LED projector power supply circuit

Abstract

The invention provides a power supply circuit of an LED projector. The power supply circuit comprises a first peripheral circuit, a second peripheral circuit, an isolation transformer and a control circuit, the first end of the control circuit is connected with the first end of the first peripheral circuit, the second end of the control circuit is connected with the first end of the second peripheral circuit, the third end of the control circuit is connected with the LED, the second end of the first peripheral circuit is connected with the second end of the second peripheral circuit through the isolation transformer, and the third end of the second peripheral circuit is connected with the LED; the control circuit is used for outputting a constant-voltage power supply and a constant-current power supply to the first peripheral circuit and the second peripheral circuit. Compared with the prior art, the power supply has the advantages that the topology is simple, the cost is low, the decisive advantage on equipment miniaturization is achieved, the volt-ampere characteristic of an LED light source and the voltage coupling characteristic of a transformer winding are utilized, constant voltage and constant current output can be achieved only through one control chip, and the production cost is reduced by simplifying the power supply topology structure.

Description

Technical Field

[0001] The invention is applicable to the technical field of LEDs, and in particular relates to a power supply circuit for an LED projector. Background Art

[0002] With the continuous advancement of projection technology, LED light sources are increasingly used in projectors. LED projectors have become an important development direction for projection equipment due to their advantages such as long light source life, small size, and no warm-up time. In LED projectors, the built-in power supply drives the LED light source and the power board for the control board and peripheral devices plays a vital role.

[0003] In the existing LED projector power supply circuit, taking the two-way output LED projector power supply as an example, the LED built-in power supply mostly uses two discrete power supply structures, one independently controlled constant current power supply drives the LED light source, and the other independently controlled constant voltage power supply powers the control board and peripheral devices. Because it is a multi-way output, an external control circuit is required to achieve low standby power consumption, there is a cross-regulation rate problem, and the constant voltage output voltage regulation accuracy is not high.

[0004] Therefore, a new LED projector power supply circuit is urgently needed to solve the above technical problems. Summary of the invention

[0005] The invention proposes a power supply circuit for an LED projector, aiming to simplify the power supply topology structure and reduce the production cost.

[0006] The present invention proposes a power supply circuit for an LED projector, comprising a first peripheral circuit, a second peripheral circuit, an isolation transformer and a control circuit; the first end of the control circuit is connected to the first end of the first peripheral circuit, the second end of the control circuit is connected to the first end of the second peripheral circuit, the third end of the control circuit is connected to an LED, the second end of the first peripheral circuit and the second end of the second peripheral circuit are connected through the isolation transformer, and the third end of the second peripheral circuit is connected to the LED; the control circuit is used to output a constant voltage power supply and a constant current power supply to the first peripheral circuit and the second peripheral circuit;

[0007] The control circuit includes an amplifier chip, an output voltage sampling circuit, a voltage loop compensation circuit, a current loop compensation circuit, a current-voltage loop isolation feedback circuit, and a current-voltage regulation circuit;

[0008] The first end of the amplifier chip is connected to the first end of the output voltage sampling circuit, the second end of the output voltage sampling circuit is connected to the first end of the voltage loop compensation circuit, the third end of the output voltage sampling circuit serves as the third end of the control circuit, the second end of the amplifier chip is grounded, the third end of the amplifier chip is respectively connected to the first end of the current loop compensation circuit, the second end of the voltage loop compensation circuit and the first end of the current-voltage loop isolation feedback circuit, the fourth end of the amplifier chip is grounded, the fifth end of the amplifier chip is connected to the first end of the current-voltage regulation circuit, the sixth end of the amplifier chip is connected to the second end of the current-voltage regulation circuit, the second end of the current loop compensation circuit is connected to the third end of the current-voltage regulation circuit, the fourth end of the current-voltage regulation circuit serves as the second end of the control circuit, and the second end of the current-voltage loop isolation feedback circuit serves as the first end of the control circuit.

[0009] Preferably, the current-voltage loop isolation feedback circuit includes a current-voltage loop isolation feedback chip, a first capacitor, a first resistor and a second resistor, the first end of the first resistor and the first end of the second resistor are connected to each other and to the power supply voltage, the second end of the first resistor is connected to the first end of the current-voltage loop isolation feedback chip, the second end of the current-voltage loop isolation feedback chip is connected to the second end of the second resistor, the second end of the current-voltage loop isolation feedback chip serves as the first end of the current-voltage loop isolation feedback circuit, the third end of the current-voltage loop isolation feedback chip is grounded, the fourth end of the current-voltage loop isolation feedback chip serves as the second end of the current-voltage loop isolation feedback circuit, the first end of the first capacitor is connected to the fourth end of the current-voltage loop isolation feedback chip, and the second end of the first capacitor is connected to the third end of the current-voltage loop isolation feedback chip.

[0010] Preferably, the output voltage sampling circuit includes a third resistor, a fourth resistor and a fifth resistor, the first end of the third resistor is connected to the power supply voltage, the second end of the third resistor serves as the second end of the output voltage sampling circuit, the first end of the fourth resistor serves as the third end of the output voltage sampling circuit, the second end of the fourth resistor is connected to the second end of the third resistor, the second end of the fourth resistor serves as the first end of the output voltage sampling circuit, the first end of the fifth resistor is connected to the second end of the third resistor, and the second end of the fifth resistor is grounded.

[0011] Preferably, the voltage loop compensation circuit includes a sixth resistor and a second capacitor, the first end of the sixth resistor serves as the first end of the voltage loop compensation circuit, the second end of the sixth resistor is connected to the first end of the second capacitor, and the second end of the second capacitor serves as the second end of the voltage loop compensation circuit.

[0012] Preferably, the current loop compensation circuit includes a third capacitor and a seventh resistor, the first end of the third capacitor serves as the first end of the current loop compensation circuit, the second end of the third capacitor is connected to the first end of the seventh resistor, and the second end of the seventh resistor serves as the second end of the current loop compensation circuit.

[0013] Preferably, the current and voltage regulating circuit includes a fourth capacitor, an eighth resistor, a ninth resistor and a tenth resistor, the first end of the eighth resistor is connected to the power supply voltage, the second end of the eighth resistor is connected to the first end of the fourth capacitor, the first end of the fourth capacitor serves as the second end of the current and voltage regulating circuit, the second end of the fourth capacitor is grounded, the first end of the ninth resistor serves as the first end of the current and voltage regulating circuit, the second end of the ninth resistor serves as the fourth end of the current and voltage regulating circuit, the first end of the tenth resistor serves as the third end of the current and voltage regulating circuit, and the second end of the tenth resistor is connected to the second end of the eighth resistor.

[0014] Preferably, the second peripheral circuit further includes an eleventh resistor, and the eleventh resistor is used for sampling current.

[0015] Preferably, the output turns ratio of the isolation transformer is 6:4.

[0016] Compared with the prior art, the present invention is suitable for multiple outputs, one of which is a constant current output and the other is a constant voltage output, and the constant voltage accuracy requirement is not high. The present invention has a simple topology and low cost, and has a decisive advantage in miniaturization of equipment. The present invention utilizes the volt-ampere characteristics of the LED light source and the voltage coupling characteristics of the transformer winding, and only one control chip is needed to achieve constant voltage and constant current output, and the production cost is reduced by simplifying the power supply topology. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be described in detail below in conjunction with the accompanying drawings. The above and other aspects of the present invention will become clearer and easier to understand through the detailed description made in conjunction with the following drawings. In the accompanying drawings:

[0018] Figure 1 is a schematic diagram of the structure of a control circuit provided by an embodiment of the present invention;

[0019] Figure 2 It is a schematic diagram of the structure of a first peripheral circuit and a second peripheral circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of 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 intended to limit the present invention.

[0021] Please refer to Figure 1-Figure 2 The present invention proposes a power supply circuit for an LED projector, comprising a control circuit 1, a first peripheral circuit 2, a second peripheral circuit 3 and an isolation transformer T1; the first end of the control circuit 1 is connected to the first end of the first peripheral circuit 2, the second end of the control circuit 1 is connected to the first end of the second peripheral circuit 3, the third end of the control circuit 1 is connected to an LED, the second end of the first peripheral circuit 2 and the second end of the second peripheral circuit 3 are connected through the isolation transformer T1, and the third end of the second peripheral circuit 3 is connected to an LED; the control circuit 1 is used to output a constant voltage power supply and a constant current power supply to the first peripheral circuit 2 and the second peripheral circuit 3;

[0022] The control circuit 1 includes an amplifier chip U2, an output voltage sampling circuit 12, a voltage loop compensation circuit 13, a current loop compensation circuit 14, a current-voltage loop isolation feedback circuit 11 and a current-voltage regulation circuit 15;

[0023] The first end (VCTRL) of the amplifier chip U2 is connected to the first end of the output voltage sampling circuit 12, the second end of the output voltage sampling circuit 12 is connected to the first end of the voltage loop compensation circuit 13, the third end of the output voltage sampling circuit 12 serves as the third end of the control circuit 1, the second end (GND) of the amplifier chip U2 is grounded, the third end (VOUT) of the amplifier chip U2 is respectively connected to the first end of the current loop compensation circuit 14, the second end of the voltage loop compensation circuit 13 and the first end of the current-voltage loop isolation feedback circuit 11, the fourth end (ICTRL) of the amplifier chip U2 is grounded, the fifth end (VSEN) of the amplifier chip U2 is connected to the first end of the current-voltage regulation circuit 15, the sixth end (VCC) of the amplifier chip U2 is connected to the second end of the current-voltage regulation circuit 15, the second end of the current loop compensation circuit 14 is connected to the third end of the current-voltage regulation circuit 15, the fourth end of the current-voltage regulation circuit 15 serves as the second end of the control circuit 1, and the second end of the current-voltage loop isolation feedback circuit 11 serves as the first end of the control circuit 1.

[0024] In an embodiment of the present invention, the current-voltage loop isolation feedback circuit 11 includes a current-voltage loop isolation feedback chip U3, a first capacitor C1, a first resistor R1 and a second resistor R2, the first end of the first resistor R1 and the first end of the second resistor R2 are interconnected and connected to the power supply voltage, the second end of the first resistor R1 is connected to the first end of the current-voltage loop isolation feedback chip U3, the second end of the current-voltage loop isolation feedback chip U3 is connected to the second end of the second resistor R2, the second end of the current-voltage loop isolation feedback chip U3 serves as the first end of the current-voltage loop isolation feedback circuit 11, the third end of the current-voltage loop isolation feedback chip U3 is grounded, the fourth end of the current-voltage loop isolation feedback chip U3 serves as the second end of the current-voltage loop isolation feedback circuit 11, the first end of the first capacitor C1 is connected to the fourth end of the current-voltage loop isolation feedback chip U3, and the second end of the first capacitor C1 is connected to the third end of the current-voltage loop isolation feedback chip U3.

[0025] In the embodiment of the present invention, the output voltage sampling circuit 12 includes a third resistor R3, a fourth resistor R4 and a fifth resistor R5, the first end of the third resistor R3 is connected to the power supply voltage, the second end of the third resistor R3 serves as the second end of the output voltage sampling circuit 12, the first end of the fourth resistor R4 serves as the third end of the output voltage sampling circuit 12, the second end of the fourth resistor R4 is connected to the second end of the third resistor R3, the second end of the fourth resistor R4 serves as the first end of the output voltage sampling circuit 12, the first end of the fifth resistor R5 is connected to the second end of the third resistor R3, and the second end of the fifth resistor R5 is grounded.

[0026] In an embodiment of the present invention, the voltage loop compensation circuit 13 includes a sixth resistor R6 and a second capacitor C2, the first end of the sixth resistor R6 serves as the first end of the voltage loop compensation circuit 13, the second end of the sixth resistor R6 is connected to the first end of the second capacitor C2, and the second end of the second capacitor C2 serves as the second end of the voltage loop compensation circuit 13.

[0027] In an embodiment of the present invention, the current loop compensation circuit 14 includes a third capacitor C3 and a seventh resistor R7, the first end of the third capacitor C3 serves as the first end of the current loop compensation circuit 14, the second end of the third capacitor C3 is connected to the first end of the seventh resistor R7, and the second end of the seventh resistor R7 serves as the second end of the current loop compensation circuit 14.

[0028] In the embodiment of the present invention, the current and voltage regulating circuit 15 includes a fourth capacitor C4, an eighth resistor R8, a ninth resistor R9 and a tenth resistor R10, the first end of the eighth resistor R8 is connected to the power supply voltage, the second end of the eighth resistor R8 is connected to the first end of the fourth capacitor C4, the first end of the fourth capacitor C4 serves as the second end of the current and voltage regulating circuit 15, the second end of the fourth capacitor C4 is grounded, the first end of the ninth resistor R9 serves as the first end of the current and voltage regulating circuit 15, the second end of the ninth resistor R9 serves as the fourth end of the current and voltage regulating circuit 15, the first end of the tenth resistor R10 serves as the third end of the current and voltage regulating circuit 15, and the second end of the tenth resistor R10 is connected to the second end of the eighth resistor R8. The ninth resistor R9 is used to sample the LED current.

[0029] In the embodiment of the present invention, the second peripheral circuit 3 further includes an eleventh resistor R11 , and the eleventh resistor R11 is used to sample the current.

[0030] In the embodiment of the present invention, the output turns ratio of the isolation transformer T1 is 6:4.

[0031] Specifically, a projector generally has two states, namely, a power-on standby state and a power-on projection working state; when the projector is connected to a power source, the projector is in a standby working state, at which time the LED is not working, and the amplifier chip U2 works in a constant voltage loop state, with the current loop open, and at this time the two outputs are stable; when the projector is turned on, the LED light source is lit, and at this time the amplifier chip U2 works in a constant current loop, with the voltage loop open, and the LED volt-ampere characteristic shows that the LED works under a constant current, so the LED voltage can be regarded as fixed (without considering device errors and temperature characteristics), which is equivalent to the LED output being a fixed voltage. Combined with the transformer winding voltage coupling characteristic (the winding voltage is proportional to the number of winding turns), if you want to get another stable voltage, you only need to adjust the transformer winding ratio in proportion; with Figure 2 For example, the built-in power supply has two outputs, the LED drive constant current is 2.8A, and the control board power supply constant voltage is 12V. The measured LED light source voltage is 17.5V when the LED light source is 2.8A. The transformer output turns ratio is designed to be 17.5 / 12, which is approximately equal to 6 / 4. The actual design LED winding number of turns is 6, and the 12V winding number of turns is 4.

[0032] Compared with the prior art, the present invention is suitable for multiple outputs, one of which is a constant current output and the other is a constant voltage output, and the constant voltage accuracy requirement is not high. The present invention has a simple topology and low cost, and has a decisive advantage in miniaturization of equipment. The present invention utilizes the volt-ampere characteristics of the LED light source and the voltage coupling characteristics of the transformer winding, and only one control chip is needed to achieve constant voltage and constant current output, and the production cost is reduced by simplifying the power supply topology.

[0033] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0034] The embodiments of the present invention are described above in conjunction with the accompanying drawings. What is disclosed is only the preferred embodiment of the present invention. However, the present invention is not limited to the above-mentioned specific implementation manner. The above-mentioned specific implementation manner is only illustrative rather than restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms and equivalent changes without departing from the scope of protection of the purpose of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A power supply circuit for an LED projector, characterized in that: It comprises a first peripheral circuit, a second peripheral circuit, an isolation transformer and a control circuit; the first end of the control circuit is connected to the first end of the first peripheral circuit, the second end of the control circuit is connected to the first end of the second peripheral circuit, the third end of the control circuit is connected to an LED, the second end of the first peripheral circuit and the second end of the second peripheral circuit are connected through the isolation transformer, and the third end of the second peripheral circuit is connected to an LED; the control circuit is used to output a constant voltage power supply and a constant current power supply to the first peripheral circuit and the second peripheral circuit; The control circuit includes an amplifier chip, an output voltage sampling circuit, a voltage loop compensation circuit, a current loop compensation circuit, a current-voltage loop isolation feedback circuit, and a current-voltage regulation circuit; The first end of the amplifier chip is connected to the first end of the output voltage sampling circuit, the second end of the output voltage sampling circuit is connected to the first end of the voltage loop compensation circuit, the third end of the output voltage sampling circuit serves as the third end of the control circuit, the second end of the amplifier chip is grounded, the third end of the amplifier chip is respectively connected to the first end of the current loop compensation circuit, the second end of the voltage loop compensation circuit and the first end of the current-voltage loop isolation feedback circuit, the fourth end of the amplifier chip is grounded, the fifth end of the amplifier chip is connected to the first end of the current-voltage regulation circuit, the sixth end of the amplifier chip is connected to the second end of the current-voltage regulation circuit, the second end of the current loop compensation circuit is connected to the third end of the current-voltage regulation circuit, the fourth end of the current-voltage regulation circuit serves as the second end of the control circuit, and the second end of the current-voltage loop isolation feedback circuit serves as the first end of the control circuit.

2. The LED projector power supply circuit as claimed in claim 1, characterized in that: The current-voltage loop isolation feedback circuit includes a current-voltage loop isolation feedback chip, a first capacitor, a first resistor and a second resistor. The first end of the first resistor and the first end of the second resistor are connected to each other and to a power supply voltage. The second end of the first resistor is connected to the first end of the current-voltage loop isolation feedback chip, and the second end of the current-voltage loop isolation feedback chip is connected to the second end of the second resistor. The second end of the current-voltage loop isolation feedback chip serves as the first end of the current-voltage loop isolation feedback circuit. The third end of the current-voltage loop isolation feedback chip is grounded. The fourth end of the current-voltage loop isolation feedback chip serves as the second end of the current-voltage loop isolation feedback circuit. The first end of the first capacitor is connected to the fourth end of the current-voltage loop isolation feedback chip, and the second end of the first capacitor is connected to the third end of the current-voltage loop isolation feedback chip.

3. The LED projector power supply circuit as claimed in claim 1, characterized in that: The output voltage sampling circuit includes a third resistor, a fourth resistor and a fifth resistor, the first end of the third resistor is connected to the power supply voltage, the second end of the third resistor serves as the second end of the output voltage sampling circuit, the first end of the fourth resistor serves as the third end of the output voltage sampling circuit, the second end of the fourth resistor is connected to the second end of the third resistor, the second end of the fourth resistor serves as the first end of the output voltage sampling circuit, the first end of the fifth resistor is connected to the second end of the third resistor, and the second end of the fifth resistor is grounded.

4. The LED projector power supply circuit as claimed in claim 1, characterized in that: The voltage loop compensation circuit includes a sixth resistor and a second capacitor, the first end of the sixth resistor serves as the first end of the voltage loop compensation circuit, the second end of the sixth resistor is connected to the first end of the second capacitor, and the second end of the second capacitor serves as the second end of the voltage loop compensation circuit.

5. The LED projector power supply circuit as claimed in claim 1, characterized in that: The current loop compensation circuit includes a third capacitor and a seventh resistor, the first end of the third capacitor serves as the first end of the current loop compensation circuit, the second end of the third capacitor is connected to the first end of the seventh resistor, and the second end of the seventh resistor serves as the second end of the current loop compensation circuit.

6. The LED projector power supply circuit as claimed in claim 1, characterized in that: The current and voltage regulating circuit includes a fourth capacitor, an eighth resistor, a ninth resistor and a tenth resistor. The first end of the eighth resistor is connected to the power supply voltage, the second end of the eighth resistor is connected to the first end of the fourth capacitor, the first end of the fourth capacitor serves as the second end of the current and voltage regulating circuit, the second end of the fourth capacitor is grounded, the first end of the ninth resistor serves as the first end of the current and voltage regulating circuit, the second end of the ninth resistor serves as the fourth end of the current and voltage regulating circuit, the first end of the tenth resistor serves as the third end of the current and voltage regulating circuit, and the second end of the tenth resistor is connected to the second end of the eighth resistor.

7. The LED projector power supply circuit as claimed in claim 1, characterized in that: The second peripheral circuit further includes an eleventh resistor, and the eleventh resistor is used for sampling current.

8. The LED projector power supply circuit as claimed in claim 1, characterized in that: The output turns ratio of the isolation transformer is 6:4.

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