Driving circuit capable of adaptively switching current of light emitting diode

Abstract

The invention discloses a driving circuit for adaptively switching current of a light emitting diode. The optical driver at least comprises a first transistor, a first switching component, a second transistor, a third transistor and an operational amplifier. The first end of the first transistor is connected with the first input end of the operational amplifier. The first end of the first switching assembly is connected with the control end of the first transistor. The control end of the second transistor is connected with the second end of the first switching assembly. The first end of the third transistor is connected with one or more light-emitting diodes. The second end of the third transistor is connected with the first end of the second transistor and the second input end of the operational amplifier. The output end of the operational amplifier is connected with the control end of the third transistor.

Description

Technical Field

[0001] The invention relates to a light emitting diode driving circuit, in particular to a driving circuit for adaptively switching the light emitting diode current. Background Art

[0002] Conventional optical drivers are often used to drive light-emitting diodes to emit light. A switch component is additionally provided between the output end of the operational amplifier of the conventional optical driver and the control end of the transistor, and the first end of the transistor is connected to the light-emitting diode. However, the additional switch component will increase the parasitic capacitance in the conventional optical driver, delaying the time for the conventional optical driver to drive the light-emitting diode to emit light. Therefore, in order to quickly drive the light-emitting diode to emit light at the desired brightness on time at the specified time, the circuit component configuration and operation of the conventional optical driver need to be further improved. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a driving circuit for adaptively switching the current of a light-emitting diode in view of the shortcomings of the prior art. The driving circuit for adaptively switching the current of a light-emitting diode is suitable for driving one or more light-emitting diodes of a display to emit light. The driving circuit for adaptively switching the current of a light-emitting diode comprises a control circuit, a reference current source, a first transistor, a first switching component, a second transistor, a third transistor and an operational amplifier. The control circuit is connected to the display. The control circuit is configured to output a reference current control signal according to the brightness information of the display. The input end of the reference current source is coupled to a common voltage. The control end of the reference current source is connected to the control circuit. The reference current source determines a current value of a reference current according to the reference current control signal and outputs the reference current. The first end of the first transistor is connected to the output end of the reference current source and the control end of the first transistor. The second end of the first transistor is grounded. The first end of the first switching component is connected to the control end of the first transistor. The control end of the second transistor is connected to the second end of the first switching component. The first end of the third transistor is connected to the display. The second end of the third transistor is connected to the first end of the second transistor. The second end of the second transistor is grounded. The first input end of the operational amplifier is connected to the first end of the first transistor. The second input terminal of the operational amplifier is connected to the second terminal of the third transistor. The output terminal of the operational amplifier is connected to the control terminal of the third transistor.

[0004] As described above, the present invention provides a driving circuit for adaptively switching the current of a light emitting diode. The driving circuit for adaptively switching the current of a light emitting diode of the present invention adopts a circuit component configuration different from that of a conventional optical driver. Compared with a conventional optical driver, the driving circuit for adaptively switching the current of a light emitting diode of the present invention can achieve faster driving of one or more light emitting diodes (e.g., a plurality of light emitting diodes connected in series to form a light emitting diode string) of a display to emit light as desired.

[0005] To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are only for reference and description and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 FIG. 4 is a block diagram of a driving circuit for adaptively switching a light emitting diode current according to the first to third embodiments of the present invention.

[0007] Figure 2 FIG. 1 is a circuit diagram of a driving circuit for adaptively switching a light emitting diode current according to a first embodiment of the present invention.

[0008] Figure 3 FIG. 1 is a circuit diagram of a light emitting diode driving circuit of a driving circuit for adaptively switching light emitting diode current according to a first embodiment of the present invention.

[0009] Figure 4 FIG. 1 is a waveform diagram of signals of a driving circuit for adaptively switching a light emitting diode current according to the first embodiment of the present invention.

[0010] Figure 5 FIG. 4 is a circuit diagram of a driving circuit for adaptively switching a light emitting diode current according to a second embodiment of the present invention.

[0011] Figure 6 FIG. 1 is a circuit diagram of a light emitting diode driving circuit for adaptively switching light emitting diode current according to a second embodiment of the present invention.

[0012] Figure 7 FIG. 1 is a waveform diagram of signals of a driving circuit for adaptively switching the current of a light emitting diode according to a second embodiment of the present invention.

[0013] Figure 8 FIG. 4 is a circuit diagram of a driving circuit for adaptively switching a light emitting diode current according to a third embodiment of the present invention.

[0014] Fig. 9 FIG. 1 is a circuit diagram of a light emitting diode driving circuit for adaptively switching light emitting diode current according to a third embodiment of the present invention.

[0015] Fig.10FIG. 1 is a waveform diagram of signals of a driving circuit for adaptively switching a light emitting diode current according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0016] The following is an explanation of the embodiments of the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are only simple schematic illustrations and are not depicted according to actual dimensions. It is stated in advance. The following embodiments will further explain the relevant technical contents of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention. In addition, the term "or" used herein may include any one or more combinations of the associated listed items depending on the actual situation.

[0017] See also Figures 1 to 4 ,in Figure 1 is a block diagram of a driving circuit for adaptively switching a light emitting diode current according to the first to third embodiments of the present invention, Figure 2 is a circuit diagram of a driving circuit for adaptively switching light emitting diode current according to a first embodiment of the present invention, Figure 3 A circuit diagram of a light emitting diode driving circuit of a driving circuit for adaptively switching light emitting diode current according to a first embodiment of the present invention; Figure 4 FIG. 1 is a waveform diagram of signals of a driving circuit for adaptively switching a light emitting diode current according to the first embodiment of the present invention.

[0018] like Figure 1 As shown, the driving circuit for adaptively switching the LED current of the present invention includes an LED driving circuit 100 and a control circuit 20, which are used to drive one or more LEDs (for example, a plurality of LEDs connected in series to form an LED string) of the display 99 to emit light.

[0019] In the first embodiment, the LED driving circuit 100 may include: Figure 2 The light emitting diode driving circuit 101 is shown.

[0020] like Figure 2 and Figure 3 As shown, the light-emitting diode driving circuit 101 may include a reference current source Iref, a first transistor T1, a first switching element SW1, a second transistor T2, a third transistor T3, an operational amplifier ER, a second switching element SW2, a third switching element SW3, a fourth transistor T4, a fifth transistor T5 and a fourth switching element SW4, but the present invention is not limited thereto. In practice, some circuit components in the light-emitting diode driving circuit 101 may be omitted or replaced according to actual needs.

[0021] The input terminal of the reference current source Iref is coupled to the common voltage VDD. The first terminal of the first transistor T1 is connected to the output terminal of the reference current source Iref and the control terminal of the first transistor T1. The second terminal of the first transistor T1 is grounded.

[0022] The first end of the first switching component SW1 is connected to the control end of the first transistor T1. The control end of the second transistor T2 is connected to the second end of the first switching component SW1. The first end of the second transistor T2 is connected to the second end of the third transistor T3. The second end of the second transistor T2 is grounded.

[0023] A first terminal of the second switching element SW2 is connected to the second terminal of the first switching element SW1 and the control terminal of the second transistor T2. A second terminal of the second switching element SW2 is grounded.

[0024] The first input terminal of the operational amplifier ER, for example, the non-inverting input terminal, is connected to the first terminal of the first transistor T1. The second input terminal of the operational amplifier ER, for example, the inverting input terminal, is connected to the first terminal of the third switching component SW3 and the first terminal of the fourth switching component SW4. The output terminal of the operational amplifier ER is connected to the control terminal of the third transistor T3.

[0025] The first end of the third transistor T3 is connected (via the pin PIN1 of the light emitting diode driving circuit) to one or more light emitting diodes of the display 99. The second end of the third switching component SW3 is connected to a node between the second end of the third transistor T3 and the first end of the second transistor T2. The second end of the fourth switching component SW4 is connected to a node between the second end of the fourth transistor T4 and the first end of the fifth transistor T5.

[0026] The first end of the fourth transistor T4 is coupled to the shared voltage VDD. The control end of the fourth transistor T4 is connected to the output end of the operational amplifier ER. The first end of the fifth transistor T5 is connected to the second end of the fourth transistor T4. The second end of the fifth transistor T5 is grounded. The control end of the fifth transistor T5 is connected to the first end of the first transistor T1.

[0027] The control circuit 20 may be connected to the control end of the reference current source Iref and may be connected to the display 99 or a detection circuit for detecting the display 99. The control circuit 20 may obtain the brightness information BRFS of the display 99 from the display 99. The control circuit 20 may output a reference current control signal CRS to the reference current source Iref of the light emitting diode driving circuit 101 according to the brightness information BRFS of the display 99.

[0028] When the control terminal of the reference current source Iref receives a reference current control signal CRS from the control circuit 20 , the reference current source Iref determines a current value of a reference current according to the reference current control signal CRS, and outputs the reference current to the first terminal of the first transistor T1 .

[0029] The control circuit 20 can be connected to a control end of the first switching element SW1 , a control end of the second switching element SW2 , a control end of the third switching element SW3 , and a control end of the fourth switching element SW4 .

[0030] The control circuit 20 can output the following information based on the brightness information BRFS of the display 99: Figure 2 and Figure 4 A pulse width modulation inverted level signal PWMB is shown to the control end of the second switching element SW2 and the control end of the fourth switching element SW4.

[0031] The second switching element SW2 and the fourth switching element SW4 operate according to the pulse width modulation inverted level signal PWMB received from the control circuit 20. Figure 4 As shown, the second switching element SW2 and the fourth switching element SW4 are turned on in the working period of the PWM inverse level signal PWMB (aligned with the non-working period of the PWM signal PWM).

[0032] When the second switching element SW2 and the fourth switching element SW4 are turned on, the second transistor T2 is grounded through the second switching element SW2 so that the second transistor T2 stops operating, and the voltage of the node between the second end of the fourth transistor T4 and the first end of the fifth transistor T5 is input to the second input end, such as the inverting input end, of the operational amplifier ER through the fourth switching element SW4. At the same time, the first input end, such as the non-inverting input end, of the operational amplifier ER receives the voltage of the first end of the first transistor T1.

[0033] As a result, the voltage of the second input terminal, for example the inverting input terminal, of the operational amplifier OPA is directly pulled to the voltage of the node between the second terminal of the fourth transistor T4 and the first terminal of the fifth transistor T5 connected to the second terminal of the fourth switching element SW4 .

[0034] The operational amplifier ER multiplies the voltage difference between the voltage of the node between the second end of the fourth transistor T4 and the first end of the fifth transistor T5 and the voltage of the first end of the first transistor T1 by a gain to output an operational amplification signal to the control end of the third transistor T3 to control the operation of the third transistor T3, thereby maintaining the setting of the feedback path bias point of the display 99.

[0035] In this way, the effect of driving the display 99 to emit light at high speed is achieved.

[0036] The control circuit 20 can output the following information based on the brightness information BRFS of the display 99: Figure 2 and Figure 4 A pulse width modulation signal PWM is shown to the control end of the first switching element SW1 and the control end of the third switching element SW3.

[0037] The first switching element SW1 and the third switching element SW3 operate according to the pulse width modulation signal PWM received from the control circuit 20. Figure 4 As shown, the first switching element SW1 and the third switching element SW3 are turned on within the working cycle of the pulse width modulation signal PWM.

[0038] When the first switching component SW1 and the third switching component SW3 are turned on, the second transistor T2 is connected to the control terminal of the first transistor T1 through the first switching component SW1, and the voltage of the node between the second terminal of the third transistor T3 and the first terminal of the second transistor T2 is input to the second input terminal, such as the inverting input terminal, of the operational amplifier ER through the third switching component SW3. At the same time, the first input terminal, such as the non-inverting input terminal, of the operational amplifier ER receives the voltage of the first terminal of the first transistor T1.

[0039] In this case, the operational amplifier ER multiplies the voltage difference between the voltage of the node between the second end of the third transistor T3 and the first end of the second transistor T2 and the voltage of the first end of the first transistor T1 by a gain to output an operational amplification signal to the control end of the third transistor T3 to control the operation of the third transistor T3, thereby appropriately adjusting the current ILED of the display 99.

[0040] like Figure 2 As shown, in the optical driver configuration of the present invention, no switch component or switching component is set between the output end of the operational amplifier ER and the control end of the third transistor T3 to prevent the optical driver of the present invention from being affected by the parasitic capacitance Cgs between the gate and the source of the third transistor T3 itself and the parasitic capacitance Cgd between the gate and the drain, which affects the reaction speed of driving the display 99 to turn on. When the current is off, the feedback bias point and the signal of the control end of the third transistor T3 can be maintained at a bias state close to that when the current is turned on. In this way, when the current is turned on, it can quickly respond to the appropriate bias point, thereby quickly turning on the required current.

[0041] See also Figures 5 to 7 ,in Figure 5 is a circuit diagram of a driving circuit for adaptively switching light emitting diode current according to a second embodiment of the present invention, Figure 6 FIG. 1 is a circuit diagram of a light emitting diode driving circuit of a driving circuit for adaptively switching light emitting diode current according to a second embodiment of the present invention. Figure 7FIG. 1 is a waveform diagram of signals of a driving circuit for adaptively switching the current of a light emitting diode according to a second embodiment of the present invention.

[0042] The similarities between the second embodiment of the present invention and the first embodiment are not described in detail herein.

[0043] The difference between the second embodiment of the present invention and the first embodiment is that Figure 5 and Figure 6 As shown, the LED driving circuit 102 of the driving circuit for adaptively switching the LED current according to the second embodiment of the present invention further includes a first capacitor C1, a second capacitor C2 and a fifth switching element SW5.

[0044] A first end of the first capacitor C1 is connected to the control end of the first transistor T1. A second end of the first capacitor C1 is grounded. A first end of the second capacitor C2 is connected to the first end of the first switching component SW1. A second end of the second capacitor C2 is grounded.

[0045] A first end of the fifth switch element SW5 is connected to the control end of the first transistor T1 and the first end of the first capacitor C1. A second end of the fifth switch element SW5 is connected to the first end of the first switch element SW1 and the first end of the second capacitor C2.

[0046] The control terminal of the fifth switch element SW5 can be connected to the control circuit 20 to receive the pulse width modulation signal PWM from the control circuit 20 .

[0047] like Figure 7 As shown, the fifth switch element SW5 operates according to the pulse width modulation signal PWM received from the control circuit 20. The first switch element SW1, the third switch element SW3 and the fifth switch element SW5 are all turned on within the working cycle of the pulse width modulation signal PWM.

[0048] See also Figures 8 to 10 ,in Figure 8 is a circuit diagram of a driving circuit for adaptively switching light emitting diode current according to a third embodiment of the present invention, Fig. 9 FIG. 1 is a circuit diagram of a light emitting diode driving circuit of a driving circuit for adaptively switching light emitting diode current according to a third embodiment of the present invention. Fig.10 FIG. 1 is a waveform diagram of signals of a driving circuit for adaptively switching a light emitting diode current according to a third embodiment of the present invention.

[0049] The similarities between the third embodiment of the present invention and the second and first embodiments are not described in detail herein.

[0050] The difference between the third embodiment of the present invention and the second embodiment is that Figure 8 and Fig. 9As shown, the LED driving circuit 103 of the driving circuit for adaptively switching the LED current according to the second embodiment of the present invention further includes a sixth switching element SW6.

[0051] like Figure 5 and Figure 6 As shown, in the LED driving circuit 102 of the second embodiment, the first end of the second capacitor C2 is coupled to the reference voltage VF, or the voltage of the node between the first end of the second capacitor C2 and the second end of the fifth switch element SW5 is the reference voltage VF.

[0052] In contrast, Figure 8 and Fig. 9 As shown, in the LED driving circuit 103 of the third embodiment, a first terminal of the sixth switch element SW6 is coupled to the common voltage VDD, and a second terminal of the sixth switch element SW6 is connected to a first terminal of the second capacitor C2, a second terminal of the fifth switch element SW5, and a first terminal of the first switch element SW1.

[0053] The control terminal of the sixth switch element SW6 can be connected to the control circuit 20 to receive a pulse width modulation inverted level signal PWMB from the control circuit 20 .

[0054] like Fig.10 As shown, the sixth switch element SW6 can operate according to a pulse width modulation inverted level signal PWMB received from the control circuit 20, and the fifth switch element SW5 can operate according to the pulse width modulation signal PWM received from the control circuit 20. Therefore, the sixth switch element SW6 and the fifth switch element SW5 can be switched complementarily.

[0055] In summary, the present invention provides a driving circuit for adaptively switching light emitting diode current. The driving circuit for adaptively switching light emitting diode current of the present invention adopts a circuit component configuration different from that of a conventional optical driver. Compared with a conventional optical driver, the driving circuit for adaptively switching light emitting diode current of the present invention can achieve faster driving of one or more light emitting diodes (e.g., a plurality of light emitting diodes connected in series to form a light emitting diode string) of a display to emit light as desired.

[0056] The contents disclosed above are only preferred feasible embodiments of the present invention, and are not intended to limit the claims of the present invention. Therefore, all equivalent technical changes made using the description and drawings of the present invention are included in the claims of the present invention.

Claims

1. A driving circuit for adaptively switching a light emitting diode current, suitable for driving one or more light emitting diodes of a display, characterized in that: The driving circuit for adaptively switching the light emitting diode current comprises: A control circuit connected to the display and configured to output a reference current control signal according to brightness information of the display; A reference current source, wherein an input terminal of the reference current source is coupled to a shared voltage, a control terminal of the reference current source is connected to the control circuit, and the reference current source determines a current value of a reference current according to the reference current control signal and outputs the reference current; a first transistor, wherein a first terminal of the first transistor is connected to an output terminal of the reference current source and a control terminal of the first transistor, and a second terminal of the first transistor is grounded; a first switching component, wherein a first terminal of the first switching component is connected to a control terminal of the first transistor; a second transistor, wherein a control terminal of the second transistor is connected to a second terminal of the first switching component; a third transistor, a first end of the third transistor being connected to the display, a second end of the third transistor being connected to the first end of the second transistor, and a second end of the second transistor being grounded; as well as An operational amplifier, wherein a first input terminal of the operational amplifier is connected to a first terminal of the first transistor, a second input terminal of the operational amplifier is connected to a second terminal of the third transistor, and an output terminal of the operational amplifier is connected to a control terminal of the third transistor.

2. The driving circuit for adaptively switching the light emitting diode current according to claim 1, characterized in that: The drive circuit for adaptively switching the light emitting diode current further comprises: A second switching component, wherein a first end of the second switching component is connected to the second end of the first switching component and the control end of the second transistor, and a second end of the second switching component is grounded.

3. The driving circuit for adaptively switching the light emitting diode current according to claim 2, characterized in that: The drive circuit for adaptively switching the light emitting diode current further comprises: A third switching component, wherein a first terminal of the third switching component is connected to the second input terminal of the operational amplifier, and a second terminal of the third switching component is connected to a node between the second terminal of the third transistor and the first terminal of the second transistor.

4. The driving circuit for adaptively switching the light emitting diode current according to claim 3, characterized in that: The drive circuit for adaptively switching the light emitting diode current further comprises: A fourth transistor, wherein a first terminal of the fourth transistor is coupled to the shared voltage, a control terminal of the fourth transistor is connected to the output terminal of the operational amplifier, and a second terminal of the fourth transistor is grounded.

5. The driving circuit for adaptively switching the light emitting diode current according to claim 4, characterized in that: The drive circuit for adaptively switching the light emitting diode current further comprises: A fifth transistor, wherein a first end of the fifth transistor is connected to the second end of the fourth transistor, a second end of the fifth transistor is grounded, and a control end of the fifth transistor is connected to the first end of the first transistor.

6. The driving circuit for adaptively switching the light emitting diode current according to claim 5, characterized in that: The drive circuit for adaptively switching the light emitting diode current further comprises: A fourth switching component, wherein a first terminal of the fourth switching component is connected to the second input terminal of the operational amplifier, and a second terminal of the fourth switching component is connected to a node between the second terminal of the fourth transistor and the first terminal of the fifth transistor.

7. The driving circuit for adaptively switching the light emitting diode current according to claim 6, characterized in that: The drive circuit for adaptively switching the light emitting diode current further comprises: A first capacitor, wherein a first end of the first capacitor is connected to the control end of the first transistor, and a second end of the first capacitor is grounded.

8. The driving circuit for adaptively switching the light emitting diode current according to claim 7, characterized in that: The drive circuit for adaptively switching the light emitting diode current further comprises: A second capacitor, wherein a first end of the second capacitor is connected to the first end of the first switching component, and a second end of the second capacitor is grounded.

9. The driving circuit for adaptively switching the light emitting diode current according to claim 8, characterized in that: The drive circuit for adaptively switching the light emitting diode current further comprises: A fifth switching component, wherein a first end of the fifth switching component is connected to the control end of the first transistor, and a second end of the fifth switching component is connected to the first end of the first switching component and the first end of the second capacitor.

10. The driving circuit for adaptively switching the light emitting diode current according to claim 9, characterized in that: The drive circuit for adaptively switching the light emitting diode current further comprises: A sixth switching element, wherein a first end of the sixth switching element is coupled to the shared voltage, and a second end of the sixth switching element is connected to the first end of the second capacitor.

11. The driving circuit for adaptively switching the light emitting diode current according to claim 10, characterized in that: The control end of the first switching element is connected to the control circuit to receive a pulse width modulation signal from the control circuit, and the first switching element operates according to the pulse width modulation signal.

12. The driving circuit for adaptively switching the light emitting diode current according to claim 11, characterized in that: The control end of the second switch element is connected to the control circuit to receive a PWM inverted level signal from the control circuit. The second switch element operates according to the PWM inverted level signal. The second switch element switches complementarily with the first switch element.

13. The driving circuit for adaptively switching the light emitting diode current according to claim 12, characterized in that: The control end of the third switching element is connected to the control circuit to receive the pulse width modulation signal from the control circuit, and the third switching element operates according to the pulse width modulation signal.

14. The driving circuit for adaptively switching the light emitting diode current according to claim 13, characterized in that: The control end of the fourth switch element is connected to the control circuit to receive the PWM inverted level signal from the control circuit. The fourth switch element operates according to the PWM inverted level signal. The fourth switch element switches complementarily with the third switch element.

15. The driving circuit for adaptively switching the light emitting diode current according to claim 14, characterized in that: The control terminal of the fifth switching element is connected to the control circuit to receive the pulse width modulation signal from the control circuit, and the fifth switching element operates according to the pulse width modulation signal.

16. The driving circuit for adaptively switching the light emitting diode current according to claim 15, characterized in that: The control end of the sixth switch element is connected to the control circuit to receive the PWM inverted level signal from the control circuit. The sixth switch element operates according to the PWM inverted level signal. The sixth switch element switches complementarily with the fifth switch element.

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