SWITCHING REGULATOR AND SEMICONDUCTOR APPARATUS INCLUDING THE SAME

• US 20090322298A1
• Filed: 06/22/2009
• Published: 12/31/2009
• Est. Priority Date: 06/26/2008
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: NISHIDA, Junji
• Granted Patent: US 8,258,765 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A switching regulator is disclosed that includes a switching element; an inductor; a rectifier element; an error amplifier circuit portion; a PWM pulse generating circuit portion; a current sensing circuit portion; an output voltage decrease detecting circuit portion; a current pulse generating circuit portion; a phase detecting circuit portion; a VFM pulse generating circuit portion; and a switching control circuit portion configured to generate a control signal based on a PWM signal or a VFM signal and to switch a control status of the switching element from a PWM control to a VFM control in accordance with a third signal output from the phase detecting circuit portion, and to switch the control status from the VFM control to the PWM control in accordance with a second signal output from the output voltage decrease detecting circuit portion.

Claims

1. A switching regulator configured to switch a control status of a switching element between a PWM control and a VFM control, and to convert an input voltage input to an input terminal into a predetermined constant voltage and output the predetermined constant voltage from an output terminal as an output voltage, the switching regulator comprising:

the switching element configured to be switched in accordance with a control signal;

an inductor configured to be supplied with current from the switching element;

a rectifier element configured to carry current supplied from the inductor when the switching element is turned off;

an error amplifier circuit portion configured to compare a proportion voltage proportional to the output voltage and a first reference voltage, and to output a first signal indicating a comparison result of the proportion voltage and the first reference voltage and generate an error voltage by amplifying a voltage difference between the proportion voltage and the first reference voltage;

a PWM pulse generating circuit portion configured to generate a PWM signal used for performing the PWM control by modulating the error voltage;

a current sensing circuit portion configured to sense a high side current flowing through the switching element and a low side current flowing through the rectifier element, and to output a signal indicating a sensing result of the high side current and a signal indicating a sensing result of the low side current;

an output voltage decrease detecting circuit portion configured to output a second signal when detecting that the output voltage becomes less than or equal to a predetermined voltage;

a current pulse generating circuit portion configured to generate a current pulse signal having a pulse width from a time point when the switching element is turned on to a time point when the high side current reaches a predetermined current value;

a phase detecting circuit portion configured to compare a phase of the PWM signal and a phase of the current pulse signal, and to output a third signal indicating a comparison result of the phase of the PWM signal and the phase of the current pulse signal;

a VFM pulse generating circuit portion configured to generate a VFM signal used for the VFM control based on the signal indicating a sensing result of the high side current and the signal indicating a sensing result of the low side current output from the current sensing circuit portion; and

a switching control circuit portion configured to generate the control signal based on the PWM signal or the VFM signal and to switch the control status of the switching element from the PWM control to the VFM control in accordance with the third signal output from the phase detecting circuit portion, and to switch the control status from the VFM control to the PWM control in accordance with the second signal output from the output voltage decrease detecting circuit portion.

2. The switching regulator as claimed in claim 1, wherein the switching control circuit portion switches the control status from the PWM control to the VFM control when the signal indicating that the phase of the PWM signal and the phase of the current pulse signal match each other, and switches the control status from the VFM control to the PWM control when the second signal is input from output voltage decrease detecting circuit portion.

3. The switching regulator as claimed in claim 1, wherein the current sensing circuit portion outputs a fourth signal when detecting that the high side current becomes larger than or equal to a first current value, in a case where the switching control circuit portion performs the PWM control.

4. The switching regulator as claimed in claim 1, wherein the current sensing circuit portion outputs a fourth signal when detecting that the high side current becomes larger than or equal to a second current value, and outputs a fifth signal when detecting that the low side current becomes smaller than or equal to a third current value in a case where the switching control circuit portion performs the VFM control, and wherein the third current value is smaller than the second current value.

5. The switching regulator as claimed in claim 4, wherein the VFM pulse generating circuit portion generates the VFM signal so that the switching element is turned on and becomes conduction state during a time period from a time point when the fifth signal is output from the current sensing circuit portion to a time point when the fourth signal is output from the current sensing circuit portion, when the first signal indicating the comparison result indicates that the proportion voltage is less than or equal to the first reference voltage is output from the error amplifier circuit portion.

6. The switching regulator as claimed in claim 5, wherein the VFM pulse generating circuit portion generates the VFM signal so that the switching element is turned on and becomes in a conduction state during a period from a time point when the first signal indicating the comparison result indicates that the proportion voltage becomes less than or equal to the first reference voltage is output from the error amplifier circuit portion to a time point when the fourth signal is output from the current sensing circuit portion, if the fifth signal is not output from the current sensing circuit portion, when the first signal indicating that the proportion voltage becomes less than or equal to the first reference voltage is output from the error amplifier circuit portion.

7. The switching regulator as claimed in claim 1, wherein the current pulse generating circuit portion generates the current pulse signal having a pulse width from a time point when the switching element is turned on by the switching control circuit portion and becomes in a conduction state at the earlier of a time point when the fourth signal is output from the current sensing circuit portion and a time point when the switching element is turned off and becomes in a cut-off status.

8. A semiconductor apparatus including the switching regulator as claimed in claim 1.

9. A switching regulator configured to switch a control status of a switching element between a PWM control and a VFM control, and to convert an input voltage input to an input terminal into a predetermined constant voltage and output the predetermined constant voltage from an output terminal as an output voltage, the switching regulator comprising:

an output voltage decrease detecting circuit portion configured to output a signal when detecting that the output voltage becomes less than or equal to a predetermined voltage; and

a switching control circuit portion configured to switch the control status from the VFM control to the PWM control in accordance with the signal output from the output voltage decrease detecting circuit portion.

10. A switching regulator configured to switch a control status of a switching element between a PWM control and a VFM control, and to convert an input voltage input to an input terminal into a predetermined constant voltage and output the predetermined constant voltage from an output terminal as an output voltage, the switching regulator comprising:

the switching element configured to be switched in accordance with a control signal;

an inductor configured to be supplied with current from the switching element;

a rectifier element configured to carry current supplied from the inductor when the switching element is turned off;

an error amplifier circuit portion configured to compare a proportion voltage proportional to the output voltage and a first reference voltage, and to output a first signal indicating a comparison result of the proportion voltage and the first reference voltage and generate an error voltage by amplifying a voltage difference between the proportion voltage and the first reference voltage;

a PWM pulse generating circuit portion configured to generate a PWM signal used for performing the PWM control by modulating the error voltage;

a current sensing circuit portion configured to sense a high side current flowing through the switching element and a low side current flowing through the rectifier element, and to output a signal indicating a sensing result of the high side current and a signal indicating a sensing result of the low side current;

a current pulse generating circuit portion configured to generate a current pulse signal having a pulse width from a time point when the switching element is turned on to a time point when the high side current reaches a predetermined current value;

a phase detecting circuit portion configured to compare a phase of the PWM signal and a phase of the current pulse signal, and to output a third signal indicating a comparison result of the phase of the PWM signal and the phase of the current pulse signal; and

a switching control circuit portion configured to generate the control signal based on the PWM signal or the VFM signal and to switch the control status of the switching element from the PWM control to the VFM control in accordance with the third signal output from the phase detecting circuit portion.