CN105657921A - Current type digital-to-analog conversion circuit and light emitting diode circuit using same - Google Patents

Abstract

A current-mode digital-to-analog conversion circuit is used for providing a diode for conducting current switching operation and comprises a current-mode digital-to-analog converter and a resistor. The current-mode digital-to-analog converter is used for outputting stable current, comprises a plurality of current units and is respectively provided with a first output end and a second output end. The first output end is electrically connected to the diode, and the second output end is electrically connected to the resistor. Each current unit has a current source and a switch circuit. The first terminal of the switch circuit is electrically coupled to the current source, the second terminal and the third terminal of the switch circuit are electrically coupled to the first output terminal and the second output terminal of the current-mode digital-to-analog converter, respectively, and the switch circuit is controlled by a switch signal to selectively conduct one of the second terminal and the third terminal with the first terminal.

Description

Current-type digital-to-analog conversion circuit and light-emitting diode circuit using it

technical field

The present invention relates to a light-emitting diode circuit, and in particular to a current-mode digital-to-analog conversion circuit for providing diodes to conduct current switching operations, and a light-emitting diode circuit using the current-mode digital-to-analog conversion circuit.

Background technique

In recent years, due to the rising awareness of environmental protection and energy saving, the rise of the light-emitting diode (Light-Emitting Diode, LED) industry has been relatively driven, and because the light source of the light-emitting diode has the advantages of environmental protection, energy saving, long service life and low driving voltage, so the current It is widely used to replace traditional lighting.

Furthermore, since the brightness of the light generated by the LED depends on the magnitude of the current flowing through the LED, when driving the LED, the main purpose is to control the current flowing through the LED to achieve the required value of the original design, and Make the current flowing through the LED stable without being affected by factors such as power supply voltage, temperature, forward bias difference, etc., so that the LED emits light with the expected brightness, and prevents the LED from being damaged or shortening its life. In addition, the light-emitting diode works on direct current, and the forward bias voltage of the light-emitting diode is exponentially related to the current, so a very small voltage change will cause a large change in the current of the light-emitting diode, which will cause a relatively large change in the brightness of the light generated by the light-emitting diode. There will be some changes, and in severe cases, the light-emitting diodes will be permanently damaged due to excessive power consumption.

On the other hand, because the traditional LED driving circuit may not be able to quickly change the current flowing through the LED, which relatively limits the speed at which the LED is turned on and off, most currently known LED circuits use one or more A current-mode digital-to-analog converter for precise current control. Under the control of these current-mode digital-to-analog converters, the light-emitting diode circuit is allowed to quickly turn on or off a plurality of current units of the current-mode digital-to-analog converter, so that the current flowing through the light-emitting diodes can be quickly adjusted. However, when the current-mode digital-analog converter disconnects at least one current unit of the current-mode digital-analog converter, the bias voltage of the current-mode digital-analog converter will be relatively changed. Only when the above-mentioned disconnected current cell is turned on again, the bias voltage will be re-established, similar to the previous bias voltage.

Please refer to FIG. 1 . FIG. 1 is a schematic circuit diagram of a conventional current-mode digital-to-analog converter used in a light-emitting diode circuit. The output end of the current-mode digital-to-analog converter 1 is electrically connected to the light-emitting diode L1, and is used to output a stable current to the light-emitting diode L1. In addition, the current-mode digital-to-analog converter 1 has a plurality of current units, and each current unit receives a switch signal TS, and controls its internal switch circuit SW1 to turn on or off according to the switch signal TS. More specifically, the number of current units is compared to the number of control bits of the switch and brightness switching signals, and each switch signal TS is one of a plurality of control bits.

Only when the switch circuit SW1 of at least one current unit is turned on, the current output by the current-mode digital-to-analog converter 1 will flow through the light-emitting diode L1, so that the light-emitting diode L1 can start to emit light, and relatively ground Build up the bias. On the contrary, when the light emitting diode L1 is to be turned off, it is necessary to control the switching circuit SW1 of all the current units to be turned off, so that the current output by the current-mode digital-to-analog converter 1 does not flow through the light emitting diode L1. But doing so will relatively change the bias voltage. In addition, when the brightness of the light-emitting diode L1 is to be adjusted, one of the current units may be controlled to be disconnected, so the bias voltage will also be affected and changed. When the disconnected current unit is turned on again, the bias voltage is re-established, which is similar to the previous bias voltage, but it takes a while to re-establish the bias voltage, which may result in inaccurate brightness for a period of time.

To put it simply, the current mode DAC in the prior art still needs to re-establish due to the switching operation of the conduction current of the light emitting diode (including the switching operation of the light emitting diode and the switching of the conduction current of the light emitting diode). The bias voltage causes the current-mode digital-to-analog converter to fail to quickly provide accurate current to the light-emitting diodes, thereby making the light-emitting diodes unable to quickly emit light with expected brightness.

Contents of the invention

An embodiment of the present invention provides a current-mode digital-to-analog conversion circuit, which is used to provide a diode to perform a conduction current switching operation. The current-mode digital-to-analog conversion circuit includes a current-mode digital-to-analog converter and a resistor. The current-mode digital-to-analog converter is used to output stable current, and has a first output terminal and a second output terminal respectively, wherein the first output terminal is electrically connected to the diode, and the second output terminal is electrically connected to the resistor. In addition, the current-mode digital-to-analog converter includes multiple current units. Each current unit has a current source and a switch circuit, wherein the first end of the switch circuit is electrically coupled to the current source, and the second end and the third end of the switch circuit are respectively electrically coupled to the current source. The first output terminal and the second output terminal of the digital-to-analog converter, and the switch circuit is controlled by a switch signal to selectively conduct one of the second terminal and the third terminal and the first terminal to each other.

The embodiment of the present invention further provides a light emitting diode circuit. The light emitting diode circuit includes a light emitting diode, and a current-mode digital-to-analog conversion circuit for providing the light emitting diode with a conduction current switching operation. The current-mode digital-to-analog conversion circuit includes a current-mode digital-to-analog converter and a resistor. The current-mode digital-to-analog converter is used to output stable current, and has a first output terminal and a second output terminal respectively, wherein the first output terminal is electrically connected to the diode, and the second output terminal is electrically connected to the resistor. In addition, the current-mode digital-to-analog converter includes multiple current units. Each current unit has a current source and a switch circuit, wherein the first end of the switch circuit is electrically coupled to the current source, and the second end and the third end of the switch circuit are respectively electrically coupled to the current The first output terminal and the second output terminal of the type digital-analog converter, and the switch circuit is controlled by the switch signal to selectively conduct one of the second terminal and the third terminal and the first terminal to each other.

In summary, the current-mode digital-to-analog conversion circuit provided by the embodiment of the present invention and the light-emitting diode circuit using the current-mode digital-to-analog conversion circuit can simulate the operation of the differential pair by adding an additional path to simulate the differential pair. The method guides the current flowing through the light-emitting diode, so that the bias voltage on the connection between the current-type digital-to-analog conversion circuit and the light-emitting diode does not need to be re-established, thereby achieving the function of switching the light-emitting diode at high speed and switching the brightness of the light-emitting diode.

In order to enable a further understanding of the features and technical content of the present invention, please refer to the following detailed descriptions and drawings of the present invention, but these descriptions and drawings are only used to illustrate the present invention, rather than to make any statement on the scope of rights of the present invention. limits.

Description of drawings

FIG. 1 is a schematic circuit diagram of a traditional current-mode digital-to-analog converter used in a light-emitting diode circuit.

FIG. 2 is a schematic circuit diagram of a current mode digital-to-analog conversion circuit provided by an embodiment of the present invention.

FIG. 3 is a schematic circuit diagram of a current mode digital-to-analog conversion circuit provided by another embodiment of the present invention.

FIG. 4 is a schematic circuit diagram of a light emitting diode circuit provided by an embodiment of the present invention.

Wherein, the reference signs are explained as follows:

1: Current-mode digital-to-analog converter

L1: LED

SW1: switch circuit

TS: switch signal

2: Current mode digital-to-analog conversion circuit

20: Current-mode digital-to-analog converter

P: first output terminal

Q: Second output terminal

I1: current source

SW2: switch circuit

M1: first transistor

M2: second transistor

R1: Resistor

L2, L3: LEDs

Din: Diode switch signal

Din_1: first control signal

Din_2: Second control signal

VDD: system voltage

4: LED circuit

detailed description

Hereinafter, the present invention will be described in detail by illustrating various embodiments of the invention with accompanying drawings. However, inventive concepts may be embodied in many different forms and should not be construed as limited to the illustrative embodiments set forth herein. Furthermore, the same reference numerals may be used to denote similar elements in the drawings.

Please refer to FIG. 2 . FIG. 2 is a schematic circuit diagram of a current mode digital-to-analog conversion circuit provided by an embodiment of the present invention. The current-mode digital-to-analog conversion circuit 2 can be used to provide diodes for conducting current switching operations (including changing the conducting current of the diodes and switching the diodes). For example, the diode may be the light emitting diode L2, but the invention is not limited thereto. The current-mode digital-to-analog conversion circuit 2 may include a current-mode digital-to-analog converter 20 and a resistor R1. The current-mode digital-to-analog converter 20 is used to output a stable current, and has a first output terminal P and a second output terminal Q, wherein the first output terminal P is electrically connected to the light-emitting diode L2, and the second output terminal Q is Electrically connected to the resistor R1.

In addition, the current-mode digital-to-analog converter 20 may include a plurality of current units. Each current unit has a current source I1 and a switch circuit SW2, wherein the first terminal of the switch circuit SW2 is electrically coupled to the current source I1, and the second terminal and the third terminal of the switch circuit SW2 are respectively electrically coupled to the current The first output terminal P and the second output terminal Q of the type digital-to-analog converter 20, and the switch circuit SW2 is controlled by the switch signal Din, so as to selectively make one of the second terminal and the third terminal and the first terminal mutually conduction. The switch signal Din is, for example, one of the control bits of the light switch and brightness switch control signal of the light emitting diode L2.

In other words, the switching signal Din controls the current output by the current unit of the current-mode digital-to-analog converter 20 to flow through the first output terminal P or the second output terminal Q. It is worth noting that the present invention does not limit the number of current units in the current-mode digital-to-analog converter 20, and the detailed implementation of each current unit. Those skilled in the art can determine the current units based on actual needs or applications. design.

Therefore, when the second terminal and the first terminal of the switch circuit SW2 of at least one current unit are connected to each other, it means that the current output by the current unit of the current-mode digital-analog converter 20 is switched to the first output terminal P. That is to say, the current unit of the current-mode digital-to-analog converter 20 is used to output current to the light-emitting diode L2, so that the light-emitting diode L2 can emit light.

Conversely, when the switch circuit SW2 of the current unit changes the third terminal and the first terminal to conduct with each other, it means that the current output by the current unit of the current-mode digital-to-analog converter 20 is switched to the second output terminal Q. That is to say, the current unit of the current-mode digital-to-analog converter 20 is used instead to output current to the resistor R1 instead of flowing through the LED L2 , so that the brightness of the LED L2 is relatively reduced. If the third terminal and the first terminal of the switch circuit SW2 of all the current units are connected to each other, the light emitting diode L2 will be turned off and not emit light.

It can be seen that, compared with the traditional current-mode digital-to-analog converter 1 in FIG. The current output by the current unit of the current-mode digital-to-analog converter 20 is guided. Therefore, if an appropriate resistor R1 is selected, the voltage of the first output terminal P when the light-emitting diode L2 is turned on (that is, when the first terminal and the second terminal of the switch circuit SW2 of all current units are turned on) will be the same as the voltage of the second output terminal P. The voltage of the terminal Q will be the same when the light emitting diode L2 is turned off (that is, when the first terminal and the third terminal of the switch circuit SW2 of all current units are turned on). Broadly speaking, before the first terminal and the third terminal of the switch circuit SW2 of one of the current units are turned on, the current source bias voltage of the current unit and the first terminal and the third terminal of the switch circuit SW2 of the current unit The bias voltage of the current source of the current unit after being turned on has little difference, and it can be seen that the bias voltage of the current source of the current unit maintains a fixed value in essence. Therefore, after the first terminal and the second terminal of the switch circuit SW2 of the current unit are turned on again, the bias voltage does not take time to re-establish, so that the light emitting diode L2 can quickly emit light with a desired brightness.

In a word, the present invention does not limit the specific implementation of the resistor R1. Therefore, the bias voltage of the current-mode digital-to-analog converter 20 in the embodiment of the present invention will not need to be re-established because the light-emitting diode L2 is turned on or off and the current provided by the current-mode digital-to-analog converter 20 changes, so the implementation of the present invention The current-mode digital-to-analog converter 20 in this example can provide accurate current relatively quickly, so that the light emitting diode L2 can quickly emit light with a desired brightness.

On the other hand, as mentioned above, one end of the light-emitting diode L2 and the resistor R1 in the embodiment of the present invention are electrically coupled to the first and second output ends P and Q of the current-mode digital-to-analog converter 20 , respectively. However, the other end of the LED L2 and the resistor R1 in the embodiment of the present invention can be electrically coupled to the system voltage VDD. In this regard, those skilled in the art should be able to design a detailed implementation of electrically coupling the system voltage VDD according to actual needs or applications, and the present invention is not limited thereto.

Next, in order to further illustrate the implementation details of the switch circuit SW2 in the current-mode digital-to-analog converter 20, the present invention further provides an implementation manner of the switch circuit SW2. Please refer to FIG. 3 . FIG. 3 is a schematic circuit diagram of a current mode digital-to-analog conversion circuit provided by another embodiment of the present invention. However, the following is only one detailed implementation of the switch circuit SW2 in the current-mode digital-to-analog converter 20 , which is not intended to limit the present invention. The switch circuit SW2 described in this embodiment can be implemented in the current mode digital-to-analog conversion circuit 2 shown in FIG. 2 , so please refer to FIG. 2 for easy understanding. In addition, some components in FIG. 3 that are similar to those in FIG. 2 are marked with similar numerals, so details thereof will not be described here.

In detail, the switch circuit SW2 may include a first transistor M1 and a second transistor M2, wherein the drain terminal of the first transistor M1 and the drain terminal of the second transistor M2 are respectively electrically coupled to the second terminal of the switch circuit SW2 with the third end. The source terminal of the first transistor M1 and the source terminal of the second transistor M2 are both electrically coupled to the first terminal of the switch circuit SW2. In addition, the gate terminal of the first transistor M1 and the gate terminal of the second transistor M2 are both used to receive the switching signal Din.

As mentioned above, because the switch circuit SW2 is controlled by the switch signal Din, only one of the second terminal and the third terminal and the first terminal can be selectively conducted to each other. In other words, when the second terminal and the first terminal of the switch circuit SW2 are connected to each other, it means that the current only flows through the first transistor M1, and when the third terminal and the first terminal of the switch circuit SW2 If they are not connected to each other, it means that the current only flows through the second transistor M2. It can be seen that, the first transistor M1 and the second transistor M2 may operate in opposite directions to each other.

In this regard, the diode switch signal Din may further include a first control signal Din_1 and a second control signal Din_2, and the second control signal Din_2 is an inverse signal of the first control signal Din_1, wherein the gate terminal of the first transistor M1 is used for The first control signal Din_1 is received, and the gate terminal of the second transistor M2 is used for receiving the second control signal Din_2. Therefore, when the first transistor M1 is controlled by the first control signal Din_1 to make the second terminal and the first terminal of the switch circuit SW2 conduct each other, the second transistor M2 is also controlled by the second control signal Din_2 to Make the third terminal and the first terminal of the switch circuit SW2 non-conductive to each other. Conversely, when the first transistor M1 is controlled by the first control signal Din_1 to make the second terminal and the first terminal of the switch circuit SW2 non-conductive, the second transistor M2 is also controlled by the second control signal Din_2 enables the third terminal and the first terminal of the switch circuit SW2 to conduct with each other. In other words, when the first transistor M1 and the second transistor M2 are respectively controlled by the first control signal Din_1 and the second control signal Din_2, the current unit of the current-mode digital-to-analog converter 20 can be selectively guided. The output current is switched between the first and second output terminals P and Q.

In summary, the current-mode digital-to-analog converter circuit 2 of the embodiment of the present invention adds an additional path, which can selectively guide the current output by the current unit of the current-mode digital-to-analog converter 20, so that the first output terminal P is at The voltage when the light-emitting diode L2 is turned on is consistent with the voltage of the second output terminal Q when the light-emitting diode L2 is turned off, or the current source bias voltage of each current unit before changing the current provided by the current-mode digital-to-analog converter 20 is consistent with the current-mode After the current provided by the digital-to-analog converter 20 is changed, the current source bias voltage of each current unit has little difference from each other, and it can be considered that the current source bias voltage of each current unit maintains a fixed magnitude in essence. Therefore, the bias voltage of the current-mode digital-analog converter 20 in the embodiment of the present invention will not need to be re-established due to the change of the switch of the light-emitting diode L2 or the current provided by the current-mode digital-analog converter 20, so that the current-mode digital-analog converter The converter 20 can quickly provide accurate current, thereby enabling the light emitting diode L2 to quickly emit light with a desired brightness, achieving the functions of switching the light emitting diode L2 at high speed and quickly adjusting the brightness of the light emitting diode L2.

As mentioned above, the current-mode digital-to-analog conversion circuit 2 can be used to provide the light emitting diode L2 to perform a conduction current switching operation. In order to further illustrate the operation of the current-mode digital-to-analog conversion circuit 2 , the present invention further provides an embodiment of its LED circuit. Please refer to FIG. 4 . FIG. 4 is a schematic circuit diagram of a light emitting diode circuit provided by an embodiment of the present invention. The light-emitting diode circuit 4 described in this embodiment may include the current-mode digital-to-analog conversion circuit 2 shown in FIG. 2 , so please refer to FIG. 2 for easy understanding. In addition, some components in FIG. 4 that are similar to those in FIG. 2 are marked with similar numerals, so details thereof will not be described here.

Please refer to FIG. 2 and FIG. 4 at the same time. The light emitting diode circuit 4 of the embodiment of the present invention may include a light emitting diode L3 and the current-mode digital-to-analog conversion circuit 2 shown in FIG. L3 performs a conduction current switching operation. Therefore, the current-mode digital-to-analog conversion circuit 2 includes a current-mode digital-to-analog converter 20 and a resistor R1. Wherein, the current-mode digital-to-analog converter 20 is used to output a stable current, and has a first output terminal P and a second output terminal Q, wherein the first output terminal P is electrically connected to the light emitting diode L3, and the second output terminal Q is electrically connected to the resistor R1.

In addition, the current-mode digital-to-analog converter 20 may include a plurality of current units. Each current unit has a current source I1 and a switch circuit SW2, wherein the first terminal of the switch circuit SW2 is electrically coupled to the current source I1, and the second terminal and the third terminal of the switch circuit SW2 are respectively electrically coupled to the current The first output terminal P and the second output terminal Q of the type digital-to-analog converter 20, and the switch circuit SW2 is controlled by the switch signal Din, so as to selectively make one of the second terminal and the third terminal and the first terminal mutually conduction.

In addition, one end of the light-emitting diode L3 and the resistor R1 in the embodiment of the present invention is electrically coupled to the first and second output ends P, Q of the current-mode digital-to-analog converter 20 . However, the other end of the LED L3 and the resistor R1 in the embodiment of the present invention can be electrically coupled to the system voltage VDD.

On the other hand, the current-mode digital-to-analog conversion circuit 2 in the light-emitting diode circuit 4 of the embodiment of the present invention may include the switch circuit SW2 shown in FIG. 3, so please refer to FIG. elaborate on its details.

Based on the above, the current-mode digital-to-analog conversion circuit provided by the embodiment of the present invention and the light-emitting diode circuit using the current-mode digital-to-analog conversion circuit can simulate the operation of the differential pair by adding an additional path to simulate the operation of the differential pair. The way to guide the current flowing through the light-emitting diode, so that the bias voltage of the current-mode digital-analog converter will not need to be re-established due to the change of the current provided by the switch of the light-emitting diode or the current-mode digital-analog conversion circuit, so that the current-mode digital The analog converter can quickly provide accurate current, and then achieve high-speed switching of the light-emitting diode and switching of the brightness of the light-emitting diode.

The above descriptions are only examples of the present invention, and are not intended to limit the patent scope of the present invention.

Claims (10)

1. a current type D/A conversion circuit, for providing a diode to carry out On current blocked operation, it is characterised in that, this current type D/A conversion circuit comprises:

One current type digital analog converter, in order to an electric current of stable output, this current type digital analog converter has one first output terminal and one the 2nd output terminal respectively, and this first output terminal is electrically connected this diode; And

One resistance, is electrically connected the 2nd output terminal of this current type digital analog converter;

Wherein this current type digital analog converter comprises:

Multiple current unit, each described multiple current unit all has a current source and a switch circuit, wherein a first end of this switch circuit is electrically coupled to this current source, and the 1 of this switch circuit the 2nd end and one the 3rd end be electrically coupled to this first output terminal and the 2nd output terminal respectively, this switch circuit is controlled by a switch signal, optionally to make one of them and the conducting each other of this first end of the 2nd end and the 3rd end.

2. current type D/A conversion circuit as claimed in claim 1, wherein this diode is a photodiode.

3. current type D/A conversion circuit as claimed in claim 1, wherein this first output terminal in those first ends of those whole switch circuits and those the 2nd ends each other conducting time voltage, with the 2nd output terminal in those first ends of those whole switch circuits and those the 3rd ends each other conducting time voltage consistent.

4. current type D/A conversion circuit as claimed in claim 1, wherein when those whole switch circuits make those the 2nd ends and those first ends each other conducting time, this current type digital analog converter in order to this electric current of stable output to this photodiode.

5. current type D/A conversion circuit as claimed in claim 1, wherein when those whole switch circuits make those the 3rd ends and those first ends each other conducting time, this current type digital analog converter in order to this electric current of stable output to this resistance.

6. current type D/A conversion circuit as claimed in claim 1, wherein one end of this resistance and one end of this diode are electrically coupled to a system voltage, and the other end of the other end of this diode and this resistance this first output terminal of electric property coupling and the 2nd output terminal respectively.

7. current type D/A conversion circuit as claimed in claim 1, wherein this switch signal comprises one first control signal and one the 2nd control signal, 2nd control signal is a reverse signal of this first control signal, this switch circuit comprises a first crystal Guan Yuyi two-transistor, one drain electrode end of this first crystal pipe and a drain electrode end of this two-transistor electric property coupling the 2nd end and the 3rd end respectively, the source-side of this first crystal pipe and this first end of source-side electric property coupling of this two-transistor, and a gate terminal of a gate terminal of this first crystal pipe and this two-transistor receives this first control signal and the 2nd control signal respectively.

8. a circuit of LED, it is characterised in that, comprising:

One photodiode; And

One current type D/A conversion circuit, for providing this photodiode to carry out On current blocked operation, this current type D/A conversion circuit comprises:

One current type digital analog converter, in order to an electric current of stable output, this current type digital analog converter has one first output terminal and one the 2nd output terminal respectively, and this first output terminal is electrically connected this photodiode; And

One resistance, is electrically connected the 2nd output terminal of this current type digital analog converter;

Wherein this current type digital analog converter comprises:

Multiple current unit, each described multiple current unit all has a current source and a switch circuit, wherein a first end of this switch circuit is electrically coupled to this current source, and the 1 of this switch circuit the 2nd end and one the 3rd end be electrically coupled to this first output terminal and the 2nd output terminal respectively, this switch circuit is controlled by a switch signal, optionally to make wherein one and the conducting each other of this first end of the 2nd end and the 3rd end.

9. circuit of LED as claimed in claim 8, the other end of wherein one end of this resistance and one end electric property coupling one system voltage of this photodiode, and the other end of this photodiode and this resistance is this first output terminal of electric property coupling and the 2nd output terminal respectively.

10. circuit of LED as claimed in claim 9, wherein this switch signal comprises one first control signal and one the 2nd control signal, 2nd control signal is a reverse signal of this first control signal, this switch circuit comprises a first crystal Guan Yuyi two-transistor, one drain electrode end of this first crystal pipe and a drain electrode end of this two-transistor electric property coupling the 2nd end and the 3rd end respectively, the source-side of this first crystal pipe and this first end of source-side electric property coupling of this two-transistor, and a gate terminal of a gate terminal of this first crystal pipe and this two-transistor receives this first control signal and the 2nd control signal respectively.