Synchronous buck DC/DC converter to perform an improved switching operation by adjusting variable resistor

Abstract

A synchronous buck DC/DC converter to perform an improved switching operation by adjusting a variable resistor is provided. The synchronous buck DC/DC converter includes a switching unit for switching two PWM signals inverted with a dead time and outputting the PWM signals, a smoothing circuit for outputting DC power using a waveform output from the switching unit as an input, a variable resistor connected to the switching unit and adjusting a switching time of the waveform output from the switching unit, and a variable resistor controller for sensing a current from an output terminal of the smoothing circuit and setting the resistance of the variable resistor to a resistance corresponding to the sensed current.

What is claimed is: 
     
       1. A DC/DC converter comprising:
 a switching unit to output a waveform having a first rising time according to a plurality of PWM signals corresponding to a plurality of power sources; 
 a smoothing circuit to output a DC power according to the waveform output from the switching unit; 
 a variable resistor connected to the switching unit to adjust a switching time of the waveform output from the switching unit and to adjust one of the plurality of power sources supplied to the switching unit; and 
 a variable resistor controller to sense a load current from an output terminal of the smoothing circuit and to set a resistance of the variable resistor according to the sensed current so that the switching unit generates an adjusted switching time according to the adjusted one of plurality of power sources, 
 wherein the smoothing circuit outputs another waveform having a second rising time according to the set resistance of the variable resistor and according to the adjusted switching time of the waveform output from the switching unit. 
 
     
     
       2. The DC/DC converter of  claim 1 , wherein the switching unit comprises:
 a switching circuit having a pair of field effect transistors (FETs) to output a square wave having a predetermined period as the waveform by a switching operation; and 
 a switching controller to control the switching operation of the switching circuit. 
 
     
     
       3. The DC/DC converter of  claim 1 , wherein the variable resistor controller comprises:
 an output sensing unit to sense the load current from the output terminal of the smoothing circuit; and 
 a variable resistor determining unit to determine a predetermined resistance corresponding to the sensed load current; and 
 a variable resistor adjusting unit to sent set the resistance of the variable resistor to the determined resistance. 
 
     
     
       4. The DC/DC converter of  claim 3 , wherein the variable resistor determining unit determines the resistance to be proportional to the sensed load current. 
     
     
       5. The DC/DC converter of  claim 3 , wherein the variable resistor determining unit determines the resistance corresponding to a predetermined range of the sensed load current. 
     
     
       6. The DC/DC converter of  claim 3 , wherein the variable resistor controlling unit further comprises:
 a storing unit to store information about the load current sensed by the output sensing unit and a the resistance corresponding to the load current. 
 
     
     
       7. The DC/DC converter of  claim 1 , further comprising:
 a bootstrap circuit connected to the switching circuit to provide power to drive the switching circuit. 
 
     
     
       8. The DC/DC converter of  claim 1 , wherein the variable resistor comprises:
 at least one of passive elements, active elements, and a combination of the passive and active elements. 
 
     
     
       9. The DC/DC converter of  claim 1 , wherein the DC/DC converter comprises a synchronous buck DC/DC converter. 
     
     
       10. A DC/DC converter comprising:
 a switching controller to generate a switching signal according to a first power source; 
 a switching circuit to output a waveform according to the switching signal and a second power source; 
 a smoothing circuit to output a DC power according to the waveform output from the switching circuit; 
 a variable resistor connected between the switching controller and the first power source to adjust the first power source supplied to the switching controller; and 
 a variable resistor controller to sense a load current of the smoothing circuit and to change a resistance of the variable resistor to generate the adjusted first power source according to the sensed load current, so that the switching controller generates a modified switching signal according to the adjusted first power source, the switching circuit outputs a second waveform according to the modified switching signal, and the smoothing circuit outputs a second DC Power according to the second waveform. 
 
     
     
       11. The DC/DC converter of  claim 10 , further comprising:
 a bootstrap circuit -disposed between the first power source and the switching controller to supply a voltage to the switching controller, 
 wherein the switching controller generates the switching signal according to the voltage. 
 
     
     
       12. The DC/DC converter of  claim 11 , wherein the variable resistor is disposed between the bootstrap circuit and the switching controller. 
     
     
       13. The DC/DC converter of  claim 11 , wherein the switching circuit comprises an output terminal to output the waveform, and the bootstrap circuit comprises a capacitor connected between the first power source and the output terminal of the switching circuit. 
     
     
       14. The DC/DC converter of  claim 10 , wherein:
 the load current comprises a first load current and a second load current; and 
 the waveform comprises a first waveform having a first rising time and a first peak voltage in the first rising time, and a second waveform having a second rising time and a second peak voltage in the second rising time, in response to the first load current and the second load current, respectively. 
 
     
     
       15. The DC/DC. converter of  claim 10 , wherein a first peak voltage and a second peak voltage are same. 
     
     
       16. The DC/DC converter of  claim 10 , wherein the waveform comprises a first waveform and a second waveform having a first period and a second period, the first and second periods being identical. 
     
     
       17. The DC/DC converter of  claim 10 , wherein:
 the load current comprises a first load current and a second load current; 
 the resistance of the variable resistor comprises a first resistance and a second resistance according to the first and second load currents, respectively; and 
 the waveform comprises a first waveform having a first rising time and a first peak voltage in the first rising time, and a second waveform having a second rising time and a second peak voltage in the second rising time, according to the first resistance and the second resistance, respectively. 
 
     
     
       18. A DC/DC converter comprising:
 a switching controller to generate a switching signal according to a first power source; 
 a switching circuit to output a first waveform having a first risina time according to the switching signal and a second power source; 
 a smoothing circuit to output a DC power according to the first waveform output from the switching circuit; and 
 a controller to detect a characteristic of the smoothing circuit with respect to the output DC power and to control the switching circuit according to the characteristic of the smoothing circuit to output the first waveform having the first rising time and a first peak voltage in the first rising time, and a second waveform having a second rising time and a second peak voltage in the second rising time, as the waveform and the controller to generate a modified switching signal when the first power source that supplies the switching controller is adjusted, 
 wherein the smoothing circuit outputs another DC power according to the second waveform and according to the control of the switching circuit by the controller. 
 
     
     
       19. The DC/DC converter of  claim 18 , further comprising:
 a bootstrap circuit connected between the first power source and the switching controller to supply a voltage to the switching controller; and 
 a variable resistor disposed between the bootstrap circuit and the switching controller to adjust the voltage according to the detected characteristic of the smoothing circuit. 
 
     
     
       20. The DC/DC converter of  claim 18 , wherein the characteristic of the smoothing circuit comprises a load current. 
     
     
       21. The DC/DC converter of  claim 18 , wherein a first peak voltage and a second peak voltage are substantially same. 
     
     
       22. A DC/DC converter comprising:
 a variable resistor;   a switching unit coupled to the variable resistor to output a first waveform having a first rising time according to (i) a plurality of PWM signals corresponding to a plurality of power sources and (ii) a first resistance value provided by the variable resistor; and   a smoothing circuit to output a DC power according to the first waveform output from the switching unit,   wherein a resistance of the variable resistor coupled to the switching unit is changeable to adjust a switching time of the first waveform output from the switching unit and to adjust the at least one power source of the plurality of power sources,   wherein the switching unit outputs a second waveform having a second rising time when the resistance of the variable resistor is changed from the first resistance value to a second resistance value and according to the adjusted switching time of the first waveform output from the switching unit.   
     
     
       23. The DC/DC converter of claim 22, wherein the variable resistor controller is configured to sense a load current from an output terminal of the smoothing circuit and to set a resistance of the variable resistor according to the sensed current. 
     
     
       24. The DC/DC converter of claim 22, wherein the switching unit comprises:
 a switching circuit having a pair of field effect transistors (FETs) to output a square wave having a predetermined period as the first waveform or the second waveform by a switching operation; and   a switching controller to control the switching operation of the switching circuit.   
     
     
       25. The DC/DC converter of claim 22, wherein the variable resistor controller comprises:
 an output sensing unit to sense the load current from the output terminal of the smoothing circuit; and   a variable resistor determining unit to determine a predetermined resistance corresponding to the sensed load current; and   a variable resistor adjusting unit to sent the resistance of the variable resistor to the determined resistance.   
     
     
       26. The DC/DC converter of claim 25, wherein the variable resistor determining unit determines the resistance to be proportional to the sensed load current. 
     
     
       27. The DC/DC converter of claim 25, wherein the variable resistor determining unit determines the resistance corresponding to a predetermined range of the sensed load current. 
     
     
       28. The DC/DC converter of claim 25, wherein the variable resistor controlling unit further comprises:
 a storing unit to store information about the load current sensed by the output sensing unit and the resistance corresponding to the load current.   
     
     
       29. The DC/DC converter of claim 22, further comprising:
 a bootstrap circuit connected to the switching circuit to provide power to drive the switching circuit.   
     
     
       30. The DC/DC converter of claim 22, wherein the variable resistor comprises:
 at least one of passive elements, active elements, and a combination of the passive and active elements.   
     
     
       31. The DC/DC converter of claim 22, wherein the DC/DC converter comprises a synchronous buck DC/DC converter.