Patent Publication Number: US-9419386-B2

Title: Indication circuit for indicating types of voltages

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an indication circuit for indicating types of voltages. 
     2. Description of Related Art 
     The recommended standard 232 (RS232) connector are widely used in the computer industry. The RS232 connector may provide various voltages between a computer and other devices, so that the devices may not need to acquire power from an external power source. Usually, the RS232 connector may provide 5 volts (V) or 12 V. However, a user may be unable to distinguish the RS232 connector with 5V from the RS232 connector with 12V. 
     Therefore, there is room for improvement in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present disclosure can be better understood with reference to the following drawing(s). The components in the drawing(s) are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawing(s), like reference numerals designate corresponding parts throughout the several views. 
         FIGS. 1 and 2  are circuit diagrams of an embodiment of an indication circuit of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  illustrate an embodiment of an indication circuit of the present disclosure. The indication circuit is used to indicate voltage values of a voltage acquired by a first recommended standard 232 (RS232) connector  10  from a second RS232 connector  20 . In one embodiment, the second RS232 connector  20  may couple to a computer, and the second RS232 connector may couple to other component. The indication circuit includes a Schottky diode D 1 , six resistors R 1 -R 6 , four transistors Q 1 -Q 4 , and two light-emitting diodes (LED) C 1  and C 2 . 
     The First RS232 connector  10  includes first to tenth pins  1 - 10 . The first pin  1  of the First RS232 connector  10  is idle. The ninth pin  9  of the First RS232 connector  10  is connected to ground. The second to eighth pins  2 - 8  and the tenth pin  10  of the First RS232 connector  10  are coupled to a pin COM_DCD, a pin COM_DSR, a pin COM_RXD, a pin COM_RTS, a pin COM_TXD, a pin COM_CTS, a pin COM_DTR, and a pin COM_RI of the second RS232 connector  20 , respectively. 
     Anodes A 1  and A 2  of the Schottky diode D 1  is coupled to the tenth pin  10  of the first RS232 connector  10 . A cathode C of the Schottky diode D 1  is connected to ground through the resistors R 1  and R 2  in that order, and is also coupled to a drain D of the transistor Q 1  through the resistor R 3 . A gate G of the transistor Q 1  is coupled to a node between the resistors R 1  and R 2 . Sources S of the transistors Q 1  and Q 2  are connected to ground. The drain D of the transistor Q 1  is coupled to a gate G of the transistor Q 2 . A drain D of the transistor Q 2  is coupled to a power terminal VCC 3  providing 3 voltages (V), through the resistor R 4 , and is also coupled to a drain D of the transistor Q 3 . A gate G of the transistor Q 3  is coupled to the cathode C of the Schottky diode D 1 . A source S of the transistor Q 3  is coupled to a cathode of the LED C 2 . An anode of the LED C 2  is coupled to the power terminal VCC 3  through the resistor R 6 . A gate G of the transistor Q 4  is coupled to the cathode C of the Schottky diode D 1 . A drain D of the transistor Q 4  is coupled to the drain D of the transistor Q 1 . A source S of the transistor Q 4  is coupled to a cathode of the LED C 1 . An anode of the LED C 1  is coupled to the power terminal VCC 3  through the resistor R 5 . 
     When the pin COM_RI of the second RS232 connector  20  provides 5V, the tenth pin  10  of the first RS232 connector  10  receives the 5V, so do the anodes A 1  and A 2  of the Schottky diode D 1 . The Schottky diode D 1  is turned on. Accordingly, the voltage of the gates G of the transistors Q 3  and Q 4  is at 5V. The voltage of the gate G of the transistor Q 1  is at 1.24V because of voltage division by the resistors R 1  and R 2 , thus, the transistor Q 1  is turned off, and the voltage of the drain D of the transistor Q 1  is at 5V. The voltage of the gate G of the transistor Q 2  is at 5V, so that the transistor Q 2  is turned on, and the drain D of the transistor Q 2  is at low-voltage level. The drain D of the transistor Q 3  is also at a low-voltage level. In the meanwhile, the voltage of the gate G of the transistor Q 3  is at 5V, to turn on the transistor Q 3 . Accordingly, the cathode of the LED C 2  is at a low-voltage level, which makes the LED C 2  emit light. The voltage of the gate G and the drain D of the transistor Q 4  is at 5V, so that the transistor Q 4  is turned on, and the voltage of the cathode of the LED C 1  is 5V. The LED C 1  will not emit light. 
     When the pin COM_RI of the second RS232 connector  20  provides 12V, the tenth pin  10  of the first RS232 connector  10  receives the 12V, so do the anodes A 1  and A 2  of the Schottky diode D 1 . The Schottky diode D 1  is turned on. Accordingly, the voltage of the gates G of the transistors Q 3  and Q 4  is at 12V. The voltage of the gate G of the transistor Q 1  is at 3V for the division voltage of the resistors R 1  and R 2 , thus, the transistor Q 1  is turned on, and the voltage of the drain D of the transistor Q 1  is at low-level voltage, such as logic 0. The voltage of the gate G of the transistor Q 2  is at low-level voltage, so that the transistor Q 2  is turned off, and the voltage of the drain D of the transistor Q 2  is 3V. The voltage of the drain D of the transistor Q 3  is also at 3V. In the meanwhile, the voltage of the gate G of the transistor Q 3  is at 12V, to turn on the transistor Q 3 . Accordingly, the voltage of the cathode of the LED C 2  is at 3V, which makes the LED C 2  not emit light. The voltage of the gate G of the transistor Q 4  is at 12V, and the drain D of the transistor Q 4  is connected to ground, so that the transistor Q 4  is turned on, and the voltage of cathode of the LED C 1  is at low-level voltage. The LED C 1  emits light. Therefore, when the second RS232 connector  20  provides 5V, the LED C 2  emits light, and the LED C 1  does not emit light. When the second RS232 connector  20  provides 12V, the LED C 1  emits light, and the LED C 2  does not emit light. 
     When the second RS232 connector  20  provides no power, the LEDs C 1  and C 2  do not emit light. 
     In the embodiment, the transistors Q 1 -Q 4  are n-channel metal oxide semiconductor transistors (NMOSFET). 
     While the disclosure has been described by way of example and in terms of preferred embodiment, it is to be understood that the disclosure is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the range of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.