# Patent

## Title
Pulse width modulation circuit and pulse width modulation signal generating method having two refresh rates

## Abstract

A PWM circuit that can have two refresh rates, including: a first PWM signal generator and a second PWM signal generator; wherein the first PWM signal generator and the second PWM signal generator respectively control refresh rates in two dimensions of an output data generated from a target apparatus. A PWM signal generation method that can have two refresh rates, including: generating a first PWM signal; generating a second PWM signal; and controlling refresh rates in different dimensions of an output data generated from a target apparatus respectively by using the first PWM signal and the second PWM signal.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The disclosed embodiments of the present invention relate to a pulse width modulation (PWM) circuit and a PWM signal generation method, and more particularly, to a PWM circuit and a PWM signal generation method that can have two refresh rates.
2. Description of the Prior Art
In electronic apparatuses, a pulse width modulation (PWM) signal is usually utilized as a control signal. For example, the duty cycle of a PWM signal might be adjusted to control the brightness of video frames or the charging/discharging of a voltage conversion circuit.
FIG. 1 is a diagram illustrating a conventional PWM signal. PWM signals with different cycles are denoted by PWMa and PWMb, respectively. As shown in FIG. 1, an example of a minimum pulse (1 ns) is illustrated, where PWMa is a PWM signal with a cycle of 256 ns, and PWMb is a PWM signal with a cycle of 512 ns. When the PWM signal is used to control the brightness of video frames, the cycle means the refresh rate. That is to say, a PWM signal with a short cycle has a higher refresh rate, and a PWM signal with a longer cycle has a lower refresh rate in contrary. In addition, a PWM signal has another important characteristic, the resolution. In the example of FIG. 1, the resolution of the PWMa is 1/256, and the resolution of the PWMb is 1/512. That is to say, PWMb could be a control signal with a precision higher than that of PWMa. However, as described above, the refresh rate of PWMb is lower than PWMa, and thus the resolution is inversely proportional to the refresh rate.
Generally speaking, only a single PWM signal of a single dimension (i.e., a single direction) is used in the current control mechanism of the PWM signal. Therefore, there would be a trade off between the resolution and the refresh rate, thus adding limitations to the circuit design.
SUMMARY OF THE INVENTION
Therefore, one objective of the present invention is to provide a PWM circuit that can have two refresh rates and a related PWM signal generation method thereof.
According to a first aspect of the present invention, a PWM circuit that can have two refresh rates is disclosed, including: a first PWM signal generator and a second PWM signal generator; wherein the first PWM signal generator and the second PWM signal generator respectively control refresh rates in different dimensions of output data from a target apparatus.
According to a second aspect of the present invention, a PWM circuit that can have two refresh rates is disclosed, wherein the PWM circuit is used by a target apparatus to generate an output data, and the output data comprises a plurality of data unit. The PWM circuit comprises: a first PWM signal generator and a second PWM signal generator; wherein the first PWM signal generator controls a first part of each of the data units, and the second PWM signal generator controls a second part of each of the data units, thus the output data can have two refresh rates.
According to a third aspect of the present invention, a PWM signal generation method that can have two refresh rates is disclosed, including: generating a first PWM signal; generating a second PWM signal; and controlling refresh rates in different dimensions of output data from a target apparatus respectively by using the first PWM signal and the second PWM signal.
According to a fourth aspect of the present invention, a PWM signal generation method that can have two refresh rates is disclosed, wherein the PWM signal generation method is used by a target apparatus to generate an output data, and the output data comprises a plurality of data unit, and the PWM signal generation method includes: generating a first PWM signal generator; generating a second PWM signal generator; and controlling a first part of each of the data units by the first PWM signal, and controlling a second part of each of the data units by using the second PWM signal, thus the output data can have two refresh rates.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating a conventional PWM signal.
FIG. 2 is a block diagram illustrating a PWM circuit according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating the frame operation of a PWM circuit according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating the frame operation of a PWM circuit according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating the frame operation of a PWM circuit according to an embodiment of the present invention.
FIG. 6 is a flowchart illustrating the operation of a PWM signal generation method according to an embodiment of the present invention.
FIG. 7 is a flowchart illustrating the operation of a PWM signal generation method according to another embodiment of the present invention.



DETAILED DESCRIPTION
Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”. Also, the term “couple” is intended to mean either an indirect or direct electrical connection. Accordingly, if one device is electrically connected to another device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.
FIG. 2 is a block diagram illustrating a PWM circuit 200 according to an embodiment of the present invention. As shown in FIG. 2, the PWM circuit 200 includes a first PWM signal generator 201 and a second PWM signal generator 203. The first PWM generator 201 and the second PWM generator 203 are used to generate the first PWM signal PWM1 and the second PWM signal PWM2 respectively to control refresh rates in different dimensions of the output data OS generated from a target apparatus 205.
In the following, the operation of the PWM circuit 200 in FIG. 2 is detailed with reference to the diagram in FIG. 3. It should be noted that an image processing device is used as the target apparatus 205 for illustrative purposes. Therefore, the output data OS includes at least a frame, and the first PWM signal generator 201 and the second PWM signal generator 203 are used to control the brightness of the frames in different dimensions, respectively. In this case, the first PWM signal generator 201 and the second PWM signal generator 203 may be regarded as a controller for controlling the brightness of a light processing device, and the light processing device accordingly generates the output data OS with different brightness settings. However, this by no means implies that the concept of the present invention is only allowed to be applied to frames or the aforementioned light processing device. Those skilled in the art should readily understand that the concept of the present invention may be applied to other electronic devices after reading the disclosed embodiments of the present invention. These alternative designs all fall within the scope of the present invention. For example, when the concept of the present invention is not applied to a frame, the frame may be replaced by a data unit.
Please refer to sub-diagram (a) of FIG. 3. As described above, the output data OS includes at least a frame (e.g., frame 1-frame 8 in this embodiment), where each frame could be divided into the first part P1 and the second part P2. In this embodiment, the first part P1 and the second part P2 represent different bits of the frame. The brightness of the first part P1 is controlled by the first PWM signal PWM1, and the brightness of the second part P2 is controlled by the second PWM signal PWM2. Please note that the first PWM signal PWM1 and the second PWM signal PWM2 control the brightness in different dimensions, respectively. As shown in the sub-diagram (a) of FIG. 3, the changing of the brightness of the first part P1 is shown on the horizontal direction (the part labeled by slashes is bright), and the changing of the brightness of the first part P2 is shown on the vertical direction (the part labeled by slashes is bright).
In this embodiment, the single cycle of the single first PWM signal PWM1 controls at least a portion of each first part P1, thus each of the first parts P1 of the frame 1 -frame 8 shows the same changing of the brightness. For instance, all of P11 included the first parts P1 of the frame 1 -frame 8 should correspond to the high level of the first PWM signal PWM1, therefore it shows the bright status. For another example, all of P12 of the first parts P1 of the frame 1 -frame 8 should correspond to the low level of the first PWM signal PWM1, therefore it shows the dark status. That is to say, the first parts P1 of the frame 1 -frame 8 would correspond to a fist cycle of the first PWM signal PWM1 and show the same brightness changes.
However, the second PWM signal PWM2 with a single cycle controls a plurality of second parts P2. For instance, some frames, including frame 1-frame 3, correspond to the high level of the second PWM signal PWM2, and the second part P2 is therefore bright; and other frames, including frame 4-frame 8, correspond to the low level of the second PWM signal PWM2, and the second part P2 is therefore dark. That is, the changes composed of the second parts P2 of the frame 1 -frame 8 correspond to a second cycle of the second PWM signal P2.
In the above-mentioned mechanism, the user would see frames like that presented in sub-diagram (b) of FIG. 3. Hence, the frames viewed by the user are still continuous frame 1 -frame 8. However, theses continuous frames are actually controlled by two distinct PWM signals instead of only one PWM signal employed in the conventional technique. Therefore, the PWM circuit 200 is allowed to have two different refresh rates under such a mechanism, which provides more flexibility in the circuit design and breaks the trade off between resolution and refresh rate encountered in the conventional design.
Please note that the above-mentioned embodiment uses two dimensions (i.e., the vertical and the horizontal directions) to illustrate the concept of the present invention. However, the definition of the directions might be changed for different memory arrangements, different data structures, or different drawing presentation manners. Thus, the concept of the present invention should be briefly summarized as using PWM signals in two different dimensions to control the same output data to make the output data normally outputted and have two different refresh rates. Any modifications based on this concept should fall within the scope of the present invention.
Please note that the second part P2 in the embodiment shown in FIG. 3 is not limited to the last few bits of each frame. Alternatively, it could be distributed in any positions co-located in all frames. Moreover, the second part P2 of each frame may meet a specific rule. For example, each of the second parts P2 in FIG. 4 are located at the neighboring position of the previous frame or the next frame. As these specific rules may be modified according to different design requirements, further details are omitted here for brevity. In addition, the position of the second part P2 may also be decided randomly, as shown in FIG. 5. This also falls within the scope of the present invention.
Regarding the embodiments in FIG. 4 and FIG. 5, the first PWM signal PWM1 and the second PWM signal PWM2 may be slightly different from that used in the embodiment of FIG. 3. For example, in the embodiment of FIG. 3, the first PWM signal PWM1 and the second PWM signal PWM2 may operate independently without interfering with each other; however, in the embodiments of FIG. 4 and FIG. 5, the timing issue of the first PWM signal PWM1 and the second PWM signal PWM2 should be considered. Taking the embodiment of FIG. 4 for example, due to that the position of the second part P2 of the frame 1 and the position of the second part P2 of the frame 2 are different, the position of the second part P2 of the frame 2 was controlled by the first PWM signal PWM1 in frame 1, but would be controlled by the second PWM signal PMW2 in frame 2.
According to the above embodiments, the WPM signal generation method as shown in FIG. 6 is obtained and includes:
Step 601: Generate a first PWM signal PWM1;
Step 603: Generate a second PWM signal PWM2; and
Step 605: Control refresh rates in different dimensions of the output data generated from a target apparatus respectively by using the first PWM signal PWM1 and the second PWM signal PWM2. Taking the embodiment of FIG. 3 for example, the first PWM signal PWM1 is used to control the refresh rate in the horizontal direction, while the second PWM signal PWM2 is used to control the refresh rate in the vertical direction.
The above-mentioned exemplary WPM signal generation method may be simplified as another WPM signal generation method shown FIG. 7, which includes:
Step 701: Generate a first PWM signal PWM1;
Step 703: Generate a second PWM signal PWM2; and
Step 705: Control a first part (P1) of each of the data units (e.g., frame 1 -frame 8 of FIG. 3) by the first PWM signal PWM1, and control a second part (P2) of each of the data units by using the second PWM signal PWM1, such that the output data can have two refresh rates.
As those skilled in this art can readily understand operations of the PWM signal generation methods of FIG. 6 and FIG. 7 after reading aforementioned embodiment of the present invention, further details are omitted here for brevity.
The above-mentioned embodiments could provide a PWM circuit and a PWM signal generation method that can have two refresh rates. With the use of the proposed mechanism, the problem of the resolution significantly limited due to the single refresh rate in the conventional design would be avoided.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

## Claims

1. A pulse width modulation (PWM) circuit that can have two refresh rates, comprising:
a first PWM signal generator; and
a second PWM signal generator;
wherein the first PWM signal generator and the second PWM signal generator respectively control refresh rates in different dimensions of output data from a target apparatus.

2. The PWM circuit that can have two refresh rates of claim 1, wherein the target apparatus is a light processing device, and the first PWM signal generator and the second PWM signal generator are arranged to control the brightness of the output data in the different dimensions respectively.

3. The PWM circuit of claim 1, wherein the output data comprises at plurality of frames, wherein the first PWM signal generator generates a first PWM signal for determining a first refresh rate for all the frames, and the second PWM signal generator generates a second PWM signal for determining a second refresh rate for all the frames.

4. A PWM circuit that can have two refresh rates, wherein the PWM circuit is used by a target apparatus to generate an output data, and the output data comprises a plurality of data units, and the PWM circuit comprises:
a first PWM signal generator; and
a second PWM signal generator;
wherein the first PWM signal generator controls a first part of each of the data units, and the second PWM signal generator controls a second part of each of the data units, thus the output data can have two refresh rates;
wherein a position of the second part of each of the data units is decided randomly.

5. The PWM circuit of claim 4, wherein the target device is a light processing device, and the first PWM signal generator and the second PWM signal generator are arranged to control the brightness of the data units respectively.

6. The PWM circuit of claim 4, wherein the first PWM signal generator generates a first PWM signal, and the second PWM signal generator generates a second PWM signal, and the first parts of the data units corresponding to a first cycle of the first PWM signal show the same changes, and the second parts of the data units corresponding to a second cycle of the second PWM signal show the same changes.

7. The PWM circuit of claim 4, wherein the data units are frames, wherein the first PWM signal generator generates a first PWM signal for determining a first refresh rate for all the frames, and the second PWM signal generator generates a second PWM signal for determining a second refresh rate for all the frames.

8. A PWM signal generation method that can have two refresh rates, comprising:
generating a first PWM signal;
generating a second PWM signal; and
controlling refresh rates in different dimensions of output data from a target apparatus respectively by using the first PWM signal and the second PWM signal.

9. The PWM signal generation method that can have two refresh rates of claim 8, wherein the target apparatus is a light processing device, and the first PWM signal and the second PWM signal are arranged to control the brightness of the output data in the different dimensions respectively.

10. The PWM signal generation method of claim 8, wherein the output data comprises a plurality of frames, wherein the first PWM signal generator generates a first PWM signal for determining a first refresh rate for all the frames, and the second PWM signal generator generates a second PWM signal for determining a second refresh rate for all the frames.

11. A PWM signal generation method that can have two refresh rates, wherein the PWM signal generation method is used by a target apparatus to generate an output data, and the output data comprises a plurality of data units, and the PWM signal generation method comprises:
generating a first PWM signal;
generating a second PWM signal; and
controlling a first part of each of the data units by the first PWM signal, and controlling a second part of each of the data units by using the second PWM signal, thus the output data can have two refresh rates;
wherein a position of the second part of each of the data units is decided randomly.

12. The PWM signal generation method of claim 11, wherein the target device is a light processing device, and the first PWM signal generator and the second PWM signal generator are arranged to control the brightness of the data units respectively.

13. The PWM signal generation method of claim 11, wherein the first PWM signal generator generates a first PWM signal, and the second PWM signal generator generates a second PWM signal, and the first parts of the data units corresponding to a first cycle of the first PWM signal show the same changes, and the second parts of the data units corresponding to a second cycle of the second PWM signal show the same changes.

14. The PWM signal generation method of claim 11, wherein the data units are frames, wherein the first PWM signal generator generates a first PWM signal for determining a first refresh rate for all the frames, and the second PWM signal generator generates a second PWM signal for determining a second refresh rate for all the frames.

15. A PWM circuit that can have two refresh rates, wherein the PWM circuit is used by a target apparatus to generate an output data, and the output data comprises a plurality of data units, and the PWM circuit comprises:
a first PWM signal generator; and
a second PWM signal generator;
wherein the first PWM signal generator controls a first part of each of the data units, and the second PWM signal generator controls a second part of each of the data units, thus the output data can have two refresh rates;
wherein the data units are frames, wherein the first PWM signal generator generates a first PWM signal for determining a first refresh rate for all the frames, and the second PWM signal generator generates a second PWM signal for determining a second refresh rate for all the frames.

16. A PWM signal generation method that can have two refresh rates, wherein the PWM signal generation method is used by a target apparatus to generate an output data, and the output data comprises a plurality of data units, and the PWM signal generation method comprises:
generating a first PWM signal;
generating a second PWM signal; and
controlling a first part of each of the data units by the first PWM signal, and controlling a second part of each of the data units by using the second PWM signal, thus the output data can have two refresh rates;
wherein the data units are frames, wherein the first PWM signal generator generates a first PWM signal for determining a first refresh rate for all the frames, and the second PWM signal generator generates a second PWM signal for determining a second refresh rate for all the frames.