Pulse width modulation controller of DC-DC converter

• US 8,624,574 B2
• Filed: 02/05/2013
• Issued: 01/07/2014
• Est. Priority Date: 08/05/2009
• Status: Active Grant

• Current Assignee: uPI Semiconductor Corporation (ASUSTek Computer, Inc.)
• Original Assignee: uPI Semiconductor Corporation (ASUSTek Computer, Inc.)
• Inventors: Chien, Min-Chu, Huang, Yung-Peng
• Primary Examiner(s): Behm, Harry
• Assistant Examiner(s): Grubb, Matthew
• Application Number:
  US13/759,640
• Publication Number:
  US 20130147456A1
• Time in Patent Office: 336 Days
• Field of Search: 323/282, 323/284, 323/285, 323/288
• US Class Current: 323/288
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• 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 DC-DC converter including a Pulse Width Modulation (PWM) controller for converting an input voltage into an output voltage is provided. The PWM controller includes: an error amplifier, receiving a reference voltage and a feedback voltage and provides an error signal; a compensation unit coupled to an output of the error amplifier, compensating the error signal and comprising a first resister and a first capacitor; a ramp generator, generating a ramp signal according to a constant on time PWM signal; a first comparator coupled to the compensation unit and the ramp generator, comparing the compensated error signal with the ramp signal to generate a trigger signal; and a PWM generator coupled to the first comparator, providing the constant on time PWM signal according to the trigger signal, an input voltage of the DC-DC converter and the output voltage of the DC-DC converter.

Claims

1. A Pulse Width Modulation (PWM) controller of a DC-DC converter, comprising:

an error amplifier, receiving a reference voltage and a feedback voltage corresponding to an output voltage of the DC-DC converter to provide an error signal;

a compensation unit coupled to an output of the error amplifier, compensating the error signal and comprising a first resistor and a first capacitor, wherein the capacitor is coupled between the first resistor and a ground;

a ramp generator, generating a ramp signal according to an on time signal;

a first comparator coupled to the compensation unit and the ramp generator, wherein when the compensated error signal exceeds the ramp signal, the first comparator generates a trigger signal, wherein the compensation unit causes an included angle between the compensated error signal and the ramp signal to increase; and

a PWM generator coupled to the first comparator, providing the on time signal according to the trigger signal, an input voltage of the DC-DC converter and the output voltage of the DC-DC converter.

2. The PWM controller as claimed in claim 1, wherein the PWM generator comprises:

a current generating unit, providing a first current corresponding to the input voltage of the DC-DC converter when the trigger signal is triggered;

a second capacitor coupled between the current generating unit and the ground, wherein the second capacitor is charged by the first current when the trigger signal is triggered; and

a second comparator, comparing a voltage of the second capacitor with a voltage corresponding to the output voltage of the DC-DC converter to generate the on time signal.

3. The PWM controller as claimed in claim 2, wherein the PWM generator further comprises:

a second resistor coupled to the ground;

a first amplifier, having an first input terminal coupled to the second resistor, a second input terminal for receiving a first voltage corresponding to the input voltage of the DC-DC converter, and an output terminal;

a transistor coupled to the second resistor, the first amplifier and the current generating unit, wherein the first current from the current generating unit flows to the second resistor through the transistor when the trigger signal is triggered, and the first current corresponds to the first voltage.

4. A constant on time PWM controller of a DC-DC converter, comprising:

an error amplifier, receiving a reference voltage and a feedback voltage corresponding to an output voltage of the DC-DC converter to provide an error signal;

a first comparator, comparing the error signal with a ramp signal to generate a trigger signal;

a PWM generator coupled to the first comparator, generating a constant on time PWM signal according to the trigger signal, an input voltage of the DC-DC converter and the output voltage of the DC-DC converter; and

a ramp generator, generating the ramp signal according to the constant on time PWM signal,

wherein the PWM generator comprises;

a current generating unit, providing a first current corresponding to the input voltage of the DC-DC converter when the trigger signal is triggered;

a first capacitor coupled between the current generating unit and a ground, wherein the first capacitor is charged by the first current when the trigger signal is triggered; and

a second comparator, comparing a voltage of the first capacitor with a voltage corresponding to the output voltage of the DC-DC converter to generate the constant on time PWM signal.

5. The constant on time PWM controller of a DC-DC converter as claimed in claim 4, further comprising:

a compensation unit, compensating the error signal and causing an included angle between the compensated error signal and the ramp signal to increase.

6. The constant on time PWM controller of a DC-DC converter as claimed in claim 4, wherein the PWM generator further comprises:

a resistor coupled to a ground;

a first amplifier, having an first input terminal connected to the resistor, a second input terminal for receiving a first voltage corresponding to the input voltage of the DC-DC converter, and an output terminal;

a transistor coupled to the second resistor, the first amplifier and the current generating unit, wherein the first current from the current generating unit flows to the resistor through the transistor when the trigger signal is triggered, and the first current corresponds to the first voltage.

7. The constant on time PWM controller of a DC-DC converter as claimed in claim 4, wherein the ramp generator comprises:

a second amplifier having a first input terminal for receiving a second voltage, an second input terminal, and an output terminal;

a first switch coupled to the second input terminal and the output terminal of the second amplifier;

a current source;

a second switch, coupled between the first switch and the current source, wherein the first switch and the second switch are controlled by the constant on time PWM signal; and

a second capacitor coupled to the first switch and the second switch.

8. A constant on time PWM controller of a DC-DC converter, comprising:

an error amplifier, receiving a reference voltage and a feedback voltage corresponding to an output voltage of the DC-DC converter to generate an error signal;

a sense unit, generating a sense current corresponding to a loading of the DC-DC converter;

a compensation unit coupled to an output terminal of the error amplifier, generating a compensation signal according to the error signal and the sense current;

a first comparator, comparing the compensation signal with a ramp signal to generate a trigger signal;

a PWM generator, generating a constant on time PWM signal according to the trigger signal, an input voltage of the DC-DC converter and the output voltage of the DC-DC converter; and

a ramp generator, generating the ramp signal according to the constant on time PWM signal.

9. A constant on time PWM controller of a DC-DC converter, comprising:

an error amplifier, receiving a reference voltage and a feedback voltage corresponding to an output voltage of the DC-DC converter to generate an error signal;

a sense unit, generating a sense current corresponding to a loading of the DC-DC converter;

a compensation unit, generating a compensation signal according to the sense current and a ramp signal, and comprising a first resistor and a first capacitor connected in series for compensating the error signal;

a first comparator, comparing the compensation signal with the error signal to generate a trigger signal;

a PWM generator, generating a PWM signal with a fixed turn-on time, wherein a frequency of the PWM signal is adjusted according to the trigger signal, an input voltage of the DC-DC converter and the output voltage of the DC-DC converter; and

a ramp generator, generating the ramp signal,

wherein the PWM generator comprises;

a current generating unit, providing a first current corresponding to the input voltage of the DC-DC converter when the trigger signal is triggered;

a second capacitor coupled between the current generating unit and a ground, wherein the second capacitor is charged by the first current when the trigger signal is triggered; and

a second comparator, comparing a voltage of the second capacitor with a voltage corresponding to the output voltage of the DC-DC converter to generate the PWM signal.

10. The constant on time PWM controller of a DC-DC converter as claimed in claim 9, wherein the PWM generator further comprises:

a first amplifier, having an inverting input terminal coupled to a node, a non-inverting input terminal for receiving a first voltage corresponding to the input voltage of the DC-DC converter, and an output terminal;

a second resistor coupled between the node and the ground;

a transistor coupled between the node and the current generating unit, having a gate coupled to the output terminal of the first amplifier, wherein the first current from the current generating unit flows to the second resistor through the transistor when the trigger signal is triggered, and the first current corresponds to the first voltage.

11. The constant on time PWM controller of a DC-DC converter as claimed in claim 9, wherein the compensation unit further comprises:

a second resistor coupled between the sense unit and the ramp generator, wherein a voltage across the second resistor corresponds to the sense current, and the compensation signal is generated according to the sense current, the ramp signal and the voltage across the second resistor.