Adaptive constant on-time switching regulator

• US 8,400,129 B2
• Filed: 10/21/2009
• Issued: 03/19/2013
• Est. Priority Date: 10/21/2008
• Status: Active Grant

• Current Assignee: Monolithic Power Systems Incorporated
• Original Assignee: Monolithic Power Systems Incorporated
• Inventors: Ouyang, Qian
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US12/603,455
• Publication Number:
  US 20100134080A1
• Time in Patent Office: 1,245 Days
• Field of Search: 323/222, 323/223, 323/225, 323/268, 323/271, 323282-286
• US Class Current: 323/283
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

The present invention provides an adaptive constant on-time switching regulator which comprises a switching circuit, a control circuit, and an output circuit. The control circuit controls the switches in the switching circuit to be turned on for an adaptive constant time, and be turned off for a minimum time.

Claims

1. An adaptive constant on-time switching regulator, comprising:

an input terminal operable to receive an input signal;

an output terminal operable to provide an output signal;

a switching circuit coupled to the input terminal;

an output circuit coupled between the switching circuit and the output terminal,

wherein the output circuit comprises;

an inductor coupled between the switching circuit and the output terminal;

an output capacitor coupled between the output terminal and ground;

and

a control circuit, coupled to the switching circuit, operable to control switches in the switching circuit to be turned on for an adaptive constant time, and be turned off for a minimum time, wherein the control circuit comprises;

an adaptive constant on-time control circuit, operable to receive a logical signal and a current sense signal representing the inductor current on the rising period part of the inductor current, the control circuit providing an adaptive constant on-time signal;

a feedback circuit, coupled to the output terminal, operable to receive the output signal and provide a feedback signal;

a minimum off-time control circuit, operable to receive the logical signal and provide a minimum off-time signal;

a logic circuit, coupled to the adaptive constant on-time control circuit, for receiving the adaptive constant on-time signal, the logic circuit coupled to the feedback circuit, for receiving the feedback signal, the logic circuit coupled to the minimum off-time control circuit, for receiving the minimum off-time signal, the logic circuit operable to provide the logical signal;

a reverse current compare circuit, operable to receive a signal representing the inductor current on the falling period part of the inductor current, and provide a reverse current indicating signal; and

a driver, coupled to the logic circuit, for receiving the logical signal;

the driver coupled to the reverse current compare circuit, for receiving the reverse current indicating signal;

the driver operable to provide a driving signal to the switching circuit to control the switches in the switching circuit to be turned on for an adaptive constant on time, and be turned off for a minimum off time.

2. The adaptive constant on-time switching regulator as set forth in claim 1, wherein the output circuit further comprises a current sense resistor coupled to the inductor in series.

3. The adaptive constant on-time switching regulator as set forth in claim 2, wherein the adaptive constant on-time control circuit further comprises:

a current sense amplifier, a first switch, a second switch, a first comparator, a first DC supply, and a first capacitor, wherein the two input terminals of the current sense amplifier are coupled across the current sense resistor, the output terminal of the current sense amplifier is coupled to the non-inverting input terminal of the first comparator via the first switch, the output terminal of the current sene amplifier is also coupled to the inverting input of the first comparator via the second switch and the first DC supply;

further wherein the first capacitor is coupled to the inverting input terminal of the first comparator via the first DC supply;

further wherein the control terminals of the first switch and said second switch are coupled together to the output terminal of said logic circuit for receiving the logical signal; and

further the first comparator provides the adaptive constant on-time signal at its output terminal.

4. The adaptive constant on-time switching regulator as set forth in claim 3, wherein the first switch and the second switch are turned on and off in complementary fashion.

5. The adaptive constant on-time switching regulator as set forth in claim 1, wherein the voltage feedback circuit comprises:

a divider, coupled between the output terminal and ground;

a second comparator, coupled to the divider at its inverting input terminal, operable to provide the feedback signal at its output terminal; and

a reference, coupled to the non-inverting input terminal of the second comparator.

6. The adaptive constant on-time switching regulator as set forth in claim 1, wherein the minimum off-time control circuit comprises:

a sawtooth generator, operable to receive the logical signal, and provide a sawtooth signal;

a third comparator, coupled to the sawtooth generator for receiving the sawtooth signal at its non-inverting input terminal, operable to provide the minimum off-time signal at its output terminal; and

a second DC supply, coupled to the inverting input terminal of the third comparator.

7. The adaptive constant on-time switching regulator as set forth in claim 1, wherein the logic circuit comprises:

an AND gate, coupled to the feedback circuit at one input terminal, for receiving the feedback signal;

coupled to the output of the minimum off-time control circuit at the other input terminal, for receiving the minimum off-time signal;

operable to provide an AND signal; and

a RS trigger, coupled to the adaptive constant on-time control circuit at its reset terminal, for receiving the adaptive constant on-time signal;

coupled to the AND gate, for receiving the AND signal at its set terminal;

operable to provide the logical signal at its output terminal.

8. The adaptive constant on-time switching regulator as set forth in claim 1, wherein the reverse current compare circuit comprises a fourth comparator.