阅读说明：本技术 高速驱动发光组件的发光驱动器 (Light emitting driver for driving light emitting assembly at high speed ) 是由 陈文言 张铭泓 于 2020-05-11 设计创作，主要内容包括：本发明公开一种高速驱动发光组件的发光驱动器。第二晶体管的控制端连接第一晶体管的控制端和第一端。运算放大器的一输入端连接第一晶体管的第一端,而另一输入端连接第一开关和第二开关的第一端。第三晶体管的控制端以及第四晶体管的控制端连接运算放大器的输出端。第一开关的第二端以及第四晶体管的第二端连接第二晶体管的第一端。第二开关的第二端以及电流源连接第三晶体管的第二端。第四晶体管的第一端连接发光组件。控制电路连接电流源、第一开关与第二开关的控制端。(The invention discloses a light-emitting driver for driving a light-emitting component at a high speed. The control end of the second transistor is connected with the control end and the first end of the first transistor. The operational amplifier has one input terminal connected to the first terminal of the first transistor and the other input terminal connected to the first terminals of the first switch and the second switch. The control end of the third transistor and the control end of the fourth transistor are connected with the output end of the operational amplifier. The second end of the first switch and the second end of the fourth transistor are connected with the first end of the second transistor. The second end of the second switch and the current source are connected with the second end of the third transistor. The first end of the fourth transistor is connected with the light-emitting component. The control circuit is connected with the current source, the first switch and the control end of the second switch.)

1. A light emitting driver for driving a light emitting element at a high speed, comprising:

a first current mirror including a first transistor and a second transistor, wherein a first terminal of the first transistor is connected to a common voltage source, a control terminal of the second transistor is connected to a control terminal and a first terminal of the first transistor, and a second terminal of the first transistor and a second terminal of the second transistor are coupled to a reference potential;

an operational amplifier having a first input terminal and a second input terminal, respectively connected to the first terminal of the first transistor and the first terminal of the second transistor;

a fast switching circuit, comprising:

inputting a current source;

a third transistor, a first end of the third transistor is connected to the shared voltage source, a second end of the third transistor is connected to the input current source, and a control end of the third transistor is connected to an output end of the operational amplifier;

a first switch, a first end of which is connected to the second input end of the operational amplifier, and a second end of which is connected to a first end of the second transistor; and

a second switch, a first end of the second switch being connected to the second input terminal of the operational amplifier, a second end of the second switch being connected to a second end of the third transistor;

a first end of the fourth transistor is connected with the light-emitting component, a second end of the fourth transistor is connected with a first end of the second transistor, and a control end of the fourth transistor is connected with an output end of the operational amplifier; and

and the control circuit is connected with the control end of the first switch and the control end of the second switch and is configured to complementarily switch the first switch and the second switch.

2. The light emitting driver of claim 1, wherein the input current source is a variable current source, and the control circuit is connected to the variable current source and controls the current supplied by the variable current source in response to the operating parameters of the light emitting device.

3. The light-emitting driver of a high-speed light-emitting device as claimed in claim 1, further comprising a reference current source connected between the first terminal of the first transistor and the common voltage source and connected to the control circuit, wherein the control circuit controls the current supplied by the reference current source according to an operation parameter of the light-emitting device.

4. The light emitting driver of high-speed driving light emitting device as claimed in claim 1, further comprising a third switch, wherein a first terminal of the third switch is connected to the control terminal of the fourth transistor, a second terminal of the third switch is connected to ground, and a control terminal of the third switch is connected to the control circuit.

5. The light emitting driver of claim 1, wherein a control terminal of the third transistor is connected to an output terminal of the operational amplifier, the third transistor and the fourth transistor form a second current mirror, and a ratio of the third transistor to the fourth transistor depends on an operation parameter of the light emitting device.

6. The light emitting driver of high speed light emitting device as claimed in claim 1, further comprising a fourth switch, wherein a first terminal of the fourth switch is connected to the output terminal of the operational amplifier, a second terminal of the fourth switch is connected to the control terminal of the fourth transistor, and a control terminal of the fourth switch is connected to the control circuit.

7. A light emitting driver for driving a light emitting device at a high speed according to claim 1, wherein the first input terminal of the operational amplifier is a non-inverting input terminal, and the second input terminal is an inverting input terminal.

8. A light driver for driving light emitting components at a high speed according to claim 1, wherein the light emitting components comprise a plurality of light emitting diodes, and the plurality of light emitting diodes are connected in series with each other.

Technical Field

The present invention relates to a light emitting driver of a display device, and more particularly, to a light emitting driver for driving light emitting elements at high speed.

Background

The circuit elements of the conventional light emitting driver are controlled by the PFM01 shown in fig. 4B, so that before the light emitting device is driven to emit light, a preparation time is required for establishing a negative feedback mechanism of the operational amplifier, which causes a driving delay, resulting in an energy loss of the PFM01, thereby forming the PFM 02. As a result, energy loss of the light emitting element current ILED01 affects the light emitting luminance of the light emitting element. In order to solve this problem, a current detection current and a compensation circuit are provided in the conventional light emitting driver. After the energy loss, the compensation circuit performs a post compensation operation according to the current of the light emitting device detected by the current detection circuit to compensate the energy loss of the current ILED0 of the light emitting device.

However, when the circuit elements of the conventional light emitting driver are changed to use the PFM03 with a higher Duty cycle (High Duty) as shown in fig. 4C, the energy of the PFM03 is lost to form the PFM 04. In this case, the duty cycle of the PFM03 is too high and does not have enough time to fully compensate the energy loss of the led current ILED02, which causes the led current ILED02 to change non-linearly, resulting in an undesirable lighting state of the led.

Disclosure of Invention

The present invention provides a light emitting driver for driving a light emitting device at a high speed, which includes a first current mirror, an operational amplifier, a fast switching circuit, a fourth transistor, and a control circuit. The first current mirror includes a first transistor and a second transistor. The first end of the first transistor is connected with a shared voltage source. The control end of the second transistor is connected with the control end and the first end of the first transistor. The second terminal of the first transistor and the second terminal of the second transistor are coupled to a reference potential. The operational amplifier has a first input terminal and a second input terminal respectively connected to the first terminal of the first transistor and the first terminal of the second transistor. The fast switching circuit comprises an input current source, a third transistor, a first switch and a second switch. The first end of the third transistor is connected with a shared voltage source. The second end of the third transistor is connected with the input current source. The control end of the third transistor is connected with the output end of the operational amplifier. The first end of the first switch is connected with the second input end of the operational amplifier. The second end of the first switch is connected with the first end of the second transistor. The first end of the second switch is connected with the second input end of the operational amplifier. A second terminal of the second switch is coupled to a second terminal of the third transistor. The first end of the fourth transistor is connected with the light-emitting component. The second terminal of the fourth transistor is connected to the first terminal of the second transistor. And the control end of the fourth transistor is connected with the output end of the operational amplifier. The control circuit is connected with the control end of the first switch and the control end of the second switch and is configured to complementarily switch the first switch and the second switch.

In one embodiment, the input current source is a variable current source. The control circuit is connected with the variable current source and responds to the operation parameters of the light-emitting component to control the current supplied by the variable current source.

In one embodiment, the light emitting driver for driving the light emitting device at a high speed further includes a reference current source connected between the first terminal of the first transistor and the common voltage source and connected to the control circuit. The control circuit controls the current supplied by the reference current source according to the operation parameters of the light-emitting component.

In one embodiment, the light emitting driver for driving the light emitting assembly at high speed further comprises a third switch. A first terminal of the third switch is connected to the control terminal of the fourth transistor. The second end of the third switch is grounded. And the control end of the third switch is connected with the control circuit.

In one embodiment, the control terminal of the third transistor is connected to the output terminal of the operational amplifier. The third transistor and the fourth transistor form a second current mirror. The proportionality coefficient of the third transistor and the fourth transistor depends on the operation parameters of the light emitting component.

In one embodiment, the light emitting driver for driving the light emitting assembly at high speed further comprises a fourth switch. The first end of the fourth switch is connected with the output end of the operational amplifier. A second terminal of the fourth switch is connected to the control terminal of the fourth transistor. And the control end of the fourth switch is connected with the control circuit.

In one embodiment, the first input terminal of the operational amplifier is a non-inverting input terminal, and the second input terminal is an inverting input terminal.

In one embodiment, the light emitting device includes a plurality of light emitting diodes. The plurality of light emitting diodes are connected in series.

As described above, the present invention provides a light emitting driver for driving a light emitting device at a high speed, which maintains the voltage at the input terminal of an operational amplifier during the process of returning the operational amplifier from an open loop (open loop) to a closed loop (closed loop) by configuring a fast switching circuit, so as to prevent the current loss of the light emitting device caused by the re-establishment of an internal dc operating point as in the conventional light emitting driver. Furthermore, the input current source in the fast switching circuit of the present invention may be a variable current source, and the current supplied by the variable current source is adjusted in response to an operation parameter of the light emitting circuit (e.g., a current value of the light emitting device), so that the light emitting driver is adapted to drive the light emitting device to vary the current within a current value range.

For a better understanding of the features and technical content of the present invention, reference should be made to the following detailed description and accompanying drawings, which are provided for purposes of illustration and description only and are not intended to limit the invention.

Drawings

Fig. 1 is a circuit layout diagram of a light emitting driver for driving a light emitting device at a high speed according to a first embodiment of the present invention.

Fig. 2 is a circuit layout diagram of a light emitting driver for driving a light emitting device at a high speed according to a second embodiment of the present invention.

Fig. 3 is a signal waveform diagram of a light emitting driver for driving a light emitting device at a high speed according to an embodiment of the present invention.

Fig. 4A is a signal waveform diagram of a conventional light emitting driver for driving light emitting elements.

Fig. 4B is a signal waveform diagram of a conventional light emitting driver for driving light emitting elements.

Fig. 4C is a signal waveform diagram of a conventional light emitting driver for driving light emitting elements.

Detailed Description

The following is a description of embodiments of the present invention with reference to specific embodiments, and those skilled in the art will understand the advantages and effects of the present invention from the disclosure of the present specification. The invention is capable of other and different embodiments and its several details are capable of modifications and various changes in detail, all without departing from the spirit and scope of the present invention. The drawings of the present invention are for illustrative purposes only and are not intended to be drawn to scale. The following embodiments will further explain the related art of the present invention in detail, but the disclosure is not intended to limit the scope of the present invention. In addition, the term "or" as used herein should be taken to include any one or combination of more of the associated listed items as the case may be.

[ first embodiment ]

Fig. 1 is a circuit layout diagram of a light emitting driver for driving a light emitting device at a high speed according to a first embodiment of the present invention. As shown in fig. 1, the light emitting driver of the present embodiment may include a first current mirror MR1, an operational amplifier OPA, a fourth transistor T4, and a control circuit COT.

It should be noted that, in order to drive the light emitting device ST (such as, but not limited to, a serial circuit of a plurality of light emitting diodes) to emit light at a high speed, the light emitting driver of the present embodiment may further include a fast switching circuit. The fast switching circuit of the present embodiment may include an input current source INC, a third transistor T3, a first switch SW1, and a second switch SW 2.

The first current mirror MR1 may include a first transistor T1 and a second transistor T2. The ratio of the input current of the first current mirror MR1 (i.e., the current of the first transistor T1) to the output current of the first current mirror MR1 (i.e., the current of the second transistor T2) may be 1: k, where K is a scaling factor, may be any suitable positive integer value. The control terminal of the first transistor T1 is connected to the first terminal of the first transistor T1 and the control terminal of the second transistor T2. The second terminal of the first transistor T1 and the second terminal of the second transistor T2 are coupled to a reference potential.

The operational amplifier OPA has a first input terminal and a second input terminal. A first, e.g. non-inverting, input of the operational amplifier OPA is connected to a first terminal of the first transistor T1, i.e. to the node a 1. A second input, e.g., an inverting input, of the operational amplifier OPA is connected to a first terminal of the first switch SW1 and a first terminal of the second switch SW2, i.e., to node a 2.

A second terminal of the first switch SW1 is connected to a first terminal of the second transistor T2. A second terminal of the second switch SW2 is connected to a second terminal of the third transistor T3. In other words, the second terminal of the first switch SW1 is connected to the node NM between the second terminal of the fourth transistor T4 and the first terminal of the second transistor T2. A second terminal of the second switch SW2 is connected to a node ND between the second terminal of the third transistor T3 and the input current source INC. The output terminal of the operational amplifier OPA is connected to the control terminal of the third transistor T3 and may be connected (via the fourth switch SW4) to the control terminal of the fourth transistor T4. A first terminal of the third transistor T3 is connected to the shared voltage source VDD. A second terminal of the third transistor T3 is connected to the input current source INC.

The control circuit COT complementarily switches the first switch SW1 and the second switch SW 2.

For example, when the control circuit COT outputs the low level of the PFM, i.e. during the non-duty cycle of the PFM, the first switch SW1 is turned off. After the first switch SW1 is closed, the second switch SW2 is opened. In this case, the operational amplifier OPA is configured to obtain the voltage of the second terminal (i.e., the node ND) of the third transistor T3, to output the operational amplifier signal EAO1 to the control terminal of the third transistor T3, and to input the voltage of the second terminal of the third transistor T3 to the second input terminal of the operational amplifier OPA.

Thus, the voltage at the second input terminal of the operational amplifier OPA is kept at the voltage at the node ND, and approaches the voltage at the second input terminal of the operational amplifier OPA within the duty cycle of one pulse of the pulse frequency modulation signal PFM, so that the light-emitting device ST can be driven to emit light at high speed.

When the control circuit COT outputs the high-level PFM, i.e. enters the duty cycle of the next pulse of the PFM, the first switch SW1 is turned on, and the second switch SW2 is turned off. When the first switch SW1 is turned on, the second input terminal, e.g., the inverting input terminal, of the operational amplifier OPA is connected to the first terminal of the second transistor T2 through the first switch SW 1. In this case, the operational amplifier OPA is configured to multiply a difference between a voltage of the first terminal (i.e., the node NM) of the second transistor T2 and a voltage of the first terminal (i.e., the node a1) of the first transistor T1 by a gain value to output an operational amplification signal EAO2 to the control terminal of the fourth transistor T4 for controlling the operation of the fourth transistor T4 and thus the current ILED of the light emitting device ST.

Further, if the input current source INC is a fixed current source and the voltage at the node ND is a fixed value, the light emitting driver is adapted to maintain the current ILED driving the light emitting element ST at a fixed value. If the current ILED to drive the light emitting device ST varies within a current value range, the input current source INC of the light emitting driver needs to be a variable current source.

The control circuit COT may be connected to the input current source INC and the light emitting element ST. The control circuit COT may obtain an operation parameter BRN (e.g., a current value, a voltage value, a light emitting intensity, etc.) of the light emitting device ST, and control the current supplied by the input current source INC in response to the operation parameter BRN of the light emitting device ST to change the voltage at the second terminal (i.e., the node ND) of the third transistor T3, wherein the voltage at the node ND is expected to approach the voltage at the tracking node NM within a current value range. For example, the current ILED of the light emitting component ST is higher when the current output by the input current source INC is higher.

Further, the first terminal of the first transistor T1 may be directly connected to the common voltage source VDD, or connected to the common voltage source VDD through the reference current source IFR as shown in fig. 1. The reference current source IFR may be a variable current source. The control circuit COT is connected to the reference current source IFR and configured to output a reference control signal CR according to an operating parameter BRN of the light emitting device ST to control a current supplied by the reference current source IFR, so as to adjust a voltage input to a first input terminal, such as a non-inverting input terminal (i.e., a node a1), of the operational amplifier OPA.

In addition, the third switch SW3 and the fourth switch SW4 may be disposed between the operational amplifier OPA and the fourth transistor T4. In detail, a first terminal of the fourth switch SW4 is connected to the output terminal of the operational amplifier OPA. A second terminal of the fourth switch SW4 is connected to the control terminal of the fourth transistor T4. A first terminal of the third switch SW3 may be connected to a control terminal of the fourth transistor T4. A second terminal of the third switch SW3 is connected to ground.

A control terminal of the third switch SW3 and a control terminal of the fourth switch SW4 may be connected to the control circuit COT. When the control circuit COT outputs the pulse frequency modulation signal PFM to turn on the fourth switch SW4 and turn off the third switch SW3, the operational amplifier signal EAO2 of the operational amplifier OPA is allowed to be output to the fourth transistor T4 to control the operation of the fourth transistor T4, thereby controlling the light emitting state of the light emitting element ST. When the control circuit COT outputs the pulse frequency modulation signal PFM to turn on the third switch SW3 and turn off the fourth switch SW4, the fourth transistor T4 is grounded through the third switch SW3, so as to reset the voltage at the control terminal of the fourth transistor T4 to a zero value.

[ second embodiment ]

Fig. 2 is a circuit layout diagram of a light emitting driver of a high-speed driving light emitting device according to a second embodiment of the invention.

As shown in fig. 2, the light emitting driver of the present embodiment may include a second current mirror MR2, an integrated circuit MRC, a fast switching circuit (including an input current source INC, a third transistor T3, a first switch SW1 and a second switch SW2), an operational amplifier OPA, a control circuit COT, a reference current source IFR, a third switch SW3 and a fourth switch SW 4. The same parts as those of the first embodiment will not be described herein, and the two differences will be described in detail below.

The second current mirror MR2 includes a third transistor T3 and a fourth transistor T4. A control terminal of the third transistor T3 is connected to the output terminal of the operational amplifier OPA. The scaling factor K1 of the fourth transistor T4 may depend on the operating parameter BRN of the light emitting device ST.

For example, the control circuit COT may be connected to the fourth transistor T4 and configured to output a control signal according to the operating parameter BRN of the light emitting device ST to adjust the scaling factor K1 of the fourth transistor T4, wherein K1 may be any suitable value.

That is, the ratio of the third transistor T3 to the fourth transistor T4 may depend on the operation parameter BRN of the light emitting device ST, such as but not limited to the current ILED of the light emitting device ST. As the current ILED of the light emitting device ST is smaller, the proportionality coefficient K1 of the fourth transistor T4 is smaller, so that the gate-to-source capacitance (Cgs) and the gate-to-drain capacitance (Cgd) of the fourth transistor T4 are reduced, thereby increasing the response speed of the fourth transistor T4 and further speeding up the driving operation of the light emitting device ST by the light emitting driver of the present embodiment.

IN addition, the input terminal IN and the Gate terminal Gate of the integrated circuit MRC may be connected to the common voltage source VDD through the reference voltage source IFR. The first output terminal OUT1 of the integrated circuit MRC may be connected to the second terminal of the fourth transistor T4. The second output terminal OUT2 of the integrated circuit MRC may be connected to the second terminal of the third transistor T3. The integrated circuit MRC may comprise a current mirror formed by a plurality of transistors, and the ratio of the current mirror in the integrated circuit MRC is adjusted to 1: m: n, and further adjusting the driving operation of the light emitting device ST, wherein N and M can be any suitable values.

Referring to fig. 3 and fig. 4A together, fig. 3 is a signal waveform diagram of a light emitting driver for driving a light emitting device at a high speed according to an embodiment of the present invention; fig. 4A is a signal waveform diagram of a conventional light emitting driver for driving light emitting elements.

When the control circuit COT of the light emitting driver according to the embodiment of the present invention shown in fig. 1 and 2 outputs the high-level frequency modulation signal PFM shown in fig. 3, the first switch SW1 is turned on, and the second switch SW2 is turned off. On the contrary, when the control circuit COT outputs the low-level frequency modulation signal PFM, the first switch SW1 is turned off, and the second switch SW2 is turned on.

By the configuration of the fast switching circuit (including the input current source INC, the third transistor T3, the first switch SW1 and the second switch SW2) according to the embodiment of the invention, the current ILED driving the light emitting element is rapidly increased from 0mA to 150mA, so as to reduce the energy loss of the current ILED. In this process, the operational amplifier OPA of the light emitting driver of the embodiment of the present invention outputs the operational amplification signal EAO1 as shown in fig. 3.

In contrast, as shown in fig. 4A, when the conventional light emitting driver is used to drive the light emitting elements, the current ILED0 of the light emitting element ST takes a period of time to rise slowly, so that the energy loss of the current ILED0 is large, and the light emitting state of the light emitting element is affected. It will be appreciated that the longer the rise time required, the greater the energy loss when the light emitting assembly current ILED0 is higher.

[ advantageous effects of the embodiments ]

One of the advantages of the present invention is that the present invention provides a light emitting driver for driving a light emitting device at a high speed, which maintains the voltage at the input terminal of the operational amplifier during the process of returning the operational amplifier from an open loop (open loop) to a closed loop (closed loop) by configuring a fast switching circuit, so as to prevent the current loss of the light emitting device caused by the re-establishment of the internal dc operating point as in the conventional light emitting driver. Furthermore, the input current source in the fast switching circuit of the present invention may be a variable current source, and the current supplied by the variable current source is adjusted in response to an operation parameter of the light emitting circuit (e.g., a current value of the light emitting device), so that the light emitting driver is adapted to drive the light emitting device to vary the current within a current value range.

The disclosure above is only a preferred embodiment of the present invention and is not intended to limit the claims, so that all the modifications and equivalents of the disclosure and drawings are included in the claims.