Constant-voltage power supply loop control circuit

Abstract

The utility model discloses a constant-voltage power supply loop control circuit, which comprises a first comparison module, a second comparison module, an impedance conversion module and a feedback module, the first input end of the first comparison module is connected with a reference voltage VREF, the second input end of the first comparison module is connected with an output voltage V + and the output end of the impedance conversion module, and the load is connected between the output voltage V + and the output voltage V-; the first input end of the second comparison module is connected with a reference voltage VREF, and the second input end of the second comparison module is connected with an output voltage V-; reference voltage VREF and VPWM signals are connected to the input end of the impedance conversion module; the input end of the feedback module is connected with the output end of the first comparison module and the output end of the second comparison module. The pulse width regulator is connected between the output end of the feedback module and output voltage V +. A stable and reliable constant voltage control circuit is provided, almost no temperature excursion exists, a perfect fixed proportion relation is formed through reasonable parameter setting, the output voltage and the duty ratio of a voltage control VPWM signal, and a hardware basis is provided for accurate voltage output.

Description

Technical Field

[0001] The utility model relates to the technical field of LED dimming drive power supply and switch power supply, in particular to a constant voltage power supply loop control circuit. Background Art

[0002] In the LED lighting industry, constant voltage lamps are popular among consumers for their extremely low failure rate, and LED dimming power supplies, which are control and drive components, are also favored by the market; however, constant voltage power supplies also have many problems. For example, it is not easy for batch-produced constant voltage power supplies to maintain a relatively consistent output voltage range, and errors may occasionally occur. In addition, some constant voltage power supplies may have serious temperature drift in high temperature environments. With the continuous upgrading of consumption, consumers have put forward higher requirements for the output voltage accuracy of dimming constant voltage power supplies. Utility Model Content

[0003] The utility model aims to solve at least one of the technical problems existing in the prior art. To this end, the utility model proposes a constant voltage power supply loop control circuit.

[0004] An embodiment of the utility model adopts a technical solution to solve its technical problem: a constant voltage power supply loop control circuit, including a first comparison module, a second comparison module, an impedance conversion module and a feedback module;

[0005] The first input terminal of the first comparison module is connected to the reference voltage VREF, the second input terminal is respectively connected to the output voltage V+ and the output terminal of the impedance conversion module, and the load is connected between the output voltage V+ and the output voltage V-;

[0006] The first input terminal of the second comparison module is connected to the reference voltage VREF, and the second input terminal is connected to the output voltage V-;

[0007] The input end of the impedance conversion module is connected to the reference voltage VREF and the VPWM signal;

[0008] The input end of the feedback module is connected to the output end of the first comparison module and the output end of the second comparison module respectively, and the pulse width regulator is connected between the output end of the feedback module and the output voltage V+.

[0009] As one of the preferred embodiments of the utility model, the first comparison module includes a comparator U1 A and resistors R5-7, the positive input terminal of the comparator U1 A is connected to the reference voltage VREF, the reverse input terminal of the comparator U1 A is respectively connected to one end of the resistor R5, one end of the resistor R6 and one end of the resistor R7, the other end of the resistor R5 is connected to the output voltage V+, the other end of the resistor R6 is connected to the impedance conversion module, the GND terminal of the comparator U1 A and the other end of the resistor R7 are grounded, the power supply terminal of the comparator U1 A is connected to the voltage VCC, and the output terminal of the comparator U1A is respectively connected to the second comparison module and the feedback module.

[0010] As one of the preferred embodiments of the utility model, the second comparison module includes a comparator U1 B and resistors R9-11, the reverse input end of the comparator U1 B is connected to the output voltage V- through the resistor R11, the positive input end of the comparator U1B is respectively connected to one end of the resistor R9 and one end of the resistor R10, the other end of the resistor R10 is grounded, the other end of the resistor R9 is connected to the reference voltage VREF, and the output end of the comparator U1 B is respectively connected to the second comparison module and the feedback module.

[0011] As one of the preferred embodiments of the utility model, the impedance conversion module includes an operational amplifier OP1, a resistor R1, a resistor R3, a capacitor C2 and a transistor Q1, the positive input end of the operational amplifier OP1 is respectively connected to one end of the resistor R3 and the collector of the transistor Q1, the other end of the resistor R3 is connected to the reference voltage VREF, the base of the transistor Q1 is connected to the VPWM signal via the resistor R1, the emitter of the transistor Q1 is respectively connected to one end of the capacitor C2 and the ground end, the reverse input end of the operational amplifier OP1 and the output end of the operational amplifier OP1 are connected to the first comparison module, and the power supply end of the operational amplifier OP1 is respectively connected to the other end of the capacitor C2 and the VCC end.

[0012] As one of the preferred embodiments of the utility model, a constant voltage power supply loop control circuit further includes a low-pass filter module connected to the positive input terminal of the operational amplifier OP1 and between the collector and the emitter of the transistor Q1.

[0013] As one of the preferred embodiments of the utility model, the low-pass filter module includes a resistor R4 and a capacitor C1, one end of the resistor R4 is connected to the collector of the transistor Q1, the other end of the resistor R4 is respectively connected to the positive input end of the operational amplifier OP1 and one end of the capacitor C1, and the other end of the capacitor C1 is connected to the emitter of the transistor Q1.

[0014] As one of the preferred embodiments of the utility model, the feedback module includes an optocoupler DU1, one end of the optocoupler DU1 light emitter is connected to the VCC end, the other end of the optocoupler DU1 light emitter is respectively connected to the output end of the first comparison module and the output end of the second comparison module, one end of the optocoupler DU1 light receiver is connected to the pulse width regulator, and the other end of the optocoupler DU1 light receiver is grounded.

[0015] The beneficial effects of the utility model are as follows: a constant voltage power supply loop control circuit comprises a first comparison module, a second comparison module, an impedance transformation module and a feedback module; the first input end of the first comparison module is connected to a reference voltage VREF, the second input end is respectively connected to an output voltage V+ and an output end of the impedance transformation module, and a load is connected between the output voltage V+ and the output voltage V-; the first input end of the second comparison module is connected to the reference voltage VREF, and the second input end is connected to the output voltage V-; the input end of the impedance transformation module is connected to the reference voltage VREF and a VPWM signal; the input end of the feedback module is respectively connected to the output end of the first comparison module and the output end of the second comparison module, and a pulse width regulator is connected between the output end of the feedback module and the output voltage V+; a stable and reliable constant voltage control circuit is provided, which has almost no temperature drift, and through reasonable parameter setting, the output voltage and the duty cycle of the voltage control VPWM signal form a perfect fixed proportional relationship, providing a hardware basis for accurate voltage output. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0017] Figure 1 It is an application schematic diagram of a constant voltage power supply loop control circuit;

[0018] Figure 2 It is a circuit schematic diagram of a constant voltage power supply loop control circuit;

[0019] Figure 3 is a circuit schematic diagram of a first comparison module;

[0020] Figure 4 is a circuit schematic diagram of a second comparison module;

[0021] Figure 5 This is the circuit schematic diagram of the impedance transformation module. DETAILED DESCRIPTION

[0022] This section will describe in detail the specific embodiments of the utility model. The preferred embodiments of the utility model are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the utility model, but it cannot be understood as a limitation on the protection scope of the utility model.

[0023] In the description of the present utility model, the meaning of "more than" is more than two, "greater than", "less than", "exceed" etc. are understood to exclude the number itself, and "above", "below", "within" etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0024] In the description of the present invention, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0025] In the present invention, unless otherwise clearly defined, the words "set", "install", "connect" and the like should be understood in a broad sense, for example, they can be directly connected or indirectly connected through an intermediate medium; they can be fixedly connected or detachably connected or integrally formed; they can be mechanically connected; they can be the internal connection of two elements or the interaction relationship between two elements. Those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0026] Reference Figures 1 to 5 , a constant voltage power supply loop control circuit, comprising a first comparison module 10, a second comparison module 20, an impedance transformation module 30 and a feedback module 40;

[0027] The first input terminal of the first comparison module 10 is connected to the reference voltage VREF, the second input terminal is connected to the output voltage V+ and the output terminal of the impedance conversion module 30 respectively, and the load is connected between the output voltage V+ and the output voltage V-;

[0028] The first input terminal of the second comparison module 20 is connected to the reference voltage VREF, and the second input terminal is connected to the output voltage V-;

[0029] The input end of the impedance conversion module 30 is connected to the reference voltage VREF and the VPWM signal;

[0030] The input end of the feedback module 40 is connected to the output end of the first comparison module 10 and the output end of the second comparison module 20 respectively, and the pulse width regulator is connected between the output end of the feedback module 40 and the output voltage V+.

[0031] The working principle of the utility model is as follows:

[0032] 1. Reference Figure 1 After the AC mains passes through module ①, it provides a steamed wave with a frequency double that of the mains to module ②. Module ② boosts and rectifies the input steamed wave into a DC voltage. After module ② outputs the DC voltage, module ③ steps it down. Under the action of the constant voltage loop control circuit, a specific current or voltage is formed according to the VPWM signal duty cycle and the output current loop parameters.

[0033] 2. Reference Figure 2-5 In the constant voltage loop control circuit, when the loop is under normal control, the first comparison module 10 includes a comparator U1A and resistors R5-7, the positive input terminal of the comparator U1A is connected to the reference voltage VREF, the reverse input terminal of the comparator U1A is respectively connected to one end of the resistor R5, one end of the resistor R6 and one end of the resistor R7, the other end of the resistor R5 is connected to the output voltage V+, the other end of the resistor R6 is connected to the impedance transformation module 30, the GND terminal of the comparator U1A and the other end of the resistor R7 are grounded, the power supply terminal of the comparator U1A is connected to the voltage VCC, and the output terminal of the comparator U1A is respectively connected to the second comparison module 20 and the feedback module 40; specifically, the voltage of the 1st pin and the 4th pin of the comparator U1A are equal, the voltage of the 1st pin of U1A is the internal reference voltage VREF of the chip, which has the characteristics of high precision and small temperature drift, and the comparator U1A The voltage at pin 4 of A is generated by the output voltage V+, the reference voltage VREF and VPWM. Under normal working conditions, the internal reference voltage VREF of the chip is a fixed value, and the pin 4 of the comparator U1 A is also a fixed value. When the VPWM signal is at different duty cycles, the loop will adjust the duty cycle of the primary pulse width regulator output to change the power supply output voltage V+ so that its voltage reaches the same voltage as the pin 1 of the comparator (that is, the voltage of VREF) at pin 4 of the comparator U1 A after voltage division through resistors R5, R6 and R7. That is, controlling the duty cycle of VPWM can control the value of the output voltage V+.

[0034] 3. In the impedance transformation module 30, the impedance transformation module 30 includes an operational amplifier OP1, a resistor R1, a resistor R3, a capacitor C2 and a transistor Q1. The positive input terminal of the operational amplifier OP1 is respectively connected to one end of the resistor R3 and the collector of the transistor Q1. The other end of the resistor R3 is connected to the reference voltage VREF. The base of the transistor Q1 is connected to the VPWM signal through the resistor R1. The emitter of the transistor Q1 is respectively connected to one end of the capacitor C2 and the ground. The reverse input terminal of the operational amplifier OP1 and the operational amplifier OP1 are connected to the collector of the transistor Q1. The output end is connected to the first comparison module 10, and the power supply end of the operational amplifier OP1 is respectively connected to the other end of the capacitor C2 and the VCC end; specifically, when VPWM outputs a duty cycle corresponding to the voltage, the transistor Q1 will enter an on-off state opposite to the corresponding duty cycle, so that the voltage VREF is chopped through the resistor R3, and then filtered into a direct current through the low-pass filter module 50 composed of the resistor R4 and the capacitor C1; the functions of the resistors R5, R6, and R7 are to set the maximum voltage value of the output voltage V+, and the resistor R7 can also discharge the charge of the 4th pin of the comparator U1 A when the comparator U1 A is powered off; the operational amplifier OP1 as a follower in the above circuit has the functions of impedance transformation and isolation buffering.

[0035] 4. In the second comparison module 20, the second comparison module 20 includes a comparator U1 B and resistors R9-11. The reverse input terminal of the comparator U1 B is connected to the output voltage V- through the resistor R11, and the positive input terminal of the comparator U1 B is respectively connected to one end of the resistor R9 and one end of the resistor R10, the other end of the resistor R10 is grounded, and the other end of the resistor R9 is connected to the reference voltage VREF. The output terminal of the comparator U1 B is respectively connected to the second comparison module 20 and the feedback module 40; specifically, the output Iout is used as the input terminal of the output current sampling, and its voltage is equal to the product of the current detection resistor R8 and the output current. After passing through the resistor R11, it is input to the 2nd pin of the comparator U1 B; under normal control of the loop, the voltages of the 2nd and 3rd pins of the comparator U1 B are almost equal, and the voltage of the 3rd pin of the comparator is generated after the resistor R9 and the resistor R10 divide the reference voltage VREF. Since the voltage VREF is a fixed value, when the resistance value of the resistor R9 or the resistor R10 changes, the comparator U1 The voltage at pin 3 of comparator U1 B will also change accordingly. The loop will adjust the duty cycle of the primary pulse width regulator output to change the output current so that pin 2 of comparator U1 B reaches the same voltage value as pin 3 of comparator U1 B.

[0036] 5. In the normal operation of the loop, the lower the voltage between pin 5 of comparator U1A and pin 7 of comparator U1B, the greater the current flowing through the diode inside the optocoupler DU1, the greater the current flowing from the feedback pin FB of the pulse width regulator to the ground (PGND) through the optocoupler DU1, the smaller the current output by the LED driver power supply to the lamp load, and the lower the voltage across the lamp load; the higher the voltage between pin 5 of comparator U1A and pin 7 of comparator U1B, the smaller the current flowing through the diode inside the optocoupler DU1, the smaller the current flowing from the feedback pin FB of the pulse width regulator to the ground (PGND) through the optocoupler DU1, the greater the current output by the LED driver power supply to the lamp load, and the higher the voltage across the lamp load.

[0037] 6. The advantages of the utility model are: providing a stable and reliable constant voltage control circuit with almost no temperature drift, and through reasonable parameter setting, the output voltage and the duty cycle of the voltage control VPWM signal form a perfect fixed ratio relationship, providing a hardware basis for accurate voltage output.

[0038] A constant voltage power supply loop control circuit also includes a low-pass filter module 50 connected to the positive input terminal of the operational amplifier OP1 and between the collector and emitter of the transistor Q1; as a preferred embodiment of the low-pass filter module 50, the low-pass filter module 50 includes a resistor R4 and a capacitor C1, one end of the resistor R4 is connected to the collector of the transistor Q1, the other end of the resistor R4 is respectively connected to the positive input terminal of the operational amplifier OP1 and one end of the capacitor C1, and the other end of the capacitor C1 is connected to the emitter of the transistor Q1.

[0039] The feedback module 40 includes an optocoupler DU1, one end of the optocoupler DU1 light emitter is connected to the VCC end, the other end of the optocoupler DU1 light emitter is respectively connected to the output end of the first comparison module 10 and the output end of the second comparison module 20, one end of the optocoupler DU1 light receiver is connected to the pulse width regulator, and the other end of the optocoupler DU1 light receiver is grounded.

[0040] Of course, the present invention is not limited to the above-mentioned embodiments, and technicians familiar with the field may make equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications and substitutions are all included in the scope defined by the claims of this application.

Claims

1. A constant voltage power supply loop control circuit, characterized in that: It comprises a first comparison module (10), a second comparison module (20), an impedance transformation module (30) and a feedback module (40); The first input end of the first comparison module (10) is connected to a reference voltage VREF, the second input end is respectively connected to an output voltage V+ and an output end of the impedance conversion module (30), and the load is connected between the output voltage V+ and the output voltage V-; The first input terminal of the second comparison module (20) is connected to a reference voltage VREF, and the second input terminal is connected to an output voltage V-; The input end of the impedance conversion module (30) is connected to a reference voltage VREF and a VPWM signal; The input end of the feedback module (40) is respectively connected to the output end of the first comparison module (10) and the output end of the second comparison module (20), and the pulse width regulator is connected between the output end of the feedback module (40) and the output voltage V+.

2. A constant voltage power supply loop control circuit according to claim 1, characterized in that: The first comparison module (10) comprises a comparator U1A and resistors R5-7, the positive input terminal of the comparator U1A is connected to a reference voltage VREF, the negative input terminal of the comparator U1A is respectively connected to one end of the resistor R5, one end of the resistor R6 and one end of the resistor R7, the other end of the resistor R5 is connected to an output voltage V+, the other end of the resistor R6 is connected to the impedance conversion module (30), the GND terminal of the comparator U1A and the other end of the resistor R7 are grounded, the power supply terminal of the comparator U1A is connected to a voltage VCC, and the output terminal of the comparator U1A is respectively connected to the second comparison module (20) and the feedback module (40).

3. A constant voltage power supply loop control circuit according to claim 1, characterized in that: The second comparison module (20) comprises a comparator U1B and resistors R9-11, the reverse input end of the comparator U1B is connected to the output voltage V- via the resistor R11, the forward input end of the comparator U1B is respectively connected to one end of the resistor R9 and one end of the resistor R10, the other end of the resistor R10 is grounded, the other end of the resistor R9 is connected to a reference voltage VREF, and the output end of the comparator U1B is respectively connected to the second comparison module (20) and the feedback module (40).

4. The constant voltage power supply loop control circuit according to claim 1, characterized in that: The impedance conversion module (30) comprises an operational amplifier OP1, a resistor R1, a resistor R3, a capacitor C2 and a transistor Q1, the positive input end of the operational amplifier OP1 is respectively connected to one end of the resistor R3 and the collector of the transistor Q1, the other end of the resistor R3 is connected to a reference voltage VREF, the base of the transistor Q1 is connected to a VPWM signal via the resistor R1, the emitter of the transistor Q1 is respectively connected to one end of the capacitor C2 and a ground end, the negative input end of the operational amplifier OP1 and the output end of the operational amplifier OP1 are connected to the first comparison module (10), and the power supply end of the operational amplifier OP1 is respectively connected to the other end of the capacitor C2 and a VCC end.

5. A constant voltage power supply loop control circuit according to claim 4, characterized in that: It also includes a low-pass filter module (50) connected between the positive input terminal of the operational amplifier OP1 and the collector and emitter of the transistor Q1.

6. A constant voltage power supply loop control circuit according to claim 5, characterized in that: The low-pass filter module (50) comprises a resistor R4 and a capacitor C1, one end of the resistor R4 is connected to the collector of the transistor Q1, the other end of the resistor R4 is respectively connected to the positive input end of the operational amplifier OP1 and one end of the capacitor C1, and the other end of the capacitor C1 is connected to the emitter of the transistor Q1.

7. The constant voltage power supply loop control circuit according to claim 1, characterized in that: The feedback module (40) comprises an optical coupler DU1, one end of the optical coupler DU1 light emitter is connected to the VCC end, the other end of the optical coupler DU1 light emitter is respectively connected to the output end of the first comparison module (10) and the output end of the second comparison module (20), one end of the optical coupler DU1 light receiver is connected to the pulse width regulator, and the other end of the optical coupler DU1 light receiver is grounded.

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