EP0178852B1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Electronic ballast circuit for fluorescent lamps
Assignee: Advance Transformer Co
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Filing: 1985-10-10
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Granted: 1994-04-06
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Expires: 2005-10-10
Abstract
Abstract An electronic ballast circuit for fluorescent or other gaseous discharge lamps includes a resonant half-bridge inverter circuit. The source voltage to the inverter is a full-wave rectified line voltage together with a DC carry-over voltage for supplying power in the inter-cusp period of the rectified line voltage. A negative feedback circuit is responsive to lamp current to vary the inverter drive frequency and thereby regulate lamp current. The frequency response of the feedback loop is high enough and the gain-versus-frequency response of the inverter is such that lamp current and voltage are regulated to reduce the crest factor of lamp current to compensate for variation in the amplitude of the voltage across the semiconductor switches.
Inventors
- 👤 Calvin E. Grubbs
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 10:29
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/10; H02H7/12; H02H7/122; H02H7/1227; H05; H05B; H05B41/00; H05B41/14; H05B41/26; H05B41/28; H05B41/295; H05B41/298; H05B41/2981; H05B41/36; H05B41/38; H05B41/39; H05B41/392; Y; Y02; Y02B; Y02B20/00
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
230 words
An electronic circuit which can be used for energising a lamp circuit including at least one gaseous discharge lamp from a source of electrical power having a voltage amplitude varying in time, comprising inverter circuit means (110) which can be connected to receive power from said source and including first and second controlled switches (111 and 112), means (123) to gate said switches to conduction respectively in alternate cycles of inverter frequency thereby generating a high frequency electrical signal at an output (121) which can be connected to said lamp circuit to supply power thereto; sensing circuit means (142) which in use generates a control signal in response to lamp current; feedback control circuit means (127) which responds to said control signal to control the gating of the controlled switches thereby regulating lamp current to a predetermined value, characterised in that said inverter circuit means (110) includes a resonant circuit having a resonant frequency and connected to said output (121), said feedback control circuit means (127) including means which varies the frequency of conduction of said first and second controlled switches (111, 112) in relation to the resonant frequency of said inverter circuit means (110) and in response to said control signal representative of lamp current during normal operation thereby regulating output of said resonant circuit to regulate said lamp current and to reduce the crest factor of lamp current.
Claim 2
Dependent Claim
92 words
An energising circuit as claimed in claim 1 wherein the switches (111, 112) are connected in circuit with first and second capacitors (116, 117) to form a bridge circuit, the energising circuit comprising a power transformer (120) connected in the diagonal branch of the bridge circuit (110), the secondary winding (120 B) of the power transformer being adapted for coupling to the lamp through a capacitor (122), the inductance of said power transformer (120) and the value of said capacitor (122) at least partially determining the resonant frequency of said inverter circuit.
Claim 3
Dependent Claim
90 words
A circuit as claimed in claim 1 or claim 2 wherein said source of electrical power includes rectifier circuit means receiving power from a 60 Hz input line for generating electrical power for said inverter circuit (110) and a source of carry-over voltage storing energy when the output of said rectifier circuit means is sufficient to supply energy to said inverter circuit means and itself supplying energy to said inverter circuit means when the output of the rectifier circuit means is insufficient to supply energy to said inverter circuit means.
Claim 4
Dependent Claim
82 words
A circuit as claimed in any one of claims 1 to 3 wherein the range of operating frequencies of said resonant inverter circuit means as determined by said feedback control circuit means (127) is above the resonant frequency of said inverter circuit means and wherein said feedback control circuit means includes variable frequency oscillator circuit means responsive to said control signal for increasing the frequency of the drive signal to gate said controlled switches as lamp current increases from a reference value.
Claim 5
Dependent Claim
28 words
A circuit as claimed in claim 4 wherein said controlled switches are semi-conductor switches (111, 112) connected in series and energised to conduction in mutually exclusive time periods.
Claim 6
Dependent Claim
15 words
A circuit as claimed in claim 5 wherein said semiconductor switches are MOSFET transistors (111,112).
Claim 7
Dependent Claim
61 words
A circuit as claimed in any one of claims 1 to 6 comprising a phase detector which in use compares a first signal representative of the phase of lamp current and a second signal representative of the phase of applied lamp voltage for determining lamp voltage for determining when the operating frequency approaches said resonant frequency of said inverter circuit means.
Claim 8
Dependent Claim
69 words
A circuit as claimed in any one of claims 1 to 7 wherein said feeback control circuit further comprises a start-up voltage circuit responsive to initial application of power to said circuit thereby causing said variable frequency circuit means to operate at a high frequency and reduce the gain of said inverter circuit means for a predetermined time upon start-up to enable heating of the filaments of said lamp.
Claim 9
Dependent Claim
41 words
A circuit as claimed in any one of claims 1 to 8 wherein said feedback control circuit means (127) is responsive to the voltage applied to said lamps and increases the inverter frequency if the lamp voltage exceeds a predetermined value.
Claim 10
Dependent Claim
43 words
A circuit as claimed in any one of claims 1 to 9 wherein the feedback control circuit means (127) as a frequency response such that its -3db frequency point occurs at a frequency 5 KHz different from a resonant frequency of 50 KHz.
References Cited (Backward Citations)
No citation records indexed.
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