Power supply system, associated current ripple suppression circuit and method

Patent metadata

Field	Value
Publication number	US-9429970-B2
Application number	US-201314038671-A
Country	US
Kind code	B2
Filing date	Sep 26, 2013
Priority date	Sep 27, 2012
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

A power supply system has a current source configured to provide an output current, a load supplied by the current source, and a current ripple suppression circuit. The current ripple suppression circuit has a first end and a second end, wherein the first end of the current ripple suppression circuit is coupled to the load, and the second end of the current ripple suppression circuit is coupled to a reference ground; wherein the current ripple suppression circuit is configured to suppress the current ripple in the output current and adaptively adjust the output current of the current source at a predetermined current level.

First claim

We claim:

1. A power supply system, comprising:
a current source having an output, wherein the output of the current source is configured to provide an output current;
a load having a first end and a second end, wherein the first end of the load is coupled to the output of the current source, and wherein the current source is configured to supply the load with the output current; and
a current ripple suppression circuit having a first end and a second end, wherein the first end of the current ripple suppression circuit is coupled to the second end of the load, and the second end of the current ripple suppression circuit is coupled to a reference ground;
wherein the current ripple suppression circuit is configured to suppress the current ripple in the output current and adaptively adjust the output current of the current source at a predetermined current level by comparing the voltage at the first end of the current ripple suppression circuit with a reference voltage, and wherein when the voltage at the first end of the current ripple suppression circuit is higher than the reference voltage, the current ripple suppression circuit is configured to increase a current flowing through the load, and when the voltage at the first end of the current ripple suppression circuit is lower than the reference voltage, the current ripple suppression circuit is configured to decrease the current flowing through the load.

2. The power supply system of claim 1 , wherein the current ripple suppression circuit comprises a low drop out linear regulator.

3. The power supply system of claim 1 , wherein the current ripple suppression circuit comprises:
a transistor having a first end, a second end and a control end, wherein the first end of the transistor is coupled to the first end of the current ripple suppression circuit, and the second end of the transistor is coupled to the second end of the current ripple suppression circuit; and
a control circuit having a first input, a second input and an output, wherein the first input of the control circuit is coupled to the first end of the transistor configured to receive the voltage at the first end of the transistor, the second input of the control circuit is coupled to the second end of the transistor configured to receive a signal indicating the current flowing through the transistor, and the output of the control circuit is coupled to the control end of the transistor configured to adjust the resistance between the first end of the transistor and the second end of the transistor.

4. The power supply system of claim 3 , wherein the transistor comprises a Metal Oxide Semiconductor Filed Effect Transistor (MOSFET).

5. The power supply system of claim 1 , wherein the current source comprises:
an AC power source having a first end and a second end;
a rectification bridge having a first input, a second input, a first output and a second output, wherein the first input of the rectification bridge is coupled to the first end of the AC power source, the second input of the rectification bridge is coupled to the second end of the AC power source, the first output of the rectification bridge is configured to provide a rectified voltage, and the second output of the rectification bridge is coupled to a primary side reference ground;
a resistor divider having a first end, a second end and an output, wherein the first end of the resistor divider is coupled to the first output of the rectification bridge, the second end of the resistor divider is coupled to the primary side reference ground, and the output of the resistor divider is configured to provide a divided voltage of the rectified voltage;
a transformer comprising a primary side winding and a secondary side winding, wherein the primary side winding has a first end and a second end, and wherein the first end of the primary side winding is coupled to the first output of the rectification bridge;
a switch having a first end, a second end and a control end, wherein the first end of the switch is coupled to the second end of the primary side winding and the second end of the switch is coupled to the primary side reference ground;
a control circuit having a first input, a second input and an output, wherein the first input of the control circuit is coupled to the output of the resistor divider, the second input of the control circuit is coupled to the second end of the switch configured to receive a signal indicating the current flowing through the switch, and the output of the control circuit is coupled to the control end of the switch configured to control the ON and OFF of the switch;
a rectifier coupled to the secondary side winding configured to rectify the current flowing through the secondary side winding; and
an output capacitor having a first end and a second end, wherein the first end of the output capacitor is coupled to the secondary side winding and the output of the current source, and the second end of the output capacitor is coupled to a secondary side reference ground.

6. The power supply system of claim 1 , wherein the load comprises a LED string having a plurality of LEDs coupled in series.

7. The power supply system of claim 1 , wherein the current ripple suppression circuit comprises:
a transistor having a first end, a second end and a control end, wherein the first end of the transistor is coupled to the first end of the current ripple suppression circuit;
a resistor having a first end and a second end, wherein the first end of the resistor is coupled to the second end of the transistor, and the second end of the resistor is coupled to the reference ground;
an error amplifying circuit having a first input, a second input and an output, wherein the first input of the error amplifying circuit is coupled to the first end of the transistor to receive the voltage at the first end of the transistor, the second input of the error amplifying circuit is coupled to the reference voltage, the error amplifying circuit amplifies the difference between the voltage at the first end of the transistor and the reference voltage and further provides an error amplifying signal at the output;
a converting circuit having an input and an output, wherein the input of the converting circuit is coupled to the output of the error amplifying circuit, and the converting circuit is configured to convert the error amplifying signal into an interim voltage, and wherein the interim voltage is lower than the reference voltage; and
an amplifier having a non-inverting input, an inverting input and an output, wherein the non-inverting input of the amplifier is coupled to the output of the converting circuit, the inverting input of the amplifier is coupled to the first end of the resistor, and the output of the amplifier is coupled to the control end of the transistor configured to control the conduction resistance of the transistor.

8. The power supply system of claim 7 , wherein the error amplifying circuit comprises:
an error amplifier having an inverting input, a non-inverting input and an output, wherein the inverting input of the error amplifier is coupled to the first end of the transistor, and the non-inverting input of the error amplifier is coupled to the reference voltage; and
a capacitor having a first end and a second end, wherein the first end of the capacitor is configured to provide the error amplifying signal and the second end of the capacitor is coupled to the reference ground.

9. The power supply system of claim 7 , wherein the converting circuit comprises:
a first resistor having a first end and a second end, wherein the first end of the first resistor of the converting circuit is coupled to the input of the converting circuit;
a Bipolar Junction Trans

Assignees

• Chengdu Monolithic Power Sys

Inventors

• Kuang Naixing
• Yu Jiaqi
• Yu Bo

Classifications

• H02M1/15

  using active elements · CPC title

• G05F1/563 Primary

  including two stages of regulation at least one of which is output level responsive, e.g. coarse and fine regulation · CPC title