Patent Publication Number: US-8970120-B2

Title: Lamp driving apparatus and illumination equipment using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 101149285, filed on Dec. 22, 2012. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an AC load driving technology, and more particularly to, a lamp driving apparatus and an illumination equipment using the same. 
     2. Description of Related Art 
     AC loads such as lamps in the market are generally lighted through a single high-voltage method, and such type of driving technology generally implements circuit protection measures such as open circuit protection and over-voltage protection according to a voltage signal in a lamp that is close to a ground potential (since it is easier to process with low-voltage signal), and said circuit protection measures are all required in actual applications. On the other hand, since the driving technology of a dual high-voltage method is novel, and two terminals of the lamp are all applied with high voltage signals, the conventional circuit protection measures designed for the driving technology which lights the lamp through the single high-voltage method is hard to be applied to the driving technology which lights the lamp through the dual high-voltage method. In this way, in order to innovate and break through the present known driving technology for the lamp, how to develop circuit protection measures suitable for the driving technology which lights the lamp through the dual high-voltage method is an urgent issue to be solved in the field. 
     SUMMARY OF THE INVENTION 
     Accordingly, a lamp driving apparatus according to an exemplary embodiment of the invention is provided, including: a power switching circuit, an LC resonator, a control chip and an open lamp and over-voltage detection circuit. Therein, the power switching circuit is coupled between a DC input high-voltage and a ground potential, and configured to switch and output the DC input high-voltage and the ground potential in response to two output signals with a phase difference of 180 degrees, so as to generate a square signal. The LC resonator is coupled to an output of the power switching circuit and configured to receive and convert the square signal, so as to generate a sinusoidal driving signal for driving a lamp. 
     The control chip is coupled to an input of the power switching circuit, and operated under a DC operating voltage. The control chip is configured to provide the two output signals with the phase difference of 180 degrees, so as to control operation of the power switching circuit. The open lamp and over-voltage detection circuit is coupled to control chip, and connected across two terminals of the lamp. The open lamp and over-voltage detection circuit is configured to: detect whether the lamp is opened or over-voltage; and send, when any one of the two terminals of the lamp is opened or the lamp is over-voltage, an abnormal signal indicating that any one of the two terminals of the lamp is opened or the lamp is over-voltage, to the control chip. In this case, the control chip may further stop providing the two output signals with the phase difference of 180 degrees in response to the abnormal signal. 
     In an exemplary embodiment of the invention, the open lamp and over-voltage detection circuit may be further configured to send, when the lamp is normal, a normal signal indicating that the lamp is normal, to the control chip, so as to make the control chip to normally provide the two output signals with the phase difference of 180 degrees, so as to control the operation of the power switching circuit. 
     In an exemplary embodiment of the invention, the open lamp and over-voltage detection circuit includes first to fourth capacitors, a first and a second diodes, a first and a second Zener diodes, an NPN-type bipolar junction transistor, and first to third capacitors. A first terminal of the first capacitor is coupled to a first terminal among the two terminals of the lamp. A first terminal of the second capacitor is coupled to a second terminal of the first capacitor, and a second terminal of the second capacitor is coupled to the ground potential. A cathode of the first diode is coupled to the second terminal of the first capacitor, and an anode of the first diode is coupled to the ground potential. A cathode of the first Zener diode is coupled to the second terminal of the first capacitor. 
     A first terminal of the third capacitor is coupled to a second terminal among the two terminals of the lamp. A first terminal of the fourth capacitor is coupled to a second terminal of the third capacitor, and a second terminal of the fourth capacitor is coupled to the ground potential. A cathode of the second diode is coupled to the second terminal of the third capacitor, and an anode of the second diode is coupled to the ground potential. A cathode of the second Zener diode is coupled to the second terminal of the third capacitor, and an anode of the second Zener diode is coupled to an anode of the first Zener diode. 
     A base of the NPN-type bipolar junction transistor is coupled to the anodes of the first and the second Zener diodes, and an emitter of the NPN-type bipolar junction transistor is configured to send the normal signal or the abnormal signal. A first terminal of the first resistor is coupled to the DC operating voltage, and a second terminal of the first resistor is coupled to a collector of the NPN-type bipolar junction transistor. A first terminal of the second resistor is coupled to the emitter of the NPN-type bipolar junction transistor, and a second terminal of the second resistor is coupled to the ground potential. The third resistor is connected across the base and the emitter of the NPN-type bipolar junction transistor. 
     In an exemplary embodiment of the invention, the open lamp and over-voltage detection circuit can further include a fourth and a fifth resistors. Therein, the fourth resistor is connected in parallel with the first Zener diode, and the fifth resistor is connected in parallel with the second Zener diode. 
     In an exemplary embodiment of the invention, the normal signal and the abnormal signal can both be voltage signals. In this case, when any one of the two terminals of the lamp is opened or the lamp is over-voltage, a level of the abnormal signal is greater than a reference level built in the control chip; otherwise, when the lamp is normal, a level of the normal signal is less than the reference level. 
     In an exemplary embodiment of the invention, the LC resonator includes a resonant capacitor and a boost isolated transformer. Therein, a first terminal the resonant capacitor is configured to receive the square signal. The boost isolated transformer has a primary side and a secondary side. A first terminal of the primary side of the boost isolated transformer is coupled to a second terminal of the resonant capacitor; a second terminal of the primary side is coupled to the ground potential; a first terminal of the secondary side of the boost isolated transformer is coupled to the first terminal of the lamp; and a second terminal of the secondary side of the boost isolated transformer is coupled to the second terminal of the lamp. 
     In an exemplary embodiment of the invention, the two output signals with the phase difference of 180 degrees include a first pulse-width modulation signal and a second pulse-width modulation signal. In this case, the power switching circuit includes an upper-arm N-type field-effect transistor and a lower-arm N-type field-effect transistor. Therein, a gate of the upper-arm N-type field-effect transistor is configured to receive the first pulse-width modulation signal, a drain of the upper-arm N-type field-effect transistor is configured to receive the DC input high-voltage, and a source of the upper-arm N-type field-effect transistor is configured to output the square signal. A gate of the lower-arm N-type field-effect transistor is configured to receive the second pulse-width modulation signal, a drain of the lower-arm N-type field-effect transistor is coupled to the source of the upper-arm N-type field-effect transistor, and a source of the lower-arm N-type field-effect transistor is coupled to the ground potential. 
     In an exemplary embodiment of the invention, the control chip may be further configured to adjust duty cycles of the first and the second pulse-width modulation signals in response to the square signal, thereby regulating the sinusoidal driving signal. 
     In an exemplary embodiment of the invention, the provided lamp driving apparatus may further include an AC-to-DC power conversion circuit which is coupled to the power switching circuit, and configured to receive an AC input power and convert the AC input power, so as to provide the DC input high-voltage. The AC-to-DC power conversion circuit may be implemented by using a combination of a bridge rectifier and a filter capacitor, but the invention is not limited thereto. 
     In an exemplary embodiment of the invention, the provided lamp driving apparatus may further include a DC voltage regulation circuit which is configured to receive the DC input high-voltage, and perform a voltage regulation process to the DC input high-voltage, so as to generate the DC operating voltage required for the control chip in operation. The DC voltage regulation circuit may be implemented by using a Zener diode/other voltage regulation device with a value identical to the DC operating voltage required for the control chip in operation, but the invention is not limited thereto. 
     An illumination equipment according to another exemplary embodiment of invention is provided, including a lamp, and the above-mentioned lamp driving apparatus responsible for driving the lamp. 
     In light of the foregoing, a lamp driving apparatus and an illumination equipment using the same are provided. The provided lamp driving apparatus is responsible for driving a lamp. When any one of two terminals of the lamp is opened or the lamp is over-voltage, the provided driving apparatus stops driving the lamp, and thus achieving the purpose of open lamp and over-voltage protection/detection. In other words, the provided lamp driving apparatus utilizes the driving technology which lights the lamp with the dual high-voltage method and is provided with functions of open lamp and over-voltage protection/detection. 
     However, the above descriptions and the below embodiments are only used for explanation, and they do not limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a schematic diagram illustrating an illumination equipment  10  according to an exemplary embodiment of the invention. 
         FIG. 2  is a schematic diagram illustrating an implementation of a lamp driving apparatus  100  responsible for driving a lamp  200  according to an exemplary embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Descriptions of the invention are given with reference to the exemplary embodiments illustrated with accompanied drawings, wherein same or similar parts are denoted with same reference numerals. In addition, whenever possible, identical or similar reference numbers stand for identical or similar elements in the figures and the embodiments. 
       FIG. 1  is a schematic diagram illustrating an illumination equipment  10  according to an exemplary embodiment of the invention, and  FIG. 2  is a schematic diagram illustrating an implementation of a lamp driving apparatus  100  responsible for driving a lamp  200  according to an exemplary embodiment of the invention. Referring to  FIG. 1  and  FIG. 2  together, in the present exemplary embodiment, the lamp  200  can be a lamp of any types (e.g., a fluorescent lamp, a daylight lamp, a halogen lamp and so on, but the invention is not limited thereto, other lamps driven by adopting an AC method are also suitable), and the lamp  200  can emit light/generate a light source, in response to a sinusoidal driving signal SIN from the lamp driving apparatus  100 . 
     The lamp driving apparatus  100  drives/lights the lamp  200  through a dual high-voltage method, and includes a power switching circuit  101 , an LC resonator  103 , a control chip  105 , an open lamp and over-voltage detection circuit  107 , an AC-to-DC power conversion circuit  109 , and a DC voltage regulation circuit  111 . 
     The AC-to-DC power conversion circuit  109  is coupled to the power switching circuit  101 . The AC-to-DC power conversion circuit  109  is configured to receive an AC input power AC_IN (e.g., city power, but the invention is not limited thereto), and convert the received AC input power AC_IN (i.e., AC-to-DC power conversion), so as to provide a DC input high-voltage DC_HV. 
     More specifically, the AC-to-DC power conversion circuit  109  includes a bridge rectifier BR and a filter capacitor CF. The bridge rectifier BR is configured to receive the AC input power AC_IN, and perform a (full wave) rectification to the received AC input power AC_IN, so as to output the DC input high-voltage DC_HV. Further, the filter capacitor CF is coupled to an output of the bridge rectifier BR, and configured to filter the DC input high-voltage DC_HV, so as to stabilize the DC input high-voltage DC_HV. It should be noted that, although the AC-to-DC power conversion circuit  109  of the present exemplary embodiment is implemented by using a full-bridge rectification architecture, the AC-to-DC power conversion circuit  109  may also be implemented by using a half-bridge rectification architecture, depending on practical design/application requirements. 
     The DC voltage regulation circuit  111  is configured to receive the DC input high-voltage DC_HV from the AC-to-DC power conversion circuit  109 , and perform a voltage regulation process to the DC input high-voltage DC_HV, so as to generate a DC operating voltage IC_VCC (e.g., 10 to 15V, but the invention is not limited thereto) required for the control chip  105  in operation. 
     More specifically, the DC voltage regulation circuit  111  includes a series resistor network R_NET, a regulation capacitor CR and a regulation Zener diode ZDR. A first terminal of the series resistor network R_NET is configured to receive the DC input high-voltage DC_HV, and a second terminal of the series resistor network R_NET is configured to output the DC operating voltage IC_VCC to the control chip  105 . The regulation capacitor CR is coupled between the second terminal of the series resistor network R_NET and a ground potential GND. A cathode of the regulation Zener diode ZDR is coupled to the second terminal of the series resistor network R_NET, and an anode of the regulation Zener diode ZDR is coupled to the ground potential GND. It should be noted that, although the DC voltage regulation circuit  111  of the present exemplary embodiment is implemented by using the regulation Zener diode ZDR, the DC voltage regulation circuit  111  may also be implemented by using other voltage regulation device(s) other than the regulation Zener diode ZDR, depending on practical design/application requirements. 
     The power switching circuit  101  is coupled between the DC input high-voltage DC_HV and the ground potential GND. The power switching circuit  101  is configured to switch and output the DC input high-voltage DC_HV and the ground potential GND in response to two output signals with a phase difference of 180 degrees (e.g., two pulse-width modulation signals PWM 1  and PWM 2  with a phase difference of 180 degrees), so as to generate a square signal SQ. 
     More specifically, the power switching circuit  101  includes an upper-arm N-type field-effect transistor MU and a lower-arm N-type field-effect transistor ML. A gate of the upper-arm N-type field-effect transistor MU is configured to receive the pulse-width modulation signal PWM 1 , a drain of the upper-arm N-type field-effect transistor MU is configured to receive the DC input high-voltage DC_HV, and a source of the upper-arm N-type field-effect transistor MU is configured to output the square signal SQ. A gate of the lower-arm N-type field-effect transistor ML is configured to receive the pulse-width modulation signal PWM 2 , a drain of the lower-arm N-type field-effect transistor ML is coupled to the source of the upper-arm N-type field-effect transistor MU, and a source of the lower-arm N-type field-effect transistor ML is coupled to the ground potential GND. It should be noted that, although the power switching circuit  101  of the present exemplary embodiment is implemented by using a half-bridge switching architecture, the power switching circuit  101  may also be implemented by using a full-bridge switching architecture, depending on practical design/application requirements. 
     The LC resonator  103  is coupled to an output of the power switching circuit  101 . The LC resonator  103  is configured to receive and convert the square signal SQ from the power switching circuit  101 , so as to generate the sinusoidal driving signal SIN for driving the lamp  200 . More specifically, the LC resonator  103  includes a resonant capacitor C and a boost isolated transformer T. A first terminal the resonant capacitor C is configured to receive the square signal SQ. The boost isolated transformer T has a primary side P and a secondary side S. A first terminal of the primary side P of the boost isolated transformer T is coupled to a second terminal of the resonant capacitor C; a second terminal of the primary side P is coupled to the ground potential GND; a first terminal of the secondary side S of the boost isolated transformer T is coupled to a first terminal of the lamp  200 ; and a second terminal of the secondary side S of the boost isolated transformer T is coupled to a second terminal of the lamp  200 . 
     The control chip  105  is served as a control core of the lamp driving apparatus  100 . The control chip  105  is coupled to an input of the power switching circuit  101 , and operated under the DC operating voltage IC_VCC generated by the DC voltage regulation circuit  111 . The control chip  105  is configured to provide the two pulse-width modulation signals (PWM 1  and PWM 2 ) with the phase difference of 180 degrees, so as to control operation of the power switching circuit  101 . Moreover, the control chip  105  may be further configured to adjust duty cycles of the pulse-width modulation signals (PWM 1  and PWM 2 ), thereby regulating the sinusoidal driving signal SIN generated by the LC resonator  103 . 
     The open lamp and over-voltage detection circuit  107  is coupled to control chip  105 , and connected across two terminals of the lamp  200 . The open lamp and over-voltage detection circuit  107  is configured to: detect whether the lamp  200  is opened or over-voltage; and send, when any one of two terminals of the lamp  200  is opened or the lamp  200  is over-voltage, an abnormal signal AS indicating that any one of the two terminals of the lamp  200  is opened or the lamp  200  is over-voltage, to the control chip  105 . Accordingly, the control chip  105  stops providing the two pulse-width modulation signals (PWM 1  and PWM 2 ) with the phase difference of 180 degrees in response to the abnormal signal AS. In other words, when any one of the two terminals of the lamp  200  is over-voltage or the lamp  200  is over-voltage, the lamp driving apparatus  100  stops driving the lamp  200 . Obviously, the lamp driving apparatus  100  is provided with an open lamp and over-voltage protection/detection function/measure. 
     Otherwise, the open lamp and over-voltage detection circuit  107  may be further configured to send, when the lamp  200  is normal, a normal signal NS indicating that the lamp  200  is normal, to the control chip  105 , so as to make the control chip  105  to normally provide the two pulse-width modulation signals (PWM 1  and PWM 2 ) with the phase difference of 180 degrees, so as to control the operation of the power switching circuit  101 . In other words, when the lamp  200  is normal, the lamp driving apparatus  100  can normally drive the lamp  200 . 
     In the present exemplary embodiment, the open lamp and over-voltage detection circuit  107  includes capacitors C 1  to C 4 , diodes D 1  to D 2 , Zener diodes ZD 1  to ZD 2 , an NPN-type bipolar junction transistor (BJT) B 1  and resistors R 1  to R 5 . A first terminal of the capacitor C 1  is coupled to a first terminal among the two terminals of the lamp  200 . A first terminal of the capacitor C 2  is coupled to a second terminal of the capacitor C 1 , and a second terminal of the capacitor C 2  is coupled to the ground potential GND. A cathode of the diode D 1  is coupled to the second terminal of the capacitor C 1 , and an anode of the diode D 1  is coupled to the ground potential GND. 
     A first terminal of the capacitor C 3  is coupled to a second terminal among the two terminals of the lamp  200 . A first terminal of the capacitor C 4  is coupled to a second terminal of the capacitor C 3 , and a second terminal of the capacitor C 4  is coupled to the ground potential GND. A cathode of the diode D 2  is coupled to the second terminal of the capacitor C 3 , and an anode of the diode D 2  is coupled to the ground potential GND. A cathode of the Zener diode ZD 1  is coupled to the second terminal of the capacitor C 1 ; a cathode of the Zener diode ZD 2  is coupled to the second terminal of the capacitor C 3 ; and an anode of the Zener diode ZD 2  is coupled to an anode of the Zener diode ZD 1 . The resistor R 4  is connected in parallel with the Zener diode ZD 1 , and the resistor R 5  is connected in parallel with the Zener diode ZD 2 . It should be noted that, the resistors R 4  and R 5  are optional. 
     A base of the NPN-type bipolar junction transistor B 1  is coupled to the anodes of the Zener diodes (ZD 1  and ZD 2 ), and an emitter of the NPN-type bipolar junction transistor B 1  is configured to send the normal signal NS or the abnormal signal AS to the control chip  105 . A first terminal of the resistor R 1  is coupled to the DC operating voltage IC_VCC, and a second terminal of the resistor R 1  is coupled to a collector of the NPN-type bipolar junction transistor B 1 . A first terminal of the resistor R 2  is coupled to the emitter of the NPN-type bipolar junction transistor B 1 , and a second terminal of the resistor R 2  is coupled to the ground potential GND. The resistor R 3  is connected across the base and the emitter of the NPN-type bipolar junction transistor B 1 . 
     In the present exemplary embodiment, the normal signal NS and the abnormal signal AS may both be voltage signals (V NS , V AS ). In this case, when any one of the two terminals of the lamp  200  is opened or the lamp  200  is over-voltage, a level of the abnormal signal AS (V AS , for instance, when the NPN-type bipolar junction transistor B 1  is ON and operated in a saturation region, V AS =(IC_VCC*R 2 )/(R 1 +R 2 )&gt;5V, but the invention is not limited thereto) is greater than a reference level Vref (e.g., 4V, but the invention is not limited thereto) built in the control chip  105 ; otherwise, when the lamp  200  is normal, a level of the normal signal NS (V NS , for instance, when the NPN-type bipolar junction transistor B 1  is OFF, V NS &lt;4V, but the invention is not limited thereto) is less than the reference level Vref (=4V). 
     Based on above, when the first terminal of the lamp  200  is opened, a potential at the second terminal of the lamp  200  is significantly increased, so that the NPN-type bipolar junction transistor B 1  is ON and operated in the saturation region. In this case, the open lamp and over-voltage detection circuit  107  is activated to send the abnormal signal AS (V AS &gt;5V) associated/related to the lamp  200  being opened, to the control chip  105 . Once the control chip  105  has determined that the level of the abnormal signal AS (V AS &gt;5V) is greater than the reference level Vref (=4V) being built in, the control chip  105  stops providing the two pulse-width modulation signals (PWM 1  and PWM 2 ) with the phase difference of 180 degrees, so as to make the lamp driving apparatus  100  to stop driving the lamp  200 , thereby achieving the purpose of open lamp protection. 
     Similarly, when the second terminal of the lamp  200  is opened, a potential at the first terminal of the lamp  200  is significantly increased, so that the NPN-type bipolar junction transistor B 1  is ON and operated in the saturation region. In this case, the open lamp and over-voltage detection circuit  107  is activated to send the abnormal signal AS (V AS &gt;5V) associated/related to the lamp  200  being opened, to the control chip  105 . Once the control chip  105  has determined that the level of the abnormal signal AS (V AS &gt;5V) is greater than the reference level Vref (=4V) being built in, the control chip  105  stops providing the two pulse-width modulation signals (PWM 1  and PWM 2 ) with the phase difference of 180 degrees, so as to make the lamp driving apparatus  100  to stop driving the lamp  200 , thereby achieving the purpose of open lamp protection. 
     On the other hand, when the lamp  200  is over-voltage, for instance, when a peak-to-peak value of the sinusoidal driving signal SIN is greater than a predetermined tolerance value, the Zener diodes ZD 1  and ZD 2  are in breakdown, so that the NPN-type bipolar junction transistor B 1  is ON and operated in the saturation region. In this case, the open lamp and over-voltage detection circuit  107  is activated to send the abnormal signal AS (V AS &gt;5V) associated/related to the lamp  200  being over-voltage, to the control chip  105 . Once the control chip  105  has determined that the level of the abnormal signal AS (V AS &gt;5V) is greater than the reference level Vref (=4V) being built in, the control chip  105  stops providing the two pulse-width modulation signals (PWM 1  and PWM 2 ) with the phase difference of 180 degrees, so as to make the lamp driving apparatus  100  to stop driving the lamp  200 , thereby achieving the purpose of over-voltage protection. 
     Of course, when the lamp  200  is normal, the NPN-type bipolar junction transistor B 1  is OFF. In this case, the open lamp and over-voltage detection circuit  107  is inactivated to send the normal signal NS (V NS &lt;4V) associated/related to the lamp  200  being normal, to the control chip  105 . Once the control chip  105  has determined that the level of the abnormal signal NS (V NS &lt;4V) is less than the reference level Vref (=4V) being built in, the control chip  105  normally provides the two pulse-width modulation signals (PWM 1  and PWM 2 ) with the phase difference of 180 degrees to control the operation of the power switching circuit  101 , so as to make the lamp driving apparatus  100  to normally drive the lamp  200 . 
     Obviously, it can be known from disclosures/teachings of foregoing exemplary embodiments that, the lamp driving apparatus  100  utilizes a driving technology/architecture that lights the lamp  200  through the dual high-voltage method, and based on the open lamp and over-voltage detection circuit  107 , the lamp driving apparatus  100  is provided with the open lamp and over-voltage protection/detection function/measure. It should be noted that, although the foregoing exemplary embodiments is illustrated using a circuit implementation of the open lamp and over-voltage detection circuit  107  as an example, but the invention is not limited thereto. In other words, as long as said functions of the open lamp and over-voltage detection circuit  107  remains unchanged, the circuit implementation of the open lamp and over-voltage detection circuit  107  can be appropriately altered or redesigned. 
     In summary, a lamp driving apparatus and an illumination equipment using the same are provided. The provided lamp driving apparatus is responsible for driving a lamp. When any one of two terminals of the lamp is opened or the lamp is over-voltage, the provided driving apparatus stops driving the lamp, and thus achieving the purpose of open lamp and over-voltage protection/detection. In other words, the provided lamp driving apparatus utilizes the driving technology which lights the lamp with the dual high-voltage method and is provided with functions of open lamp and over-voltage protection/detection. 
     On the other hand, the provided lamp driving apparatus can at least realize/achieve the following advantages. 
     1. Applicability in lamps with different powers. 
     2. Easy to setup and adjust a protection point when replacing different lamps. 
     3. Regardless of lamps with large or small powers, over-voltage or open circuit protection voltage can all be adjusted to fall within a safe usage range. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this specification provided they fall within the scope of the following claims and their equivalents. 
     Any of the embodiments or any of the claims of the invention does not need to achieve all of the advantages or features disclosed by the present invention. Moreover, the abstract and the headings are merely used to aid in searches of patent files and are not intended to limit the scope of the claims of the present invention.