Power converter with improved load transient response and associated control method

• US 10,727,742 B2
• Filed: 10/16/2018
• Issued: 07/28/2020
• Est. Priority Date: 10/16/2017
• Status: Active Grant

• Current Assignee: Chengdu Monolithic Power Systems Company Limited (Monolithic Power Systems Incorporated)
• Original Assignee: Chengdu Monolithic Power Systems Company Limited (Monolithic Power Systems Incorporated)
• Inventors: Chen, Changjiang, Li, Lei
• Primary Examiner(s): Tran, Nguyen
• Assistant Examiner(s): Singh, David A.
• Application Number:
  US16/162,042
• Publication Number:
  US 20190115831A1
• Time in Patent Office: 651 Days
• CPC Class Codes: G05F 1/10 Regulating voltage or current G05F1/02 takes precedence; for electric railways B60M3/02
• CPC Class Codes: H02M 11/00 Power conversion systems not covered by the preceding groups
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/1566 with means for compensating against rapid load changes, e.g. with auxiliary current source, with dual mode control or with inductance variation
• 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: H03K 19/20 characterised by logic function, e.g. AND, OR, NOR, NOT circuits H03K19/003 - H03K19/01 take precedence

Abstract

A power converter including a load transient enhancing module and associated method for improving load transient response of the power converter. The load transient enhancing module detects whether load transient is occurring in a load of the power converter, and turns the secondary switch off and locks the secondary switch at “OFF” state to turn on a body diode of the secondary switch once load transient is occurring in the load.

Claims

1. A load transient enhancing module for a power converter having a main switch and a secondary switch, comprising:

a first input terminal, configured to receive a secondary switch control signal, wherein the secondary switch control signal is used to control on and off switching of the secondary switch;

a second input terminal, configured to receive a load transient indication signal, wherein the load transient indication signal indicates whether a transient change is occurring in a load of the power converter; and

an output terminal, configured to provide a load transient enhancing signal;

wherein the load transient enhancing module is configured to generate the load transient enhancing signal at least based on the secondary switch control signal and the load transient indication signal; and

wherein when the load transient indication signal indicates that a transient change is occurring, the load transient enhancing module is configured to disable the secondary switch control signal and to set the load transient enhancing signal to turn off the secondary switch and lock the secondary switch at “

OFF”

state so that a body diode of the secondary switch is turned on; and

wherein the load transient enhancing module further comprises a third input terminal, configured to receive a main switch control signal, and wherein the main switch control signal is logically complementary with the secondary switch control signal and is used to control on and off switching of the main switch; and

wherein when the load transient indication signal indicates that no transient change is occurring as well as the main switch control signal changes to a logic state that drives the main switch on, the load transient enhancing module is configured to enable the secondary switch control signal, and to synchronize the load transient enhancing signal with the secondary switch control signal.

2. The load transient enhancing module of claim 1, further comprising:

a single pulse generator, configured to receive the load transient indication signal, and to output a single pulse signal when the load transient indication signal indicates that transient change is occurring;

a first inverter, configured to receive the load transient indication signal and to output an inverted signal of the load transient indication signal;

an RS flip-flop, having a set input terminal configured to receive the single pulse signal, a reset input terminal configured to receive the inverted signal of the load transient indication signal, a non-inverse output terminal configured to provide a non-inversion signal, and an inverse output terminal configured to provide an inversion signal;

a first NAND gate, configured to receive the inversion signal and the secondary switch control signal, and to perform NAND logic operation to the non-inversion signal and the secondary switch control signal to provide a first operation result; and

a second inverter, configured to perform inversion logic operation to the first operation result to provide the load transient enhancing signal.

3. The load transient enhancing module of claim 2, wherein:

when the load transient indication signal indicates that transient change is occurring, the single pulse signal sets the RS flip-flop to set the non-inversion signal to logic high state and the inversion signal to logic low state, which disables the secondary switch control signal and locks the load transient enhancing signal at logic low state, wherein the secondary switch is switched off and locked at “

OFF”

state by the load transient enhancing signal so that the body diode of the secondary switch is conducted; and

wherein when the load transient indication signal indicates that no transient change is occurring, the inverted signal of the load transient indication signal resets the RS flip-flop to reset the non-inversion signal to logic low state and the inversion signal to logic high state, which enables the secondary switch control signal, wherein the load transient enhancing signal follows the secondary switch control signal and has the same logic state as the secondary switch control signal to control the secondary switch to perform normal on and off switching.

4. The load transient enhancing module of claim 2, further comprising:

a schottky diode, connected in parallel with the secondary switch; and

a schottky diode control switch, coupled in series with the schottky diode, wherein a control terminal of the schottky diode control switch is configured to receive the non-inversion signal; and

wherein when the load transient indication signal indicates that transient change is occurring, the non-inversion signal turns the schottky diode control switch on to turn on the schottky diode; and

wherein when the load transient indication signal indicates that no transient change is occurring, the non-inversion signal turns the schottky diode control switch off to turn off the schottky diode.

5. The load transient enhancing module of claim 1, further comprising:

a single pulse generator, configured to receive the load transient indication signal, and to output a single pulse signal when the load transient indication signal indicates that transient change is occurring;

a first inverter, configured to receive the load transient indication signal and to output an inverted signal of the load transient indication signal;

an RS flip-flop, having a set input terminal configured to receive the single pulse signal, a reset input terminal, a non-inverse output terminal configured to provide a non-inversion signal, and an inverse output terminal configured to provide an inversion signal;

a first NAND gate, configured to receive the inversion signal and the secondary switch control signal, and to perform NAND logic operation to the non-inversion signal and the secondary switch control signal to provide a first operation result;

a second inverter, configured to perform inversion logic operation to the first operation result to provide the load transient enhancing signal;

a second NAND gate, configured to receive the inverted signal of the load transient indication signal and a main switch control signal which is used to control on and off switching of the main switch, and to perform NAND logic operation to the inverted signal of the load transient indication signal and the main switch control signal to provide a second operation result; and

a third inverter, configured to perform inversion logic operation to the second operation result to provide a reset control signal to the reset terminal of the RS flip-flop.

6. The load transient enhancing module of claim 5, wherein:

when the load transient indication signal indicates that transient change is occurring, the single pulse signal sets the RS flip-flop to set the non-inversion signal to logic high state and the inversion signal to logic low state, which disables the secondary switch control signal and locks the load transient enhancing signal at logic low state, wherein the secondary switch is switched off and locked at “

OFF”

state by the load transient enhancing signal so that the body diode of the secondary switch is conducted; and

wherein;

when the load transient indication signal indicates that no transient change is occurring as well as the main switch control signal changes to the logic state that drives the main switch on, the reset control signal changes to logic high state which resets the RS flip-flop to reset the non-inversion signal to logic low state and the inversion signal to logic high state, which enables the secondary switch control signal, wherein the load transient enhancing signal follows the secondary switch control signal and has the same logic state as the secondary switch control signal to control the secondary switch to perform normal on and off switching.

7. The load transient enhancing module of claim 5, further comprising:

a schottky diode, connected in parallel with the secondary switch; and

a schottky diode control switch, coupled in series with the schottky diode, wherein a control terminal of the schottky diode control switch is configured to receive the non-inversion signal; and

wherein when the load transient indication signal indicates that transient change is occurring, the non-inversion signal turns the schottky diode control switch on to turn on the schottky diode; and

wherein when the load transient indication signal indicates that no transient change is occurring, the non-inversion signal turns the schottky diode control switch off to turn off the schottky diode.

8. The load transient enhancing module of claim 1, further comprising:

a schottky diode connected in parallel with the secondary switch, wherein when the load transient indication signal indicates that transient change is occurring, the load transient enhancing module is configured to turn off the secondary switch and lock the secondary switch at “

OFF”

state, and to turn on the schottky diode instead of the body diode.

9. The load transient enhancing module of claim 8, wherein when the load transient indication signal indicates that no transient change is occurring, the load transient enhancing module is further configured to turn off the schottky diode, and to synchronize the load transient enhancing signal with the secondary switch control signal so as to control the secondary switch to perform normal on and off switching.