# Patent

## Title
Electric lighting driver circuit

## Abstract

An electric lighting driver circuit for driving an illuminating unit to emit light includes a flyback converting unit for converting a DC input voltage to a low ripple DC voltage, and a half-bridge converting unit electrically connected to the flyback converting unit, for converting the low ripple DC voltage to a low frequency, rectangular wave output voltage to drive the illuminating unit to emit light. The flyback converting unit includes a dual-output winding transformer connected to the half-bridge converting unit. The dual-output winding transformer includes a first winding at a primary side of the dual-output winding transformer and a second winding and a third winding at a secondary side of the dual-output winding transformer. The third winding converts leakage inductance attributed to the first winding and the second winding to electrical energy that is provided to the half-bridge converting unit.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a driver circuit, more particularly to an electric lighting driver circuit.
2. Description of the Related Art
As shown in FIG. 1, a conventional in-vehicle electric lighting driver circuit 1 is electrically connected to an in-vehicle power source V1 and a high intensity discharge (HID) lamp, and is for converting a direct current (DC) input voltage from the in-vehicle power source V1 to an alternating current (AC) low frequency, rectangular wave voltage to drive the HID lamp. The in-vehicle electric lighting driver circuit 1 includes a flyback DC-to-DC converter 11 and a full-bridge DC-to-AC converter 12. The flyback DC-to-DC converter 11 is configured to boost the DC input voltage so as to provide a high DC voltage that is stable and that has relatively small ripples, and includes a power switch S, a single-output winding transformer 111 and an output diode D. The power switch S is operated at a high frequency to boost the DC input voltage to the high DC voltage.
The full-bridge DC-to-AC converter 12 is electrically connected to the flyback DC-to-DC converter 11 and the HID lamp, and includes an output capacitor C1 and four power switches, namely S1, S2, S3 and S4. The power switches S1, S2, S3 and S4 are operated at a low frequency, in order to convert the high DC voltage to a low frequency, rectangular wave voltage that is necessary for the HID lamp to operate in a steady state.
Nonetheless, the full-bridge DC-to-AC converter 12 requires four power switches, raising the manufacturing costs of the electric lighting driver circuit 1. Moreover, FIG. 2 illustrates an extended structure of the conventional electric lighting driver circuit 1 depicted in FIG. 1, which is adapted to drive two HID lamps. Compared to the original structure, the extended structure employs an additional output capacitor C2 and four additional power switches S5, S6, S7 and S8, bringing the manufacturing costs even higher.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention is to provide an electric lighting driver circuit that is less expensive to produce.
Accordingly, an electric lighting driver circuit of the present invention is for electrically connecting to a direct current (DC) power source and for driving an illuminating unit to emit light. The electric lighting driver circuit comprises a flyback converting unit for converting a DC input voltage from the DC power source to a low ripple DC voltage, and a first half-bridge converting unit electrically connected to the flyback converting unit, for converting the low ripple DC voltage to a low frequency, rectangular wave output voltage to drive the illuminating unit to emit light.
The flyback converting unit includes a dual-output winding transformer electrically connected to the first half-bridge converting unit. The dual-output winding transformer includes a first winding at a primary side of the dual-output winding transformer and a second winding and a third winding at a secondary side of the dual-output winding transformer. The third winding converts leakage inductance attributed to the first winding and the second winding to electrical energy that is provided to the first half-bridge converting unit.



BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which:
FIG. 1 is a circuit diagram of a conventional electric lighting driver circuit;
FIG. 2 is a circuit diagram of an extended structure of the conventional electric lighting driver circuit;
FIG. 3 is a circuit diagram of a first preferred embodiment of an electric lighting driver circuit according to the invention;
FIG. 4 is a circuit diagram of a second preferred embodiment of this invention;
FIG. 5 is a circuit diagram of a third preferred embodiment of this invention;
FIG. 6 is a circuit diagram of a fourth preferred embodiment of this invention;
FIG. 7 is a circuit diagram of a fifth preferred embodiment of this invention;
FIG. 8 is a circuit diagram of a sixth preferred embodiment of this invention;
FIG. 9 is a circuit diagram of a seventh preferred embodiment of this invention; and
FIG. 10 is a circuit diagram of an eighth preferred embodiment of this invention.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before the present invention is described in greater detail, it should be noted that like elements are denoted by the same reference numerals throughout the disclosure.
As shown in FIG. 3, the first preferred embodiment of an electric lighting driver circuit according to the present invention comprises a flyback converting unit 3, a first half-bridge converting unit 4 electrically connected to the flyback converting unit 3, and an illuminating unit 5 electrically connected to the flyback converting unit 3 and the first half-bridge converting unit 4. The flyback converting unit 3 is electrically connected to a direct current (DC) power source Vin, and cooperates with the first half-bridge converting unit 4 for driving the illuminating unit 5 to emit light.
The flyback converting unit 3 includes a dual-output winding transformer 31, a first power switch S1, a voltage multiplier module 32, and a first diode D3 and a second diode D4 that electrically interconnect the voltage multiplier module 32 and the first half-bridge converting unit 4. The dual-output winding transformer 31 is configured to boost a DC input voltage from the DC power source Vin, and converts leakage inductance to electrical energy that is provided at an output node of the dual-output winding transformer 31. The first power switch S1 is electrically connected to the dual-output winding transformer 31 and controls supply of the DC input voltage to the dual-output winding transformer 31. The voltage multiplier module 32 electrically interconnects the dual-output winding transformer 31 and the first half-bridge converting unit 4. The first power switch S1 is operated at a high frequency to boost the DC input voltage to a high DC voltage.
The dual-output winding transformer 31 includes a first winding NP at a primary side of the dual-output winding transformer 31 and a second winding NS1 and a third winding NS2 at a secondary side of the dual-output winding transformer 31. Each of the first winding NP, the second winding NS1 and the third winding NS2 has a first end and a second end. The first end and the second end of the first winding Np are electrically connected to the DC power source Vin and the first power switch S1, respectively. Specifically, the third winding NS2 converts leakage inductance attributed to the first winding NP and the second winding NS1 to electrical energy that is provided to the first half-bridge converting unit 4.
The voltage multiplier module 32 includes a first step-up capacitor CS1, a second step-up capacitor CS2, a first step-up diode D1 and a second step-up diode D2. The first step-up capacitor CS1 electrically interconnects an anode of the first diode D3 and the first end of the second winding NS1. The second step-up capacitor CS2 electrically interconnects an anode of the second diode D4 and the first end of the third winding NS2. The first step-up diode D1 has a cathode electrically connected to the anode of the first diode D3, and an anode electrically connected to the second end of the second winding NS1. The second step-up diode D2 has a cathode electrically connected to the anode of the second diode D4, and an anode electrically connected to a second end of the third winding NS2.
The first half-bridge converting unit 4 includes a first output capacitor CO1, a second output capacitor CO2, a second power switch S2, a third power switch S3, a first buck inductor Lbuck1 and a first capacitor Cbuck1. The first output capacitor CO1 electrically interconnects a cathode of the first diode D3 and the second end of the second winding N31. The second output capacitor CO2 electrically interconnects a cathode of the second diode D4 and the second end of the third winding NS2. The second power switch S2 has a first switch terminal electrically connected to the cathode of the first diode D3, and a second switch terminal. The third power switch S3 interconnects the second switch terminal of the second power switch S2 and the second end of the third winding NS2. The third power switch S3 has a first switch terminal electrically connected to the second switch terminal of the second power switch S2. The second power switch S2 and the third power switch S3 are adapted to operate at both high frequency rectangular wave and low frequency rectangular wave. In this configuration, the half-bridge converting unit 4 is capable of converting the high DC voltage generated by the flyback converting unit 3 to a low-frequency AC rectangular voltage, which is subsequently fed to the illuminating unit 5.
The first buck inductor Lbuck1 connects electrically the first switch terminal of the third power switch S3 to the illuminating unit 5. The first capacitor Cbuck1 has an end electrically connected to the illuminating unit 5 and the first buck inductor Lbuck1, and another end electrically connected to the first output capacitor CO1 and the second output capacitor CO2.
The illuminating unit 5 includes a first lamp 51. In this embodiment, the first lamp 51 is configured as a high intensity discharge (HID) lamp, but may be configured as other illuminating components in other embodiments of the invention.
The electric lighting driver circuit further comprises a first lighting unit 6 that electrically connects the first half-bridge converting unit 4 to the first lamp 51 and that is for increasing the probability to light the first lamp 51.
The first capacitor Cbuck1 is disposed in parallel with the first lamp 51 and the first lighting unit 6 so as to buck the DC output voltage to a steady-state voltage, and to cooperate with the first capacitor Cbuck1 to filter out high frequency ripples attributed to the second power switch S2 and the third power switch S3. This configuration is to avoid acoustic resonance that usually occurs when the electric lighting driver circuit is operated in a high frequency, and may cause instability (i.e., flashing) to the light emitted by the HID lamp, and even lamp malfunction.
In use, the DC input voltage from the DC power source Vin is fed into the flyback converting unit 3 of the electric lighting driver circuit, converted to the low ripple DC voltage by the dual-output winding transformer 31, and boosted by the voltage multiplier module 32. The first half-bridge converting unit 4 subsequently converts the boosted low ripple DC voltage to a rectangular wave output voltage that has both high-frequency and low-frequency components, which is for driving the second power switch S2 and the third power switch S3 to supply an output voltage to the first lamp 51 of the illuminating unit 5. The first lamp 51 consequently emits light.
As shown in FIG. 4, the second preferred embodiment of the electric lighting driver circuit according to the present invention has a structure similar to that of the first preferred embodiment. The main difference between this embodiment and the previous embodiment resides in the configuration of a second half-bridge converting unit 7 and a second lighting unit 8. Moreover, the illuminating unit 5 further includes a second lamp 52 which, like the first lamp 51, is configured as but not limited to a HID lamp in this embodiment.
The second half-bridge converting unit 7 includes a third output capacitor CO3, a fourth output capacitor CO4, a fourth power switch S4, a fifth power switch S5, a second buck inductor Lbuck2 and a second capacitor Cbuck2. Each of the fourth power switch S4 and the fifth power switch S5 has a first switch terminal and a second switch terminal. The first switch terminal of the fifth power switch S5 is electrically connected to the second switch terminal of the fourth power switch S4. The third output capacitor CO3 electrically connects a cathode of the first diode D3 to an end of the fourth output capacitor CO4. Another end of the fourth output capacitor CO4 is electrically connected to the second switch terminal of the fifth power switch S5.
The first switch terminal of the fourth power switch S4 is also electrically connected to the cathode of the first diode D3. The second buck inductor Lbuck2 connects electrically the first switch terminal of the fifth power switch S5 to the second lamp 52 of the illuminating unit 5. The second capacitor Cbuck2 has an end electrically connected to the second lamp 52 and the second buck inductor Lbuck2, and another end electrically connected to the third output capacitor CO3 and the fourth output capacitor CO4. The second capacitor Cbuck2 is also disposed in parallel with the second lamp 52 and the second lighting unit 8.
The second preferred embodiment enables the first half-bridge converting unit 4 and the second half-bridge converting unit 7 to respectively supply the output voltage to the first lamp 51 and the second lamp 52 for emitting light, and has the same advantages as those of the first preferred embodiment.
As shown in FIG. 5, the third preferred embodiment of the electric lighting driver circuit according to the present invention has a structure similar to that of the second preferred embodiment. The main difference between this embodiment and the second preferred embodiment resides in the following. The third output capacitor CO3 and the fourth output capacitor CO4 of the second half-bridge converting unit 7 are omitted. Alternatively, the first switch terminal and the second switch terminal of the fourth power switch S4 are electrically connected to the cathode of the first diode D3 and the first switch terminal of the fifth power switch S5, respectively. The second switch terminal of the fifth power switch S5 is electrically connected to the second end of the third winding NS2. The third preferred embodiment provides a relatively simpler structure, enables the second half-bridge converting unit 7 to supply the output voltage to the second lamp 52 for emitting light, and has the same advantages as those of the second preferred embodiment.
As shown in FIG. 6, the fourth preferred embodiment of the electric lighting driver circuit according to the present invention has a structure similar to that of the first preferred embodiment. The main difference between this embodiment and the first preferred embodiment resides in the following. The voltage multiplier module 32 of the flyback converter 3 is omitted (see FIG. 3), thereby providing a further simplified structure but at the expense of a weaker lighting effect. The fourth preferred embodiment has the same advantages as those of the first preferred embodiment.
As shown in FIG. 7, the fifth preferred embodiment of the electric lighting driver circuit according to the present invention has a structure similar to that of the first preferred embodiment. The main difference between this embodiment and the first preferred embodiment resides in the following. The flyback converting unit 31 further includes a voltage booster 33 that is configured to boost the DC input voltage, and a first boosting diode Da1. The voltage booster 33 includes a boosting inductor Lb, a second boosting diode Da2, and a boosting capacitor Cdc. The boosting inductor Lb connects electrically the DC power source Vin to an anode of the second boosting diode Da2. A cathode of the second boosting diode Da2 is electrically connected to the first end of the first winding Np of the dual-output winding transformer 31. The boosting capacitor Cdc has an end electrically connected to the cathode of the second boosting diode Da2 and the first end of the first winding Np of the dual-output winding transformer 31, and another end grounded.
The fifth preferred embodiment has the same advantages as those of the first preferred embodiment, and further employs the voltage booster 33 to boost the DC input voltage before feeding into the dual-output winding transformer 31, thereby enhancing the lighting effect.
As shown in FIG. 8, the sixth preferred embodiment of the electric lighting driver circuit according to the present invention has a structure similar to that of the fifth preferred embodiment. The main difference between this embodiment and the fifth preferred embodiment resides in the configuration of a second half-bridge converting unit 7 and a second lighting unit 8. The illuminating unit 5 also includes a second lamp (similar to the second preferred embodiment, see FIG. 4). The sixth preferred embodiment enables the first half-bridge converting unit 4 and the second half-bridge converting unit 7 to respectively supply the output voltage to the first lamp 51 and the second lamp 52 for emitting light, and has the same advantages as those of the fifth preferred embodiment.
As shown in FIG. 9, the seventh preferred embodiment of the electric lighting driver circuit according to the present invention has a structure similar to that of the sixth preferred embodiment. The main difference between this embodiment and the sixth preferred embodiment resides in the following. The third output capacitor CO3 and the fourth output capacitor CO4 of the second half-bridge converting unit 7 are omitted. Alternatively, the first switch terminal and the second switch terminal of the fourth power switch S4 are electrically connected to the cathode of the first diode D3 and the first switch terminal of the fifth power switch S5, respectively. The second switch terminal of the fifth power switch S5 is electrically connected to the second end of the third winding NS2. The seventh preferred embodiment provides a relatively simpler structure, enables the second half-bridge converting unit 7 to supply the output voltage to the second lamp 52 for emitting light, and has the same advantages as those of the sixth preferred embodiment.
As shown in FIG. 10, the eighth preferred embodiment of the electric lighting driver circuit according to the present invention has a structure similar to that of the fifth preferred embodiment. The main difference between this embodiment and the fifth preferred embodiment resides in the following. The voltage multiplier module 32 of the flyback converter 3 is omitted (see FIG. 3), thereby providing a further simplified structure but at the expense of a weaker lighting effect. The eighth preferred embodiment has the same advantages as those of the fifth preferred embodiment.
To sum up, the effect of this invention is that by having the third winding NS2 convert leakage inductance attributed to the first winding Np and the second winding NS1 to electrical energy that is provided to the first half-bridge converting unit 4, by having the first half-bridge converting unit 4 include two power switches S1 and S2 instead of four as disclosed in the conventional configuration (see FIG. 1), and by having the first buck inductor Lbuck1 and the first capacitor Cbuck1 cooperate to filter out high frequency ripples attributed to the second power switch S2 and the third power switch S3, this invention achieves higher efficiency and lower manufacturing costs, and avoids undesired audio frequency resonance in practical use.
While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.

## Claims

1. An electric lighting driver circuit for electrically connecting to a direct current (DC) power source and for driving an illuminating unit to emit light, said electric lighting driver circuit comprising:
a flyback converting unit for converting a DC input voltage from the DC power source to a low ripple DC voltage; and
a first half-bridge converting unit electrically connected to said flyback converting unit, for converting the low ripple DC voltage to a low frequency, rectangular wave output voltage to drive the illuminating unit to emit light;
said flyback converting unit including a dual-output winding transformer electrically connected to said first half-bridge converting unit, said dual-output winding transformer including a first winding at a primary side of said dual-output winding transformer and a second winding and a third winding at a secondary side of said dual-output winding transformer, said third winding converting leakage inductance attributed to said first winding and said second winding to electrical energy that is provided to said first half-bridge converting unit;
wherein said flyback converting unit further includes a first power switch that is electrical) connected to said dual-output winding transformer and that controls supply of the DC input voltage to said dual-output winding transformer;
wherein said flyback converting unit further includes a voltage multiplier module electrically interconnecting said dual-output winding transformer and said first half-bridge converting unit;
wherein said flyback converting unit further includes a first diode and a second diode that electrically interconnect said voltage multiplier module and said first half-bridge converting unit;
wherein said voltage multiplier module includes:
a first step-up capacitor electrically interconnecting an anode of said first diode and a first end of said second winding;
a second step-up capacitor electrically interconnecting an anode of said second diode and a first end of said third winding;
a first step-up diode having a cathode electrically connected to said anode of said first diode, and an anode electrically connected to a second end of said second winding; and
a second step-up diode having a cathode electrically connected to said anode of said second diode and an anode electrically connected to a second end of said third winding;

wherein said first half-bridge converting unit includes:
a first output capacitor electrically interconnecting a cathode of said first diode and said second end of said second winding;
a second output capacitor electrically interconnecting a cathode of said second diode and said second end of said third winding;
a second power switch having a first switch terminal electrically connected to said cathode of said first diode, and a second switch terminal; and
a third power switch that interconnects said second switch terminal of said second power switch and said second end of said third winding;

wherein said third power switch has a first switch terminal electrically connected to said second end of said second power switch, and said first half-bridge converting unit further includes:
a first buck inductor to connect electrically said first switch terminal of said third power switch to the illuminating unit; and
a first capacitor having an end electrically connected to the illuminating unit and said first buck inductor and another end electrically connected to said first output capacitor and said second output capacitor;

said first buck inductor being configured to buck the DC output voltage to a steady-state voltage, and cooperating with said first capacitor to filter out high frequency ripples attributed to said second power switch and said third power switch.

2. The electric lighting driver circuit as claimed in claim 1, wherein said flyback converting unit further includes a voltage booster that is configured to boost the DC input voltage.

3. The electric lighting driver circuit as claimed in claim 1, the illuminating unit including a first lamp, said electric lighting driver circuit further comprising a first lighting unit for electrically connecting said first half-bridge converting unit to the first lamp.

4. An electric lighting driver circuit for electrically connecting to a direct current (DC) power source and for driving an illuminating unit to emit light, the illuminations unit including a first lamp and a second lamp, said electric lighting driver circuit comprising:
a flyback converting unit for converting a DC input voltage from the DC power source to a low ripple DC voltage; and
a first half-bridge converting unit electrically connected to said flyback converting unit, for converting the low ripple DC voltage to a low frequency, rectangular wave output voltage to drive the illuminating unit to emit light;
said flyback converting unit including a dual-output winding transformer electrically connected to said first half-bridge converting unit, said dual-output winding transformer including a first winding at a primary side of said dual-output winding transformer and a second winding and a third winding at a secondary side of said dual-output winding transformer, said third winding converting leakage inductance attributed to said first winding and said second winding to electrical energy that is provided to said first half-bridge converting unit; and
said electric lighting driver circuit further comprising a first lighting unit for electrically connecting said first half-bridge converting unit to the first lamp; and a second half-bridge converting unit electrically connected to said first half-bridge converting unit, and a second lighting unit for electrically connecting said second half-bridge converting unit to the second lamp.