DC-DC converter

Abstract

A DC-DC converter having a coupling network is provided, in which the coupling network is so configured as to forcibly add a noise source to a feedback output voltage of the DC-DC converter. The coupling network includes one coupling resistor and two coupling capacitors to include the switching voltage of a power switch and inductor output voltage into the output voltage, and transmit the result together with the feedback output voltage to the comparator. Accordingly, it is easier to compare the reference voltage and the feedback voltage, and stably maintain the output voltage of the DC-DC converter operating in constant on-time (COT).

What is claimed is: 
     
       1. A DC-DC converter, comprising:
 a comparator configured to compare a reference voltage to a feedback voltage; 
 a constant on-time (COT) generator configured to output an on-time signal of a power switch, in response to a result of the comparison at of the comparator; 
 a first switch and a second switch each configured to turn on for a predetermined time interval, according to based on the on-time signal; 
 an inductor connected in series to a common terminal of the first and second switches; 
 a first feedback resistor and a second feedback resistor connected between the inductor and a load resistor; and 
 a coupling network comprising a coupling resistor and a first coupling capacitor directly connected to an output end of the inductor, the coupling network configured to receive the on-time signal a switching output voltage through the coupling resistor and a feedback output voltage of the inductor, sum the received voltages, and output the result of summing as and output a first feedback voltage summing the received switching output voltage and the feedback output voltage, 
 wherein the first feedback voltage and a second feedback voltage outputted via, output by the first feedback resistor and the second feedback resistor, are directly provided as the feedback voltage of the comparator, and 
 wherein the coupling network further comprises a second coupling capacitor connected in parallel to the coupling resistor and the first coupling capacitor, and configured to output the first feedback voltage. 
 
     
     
       2. The DC-DC converter of  claim 1 , wherein the coupling network further comprises:
 the coupling resistor connected to the common terminal;   a first coupling capacitor connected to an output end of the inductor; and   a second coupling capacitor that is connected in parallel to the coupling resistor and the first coupling capacitor and that is configured to output the first feedback voltage.   
     
     
       3. The DC-DC converter of  claim 1 , wherein the first feedback voltage comprises an AC voltage of the output voltage of switching voltages of the first switch, switching voltages of the second switch and the inductor the switching output voltage of the first and second switches and the feedback output voltage of the inductor. 
     
     
       4. The DC-DC converter of  claim 1 , wherein the second feedback voltage comprises a DC voltage of an output voltage of an output end of the converter. 
     
     
       5. The DC-DC converter of  claim 1 , wherein the first and second switches are complementary MOS transistors. 
     
     
       6. The DC-DC converter of claim  5  1, wherein, in response to the first switch being PMOS, the second switch is NMOS, or in response to the first switch being NMOS, the second switch is PMOS:
 the first switch is a PMOS transistor and the second switch is an NMOS transistor; or 
 the first switch is a NMOS transistor and the second switch is a PMOS transistor. 
 
     
     
       7. The DC-DC converter of  claim 1 , wherein the first feedback voltage and the second feedback voltage are supplied to the comparator, in response to electric current  - flowing through the inductor. 
     
     
       8. The DC-DC converter of  claim 1 , wherein the DC-DC converter is configured to operate in continuous-current-mode (CCM) or discontinuous-current-mode (DCM). 
     
     
       9. A DC-DC converter, comprising:
 a comparator configured to compare a reference voltage to a feedback voltage; 
 a constant on-time (COT) generator configured to output an on-time signal of a power switch, in response to a result of the comparison at of the comparator; 
 a first switch and a second switch each configured to turn on for a predetermined time interval, according to based on the on-time signal; 
 an inductor connected in series to a common terminal of the first and second switches; 
 a first feedback resistor and a second feedback resistor connected between the inductor and a load resistor; and 
 a coupling resistor connected to an output pin of the COT generator, a first coupling capacitor directly connected to an output end of the inductor, and a second coupling capacitor connected in parallel to the coupling resistor and the first coupling capacitor to output the a first feedback voltage, 
 wherein the first feedback voltage and a second feedback voltage outputted via, output by the first feedback resistor and the second feedback resistor, are directly provided as the feedback voltage of the comparator. 
 
     
     
       10. The DC-DC converter of  claim 9 , further comprising a third switch between the output pin of the COT generator and the coupling resistor to select between a continuous current mode (CCM) and a discontinuous current mode (DCM) according to based on an electric current flowing through the inductor. 
     
     
       11. The DC-DC converter of  claim 9 , wherein the first feedback voltage comprises a DC an AC voltage of the an output voltage, and the second feedback voltage comprises an AC a DC voltage of the output voltage. 
     
     
       12. The DC-DC converter of  claim 10 , wherein the first and second switches are complementary MOS transistors, and in response to the first switch being PMOS, the second switch is NMOS, or in response to the first switch being NMOS, the second switch is PMOS wherein:
 the first switch is a PMOS transistor and the second switch is an NMOS transistor; or 
 the first switch is a NMOS transistor and the second switch is a PMOS transistor. 
 
     
     
       13. The DC-DC converter of  claim 12 , wherein the converter is configured to operate in the CCM until a current slope of the inductor becomes zero. 
     
     
       14. The DC-DC converter of  claim 12 , wherein the converter is configured to operate in the DCM when a current slope of the inductor has a negative value. 
     
     
       15. The DC-DC converter of  claim 14 , wherein the second switch is turned off and the first switch is turned on at a time point when the current slope of the inductor becomes a negative value. 
     
     
       16. The DC-DC converter of  claim 15 , wherein the second switch is the NMOS transistor and the first switch is the PMOS transistor. 
     
     
       17. A coupling network configured to receive switching voltages of a first switch and a second switch and a feedback output voltage of an inductor, sum the received switching voltages, and output the result of summing as a first feedback voltage, wherein the coupling network comprises comprising:
 a coupling resistorthe inductor connected to a common terminal of the first and second switches, wherein the inductor is connected in series to the common terminal; 
 a first coupling capacitor directly connected to an output end of the inductor; and 
 a second coupling capacitor that is, connected in parallel to the a coupling resistor and the first coupling capacitor and that is, configured to output the first feedback voltage, 
 wherein the first switch and the second switch are configured to turn on for a predetermined time interval, according to based on an on-time signal of a power switch generated by a constant on-time (COT) generator, and 
 wherein the coupling resistor is further connected to an output of the COT generator. 
 
     
     
       18. The coupling network of  claim 17 , wherein the first feedback voltage comprises an AC voltage of the output voltage of the switching voltages and the inductor. 
     
     
       19. The coupling network of  claim 17 , wherein the COT generator generates the on-time signal of the power switch in response to a result of a comparison at of a comparator that is configured to compare a reference voltage to a feedback voltage. 
     
     
       20. The coupling network of  claim 19 , wherein the first feedback voltage and a second feedback voltage outputted via the a feedback resistor are directly provided as the feedback voltage of the comparator. 
     
     
       21. A DC-DC converter configured to operate in continuous-current-mode (CCM) or discontinuous-current-mode (DCM), the DC-DC converter comprising the coupling network of  claim 17 . 
     
     
       22. A coupling network, the coupling network comprising:
 a coupling resistor provided with an on-time signaling, for a first switch and a second switch, based on an output of a constant on-time (COT) generator;   a first coupling capacitor directly connected to an output end of an inductor that is connected in series to a terminal of the first switch and the second switch, the first coupling capacitor being configured to output a feedback output voltage; and   a second coupling capacitor that is connected in parallel to the coupling resistor and the first coupling capacitor, the second coupling capacitor being configured to output a first feedback voltage summing a voltage of the coupling resistor and the feedback output voltage,   wherein the first switch and the second switch are configured to turn on for a predetermined time interval according to the on-time signaling.    
     
     
       23. The coupling network of claim 22, wherein the first feedback voltage comprises an AC voltage of an output voltage of switching voltages of the first and second switches and the inductor.  
     
     
       24. The coupling network of claim 22, wherein the COT generator generates the on-time signaling based on a result of a comparison at a comparator that is configured to compare a reference voltage to a feedback voltage.  
     
     
       25. The coupling network of claim 24, wherein the first feedback voltage and a second feedback voltage, outputted via a feedback resistor, are directly provided as the feedback voltage of the comparator.  
     
     
       26. A DC-DC converter configured to operate in continuous-current-mode (CCM) or discontinuous-current-mode (DCM), the DC-DC converter comprising the coupling network of claim 22.   
     
     
       27. The DC-DC converter of claim 26, wherein the coupling resistor connects to an output of the COT generator through a third switch.  
     
     
       28. The DC-DC converter of claim 27, wherein the third switch is connected between an output pin of the COT generator and the coupling resistor to select between the CCM or the DCM according to an electric current flowing through the inductor.