Projection device and photo coupler circuit for the same

A projection device and a photo coupler circuit for the same are disclosed. The photo coupler circuit includes a logic unit, a number of integration units and a selection unit. The logic unit is configured to receive a number of first control signals and a number of first PWM signals from a main circuit of the projection device, and to output a number of second PWM signals and one or more second control signals according to the first control signals and the first PWM signals. The integration units are coupled to the logic unit. Each of the integration units is configured to generate an integration signal according to one of the second PWM signals. The selection unit is coupled to the integration units to select one of the integration signals to be output to a light source drive circuit of the projection device according to the second control signals.

This application claims the benefit of People's Republic of China application Serial No. 201910527287.6, filed Jun. 18, 2019, the subject matter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates in general to a projection device and a photo coupler circuit for the same.

Description of the Related Art

In the presentation or the speech, projector is commonly used to share the screen of a person computer through the projection of image on a large screen. Photo coupler circuit is a component essential to existing projector. The size and the manufacturing cost of the drive circuit board will be reduced if the photo coupler circuit can be improved.

SUMMARY OF THE INVENTION

According to one embodiment of the present invention, a photo coupler circuit adapted to a projection device is disclosed. The photo coupler circuit includes a logic unit, a number of integration units and a selection unit. The logic unit is configured to receive a number of first control signals and a number of first pulse width modulation (PWM) signals from a main circuit of the projection device, and to output a number of second PWM signals and one or more second control signals according to the first control signals and the first PWM signals. The integration units are coupled to the logic unit. Each of the integration units is configured to generate an integration signal according to one of the second PWM signals. The selection unit is coupled to the integration units and is configured to select one of the integration signals to be output to a light source drive circuit of the projection device according to the one or more second control signals.

According to another embodiment of the present invention, a projection device is provided. The projection device includes a main circuit, a photo coupler circuit and a light source drive circuit. The photo coupler circuit includes a logic unit, a number of integration units and a selection unit. The logic unit is configured to receive a number of first control signals and a number of first PWM signals from the main circuit, and to output a number of second PWM signals and one or more second control signals according to the first control signals and the first PWM signals. The integration units are coupled to the logic unit. Each of the integration units is configured to generate an integration signal according to one of the second PWM signals. The selection unit is coupled to the integration units, and is configured to select one of the integration signals to be output according to the second control signals. The light source drive circuit is coupled to the photo coupler circuit and is configured to receive the integration signal output from the photo coupler circuit.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIG. 1, a schematic diagram of a projection device according to an embodiment of the present invention is shown. The projection device10includes a main circuit102, a photo coupler circuit104and a light source drive circuit106. The main circuit102is configured to generate a number of first control signals and a number of first pulse width modulation (PWM) signals. The first control signals include a red enable signal R_enable, a green enable signal G_enable and a blue enable signal B_enable. The first PWM signals include a red PWM signal R_PWM, a green PWM signal G_PWM, a blue PWM signal B_PWM and a yellow PWM signal Y_PWM.

The waveforms of the red enable signal R_enable, the green enable signal G_enable, the blue enable signal B_enable, the red PWM signal R_PWM, the green PWM signal G_PWM, the blue PWM signal B_PWM and the yellow PWM signal Y_PWM are illustrated inFIG. 2.

The photo coupler circuit104is coupled to the main circuit102. The photo coupler circuit104includes a logic unit1041, a number of integration units1043A and1043B and a selection unit1045.

The logic unit1041receives the first PWM signals (the red PWM signal R_PWM, the green PWM signal G_PWM, the blue PWM signal B_PWM and the yellow PWM signal Y_PWM) and the first control signals (the red enable signal R_enable, the green enable signal G_enable and the blue enable signal B_enable) from the main circuit102, and generates a number of second PWM signals PWM1and PWM2and a second control signal SW according to the first PWM signals and the first control signals. In an embodiment, the second PWM signal PWM1is generated according to the following formula: PWM1=G_enable*G_PWM+Inv(G_enable)*R_PWM; the second PWM signal PWM2is generated according to the following formula: PWM2=R_enable*Y_PWM+Inv(R_enable)*B_PWM; and the first control signal SW is generated according to the following formula: SW=R_enable*G_enable+B_enable, wherein * represents logic “AND” operation; + represents logic “OR” operation; and Inv represents logic “INVERSE” operation. The logic unit1041may include a number of logic gates formed of a number of transistors to implement the above formulas.

The integration units1043A and1043B are coupled to the logic unit1041. The integration units1043A is configured to generate an integration signal Int_PWM1according to the second PWM signal PWM1. The integration units1043B is configured to generate an integration signal Int_PWM2according to the second PWM signal PWM2. In an embodiment, the integration units1043A and1043B respectively include a capacitor configured to integrate the received second PWM signals.

The selection unit1045is coupled to the integration units1043A and1043B. The selection unit1045selects one of the integration signals Int_PWM1and Int_PWM2to be output according to the second control signal SW.

The light source drive circuit106is coupled to the photo coupling unit104. The light source drive circuit106drives a light source according to one of the integration signals Int_PWM1and Int_PWM2output from the selection unit1045.

In an embodiment, the photo coupler circuit104further includes a number of first photo coupling units (not illustrated) and a second photo coupling unit (not illustrated). Each of the first photo coupling units is coupled between each of the integration units and the logic unit to transmit each of the second PWM signals in the form of light. The second photo coupling unit is coupled between the selection unit and the logic unit to transmit the second control signals in the form of light.

Principles of the present invention are disclosed below with accompanying drawingFIG. 2. During time T1, the red enable signal R_enable represents logic high (referred as high hereinafter); the green enable signal G_enable and the blue enable signal B_enable represent logic low (referred as low hereinafter); the second PWM signal PWM1represents the red PWM signal R_PWM; the integration units1043A performs integration on the red PWM signal R_PWM to generate the integration signal Int_PWM1; the second PWM signal PWM2represents the yellow PWM signal Y_PWM; the integration units1043B performs integration on the yellow PWM signal Y_PWM to generate the integration signal Int_PWM2; the second control signal SW is at low level; the selection unit1045selects the integration signal Int_PWM1to be output to the light source drive circuit106; and the light source drive circuit106drives the element of the light source (such as red LED) to generate a red beam corresponding to the brightness of the current intensity represented by the integration signal Int_PWM1according to the integration signal Int_PWM1. Meanwhile, during time T2, the integration signal Int_PWM2is integrated by the integration units1043B. During time T2, the red enable signal R_enable and the green enable signal G_enable are at high level; the blue enable signal B_enable is at low level; the second PWM signal PWM1represents the green PWM signal G_PWM; the integration units1043A performs integration on the green PWM signal G_PWM to generate the integration signal Int_PWM1; the second PWM signal PWM2represents the yellow PWM signal Y_PWM; the integration units1043B performs integration on the yellow PWM signal Y_PWM to generate the integration signal Int_PWM2; the second control signal SW is at high level; the selection unit1045selects the integration signal Int_PWM2to be output to the light source drive circuit106; and the light source drive circuit106drives the element of the light source (such as red LED and green LED) to generate a yellow beam corresponding to the brightness of the current intensity represented by the integration signal Int_PWM2according to the integration signal Int_PWM2. Meanwhile, during time T3, the integration signal Int_PWM1is integrated by the integration units1043A. During time T3, the green enable signal G_enable is at high level; the red enable signal R_enable and the blue enable signal B_enable is at low level; the second PWM signal PWM1represents the green PWM signal G_PWM; the integration units1043A performs integration on the green PWM signal G_PWM to generate the integration signal Int_PWM1; the second PWM signal PWM2represents the blue PWM signal B_PWM; the integration units1043B performs integration on the blue PWM signal B_PWM to generate the integration signal Int_PWM2; the second control signal SW is at low level; the selection unit1045selects the integration signal Int_PWM1to be output to the light source drive circuit106; and the light source drive circuit106drives the element of the light source (such as green LED) to generate a green beam corresponding to the brightness of the current intensity represented by the integration signal Int_PWM1according to the integration signal Int_PWM1. Meanwhile, during time T4, the integration signal Int_PWM2is integrated by the integration units1043B. During time T4, the blue enable signal B_enable is at high level; the red enable signal R_enable and the green enable signal G_enable is at low level; the second PWM signal PWM1represents the red PWM signal R_PWM; the integration units1043A performs integration on the red PWM signal R_PWM to generate the integration signal Int_PWM1; the second PWM signal PWM2represents the blue PWM signal B_PWM; the integration units1043B performs integration on the blue PWM signal B_PWM to generate the integration signal Int_PWM2; the second control signal SW is at high level; the selection unit1045selects the integration signal Int_PWM2to be output to the light source drive circuit106; and the light source drive circuit106drives the element of the light source (such as blue LED) to generate a blue beam corresponding to the brightness of the current intensity represented by the integration signal Int_PWM2according to the integration signal Int_PWM2. Meanwhile, during next time, the integration signal Int_PWM1is integrated by the integration units1043A.

For the invention to be better understood, the above disclosure is illustrated in Table 1, wherein “0” represents logic low, and “1” represents logic high.

Referring toFIG. 3, a schematic diagram of a projection device according to another embodiment of the present invention is shown. The projection device30includes a lens301, a low voltage block303and a high voltage block305. The low voltage block303includes a logic unit3031, a main circuit3033and an imaging unit3035, wherein the logic unit3031can be the said logic unit1041, and the main circuit3033can be the said main circuit102. The high voltage unit305includes a voltage conversion unit3051, a number of integration units3053A and3053B, a selection unit3055, a light source drive circuit3057and a light source3059, wherein the integration units3053A and3053B respectively can be the said integration units1043A and1043B; the selection unit3055can be the said selection unit1045; and the light source drive circuit3057can be the said light source drive circuit106. The voltage conversion unit3051is configured to receive a source current to generate a first voltage V1and a second voltage V2, wherein the first voltage V1is higher than the second voltage V2. The first voltage V1will be provided to the high voltage block305, and the second voltage V2will be provided to the low voltage block303. The light source3059may include a number of light emitting diodes (LEDs) configured to generate the red, the green, the blue and the yellow beams. The light source3059is driven by the light source drive circuit3057to generate a beam to the imaging unit3035, which accordingly generates an image output via the lens301. The projection device30further includes a number of first photo coupling units307A and307B and a second photo coupling unit309. The first photo coupling units307A and307B are coupled between the logic unit3031and the integration units3053A and3053B to transmit the second PWM signals PWM1and PWM2in the form of light. The second photo coupling unit309is coupled between the logic unit3031and the selection unit3055to transmit the second control signal SW in the form of light.

The drive voltage for the low voltage block303is different from that for the high voltage block305. Due to the considerations of interaction avoidance and safety enhancement, the low voltage block303and the high voltage block305are electrically isolated from each other (except for the drive voltage provided by the voltage conversion unit). The PWM signals and the control signals of each color are transmitted to the high voltage block305from the low voltage block303by the photo coupling unit in the form of light. In the present embodiment, the logic unit3031simplifies the first control signals and the first PWM signals, which are 7 signals in total, to the second PWM signals and the second control signal, which are 3 signals in total, and the quantity of the photo coupling unit connected between the low voltage block303and the high voltage block305will decrease accordingly (from7to3), not only reducing the manufacturing cost but also downsizing the entire circuit.

Referring toFIG. 4, a schematic diagram of a projection device according to an alternate embodiment of the present invention is shown. The projection device40is similar to the projection device10, and the differences are disclosed below.

The first control signals provided by the main circuit40include a red enable signal R_enable, a green enable signal G_enable and a blue enable signal B_enable; the first PWM signals include a red PWM signal R_PWM, a green PWM signal G_PWM and a blue PWM signal B_PWM; the waveform of each signal can be obtained with reference toFIG. 5. The logic unit4041generates 3 second PWM signals PWM3, PWM4, and PWM5and 3 selection signals SW according to the first control signals and the first PWM signals. The integration units4043A,4043B, and4043C generate the integration signals Int_PWM3, Int_PWM4, and Int_PWM5according to the second PWM signals PWM3, PWM4, and PWM5, respectively. The selection unit4045selects one of the integration signal Int_PWM3, Int_PWM4, and Int_PWM5to be output to the light source drive circuit406according to the second control signals SW1and SW2. In the present example, the projection device40may include 3 first photo coupling units connected between the logic unit4041and the integration units4043A,4043B, and4043C, and 2 second photo coupling units connected between the logic unit4041and the selection unit4045.

Besides, the second PWM signals PWM3can be generated according to the following formula: PWM3=(B_enable+R_enable)*R_PWM; the second PWM signals PWM4can be generated according to the following formula: PWM4=(R_enable+G_enable)*G_PWM; the second PWM signals PWM3can be generated according to the following formula: PWM5=(G_enable+B_enable)*B_PWM; the second control signal SW1can be generated according to the following formula: SW1=R_enable; and the second control signal SW2can be generated according to the following formula: SW2=G_enable, wherein * represents logic “AND” operation, and + represents logic “OR” operation. The selection unit4045selects one of the integration signal Int_PWM3, Int_PWM4, Int_PWM5to be output to the light source drive circuit406according to the table illustrated below.