Patent Application
20210029788
In a Light-Emitting Diode (LED) display system such as a Liquid Crystal Display (LCD) TV, a controller is used to control the power of multiple LED strings for back-lighting. Because the controller has a given number of control pins, only a limited number of LED strings can be controlled by one controller. In order to control more LED strings, more controllers are needed, which increases the cost of the system.
In embodiments, a controller for controlling a light source module including a first LED array and a second LED array includes a power input terminal, a first power output terminal and a second power output terminal. The power input terminal is operable for receiving electric power from a power converter. The first power output terminal is coupled to the first LED array, and the second power output terminal is coupled to the second LED array. The controller is operable for delivering the electric power to the first LED array via the first power output terminal in a first sequence of discrete time slots, and for delivering the electric power to the second LED array via the second power output terminal in a second sequence of discrete time slots. The first sequence of discrete time slots and the second sequence of discrete time slots are mutually exclusive.
In other embodiments, a controller is coupled to a power source and operable for controlling a light source module including a first LED array and a second LED array. Each of the first LED array and the second LED array includes multiple LED strings. The controller includes a switching module and a current regulation module. The switching module is coupled to the first LED array and the second LED array and is operable for alternately delivering power to the first LED array and to the second LED array. In other words, power is delivered to the first LED array (but not to another LED array), and then power is delivered to the second LED array (but not to another LED array), and so on depending on the number of LED arrays, and then the pattern/cycle is repeated. The current regulation module is coupled to the first LED array and the second LED array and is operable for linearly regulating a current of each LED string in the first LED array and a current of each LED string in the second LED array.
Features and advantages of embodiments of the claimed subject matter will become apparent as the following detailed description proceeds, and upon reference to the drawings, wherein like numerals depict like parts, and in which:
Reference will now be made in detail to the embodiments of the present invention. While the invention will be described in combination with these embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention.
The controller 180 receives electric power from a power converter 120. The power converter 120 is coupled between the controller 180 and a power source 110. The controller 180 includes a power input terminal PWIN, a feedback terminal FBOUT, multiple power output terminals PWO1-PWO4 and multiple current sensing terminals ISEN1-ISEN8. The number of the power output terminals is equal to the number of the LED arrays. The number of the current sensing terminals is equal to the number of the LED strings in each LED array. The controller 180 includes a switching module 130, a feedback control module 140, a current regulation module 150 and a decoding module 160.
The power input terminal PWIN is coupled to the power source 110 through the power converter 120 and is operable for receiving electric power from the power converter 120. The power output terminals PWO1-PWO4 are coupled to the LED arrays A1-A4, respectively. The controller 180 is operable for delivering the electric power to the LED arrays A1-A4 via the power output terminals PWO1-PWO4 in a first sequence, a second sequence, a third sequence, and a fourth sequence of discrete time slots, respectively. The first, second, third and fourth sequences of discrete time slots are mutually exclusive; that is, they do not overlap in time.
More specifically, the switching module 130 includes multiple switches SW1-SW4 that are coupled between the power input terminal PWIN and a corresponding power output terminal. For example, a first switch SW1 is coupled between the power input terminal PWIN and the first power output terminal PWO1, and a second switch SW2 is coupled between the power input terminal PWIN and the second power output terminal PWO2. Referring to
With reference back to
Continuing with reference to
The decoding module 160 is operable for receiving a timing signal from a timing controller 190 (e.g., a Micro Controlling Unit) and for generating a switching signal to control the switches SW1-SW4 in the switching module 130 based on the timing signal. The decoding module 160 is further operable for generating multiple control signals to control the current regulation module 150. Accordingly, multiple current regulation units (shown in
The LED arrays A1-A4 are configured to receive electric power from power output terminals PWO1-PWO4, respectively, and share the current sensing terminals ISEN1-ISEN8. More specifically, the anodes of the LED strings in the first LED array A1 are connected to a common node N1, and the common node N1 is connected to the first power output terminal PWO1. The anodes of the LED strings in the second LED array A2 are connected to a common node N2, and the common node N2 is connected to the second power output terminal PWO2. The anodes of the LED strings in the third LED array A3 are connected to a common node N3, and the common node N3 is connected to the third power output terminal PWO3. The anodes of the LED strings in the fourth LED array A4 are connected to a common node N4, and the common node N4 is connected to the fourth power output terminal PWO4.
On the other hand, the cathode of a first LED string in the first LED array A1, the cathode of a first LED string in the second LED array A2, the cathode of a first LED string in the third LED array A3 and the cathode of a first LED string in the fourth LED array A4 are connected to a first common node NC1. The common node NC1 is connected to a current sensing terminal ISEN1. Thus, the current sensing terminal ISEN1 senses the current on each of the first LED strings in each of the LED arrays. Similarly, the cathodes of each of the second LED strings in each LED array are connected to a second common node NC2 (not shown), which is connected to a current sensing terminal ISEN2 (not shown), and so on. The cathodes of each of the last (e.g., eighth) LED strings in each LED array are connected to the respective (e.g., eighth) common node NCB, which is connected to a current sensing terminal ISEN8.
In operation, if the switch SW1 is turned on, then a current flows through the first power output terminal PWO1, the common node N1 to the first LED array A1, and then back to the controller 180 through the common nodes NC1-NC8 and the current sensing terminals ISEN1-ISEN8. If the switch SW2 is turned on, then a current flows through the second power output terminal PWO2, the common node N2 to the second LED array A2, and then back to the controller 180 through the common nodes NC1-NC8 and the current sensing terminals ISEN1-ISEN8. As such, the configuration of the controller 180 and the structure of the circuit 100 allow the LED arrays A1-A4 to share the same group of current sensing terminals SEN1-ISEN8.
The current regulation module 150 includes multiple current regulation units 230_1-230_8 coupled to the current sensing terminals ISEN1-ISEN8, respectively. The current regulation units 230_1-230_8 are operable for linearly regulating current of each LED string in the LED arrays A1-A4, and each current regulation unit is independently and individually enabled and disabled by a corresponding control signal of control signals PWM1-PWM8. The control signals PWM1-PWM8 can be Pulse Width Modulation (PWM) signals.
More specifically, each current regulation unit 230_1-230_8 includes a respective amplifier 290_1-290_8 coupled to a respective switch Q1-Q8. Each switch Q1-Q8 is in coupled in series with a corresponding LED string. Each current regulation unit has a similar configuration. Take current regulation unit 230_1 as an example. A non-inverting input of the amplifier 290_1 receives a reference signal ADJ1 indicative of a target current. An inverting input of the amplifier 290_1 receives a sensing signal IS1 indicative of a level of a current through the corresponding LED string. The amplifier 290_1 compares the reference signal ADJ1 with the sensing signal IS1 to generate an error signal EA1, and linearly controls the switch Q1 with the error signal EA1 so as to regulate the current of the corresponding LED string so that current is at the target current. The switch Q1 is controlled linearly means that, instead of either being fully turned on or fully turned off, the switch Q1 can be partially turned on such that a level of the current flowing through the switch Q1 can be continuously (non-discretely) and gradually adjusted.
The amplifier 290_1 is controlled by a control signal PWM1. If the control signal PWM1 is in a first state (e.g., logic high), then the amplifier 290_1 is enabled and the corresponding LED string is turned on and regulated as described above. If the control signal PWM1 is in a second state (e.g., logic low), then the amplifier 290_1 is disabled and the corresponding LED string is turned off.
In an embodiment, the decoding module 160 includes a SPI decoder 210, a PWM generator 220, a digital-analog convertor (DAC) 240, and a reference selection unit 250. The SPI decoder 210 receives a timing signal from a timing controller (not shown) and decodes the timing signal. The PWM generator 220 is coupled to the SPI decoder 210 and generates the control signals PWM1-PWM8 based on the timing signal. The DAC 240 is coupled to the SPI decoder and generates reference signals ADJ1-ADJ8. The reference selection unit 250 selects either the reference signals ADJ1-ADJ8 or a system reference signal SYS_REF that is also generated from the SPI decoder 210, and supplies the selected signal(s) (e.g., ADJ1-ADJ8 or SYS_REF) to the respective amplifier 290_1-290_8. That is, either the non-inverting input of the amplifier 290_1 receives the signal ADJ1, the non-inverting input of the amplifier 290_2 receives the signal ADJ2, and so on, or the non-inverting inputs of the amplifiers 290_1-290_8 all receive the signal SYS_REF. Furthermore, the decoding module 160 processes the timing signal and provides a switching signal to the switching module 130. The switching module 130 controls the switches SW1-SW4 with the switching signal to turn on the switches SW1-SW4 in four sequences of discrete time slots that are mutually exclusive.
As described above, the present invention includes a controller for controlling a light source module. The controller is operable for alternately delivering electric power to multiple LED arrays, and for regulating the current of each LED string in the LED arrays. The controller enables the LED arrays to share a same group of current sensing terminals of the controller. Advantageously, multiple LED arrays can be controlled by a single controller, and thus the cost of the system is reduced. Moreover, each LED string in the LED arrays can be independently and individually regulated or disabled, which allows flexible and fine (accurate or precise) levels of dimming in a display system.
While the foregoing description and drawings represent embodiments of the present invention, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope of the principles of the present invention as defined in the accompanying claims. One skilled in the art will appreciate that the invention may be used with many modifications of form, structure, arrangement, proportions, materials, elements, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims and their legal equivalents, and not limited to the foregoing description.
