Voltage conversion circuit and LED driving system

Abstract

The embodiment of the invention discloses a voltage conversion circuit and an LED driving system. The voltage conversion circuit comprises an input end for receiving input voltage and an output end for providing output voltage. The feedback circuit is provided with an input end for receiving input voltage and an output end for providing feedback signals, the feedback circuit generates the feedback signals according to the input voltage, Vfb = k1 * Vin + a, Vfb is the value of the feedback signals, Vin is the input voltage, k1 is a constant smaller than 1, and a is the voltage stabilizing value of the voltage stabilizing diode. The first transistor has a first end receiving an input voltage and a control end receiving a feedback signal. When the input voltage is increased, the output voltage is increased, and the increasing amplitude of the output voltage is smaller than that of the input voltage. According to the voltage conversion circuit, the input voltage can be subjected to voltage conversion, relatively stable output voltage is provided for a post-stage driving chip, and the manufacturing cost is saved.

Description

Technical Field

[0001] This application relates to the technical field of voltage conversion circuits, and particularly to a voltage conversion circuit and an LED driving system. Background Art

[0002] In an LED driving system, the output voltage of a battery is usually higher than the operating voltage required by an LED driving chip. If the battery is directly connected to the LED driving chip, then when the input voltage increases, the power consumption of the LED driving chip increases. Excessive power consumption will cause the LED driving chip to generate a large amount of heat, resulting in a sharp rise in the temperature of the LED driving chip. When the temperature is too high, the LED driving chip will undergo overheat protection, affecting normal operation and seriously affecting the stability and reliability of the entire LED driving system. To prevent the LED driving chip from overheating and becoming unusable, a voltage conversion circuit needs to be added between the battery and the LED. Usually, a buck circuit is used to convert the higher battery voltage into a lower voltage suitable for the normal operation of the LED. However, since the buck circuit consists of many components, usually including a switching transistor, an inductor, a capacitor, a diode, and a control chip, etc. This not only increases the circuit design difficulty and wiring complexity but also raises the manufacturing cost of the PCB (printed circuit board).

[0003] Therefore, a voltage conversion circuit with low cost and capable of ensuring the normal operation of the LED driving chip is needed. Summary of the Invention

[0004] This application provides a voltage conversion circuit and an LED driving system, aiming to solve the problem of the excessively high cost of the voltage conversion circuit in the LED driving system.

[0005] According to the first aspect of this application, a voltage conversion circuit is provided. The voltage conversion circuit includes: an input terminal for receiving an input voltage; an output terminal for providing an output voltage; a feedback circuit having an input terminal, a zener diode, and an output terminal, where the input terminal receives the input voltage, the output terminal provides a feedback signal, and the feedback circuit generates the feedback signal according to the input voltage, where Vfb = k1×Vin + a, where Vfb is the value of the feedback signal, Vin is the input voltage, k1 is a constant less than 1, and a is the regulated voltage value of the zener diode; and a first transistor having a first terminal, a second terminal, and a control terminal, where the first terminal receives the input voltage, the control terminal receives the feedback signal, and the first transistor converts the input voltage into the output voltage under the control of the feedback signal; where when the input voltage increases, the output voltage increases, and the amplitude of the increase in the output voltage is less than the amplitude of the increase in the input voltage.

[0006] According to a second aspect of the present application, an LED driving system includes: the voltage conversion circuit according to any one of the first aspects described above; a driving circuit having a power supply terminal and N LED driving terminals, wherein the power supply terminal receives the output voltage provided by the voltage conversion circuit, where N is a positive integer; and single or multiple LEDs coupled between each LED driving terminal and the output terminal of the voltage conversion circuit; wherein the current flowing through the LEDs is controlled by the driving circuit.

[0007] Through one or more embodiments of the above embodiments of the present invention, at least the following technical effects can be achieved:

[0008] The voltage conversion circuit in the present application can convert the input voltage and provide a stable output voltage to the subsequent driving chip and load, saving manufacturing costs. Based on the feedback circuit in the voltage conversion circuit, when the input voltage increases, the feedback signal also increases. Although the voltage between the control terminal and the second terminal of the first transistor remains unchanged, and the voltage between the control terminal and the second terminal of the second transistor remains unchanged, during the process of increasing the input voltage, the increased part of the input voltage will be simultaneously distributed to the transistor and the driving chip, thereby achieving power consumption balance between the transistor and the driving chip, avoiding transistor burnout, and protecting the normal operation of the entire system. Description of the Drawings

[0009] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative efforts.

[0010] Figure 1 Shows a schematic circuit diagram of a voltage conversion circuit 100 according to an embodiment of the present application;

[0011] Figure 2 Shows a schematic circuit diagram of a voltage conversion circuit 200 according to another embodiment of the present application;

[0012] Figure 3 Shows a schematic circuit diagram of an LED driving system 300 according to an embodiment of the present application. Detailed Embodiments

[0013] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present application.

[0014] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application described here can be implemented in an order different from those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0015] It should be understood that in the following description, a "circuit" refers to a conductive loop formed by at least one element or sub-circuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "connected to" another element or when an element / circuit is said to be "connected between" two nodes, it can be directly coupled or connected to another element or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between the two.

[0016] Figure 1 The circuit structure diagram of a voltage conversion circuit 100 according to an embodiment of the present application is shown. The voltage conversion circuit 100 includes an input terminal IN, an output terminal OUT, a feedback circuit 10, and a first transistor M1. The input terminal IN receives an input voltage Vin, and the output terminal OUT provides an output voltage Vout. The feedback circuit 10 has an input terminal, a zener diode ZD1, and an output terminal. The input terminal receives the input voltage Vin, and the output terminal provides a feedback signal Vfb. The feedback circuit 10 generates the feedback signal Vfb according to the input voltage Vin, where Vfb = k1×Vin + a, k1 is a constant less than 1, and a is the regulated voltage value of the zener diode. When the input voltage Vin increases, the output voltage Vout increases, and the amplitude of the increase in the output voltage Vout is less than the amplitude of the increase in the input voltage Vin. In Figure 1 In the illustrated embodiment, the first transistor M1 is an N-type field-effect transistor. The range of the input voltage Vin is between 9V and 16V. In one embodiment, the first transistor M1 is a discrete device.

[0017] Figure 2 shows a schematic circuit diagram of a voltage conversion circuit 200 according to another embodiment of the present application. In Figure 2 the shown voltage conversion circuit 200, the voltage conversion circuit 100 includes an input terminal IN, an output terminal OUT, a feedback circuit 10, a first transistor M1, a second transistor M2, a first resistor R1, and a second resistor R2. The input terminal IN receives an input voltage Vin, and the output terminal OUT provides an output voltage Vout. The feedback circuit 10 has an input terminal and an output terminal. The input terminal receives the input voltage Vin, and the output terminal provides a feedback signal Vfb. The feedback circuit 10 generates the feedback signal Vfb according to the input voltage Vin, where Vfb = k1×Vin + a, where vfb is the value of the feedback signal, Vin is the input voltage, k1 is a constant less than 1, and a is the regulated voltage value of the zener diode. The first transistor M1 has a first terminal, a second terminal, and a control terminal. The first terminal receives the input voltage Vin, and the control terminal receives the feedback signal Vfb. The second transistor M2 has a first terminal, a second terminal, and a control terminal. The first terminal receives the input voltage Vin, and the control terminal receives the feedback signal Vfb.

[0018] In Figure 2 the shown embodiment, the feedback circuit 10 includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a zener diode ZD1. The fourth resistor R4 has a first terminal and a second terminal, and the first terminal is coupled to the input terminal IN. The fifth resistor R5 has a first terminal and a second terminal, and the first terminal is coupled to the second terminal of the fourth resistor R4, and the second terminal is coupled to the reference ground. The sixth resistor R6 has a first terminal and a second terminal, and the first terminal is coupled to the input terminal IN. The zener diode ZD1 has a positive terminal and a negative terminal, and the positive terminal is coupled to the second terminal of the fourth resistor R4, and the negative terminal is coupled to the second terminal of the sixth resistor R6 and outputs the feedback signal Vfb. The feedback circuit 10 further includes a first capacitor C1. The first capacitor C1 has a first terminal and a second terminal, and the first terminal is coupled to the negative terminal of the zener diode ZD1, and the second terminal is coupled to the reference ground.

[0019] Continuing Figure 2 the description, the fourth resistor R4 and the fifth resistor R5 form a voltage dividing circuit. The voltage value of the feedback signal Vfb is equal to the voltage value at the first terminal of the fifth resistor R5 plus the regulated voltage value of the zener diode ZD1, that is, k1 is R5 / (R4 + R5), and a is the regulated voltage value of the zener diode ZD1. The first capacitor C1 is used for voltage regulation to prevent voltage fluctuations.

[0020] The feedback signal Vfb controls the first transistor M1 and the second transistor M2 to turn on and operate in the variable resistance region. For the first transistor M1, Vout = Vfb - Vfbs1, where Vfbs1 is the gate-source voltage between the gate and the source of the first transistor M1. When the input voltage Vin increases, the feedback signal Vfb increases with the increase of the input voltage Vin, and the voltage Vfbs1 between the control terminal and the second terminal of the first transistor M1 remains unchanged (there is actually a slight change, but the change amplitude is small and can be ignored in the calculation of this application), and the voltage Vfbs2 between the control terminal and the second terminal of the second transistor M2 remains unchanged. According to the formula, the output voltage Vout increases. When the input voltage Vin decreases, the feedback signal Vfb decreases with the decrease of the input voltage Vin, the voltage Vfbs1 between the control terminal and the second terminal of the first transistor M1 remains almost unchanged, and the voltage Vfbs2 between the control terminal and the second terminal of the second transistor M2 remains almost unchanged. According to the formula, the output voltage Vout decreases.

[0021] In Figure 2 In the illustrated embodiment, the source of the first transistor M1 in the voltage conversion circuit 100 is connected to the output terminal of the voltage conversion circuit 200 through the first resistor R1, and the source of the second transistor M2 is connected to the output terminal of the voltage conversion circuit 200 through the second resistor R2. When the first transistor M1 and the second transistor M2 operate in the variable resistance region under the control of an appropriate feedback signal Vfb, considering that the parameters of the first transistor M1 and the second transistor M2 cannot be exactly the same, which will cause uneven current distribution in the branches where the first transistor M1 and the second transistor M2 are located. The first resistor R1 and the second resistor R2 are provided as current-sharing resistors, and the voltage-dividing characteristics of the resistors are used to adjust the current of each branch, so that the currents on the branch of the first transistor M1 and the branch of the second transistor M2 are nearly equal. Since the resistance value of the current-sharing resistor is small and the voltage drop across it accounts for a small proportion, the output voltage Vout can still be calculated by Vout = Vfb - Vfbs1 when calculating the output voltage Vout.

[0022] It should be noted that in Figure 2 In the illustrated voltage conversion circuit 200, the change amplitude of the output voltage Vout is smaller than the change amplitude of the input voltage Vin. That is, the output voltage Vout will change within a range, and this range is determined based on the ratio of the feedback signal Vfb output by the feedback circuit 10 to the input voltage Vin. When the input voltage Vin increases, the feedback signal Vfb increases accordingly. Although the voltage between the control terminal and the second terminal of the first transistor M1 remains unchanged, and the voltage between the control terminal and the second terminal of the second transistor M2 remains unchanged, during the process of increasing the input voltage Vin, the voltage difference between the input terminal and the output terminal of the voltage conversion circuit 200 will become larger.

[0023] In Figure 2 In the illustrated embodiment, the first transistor M1 is an N-type field effect transistor, and the second transistor M2 is an N-type field effect transistor. The first ends of the first transistor M1 and the second transistor M2 are drain ends, the second ends are source ends, and the control ends are gate ends. In one embodiment, the first transistor M1 and the second transistor M2 are discrete devices.

[0024] Figure 3 FIG. shows a schematic circuit structure of an LED driving system 300 according to an embodiment of the present application. The LED driving system 300 includes a voltage conversion circuit 100, a driving circuit 31, and single or multiple LEDs. The voltage conversion circuit receives an input voltage Vin and provides an output voltage Vout. The driving circuit 31 has a power supply terminal VS and a plurality of LED driving terminals Led1 to LedN. The power supply terminal VS receives the output voltage Vout provided by the voltage conversion circuit 100. The single or multiple LEDs are coupled between each LED driving terminal and the output terminal of the voltage conversion circuit, and the current flowing through the LEDs is controlled by the driving circuit 31. Exemplarily, Figure 3 The driving circuit 31 in shows a plurality of driving chips. Each driving chip includes 16 LED driving terminals, and each LED driving terminal drives one LED. In some embodiments, the voltage conversion circuit 100 is configured to step down the input voltage Vin, and the output voltage Vout is less than the input voltage Vin.

[0025] In Figure 3In the illustrated embodiment, the voltage conversion circuit 100 includes an input terminal IN, an output terminal OUT, a feedback circuit 10, a first transistor M1, a second transistor M2, a third transistor M3, a first resistor R1, a second resistor R2, and a third resistor R3. The input terminal IN receives an input voltage Vin, and the output terminal OUT provides an output voltage Vout. The feedback circuit 10 has an input terminal and an output terminal. The input terminal receives the input voltage Vin, and the output terminal provides a feedback signal Vfb, which generates the feedback signal Vfb according to the input voltage Vin. The first transistor M1 has a first terminal, a second terminal, and a control terminal. The first terminal receives the input voltage Vin, and the control terminal receives the feedback signal Vfb. The first transistor M1 operates under the control of the feedback signal Vfb. The second transistor M2 has a first terminal, a second terminal, and a control terminal. The first terminal receives the input voltage Vin, and the control terminal receives the feedback signal Vfb. The second transistor M2 operates under the control of the feedback signal Vfb. The third transistor M3 has a first terminal, a second terminal, and a control terminal. The first terminal receives the input voltage Vin, and the control terminal receives the feedback signal Vfb. The third transistor M3 operates under the control of the feedback signal Vfb. The first resistor R1 has a first terminal and a second terminal. The first terminal is coupled to the second terminal of the first transistor M1, and the second terminal is coupled to the output terminal OUT. The second resistor R2 has a first terminal and a second terminal. The first terminal is coupled to the second terminal of the second transistor M2, and the second terminal is coupled to the output terminal OUT. The third resistor R3 has a first terminal and a second terminal. The first terminal is coupled to the second terminal of the third transistor M3, and the second terminal is coupled to the output terminal OUT.

[0026] When the input voltage Vin increases, the feedback signal Vfb increases, the voltage between the control terminal and the second terminal of the first transistor M1 remains almost unchanged, the voltage between the control terminal and the second terminal of the second transistor M2 remains almost unchanged, the voltage between the control terminal and the second terminal of the third transistor M3 remains almost unchanged, and the output voltage Vout increases. In Figure 3 the illustrated embodiment, the first transistor M1, the second transistor M2, and the third transistor M3 are all N-type field effect transistors. Compared with Figure 2 the circuit with only two transistors in the embodiment, Figure 3 the illustrated embodiment uses three transistors. For each additional transistor, the total current of the voltage conversion circuit will also increase accordingly, so that it can carry a larger power.

[0027] In Figure 3In the illustrated embodiment, the number of LEDs is multiple, and the driving circuit includes driving chips, such as driving chip U1 and driving chip U2. Each driving chip can drive up to N LEDs through multiple driving terminals Led1 to LedN on the chip. In some embodiments, the driving chip can be a chip with a thermal derating function. When the temperature exceeds a certain high-temperature threshold, it will adaptively reduce the driving current of the LEDs, reducing the system thermal power consumption, and protecting the normal operation of the entire system while ensuring that the LED load does not go out. In one embodiment, the high-temperature threshold is programmable. In one embodiment, the high-temperature threshold can be set to 110°C, 130°C or 150°C as needed. When the temperature of the driving circuit increases to 110°C, the current flowing through the LEDs decreases from the preset value.

[0028] In Figure 3 In the illustrated embodiment, when the input voltage Vin increases, the feedback voltage Vfb also increases, which in turn causes the output voltage Vout to increase, forming a voltage feed-forward mechanism. And because the driving circuit has a thermal derating function, the increased part of the input voltage Vin will be simultaneously distributed to the voltage conversion circuit and the driving chip, thereby achieving power consumption balance between the voltage conversion circuit and the driving chip. At the same time, the voltage conversion circuit uses a single or multiple transistors instead of a buck bucking circuit, greatly reducing the cost of the voltage conversion circuit.

[0029] In some embodiments, the voltage regulation value of the voltage regulating diode ZD1 is 7.5V. The capacitance of the first capacitor C1 is 100 nF, and the rated voltage is 50V. The resistance value of the fourth resistor R4 is 39 KΩ, the resistance value of the fifth resistor R5 is 3.9 KΩ, and the resistance value of the sixth resistor R6 is 100 KΩ.

[0030] In this application, when the input voltage Vin increases, the voltages across the voltage conversion circuit and the driving chip increase simultaneously, that is, the increased power consumption caused by the increase in Vin is simultaneously distributed to the voltage conversion circuit and the driving chip, thereby achieving power consumption balance between the voltage conversion circuit and the driving chip, avoiding the burning of transistors in the voltage conversion circuit, and at the same time, the change of the output voltage Vout within a certain range also ensures the relatively stable working voltage of the driving chip and the load connected to the output terminal OUT, and it is not easy to damage the driving chip and the load.

[0031] The LED driving system provided by this application can, without using a Buck circuit, convert the input voltage Vin through the voltage conversion circuit provided by this application to obtain a stable output voltage for driving the subsequent-stage chip and the load, saving the system cost to the greatest extent while ensuring the normal operation of the LED driving system and improving the reliability of the system.

[0032] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A voltage conversion circuit, comprising: An input terminal, receiving an input voltage; An output terminal, providing an output voltage; A feedback circuit has an input terminal, a voltage stabilizing diode and an output terminal, wherein the input terminal receives an input voltage, the output terminal provides a feedback signal, and the feedback circuit generates a feedback signal according to the input voltage, wherein Vfb=k1×Vin+a, wherein Vfb is the value of the feedback signal, Vin is the input voltage, k1 is a constant less than 1, and a is the voltage stabilizing value of the voltage stabilizing diode; as well as A first transistor having a first terminal, a second terminal and a control terminal, wherein the first terminal receives an input voltage, the control terminal receives a feedback signal, and the first transistor converts the input voltage into an output voltage under the control of the feedback signal; When the input voltage increases, the output voltage increases, and the increase in the output voltage is smaller than the increase in the input voltage.

2. The voltage conversion circuit according to claim 1, further comprising: A second transistor having a first terminal, a second terminal and a control terminal, wherein the first terminal receives an input voltage, and the control terminal receives a feedback signal; A first resistor is coupled between the second terminal of the first transistor and the output terminal; as well as The second resistor is coupled between the second end of the second transistor and the output end, wherein the number of the second transistor is one or more.

3. The voltage conversion circuit according to claim 1, wherein the feedback circuit comprises: a fourth resistor having a first end and a second end, wherein the first end is coupled to the input end; a fifth resistor having a first end and a second end, wherein the first end is coupled to the second end of the fourth resistor, and the second end is coupled to a reference ground; The sixth resistor has a first end and a second end, wherein the first end is coupled to the input end; wherein the positive end of the voltage-stabilizing diode is coupled to the second end of the fourth resistor, and the negative end is coupled to the second end of the sixth resistor and outputs a feedback signal. 4 . The voltage conversion circuit according to claim 3 , wherein a value of the feedback signal is determined according to resistance values ​​of the fourth resistor and the fifth resistor.

5. The voltage conversion circuit according to claim 1, wherein the voltage value of the input voltage is 9-16V. The voltage conversion circuit according to claim 1 , wherein the first transistor is an N-type field effect transistor.

7. An LED driving system, comprising: The voltage conversion circuit according to any one of claims 1 to 6; A driving circuit having a power supply terminal and N LED driving terminals, wherein the power supply terminal receives an output voltage provided by the voltage conversion circuit, wherein N is a positive integer; and A single or multiple LEDs are coupled between each LED driving terminal and the output terminal of the voltage conversion circuit; The current flowing through the LED is controlled by the drive circuit. 8 . The LED driving system according to claim 7 , wherein when the temperature of the driving circuit increases to a high temperature threshold, the current flowing through the LED decreases. 9 . The LED driving system according to claim 8 , wherein the high temperature threshold is programmable.

10. The LED driving system according to claim 7, wherein a current flowing through the LED is a preset value.

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