A driving circuit for causing a light emitting element to emit light in response to a driving signal is provided. The driving circuit comprising a first current supply circuit that starts to supply a driving current to the light emitting element in response to the driving signal, a second current su
A driving circuit for causing a light emitting element to emit light in response to a driving signal is provided. The driving circuit comprising a first current supply circuit that starts to supply a driving current to the light emitting element in response to the driving signal, a second current supply circuit that starts to supply a supplementary current to the light emitting element in response to the driving signal. The second current supply circuit stops to supply the supplementary current upon detecting that a voltage applied to the light emitting element has reached a threshold voltage.
대표청구항▼
1. A driving circuit for causing a light emitting element to emit light in response to a driving signal, the driving circuit comprising: a first current supply circuit that starts to supply a first current for driving the light emitting element to the light emitting element in response to the drivin
1. A driving circuit for causing a light emitting element to emit light in response to a driving signal, the driving circuit comprising: a first current supply circuit that starts to supply a first current for driving the light emitting element to the light emitting element in response to the driving signal; anda second current supply circuit that starts to supply a second current to the light emitting element in response to the driving signal, the second current increasing a current supplied to the light emitting element, the second current supply circuit comprising a MOS transistor having a source connected to the light emitting element,wherein the second current supply circuit stops supplying the second current in response to the MOS transistor being OFF,wherein the first current supply circuit continues to supply the first current to the light emitting element after the second current supply circuit stops supplying the second current,wherein the source of the MOS transistor is connected to the light emitting element without another transistor intervening therebetween,wherein a constant voltage is applied to a drain of the MOS transistor,wherein the second current supply circuit further comprises a diode fixing a potential of a gate of the MOS transistor in response to the driving signal, andwherein the second current supply circuit stops supplying the second current as the MOS transistor stops operating as a source follower when a voltage applied to the light emitting element reaches a threshold voltage. 2. The driving circuit according to claim 1, wherein the threshold voltage is not greater than a light emission voltage of the light emitting element. 3. The driving circuit according to claim 1, wherein: the first current supply circuit comprises a current mirror circuit that supplies to the light emitting element, as the first current, a current that depends on a current supplied from a constant current source; andthe current mirror circuit takes on an operative state in response to the driving signal. 4. The driving circuit according to claim 3, wherein the current mirror circuit comprises a first MOS transistor and a second MOS transistor, wherein a first main electrode of the first MOS transistor and a first main electrode of the second MOS transistor are connected to a constant voltage source,wherein a second main electrode of the first MOS transistor is connected to the constant current source, andwherein a second main electrode of the second MOS transistor is connected to the light emitting element. 5. The driving circuit according to claim 1, further comprising: a third current supply circuit that supplies a third current to the light emitting element prior to starting supply of the first current. 6. The driving circuit according to claim 1, wherein the first current supply circuit comprises a first MOS transistor connected to the light emitting element, andwherein the first current is supplied to the light emitting element from the first MOS transistor. 7. The driving circuit according to claim 6, wherein the first MOS transistor is connected to the light emitting element without another transistor intervening therebetween. 8. The driving circuit according to claim 1, wherein a signal based on the driving signal is supplied to each of the first current supply circuit and the second current supply circuit through their respective signal paths. 9. The driving circuit according to claim 1, wherein a signal based on the driving signal and supplied to the first current supply circuit and a signal based on the driving signal and supplied to the second current supply circuit are complementary to each other. 10. A driving circuit for causing a light emitting element to emit light in response to a driving signal, the driving circuit comprising: a first current supply circuit that starts to supply a first current for driving the light emitting element to the light emitting element in response to the driving signal; anda second current supply circuit that starts to supply a second current to the light emitting element in response to the driving signal, the second current increasing a current to be supplied to the light emitting element, the second current supply circuit comprising a MOS transistor having a source connected to the light emitting element,wherein the second current supply circuit stops supplying the second current in response to the MOS transistor being OFF,wherein the first current supply circuit continues to supply the first current to the light emitting element after the second current supply circuit stops supplying the second current,wherein a constant voltage is applied to the drain of the MOS transistor,wherein the second current supply circuit further comprises an inverter whose input terminal is connected to the light emitting element,wherein the inverter changes the level of a signal output therefrom when a voltage applied to the light emitting element has reached a threshold voltage, andwherein the second current supply circuit stops supplying the second current as a potential of a gate of the MOS transistor changes in accordance with the output of the inverter. 11. The driving circuit according to claim 10, wherein the second current supply circuit stops supplying the second current in response to the voltage applied to the light emitting element reaching a voltage that is not greater than a light emission voltage of the light emitting element. 12. The driving circuit according to claim 10, wherein the first current supply circuit comprises a current mirror circuit that supplies to the light emitting element, as the first current, a current that depends on a current supplied from a constant current source, andwherein the current mirror circuit takes on an operative state in response to the driving signal. 13. The driving circuit according to claim 10, further comprising: a third current supply circuit that supplies a third current to the light emitting element prior to starting supply of the first current. 14. The driving circuit according to claim 10, wherein a signal based on the driving signal is supplied to each of the first current supply circuit and the second current supply circuit through their respective signal paths. 15. The driving circuit according to claim 10, wherein a signal based on the driving signal and supplied to the first current supply circuit and a signal based on the driving signal and supplied to the second current supply circuit are complementary to each other. 16. A driving circuit for causing a light emitting element to emit light in response to a driving signal, the driving circuit comprising: a first current supply circuit that starts to supply a first current for driving the light emitting element to the light emitting element in response to the driving signal; anda second current supply circuit that starts to supply a second current to the light emitting element in response to the driving signal, the second current increasing a current supplied to the light emitting element, the second current supply circuit comprising a MOS transistor having a source connected to the light emitting element,wherein the second current supply circuit stops supplying the second current in response to the MOS transistor being OFF,wherein the first current supply circuit continues to supply the first current to the light emitting element after the second current supply circuit stops supplying the second current,wherein a constant voltage is applied to the drain of the MOS transistor,wherein the second current supply circuit further comprises a comparator whose first input terminal is connected to the light emitting element, and a reference voltage is applied to a second input terminal of the comparator,wherein the comparator changes the level of a signal output therefrom when a voltage applied to the light emitting element has reached a threshold voltage, andwherein the second current supply circuit stops supplying the second current as the potential of a gate of the MOS transistor changes in accordance with the output of the comparator. 17. The driving circuit according to claim 16, wherein the second current supply circuit stops supplying the second current in response to the voltage applied to the light emitting element reaching a voltage that is not greater than a light emission voltage of the light emitting element. 18. The driving circuit according to claim 16, wherein the first current supply circuit comprises a current mirror circuit that supplies to the light emitting element, as the first current, a current that depends on a current supplied from a constant current source, andwherein the current mirror circuit takes on an operative state in response to the driving signal. 19. The driving circuit according to claim 16, further comprising: a third current supply circuit that supplies a third current to the light emitting element prior to starting supply of the first current. 20. The driving circuit according to claim 16, wherein a signal based on the driving signal is supplied to each of the first current supply circuit and the second current supply circuit through their respective signal paths.
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이 특허에 인용된 특허 (10)
Nakamura, Hiroyuki, Differential signal comparator.
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