# US 7,746,040 B2 · AC to DC converter with power factor correction

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- Number: US 7,746,040 B2
- Document ID: US7746040B2
- Status: Granted
- Kind: B2
- Application number: 12/101,353
- Filed: 2008-04-11
- Published: 2009-10-15
- Granted: 2010-06-29
- Earliest claimed: 2008-04-11
- Assignees: Flextronics AP, LLC
- Inventors: Paul Garrity; Zaohong Yang
- Web page: https://patentgrep.com/patent/US7746040B2

## CPC

- H02M 1/4225: {using a non-isolated boost converter}
- 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
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

An input current shaping AC to DC converter with PFC front end that reduces input current harmonics is provided. In one embodiment, an AC to DC converter connectable with an alternating current source and operable to output a direct current has a PFC front end followed by a DC/DC converter. The PFC front end reduces harmonic components present in an input current waveform received by the PFC front end from the alternating current source and includes current steering circuitry and, optionally, valley filling circuitry. The DC/DC converter is one that presents pure resistive input impedance to the PFC front end. The DC/DC converter outputs the direct current to a load connected thereto.

## Claims

### Claim 1

An AC to DC converter connectable with an alternating current source and operable to output a direct current, said converter comprising:
a power factor corrective (PFC) front end including current steering circuitry that reduces harmonic components present in an input current waveform received by the PFC front end from the alternating current source, the current steering circuitry being connected between a first node and a common node of the PFC front end; and
a DC/DC converter following the PFC front end, wherein said DC/DC converter is connected in parallel with the current steering circuitry between the first node and the common node and presents pure resistive input impedance to the PFC front end, said DC/DC converter outputting the direct current to a load connected to said DC/DC converter.

### Claim 2 (depends on 1)

The converter of claim 1 wherein said current steering circuitry comprises three capacitors and six diodes.

### Claim 3 (depends on 2)

The converter of claim 2 wherein said three capacitors and six diodes are arranged in a network having six nodes and wherein:
a first capacitor is connected between the first node and a second node;
a second capacitor is connected between a third node and a fourth node;
a third capacitor is connected between a fifth node and the common node;
a first diode is connected between the first node and the fifth node;
a second diode is connected between the first node and the third node;
a third diode is connected between the second node and the third node;
a fourth diode is connected between the fourth node and the fifth node;
a fifth diode is connected between the fourth node and the common node; and
a sixth diode is connected between the second node and the common node.

### Claim 4 (depends on 1)

The converter of claim 1 wherein said current steering circuitry comprises two capacitors and three diodes.

### Claim 5 (depends on 4)

The converter of claim 4 wherein the two capacitors and three diodes are arranged in a network having four nodes and wherein:
a first capacitor is connected between the first node and a second node;
a second capacitor is connected between a third node and the common node;
a first diode is connected between the first node and the third node;
a second diode is connected between the second node and the third node; and
a third diode is connected between the second node and the common node.

### Claim 6 (depends on 1)

The converter of claim 1 wherein said PFC front end further includes:
valley filling circuitry that reduces the presence of discontinuities in the input current waveform.

### Claim 7 (depends on 6)

The converter of claim 6 wherein said valley filling circuitry comprises an inductor, a diode, and a switching element.

### Claim 8 (depends on 7)

The converter of claim 7 wherein said diode, inductor, and switching element are arranged in a network having four nodes and wherein:
said diode is connected between the first node and a second node;
said inductor is connected between a third node and the second node; and
said switching element is connected between the second node and the common node.

### Claim 9

AC to DC conversion means connectable with an alternating current source and operable to output a direct current, said conversion means comprising:
first stage means for correcting a power factor, said first stage means including current steering means for reducing harmonic components present in an input current waveform received by the first stage means from the alternating current source, the current steering means being connected between a first node and a common node of the first stage means; and
second stage means for outputting the direct current to a load connected to said second stage means, wherein said second stage means are connected in parallel with the current steering means between the first node and the common node and present pure resistive input impedance to the first stage means.

### Claim 10 (depends on 9)

The conversion means of claim 9 wherein said current steering means comprise:
first charge storing means connected between the first node and a second node;
a second charge storing means connected between a third node and a fourth node;
a third charge storing means connected between a fifth node and the common node;
first current blocking means connected between the first node and the fifth node;
second current blocking means connected between the first node and the third node;
third current blocking means connected between the second node and the third node;
fourth current blocking means connected between the fourth node and the fifth node;
fifth current blocking means connected between the fourth node and the common node; and
a sixth current blocking means connected between the second node and the common node.

### Claim 11 (depends on 10)

The conversion means of claim 10 wherein said charge storing means comprise capacitors.

### Claim 12 (depends on 10)

The conversion means of claim 10 wherein said current blocking means comprise diodes.

### Claim 13 (depends on 9)

The conversion means of claim 9 wherein said current steering means comprise:
first charge storing means connected between the first node and a second node;
second charge storing means connected between a third node and the common node;
first current blocking means connected between the first node and the third node;
second current blocking means connected between the second node and the third node; and
third current blocking means connected between the second node and the common node.

### Claim 14 (depends on 13)

The conversion means of claim 13 wherein said charge storing means comprise capacitors.

### Claim 15 (depends on 13)

The conversion means of claim 13 wherein said current blocking means comprise diodes.

### Claim 16 (depends on 9)

The conversion means of claim 9 wherein said first stage means further include:
valley filling means for reducing the presence of discontinuities in the input current waveform.

### Claim 17 (depends on 16)

The conversion means of claim 16 wherein said valley filling means comprise:
current blocking means connected between the first node and a second node;
current change opposing means connected between a third node and the second node; and
switching means connected between the second node and the common node.

### Claim 18 (depends on 17)

The conversion means of claim 17 wherein said current change opposing means comprise an inductor, said current blocking means comprise a diode, and said switching means comprise a transistor.

### Claim 19

A current shaping AC to DC converter, said converter comprising:
a valley filling circuit connected to at least a first node and a common node;
a current steering circuit connected between the first node and the common node; and
a constant power DC/DC converter connected with the current steering circuit and the valley filling circuit, wherein said DC/DC converter is connected in parallel with the current steering circuit between the first node and the common node and presents pure resistive input impedance to the current steering circuit.

### Claim 20 (depends on 19)

The converter of claim 19 wherein said current steering circuit comprises three capacitors and six diodes.

### Claim 21 (depends on 20)

The converter of claim 20 wherein said three capacitors and six diodes are arranged in a network having six nodes and wherein:
a first capacitor is connected between the first node and a second node;
a second capacitor is connected between a third node and a fourth node;
a third capacitor is connected between a fifth node and the common node;
a first diode is connected between the first node and the fifth node;
a second diode is connected between the first node and the third node;
a third diode is connected between the second node and the third node;
a fourth diode is connected between the fourth node and the fifth node;
a fifth diode is connected between the fourth node and the common node; and
a sixth diode is connected between the second node and the common node.

### Claim 22 (depends on 19)

The converter of claim 19 wherein said current steering circuit comprises two capacitors and three diodes.

### Claim 23 (depends on 22)

The converter of claim 22 wherein the two capacitors and three diodes are arranged in a network having four nodes and wherein:
a first capacitor is connected between the first node and a second node;
a second capacitor is connected between a third node and the common node;
a first diode is connected between the first node and the third node;
a second diode is connected between the second node and the third node; and
a third diode is connected between the second node and the common node.

### Claim 24 (depends on 19)

The converter of claim 19 wherein said valley filling circuit comprises an inductor, a diode, and a switching element.

### Claim 25 (depends on 24)

The converter of claim 24 wherein said diode, inductor and switching element are arranged in a network having four nodes and wherein:
said diode is connected between the first node and a second node;
said inductor is connected between a third node and the second node; and
said switching element is connected between the second node and the common node.