System and method for dynamic load sharing between electronic displays
View Patent ↗A system and method for allocating power to a plurality of displays is disclosed. An exemplary system preferably includes an AC current sensor, a power load sharing controller, ambient light sensors for each display, and a brightness controller for each display. A maximum total current draw may be selected. The ambient light contacting each display may be measured and a corresponding desired brightness calculated. Depending on the present amount of current draw, the system determines if the displays can be driven at the desired brightness without exceeding the maximum total current draw. If yes, the displays are driven at their desired brightness. If no, the desired brightness for each display may be slightly reduced to prevent exceeding the maximum total current draw. Thus, as the ambient light varies between the displays, the available power may be shared.
1. A method for allocating power between a first and second display, comprising the steps of:
selecting a maximum allowable total current draw for the first and second display;
measuring the amount of ambient light contacting the first display;
measuring the amount of ambient light contacting the second display;
calculating a desired brightness for the first display;
calculating a desired brightness for the second display;
measuring the amount of total current being drawn by the first and second displays; and
determining if the first and second displays can be driven to their respective desired brightness without exceeding the maximum allowable total current draw and
driving the first and second displays at their desired brightness if yes, and
reducing the respective desired brightnesses and driving the first and second displays at the reduced brightness if no;
wherein the step of reducing the respective desired brightness is performed by applying a common derating value to the first and second display's desired brightness value.
2. The method of claim 1 wherein:
the first and second displays are positioned so that they are not co-planar.
3. The method of claim 1 wherein:
the first and second displays are liquid crystal displays.
4. The method of claim 1 wherein:
the first and second displays are OLED displays.
5. A method for allocating power between a first and second display, comprising the steps of:
(A) selecting a common derating value (k) which varies between k min and k max where k represents the relative amount of current to be sent to each display;
(B) setting k equal to k min ;
(C) selecting a maximum total current draw (IA) for the two displays;
(D) selecting a tolerance (t) for (IA);
(E) measuring the amount of ambient light contacting the first display;
(F) measuring the amount of ambient light contacting the second display;
(G) calculating a desired brightness (D 1 ) for the first display based on the measured amount of ambient light;
(H) calculating a desired brightness (D 2 ) for the second display based on the measured amount of ambient light;
(I) measuring the amount of total current (IL) being drawn by the first and second displays;
(J) increasing k if IL<IA−t;
(K) decreasing k if IL>IA+t;
(L) applying k to D 1 to create brightness setting (B 1 );
(M) applying k to D 2 to create brightness setting (B 2 );
(N) driving the first display at B 1 ;
(O) driving the second display at B 2 ; and
(P) repeating steps (E)-(O).
6. The method of claim 5 further comprising the steps of:
setting k=k min if k<k min and
setting k=k max if k>k max .
7. The method of claim 5 further comprising the steps of:
selecting a maximum brightness (LU) for the first and second displays;
selecting a minimum brightness (LL) for the first and second displays;
setting B 1 =LU if B 1 >LU;
setting B 2 =LU if B 2 >LU;
setting B 1 =LL if B 1 <LL; and
setting B 2 =LL if B 2 <LL.
8. The method of claim 5 wherein:
k min is equal to 0; and
k max is equal to 1.
9. The method of claim 5 wherein:
the step of applying k to D 1 is performed by multiplying k with D 1 ; and
the step of applying k to D 2 is performed by multiplying k with D 2 .
10. The method of claim 5 wherein:
the first and second displays are OLED displays.
11. The method of claim 5 wherein:
the first and second displays are liquid crystal displays.