Current-sharing circuit for DC-DC converters

Patent metadata

Field	Value
Publication number	US-10211728-B2
Application number	US-201715447538-A
Country	US
Kind code	B2
Filing date	Mar 2, 2017
Priority date	Mar 2, 2017
Publication date	Feb 19, 2019
Grant date	Feb 19, 2019

Abstract

Two or more power converters are connected in parallel to supply power current to a joining node through connecting resistors. An output voltage before the connecting resistor in each power converter is sampled and divided by a sampling ratio to generate sampled voltages for each power converter. A current sharing circuit for each power converter receives the local sampled voltage and another sampled voltage from another power converter. The current sharing circuit generates an adjustment voltage that is injected into a feedback loop. The adjustment voltage modifies the output voltage of the power converter, adjusting and balancing the power current delivered by that power converter. Power currents from several power converters are reduced and balanced when the same sampling ratio is used for all power converters. Current hogging by one power converter is prevented.

First claim

We claim:

1. A parallel power converter system comprising:
a plurality of power converters, each power converter comprising:
an input voltage;
a voltage adjustment port for receiving an adjustment voltage, the adjustment voltage for adjusting a power current delivered by the power converter;
a connecting resistor connected between a sampling node from the power converter and a joining node external to the power converter;
a voltage divider, directly connected to the sampling node and directly connected to a divided node, that divides a voltage of the sampling node to directly generate a sampled voltage on the divided node;
a current sharing circuit that compares the sampled voltage to an external sampled voltage from another one of the plurality of power converters to generate the adjustment voltage that is applied to the voltage adjustment port to adjust the power current;
wherein each of the power current through each of the connecting resistor is controlled for sharing among the plurality of power converters;
wherein joining nodes of all power converters in the plurality of power converters are connected together to drive power currents to a load;
wherein power currents from the plurality of power converters are summed by the joining node;
wherein the current sharing circuit further comprises:
an op amp having a first input and a second input and an output;
a first input resistor that couples the sampled voltage to the first input of the op amp;
a second input resistor that couples the external sampled voltage to the second input of the op amp; and
a feedback compensation network between the output and the first input of the op amp.

2. The parallel power converter system of claim 1 wherein each power converter further comprises:
a power transistor connected between the input voltage and a first node;
an inductor coupled between the first node and the sampling node;
a Pulse-Width-Modulator for modulating a gate of the power transistor; and
an internal feedback loop for sampling the sampling node to generate an error signal to control the Pulse-Width-Modulator.

3. The parallel power converter system of claim 2 wherein the internal feedback loop further comprises:
a voltage sampler that samples a voltage of the sampling node to generate an internally sampled voltage;
a subtractor that subtracts the internally sampled voltage from a second input to generate the error signal;
an adder that adds the adjustment voltage from the current sharing circuit to a reference voltage to drive the second input to the subtractor.

4. The parallel power converter system of claim 3 wherein the internal feedback loop further comprises:
a compensator that receives the error signal and drives the Pulse-Width-Modulator.

5. The parallel power converter system of claim 3
wherein when the plurality of power converters comprises at least three power converters, wherein a power converter in the plurality of power converters is a reference power converter that outputs the sampled voltage from the voltage divider as a reference sampled voltage;
wherein other power converters in the plurality of power converters receive the reference sampled voltage as the external sampled voltage to the current sharing circuit.

6. The parallel power converter system of claim 1 wherein the current sharing circuit further comprises:
a limiter for limiting an amplitude of the output of the op amp to generate the adjustment voltage.

7. The parallel power converter system of claim 6 wherein the feedback compensation network comprises:
a feedback capacitor coupled between the output and the first input of the op amp;
a series feedback capacitor and a series resistor coupled in series between the output and the first input of the op amp.

8. The parallel power converter system of claim 3 wherein power currents through the connecting resistors from different power converters in the plurality of power converters are matched to within 5%.

9. The parallel power converter system of claim 3 wherein power currents through the connecting resistors from different power converters in the plurality of power converters are matched to within 2%.

10. The parallel power converter system of claim 3 wherein each power converter further comprises:
a bypass capacitor coupled between the sampling node and a ground.

11. The parallel power converter system of claim 10 wherein each power converter further comprises:
a diode coupled between the first node and a ground.

12. The parallel power converter system of claim 11 wherein the power transistor is an n-channel transistor having a drain connected to the input voltage, a source connected to the first node, and a gate driven by the Pulse-Width-Modulator.

13. The parallel power converter system of claim 3 wherein the voltage divider that divides a voltage of the sampling node to generate a sampled voltage divides by a sampling ratio;
wherein the sampling ratio has a same value for all power converters in the plurality of power converters.

14. A sharing power converter comprising:
an input voltage;
a first power converter that comprises:
a first power transistor connected between the input voltage and a first node;
a first inductor coupled between the first node and a first sampling node;
a first connecting resistor connected between the first sampling node and a joining node;
a first voltage divider, connected to the first sampling node and isolated from the joining node, that divides a voltage of the first sampling node to generate a first sampled voltage on a first divided node that is isolated from the joining node;
a first current sharing circuit that compares the first sampled voltage to a second sampled voltage to generate a first adjustment voltage;
a first Pulse-Width-Modulator for modulating a first gate of the first power transistor; and
a first internal feedback loop for sampling the first sampling node to generate a first error signal to control the first Pulse-Width-Modulator;

a second power converter that comprises:
a second power transistor connected between the input voltage and a second node;
a second inductor coupled between the second node and a second sampling node;
a second connecting resistor connected between the second sampling node and the joining node;
a second voltage divider, connected to the second sampling node and isolated from the joining node, that divides a voltage of the second sampling node to generate the second sampled voltage on a second divided node that is isolated from the joining node;
a second current sharing circuit that compares the second sampled voltage to the first sampled voltage to generate a second adjustment voltage;
a second Pulse-Width-Modulator for modulating a second gate of the second power transistor; and
a second internal feedback loop for sampling the second sampling node to generate a second error signal to control the second Pulse-Width-Modulator.

15. The sharing power converter of claim 14 wherein the first voltage divider divides by a sampling ratio;
wherein the second voltage divider divides by the sampling ratio.

Assignees

• Hong Kong Applied Science & Tech Research Inst Co Ltd

Inventors

• Hu Xiaoyong
• Gao Ziyang
• Shum Tak Lok

Classifications

• H02M3/156 Primary

  with automatic control of output voltage or current, e.g. switching regulators · CPC title

• H02M3/1584 Primary

  with a plurality of power processing stages connected in parallel · CPC title

• H02M3/1586

  switched with a phase shift, i.e. interleaved · CPC title