Control circuitry for controlling rotational speed of a DC motor

Abstract

A simple control circuitry is provided for controlling the rotational speed of a DC motor. The control circuitry includes a voltage reference component and a switching circuit for controlling the state of the voltage reference component. When the voltage of the DC motor and the voltage reference component is no higher than a predetermined voltage level of the voltage reference component, the switching circuit does not conduct, and the DC motor is accelerated according to a first operation mode. When the voltage of the DC motor and the voltage reference component is higher than a predetermined voltage level of the voltage reference component, the switching circuit conducts, and the DC motor is accelerated to a maximum speed according to a second operation mode.

What is claimed is:  
     
         1 . A simple control circuitry, electrically connected to a DC motor, to modulate and control the rotational speed of the DC motor. The control circuitry comprises of, but is not limited to: 
 an input node, which is connected with the input node of the DC motor to a variable voltage source;    a voltage reference component, which is electrically connected to the input node of the control circuitry, and provides a predetermined reference voltage; and    a switching circuit, electrically connected between the DC motor and the voltage reference component, controls the state of the voltage reference component. The switching circuit includes a ground node, and a connector node connected to the DC motor;    wherein when the voltage provided by the variable voltage source to the DC motor and the voltage reference component is no higher than a predetermined voltage level of the voltage reference component, the switching circuit does not conduct, and the DC motor is accelerated according to a first operation mode; when the voltage of the DC motor and the voltage reference component is higher than the predetermined voltage level of the voltage reference component, the switching circuit conducts, and the DC motor is accelerated to a maximum speed according to a second operation mode.    
     
     
         2 . Circuitry according to  claim 1 , characterized in that the second operation mode of the DC motor operates at a higher rotational speed than the first operation mode for a given voltage.  
     
     
         3 . Circuitry according to  claim 1 , characterized in that the voltage reference component is a Zener diode.  
     
     
         4 . Circuitry according to  claim 3 , wherein said voltage reference component further comprises a current limiting resistor which is connected between the input node of the control circuit and the Zener diode, used to reduce the current through the Zener diode as a protective measure to the Zener diode.  
     
     
         5 . Circuitry according to  claim 1 , wherein said switching circuit is an npn bipolar junction transistor (BJT), an N-type metal oxide semiconductor (NMOS) transistor, or a relay.  
     
     
         6 . Circuitry according to  claim 5 , wherein said switching circuit further comprises a voltage drop component connected in parallel with the switching circuit, providing a voltage drop across switching circuit.  
     
     
         7 . Circuitry according to  claim 6 , wherein said voltage drop component is a resistor or a Zener diode.  
     
     
         8 . A simple control circuitry, electrically connected to a DC motor, used to modulate and control the rotational speed of the DC motor. The control circuitry comprises, but is not limited to: 
 an input node, connected to a variable voltage source;    a ground node;    a first voltage drop component, which is electrically connected to the input node and develops a voltage drop when current generated from the variable voltage source flows through it;    a voltage reference component, which is electrically connected to the first voltage drop component at one node, and the ground at the other, and provides a predetermined reference voltage; and    a switching circuit, which is electrically connected between the input node and the DC motor, used to control the state of the voltage reference component, the switching circuit comprising of: 
 a connector node, connected between the first voltage drop component and the voltage reference component, used to control the state of the voltage reference component; and  
 a second voltage drop component, which is electrically connected between the input node of the control circuit and the DC motor, and provides a path for the current generated from the variable voltage source to the DC motor;  
   wherein when the voltage provided by the variable voltage source to the switching circuit and the voltage reference component is higher than the voltage across the first voltage drop component and no larger than the predetermined voltage of the voltage reference component, the switching circuit does not conduct, and the DC motor accelerates according to a first operation mode; when the voltage provided by the variable voltage source to the switching circuit and the voltage reference component is higher than the predetermined voltage of the voltage reference component, the switching circuit conducts, and the DC motor accelerates according to a second operation mode to a maximum speed.    
     
     
         9 . Circuitry according to  claim 8 , characterized in that the second operation mode of the DC motor operates at a higher rotational speed than the first operation mode for a given voltage.  
     
     
         10 . Circuitry according to  claim 8 , wherein said first voltage drop component is a resistor.  
     
     
         11 . Circuitry according to  claim 8 , characterized in that the voltage reference component is a Zener diode.  
     
     
         12 . Circuitry according to  claim 11 , wherein said voltage reference component further comprises a current limiting resistor which is connected between the input node of the control circuit and the Zener diode, used to reduce the current through the Zener diode as a protective measure to the Zener diode.  
     
     
         13 . Circuitry according to  claim 8 , wherein said switching circuit is a pnp BJT, a P-type metal oxide semiconductor (PMOS) transistor, or a relay.  
     
     
         14 . Circuitry according to  claim 13 , wherein said second voltage drop component is a resistor or a Zener diode.