USOO70O2819B1
`
`(12) United States Patent
`Chan et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,002,819 B1
`Feb. 21, 2006
`
`(54) HALF-BRIDGE INVERTER
`(75) Inventors: Chun-Kong Chan, Hsi Chih (TW);
`Jeng-Shong Wang, Hsin Chuang (TW)
`
`(*) Notice:
`
`(73) Assignee: Lien Chang Electronic Enterprise
`Co., Ltd., Taipei (TW)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`(21) Appl. No.: 11/068,790
`(22) Filed:
`Mar. 2, 2005
`(51) Int. Cl.
`(2006.01)
`H04M 7/5387
`(52) U.S. Cl. ...................................................... 363/132
`(58) Field of Classification Search .................. 363/95,
`363/97, 131, 132; 315/306, 307, 308
`See application file for complete Search history.
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`3,978,390 A * 8/1976 Remery ...................... 363/131
`4,156.273 A * 5/1979 Sato ........................ 363/21.16
`4,745,537 A * 5/1988 Cheung ....................... 363/37
`5.449979 A * 9/1995 Ueoka et al. ............... 315/225
`
`sk -
`
`5,563,777 A * 10/1996 Miki et al..................... 363/37
`5,615,093 A
`3/1997 Nalbant
`cited by examiner
`Primary Examiner-Adolf Berhane
`(74) Attorney, Agent, or Firm-Rosenberg, Klein & Lee
`
`57
`(57)
`
`ABSTRACT
`
`A half-bridge inverter achieves an inversion by Switching an
`external-driven Switch and a Self-driven Switch, and includes
`a transformer having a primary winding, a Secondary wind
`ing and an auxiliary winding. The external-driven Switch
`coupled to the first winding and ground is controlled by a
`Square wave signal. The Self-driven Switch coupled to the
`primary winding, auxiliary winding and a DC power Supply
`is controlled by an output voltage of the auxiliary winding.
`A resonant capacitor is coupled to the Secondary winding.
`The Square wave signal controls the Switching of the exter
`nal-driven Switch, and the Switching of the self-driven
`Switch controlled by the output voltage of the auxiliary
`winding introduces DC power into the primary winding of
`the transformer while Sensing an alternating Voltage at the
`Secondary winding of the transformer. A resonant capacitor
`filters harmonic waves into low-noise AC power to reduce
`interferences and Supply power to a load.
`
`7 Claims, 6 Drawing Sheets
`
`
`
`Vo
`
`C2 Vac
`
`C3
`
`CCFL
`
`GOOGLE AND SAMSUNG EXHIBIT 1012, 0001
`
`

`

`U.S. Patent
`
`US 7,002,819 B1
`
`10
`
`r- - -------
`
`
`
`FIG. 1
`PRIOR ART
`
`GOOGLE AND SAMSUNG EXHIBIT 1012, 0002
`
`

`

`U.S. Patent
`
`Feb. 21, 2006
`
`Sheet 2 of 6
`
`US 7,002,819 B1
`
`
`
`D2
`
`(t)
`
`Ct)
`
`dead time
`
`FIG. 2
`PRIOR ART
`
`GOOGLE AND SAMSUNG EXHIBIT 1012, 0003
`
`

`

`U.S. Patent
`
`Feb. 21, 2006
`
`Sheet 3 of 6
`
`US 7,002,819 B1
`
`O
`
`- S
`
`er
`O
`
`O
`
`CN
`C
`
`S
`
`a.
`
`
`
`g
`
`GOOGLE AND SAMSUNG EXHIBIT 1012, 0004
`
`

`

`U.S. Patent
`
`Feb. 21, 2006
`
`Sheet 4 of 6
`
`US 7,002,819 B1
`
`VDCo-
`
`Cl
`
`Vo
`
`Q1
`
`FIG. 4A
`
`Tr
`
`W
`O
`
`VDC
`
`C1
`
`ca)
`
`CQ1
`
`FIG. 4B
`
`W
`O
`
`VDC
`
`C1
`
`Tr
`
`DQ2 ) I
`
`FIG. 4C
`
`GOOGLE AND SAMSUNG EXHIBIT 1012, 0005
`
`

`

`U.S. Patent
`
`Feb. 21, 2006
`
`Sheet 5 of 6
`
`US 7,002,819 B1
`
`VDC
`
`C1
`
`T
`
`W
`O
`
`
`
`GOOGLE AND SAMSUNG EXHIBIT 1012, 0006
`
`

`

`U.S. Patent
`
`Feb. 21, 2006
`
`Sheet 6 of 6
`
`US 7,002,819 B1
`
`a N
`-)
`N/
`
`a N
`-
`Nu1
`
`E
`
`D)
`
`GOOGLE AND SAMSUNG EXHIBIT 1012, 0007
`
`

`

`1
`HALF-BRIDGE INVERTER
`
`US 7,002,819 B1
`
`BACKGROUND OF THE INVENTION
`
`15
`
`25
`
`1. Field of the Invention
`The present invention relates to a half-bridge inverter, and
`more particularly to a half-bridge inverter that accomplishes
`an inversion by Switching an external-driven Switch and a
`Self-driven Switch.
`2. Description of Related Art
`AS electronic and computer devices are increasingly com
`plicated, a power Supply device becomes more important
`than ever. A power Supply device can be divided into two
`main types: a linear type and a Switching type. Since the
`linear type is less advantageous than the Switching type,
`therefore, most power Supply devices are the Switching type.
`The power Supply for a backlight Source of a thin film
`transistor (TFT) panel mainly uses a DC-AC inverter circuit
`to achieve the power conversion and drive a cold cathode
`fluorescent lamp (CCFL) to illuminate. With a different
`circuit topology, a conventional prior type of inverter circuit
`is generally divided into a half-bridge inverter circuit, a
`full-bridge inverter circuit, and a push-pull inverter circuit,
`which are inverter circuits for converting direct current (DC)
`into alternate circuit (AC).
`U.S. Pat. No. 5,615,093 discloses a half-bridge inverter
`circuit. Referring to FIG. 1, a Schematic circuit diagram of
`a half-bridge inverter circuit driving a load is illustrated. In
`FIG. 1, a transformer T1 divides a circuit into a primary
`circuit and a Secondary circuit, and a feedback network 30
`is connected between these two circuits. The primary circuit
`comprises a direct current power supply VDD, two elec
`tronic switches Q1, Q2, a half-bridge control chip 10 and a
`LCC resonant network 40, and the secondary circuit com
`prises a lamp load 20. With reference to FIG.2 together with
`35
`FIG. 1, Schematic views of the output control Signal of a
`half-bridge control chip and the Voltage waveform of an
`alternate current (AC) according to a prior art are illustrated.
`The half-bridge control chip 10 uses two output ends
`LFET1, LFET2 to output control signals D1, D2, and the
`control Signals D1, D2 respectively control the Switching of
`two electronic Switches Q1, Q2. By Switching the two
`electronic Switches Q1, Q2, the electric power of the direct
`current (DC) power Supply is Supplied to the primary
`winding of the transformer T1 through the LCC resonant
`network 40 to define an AC power supply ac. The AC power
`Supply ac is provided for Supplying power to the transformer
`T1, and the transformer T1 steps up and converts the AC
`power to the Secondary winding for driving the lamp load
`2O.
`In the foregoing description, the half-bridge inverter cir
`cuit disclosed in the U.S. Pat. No. 5,61.5,093 requires a
`half-bridge control chip 10 having at least two outputs to
`drive directly the electronic switches Q1, Q2 and control the
`alternating connection of the Switches Q1, Q2. Further, the
`half-bridge control chip 10 also needs to control the first
`Switch O1 and the second Switch O2 to alternate for a short
`time by turning the Switches on and off alternatingly. There
`fore, it is necessary to have a little dead time for the control
`signals D1, D2 as shown in FIG. 2 to avoid a concurrent
`electric connection of the first Switch O1 and the second
`Switch Q2, which will destroy both the first Switch Q1 and
`the second Switch O2.
`Further, the control Signals D1, D2 need to change the
`Signal cycle and control the Switching of the first Switch Q1
`and the Second Switch Q2 to Supply the electric power for the
`load according to the power requirement of the lamp load
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`20. The half-bridge control chip 10 needs to protect the
`circuit according to the conditions fed back from the load
`end, Such as the condition of a too-low Voltage output, a
`too-high Voltage output, an open circuit of the lamp or
`overheat etc. The output of the control signal D1, D2 is
`terminated to Switch off the first Switch O1 and the second
`Switch Q2 to achieve a circuit protection function.
`AS described above, the conventional prior half-bridge
`inverter circuit comes with a half-bridge control chip 10
`having two drive signals for driving the half-bridge circuit.
`Meanwhile, a protect circuit is needed to protect the Sec
`ondary circuit of the transformer. Such requirement causes
`a high cost and an excessively large size of the product.
`
`SUMMARY OF THE INVENTION
`
`Therefore, it is a primary objective of the present inven
`tion to provide a half-bridge inverter that achieves an
`inversion by using any PWM integrated circuit and Switch
`ing an external-driven Switch and a Self-driven Switch. The
`external-driven Switch is controlled by a Square wave signal
`and works together with the self-driven Switch for convert
`ing a DC power Supply into an alternate current power and
`Supplying the power for at least one lamp.
`The present invention comprises a transformer having a
`primary winding, a Second winding and an auxiliary wind
`ing. The transformer is coupled to the external-driven
`Switch. The external-driven Switch is coupled to the primary
`winding of the transformer and ground and controlled by the
`Square wave Signal. The Self-driven Switch is coupled to the
`primary winding, the auxiliary winding and the direct cur
`rent power supply of the transformer and controlled by an
`output Voltage of the auxiliary winding. A resonant capacitor
`is coupled to the Secondary winding. Therefore, the present
`invention uses the Square wave Signal to control the Switch
`ing of the external-driven Switch and the output Voltage of
`the auxiliary winding to control the Switching of the Self
`driven Switch. By alternately Switching the Switches, a direct
`current power Supply is introduced to the primary winding
`of the transformer while Sensing an alternating Voltage at the
`Second winding of the transformer. The alternating Voltage
`is converted into alternating current power through the
`resonant capacitor. Further, the external-driven Switch of the
`invention includes a first polar capacitor (or an additional
`capacitor) and a first interface diode (or an additional diode)
`between two output gates in the external-driven Switch. The
`Self-driven Switch of the invention includes a Second polar
`capacitor (or an additional capacitor) and a second interface
`diode (or an additional diode) between two output gates in
`the Self-driven Switch. Therefore, the Square wave signal and
`the output voltage of the auxiliary winding respectively
`control the Switching of the external-driven switch and the
`Self-driven Switch to charge or discharge the polar capacitor
`(or an additional capacitor) and the Second polar capacitor
`(or an additional capacitor) by the DC power Supply. The
`charging/discharging power is Supplied to the primary wind
`ing of the transformer while Sensing an alternating Voltage
`at the Secondary winding of the transformer and converted
`into the AC power by the resonant capacitor.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The foregoing aspects and many of the attendant advan
`tages of this invention will be more readily appreciated as
`the same becomes better understood by reference to the
`following detailed description, when taken in conjunction
`with the accompanying drawings, wherein:
`
`GOOGLE AND SAMSUNG EXHIBIT 1012, 0008
`
`

`

`3
`FIG. 1 is a Schematic circuit diagram of a half-bridge
`inverter circuit driving a load according to the prior art;
`FIG. 2 is a Schematic diagram of an output control Signal
`of a half-bridge control chip and a Voltage waveform of an
`alternate current power Supply according to the prior art;
`FIG. 3 is a Schematic circuit diagram of a half-bridge
`inverter circuit driving a load according to the present
`invention;
`FIGS. 4A to 4F are schematic diagrams illustrating the
`actions taken in a cycle of a circuit according to the present
`invention; and
`FIG. 5 is a Schematic diagram of a waveform in a cycle
`of a circuit according to the present invention.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`15
`
`Reference to FIG. 3 is made for a schematic circuit
`diagram of a half-bridge inverter in accordance with the
`present invention. A half-bridge inverter of the invention is
`controlled by a Square signal Se for converting DC power
`supply VDC into AC power supplied for the use of at least
`one cold cathode fluorescent lamp (CCFL). The half-bridge
`inverter comprises a primary winding Np, a Secondary
`winding NS and an auxiliary winding Na of a transformer Tr.
`An external-driven Switch Q1 is coupled to the primary
`winding Np and ground G and controlled by the Square wave
`Signal Se. A Self-driven Switch Q2 is coupled to the
`primary winding Np, the auxiliary winding Na and the direct
`current power supply VDC and controlled by an output
`Voltage of the auxiliary winding Na. A resonant capacitor is
`coupled to the secondary winding Ns.
`With the Switching of the external-driven Switch Q1
`controlled by the Square wave signal Sea and the Switch
`ing of the self-driven Switch Q2 controlled by the output
`Voltage of the auxiliary winding Na, the DC power Supply
`VDC is introduced to the primary winding Np of the
`transformer Tr while an alternating Voltage is Sensed at the
`secondary winding Ns of the transformer Tr, and then
`converted into the AC power by the resonant capacitor C3.
`Referring to FIG. 3 again, the present invention further
`comprises a fast diode D1 coupled to a control end of the
`external-driven Switch Q1 for Suppressing the current pass
`ing through the control end when the external-driven Switch
`Q1 is electrically connected and accelerating to turn off the
`external-driven Switch O1 while the external-driven Switch
`Q1 is being turned off. A second accelerated diode D2 is
`coupled to a control end of the self-driven Switch Q2 and the
`auxiliary winding Na for Suppressing the current passing
`through the control end when the self-driven Switch Q2 is
`electrically connected and accelerating to turn off the Self
`driven Switch Q2 while the self-driven Switch Q2 is being
`turned off. In the foregoing description, the external-driven
`switch Q1 is an N-channel field effect transistor (FET)
`having a first polar capacitor CQ1 (or an additional capaci
`tor) and a first interface diode (or an additional diode)
`disposed between two output gates of the external-driven
`Switch. Further, the self-driven Switch O2 is an N-channel
`field effect transistor (FET) having a Second polar capacitor
`CQ2 (or an additional capacitor) and a second interface
`diode (or an additional diode) disposed between two output
`gates of the Self-driven Switch.
`Reference is made to FIGS. 4A to 4F for Schematic views
`of the actions taken in a cycle of a circuit in accordance with
`the present invention, while referring to FIG. 5 simulta
`neously for a Schematic diagram of the waveform in a cycle
`of a circuit of the invention. During period I, the Square
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`US 7,002,819 B1
`
`4
`wave Signal Se is high, and the external-driven Switch Q1
`at that time is turned ON by the control of the square wave
`Signal Sr. and the Self-driven Switch Q2 is turned OFF.
`Therefore, the DC power supply VDC provides a path
`through the capacitor C1 and transformer Tr to the external
`driven Switch O1, the current is stored in the transformer Tr,
`and a positive alternating Voltage Vo is Sensed by the
`secondary winding Ns of the transformer Tr.
`During period II, the Square Wave signal Sea is turned
`OFF by the control of the external-driven Switch Q1, and the
`self-driven Switch Q2 remains OFF. By that time, the electric
`power temporarily Stored in the Second polar capacitor CO2
`or additional capacitor of the self-driven switch Q2 will be
`discharged, and the current Stored in the transformer Tr will
`charge the first polar capacitor CQ1 or additional capacitor
`in the external-driven Switch Q1. Thus, the alternating
`voltage Vo of the secondary winding Ns of the transformer
`Tr is at a low voltage.
`During period III, both of the external-driven Switch Q1
`and the self-driven Switch still remain OFF. When the first
`polar capacitor CO1 or the additional capacitor is charged up
`to the voltage of the DC power Supply VDC, and the second
`polar capacitor CO2 or additional capacitor is discharged to
`Zero Voltage, the Second interface diode DO2 or additional
`diode is turned ON and the self-driven Switch Q2 is Switched
`to Zero Voltage. Therefore, the alternating Voltage Sensed by
`the secondary winding Ns of the transformer Tr is at a
`negative alternating Voltage Vo Status.
`During period IV, the self-driven Switch Q2 is turned ON
`by the control of the auxiliary winding Na of the transformer
`Tr. By that time, the direction of the current passing through
`the primary winding Np of the transformer Tr is reversed,
`and the energy will be accumulated in the transformer Tr. In
`this period, the alternating Voltage Sensed by the Secondary
`winding NS of the transformer Tris at a negative alternating
`Voltage Status.
`During period V, the self-driven Q2 is Switched OFF, and
`the external-driven Switch Q1 still remains OFF. By that
`time, the first polar capacitor CO1 or additional capacitor in
`the external-driven Switch Q1 discharges the temporarily
`Stored electric power, and the current Stored in the trans
`former will charge the Second polar capacitor CO2 or
`additional capacitor in the self-driven Switch Q2. Therefore,
`the alternating Voltage Vo Sensed by the Secondary winding
`Ns of the transformer Tr is at a rising Voltage Status.
`During period VI, if the Second polar capacitor CO2 or
`additional capacitor is charged up to the Voltage of the DC
`power supply VDC and the first polar capacitor CQ1 or
`additional capacitor is discharged to Zero Voltage, then the
`first interface diode DO1 or additional diode will be turned
`ON. By that time, the external-driven Switch Q1 is switched
`to Zero Voltage. Therefore, the alternating Voltage Sensed by
`the secondary winding Ns of the transformer Tr is at a
`positive alternating Voltage Vo Status.
`In the description above, the operation of the circuit
`returns to Period I after Period VI is finished to complete a
`cycle. The waveform of the alternating Voltage Vo output in
`the cycle of the circuit is converted into the AC power Vac
`by the resonant capacitor C3. Therefore, the present inven
`tion can achieve an inversion according to the cycle of the
`foregoing circuit. Furthermore, the present invention only
`needs a Square signal to drive the half-bridge circuit. If a
`Short circuit or any other failure occurs at the Secondary
`winding of the transformer, the self-driven Switch Q2 cannot
`continue its operation. The present invention does not
`
`GOOGLE AND SAMSUNG EXHIBIT 1012, 0009
`
`

`

`S
`require an additional peripheral circuit to achieve the circuit
`protection, and thus can reduce the manufacturing cost and
`the size of the product.
`While the invention has been described in terms of what
`is presently considered to be the most practical and preferred
`embodiments, it is to be understood that the invention needs
`not be limited to the disclosed embodiment. On the contrary,
`it is intended to cover various modifications and Similar
`arrangements included within the Spirit and Scope of the
`appended claims which are to be accorded with the broadest
`interpretation So as to encompass all Such modifications and
`Similar Structures.
`What is claimed is:
`1. A half-bridge inverter, controlled by a Square wave for
`converting a direct current power Supply into an alternate
`current power for the use of at least one lamp, comprising:
`a transformer, having a primary winding, a Secondary
`winding and an auxiliary winding,
`an external-driven Switch, being coupled to Said primary
`winding and ground and controlled by Said Square
`control Signal;
`a Self-driven Switch, being coupled to Said primary wind
`ing, Said auxiliary winding and Said direct current
`power Supply and controlled by an output Voltage of
`Said auxiliary winding, and
`a resonant capacitor, being coupled to Said Secondary
`winding,
`wherein Said Square signal controls a Switching of Said
`external-driven Switch and Said output voltage of Said
`auxiliary winding controls a Switching of Said Self
`driven Switch introducing Said direct current power
`supply into said primary winding of said transformer,
`while an alternating Voltage is Sensed by Said Secondary
`winding of Said transformerS Senses and converted into
`alternate current power by Said resonant capacitor.
`
`15
`
`25
`
`US 7,002,819 B1
`
`6
`2. The half-bridge inverter of claim 1, further comprising
`a first fast diode coupled to a control end of Said external
`driven Switch for Suppressing the current at Said control end
`to pass through when Said external-driven Switch is electri
`cally connected, and accelerating to turn off Said external
`Switch when said external Switch is being turned off.
`3. The half-bridge inverter of claim 1, further comprising
`a Second accelerated diode coupled to Said control end of
`Said Self-driven Switch and Said auxiliary winding for Sup
`pressing the current at Said control end to pass through when
`Said Self-driven Switch is electrically connected, and accel
`erating to turn off said self-switch when said self switch is
`being turned off.
`4. The half-bridge inverter of claim 1, wherein said
`external-driven Switch is an N-channel field effect transistor
`and includes a first polar capacitor and a first interface diode
`disposed between two output gates in Said external-driven
`Switch.
`5. The half-bridge inverter of claim 1, wherein said
`external-driven Switch is an N-channel field effect transistor
`and includes a capacitor and a diode disposed between two
`output gates in Said external-driven Switch.
`6. The half-bridge inverter of claim 1, wherein said
`Self-driven Switch is an N-channel field effect transistor and
`includes a Second polar capacitor and a Second interface
`diode disposed between two output gates in Said Self-driven
`Switch.
`7. The half-bridge inverter of claim 1, wherein said
`Self-driven Switch is an N-channel field effect transistor and
`includes a capacitor and a diode disposed between two
`output gates in Said Self-driven Switch.
`
`GOOGLE AND SAMSUNG EXHIBIT 1012, 0010
`
`