WO1999019977A2 - Converter/inverter full bridge ballast circuit - Google Patents
Converter/inverter full bridge ballast circuit Download PDFInfo
- Publication number
- WO1999019977A2 WO1999019977A2 PCT/US1998/021005 US9821005W WO9919977A2 WO 1999019977 A2 WO1999019977 A2 WO 1999019977A2 US 9821005 W US9821005 W US 9821005W WO 9919977 A2 WO9919977 A2 WO 9919977A2
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- inductive
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Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
- H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
- H05B41/282—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices
- H05B41/285—Arrangements for protecting lamps or circuits against abnormal operating conditions
- H05B41/2851—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions
- H05B41/2856—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions against internal abnormal circuit conditions
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- 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
- H02M1/00—Details of apparatus for conversion
- H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
- H02M1/4208—Arrangements for improving power factor of AC input
- H02M1/425—Arrangements for improving power factor of AC input using a single converter stage both for correction of AC input power factor and generation of a high frequency AC output voltage
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- 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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/538—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a push-pull configuration
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- 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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5383—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a self-oscillating arrangement
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- 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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5383—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a self-oscillating arrangement
- H02M7/53832—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a self-oscillating arrangement in a push-pull arrangement
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
- H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—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
Definitions
- the present invention relates generally to circuits for driving a load and more particularly to a lighting system circuit.
- a light source or lamp generally refers to an electrically powered man made element which produces light having a predetermined color such as white or near white.
- Light sources may be provided, for example, as incandescent light sources, fluorescent light sources and high-intensity discharge (HID) light sources such as mercury vapor, metal halide, high-pressure sodium and low-pressure sodium light sources.
- IFD high-intensity discharge
- ballast is a device which by means of inductance, capacitance or resistance, singly or in combination, limits a current provided to a light source such as a fluorescent or a HID light source.
- the ballast provides an amount of current required for proper lamp operation.
- the ballast may provide a required starting voltage and current. In the case of so-called rapid start lamps, the ballast heats a cathode of the lamp prior to providing a strike voltage to the lamp.
- one type of ballast is a so-called magnetic or inductive ballast.
- a magnetic ballast refers to any ballast which includes a magnetic element such as a laminated, iron core or an inductor.
- One problem with magnetic ballasts is that the relatively low frequency drive signal which they provide results in a relatively inefficient lighting system. Furthermore, magnetic ballasts tend to incur substantial heat losses which further lowers the efficiency of lighting systems utilizing a low frequency magnetic ballast.
- Electronic ballasts generally include a rectifier circuit for converting an alternating current (AC) input signal to a direct current signal (DC) and an inverter circuit to drive the load with an AC signal.
- the inverter circuit can be a circuit having resonant inductive, capacitive and resistive elements coupled in various parallel and/or series configurations to provide resonant operation of the circuit.
- Inverter circuits generally include switching elements arranged in a half or full bridge configuration with the switching elements controlled in various ways.
- U.S. Patent No. 5,220,247 discloses a conventional half bridge inverter circuit configuration having the switching elements controlled by inductors inductively coupled to the resonant inductive element.
- Conduction of the switching elements can be controlled with a pulse width modulation circuit as disclosed in U.S. Patent No. 4,415,839.
- U.S. Patent No. 5,434,477 discloses a half bridge inverter circuit coupled to a boost circuit having a switching element in common with the inverter circuit.
- the power supply can include a rectifier circuit. It will be appreciated that circuit components can be severely damaged in a short amount of time in the presence of such a short circuit. Even if cross conduction of multiple switching elements is prevented from a circuit operation standpoint, transients, electromagnetic interference (EMI) pulses, and other such events can result in cross conduction of switching elements. Furthermore, cross conduction prevention and/or protection schemes require additional circuit components thereby adding cost and increasing space requirements.
- EMI electromagnetic interference
- Another disadvantage associated with known electronic and magnetic ballast circuits is the output isolation transformer typically used to meet safety requirements.
- the load current must be limited, i.e., 43 mA at present, in the event that one end of a lamp is removed from the circuit to protect an operator from severe electrical shock.
- the isolation transformer is bulky and presents a significant cost in the manufacturing of a ballast.
- the present invention provides a circuit for driving a load.
- the load is primarily shown and described as a lamp, and in particular a fluorescent lamp, it is understood that the invention is applicable to a variety of circuits and circuit loads.
- a circuit for driving a load has a full bridge topology with a first bridge portion formed from a first switching element and a first current switch and a second bridge portion formed from a second switching element and a second current switch.
- First and second inductive elements divide the full bridge into the first and second portions and are effective to limit current during cross conduction of the first and second switching elements.
- the full bridge forms a portion of a resonant inverter circuit having resonant circuit elements including a resonant capacitive element, resistive element such as the load, and the first and second inductive elements.
- the first and second switching elements are biased into their states during conductive alternate cycles to thus energize the load.
- the manner in which the first and second inductive elements are coupled to the bridge limits the current to thus prevent the circuit elements from exposure to excessive amounts of current which could damage or destroy the circuit elements.
- a circuit for driving a load includes first and second converter circuits for receiving signal voltages at a first voltage level and providing signal voltages at a second higher voltage level to a power circuit, such as an inverter circuit.
- the first converter circuit includes a first switching element that forms a portion of the inverter circuit and the second converter circuit includes a second switching element that also forms a portion of the inverter circuit.
- a capacitive element forms a portion of the first and second converter circuits for charging and discharging by the converter circuits during resonant cycles.
- a common mode ground fault protection circuit includes a common mode inductive element for inductive coupling with an inductive element of an AC filter and a control circuit.
- the common mode inductive element detects common mode energy generated by a disruption in load return current.
- the control circuit provides an output signal to the power circuit to limit current to the load and thereby provide ground fault protection.
- the detected common mode energy i.e., longitudinal current
- load return current finding a path to earth ground other than the circuit path.
- One such path is through a technician in contact with the energized load, i.e., electrical shock.
- the common mode inductive element detects the current path disruption as a common mode voltage drop and the control circuit provides a signal to the power circuit to limit current to the load.
- FIG. 1 is a block diagram of a ballast circuit in accordance with the present invention
- FIG. 2 is a schematic diagram of the ballast circuit of FIG. 1;
- FIG. 3 is a schematic diagram showing the ballast circuit of FIG. 1 in further detail
- FIG. 4 is block diagram of a circuit for driving a load in accordance with the present invention
- FIG. 5 is a block diagram showing the circuit of FIG. 4 in further detail
- FIG. 6 is a schematic diagram of the circuit of FIG. 5;
- FIG. 6 A is a schematic diagram of an alternative embodiment of the circuit of FIG. 6;
- FIG. 6B is schematic diagram of a further alternative embodiment of the circuit of FIG. 6;
- FIG. 7 is block diagram of a circuit for providing ground fault protection in accordance with the present invention.
- FIG. 8 is a block diagram of the circuit of FIG. 7 shown in further detail
- FIG. 9 is a schematic diagram of the circuit of FIG. 8;
- FIG. 10 is a schematic diagram of the circuit of FIG. 9; and
- FIG. 10A is a further embodiment of the circuit of FIG. 10.
- FIG. 1 shows a ballast circuit 10 having first and second inputs 12,14 coupled to an alternating current (AC) power source 16 and first and second outputs
- the ballast 10 includes a rectifier circuit 24 to provide a direct current (DC) positive rail 26 and a negative rail 28.
- the rectifier circuit 24 is coupled to an inverter circuit 30 which provides AC energy at the first and second outputs 18,20 thereby energizing the load 22, which can be a fluorescent lamp.
- FIG. 2 shows an exemplary embodiment of the inverter circuit 30 of FIG. 1, wherein like elements have like reference numbers.
- the inverter circuit 30 receives DC power, i.e., from a rectifier, and outputs AC energy for energizing the load.
- the inverter circuit 30 is a self-resonating circuit providing an AC drive signal to the load 22.
- the inverter circuit 30 has resonant circuit elements including inductively coupled (i.e., on the same core) inductive elements LQ1 and LQ2, DC blocking capacitor CS, resonant capacitor CR, and the load 22, as shown.
- the inverter circuit 30 has a full bridge topology with a first bridge portion formed from diode Dl and switching element Ql and a second bridge portion formed from diode D2 and switching element Q2.
- the switching elements Ql, Q2 can be provided as bipolar junction transistors (BJTs) or field effect transistors
- transistors transistors.
- the conduction state of transistor Ql is controlled by a Ql control circuit 40 and the conduction state of transistor Q2 is controlled by a Q2 control circuit 42, as discussed below.
- the bridge, 43 formed from diodes Dl, D2 and switching elements Ql, Q2, is divided into the first and second portions by consecutively connected inductors
- inductors LQ1, LQ2 Connected between inductors LQ1, LQ2 is the DC blocking capacitor CS coupled in series with parallel connected capacitor CR and load 22.
- a capacitor Cl is coupled across the bridge as shown which charges and discharges energy as the circuit operates by providing an AC current path. Circuit resonance is initiated as the switching element Q2 is biased into its conduction state. Circuit start-up and control of the switching elements is discussed below. As Q2 becomes conductive, stored capacitive energy in CS in the form of current flows through inductor LQ2 and switching element Q2 to a negative of rail 44 of inverter 30. Since the circuit 30 operates in resonance, after a time the current will reverse direction.
- Switching element Q2 is biased into its non- conduction state so that the voltage drop across inductor LQ2 reverses thereby biasing diode Dl into conduction so that current flows to capacitor Cl.
- Diode D2 is also biased into conduction so that stored energy is damped in the load 22.
- the inverter circuit 30 operates in a repeating sequence of steps as shown in Table 1.
- the switching elements Ql and Q2 should not be conductive at the same time, i.e., cross conduct, since the positive and negative rails 46,44 would be effectively connected through inductors LQl and LQ2.
- the other switching element should not become conductive until the transistor has fully discharged.
- switching elements Ql and Q2 are controlled to prevent cross conduction, but transients or noise can produce simultaneous current flow through the switching elements Ql, Q2.
- the inductors LQl, LQ2 coupled across the bridge provide protection in the event that cross conduction of switching elements Ql, Q2 occurs.
- switching elements Ql, Q2 are provided as BJTs and are simultaneously conductive, current flows from an emitter of transistor Ql through inductor LQl, LQ2, to the collector of transistor Q2 to the negative rail 44.
- inductors LQl and LQ2 In addition to providing a resistance, inductors LQl and LQ2 also limit the current via the leakage inductance therebetween. That is, the respective windings of the inductive elements can be separated by a gap to provide a controlled leakage inductance to further limit the current. Thus, during cross conduction of switching elements Ql and Q2, inductors LQl and LQ2 provide a current limiting effect in the form of resistance and leakage inductance.
- FIG. 3 shows further details of inverter circuit 30 of FIG. 2 including exemplary embodiments for the switching elements Ql, Q2, control circuits 40,42, a start up circuit 50, and current limiting circuits formed from switching elements Q3, Q4.
- the start-up circuit 50 includes resistors RSU1, RSU2, diode D3, diac DD1 and capacitor C3.
- An additional resistor RSU3 can be coupled to the base of Q2 to facilitate charging of circuit elements such as capacitor CS.
- the circuit elements energize and the voltage at capacitor C3 increases to eventually cause conduction of diac DD1 and thereby turn on transistor Q2 to begin circuit resonance.
- an exemplary embodiment for the Ql control circuit 40 includes an RC network provided from resistor RQ1 and capacitor CQ1B coupled as shown, and a control element in the form of an inductor LQ1S inductively coupled with inductors LQl and/or LQ2.
- inductive elements LQl and LQ1S Looking to the winding polarities (i.e., the dot notations) of inductive elements LQl and LQ1S it can be seen that as switching element Ql conducts a current though inductor LQl there is a positive voltage drop across inductors LQl and LQ1S.
- switching element Ql is provided as a BJT
- LQ1S provides a positive voltage at the base of transistor Ql biasing transistor Ql into its conduction state.
- the LQl S voltage drop reverses to cause transistor Ql to turn off.
- the RC network provides a delay time that corresponds to the time required for Q2 to discharge after turning off.
- the positive voltage drop across LQIS does not turn Ql on until Q2 has fully discharged.
- the Q2 control circuit 42 is similar to that of the Ql control circuit 40 and includes an RC network of RQ2 and CQ2B and a control element in the form of inductive element LQ2S coupled to the base of Q2.
- LQ2S is inductively coupled to LQl and/or LQ2.
- the RC network provides a delay longer than the time required for Ql to fully discharge. Thus, the delay prevents the LQ2S voltage drop from immediately turning on Q2 after Ql turns off. Looking again to the winding polarities of LQIS and LQ2S in conjunction with LQl and LQ2, the Ql and Q2 control circuits 40,42 tend to avoid cross conduction of Ql and Q2.
- the switching elements Q3 and Q4 provide a means to limit the current through respective switching elements Ql and Q2. Coupled to the base of Ql is the collector C of Q3 with the base B of Q3 coupled to the emitter of Ql through resistor RQ3B. A resistor RQ1E is coupled at a first terminal to the emitter of Ql and the emitter of Q3 at the other terminal as shown. When the current through Ql and RQ1E is sufficient to overcome the Q3 base to emitter voltage drop, Q3 effectively turns Ql off and prevents current flow. Ql remains turned off until the current through Q3 is less than a predetermined level.
- the network of Q4, RQ4B, and RQ2E are coupled in a manner as described above in conjunction with Q3.
- Q4 is effective to limit current through Q2 to a predetermined level. It is understood that the current through Ql and Q2 can be limited to the same or a different amount. It is further understood that one of ordinary skill in the art can readily modify the disclosed circuit to select a desired limiting current level.
- FIG. 4 a circuit 100 for driving a load in accordance with the present invention is shown.
- the circuit 100 includes a first converter circuit 102 and a second converter circuit 104 coupled to an AC power source 106 as shown.
- the first and second converter circuits 102,104 are coupled to a circuit 108 including a load 110.
- the converter circuits provide power factor (PF) correction and total harmonic distortion (THD) correction.
- PF power factor
- TDD total harmonic distortion
- FIG. 5 shows one particular embodiment of a circuit for driving a load including a ballast circuit 110 having first and second terminals 112,114 coupled to an AC power source 116.
- the ballast circuit 110 includes a rectifier circuit 118 receiving the AC energy and providing DC positive and negative rails 120,122.
- the positive rail 120 is coupled to a first converter circuit 124 and the negative rail 122 is coupled to a second converter circuit 126.
- the first and second converter circuits 124,126 are coupled to and form portions of an inverter circuit 128 for energizing a load 130 with AC energy.
- FIG. 6 shows an exemplary embodiment of the ballast circuit 100.
- the rectifier circuit 118 is formed from diodes Da-Dd as shown to provide a conventional bridge rectifier with positive rail 120 and negative rail 122.
- a capacitor C2 can be coupled across the positive and negative rails 120,122 to filter the signal.
- the first converter circuit 124 includes a first converter inductor LB1, diode Dl, switching element Ql and capacitor Cl.
- LB 1 has a first terminal coupled to the positive rail 120 and a second terminal coupled to diode Dl as shown.
- the second converter circuit 126 includes a second converter inductor LB2, diode D2, switching element Q2 and capacitor Cl.
- LB1 and LB2 are loosely inductively coupled to provide circuit control as discussed below, but can be independent elements. It is understood that the dual converter circuit configuration is described in conjunction with a circuit similar to that shown and described in FIG. 3 to facilitate an understanding of the invention. Thus, the dual converter configuration is not to be limited to the particular embodiments shown and described herein. Furthermore, operation of the inverter circuit 128 is described in detail above in conjunction with FIG. 3, and therefore, is not repeated here.
- the first converter circuit 124 and the inverter circuit 128 have circuit elements in common, including Ql, Dl and Cl.
- the second converter circuit 126 and the inverter circuit 128 have Q2, D2 and Cl in common.
- the inverter circuit 128 resonates so that current periodically reverses direction through the load.
- Q2 in a conductive state.
- Current flows from the positive rail 120 of the rectifier circuit through LBl and Q2 to a negative rail 140 of the inverter circuit 128.
- Dl and D2 become conductive to provide a current path to Cl and the negative rail 140 of the inverter until Ql turns on.
- current flows though LB2 as Ql conducts and Dl and D2 conduct between the time that Ql turns off and Q2 turns on.
- Ql control circuit 150 further includes inductive element LBSl coupled in parallel with LQIS.
- Q2 control circuit 152 includes LBS2. Examining the dot notation shows that as Q2 conducts, the voltage drop across LBS2 biases Q2 on and LBSl biases Ql off.
- LBS2 biases Q2 off and LBSl biases Ql on.
- LBl and LB2 provide a more efficient switching of Ql and Q2.
- LBSl and LBS2 without LQIS and LQ2S, can control Ql and Q2 switching and vice-versa.
- FIG. 6 A shows an alternative embodiment of the circuit of FIG. 6 further including diode D3 and diode D4.
- Diode D3 has an anode coupled to inductor LQ2 and cathode coupled to the bridge between the collector of Q2 and Dl.
- Diode D4 has an anode coupled to the bridge at a point between diode D2 and the emitter of Ql.
- Diode D3 is effective to prevent the flow of current from LBl to LQ2. Without the diode D3, current may flow into LQ2 while Q2 is off and the voltage at the positive rail 141 of the inverter is present at the collector of Q2. Similarly, D4 prevents current flow from LB2 to LQl thereby eliminating parasitic circuit effects from such a current. It is understood that inductors LBl and LB2 can have a relatively loose inductive coupling to provide an energy release path when Q2 and Ql respectively terminate conduction. The diodes D3 and D4 provide enhanced circuit control and more clearly define the alternating Ql, Q2 conduction cycles.
- FIG. 6B shown another embodiment of FIG. 6 with diode D3 coupled between inductor LBl and the bridge and diode D4 coupled between the bridge and inductor LB2.
- diodes D3 and D4 prevent current flow to inductors LQ2 and LQl respectively after the switching elements Q1,Q2 are biased to the non-conduction state.
- FIG. 7 shows a power generating station 200 providing AC power to a power circuit 202 for driving a load 204.
- the power generating station 200 can be a regional substation for generating electricity for consumer use.
- FIG. 8 shows a common mode detector circuit 206 coupled to an AC energy source 208, such as power generating station 200.
- the common mode detector circuit 206 is coupled to an inverter circuit 210, such as the inverter circuits described above, for energizing the load 204.
- the load can be one or more fluorescent lamps.
- FIG. 9 shows an exemplary embodiment of the common mode detector circuit 206 including an 212 and control circuit 214 coupled to the inverter circuit 210 which drives the load 204.
- the AC power source 208 is coupled to the inverter circuit 210 through first and second common mode inductive elements 216,218 for power factor correction and EMI control.
- the inductive element 212 is inductively coupled with the first and second common mode inductive elements 216,218 for detecting common mode energy from the AC power source 208. Common mode energy appears as a voltage drop across the inductive element 212. As the control circuit 214 detects the common mode voltage drop an output signal 220 to the inverter circuit 210 is activated for limiting the current to the load 204.
- FIG. 10 is an exemplary embodiment of a common mode ground fault protection (CMGFP) scheme in accordance with the present invention. It is understood that this ground fault protection scheme is described in conjunction with above described inverter circuits to facilitate an understanding of the invention. It is further understood that one of ordinary skill in the art can readily modify the described embodiments for other applications of the ground fault circuit of the present invention and fall within the scope and spirit of the appended claims.
- CMGFP common mode ground fault protection
- FIG. 10 shows AC input terminals 230,232 coupled to a rectifier circuit 234 for providing DC power to an inverter circuit 236 to drive load 238.
- the load 238 can be a fluorescent lamp energized with AC energy by the inverter circuit 236.
- the inverter circuit 236 operates as described in detail above.
- An AC filter 240 comprising inductively coupled first and second common mode inductive elements 242,244 and filter capacitor CF 246 are coupled to the AC power terminals 230,232 as shown.
- a first inductor 248 is inductively coupled with the first and second common mode inductive filter elements 242,244.
- a first terminal 250 of the first inductor 248 is connected to a negative rail 252 of the inverter circuit 236, i.e., the load return, and a second terminal 254 is coupled to a control circuit 256.
- the control circuit 256 provides an output signal to the base of Q4 to selectively disable Q4 and interrupt current flow in the circuit. It is readily apparent that other circuit nodes can be controlled by the control circuit 256 to disable current flow.
- An optional second inductor 260 can be inductively coupled with the first and second inductive filter elements 242,244 in a manner similar to that of the first inductor 248.
- the second inductor 260 is connected to a second control circuit 262 which is coupled to the base of Q3 to selectively disable Q3.
- the ground fault protection circuit of the present invention detects a common mode signal and limits current through a load to reduce electrical shock injuries.
- an output isolation transformer is generally used to limit current through the load and thereby provide ground fault protection. More particularly, where an operator removes one end of an energized lamp, the operator can undesirably provide a current path to ground. That is, the operator can suffer an electrical shock that can be fatal with sufficient current flow. Thus, to limit the current, the isolation transformer is used. However, the isolation transformer makes the circuit less efficient, more costly, and less compact.
- the ground fault protection circuit of the present invention detects common mode energy.
- the detected common mode energy i.e., longitudinal current
- the disruption can be constituted by load return current finding a path to earth ground other than the circuit path, such as through a technician in contact with the energized load.
- FIG. 10A shows a further embodiment of the ground fault protection circuit of FIG. 10 where like reference numbers represent like elements.
- the circuit includes a first common mode capacitor CCM1 coupled across the first and second inductive elements 242,244 and a second common mode capacitor CCM2 connecting the capacitor CCM1 to ground as shown.
- the capacitors CCM1 and CCM2 provide an AC signal path to ground and provide EMI filtering for longitudinal currents generated by the ballast flowing to the supply lines.
- standard electrical wiring provides that each electrical outlet box be connected to ground to prevent electrical shock.
- the ground connection is generally not necessary for operation of electrical devices. However, where a ground connection for the box is broken or missing, a safety hazard exists that is not readily detectable. That is, the box can be energized and shock a user upon contact with the box.
- the common mode capacitors CCM1 and CCM2 also provide the inductor element 248 with better sensitivity to incoming common mode energy by eliminating the common mode signal generated by the ballast circuit before it reaches the inductor element 248.
- control circuit 256 includes an audible or visible alarm to provide a warning that a hazardous condition exists.
- the warning signal can be sent along the supply lines.
- a warning signal may flow to a central station to alert a security guard or other interested parties.
- the warning signal can be sent as a high frequency signal through the power supply lines.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP98950940A EP1020016A2 (en) | 1997-10-10 | 1998-10-07 | Converter/inverter full bridge ballast circuit |
AU96853/98A AU9685398A (en) | 1997-10-10 | 1998-10-07 | Converter/inverter full bridge ballast circuit |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US08/948,690 US6020688A (en) | 1997-10-10 | 1997-10-10 | Converter/inverter full bridge ballast circuit |
US08/948,690 | 1997-10-10 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO1999019977A2 true WO1999019977A2 (en) | 1999-04-22 |
WO1999019977A3 WO1999019977A3 (en) | 1999-06-17 |
Family
ID=25488151
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1998/021005 WO1999019977A2 (en) | 1997-10-10 | 1998-10-07 | Converter/inverter full bridge ballast circuit |
Country Status (4)
Country | Link |
---|---|
US (2) | US6020688A (en) |
EP (1) | EP1020016A2 (en) |
AU (1) | AU9685398A (en) |
WO (1) | WO1999019977A2 (en) |
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2000
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Also Published As
Publication number | Publication date |
---|---|
US6020688A (en) | 2000-02-01 |
EP1020016A2 (en) | 2000-07-19 |
WO1999019977A3 (en) | 1999-06-17 |
AU9685398A (en) | 1999-05-03 |
US6281638B1 (en) | 2001-08-28 |
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