Reference signal generator and the method thereof

Patent metadata

Field	Value
Publication number	US-2016147248-A1
Application number	US-201514937853-A
Country	US
Kind code	A1
Filing date	Nov 10, 2015
Priority date	Nov 21, 2014
Publication date	May 26, 2016
Grant date	—

Abstract

A reference signal generator used with a switching mode power supply which converts an input voltage to an output voltage. The reference signal generator provides a reference signal consisting of a constant voltage signal and a variable voltage signal which is varying according to a duty cycle of the switching mode power supply during a startup period of the switching mode power supply and is varying according to a ratio of the input voltage at an end of the startup period to the input voltage of real time after the startup period.

First claim

What is claimed is:

1 . A reference signal generator used with a switching mode power supply, wherein the switching mode power supply converts an input voltage to an output voltage, comprising:
a constant voltage generator configured to provide a constant voltage signal; a voltage convert circuit having an input terminal configured to receive the input voltage, a first output terminal configured to provide a startup voltage converted digital signal indicative of the input voltage during a startup period of the switching mode power supply, and a second output terminal configured to provide a real time voltage converted digital signal indicative of the real time input voltage; a duty cycle convert circuit, having an input terminal configured to receive a duty cycle signal indicative of a duty cycle of the switching mode power supply, and an output terminal configured to provide a duty cycle converted digital signal indicative of the duty cycle of the switching mode power supply; and a variable voltage generator having a first input terminal coupled to the first output terminal of the voltage convert circuit to receive the startup voltage converted digital signal, a second input terminal coupled to the second output terminal of the voltage convert circuit to receive the real time voltage converted digital signal, a third input terminal coupled to the output terminal of the duty cycle convert circuit to receive the duty cycle converted digital signal, and an output terminal configured to provide a variable voltage signal based on the startup voltage converted digital signal, the real time voltage converted digital signal and the duty cycle converted digital signal; wherein a reference signal is generated based on a sum of the constant voltage signal and the variable voltage signal.

2 . The reference signal generator of claim 1 , wherein the constant voltage generator comprises:
a reference current source having an input terminal configured to receive an internal power supply and an output terminal configured to provide a preset reference current; a reference resistor having a first terminal and a second terminal, wherein the first terminal is coupled to the output terminal of the reference current source to receive the preset reference current; and a compensation resistor coupled between the second terminal of the reference resistor and a ground reference; wherein the preset current provided by the reference current source flows through the reference resistor and the compensation resistor to generate the constant voltage signal across the reference resistor and the compensation resistor.

3 . The reference signal generator of claim 2 , wherein the variable voltage generator comprises:
a compensation current source having a first control terminal configured to receive the startup voltage converted digital signal, a second control terminal configured to receive the real time voltage converted digital signal, and an output terminal configured to provide a compensation current based on the startup voltage converted digital signal and the real time voltage converted digital signal; and the compensation resistor having a first terminal coupled to the output terminal of the compensation current source to receive the compensation current, a second terminal coupled to the second terminal of the reference resistor, a third terminal connected to the ground reference and a control terminal configured to receive the duty cycle converted digital signal; wherein the compensation current flows through part of the compensation resistor to generate the variable voltage signal, and the reference signal is provided at the connection node of the reference current source and the reference resistor.

4 . The reference signal generator of claim 3 , wherein the compensation current source comprises:
a source circuit including: a current source having a first terminal and a second terminal, wherein the second terminal is connected to the ground reference; a first set of N current branches coupled in parallel between the internal power supply and the first terminal of the current source, wherein each current branch comprises a MOSFET and a switch coupled in series, and wherein a control terminal of each MOSFET is coupled to the first terminal of the current source, and a control terminal of each switch is coupled to the second output terminal of the voltage convert circuit to receive the real time voltage converted digital signal; and a mirror circuit including: a second set of N current branches coupled in parallel between the internal power supply and the first terminal of the compensation resistor, wherein each current branch comprises a MOSFET and a switch coupled in series, and wherein a control terminal of each MOSFET coupled to the control terminal of the MOSFET from the source circuit, and a control terminal of each switch is coupled to the first output terminal of the voltage convert circuit to receive the startup voltage converted digital signal; wherein N is an integer and N>1.

5 . The reference signal generator of claim 3 , wherein the compensation resistor comprises:
N switches, wherein each switch has a first terminal, a second terminal and a control terminal, and wherein the first terminal of each switch is coupled to the output terminal of the compensation current source, and the control terminal of each switch is coupled to the output terminal of the duty cycle convert circuit to receive the duty cycle converted digital signal; and N resistors coupled in series between the second terminal of the reference resistor and the ground reference, wherein each resistor has a first terminal and a second terminal, the first terminal of a first resistor coupled to the second terminal of the reference resistor and the second terminal of the first switch, the second terminal of the N-th resistor connected to the ground reference, and the second terminal of the i-th switch is coupled to the connection node of second terminal of the (i−1)-th resistor and the first terminal of the i-th resistor, and wherein 1<i≦N, and wherein N is an integer and N>1.

6 . The reference signal generator of claim 2 , wherein the variable voltage generator comprises:
a compensation current source having a first control terminal configured to receive the startup voltage converted digital signal, a second control terminal configured to receive the real time voltage converted digital signal, a third control terminal configured to receive a duty cycle converted digital signal, and an output terminal configured to provide a compensation current based on the startup voltage converted digital signal, the real time voltage converted digital signal and the duty cycle converted digital signal; and the compensation resistor having a first terminal coupled to the output terminal of the compensation current source to receive the compensation current, a second terminal connected to the ground reference; wherein the reference signal is provided at the connection node of the reference current source and the reference resistor.

7 . The reference signal generator of claim 6 , wherein the compensation current source comprises:
a source circuit including: a current source having a first terminal and a second terminal, wherein the first terminal is coupled to the internal power supply; a first set of N current branches coupled in parallel between the second terminal of the current source and the ground reference, wherein each current branch comprises a MOSFET and a switch, and wherein each MOSFET has a control terminal coupled to the second terminal of the current source, and each switch has a control terminal coupled to the second output terminal of the voltage convert circuit to receive the real time voltage con

Assignees

• Monolithic Power Systems Inc

Inventors

• Wang Yiwei
• Li Yike

Classifications

• H02M7/217

  using semiconductor devices only · CPC title

• G05F3/26

  Current mirrors · CPC title

• G05F3/262 Primary

  using field-effect transistors only · CPC title