EP2717249A1

EP2717249A1 - LED indicator and heating cooker having same

Info

Publication number: EP2717249A1
Application number: EP13187015.6A
Authority: EP
Inventors: Kiyoshi Nakashita
Original assignee: Panasonic Corp
Current assignee: Panasonic Corp
Priority date: 2012-10-04
Filing date: 2013-10-02
Publication date: 2014-04-09
Also published as: JP6244537B2; JP2014074791A

Abstract

An LED indicator (20) includes a plurality of display portions (15a, 15b), a plurality of LEDs each corresponding to one of the plurality of display portions (15a, 15b), and a microcomputer (2) for controlling a lighting period of the LEDs based on a dynamic lighting method. The plurality of display portions (15a, 15b) include a first display portion (15a) and a second display portion (15b) having a display area greater than that of the first display portion (15a). The lighting period of the LEDs corresponding to the first display portion (15a) is longer than that of the LEDs corresponding to the second display portion (15b), thereby making it possible to effectively restrain a flicker phenomenon.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an LED indicator employing a microcomputer and also to a heating cooker having the same.

Description of the Related Art

In an example of LED (Light-Emitting Diode) indicators for use in microwave ovens, LEDs (LED display elements) are accommodated within a light-blocking casing, a portion of which is translucent and the rest of which is a light-blocking portion, and the LEDs are lighted up within the light-blocking casing, thereby enabling a user to recognize an alphabet or character or a pictograph which is desired to be displayed. A method of lighting the LEDs is, for example, a dynamic lighting method, in which the LEDs are arrayed in the form of a matrix. Columns of the matrix are always driven on a time-division basis and, in rows of the matrix, transistor elements employed as switches provided depending on a state of array are periodically appropriately turned on and off based on predetermined control pulses. By doing so, those LEDs that are turned on in both the columns and the rows of the matrix are selectively lighted up.
A method of controlling the brightness of the LED indicator is disclosed in, for example, Patent Document 1 or 2. According to the method as disclosed in Patent Document 1 or 2, the brightness is controlled by setting a duty of the control pulses in the rows of the matrix to control the lightening length when the LEDs connected to the columns of the matrix are being driven.
Also, Patent Document 3 discloses a method of performing an N-fold speed display (N=2, 3, ···; a natural number) in which a frame of a screen on, for example, a personal computer is displayed more than once. In this method, a time period during which the LEDs are in an off-state becomes short and, hence, a difficulty is encountered in sensing the lights-out of the LEDs.

Prior Art Documents

Patent Document 1: Japanese Laid-Open Patent Publication No. 2002-287680
Patent Document 2: Japanese Laid-Open Patent Publication No. 4-306050
Patent Document 3: Japanese Laid-Open Patent Publication No. 11-161230

SUMMARY OF THE INVENTION

In display portions of the LED indicator, however, the display area may differ depending on the kind of the display portions. In such a case, if the brightness of each LED is the same, the brightness differs with respect to each display portion and, hence, it is likely that a flicker phenomenon (a phenomenon in which the blink of the LEDs is sensed) may occur particularly in a display portion having an increased brightness. Also, emission colors of the LEDs may differ and if the emission colors differ, even though the LEDs have the same brightness, the flicker phenomenon may be easily sensed because the sense of the human eye of sensing the lights-out of the LEDs changes.
Because the methods of Patent Documents 1-3 do not take account of the difference in display areas of the display portions, they cannot effectively restrain the occurrence of the flicker phenomenon.
The present invention has been developed to overcome the above-described disadvantages. It is accordingly an objective of the present invention to provide an LED indicator capable of restraining the occurrence of the flicker phenomenon and also provide a heating cooker having the same.
In accomplishing the above and other objectives, the LED indicator according to the present invention includes a plurality of display portions, a plurality of LEDs each corresponding to one of the plurality of display portions, and a microcomputer for controlling a lighting period of the LEDs based on a dynamic lighting method. The plurality of display portions include a first display portion and a second display portion having a display area greater than that of the first display portion. The lighting period of the LEDs corresponding to the first display portion is longer than that of the LEDs corresponding to the second display portion.
Also, a heating cooker according to the present invention includes the LED indicator as referred to above, a heating chamber for accommodating an object to be heated therein, a door for opening and closing the heating chamber, a heating portion for heating the object accommodated within the heating chamber, a main control circuit for controlling the heating portion, and an input portion for allowing a user to set a cooking menu.
Because the LED indicator and the heating cooker according to the present invention change the lighting period of the LEDs depending on the display areas of the display portions, the flicker phenomenon can be restrained.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and features of the present invention will become apparent from the following description of preferred embodiments thereof with reference to the accompanying drawings.

Fig. 1 is a block diagram of an LED indicator according to an embodiment of the present invention.
Fig. 2 is a detailed configuration diagram of a display portion of the LED indicator according to the embodiment.
Fig. 3 is a block diagram of a heating cooker according to the embodiment.
Fig. 4 is a timing chart of an LED display method as employed in the LED indicator according to the embodiment.
Fig. 5 is a flowchart of the LED display method of the LED indicator according to the embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first invention is directed to an LED indicator (20) having a plurality of display portions (15a, 15b), a plurality of LEDs each corresponding to one of the plurality of display portions (15a, 15b), and a microcomputer (2) for controlling a lighting period of the LEDs based on a dynamic lighting method,
characterized in that
the plurality of display portions (15a, 15b) comprise a first display portion (15a) and a second display portion (15b) having a display area greater than that of the first display portion (15a), and
the lighting period of the LEDs corresponding to the first display portion (15a) is longer than that of the LEDs corresponding to the second display portion (15b).
Thus, it is possible to effectively restrain the flicker phenomenon.
A second invention is directed to the LED indicator (20) according to claim 1, wherein if a display color of the LEDs is white, the lighting period of the LEDs is reduced compared with a case where the display color of the LEDs is in other colors.
Thus, it is possible to effectively restrain the flicker phenomenon.
A third invention is directed to a heating cooker (30) having a heating chamber for accommodating an object to be heated therein, a door for opening and closing the heating chamber, a heating portion (14) for heating the object accommodated within the heating chamber, a main control circuit (12) for controlling the heating portion (14), and an input portion (13) for allowing a user to set a cooking menu,
characterized by an LED indicator (20) according to the first invention or second invention.
Thus, it is possible to effectively restrain the flicker phenomenon.
Embodiments of the present invention are described hereinafter with reference to the drawings, but the present invention is not limited by the embodiments.

(Embodiments)

Fig. 1 is a block diagram of an LED indicator 20 according to an embodiment of the present invention. As shown in Fig. 1, the LED indicator 20 includes an LED display unit 1, a microcomputer 2, a scanning line output circuit 3, and a display data output circuit 4.
The LED display unit 1 includes a plurality of LEDs and a plurality of display portions (described later with reference to Fig. 2). In the LED display unit 1, the LEDs are arrayed in the form of a matrix. As shown in Fig. 1, columns of the matrix are referred to as COM1-COM6 and rows of the matrix are referred to as SEG1-SEG7.
As shown in Fig. 1, the LED display unit 1 is connected to the microcomputer 2 via the scanning line output circuit 3 and the display data output circuit 4. Specifically, six pins of the microcomputer 2 are respectively connected to COM 1 to COM6 of the LED display unit 1 via the scanning line output circuit 3, and seven other pins of the microcomputer 2 are respectively connected to SEG1 to SEG7 of the LED display unit 1 via the display data output circuit 4.
The microcomputer 2 sends a high signal or a low signal to the scanning line output circuit 3 and the display data output circuit 4. Each of the scanning line output circuit 3 and the display data output circuit 4 is made up of a transistor and rendered to be in a conductive state (on-state) when it receives a high signal from the microcomputer 2. This renders a corresponding one of the COMs and the SEGs of the LED display unit 1 to be in a high state. On the other hand, each of the scanning line output circuit 3 and the display data output circuit 4 is rendered to be in a non-conductive state (off-state) when it receives a low signal from the microcomputer 2. This renders a corresponding one of the COMs and the SEGs of the LED display unit 1 to be in a low state. In the LED display unit 1, an LED corresponding to one of the COMs and one of the SEGs both rendered to be in a high state is turned on. In the LED display unit 1 according to this embodiment, a dynamic method is employed wherein each LED is periodically turned on for display.
An example of the LED display unit 1 so configured is shown in Fig. 2. As shown in Fig. 2, a display portion 15 of the LED display unit 1 includes a seven-segment display portion 15a and a unit display portion 15b. The seven-segment display portion 15a is made up of four groups of seven segments and the unit display portion 15b is made up of three units "kg", "h" and "min". By way of example, the ones digit (rightmost side in Fig. 2) of the seven-segment display portion 15a includes an uppermost segment 5, an upper right segment 6, a lower right segment 7, a lowermost segment 8, a lower left segment 9, an upper left segment 10, and a middle segment 11. Each of those segments 5-11 corresponds to one of the LEDs (not shown in Fig. 2 because it is located on the rear side of the display portion 15).
When a number two is displayed, for example, five LEDs corresponding to the segments 5, 6, 8, 9 and 11 are turned on.
Each of the units "kg", "h" and "min" of the unit display portion 15b corresponds to one of the LEDs.
A correspondence relationship between the display portion 15 and the COMs and the SEGs of the matrix (Fig. 1) is explained hereinafter.
In this embodiment, COM1 to COM4 correspond to the seven-segment display portion 15a and COM5 and COM6 correspond to the unit display portion 15b, Specifically, COM1 corresponds to the leftmost group of seven segments (thousands digit) in Fig. 2, COM2 corresponds to the second group of seven segments from the left (hundreds digit) in Fig. 2, COM3 corresponds to the third group of seven segments from the left (tens digit) in Fig. 2, and COM4 corresponds to the rightmost group of seven segments (ones digit) in Fig. 2. COM5 corresponds to the unit "min" of the unit display portion 15b and COM6 corresponds to the units "kg" and "h" of the unit display portion 15b.
SEG1 to SEG7 of the matrix correspond to the segments 5-11 of the seven-segment display portion 15a, respectively. SEG6 also corresponds to the unit "min" of the unit display portion 15b. SEG5 and SEG4 also correspond to the units "kg" and "h" of the unit display portion 15b, respectively.
In such a configuration, in order to light the ones digit segment 5 of the seven-segment display portion 15a, SEG1 is rendered to be in a high state when COM4 is in a high state. Similarly, in order to light the ones digit segment 6 of the seven-segment display portion 15a, SEG2 is rendered to be in a high state when COM4 is in a high state. Similarly, in order to light the unit "min" of the unit display portion 15b, SEG6 is rendered to be in a high state when COM5 is in a high state.
Fig. 3 depicts a connection block diagram of a heating cooker 30 having the LED indicator 20 in this embodiment.
As shown in Fig. 3, the heating cooker 30 includes an LED indicator 20 having an LED display unit 1, a microcomputer 2 and the like, a heating portion 14, a main control circuit 12, and an input portion 13. The heating portion 14 is intended to heat an object to be heated accommodated within a heating chamber (not shown) that can be opened and closed by a door (not shown). The main control circuit 12 is a circuit to control the heating portion 14 and connected to the microcomputer 2. The input portion 13 is intended to allow a user to set a cooking menu and connected to the microcomputer 2.
In the heating cooker of the above-described construction, the microcomputer 2 controls the heating portion 14 using the main control circuit 12. Also, information (information such as, for example, "during an off-state", "during cooking" or "during setting") associated with the heating cooker 30, which is controlled by the microcomputer 2, changes based on the contents that are inputted by the user with the use of the input portion 13. Depending on the state of the heating cooker 30 that changes in this way, the microcomputer 2 controls the indication on the LED display unit 1.
The behavior and operation of the LED indicator 20 of the heating cooker 30 of the above-described construction are explained hereinafter with reference to Fig. 4.
Fig. 4 is a timing chart of an LED display method as employed in the LED indicator 20 and depicts LED-lighting periods (time periods during which the LEDs are lighted up). The timing chart shown in Fig. 4 is a timing chart to display "0 min" on the display portion 15 of the LED display unit 1 shown in Fig. 2. In order to display "0 min", a number "0" is displayed in the ones digit of the seven-segment display portion 15a and "min" is displayed on the unit display portion 15b.
In Fig. 4, the timings at which COM1 to COM6 are rendered to be in a high state and those at which SEG1 to SEG7 are rendered to be in a high state are shown. Also, periods 1-5 are set in Fig. 4 with one period set as a time interval in which each of COM1 to COM6 is rendered to be in a high state once.
As shown in Fig. 4, COM1 to COM6 are controlled such that they are sequentially rendered to be in a high state at a constant duty ratio. A pulse width (time period during which a COM is in a high state) in this embodiment is, for example, 500 microseconds. More specifically, a high signal is outputted from a pin of the microcomputer 2 connected to COM1 to render a transistor of the scanning line output circuit 3 to be in an on-state and COM1 to be in a high state. This state is maintained for 500 microseconds.
A low signal is subsequently outputted from the pin of the microcomputer 2 connected to COM1 to render the transistor of the scanning line output circuit 3 to be in an off-state and COM1 to be in a low state. At the same time, COM2 is maintained in a high state for 500 microseconds. Similariy, COM4, COM5 and COM6 are sequentially rendered to be in a high state every 500 microseconds. After COM6 has been rendered to be in a high state, COM1 is again controlled. In this way, the same cycle is repeated to scan each COM of the matrix every 500 microseconds.
On the other hand, SEG1 to SEG7 are controlled based on a pattern that has been stored in the microcomputer 2 in advance. Specifically, as shown in Fig. 4, when COM4 is in a high state in the periods 1, 3 and 5 of the periods 1-5, SEG1 to SEG6 are rendered to be in a high state. More specifically, high signals are sent from pins of the microcomputer 2 corresponding to SEG1 to SEG6 to the display data output circuit 4 to render SEG1 to SEG6 to be in a high state. As a result, a number "0" is displayed in the ones digit of the seven-segment display portion 15a. A lighting period (time period) of the LEDs to display the number "0" is 6.0 milliseconds (500 microseconds x 12), as shown in Fig. 4.
Further, as shown in Fig. 4, when COM5 is in a high state in the periods 1-5, SEG6 is rendered to be in a high state. Specifically, a high signal is sent from a pin of the microcomputer 2 corresponding to SEG6 to the display data output circuit 4 to render SEG6 to be in a high state. As a result, "min" is displayed on the unit display portion 15b. A lighting period of the LEDs to display "min" is 3.0 milliseconds (500 microseconds x 6), as shown in Fig. 4.
According to the above-described LED display method, in one cycle from the period 1 to the period 5, "0" is displayed thrice and "min" is displayed five times. That is, the brightness level of "0" is set to 3 and that of "min" is set to 5. The brightness level in this application means the brightness of the display portion 15, i.e., the degree of brightness which the user senses.
As shown in Fig. 2, the seven-segment display portion 15a and the unit display portion 15b differ in display area and, for example, the display area of each segment is smaller than that of "min". In this embodiment, the lighting period of the LEDs corresponding to the display portion (first display portion) that is smaller in display area is longer than that of the LEDs corresponding to the display portion (second display portion) that is larger in display area (6.0 milliseconds > 3.0 milliseconds). The lighting period of the LEDs is changed depending on the display area of the display portion in this way to change the brightness level of the display portion, thereby making it possible to effectively restrain the flicker phenomenon.
By way of example, if the brightness of the LEDs is set to 1 (lowest value), the lighting period is as long as 15.0 milliseconds (500 microseconds x 30). In this embodiment, however, the pulse width of the COMs is set to a value as short as 500 microseconds to thereby make it difficult to sense the flicker phenomenon. That is, unlike in the case where the pulse width of the COMs is, for example, 2.5 milliseconds, even if the brightness level is set to 1, it can be made possible for the sense of a relative brightness difference of the human eye not to sense the flicker phenomenon.
In this way, in this embodiment, the pulse width of the LEDs is set to 500 microseconds and the scanning cycle of the COMs is set to 5 periods for one display processing. By doing so, the brightness of each display portion 15 and the lighting period of the LEDs can be controlled, thereby making it possible to effectively restrain the flicker phenomenon.
A specific procedure required for performing the timing chart of Fig. 4 is explained hereinafter with reference to Fig. 5. Fig. 5 is a flowchart of the LED display method of the LED indicator in this embodiment.
As shown in Fig. 5, a default setting or initialization is conducted at step S1. Specifically, the microcomputer 2 sets the number of the COMs to 1 to set the number of the periods to 1. The number of the COMs is a counter to control as to which of COM1 to COM6 should be rendered to be in a high state. The number of the periods is a counter to control as to which of the periods 1-5 is under control.
At step S2, the microcomputer 2 sends low signals to all of COM1 to COM6 to render COM1 to COM6 to be in a low state.
At step S3, a high signal is sent to a COM corresponding to the number of the COMs set at step S1 (rendered to be in a high state). The high signal is sent to, for example, COM1.
At step S4, a SEG corresponding to the display portion 15 to be displayed is determined based on information controlled by the microcomputer 2 (information associated with the cooking menu, the lighting period of the LEDs and the like that have been set). At step S5, the microcomputer 2 sends a high signal to the SEG determined at step S4 to render this SEG to be in a high state (this SEG is turned on).
At steps S3 and D5, the selected COM and SEG are each rendered to be in a high state to light an LED corresponding to the COM and the SEG both rendered to be in the high state.
At step S6, the procedure stands by in such a state for 500 microseconds to thereby maintain the lighting state of the LED and light the LED for 500 microseconds.
At step S7, the number of the COMs is counted up. For example, COM1 is counted up to COM2.
At step S8, a determination is made as to whether or not the number of the COMs is greater than or equal to 7. If a determination is made that the number of the COMs is greater than or equal to 7, the procedure advances to the next step S9. On the other hand, if a determination is made that the number of the COMs is less than 7, the procedure returns to step S2.
At step S9, the number of the COMs is returned to 1.
At step S10, the number of the periods is counted up. For example, the first period is counted up to the second period.
At step S11, a determination is made as to whether or not the number of the periods is greater than or equal to 6. If a determination is made that the number of the periods is greater than or equal to 6, the number of the periods is returned to 1 (at step S12) and the procedure returns to step S2. Thereafter, the same flow is repeated. If a determination is made that the number of the periods is less than 6, the procedure similarly returns to step S2.
At steps S1-S12 as referred to above, all the steps except step S7 are performed substantially simultaneously to conduct the LED display method according to the control as shown in Fig. 4.
In this embodiment, the LED indicator 20 is applied to the heating cooker 30. Because the LED indicator 20 has a longer life than an LCD indicator, in the case where the LED indicator 20 is applied to the heating cooker 30, the need for replacement of the LED indicator 20 is reduced, thus making it possible to enhance the maintenance of the heating cooker 30. This is particularly effective in using a built-in heating cooker or a heating cooker suspended from a ceiling.
The present invention is not limited to the above-described embodiment but practicable in various other embodiments. By way of example, the lighting period of the LEDs in the LED display unit 1 may be changed based on a display color of the LEDs. When green LEDs are compared with white LEDs, the white LEDs are brighter and accordingly more sensitive to the flicker phenomenon due to a relative brightness difference between a lighting state and a lights-out state. Also, because the relative brightness difference between the lighting state and the lights-out state increases with an increase in brightness of the LEDs, the flicker phenomenon is likely to be sensed. Taking notice of this point, if the display color of the LEDs used is white, the lighting period may be reduced compared with the case where the display color is other than white (for example, green, red, blue or the fike). By doing so, even if the white LEDs, which are higher in brightness than LEDs in other colors and sensitive to the flicker phenomenon, are used, the flicker phenomenon can be effectively restrained. Although attention is paid to the brightness according to the difference in LED color, the lighting period may be changed not just in this case but depending on, for example, the brightness of the LEDs or the degree of whiteness. Even in such cases, the flicker phenomenon can be similarly effectively restrained.
Also, although in this embodiment the case where the periods 1-5 are set is explained, the present invention is not limited thereto and, in addition to the periods 1-5, a period 6 may be set as a waiting time during which a lighting processing of the LEDs or the like is not performed.
Further, although in this embodiment the case where there exist the seven-segment display portion 15a and the unit display portion 15b as the display portion 15 is explained, the present invention is not limited thereto and a pictograph display portion for displaying pictographs may be further provided. In such a case, the pictograph display portion can be periodically lighted as well as the seven-segment display portion 15a and the unit display portion 15b by relating arbitrary COM and SEG to the pictograph display portion.
Any combination of the various embodiments referred to above can produce respective effects.
Although the present invention has been fully described by way of preferred embodiments with reference to the accompanying drawings, it is to be noted here that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications otherwise depart from the scope of the present invention as set forth in the appended claims, they should be construed as being included therein.
As described above, because the LED indicator according to the present invention can be realized with only a change in software configuration, the present invention is applicable to heating cookers or other electrical products.

Claims

An LED indicator (20) having a plurality of display portions (15a, 15b), a plurality of LEDs each corresponding to one of the plurality of display portions (15a, 15b), and a microcomputer (2) for controlling a lighting period of the LEDs based on a dynamic lighting method,
characterized in that
the plurality of display portions (15a, 15b) comprise a first display portion (15a) and a second display portion (15b) having a display area greater than that of the first display portion (15a), and
the lighting period of the LEDs corresponding to the first display portion (15a) is longer than that of the LEDs corresponding to the second display portion (15b).
The LED indicator (20) according to claim 1, wherein if a display color of the LEDs is white, the lighting period of the LEDs is reduced compared with a case where the display color of the LEDs is in other colors.
A heating cooker (30) having a heating chamber for accommodating an object to be heated therein, a door for opening and closing the heating chamber, a heating portion (14) for heating the object accommodated within the heating chamber, a main control circuit (12) for controlling the heating portion (14), and an input portion (13) for allowing a user to set a cooking menu,
characterized by an LED indicator (20) according to claim 1 or 2.