Multimode PWM converter with smooth mode transition

• US 10,566,904 B2
• Filed: 06/19/2018
• Issued: 02/18/2020
• Est. Priority Date: 10/16/2017
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Cohen, Isaac
• Primary Examiner(s): Ahmed, Yusef A
• Assistant Examiner(s): Jamali, Ishrat F
• Application Number:
  US16/011,757
• Publication Number:
  US 20190115835A1
• Time in Patent Office: 609 Days
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 3/33576 having at least one active switching element at the secondary side of an isolation transformer
• 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

Control circuits and methods to operate a switch of a DC-DC converter, including an output circuit to turn the switch off to control a peak inductor current in a given switching control cycle, and a modulation circuit to implement transition mode (TM) or continuous conduction mode (CCM) operation for a given switching control cycle by causing the output circuit to turn the switch on in response to an earlier one of a first signal, that represents an inductor current of the DC-DC converter, decreasing to a reference voltage that represents a zero crossing of the inductor current for the TM operation or the first signal decreasing to a valley reference signal that represents a non-zero value of the inductor current for the CCM operation.

Claims

1. A modulation circuit to operate a switch of a DC-DC converter, the modulation circuit comprising:

a first comparator, including a first input terminal connected to a first node, a second input terminal connected to a second node, and

a first comparator output terminal coupled to a first modulator output node to turn the switch off when a voltage at the second node equals or exceeds a voltage at the first node;

a second comparator, including a first input terminal connected to the second node, a second input terminal connected to a third node, and

a second comparator output terminal coupled to a second modulator output node to turn the switch on when the voltage at the second node is less than or equal to a voltage at the third node;

a first offset circuit, including a first terminal connected to the first node, a second terminal connected to a ground reference voltage node, and a third terminal coupled to a fourth node; and

a second offset circuit, including a first terminal connected to the fourth node, and a second terminal connected to the third node.

2. The modulation circuit of claim 1,

wherein the first offset circuit is configured to control a voltage at the fourth node to be different from the voltage at the first node;

and

wherein the second offset circuit is configured to control the voltage at the third node to be different from the voltage at the fourth node.

3. The modulation circuit of claim 2, wherein the first offset circuit is configured to adjust a difference between the voltage at the fourth node and the voltage at the first node.

4. The modulation circuit of claim 1, wherein the first offset circuit includes:

a Zener diode; and

a resistor coupled in series with the Zener diode between the first node and the ground reference voltage node, the fourth node being coupled to a node that joins the Zener diode and the resistor.

5. The modulation circuit of claim 1, wherein the modulation circuit includes:

a detection circuit, including a detection circuit output terminal coupled to the second modulator output node to turn the switch on when the voltage at the second node is less than or equal to a voltage of the ground reference voltage node; and

a logic circuit, including;

a first input terminal connected to the detection circuit output terminal;

a second input connected to the second comparator output terminal; and

an output coupled to the second modulator output node to turn the switch on when the voltage at the second node is less than or equal to the voltage of the reference voltage node or when the voltage at the second node is less than or equal to the voltage at the third node.

6. The modulation circuit of claim 5, wherein the output of the logic circuit is configured to turn the switch on in response to an earliest one of:

the voltage at the second node decreasing to or below the voltage of the reference voltage node, and the voltage at the second node decreasing to or below the voltage at the third node.

7. The modulation circuit of claim 1, wherein the second comparator output terminal is configured to turn the switch on when the voltage at the second node decreases to or below a highest one of the voltage of the reference voltage node, and the voltage at the third node.

8. The modulation circuit of claim 1, further comprising a clamp circuit coupled to clamp one of the voltage at the first node and the voltage at the third node.