CN103491664A - Load driving device and method for light-emitting diode lamp tube and lighting device applied by same - Google Patents

Abstract

The invention discloses a load driving device and method for a light-emitting diode lamp tube and a lighting device applied by the same. When the light-emitting diode lamp tube is short-circuited, the low-pass filter is used for filtering the high-frequency pulse width modulation signal output by the control chip and providing a direct-current low voltage level to the pulse width modulation dimming pin of the control chip. In this way, the control chip stops outputting the pwm signal (completely) in response to the dc low voltage level provided by the low pass filter, so that all components in the load driving apparatus are prevented from being damaged by the short circuit of the led lamp.

Description

Load driving device and method for light-emitting diode lamp tube, and lighting device applied thereto

technical field

The invention relates to the technical field of capacitive load driving, and in particular to a load driving device and method for a light-emitting diode lamp tube, and a lighting device applied thereto. the

Background technique

With the advancement of semiconductor technology, the luminous brightness and luminous efficiency of light emitting diodes (LEDs) continue to increase. Light-emitting diode is a new type of cold light source, which has the advantages of long service life, small size, low power consumption, low pollution, high reliability, and suitable for mass production. Moreover, light-emitting diodes can be used in a wide range of fields, such as lighting devices ( illumination apparatus), liquid crystal display (liquid crystal display, LCD) or the backlight source of large billboards, etc. the

Taking a lighting device with an LED lamp as an example, the driving device for driving the LED lamp can use a PWM-based boost circuit or a Power conversion circuit (buck circuit). However, no matter which one is used, the protection measures for short circuit (short circuit) of the light-emitting diode tube are not perfect, so that it may cause damage to some parts in the driving device, and may even cause damage. Causes fire and combustion of some parts in the drive unit. the

Contents of the invention

In view of this, an exemplary embodiment of the present invention provides a load driving device, which includes: a power conversion circuit, a control chip, and a short circuit protection circuit. The power conversion circuit is used for receiving a DC input voltage, and responding to a pulse width modulation signal to provide a DC output voltage to a light-emitting diode lamp. The control chip is coupled to the power conversion circuit for generating the pulse width modulation signal to control the operation of the power conversion circuit, and the control chip has an output pin for outputting the pulse width modulation signal and a load for adjusting the pulse width modulation signal Period (duty cycle) PWM dimming pin. The short-circuit protection circuit is coupled between the output pin of the control chip and the PWM dimming pin, and is used to generate a short-circuit protection signal to the PWM dimming pin of the control chip when the LED tube is short-circuited , so that the output pin of the control chip stops outputting the pulse width modulation signal. the

In an exemplary embodiment of the present invention, the power conversion circuit may be a step-down circuit, and the step-down circuit may include: a diode, an inductor, a power switch, and a first resistor. The cathode of the diode is used to receive the DC input voltage, and is coupled to the first end of the LED tube. The first end of the inductor is coupled to the anode of the diode, and the second end of the inductor is coupled to the second end of the LED tube. The drain of the power switch is coupled to the anode of the diode and the first end of the inductor, and the gate of the power switch is used for receiving the pulse width modulation signal. The first resistor is coupled between the source of the power switch and a ground potential. the

In an exemplary embodiment of the present invention, the short-circuit protection circuit may be a low-pass filter, and the low-pass filter includes: a second resistor and a capacitor. The first end of the second resistor is coupled to the gate of the power switch and the output pin of the control chip, and the second end of the second resistor is coupled to the PWM dimming pin of the control chip. The first end of the capacitor is coupled to the second end of the second resistor and the PWM dimming pin of the control chip, and the second end of the capacitor is coupled to the ground potential. the

Another exemplary embodiment of the present invention provides a lighting device, which includes: a light emitting diode tube and the aforementioned load driving device. the

Still another exemplary embodiment of the present invention provides a load driving method, which includes: converting an input DC voltage into a DC output voltage in response to a pulse width modulation signal, thereby providing the DC output voltage for lighting a diode lamp; and when the LED lamp is short-circuited, it responds to a low-pass filtering means (low-pass filtering means) to stop generating the pulse width modulation signal, thereby stopping providing the DC output voltage to the LED lamp Tube. the

Based on the above, the present invention can use a low-pass filter (that is, a short-circuit protection circuit) to filter out the high-frequency pulse width modulation signal output by the control chip when the light-emitting diode lamp is short-circuited, and provide a DC low voltage level ( That is, short circuit protection signal) to the PWM dimming pin of the control chip. In this way, the control chip will respond to the DC low voltage level provided by the low-pass filter and (completely) stop outputting the pulse width modulation signal, so that all parts in the load driving device are protected from being affected by the LED light. The tube is damaged by a short circuit. the

Description of drawings

Fig. 1 has shown the schematic block diagram of the illuminating device (illumination apparatus) 10 of an exemplary embodiment of the present invention;

Fig. 2 has shown the implementation (implementation) schematic diagram of lighting device 10 of Fig. 1;

FIG. 3 shows a flowchart of a load driving method for an LED lamp according to an exemplary embodiment of the present invention. the

【Description of main component symbols】

10: lighting device

101: LED tube

103: Load drive device

105: Power conversion circuit

107: Control chip

109: Short circuit protection circuit

R1, Rcs, Rf: resistance

Ca, Cb, Cf: Capacitance

D1: Diode

L1: inductance

Q: (N type) power switch

GATE: the output pin of the control chip

PWM_D: PWM dimming pin of the control chip

VDDP: the operating power supply pin of the control chip

GNDP: the ground pin of the control chip

CS: Current detection pin of the control chip

VIN: the voltage input pin of the control chip

RT: The frequency setting pin of the control chip

LD: DC dimming pin of the control chip

ND: node

VND: node voltage

Vocp: over-current protection reference voltage

Ics: current

VDC_IN: DC input voltage

VDC_OUT: DC output voltage

PW: pulse width modulation signal

TS: trigger signal

LS: short circuit protection signal

VDD: operating power supply

GND: ground potential

S301, S303: each step of the flow chart of the load driving method for light-emitting diode lamps in an exemplary embodiment of the present invention

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. Elements/components using the same reference numerals in the drawings and the detailed description of the description represent the same or similar parts. the

FIG. 1 is a schematic block diagram of an illumination apparatus 10 according to an exemplary embodiment of the present invention, and FIG. 2 shows an implementation schematic diagram of the illumination apparatus 10 of FIG. 1 . Please refer to FIG. 1 and FIG. 2 together. The lighting device 10 includes: a light emitting diode lamp (light emitting diode lamp, LED lamp) 101 and a load driving apparatus (load driving apparatus) 103 . Wherein, the light-emitting diode lamp 101 is coupled to the load driving device 103 for emitting light in response to the DC output voltage VDC_OUT from the load driving device 103; in addition, the load driving device 103 is used for receiving the rectified and filtered DC input voltage VDC_IN , and respond to pulse width modulation control means (pulse width modulation control means, PWM control means) to provide a DC output voltage VDC_OUT to the LED lamp 101 . the

More clearly, the load driving device 103 includes: a power conversion circuit (power conversion circuit) 105, a control chip (control chip) 107, a short-circuit protection circuit (short-circuit protection circuit) 109, a resistor (resistor) R1, and a capacitor ( capacitor) Ca and Cb. Wherein, the power conversion circuit 105 is used for receiving the DC input voltage VDC_IN, and providing a DC output voltage VDC_OUT to the LED lamp 101 in response to a PWM signal PW output from the control chip 107 . the

In this exemplary embodiment, the power conversion circuit 105 may be a buck circuit (but not limited thereto), and it may include: a diode (such as a Schottky (Schottky) diode, but not Limited to this) D1, inductor (inductor) L1, (N-type) power switch (power switch) Q, and resistor Rcs. Among them, the cathode (cathode) of diode D1 is used to receive the DC input voltage VDC_IN, and is coupled to the light-emitting diode The first end of the lamp tube 101. The first end of the inductor L1 is coupled to the anode (anode) of the diode D1, and the second end of the inductor L1 is coupled to the second end of the LED lamp tube 101.

The drain of the (N-type) power switch Q is coupled to the anode of the diode D1 and the first end of the inductor L1, and the gate of the (N-type) power switch Q is used to receive the power from the control chip 107 The pulse width modulated signal PW. The resistor Rcs is coupled between the source (source) of the (N-type) power switch Q and the ground potential (GND). the

On the other hand, the control chip 107 is coupled to the power conversion circuit 105, and is used to generate a pulse width modulation signal PW in response to the power supply demand of the load (that is, the light-emitting diode lamp 101), so as to control the power conversion circuit (step-down circuit) )105 operation. In this exemplary embodiment, the control chip 107 may have an output pin (output pin) GATE for outputting the pulse width modulation signal PW and a pulse pin for adjusting the duty cycle (duty cycle) of the pulse width modulation signal PW. Wide modulation dimming pin (PWM dimming pin) PWM_D. Wherein, the duty cycle of the pulse width modulation signal PW will determine the ON/OFF time ratio of the LED tube 101 . If the 'ON' time is longer, the brightness of the LED tube 101 is higher; on the contrary, if the 'OFF' time is longer, the brightness of the LED tube 101 is lower. Obviously, by changing the duty cycle of the pulse signal input to the PWM dimming pin PWM_D of the control chip 107 , the brightness of the LED lamp 101 can be adjusted/determined. the

In addition, the short-circuit protection circuit 109 is coupled between the output pin GATE of the control chip 107 and the pulse width modulation dimming pin PWM_D, and is used for generating a short-circuit protection signal (such as : DC low voltage level (DC low voltage level)) LS to the pulse width modulation dimming pin PWM_D of the control chip 107, so that the output pin GATE of the control chip 107 (completely) stops outputting the pulse width modulation signal PW . the

To be more clear, the short-circuit protection circuit 109 can be designed as a low-pass filter (low-pass filter, which will be described in detail later). Based on this, the short circuit protection circuit 109 may include: a (filtering) resistor Rf and a (filtering) capacitor Cf. Wherein, the first end of the resistor Rf is coupled to the gate of the (N-type) power switch Q and the output pin GATE of the control chip 107, and the second end of the resistor Rf is coupled to the PWM dimming pin of the control chip 107. pin PWM_D; in addition, the first end of the capacitor Cf is coupled to the second end of the resistor Rf and the PWM dimming pin PWM_D of the control chip 107, and the second end of the capacitor Cf is coupled to the ground potential GND. the

Furthermore, the control chip 107 can also have a current detection pin CS, and the current detection pin CS of the control chip 107 will be coupled to the first end of the resistor Rcs (that is, the (N-type) power switch The node ND between the source of Q and the first end of the resistor Rcs). In this exemplary embodiment, the control chip 107 can detect the current Ics flowing through the resistor Rcs through the current detection pin CS, and decide whether to start an over-current protection mechanism (over-current protection mechanism, OCP mechanism) to protect The load driving device 103 is protected from damage caused by overcurrent. the

To be more clear, the control chip 107 has a built-in over-current protection reference voltage (for example: Vocp). Once the voltage VND (that is, Rcs×Ics) on the node ND is greater than the built-in over-current protection reference voltage Vocp, the control chip 107 will start the over-current protection mechanism, so as to gradually reduce the output voltage of the control chip 107. The duty cycle of the pulse width modulation signal PW output by the pin GATE is until the voltage VND (Rcs×Ics) on the node ND is smaller than the built-in over-current protection reference voltage Vocp (that is, no over-current occurs). the

Under the condition that the control chip 107 has the function of over-current protection, when the light-emitting diode tube 101 is short-circuited, the voltage VND (Rcs×Ics) on the node ND will rise rapidly to reach/reach the built-in overcurrent The current protects the reference voltage Vocp, so that the duty cycle of the PWM signal PW output by the output pin GATE of the control chip 107 gradually decreases until a high frequency PWM signal PW is formed. the

In this way, since the short-circuit protection circuit 109 has been designed as a low-pass filter, the short-circuit protection circuit 109 will continuously output the short-circuit protection signal (that is, DC low voltage level) LS to the pulse width modulation modulation of the control chip 107. Optical pin PWM_D (because high-frequency signals cannot pass through, and this is also the reason why the short-circuit protection circuit 109 is designed as a low-pass filter), so that the output pin GATE of the control chip 107 will (completely) stop the output pulse width modulation signal PW. In other words, at this time, the duty cycle of the pulse width modulation signal PW output by the output pin GATE of the control chip 107 is 0%, so that a complete circuit loop cannot be formed between the load driving device 103 and the light-emitting diode lamp 10, so that All components in the load driving device 103 are protected from being damaged by the short circuit of the LED tube 101 . the

On the other hand, the control chip 107 can also have a voltage input pin (input pin) VIN and an operation power pin (operation power pin) VDDP. Moreover, the control chip 107 can receive the DC input voltage VDC_IN through the voltage input pin VIN, and convert (for example step down) the received DC input voltage VDC_IN to generate the operating power (VDD) on the operating power pin VDDP. Certainly, the control chip 107 may also have a ground pin GNDP coupled to the ground potential GND. the

In addition, the (trigger) capacitor Ca is coupled between the operation power supply pin VDDP of the control chip 107 and the pulse width modulation dimming pin PWM_D, and is used for the initial stage of starting the LED lamp 101 by the load driving device 103 (initial phase, even the initial phase of starting a new/non-short-circuited light-emitting diode (not shown)), provide a trigger signal (trigger signal) TS to the pulse width modulation dimming pin PWM_D of the control chip 107, according to the control The output pin GATE of the chip 107 outputs the (initial/preset) pulse width modulation signal PW to control the operation of the power conversion circuit 105 . the

Furthermore, the control chip 107 may also have a DC dimming pin (DC dimming pin) LD. However, since the above exemplary embodiment adjusts the brightness of the light-emitting diode tube 101 by controlling the PWM dimming pin PWM_D of the chip 107, in this exemplary embodiment, the DC dimming of the control chip 107 The pin LD must be coupled to the ground potential GND through a capacitor Cb, and directly coupled to the operating power pin VDDP of the control chip 107 (that is, the function of the DC dimming pin LD of the control chip 107 to be disabled) . the

It can be seen that, if the brightness of the LED lamp 101 is to be adjusted through the DC dimming pin LD of the control chip 107, the pulse width modulation dimming pin PWM_D of the control chip 107 must be directly coupled to The operation power supply pin VDDP of the control chip 107 (that is, the function of the pulse width modulation dimming pin PWM_D of the control chip 107 is disabled), and the DC dimming pin LD of the control chip 107 can be changed to receive a default range Adjust the voltage (for example: 0-0.25V, but not limited thereto) to adjust the brightness of the LED tube 101 . the

Even, the control chip 107 can also have a frequency setting pin (frequency setting pin) RT. Based on this, in this exemplary embodiment, the resistor R1 can be coupled between the frequency setting pin RT of the control chip 107 and the output pin GATE, so as to control the pulse output by the output pin GATE of the control chip 107. The frequency of the wide modulation signal PW is set/adjusted. However, if the frequency of the pulse width modulation signal PW output by the output pin GATE of the control chip 107 is to be fixed, the frequency setting pin RT of the control chip 107 can be coupled to the ground potential GND ( That is, the function of the frequency setting pin RT of the control chip 107 is disabled). the

It can be seen from this that the present invention can use a low-pass filter (short-circuit protection circuit 109) to filter out the high-frequency pulse-width modulation signal PW output by the control chip 107 when a short-circuit occurs in the light-emitting diode lamp 101, and provide DC The low voltage level (short circuit protection signal LS) is sent to the PWM dimming pin PWM_D of the control chip 107 . In this way, the control chip 107 will respond to the DC low voltage level (short circuit protection signal LS) provided by the low pass filter (short circuit protection circuit 109) and (completely) stop outputting the pulse width modulation signal PW, according to All parts in the load driving device 103 are prevented from being damaged by the short circuit of the LED tube 101 . the

In addition, although the power conversion circuit 105 in the above exemplary embodiment is described as a step-down circuit as an example, the present invention is not limited thereto. In other words, the power conversion circuit 105 can be changed to other types of power conversion architectures, such as: boost circuit (boost circuit), boost-buck circuit (boost- buck circuit), etc., everything depends on the actual design/application. the

On the other hand, based on the disclosure/teaching of the above exemplary embodiments, FIG. 3 shows a flow chart of a load driving method for an LED lamp according to an exemplary embodiment of the present invention. Please refer to Fig. 3, the load driving method of the present exemplary embodiment includes:

Converting an input DC voltage into a DC output voltage in response to a pulse width modulation signal, so as to provide the DC output voltage to the LED lamp (step S301); and

When the LED tube is short-circuited, a low-pass filtering means is used to stop generating the PWM signal, and then stop providing the DC output voltage to the LED tube (step S303 ). the

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention. the

Claims (13)

1. a load drive device comprises:

One power-switching circuit, for receiving a direct current input voltage, and react on a pulse-width signal and provide a direct current output voltage to a light-emitting diode lamp tube;

One control chip, couple this power-switching circuit, for generation of this pulse-width signal, to control the running of this power-switching circuit, wherein this control chip has an output pin of this pulse-width signal of output and an impulse width modulation and light adjusting pin of adjusting a duty cycle of this pulse-width signal; And

One short-circuit protection circuit; be coupled between this output pin and this impulse width modulation and light adjusting pin; for when this light-emitting diode lamp tube is short-circuited, produce a short-circuit protection signal to this impulse width modulation and light adjusting pin, make according to this this output pin stop exporting this pulse-width signal.

2. load drive device as claimed in claim 1, wherein this power-switching circuit is at least a reduction voltage circuit, and this reduction voltage circuit comprises:

One diode, its negative electrode is used for receiving this DC input voitage, and couples the first end of this light-emitting diode lamp tube;

One inductance, its first end couples the anode of this diode, and its second end couples the second end of this light-emitting diode lamp tube;

One power switch, its drain electrode couples the anode of this diode and the first end of this inductance, and its grid is for receiving this pulse-width signal; And

One first resistance, be coupled between the source electrode and an earthing potential of this power switch.

3. load drive device as claimed in claim 2, wherein this short-circuit protection circuit is a low pass filter, and this low pass filter comprises:

One second resistance, its first end couples grid and this output pin of this power switch, and its second end couples this impulse width modulation and light adjusting pin; And

One electric capacity, its first end couples the second end and this impulse width modulation and light adjusting pin of this second resistance, and its second end is coupled to this earthing potential.

4. load drive device as claimed in claim 2, wherein:

This control chip also has a gallon pin of the first end that is coupled to this first resistance; And

This control chip by this gallon pin with detection flows the electric current through this first resistance, and determine according to this whether to start an over current protection protection mechanism.

5. load drive device as claimed in claim 1, wherein this control chip also has an operating power pin, and this load drive device also comprises:

One electric capacity, be coupled between this operating power pin and this impulse width modulation and light adjusting pin, a starting stage for starting this light-emitting diode lamp tube, provide a triggering signal to this impulse width modulation and light adjusting pin, makes according to this this output pin export this pulse-width signal.

6. load drive device as claimed in claim 5, wherein this control chip also has:

One voltage input pin, wherein this control chip receives this DC input voitage by this voltage input pin, and this received DC input voitage is changed to produce an operating power on this operating power pin; And

One grounding pin, be coupled to this earthing potential.

7. a lighting device comprises:

One light-emitting diode lamp tube, luminous for reacting on a direct current output voltage; And

One load drive device, couple this light-emitting diode lamp tube, and this load drive device comprises:

One power-switching circuit, for receiving a direct current input voltage, and react on a pulse-width signal and provide this VD to this light-emitting diode lamp tube;

One control chip, couple this power-switching circuit, for generation of this pulse-width signal, to control the running of this power-switching circuit, wherein this control chip has an output pin of this pulse-width signal of output and an impulse width modulation and light adjusting pin of adjusting a duty cycle of this pulse-width signal; And

One short-circuit protection circuit; be coupled between this output pin and this impulse width modulation and light adjusting pin; for when this light-emitting diode lamp tube is short-circuited, produce a short-circuit protection signal to this impulse width modulation and light adjusting pin, make according to this this output pin stop exporting this pulse-width signal.

8. lighting device as claimed in claim 7, wherein this power-switching circuit is at least a reduction voltage circuit, and this reduction voltage circuit comprises:

One diode, its negative electrode is used for receiving this DC input voitage, and couples the first end of this light-emitting diode lamp tube;

One inductance, its first end couples the anode of this diode, and its second end couples the second end of this light-emitting diode lamp tube;

One power switch, its drain electrode couples the anode of this diode and the first end of this inductance, and its grid is for receiving this pulse-width signal; And

One first resistance, be coupled between the source electrode and an earthing potential of this power switch.

9. lighting device as claimed in claim 8, wherein this short-circuit protection circuit is a low pass filter, and this low pass filter comprises:

One second resistance, its first end couples grid and this output pin of this power switch, and its second end couples this impulse width modulation and light adjusting pin; And

One electric capacity, its first end couples the second end and this impulse width modulation and light adjusting pin of this second resistance, and its second end is coupled to this earthing potential.

10. lighting device as claimed in claim 8, wherein:

This control chip also has a gallon pin of the first end that is coupled to this first resistance; And

This control chip by this gallon pin with detection flows the electric current through this first resistance, and determine according to this whether to start an over current protection protection mechanism.

11. lighting device as claimed in claim 7, wherein this control chip also has an operating power pin, and this load drive device also comprises:

One electric capacity, be coupled between this operating power pin and this impulse width modulation and light adjusting pin, a starting stage for starting this light-emitting diode lamp tube, provide a triggering signal to this impulse width modulation and light adjusting pin, makes according to this this output pin export this pulse-width signal.

12. lighting device as claimed in claim 11, wherein this control chip also has:

One voltage input pin, wherein this control chip receives this DC input voitage by this voltage input pin, and this received DC input voitage is changed to produce an operating power on this operating power pin; And

One grounding pin, be coupled to this earthing potential.

13. a load driving method comprises:

React on a pulse-width signal and an input direct voltage is converted to a direct current output voltage, provide according to this this VD to a light-emitting diode lamp tube; And

When this light-emitting diode lamp tube is short-circuited, reacts on low-pass filtering means and stop producing this pulse-width signal, and then stopping providing this VD to this light-emitting diode lamp tube.

Images