Patent Application
20170311401
The invention relates to a light emitting device, and more particularly to a light emitting device that may have a high power factor and a constant voltage/current feedback control mechanism.
Conventional light emitting devices may include a light emitting unit and a control circuit for driving the light emitting unit. The control circuit has a power factor that is closely associated with efficiency of a power supply system. A conventional control circuit usually has a power factor correction circuit for promoting the power factor. However, since the conventional control circuits that are capable of correcting the power factor are usually highly complicated, high costs in research and production are usually incurred.
Therefore, an object of the present invention is to provide a light emitting device that may have a high power factor and a constant voltage/current feedback control mechanism, and that may have a relatively simple circuit structure, to thereby reduce costs.
According to an aspect of the present invention, a light emitting device is adapted to receive an alternating-current (AC) voltage signal generated by an AC signal source, and comprises:
According to another aspect of the present invention, a light emitting device is adapted to receive an alternating-current (AC) voltage signal generated by an AC signal source, and comprises:
According to yet another aspect of the present invention, a light emitting device is adapted to receive an alternating-current (AC) voltage signal generated by an AC signal source, and comprises:
Other features and advantages of the present invention will become apparent in the following detailed description of embodiments with reference to the accompanying drawings, of which:
Referring to
The AC signal source VAC has a first terminal and a second terminal. The filter circuit 6 is electrically coupled between the rectifier circuit 1 and the AC signal source VAC. The filter circuit 6 receives and filters the AC voltage signal, and provides the filtered AC voltage signal to the rectifier circuit 1. The filter circuit 6 has a first terminal electrically coupled to the first terminal of the AC signal source VAC, a second terminal, and a third terminal electrically coupled to the second terminal of the AC signal source VAC. In this embodiment, the filter circuit 6 includes a filtering inductor LF and a filtering capacitor CF. The filtering inductor LF has a first terminal electrically coupled to the first terminal of the filter circuit 6, and a second terminal electrically coupled to the second terminal of the filter circuit 6. The filtering capacitor CF has a first terminal electrically coupled to the second terminal of the filter circuit 6, and a second terminal electrically coupled to the third terminal of the filter circuit 6.
The rectifier circuit 1 is electrically coupled to the filter circuit 6 for receiving and rectifying the filtered AC voltage signal, and generates a rectified signal. The rectifier circuit 1 has a first terminal electrically coupled to the second terminal of the filter circuit 6, a second terminal electrically coupled to the second terminal of the AC signal source VAC, a third terminal electrically coupled to the mutual inductance device 2 and the light emitting unit 3 for providing the rectified signal thereto, and a grounded fourth terminal. In this embodiment, the rectifier 1 includes a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4. The first diode D1 has an anode and a cathode respectively and electrically coupled to the first terminal and the third terminal of the rectifier circuit 1. The second diode D2 has an anode and a cathode respectively and electrically coupled to the fourth terminal and the second terminal of the rectifier circuit 1. The third diode D3 has an anode and a cathode respectively and electrically coupled to the second terminal and the third terminal of the rectifier circuit 1. The fourth diode D4 has an anode and a cathode respectively and electrically coupled to the fourth terminal and the first terminal of the rectifier circuit 1.
The mutual inductance device 2 includes a primary winding N1 and a secondary winding N2. The primary winding N1 has a first terminal electrically coupled to the third terminal of the rectifier circuit 1, and a second terminal. The secondary winding N2 has a first terminal electrically coupled to the second terminal of the primary winding and a second terminal. The energy-storing capacitor CS has a first terminal electrically coupled to the second terminal of the primary winding N1, and a grounded second terminal.
The light emitting unit 3 includes a first terminal electrically coupled to the first terminal of the primary winding N1, a second terminal, a third terminal and a fourth terminal. In this embodiment, the light emitting unit 3 is driven by a high-frequency AC signal, and may be an AC-type fluorescent lamp (e.g., a fluorescent tube), or a combination of an AC-type gas-discharge lamp (e.g., a high-intensity discharge (HID) lamp) and a high-voltage driving circuit thereof. The resonant capacitor CR has a first terminal electrically coupled to the third terminal of the light emitting unit 3, and a second terminal electrically coupled to the fourth terminal of the light emitting unit 3. In other words, the resonant capacitor CR is electrically coupled across the light emitting unit 3 at the third and fourth terminals of the latter. The resonant inductor LR has a first terminal electrically coupled to the second terminal of the light emitting unit 3, and a second terminal electrically coupled to the second terminal of the secondary winding N2. Accordingly, a series connection of the resonant inductor LR and the light emitting module is electrically coupled between the first terminal of the primary winding N1 and the second terminal of the secondary winding N2.
The switch unit 4 has a first terminal electrically coupled to the second terminal of the secondary winding N2, a second terminal, and a control terminal receiving a pulse width modulation (PWM) signal, and is configured to make or break electrical connection between the first and second terminals thereof in response to the PWM signal. In this embodiment, the switch unit 4 includes a transistor M that has a drain terminal, a source terminal and a gate terminal respectively and electrically coupled to the first terminal, the second terminal and the control terminal of the switch unit 4.
The feedback unit 7 has a first terminal electrically coupled to the second terminal of the switch unit 4, a second terminal and a grounded third terminal. The feedback unit 7 is configured to sense a voltage or a current at the second terminal of the switch unit 4, and provides a sensed result at the second terminal thereof. In this embodiment, the feedback unit 7 includes a sensing resistor RS that has a first terminal electrically coupled to the first and second terminals of the feedback unit 7, and a second terminal electrically coupled to the third terminal of the feedback unit 7.
The control circuit 5 has a power supply terminal electrically coupled to the energy-storing capacitor CS, a reference terminal to receive a reference voltage, a driving terminal electrically coupled to the control terminal of the switch unit 4, and a sensing terminal electrically coupled to the second terminal of the feedback unit 7 for receiving the sensed result therefrom. In this embodiment, the reference terminal is electrically coupled to the third terminal of the feedback unit 7 (i.e., grounded). The control circuit 5 generates and provides the PWM signal to the control terminal of the switch unit 4 via the driving terminal thereof, to thereby control the switch unit 4 to make or break electrical connection between the first and second terminals thereof, i.e., the control circuit 5 controls the switch unit 4 to conduct or non-conduct.
When the control circuit 5 controls the switch unit 4 to make electrical connection, the secondary winding N2 generates a voltage VN2, and the primary winding N1 generates a voltage VN1 by induction. A resulting voltage VN1+VN2 forms a resonant voltage that drives emission of the light emitting unit 3. Since the resonant voltage VN1+VN2 is higher than the AC voltage signal of the AC signal source VAC, the mutual inductance device 2 may not receive the AC voltage signal of the AC signal source VAC.
In addition, since the resonant voltage VN1+VN2 may be higher than a voltage conventionally used for driving the light emitting unit 3, a time required to start light emission of the light emitting unit 3 may be effectively reduced.
When the control circuit 5 then controls the switch unit 4 to break electrical connection, the light emitting unit 3 is driven by a reversed voltage VN1+VN2, and energy stored by the primary winding N1 is released to the energy-storing capacitor CS while the energy-storing capacitor CS is charged by the AC signal source VAC at the same time. That is, the energy-storing capacitor CS is charged with a voltage of VAC+VN1. In such a manner, even when the AC voltage signal is lower than a voltage across the energy-storing capacitor CS, charging of the energy-storing capacitor CS may still proceed, so as to synchronize the AC voltage signal with a current that charges the energy-storing capacitor CS, resulting in a high power factor of the light emitting device 100. Moreover, a frequency of a current flowing from the primary winding N1 to the filter circuit 6 may be lowered to a frequency of the AC signal source VAC and synchronized with the AC voltage signal, which may also lead to a high power factor of the light emitting device 100.
It should be noted that the control circuit 5 may sense the voltage at the second terminal of the switch unit 4 via the second terminal of the feedback unit 7. When the voltage at the second terminal of the switch unit 4 is higher than a pre-designed threshold value, the control circuit 5 controls the switch unit 4 to break electrical connection between the first and second terminals thereof until beginning of the next cycle of the PWM signal. By virtue of cooperation of the control circuit 5 and the sensing resistor RS of the feedback unit 7, a current flowing through the switch unit 4 may thus be controlled, to thereby stabilize the current.
Furthermore, the control circuit 5 may adjust a duty cycle of the PWM signal according to a voltage at the power supply terminal thereof, to thereby stabilize the voltage at the power supply terminal via the voltage feedback mechanism.
Referring to
In this embodiment, the resonant capacitor CR and the resonant inductor LR of the first embodiment are omitted. The light emitting unit 3 may have a first terminal electrically coupled to the second terminal of the secondary winding N2, and a second terminal electrically coupled to the first terminal of the switch unit 4. The light emitting unit 3 may be driven using a direct-current (DC) voltage, and may be a light emitting diode (LED) unit. The light emitting unit 3 may include a plurality of LED strings 31 that are electrically coupled in parallel between the first and second terminals of the light emitting unit 3. Each of the LED strings 31 includes a plurality of LEDs electrically coupled in series. The light emitting device 100 may further include a rectifying diode DR that has an anode electrically coupled to the second terminal of the light emitting unit 3, and a cathode electrically coupled to the first terminal of the secondary winding N2.
Referring to
In this embodiment, the rectifying diode DR of the second embodiment is omitted. The light emitting device 100 may further include an energy-storing inductor LS that cooperates with the light emitting unit 3 to form a light emitting module, and a freewheeling diode DF. The energy-storing inductor LS has a first terminal electrically coupled to the second terminal of the secondary winding N2, and a second terminal. The first terminal of the light emitting unit 3 is electrically coupled to the second terminal of the energy-storing inductor LS, and the second terminal of the light emitting unit 3 is electrically coupled to the first terminal of the switch unit 4. The freewheeling diode DF has an anode electrically coupled to the second terminal of the light emitting unit 3, and a cathode electrically coupled to the first terminal of the energy-storing inductor LS.
Cooperation of the energy-storing inductor LS and the freewheeling diode DF may reduce a ripple of a current flowing through the light emitting unit 3.
In summary, the light emitting device 100 of this disclosure includes the control circuit 5, the switch unit 4, the mutual inductance device 2, the rectifier circuit 1, the filter circuit 6 and the energy-storing capacitor CS that cooperate with each other to synchronize the current that charges the energy-storing capacitor CS with the AC voltage signal, thereby resulting in a high power factor of the light emitting device 100. By virtue of cooperation of the control circuit 5 and the sensing resistor RS of the feedback unit 7, the current that flows through the light emitting unit 3 may be effectively stabilized. In addition, the control circuit 5 adjusts the duty cycle of the PWM signal according to the voltage at the power supply terminal thereof, thereby forming the voltage feedback mechanism that may stabilize the voltage at the power supply terminal.
While the present disclosure has been described in connection with what are considered the most practical embodiments, it is understood that this disclosure 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201310511789.2 | Oct 2013 | CN | national |
This application claims benefit from and is a divisional patent application of U.S. patent application Ser. No. 14/522835, which claims benefit and priority to Chinese Application No. 201310511789.2, filed on Oct. 25, 2013, which applications are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14522835 | Oct 2014 | US |
| Child | 15646720 | US |
