Patent Application
20140339921
This application claims the benefits of the Taiwan Patent Application Serial NO. 102117489 filed on May 17, 2013, the subject matter of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a light load current detection system and more particularly, relates to a light load current detection system determining whether a current value of a light load current reaching a threshold and then determining whether to switch off a switch.
2. Description
In terms of the efficiency of a power switch for a mobile charger, nowadays people value more on both full and light loads efficiency at the same time rather than full but heavy loads. Usually when a user charges his/her cellphone with a power adaptor, he/she will have to remove the power adaptor by himself/herself after seeing the screen of the cellphone showing that the phone has been fully charged, which is very inconvenient.
When applying a light load current detection to a mobile charger, it is more convenient and useful for a user. More specifically, with the assistance of a Micro Control Unit (MCU) in the mobile charger, an application circuit is utilized for detecting whether the cellphone is fully charged; after the cellphone is fully charged, the MCU will inform the application circuit to cut off the power, so that the system of the cellphone enters energy-saving mode or sleep mode.
However, present application circuits with the light load current detection require certain components. For example, in the market, an amplifier circuit is utilized to amplify signals generated from the conversion of a load current into a voltage and to send the amplified signals to a processor. However, there are disadvantages in this method: 1) Since the signals of voltages are weak, a precision amplifier with low offset is required; however, the usage of precision amplifier with low offset increases the cost and size; as a result, it is a challenge for developing a light-weighted and small-sized product. 2) A sensing resistance is required to convert the load current into the voltage; however, the usage of the sensing resistance easily causes energy-loss and low conversion efficiency.
In prior art, most application circuits have disadvantages such as high cost, waste of space and low conversion efficiency. Thus, a light load current detection system is provided according to embodiments of the present invention, in which a pre-simulated data table is stored in an application circuit and a current value of the light load current is detected according to the data table so as to determine whether to switch off a switch or not.
A light load current detection system is provided according to an embodiment of the present invention for detecting a current value of a light load current of a load in a light load mode, the load electrically connecting a switch, the light load current detection system including a detection process module and a control circuit. The detection process module electrically connects an input voltage source and electrically connected to the load via the switch, the detection process module including a power save unit and a voltage detection module. The power save unit sends a power save signal in the light load mode, wherein a cycle of the power save signal corresponds to a switch time. The voltage detection module electrically connects the input voltage source for detecting an input voltage value of the input voltage source to generate and output a detection signal.
The control circuit includes a data table and a threshold, the data table shows a relation among the cycle, the current value and the input voltage value, the control circuit electrically connects the power save unit, the voltage detection module and the switch for receiving the power save signal and the detection signal, obtaining the current value according to the data table, the cycle and the input voltage value, and determining whether the current value reaching the threshold, wherein when the control circuit determines the current value reaches the threshold, the switch is turned off in the light load module.
A light load current detection is provided according to anther embodiment of the present invention, which is different from the above embodiment in that the power save unit electrically connects a power switch and sends a power save signal. Furthermore, a cycle of the power save signal corresponds to a switch state, wherein the switch state includes a switch time and a switch pulse number. The cycle is determined by the ratio of switch time and non-switch time of the power switch or determined by the number of switch pulse number of the power switch. As a result, the control circuit obtains the current value according to the data table, the cycle and the input voltage value, and determining whether the current value reaching the threshold, wherein when the control circuit determines the current value reaches the threshold, the switch is turned off in the light load module.
According to embodiments of the present invention, the control circuit includes a Micro Control Unit (MCU). The detection process module further includes an activation input end, the control circuit electrically connecting the detection process module via the activation input end, when the control circuit determines the current value reaches the threshold, the control circuit simultaneously outputs a switch-off signal to the activation input end so as to turn off the detection process module. The load is selected from the group of a cellphone, a tablet computer and a laptop computer.
Accordingly, precision amplifier and sensing resistance are no longer required. Instead, merely a data table is required for the detection of light load currents. Thus, the problems of high cost, waste of space and low conversion efficiency no longer bother.
Other features and advantages of this invention will become more apparent in the following detailed description of the preferred embodiments of this invention, with reference to the accompanying drawings.
The present invention relates to a light load current detection system. In the following description, numerous details are set forth in order to provide a thorough understanding of the present invention. It will be appreciated by one skilled in the art that variations of these specific details are possible while still achieving the results of the present invention. In other instance, well-known components are not described in detail in order not to unnecessarily obscure the present invention.
Refer to
The light load current detection system 1 including a detection process module 11 and a control circuit 12, the detection process module 11 electrically connecting an input voltage source 4 and electrically connected to the load 2 via the switch 3, wherein the detection process module 11 includes a processing circuit for DC to DC.
The detection process module 11 electrically connects the switch 3 via an inductance (not shown), a diode (not shown), a capacitance (not shown) and two resistances (not shown). The design of its circuit varies according to various usages. The detection process module 11 includes a power save unit 111, a voltage detection module 112, an activation input end 113, a power switch 114, a comparator 115 and compensator 116 and a compensation comparator 117.
The power save unit 111 includes an ordinary circuit; the voltage detection module 112 includes a present circuit for detecting voltage; the detection module 112 electrically connects the input voltage source 4. The activation input end 113 can be one of an input pin of the detection process module. The power switch 114 (same as a power switch 114a of
The control circuit 12 electrically connects the power save unit 111, the voltage detection module 112 and the switch 3. According to the first embodiment of the present invention, the control circuit 12 electrically connects the detection process module 11 via the activation input end 113. The control circuit 12 includes a Micro Control Unit (MCU). In other embodiments of the present invention, the control circuit 12 includes a Complex Programmable Logic Device (CPLD) and an Application-Specific Integrated Circuit (ASIC).
Please refer to
According to the first embodiment of the present invention, the power save signal S1 is relevant with the load 2. The relation between the power save signal S1 and load 2 is that the power save signal S1 is determined by the following process: the feedback voltage fed from the load 2 is firstly compared with the comparator 115, and the output signal of comparator 115 compensated by the compensator 116, and the power save signal S1 is determined by compensation comparator 117.
The voltage detection module 112 detects an input voltage value of the input voltage source 4, generates and outputs a detection signal S2 accordingly. The detection signal S2 represents the mentioned input voltage value. The control circuit 12 includes a data table (as shown in
The control circuit 12 receives the power save signal S1 and the detection signal S2, obtains the current value of the light load current I according to the data table, the cycle and the input voltage value, and determines whether the current value reaching the threshold, wherein when the control circuit 12 determines the current value reaches the threshold, the switch 3 is turned off in the light load module. For example, a preferred method of turning off the switch 3 is to make the control circuit 12 send a turning-off signal to the switch 3.
According to
Furthermore, when the control circuit 12 determines the current value reaching the threshold, the control circuit 12 simultaneously outputs a switch signal S3 to the activation input end 113, switches off the detection process module 11, and switches off the light load current detection system 1 so as to further decrease the energy consumption.
Refer to
Refer to
For example, when the switch state is a switch time, the switch time is defined as the ratio of switch time and non-switch time of the power switch 114a. Further, as shown in
Take the switch state being a switch pulse number for example. Within a unit time interval (t1+t2, according to the second embodiment of the present invention), when the load 2a is lighter, the time interval t2 decreases, so the pulse numbers within the unit time interval also decrease; on the contrary, when the load 2a is heavier, the time interval t2 increases, so the pulse numbers within the unit time interval also increase. Therefore, the power save signal S1a with a cycle corresponding to the pulse number can be output, so the control circuit 12a receives the power save signal S1a and a detection signal S2a, obtains the current value of a light load current Ia according to the data table.
In conclusion, precision amplifiers and sensing resistances are no longer required according to embodiments of the present invention. Instead, merely a data table is required for the detection of light load currents. Thus, the problems of high cost, waste of space and low conversion efficiency no longer bother.
While the present invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be without departing from the spirit and scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102117489 | May 2013 | TW | national |
