Ballast control IC with minimal internal and external components

• US 20050007037A1
• Filed: 07/27/2004
• Published: 01/13/2005
• Est. Priority Date: 06/19/2000
• Status: Active Grant

• Current Assignee: International Rectifier Corporation (Infineon Technologies AG)
• Original Assignee: International Rectifier Corporation (Infineon Technologies AG)
• Inventors: Ribarich, Thomas J.
• Granted Patent: US 7,420,338 B2
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: H05B 41/2828 using control circuits for the switching elements H05B41/2827 takes precedence
• CPC Class Codes: H05B 41/2851 for protecting the circuit against abnormal operating conditions
• CPC Class Codes: H05B 41/2981 for protecting the circuit against abnormal operating conditions
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

A ballast controller integrated circuit which executes a specific set of instructions via an integrated state diagram architecture to control a fluorescent lamp or high intensity discharge lamp and protect the ballast. The state diagram architecture controls powering up and down of the IC and the half-bridge circuit driven by the IC, preheating and striking of the lamp, running of the lamp, sensing for numerous possible fault conditions, and recovering from these fault conditions based on the normal maintenance of a lamp, while requiring fewer internal and external components than previous electronic ballasts.

Claims

1. A ballast control IC comprising an oscillator circuit, a preheat circuit and a start-up circuit, the oscillator circuit including only one comparator such that a smaller layout space is required and the overall size of the IC is reduced.

2. The ballast control IC as recited in claim 1, wherein the preheat circuit generates a preheat frequency, and wherein the preheat frequency is programmed using an external pre-heat resistor in parallel with a timing resistor, the preheat resistor being gradually disconnected as the ballast control IC enters a run mode following the pre-heat frequency.

3. The ballast control IC as recited in claim 2, wherein the preheat circuit generates a preheat voltage ramp to determine the preheat period, and the preheat voltage ramp is also used as an ignition ramp.

4. The ballast control IC of claim 2, wherein the preheat circuit does not include a comparator.

5. The ballast control IC according to claim 1, wherein the oscillator circuitry further comprises a capacitor coupled to the one comparator and operable to be charged and discharged to influence operation of the one comparator.

6. The ballast control IC according to claim 5, further comprising a threshold voltage applied to the one comparator being selectively varied in dependence upon the charging or discharging of the capacitor.

7. The ballast control IC according to claim 6, further comprising a switch for selectively varying the threshold voltage, the switch being coupled to the comparator whereby the switch changes state when a comparator output changes state.

8. A ballast control IC with a preheat function, comprising:

a switch coupled to a current source and operable to gradually change state to gradually change an external resistance based on a voltage derived from the current source;

a circuit for charging and discharging an external capacitor and coupled to the external resistance, whereby the gradually changing resistance gradually modifies a charging/discharging frequency of the circuit; and

a switching control coupled to the circuit and operable to provide a switching signal at the gradually modified frequency to provide a preheat function.

9. The ballast control IC according to claim 8, further comprising an external capacitor coupled to the current source to provide a gradually changing voltage applied to the switch.

10. A method for providing an oscillating signal in a ballast control IC, comprising:

charging and discharging a capacitor between given voltage levels;

comparing the voltage level of the capacitor with a first threshold and providing a first signal when the voltage level of the capacitor crosses the first threshold;

comparing the voltage level of the capacitor with a second threshold and providing a second signal when the voltage level of the capacitor crosses the second threshold; and

switching between the first and second threshold when the first or second signal is provided.

11. A method for providing a preheat function in a ballast control IC, comprising:

applying a current source to an energy source element to provide a gradually changing parameter dependent on the element;

gradually switching a resistance between a first and second value based on the gradually changing parameter;

applying the gradually changing resistance to an oscillator circuit, where the gradually changing resistance influences a frequency of the oscillator circuit such that the frequency gradually changes; and

applying the gradually changing frequency to a switching circuit to obtain a preheat function.