duty cycle as the dimming signal. After filtering by R16 and C6, it is given to the non-inverting input of U6. The current signal sampled by R4 and R7 is given to the inverting input of U6 for comparison with the non-inverting end. The output of U6 drives U7 through D3 and R12 to feed back to the primary side U8 to control the output current of Q1 and T1. The current is a direct indicator of the brightness of the LED lamp.

[0051] The above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application. Other principles and basic structures that are the same or similar to those of the present application are within the protection scope of the present application.

Claims

1. A three-channel isolation control feedback loop circuit, characterized in that: include; A signal generating unit, used for outputting a voltage PWM signal, a current PWM signal and a dimming PWM signal; A signal conversion integration feedback loop includes an optocoupler U1, wherein the positive electrode of the light-emitting end of the optocoupler U1 receives a voltage PWM signal, the negative electrode is grounded, the collector receives a voltage VCC, the emitter is connected to the positive phase end of the operational amplifier unit U4, and the negative phase end is used to receive the collected voltage at the output end. The output end of the operational amplifier unit U4 is sequentially connected to the negative electrode of the light-emitting end of the optocoupler U7 through a reverse diode D2 and a resistor R12, and the positive electrode of the light-emitting end of the optocoupler U7 receives the voltage VCC; The signal conversion integration feedback loop also includes an optocoupler U2, the positive electrode of the light-emitting end of the optocoupler U2 receives the current PWM signal, the negative electrode is grounded, the collector receives the voltage VCC, the emitter is connected to the positive phase end of the operational amplifier unit U5, the positive phase end of the operational amplifier unit U5 is connected to the output end, the output end is connected to the positive phase end of the operational amplifier unit U6, the inverting end of the operational amplifier unit U6 receives the collection current of the output end, and the output end of the operational amplifier unit U6 is connected to the resistor R12 through the reverse diode D3; The signal conversion integration feedback loop also includes an optocoupler U3, the positive electrode of the light-emitting end of the optocoupler U3 receives the dimming PWM signal, the negative electrode is grounded, the collector is connected to the positive phase end of the operational amplifier unit U6, and the emitter is grounded; The isolated LED power supply power conversion output circuit includes a control unit U8, the receiving end of the control unit U8 is connected to the emitter and collector of the optical coupler U7 for collecting the current control signal, and the control unit U8 is also used to send a control signal to the output end.

2. The three-channel isolation control feedback loop circuit according to claim 1, characterized in that: The emitter of the optical coupler U1 is connected to a resistor R2, and the resistor R2 is grounded via a resistor R3 and a capacitor C2 respectively; The emitter of the optical coupler U2 is connected to a resistor R9, and the resistor R9 is grounded via a resistor R11 and a capacitor C4 respectively; A resistor R15 is connected between the collector of the optical coupler U3 and the output end of the operational amplifier unit U5 , and a resistor R16 is further connected between the collector and the positive phase end of the operational amplifier unit U6 . The resistor R16 is grounded via a capacitor C6 .

3. The three-channel isolation control feedback loop circuit according to claim 1, characterized in that: A resistor R5 and a capacitor C3 are provided between the output terminal and the inverting terminal of the operational amplifier unit U4 , and a resistor R14 and a capacitor C5 are provided between the output terminal and the inverting terminal of the optical coupler U6 .

4. The three-channel isolation control feedback loop circuit according to claim 1, characterized in that: The isolated LED power supply power conversion output circuit also includes a transformer T1, one end of the primary coil of the transformer T1 receives the voltage Vin, the other end is connected to the drain of the MOS tube Q1, the source is grounded, and the gate is connected to the main control unit U8; One end of the secondary coil of the transformer T1 is connected to the positive electrode of the output terminal through a diode D1, and the other end is connected to the negative electrode of the output terminal through a resistor R4.

5. The three-channel isolation control feedback loop circuit according to claim 4, characterized in that: The positive electrode of the output terminal is grounded through the resistor R6 and the resistor R10 in sequence, and the resistor R6 and the resistor R10 are used to collect voltage signals for the operational amplifier unit U4.

6. The three-channel isolation control feedback loop circuit according to claim 5, characterized in that: The negative electrode of the output terminal collects the current signal for the operational amplifier unit U6 through the resistor R7.

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