Patent Publication Number: US-2013234673-A1

Title: Discharge circuit

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to discharge circuits, and more particularly to a discharge circuit for effectively increasing discharge time of battery. 
     2. Description of Related Art 
     Many portable electronic products, such as portable DVD players, mobile phones, MP3 and MP4 players and the like, use battery as power source. However, discharge time of the battery is very limited, and an increase in the discharge time of the battery is really required. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. 
       The drawing is a schematic circuit diagram of one embodiment of discharge circuit in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure will be described below, with reference to the accompanying drawings. 
     Referring to the drawing, the discharge circuit  10  is applied to portable electronic devices which uses battery as power source. The discharge circuit  10  is connected with a micro-controller  20 . The micro-controller  20  is pulled down to a logic low (low voltage) when only the battery is used as the power source and pulled up to a logic high (high voltage) when an adapter (not shown) is used to connect to an external power source (not shown). The discharge circuit  10  includes a discharging IC  12 , a first current-limiting resistance  14  and a delay discharge circuit  16 . 
     The discharging IC is connected with a system voltage Vs via the first current-limiting resistance  14 . When the discharging IC  12  detects any voltage input, minimum operating voltage of the discharging IC  12  is set to 6.3V; when the discharging IC  12  detects no voltage input, the minimum operating voltage of the discharging IC  12  is set to 5.5 V. The discharging IC  12  is Unicorn  20 . The discharge circuit  10  uses characteristics of the discharging IC  12  in making the discharging IC  12  unable to detect any voltage input when the battery is used as the power source, thereby the minimum operating voltage of the discharging IC  12  is set to 5.5V, which significantly increases discharge time of the battery. 
     The delay discharge circuit  16  is connected with the system voltage Vs via the first current-limiting resistance  14 . When only the battery is used as the power source, the delay discharge circuit  16  is used to make the discharging IC  12  unable to detect any voltage input, thereby the minimum operating voltage of the discharging IC  12  is set to 5.5V. When the adapter for the external power source is used, the delay discharge circuit  16  allows the discharging IC  12  to detect the voltage input, thereby the minimum operating voltage of the discharging IC  12  is set to 6.3 V. 
     The delay discharge circuit  16  is connected between the discharging IC  12  and the micro-controller  20 . The delay discharge circuit  16  includes a npn transistor  162 , a PMOS transistor  164 , a second current-limiting resistance  166 , and a third current-limiting resistance  168 . A base of the npn transistor  162  is connected with the micro-controller  20  via a third current-limiting resistance  168 , an emitter of the npn transistor  162  is grounded, a connector of the npn transistor  162  is connected with a gate of the PMOS transistor  16 , and connected with the system voltage Vs via the second current-limiting resistance  166 . The gate of the PMOS transistor  164  is connected with the second current-limiting resistance  166  and the connector of the npn transistor  162 , a source of the PMOS transistor  164  is connected with the system voltage Vs via the first current-limiting resistance  14 , and a drain of the the PMOS transistor  164  is connected with the discharging IC  12 . The first current-limiting resistance  14  is used to provide current-limiting protection when the PMOS transistor  164  is turned on, and the system voltage Vs provides power to the discharging IC. 
     When the adapter for the external power source is used, the micro-controller  20  is pulled up to the logic high, and the npn transistor  162  is turned on. The gate of the PMOS transistor  164  is pulled down to a logic low, the PMOS transistor  164  is turned on, and the discharging IC  12  is connected with the system voltage Vs via the first current-limiting resistance  14 . The discharging IC  12  can detect voltage input, thereby the minimum operating voltage of the discharging IC  12  is set to 6.3 V. When only battery is used as the power source, the micro-controller  20  is pulled down to a logic low, the npn transistor  162  is turned off, the gate of the PMOS transistor  164  is pulled up to the logic high, and the PMOS transistor  164  is turned off, which disconnects the discharging IC  12  and the first current-limiting resistance  14  from the system voltage Vs. The discharging IC  12  cannot detect any voltage input, thereby the minimum operating voltage of the discharging IC  12  is set to 5.5 V. 
     Although the features and elements of the present disclosure are described as embodiments in particular combinations, each feature or element can be used alone or in other various combinations within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.