Control circuit for step-down and boost type switching supply circuit and method for switching supply circuit

• US 8,638,082 B2
• Filed: 01/18/2011
• Issued: 01/28/2014
• Est. Priority Date: 01/19/2010
• Status: Active Grant

• Current Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Original Assignee: Spansion LLC (Infineon Technologies AG)
• Inventors: MIYAMAE, Toru
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): NASH, GARY A
• Application Number:
  US13/008,374
• Publication Number:
  US 20110175588A1
• Time in Patent Office: 1,106 Days
• Field of Search: 323/282, 323284-287
• US Class Current: 323/284
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence

Abstract

A control circuit for a switching supply, include: a first control circuit that selects one of a first signal to switch a boost mode and a step-down mode and a second signal to control an on-period of a switch based on an input voltage, the switch provided between a terminal to which the input voltage is applied and an inductor; and a second control circuit that controls the switching supply based on an output voltage and the selected one of the first signal and the second signal.

Claims

1. A control circuit for a switching supply, comprising:

a first control circuit that outputs a first signal to switch a boost mode and a step-down mode and a second signal to control an on-period of a switch based on an input voltage, the switch provided between a terminal to which the input voltage is applied and an inductor; and

a second control circuit that controls the switching supply based on an output voltage by performing a logical operation on the first signal and the second signal,

wherein the first control circuit includes;

a generation circuit that generates triangular wave;

a plurality of amplifiers that amplify a difference voltage between the input voltage and a reference voltage; and

a plurality of comparators, each of which compares an output of a respective amplifier of the plurality of amplifiers with an output of the generation circuit.

2. The control circuit according to claim 1, further comprising:

an element that detects a fluctuation of the output voltage and the input voltage, wherein the first control circuit selects one of the first signal and the second signal based on a reference voltage corresponding to a response speed of the element.

3. The control circuit according to claim 2, wherein the first control circuit selects the second signal when the input voltage is higher than the reference voltage.

4. The control circuit according to claim 1, further comprising:

an error signal generation circuit that outputs an error voltage in accordance with a difference between a reference voltage and a voltage in proportion to the output voltage; and

a pulse-width modulation (PWM) signal generation circuit that changes a duty of a control signal output from the second control circuit based on the error voltage.

5. The control circuit according to claim 1, wherein the switching supply includes a step-down and boost power supply.

6. A switching supply comprising:

a first switch provided between a first terminal of an inductor and an input terminal to which an input voltage is input;

a second switch provided between the first terminal of the inductor and a ground terminal;

a third switch provided between a second terminal of the inductor and the ground terminal;

a fourth switch provided between the second terminal of the inductor and an output terminal from which an output voltage is output; and

a control circuit that generates a control signal to control the first switch to the fourth switch, wherein the control circuit includes;

a first control circuit that outputs a first signal to switch a boost mode and a step-down mode and a second signal to control an on-period of a switch based on the input voltage, the switch provided between the inductor and a terminal to which the input voltage is applied; and

a second control circuit that controls the switching supply based on the output voltage by performing a logical operation on the first signal and the second signal,

wherein the first control circuit includes;

a generation circuit that generates triangular wave;

a plurality of amplifiers that amplify a difference voltage between the input voltage and a reference voltage; and

a plurality of comparators, each of which compares an output of a respective amplifier of the plurality of amplifiers with an output of the generation circuit.

7. The switching supply according to claim 6, wherein the switching supply includes a step-down and boost power supply.

8. A control method of a switching supply, the method comprising:

generating triangular wave signal;

amplifying a difference voltage between an input voltage and a reference voltage;

comparing an amplified difference voltage with the triangular wave signal to generate a first signal to switch a boost mode and a step-down mode and a second signal to control an on-period of a switch, the switch provided between an inductor and a terminal to which the input voltage is applied; and

controlling the switching supply based on an output voltage by performing a logical operation on the first signal and the second signal.

9. The control method according to claim 8, wherein the switching supply includes a step-down and boost power supply.