Ac line powered relay driving circuits

Abstract

Disclosed are exemplary embodiments of relay drive circuits. In an exemplary embodiment, a relay drive circuit generally includes a first diode, a second diode, a third diode, a first transistor, a second transistor, a first capacitor, and a second capacitor. The relay drive circuit is operable to transform an AC voltage to a DC voltage, and then use the DC voltage to control on/off of the relay.

What is claimed is: 
     
         1 . A relay drive circuit comprising:
 a first diode having a positive pole and a negative pole;   a first capacitor having a positive pole and a negative pole;   a first transistor having a base, an emitter, and a collector; and   an integrated circuit configured to transform high voltage DC current into low voltage DC current, the integrated circuit including a first terminal, a second terminal, and a third terminal;   wherein:   the positive pole of the first diode is electrically connected to a positive terminal of an AC supply;   the negative pole of the first diode is electrically connected to the positive pole of the first capacitor;   the negative pole of the first capacitor is connected to a negative terminal of the AC supply;   the base of the first transistor is connected with a drive signal;   the collector of the first transistor is connected with a relay;   the emitter of the first transistor is connected to the negative pole of the first capacitor;   the first terminal of the integrated circuit is connected to the negative pole of the first diode and the positive pole of the first capacitor;   the second terminal of the integrated circuit is connected to the relay; and   the third terminal of the integrated circuit is connected to the negative pole of the first capacitor.   
     
     
         2 . The relay drive circuit of  claim 1 , wherein:
 the relay drive circuit further comprises a first resistor and a second resistor;   the first resistor is connected between the first diode and the first capacitor; and   the second resistor is connected between the base of the first transistor and the drive signal.   
     
     
         3 . The relay drive circuit of  claim 1 , wherein a model of the integrated circuit is VIPer12AS. 
     
     
         4 . The relay drive circuit of  claim 1 , wherein the base of the first transistor is connected with the drive signal such that, when the first transistor is switched on by the drive signal, the integrated circuit will provide a voltage that turns on the relay. 
     
     
         5 . An AC line powered relay driving circuit operable for using AC line voltage directly to provide power to drive a relay, the relay drive circuit comprising:
 a rectifying circuit electrically connected with an AC power supply to rectify high AC voltage into high DC voltage;   a DC voltage converting circuit electrically connected between the rectifying circuit and the relay, the DC voltage converting circuit operable to transform high DC voltage into low DC voltage; and   a capacitor in parallel with the relay such that voltage on the capacitor turns on the relay, wherein voltage on the capacitor is controllable by a duty cycle and frequency of a drive signal.   
     
     
         6 . The AC line powered relay driving circuit of  claim 5 , wherein:
 the relay drive circuit is configured to receive a pulse-width-modulation (PWM) input operable for providing a pulse-width modulated drive signal;   the rectifying circuit includes a first diode and a first capacitor; and   the DC voltage converting circuit includes a second diode, a third diode, a first transistor, a second transistor, a second capacitor, and is configured to receive the PWM input; and   the capacitor in parallel with the relay is a third capacitor.   
     
     
         7 . The AC line powered relay driving circuit of  claim 6 , wherein the PWM input is input to a base of the second transistor. 
     
     
         8 . The AC line powered relay driving circuit of  claim 6 , wherein:
 the first diode includes a positive pole and a negative pole;   the second diode includes a positive pole and a negative pole; and   the third diode includes a positive pole and a negative pole;   the first transistor includes a base, an emitter, and a collector;   the second transistor includes a base, an emitter, and a collector;   the first capacitor includes a positive pole and a negative pole;   the positive pole of the first diode is electrically connected to a positive terminal of the AC power supply; and   the negative pole of the first diode is electrically connected to the positive pole of the first capacitor.   
     
     
         9 . The AC line powered relay driving circuit of  claim 6 , wherein the first capacitor is configured to charge the second capacitor when the PWM input is low. 
     
     
         10 . The AC line powered relay driving circuit of  claim 6 , wherein the second capacitor is configured to charge the third capacitor when the PWM input is high. 
     
     
         11 . A method of using AC line voltage directly to provide power to drive a relay, the method comprising:
 rectifying high AC voltage into high DC voltage;   transforming high DC voltage into low DC voltage; and   controlling a charge on a capacitor in parallel with the relay by a duty cycle and frequency of a drive signal, whereby low DC voltage on the capacitor in parallel with the relay turns on the relay.   
     
     
         12 . The method of  claim 11 , wherein:
 rectifying high AC voltage into high DC voltage comprises regulating AC line voltage into a first diode and a first capacitor; and   transforming high DC voltage into low DC voltage comprises using a second diode, a third diode, a first transistor, a second transistor, a second capacitor, and a drive signal input.   
     
     
         13 . The method of  claim 12 , further comprising receiving the drive signal through a base of the second transistor. 
     
     
         14 . The method of  claim 12 , further comprising:
 charging the second capacitor from the first capacitor when the drive signal is low; and   charging the capacitor in parallel with the relay from the second capacitor when the drive signal is high.   
     
     
         15 . The method of  claim 11 , wherein the low DC voltage on the capacitor is 24 VDC.