SWITCHING REGULATOR AND METHOD FOR CONTROLLING OPERATION THEREOF

• US 20100181977A1
• Filed: 06/17/2008
• Published: 07/22/2010
• Est. Priority Date: 07/27/2007
• Status: Active Grant

• Current Assignee: Nisshinbo Micro Devices Incorporated
• Original Assignee: Ricoh Company Limited
• Inventors: Sohma, Shohtaroh
• Granted Patent: US 8,207,721 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

A disclosed switching regulator includes: a switching element switching in accordance with an input control signal; an inductor charged with a supply voltage by the switching of the switching element; a rectifying element discharging the inductor when the switching element is switched off and charging of the inductor is stopped; and a control circuit unit generating an error voltage based on a voltage difference between a proportional voltage and a predetermined reference voltage, generating and outputting a pulse signal with a duty cycle in accordance with the error voltage to a control electrode of the switching element. The control circuit unit generates a feedback voltage from the duty cycle of the pulse signal, generates the pulse signal with the duty cycle from a voltage difference between the generated feedback voltage and the error voltage, and varies the voltage difference from the duty cycle of the pulse signal.

Claims

1. A switching regulator for converting a supply voltage input to an input terminal into a predetermined constant voltage and outputting the predetermined constant voltage as an output voltage from an output terminal, comprising:

a switching element performing switching in accordance with an input control signal;

an inductor charged with the supply voltage by the switching of said switching element;

a rectifying element discharging said inductor when said switching element is switched off and charging of said inductor is stopped; and

a control circuit unit generating an error voltage based on a difference of voltage between a proportional voltage proportionate to the output voltage and a predetermined reference voltage, generating a pulse signal with a duty cycle in accordance with the error voltage, and outputting the pulse signal to a control electrode of said switching element so as to perform switching control of said switching element, wherein

said control circuit unit generates a feedback voltage in accordance with the duty cycle of the pulse signal, generates the pulse signal with the duty cycle based on a difference of voltage between the generated feedback voltage and the error voltage, and varies the difference of voltage in accordance with the duty cycle of the pulse signal, thereby performing feedback control.

2. The switching regulator according to claim 1, wherein

said control circuit unit compares the error voltage with the feedback voltage and generates the pulse signal with a duty cycle based on a result of the comparison.

3. The switching regulator according to claim 2, wherein

said control circuit unit includes:

an error voltage generating circuit unit generating and outputting the error voltage based on the difference of voltage between the proportional voltage proportionate to the output voltage and the predetermined reference voltage;

a pulse modulating circuit unit generating the pulse signal with the duty cycle in accordance with the error voltage and outputting the pulse signal to the control electrode of said switching element so as to perform switching control of said switching element; and

a feedback circuit unit generating and outputting the feedback voltage in accordance with the duty cycle of the pulse signal, wherein

said pulse modulating circuit unit compares the error voltage with the feedback voltage and generates the pulse signal with a duty cycle based on a result of the comparison.

4. The switching regulator according to claim 3, wherein

said feedback circuit unit generates the feedback voltage by integrating the pulse signal.

5. The switching regulator according to claim 4, wherein

said feedback circuit unit includes:

a first switch performing switching in accordance with the pulse signal;

a second switch performing switching opposite to the switching of said first switch in accordance with the pulse signal;

a capacitor;

a constant current source performing charging by supplying a predetermined constant current to said capacitor in accordance with the switching of said first switch; and

a resistor forming a predetermined time constant when said capacitor is discharged in accordance with the switching of said second switch.

6. The switching regulator according to claim 3, wherein

said feedback circuit unit integrates the pulse signal and adds a slope voltage having a voltage tilt in accordance with the duty cycle of the pulse signal to a signal with ripple obtained by the integration so as to generate the feedback voltage.

7. The switching regulator according to claim 6, wherein

said feedback circuit unit includes:

a first switch performing switching in accordance with the pulse signal;

a second switch performing switching opposite to the switching of said first switch in accordance with the pulse signal;

a capacitor;

a constant current source performing charging by supplying a predetermined constant current to said capacitor in accordance with the switching of said first switch;

a resistor forming a predetermined time constant when said capacitor is discharged in accordance with the switching of said second switch; and

a slope voltage generating circuit generating the slope voltage and adding the generated slope voltage to a voltage of a charging and discharging terminal of said capacitor at a time of charging so as to generate the feedback voltage.

8. The switching regulator according to claim 6, wherein

said feedback circuit unit includes:

a first switch performing switching in accordance with the pulse signal;

a second switch performing switching opposite to the switching of said first switch in accordance with the pulse signal;

a resistor;

a capacitor supplied with a current to be charged via said resistor in accordance with the switching of said first switch;

a constant current source discharging said capacitor in accordance with the switching of said second switch; and

a slope voltage generating circuit generating the slope voltage and adding the generated slope voltage to a voltage of a charging and discharging terminal of said capacitor at a time of charging so as to generate the feedback voltage.

9. The switching regulator according to claim 3, wherein

said error voltage generating circuit unit includes:

an output voltage detecting circuit dividing the output voltage and generating and outputting the proportional voltage;

a reference voltage generating circuit generating and outputting the reference voltage; and

an error amplifying circuit amplifying the difference of voltage between the proportional voltage and the reference voltage and generating and outputting the error voltage.

10. The switching regulator according to claim 3, wherein

said pulse modulating circuit unit includes:

a voltage comparison circuit comparing the error voltage with the feedback voltage and generating and outputting a binary signal indicating a result of the comparison; and

an RS flip-flop circuit receiving a predetermined clock signal at one input terminal and an output signal of said voltage comparison circuit at the other input terminal and generating and outputting the pulse signal based on each signal level of the output signal and the clock signal.

11. A method for controlling operation of a switching regulator including:

a switching element performing switching in accordance with an input control signal;

an inductor charged with an input voltage input to an input terminal by the switching of said switching element; and

a rectifying element discharging said inductor when said switching element is switched off and charging of said inductor is stopped,

said method comprising;

generating an error voltage based on a difference of voltage between a proportional voltage proportionate to an output voltage output from an output terminal and a predetermined reference voltage;

generating a pulse signal with a duty cycle in accordance with the error voltage and outputting the pulse signal to a control electrode of said switching element so as to perform switching control of said switching element;

converting the input voltage input to said input terminal into a predetermined constant voltage and outputting the predetermined constant voltage as the output voltage;

generating a feedback voltage in accordance with the duty cycle of the pulse signal;

generating the pulse signal with the duty cycle based on a difference of voltage between the generated feedback voltage and the error voltage; and

varying the difference of voltage in accordance with the duty cycle of the pulse signal, thereby performing feedback control.

12. The method for controlling operation of a switching regulator according to claim 11, wherein

the error voltage is compared with the feedback voltage, and

the pulse signal with the duty cycle is generated based on a result of the comparison.

13. The method for controlling operation of a switching regulator according to claim 11, wherein

the feedback voltage is generated by integrating the pulse signal.

14. The method for controlling operation of a switching regulator according to claim 11, wherein

the pulse signal is integrated and a slope voltage having a voltage tilt in accordance with the duty cycle of the pulse signal is added to a signal with ripple obtained by the integration so as to generate the feedback voltage.