AU2021250964B1

AU2021250964B1 - Zero-crossing detector capable of saving power

Info

Publication number: AU2021250964B1
Application number: AU2021250964A
Authority: AU
Inventors: Kuo-Tsun Lin
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-10-15
Filing date: 2021-10-15
Publication date: 2023-03-09
Anticipated expiration: 2041-10-15

Abstract

OF THE DISCLOSURE ZERO-CROSSING DETECTOR CAPABLE OF SAVING POWER A zero-crossing detector to be installed in a ceiling fan (9) includes: a first terminal (21); a 5 second terminal (22); and a rectifier (3), an adjustor (5) and a feedback generator (4) that cooperatively generate a current signal based on an AC voltage between the first and second terminals (21, 22). The current signal has a non-zero magnitude when the AC voltage 10 causes a potential at the first terminal (21) to be greater than a potential at the second terminal (22), and has a zero magnitude when otherwise. An average of the non-zero magnitude of the current signal is greater when the adjustor (5) is in a working state than when 15 the adjustor (5) is in apower saving state. The feedback generator (4) generates a feedback signal based on the current signal. (FIG. 1)

Description

ZERO-CROSSING DETECTOR CAPABLE OF SAVING POWER

The disclosure relates to zero-crossing detection,

and more particularly to a zero-crossing detector

capable of saving power.

A conventional zero-crossing detector installed in

a ceiling fan receives an alternating current (AC)

voltage originating from the mains electricity for

powering the ceiling fan, and generates a pulse signal,

whichindicates zero-crossing points of the AC voltage,

for receipt by a control module of the ceiling fan. When

the mains electricity is stably supplied to the ceiling

fan, the ceiling fan can be turned on so that vanes of

the ceiling fan start to rotate, and can be turned off

so that the vanes stop rotating. When the ceiling fan

is turned on, the control module controls the rotation

of the vanes or light emission of lamps of the ceiling

fan based on the pulse signal.

When the ceiling fan enters a sleep mode after being

turned off for a while, the AC voltage is still supplied

to the conventional zero-crossing detector, the

conventional zero-crossing detector still generates

the pulse signal, and the ceiling fan still consumes

relatively high power. Therefore, the control module

can learn a condition of the mains electricity based

on the pulse signal, and can execute a power-off

protection procedure upon loss of the mains electricity.

If the supply of the AC voltage to the conventional

zero-crossing detector is interrupted for the purpose

of reducing the power consumption of the ceiling fan,

the conventional zero-crossing detector would not

operate to generate the pulse signal, and the control

module would be unable to learn the condition of the

mains electricity based on the pulse signal and would

be unable to execute the power-offprotection procedure

upon loss of the mains electricity.

Therefore, an aspect of the disclosure is to provide

a zero-crossing detector that is capable of saving

power.

According to the disclosure, the zero-crossing

detector is to be installed in a ceiling fan including

a control unit, and includes a first terminal, a second

terminal, a rectifier, an adjustor and a feedback

generator. The first and second terminals are to

cooperatively receive an alternating current (AC)

voltage. The rectifier, the adjustor and the feedback

generator are coupled in series between the first and

second terminals, cooperatively provide a current path

between the first and second terminals, and

cooperatively generate a current signal based on the

AC voltage. The rectifier performs half-wave

rectification so that the current signal has a non-zero

magnitude and flows from the first terminal along the

current path to the second terminal when the AC voltage causes a potential at the first terminal to be greater than a potential at the second terminal, and has a zero magnitude when otherwise. The adjustor is adapted to be further coupled to the control unit to receive a control signal, and switches between a working state and a power saving state based on the control signal to adjust the non-zero magnitude of the current signal.

An average of the non-zero magnitude of the current

signal is greater when the adjustor is in the working

state than when the adjustor is in the power saving state.

The feedback generator is adapted to be further coupled

to the control unit, and generates a feedback signal

for receipt by the control unit based on the current

signal.

According to the disclosure comment is provided a

zero-crossing detector to be installed in a ceiling fan

that includes a control unit, said zero-crossing

detector comprising: a first terminal and a second

terminal that are to cooperatively receive an

alternating current (AC) voltage; and a rectifier, an

adjustor and a feedback generator that are coupled in

series between said first and second terminals, that

cooperatively provide a current pathbetween said first

and second terminals, and that cooperatively generate

a current signal based on the AC voltage;

3a

said rectifier performing half-wave rectification so

that the current signal has a non-zero magnitude and

flows from said first terminal along said current path

to said second terminal when the AC voltage causes a

potential at said first terminal to be greater than a

potential at said second terminal, and has a zero

magnitude when otherwise; said adjustor being adapted

to be further coupled to the control unit to receive

a control signal, and switching between a working state

and a power saving state based on the control signal

to adjust the non-zero magnitude of the current signal,

an average of the non-zero magnitude of the current

signal being greater when said adjustor is in the

working state than when said adjustor is in the power

saving state; said feedback generator being adapted to

be further coupled to the control unit, and generating

a feedback signal for receipt by the control unit based

on the current signal, the feedback signal having a

characteristic correlated to the magnitude of the

current signal, so as to indicate zero-crossing points

of the AC voltage.

Other features and advantages of the disclosure will

become apparent in the following detailed description

of the embodiment with reference to the accompanying

drawings, of which:

FIG. 1 is a circuit block diagram illustrating an

3b

embodiment of a zero-crossing detector according to the

disclosure in use with a control unit of a ceiling fan;

and

FIGS. 2 to 5 are timing diagrams illustrating

operations of the embodiment.

Referring to FIG. 1, an embodiment of a

zero-crossing detector according to the disclosure is

to be installed in a ceiling fan 9. The ceiling fan 9

is powered by mains electricity, and includes at least a control unit 91. The control unit 91 outputs a control signal, and receives a feedback signal.

In this embodiment, the control unit 91 includes a

control module 911 (e.g., a controller), three

resistors 912, 913, 915, a switch 914 and a capacitor

916. The resistor 912 has a first terminal that is

coupled to apower supply node 92, and a second terminal.

The switch 914 (e.g., a bipolar junction transistor

(BJT)) has a first terminal (e.g., a collector terminal),

a second terminal (e.g., an emitter terminal) that is

coupled to a ground node 93, and a control terminal (e.g.,

a base terminal). The resistor 913 is coupled between

the control terminal of the switch 914 and the control

module 911. The resistor 915 has a first terminal that

is coupled to the power supply node 91, and a second

terminal. The capacitor 916 is coupled between the

second terminal of the resistor 915 and the ground node

93. A common node of the resistor 915 and the capacitor

916 is coupled to the control module 911.

It should be noted that the switch 914 is a BJT in

this embodiment, but may be a metal oxide semiconductor

field effect transistor (MOSFET), a relay or the like

in other embodiments.

The zero-crossing detector of this embodiment

includes a first terminal 21, a second terminal 22, a

rectifier 3, an adjustor 5 and a feedback generator 4.

The first and second terminals 21, 22 are to

cooperatively receive an alternating current (AC)

voltage. The AC voltage may be supplied by the mains

electricity, or may be obtained by an AC power module

(not shown) of the ceiling fan 9 from processing (e.g.,

performing phase fired control on) a voltage supplied

by the mains electricity.

The rectifier 3, the adjustor 5 and the feedback

generator 4 are coupled in series between the first and

second terminals 21, 22, cooperatively provide a

current path 23 between the first and second terminals

21, 22, and cooperatively generate a current signal

based on the AC voltage.

The rectifier 3 performs half-wave rectification so

that the current signal has a non-zero magnitude and

flows from the first terminal 21 along the current path

23 to the second terminal 22 when the AC voltage causes

a potential at the first terminal 21 to be greater than

a potential at the second terminal 22, and has a zero

magnitude otherwise. In this embodiment, the rectifier

3 includes a diode 31 that is located on the current

path 23, and that has an anode, which is coupled to the

first terminal 21, and a cathode. It should be noted

that, in other embodiments, the rectifier 3 may further

include at least one resistor (not shown) that is

located on the current path 23.

The adjustor 5 is adapted to be further coupled to the control unit 91 to receive the control signal, and switches between a working state and a power saving state based on the control signal, so as to adjust the non-zero magnitude of the current signal. An average of the non-zero magnitude of the current signal is greater when the adjustor 5 is in the working state than when the adjustor 5 is in the power saving state.

In this embodiment, the adjustor 5 includes two

terminals 51, 52, a first resistive element 53, a second

resistive element 54 and a switch 55. The terminals 51,

52 are located on the current path 23, and the terminal

51 is coupled to the cathode of the diode 31. The first

resistive element 53 and the switch 55 are coupled in

series between the terminals 51, 52. The switch 55 is

adapted to be further coupled to the control unit 91

to receive the control signal, and switches between

conduction and non-conduction based on the control

signal. The second resistive element 54 is coupled

between the terminals 51, 52. When the switch 55

conducts, the adjustor 5 is in the working state where

the first resistive element 53 is coupled to the second

resistive element 54 in parallel, the current signal

flows from the terminal 51 through the parallel

connection of the first and second resistive elements

53, 54 to the terminal 52, and a resistance provided

by the adjustor 5 between the terminals 51, 52 is equal

to an equivalent resistance of the parallel connection of the first and second resistive elements 53, 54. When the switch 55 does not conduct, the adjustor 5 is in the power saving state where the first resistive element

53 is not coupled to the second resistive element 54

in parallel, the current signal flows from the terminal

51 through only the second resistive element 54 to the

terminal52, and the resistance providedby the adjustor

5 between the terminals 51, 52 is equal to a resistance

of the second resistive element 54. In other words, the

resistance provided by the adjustor 5 between the

terminals 51, 52 is greater when the adjustor 5 is in

the power saving state than when the adjustor 5 is in

the working state.

Optionally, the resistance of the second resistive

element 54 is greater than a resistance of the first

resistive element 53, so that the resistance provided

by the adjustor 5 between the terminals 51, 52 is much

greater when the adjustor 5 is in the power saving state

than when the adjustor 5 is in the working state.

In this embodiment, the first resistive element 53

is implemented using two resistors 531 coupled in

parallel, and the second resistive element 54 is

implemented using a single resistor. However, the

disclosure is not limited to such configuration. For

example, in other embodiments, the first resistive

element 53 may be implemented using a single resistor,

two resistors coupled in series, or at least three resistors coupled in series and/or parallel.

In this embodiment, the switch 55 is an

opto-isolator, and includes a transmitter 551 and a

receiver 552. The transmitter 551 (e.g., a light

emitting diode (LED)) has a first terminal (e.g., an

anode) that is adapted to be coupled to the second

terminal of the resistor 912, and a second terminal

(e.g., a cathode) that is adapted to be coupled to the

first terminal of the switch 914. The transmitter 51

is to receive the control signal from the control unit

91, and converts the controlsignalinto a light signal.

The receiver 552 (e.g., a phototriac) is coupled in

series with the first resistive element 53 between the

terminals 51, 52, is to receive the light signal

generated by the transmitter 551, and switches between

conduction and non-conduction based on the light

signal.

It should be noted that, in other embodiments, the

switch 55 maybe a triac, a silicon controlled rectifier

(SCR), a MOSFET or a BJT, and the circuit (including

the elements 912-914) configured to control the switch

55 should be modified where necessary.

The feedback generator 4 is adapted to be further

coupled to the control unit 91, and generates the

feedback signalfor receipt by the controlunit 91based

on the current signal. In this embodiment, the feedback

generator 4 is an opto-isolator, and includes a transmitter 41 and a receiver 42. The transmitter 41

(e.g., an LED) is located on the current path 23, has

a first terminal (e.g., an anode) and a second terminal

(e.g., a cathode) that are respectively coupled to the

terminal 52 of the adjustor 5 and the second terminal

22, and converts the current signalinto a light signal.

The receiver 42 (e.g., a phototransistor) has a first

terminal (e.g., a collector terminal) that is adapted

to be coupled to the common node of the resistor 915

and the capacitor 916, and a second terminal (e.g., an

emitter terminal) that is to be coupled to the ground

node 93. The receiver 42 is to receive the light signal

generated by the transmitter 41, and generates the

feedback signalfor receipt by the controlunit 91based

on the light signal.

FIG. 2 illustrates the AC voltage. FIG. 3

illustrates a rectified voltage at the terminal 51 of

the adjustor 5, a waveform of which is similar to a

waveform of the current signal. FIG. 4 illustrates a

pulse signalwhen the adjustor 5 is in the working state.

FIG. 5 illustrates the pulse signal when the adjustor

5 is in the power saving state. The pulse signal is

generated by the control unit 91 based on the feedback

signal (e.g., being obtained by the control module 911

from binarizing a voltage across the capacitor 916).

Referring to FIGS. 1 to 5, operations of the

zero-crossing detector of this embodiment are described in detail below.

When the ceiling fan 9 is turned on, the control

module 911 causes the switch 93 to conduct, the control

signal has a non-zero current magnitude, the light

signal generated by the transmitter 551 of the switch

55 has a non-zero intensity, the receiver 552 of the

switch 55 conducts (i.e., the adjustor 5 being in the

working state), and the resistance provided by the

adjustor 5 between the terminals 51, 52 is relatively

small.

Because of the half-wave rectification performed by

the rectifier 3, the rectified voltage as shown in FIG.

3 has a non-zero magnitude when the AC voltage causes

the potential at the first terminal 21 to be greater

than the potential at the second terminal 22 (e.g., in

positive halves of the AC voltage as shown in FIG. 2),

and has a zero magnitude when otherwise. In each

negative half of the AC voltage, the current signal has

a zero magnitude, the light signal generated by the

transmitter 41 of the feedback generator 4 has a zero

intensity, the feedback signal has a zero current

magnitude, the voltage across the capacitor 916 is

pulled up by the resistor 915 to be equal in magnitude

to a power supply voltage at the power supply node 92,

and the pulse signal as shown in FIG. 4 is in a logic

"1" state. In each positive half of the AC voltage, since

the resistance provided by the adjustor 5 between the terminals 51, 52 is relatively small, the current signal has a non-zero magnitude with a relatively large average, the light signal generated by the transmitter 41 of the feedback generator 4 has a non-zero intensity with a relatively large average, the feedback signal has a non-zero current magnitude with a relatively large average, the voltage across the capacitor 916is quickly pulled down to be equalin magnitude to a ground voltage at the ground node 93, and switching of the pulse signal from the logic "1" state to a logic "0" state is substantially concurrent with a respective zero-crossing point of the AC voltage. Since the pulse signal accurately indicates the zero-crossing points of the AC voltage, the control module 911 can control operations of the ceiling fan 9 based on the pulse signal.

When the ceiling fan 9 enters a sleep mode after

being turned off for a while, the control module 911

causes the switch 914 to not conduct, the control signal

has a zero current magnitude, the light signalgenerated

by the transmitter 551 of the switch 55 has a zero

intensity, the receiver 552 of the switch 55 does not

conduct (i.e., the adjustor 5 being in the power saving

state), and the resistance provided by the adjustor 5

between the terminals 51, 52 is relatively large.

Because of the half-wave rectification performed by

the rectifier 3, the rectified voltage as shown in FIG.

3 has a non-zero magnitude when the AC voltage causes

the potential at the first terminal 21 to be greater

than the potential at the second terminal 22 (i.e., in

the positive halves of the AC voltage as shown in FIG.

2), and has a zero magnitude when otherwise. In each

negative half of the AC voltage, the current signal has

a zero magnitude, the light signal generated by the

transmitter 41 of the feedback generator 4 has a zero

magnitude, the feedback signal has a zero current

magnitude, the voltage across the capacitor 916 is

pulled up by the resistor 915 to be equal in magnitude

to the power supply voltage, and the pulse signal as

shown in FIG. 5 is in the logic "1" state. In each

positive half of the AC voltage, since the resistance

provided by the adjustor 5 between the terminals 51,

52 is relatively large, the current signal has a

non-zero magnitude with a relatively small average, the

light signal generated by the transmitter 41 of the

feedback generator 4 has a non-zero intensity with a

relatively small average, the feedback signal has a

non-zero current magnitude with a relatively small

average, the voltage across the capacitor 916 is slowly

pulled down to be equal in magnitude to the ground

voltage, and switching of the pulse signal from the

logic "1" state to the logic "0" state considerably lags

a respective zero-crossing point of the AC voltage.

Regardless of the state of the adjustor 5, the control module 911 can determine, based on the pulse signal, whether the AC voltage is stably supplied. The control module 911 determines that the AC voltage is stably supplied when the pulse signal switches between the logic "1" state and the logic "0" state, and determines that the supply of the ACvoltage ceases when the pulse signal stays in the logic "1" state for more than a predetermined time.

When the supply of the AC voltage ceases because of

loss of the mains electricity, the control module 911

can detect the loss of the mains electricity based on

the pulse signal, and can execute apower-offprotection

procedure in a timely fashion. For example, the control

module 911 is powered by electricity stored in

capacitors (not shown) of the ceiling fan 9, and stores

current settings of the ceiling fan 9. After the mains

electricityis restored, the stored settings can be used

to recover the ceiling fan 9 to a condition immediately

prior to the loss of the mains electricity.

In view of the above, the zero-crossing detector of

this embodiment has the following advantages.

1. By virtue of the adjustor 5 adjusting the non-zero

magnitude of the current signal based on the control

signal such that the average of the non-zero magnitude

of the current signal is greater when the adjustor 5

is in the working state than when the adjustor 5 is in

the power saving state, power consumption of the ceiling fan 9 can be reduced to achieve power saving once the ceiling fan 9 enters the sleep mode.

2. When the ceiling fan 9 is in the sleep mode, since

the capacitor 916 is alternately discharged by the

receiver 42 of the feedback generator 4 and charged by

the resistor 915, the pulse signal still switches

between the logic "1" state and the logic "0" state,

and the control module 911 can learn the condition of

the AC voltage based on the pulse signal.

3. The configuration of the adjustor 5 is simple.

4. Since the resistance of the second resistive

element 54 is greater than the resistance of the first

resistive element 53, the resistance provided by the

adjustor 5 between the terminals 51, 52 can be much

greater when the adjustor 5 is in the power saving state

than when the adjustor 5 is in the working state, thereby

attaining better power saving effect.

In the description above, for the purposes of

explanation, numerous specific details have been set

forth in order to provide a thorough understanding of

the embodiment. It will be apparent, however, to one

skilled in the art, that one or more other embodiments

maybe practicedwithout some of these specificdetails.

It should also be appreciated that reference throughout

this specification to "one embodiment," "an

embodiment," an embodiment with an indication of an

ordinal number and so forth means that a particular

1 5

feature, structure, or characteristic may be included

in the practice of the disclosure. It should be further

appreciated that in the description, various features

are sometimes grouped together in a single embodiment,

figure, or description thereof for the purpose of

streamlining the disclosure and aiding in the

understanding of various inventive aspects.

The discussion of documents, acts, materials,

devices, articles and the like is included in this

specification solely for the purpose of providing a

context for the present invention. It is not suggested

or represented that any or all of these matters formed

part of the prior art base or were common general

knowledge in the field relevant to the presentinvention

as it existed before the priority date of each claim

of this application.

Where the terms "comprise", "comprises",

"comprised" or "comprising" are used in this

specification (including the claims) they are to be

interpreted as specifying the presence of the stated

features, integers, steps or components, but not

precluding the presence of one or more other features,

integers, steps or components, or group thereof.

Claims

1 6 The Claims defining the invention are as follows:

1. A zero-crossing detector to be installed in a

ceiling fan that includes a control unit, said

zero-crossing detector comprising:

a first terminal and a second terminal that are to

cooperatively receive an alternating current (AC)

voltage; and

a rectifier, an adjustor and a feedback generator

that are coupled in series between said first and second

terminals, that cooperatively provide a current path

between said first and second terminals, and that

cooperatively generate a current signal based on the

AC voltage;

said rectifier performing half-wave rectification

so that the current signal has a non-zero magnitude and

flows from said first terminal along said current path

to said second terminal when the AC voltage causes a

potential at said first terminal to be greater than a

potential at said second terminal, and has a zero

magnitude when otherwise;

said adjustor being adapted to be further coupled

to the control unit to receive a control signal, and

switching between a working state and a power saving

state based on the control signal to adjust the non-zero

magnitude of the current signal, an average of the

non-zero magnitude of the current signal being greater

when said adjustor is in the working state than when

1 7

said adjustor is in the power saving state;

said feedback generator being adapted to be further

coupled to the control unit, and generating a feedback

signal for receipt by the control unit based on the

current signal, the feedback signal having a

characteristic correlated to the magnitude of the

current signal, so as to indicate zero-crossing points

of the AC voltage.

2. The zero-crossing detector of claim 1, wherein:

said adjustor has two terminals that are located on

said current path, and provides, between said two

terminals ofsaid adjustor, aresistance thatis greater

in the power saving state than in the working state.

3. The zero-crossing detector of claim 2, wherein said

adjustor includes:

a first resistive element and a switch coupled in

series between said two terminals ofsaid adjustor, said

switch being adapted to be further coupled to the

control unit to receive the control signal, and

switching between conduction and non-conduction based

on the control signal; and

a second resistive element coupled between said two

terminals of said adjustor;

said adjustor being in the working state when said

switch conducts, and being in the power saving state when said switch does not conduct.

4. The zero-crossing detector of claim 3, wherein said

second resistive element has a resistance greater than

that of said first resistive element.

5. The zero-crossing detector of claim 3 or claim 4,

wherein said switch is one of an opto-isolator, a triac,

a silicon controlled rectifier, a metal oxide

semiconductor field effect transistor and a bipolar

junction transistor.

6. The zero-crossing detector of claim 3 or claim 4,

wherein:

said switch is an opto-isolator, and includes a

transmitter and a receiver;

said transmitter is adapted to be coupled to the

controlunit to receive the controlsignal, and converts

the control signal into a light signal; and

said receiver is coupled in series with said first

resistive element between said two terminals of said

adjustor, is to receive the light signal, and switches

between conduction and non-conduction based on the

light signal.

7. The zero-crossing detector of any one of claims 1

to 6, wherein said rectifier includes a diode that is

1 9

located on said current path.

8. The zero-crossing detector of any one of claims 1

to 7, wherein:

said feedback generator includes an opto-isolator;

said opto-isolator includes a transmitter and a

receiver;

said transmitter is located on said current path,

and converts the current signal into a light signal;

said receiver is adapted to be coupled to the control

unit, is to receive the light signal, and generates the

feedback signal for receipt by the control unit based

on the light signal.