TW201532377A - AC voltage adjustment circuit and LED brightness adjustment circuit - Google Patents

Abstract

An AC voltage adjustment circuit is disclosed according to the embodiments of the present invention for receiving an AC input voltage. The AC voltage adjustment circuit includes a bridge rectifier for receiving the AC input current to generate a bridge rectified signal; a voltage hold circuit, coupled to the bridge rectifier, for generating a current path between an output terminal of the voltage hold circuit and a reference voltage, wherein the current path is conducted intermittently. In addition, according to another embodiment of the present invention, an LED brightness adjustment circuit is further disclosed. The LED brightness adjustment circuit is arranged for controlling current flowing through an LED device powered by an AC input voltage.

Description

AC voltage adjustment circuit and LED brightness adjustment circuit

The embodiments disclosed in the present invention relate to an adjustment circuit, and more particularly to an AC voltage adjustment circuit and a Light Emitting Diode (LED) brightness adjustment circuit.

Generally, electronic products on the market (such as LEDs) can be divided into two types of designs that are driven by direct current (DC) or alternating current (AC) power. However, due to the AC voltage of each country. Not the same (for example, the United States uses 120 volts AC, while Europe uses 230 volts AC), so products that use AC power often require different designs depending on the country or region of sale, which is inconvenient.

In addition, the voltage regulation circuit of the conventional AC power supply needs to provide a discharge path by an external large capacitor or a large resistor to avoid the voltage increase and the output voltage is infinitely shifted upward. However, in the integrated circuit Large capacitance or large resistance in the design requires a large area for layout. In addition, the slight up and down drift of the output voltage of the AC power source may affect the users of certain types of electronic products. For example, the LEDs of the LEDs may cause changes in brightness and cause discomfort to the user. In summary, there is a need in the art for an AC voltage adjustment circuit to solve the above problems.

According to an exemplary embodiment of the present invention, an AC voltage adjustment circuit and a light-emitting diode brightness adjustment circuit are disclosed to solve the above problems.

According to a first embodiment of the present invention, an AC voltage adjustment circuit is provided for receiving an AC input voltage, comprising: a bridge rectifier for receiving the AC input voltage to generate a bridge rectified signal; and a voltage hold a voltage hold circuit coupled to the bridge rectifier for generating a voltage hold signal, and a switched current source for providing a current path to the output of the voltage hold circuit and a reference Between voltages, wherein the current path is intermittently conducted.

According to a second embodiment of the present invention, a light-emitting diode brightness adjusting circuit for controlling a current amount of a light-emitting diode element powered by an alternating-current input voltage is provided, which includes: The AC voltage adjusting circuit is configured to generate the voltage holding signal according to the AC input voltage; and a current control circuit coupled to the AC voltage adjusting circuit, and controlling the LED component according to the voltage holding signal The amount of current.

According to a third embodiment of the present invention, a light-emitting diode brightness adjusting circuit for controlling the amount of current of a light-emitting diode element powered by an alternating current input voltage is provided, which includes: The AC voltage adjustment circuit is configured to generate the voltage hold signal according to the AC input voltage, wherein the AC voltage adjustment circuit further includes: a comparator coupled to the voltage hold circuit for comparing the voltage hold signal and a reference value, and outputting a comparison result; and a current control circuit coupled to the AC voltage adjustment circuit, and controlling the current amount of the LED component according to the voltage hold signal and the comparison result.

The AC voltage adjusting circuit of the present invention uses a novel method to prevent the output voltage from being infinitely shifted upward, saving design cost and improving accuracy, and automatically discriminating different AC voltages. In addition, the light-emitting diode brightness adjusting circuit of the present invention can solve the problem of brightness stabilization of the light-emitting diode element powered by the alternating-current input voltage by using the above-described alternating-current voltage adjusting circuit.

100‧‧‧AC voltage adjustment circuit

102‧‧‧Bridge rectifier

104‧‧‧Divider

106‧‧‧Voltage holding circuit

108‧‧‧Switching current source

1082‧‧‧current source

1084‧‧‧Optoelectronics

1086‧‧‧Control circuit

110‧‧‧ comparator

400‧‧‧Lighting diode brightness adjustment circuit

402_1~402_N‧‧‧Lighting diode component stacking

404_1~404_N‧‧‧ Current Control Circuit

4042‧‧‧Transduction Amplifier

4044‧‧‧First Transconductance Amplifier

4046‧‧‧Second transconductance amplifier

4048‧‧‧Selector

Fig. 1 is a schematic view showing a first exemplary embodiment of an alternating current voltage adjusting circuit of the present invention.

Fig. 2 is an operation waveform diagram of the first embodiment of the control circuit in Fig. 1.

Fig. 3 is an operational waveform diagram of the second embodiment of the control circuit in Fig. 1.

Fig. 4 is a schematic view showing an exemplary embodiment of a light-emitting diode brightness adjusting circuit of the present invention.

Figure 5 is a schematic diagram of an exemplary embodiment of a current control circuit of the present invention.

Figure 6 is a schematic diagram of another exemplary embodiment of a current control circuit of the present invention.

Figure 7 is a graph showing the relationship between the rms value of the AC input voltage and the illuminating diode current when the comparison result is zero.

Figure 8 is a graph showing the relationship between the rms value of the AC input voltage and the illuminating diode current when the comparison result is 1.

Certain terms are used throughout the description and following claims to refer to particular elements. It should be understood by those of ordinary skill in the art that manufacturers may refer to the same elements by different nouns. The scope of this specification and the subsequent patent application do not use the difference of the names as the means for distinguishing the elements, but the difference in function of the elements as the criterion for distinguishing. The term "including" as used throughout the specification and subsequent claims is an open term and should be interpreted as "including but not limited to". In addition, the term "coupled" is used herein to include any direct and indirect electrical connection. Therefore, if a first device is coupled to a second device, it means that the first device can be directly electrically connected to the second device or indirectly electrically connected to the second device through other devices or connection means.

1 is a schematic diagram of a first exemplary embodiment of an AC voltage adjustment circuit 100 of the present invention. The AC voltage adjustment circuit 100 is configured to receive an AC input voltage Vin and convert it It is an output voltage Vc for use by subsequent circuits. The AC voltage adjustment circuit 100 includes a bridge rectifier 102, a voltage divider 104, a voltage hold circuit 106, and a switched current source 108. The bridge rectifier 102 includes four diodes (herein only for illustrative purposes, not the limitation of the present invention), and is used for receiving the AC input voltage Vin to generate a bridge rectified signal Vbr, and the bridge rectification signal Vbr is divided. After dividing a first resistor R1 and a second resistor R2 in the device 104, a divided output voltage Vdiv having an adjusted amplitude is output, and the divided output voltage Vdiv enters the voltage holding circuit 106. The voltage holding circuit 106 can be composed of an operational amplifier, a diode and a capacitor (herein only for illustrative purposes, not the limitation of the present invention), which is used to track and maintain the peak value of the divided output voltage Vdiv. And according to the output voltage Vc.

In the actual circuit, there is a possibility that the output voltage Vc is instantaneously shifted upward due to the line voltage spike. In order to correct this error, it is necessary to design a corresponding capacitor for the voltage holding circuit 106 in the conventional design. A large value, or an additional discharge path to a ground voltage, which requires a relatively large amount of resistance, is very costly for today's processes. According to this embodiment, the switching current source 108 can actively provide a current path between the output of the voltage holding circuit 106 and the ground voltage, and the current path is intermittently turned on, wherein the switching current source 108 includes settings. A current source 1082, a transistor 1084, and a control circuit 1086 on the current path. The current source 1082 generates a certain current I, and the transistor 1084 is used as a switch (ie, a switch) in this embodiment. Specifically, the control circuit 1086 generates a control signal cmp according to the divided output voltage Vdiv and a threshold value Vset1 and transmits it to a gate of the transistor 1084. In other words, the control circuit 1086 is controlled by the control signal cmp. Whether the current path is turned on or not, that is, the control circuit 1086 can intermittently control the current path to be turned on by using the control signal cmp. However, the above is a preferred embodiment of the present invention, and virtually any other design that achieves the same or similar functions and that conforms to the spirit of the invention is within the scope of the invention.

Fig. 2 is an operational waveform diagram of the first embodiment of the control circuit 1086 in Fig. 1. As shown in FIG. 2, each time the divided output voltage Vdiv passes through the threshold Vset1 from a voltage higher than the threshold Vset1, the control signal cmp of the control circuit 1086 changes from a low value to a high value. And maintaining a predetermined time T; that is, each time the divided output voltage Vdiv passes through the threshold Vset1 from a voltage higher than the threshold Vset1, the control circuit 1086 controls the current path to conduct the constant current I. The output voltage Vc is discharged. However, the present invention is intended to be illustrative only and not limiting of the invention. In fact, any variation that is capable of achieving the same or similar functions and that conforms to the spirit of the invention is within the scope of the invention. For example, FIG. 3 is an operation waveform diagram of the second embodiment of the control circuit 1086 in FIG. 1. In FIG. 3, each time the divided output voltage Vdiv is driven downward from a voltage higher than the threshold value Vset1. When the number of times the threshold value Vset1 reaches a certain number of times, the control signal cmp of the control circuit 1086 changes from the low value to the high value and maintains the predetermined time T. Judgingly, it can be said that the current path continuously has an average current to correct the drift phenomenon of the output voltage Vc.

In addition, the AC voltage adjusting circuit 100 further includes a comparator 110 for comparing the output voltage Vc with a reference value Vset2 and outputting a comparison result Vdet. In one embodiment, the voltage divider 104 outputs a divided output voltage Vdiv having a ratio of 100:1. For example, when the AC input voltage Vin is 130 volts AC, the voltage divider outputs a divided output voltage Vdiv of about 1.3V; when the AC input voltage Vin is 230 volts AC, the voltage divider outputs a partial voltage of about 2.3V. Output voltage Vdiv. Therefore, the reference value Vset2 can be set to 2V in this embodiment. Therefore, when the AC input voltage Vin is 130 volts AC, the comparison result Vdet=0; when the AC input voltage Vin is 230 volts AC, the comparison result Vdet=1. In this way, the electronic product designed according to the present invention does not need to separately produce different products for voltages in different regions, but can integrate them together.

4 is a schematic diagram of an exemplary embodiment of a Light Emitting Diode (LED) brightness adjustment circuit 400 of the present invention. The LED brightness adjustment circuit 400 is configured to control a current amount of each of the plurality of LED arrays 402_1~402_N powered by an AC input voltage Vin, wherein N can be any positive integer. Each of the light emitting diode element stacks 402_1~402_N includes more than one light emitting diode element. The LED brightness adjustment circuit 400 includes the AC voltage adjustment circuit 100 and a plurality of current control circuits 404_1 to 404_N, wherein the AC voltage adjustment circuit 100 converts the AC input voltage Vin into the bridge rectifier signal Vbr and the output voltage Vc, respectively. The result Vdet is compared, and the bridge rectified signal Vbr is supplied to the plurality of light emitting diode element stacks 402_1 to 402_N, and the output voltage Vc and the comparison result Vdet are supplied to the plurality of current control circuits 404_1 to 404_N. A plurality of current control circuits 404_1 ～ 404_N are respectively used to control the amount of current on the respective current paths. For details, please refer to FIG.

Figure 5 is a schematic diagram of an exemplary embodiment of a current control circuit of the present invention. The current control circuit 404_1 includes a transconductance amplifier 4042 for converting the output voltage Vc into a one-turn conduction current I _GM . The conductive current I _{GM is} used to control the amount of current on the current path to which the current control circuit 404_1 belongs, thereby controlling the amount of current of the light-emitting diode element 402_1 (ie, the light-emitting diode current I _{LED in} FIG. 4). The operation methods of the plurality of current control circuits 404_2 to 404_N are similar to those of the current control circuit 404_2, so that no further description is made here. In an embodiment, the conductive current I _{GM is} inversely proportional to the output voltage Vc. That is, the amount of current flowing through the light-emitting diode element 402_1 is inversely proportional to the root mean square value of the alternating current input voltage Vin, as shown in the lower left diagram of FIG. In another embodiment, the conductive current I _{GM is} proportional to the output voltage Vc. That is, the amount of current flowing through the light-emitting diode element 402_1 is proportional to the root mean square value of the alternating current input voltage Vin, as shown in the lower right diagram of FIG.

Figure 6 is a schematic diagram of another exemplary embodiment of a current control circuit of the present invention. The current control circuit 404_1 includes a first transconductance amplifier 4044, a second transconductance amplifier 4046, and a selector 4048. The selector 4048 can selectively select the first transduction amplifier 4044 or the second according to the comparison result Vdet. The output current of the transconductance amplifier 4046 is coupled to the corresponding LED component stack. For example, when the comparison result Vdet=0 (ie, the AC input voltage Vin is 110 volts AC), the selector 4048 will be the first. The output current of the transconductance amplifier 4044 is coupled to the corresponding LED component stack; conversely, when the comparison result Vdet=1 (ie, the AC input voltage Vin is 230 volts AC), indicating that the selector 4048 will be the second transducing The output current of amplifier 4046 is coupled to a corresponding stack of light emitting diode elements. In this embodiment, the first transconductance amplifier 4044 and the second transduction amplifier 4046 respectively convert the output voltage Vc into a first transconductance current I _GM1 and a second transconductance current I _GM2 , and are determined according to the comparison result Vdet. Extracting the first conductive current I _GM1 or the second conductive current I _GM2 to generate a light-emitting diode current I _LED to control the current amount in the current path of the current control circuit 404_1, thereby controlling the light-emitting diode element 402_1 The amount of current (ie, the LED current I _{LED in} Figure 4). The transducing values of the first transconductance amplifier 4044 and the second transduction amplifier 4046 can be set to different values to increase the flexibility of the design. As for the operation method of the current control circuits 404_2 to 404_N, the current control circuit 404_1 is similar, so no further description is made here.

Please refer to FIG. 7. FIG. 7 is a graph showing the relationship between the rms value of the AC input voltage Vin and the LED current I _LED when the comparison result Vdet=0 (ie, the AC input voltage Vin is 110 volts AC). . Please note that the relationship diagram in FIG. 7 is specifically reversed in order to compensate for the phenomenon that the brightness of the plurality of LED arrays 402_1~402_N changes due to the change of the AC input voltage Vin. In other words, the first conductive current I _{GM1 in} FIG. 7 is inversely proportional to the root mean square value of the AC input voltage Vin. In addition, Fig. 8 is a graph showing the relationship between the rms value of the AC input voltage Vin and the illuminating diode current I _LED when the comparison result Vdet = 1 (i.e., the AC input voltage Vin is 230 volts AC). Referring to FIG. 8, the second conductive current I _{GM2 is} also inversely proportional to the rms value of the AC input voltage Vin, and the transconductance of the second transconductance amplifier 4046 is half of the transconductance value of the first transconductance amplifier 4044. It should be noted that the numerical values in FIGS. 7 and 8 are for illustrative purposes only, and are not intended to limit the invention. In fact, any other variation that is capable of achieving the same or similar function variations, and which is in accordance with the inventive concept of the invention, All fall within the scope of the invention.

In summary, the AC voltage adjustment circuit of the present invention uses a novel method to avoid leakage of the output voltage infinitely upward, saving design cost and improving accuracy, and automatically distinguishing different AC voltages ( For example, 120 volts AC and 230 volts AC). In addition, the light-emitting diode brightness adjusting circuit of the present invention can solve the problem of brightness stabilization of the light-emitting diode element powered by the alternating-current input voltage by using the above-described alternating-current voltage adjusting circuit.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

100‧‧‧AC voltage adjustment circuit

102‧‧‧Bridge rectifier

104‧‧‧Divider

106‧‧‧Voltage holding circuit

108‧‧‧Switching current source

1082‧‧‧current source

1084‧‧‧Optoelectronics

1086‧‧‧Control circuit

110‧‧‧ comparator

Claims (10)

An AC voltage adjusting circuit receives an AC input voltage, comprising: a bridge rectifier for receiving the AC input voltage to generate a bridge rectified signal; and a voltage holding circuit coupled to the bridge rectifier for generating a voltage And a switching current source for providing a current path between the output of the voltage holding circuit and a reference voltage, wherein the current path is intermittently turned on. The AC voltage adjustment circuit of claim 1, further comprising a voltage divider coupled between the bridge rectifier and the voltage holding circuit. The AC voltage adjustment circuit of claim 1, wherein the switching current source comprises: a current source disposed on the current path; a switching switch disposed on the current path; and a control circuit, The switch is coupled to the switch to determine whether to turn the switch on or off according to the bridge rectified signal and a threshold, wherein the current path is turned on when the switch is turned on. The AC voltage adjustment circuit of claim 3, wherein the control circuit turns on the switch and maintains for a predetermined time only when the bridge rectification signal exceeds the threshold. The AC voltage adjustment circuit of claim 3, wherein the control circuit turns on the switch and maintains the predetermined time when the bridge rectifier signal exceeds the threshold for a certain number of times. A light-emitting diode (LED) brightness adjusting circuit for controlling a current amount of a light-emitting diode element powered by an AC input voltage, comprising: as described in claim 1 An AC voltage adjustment circuit for generating the voltage hold signal according to the AC input voltage; and a current control circuit coupled to the AC voltage adjustment circuit, and controlling the current amount of the LED component according to the voltage hold signal . The light-emitting diode brightness adjusting circuit of claim 6, wherein the current amount of the light-emitting diode element is proportional to the voltage holding signal. The light-emitting diode brightness adjusting circuit of claim 6, wherein the current amount of the light-emitting diode element is inversely proportional to the voltage holding signal. A light-emitting diode brightness adjusting circuit for controlling the current amount of a light-emitting diode element powered by an AC input voltage, comprising: an AC voltage adjusting circuit as described in claim 1 of the patent scope, The AC input voltage generates the voltage hold signal, wherein the AC voltage adjustment circuit further includes: a comparator coupled to the voltage hold circuit for comparing the voltage hold signal and a reference value, and outputting a comparison result; And a current control circuit coupled to the AC voltage adjustment circuit, and controlling the current amount of the LED component according to the voltage hold signal and the comparison result. The illuminating diode brightness adjusting circuit of claim 9, wherein the current control circuit comprises: a first transconductance amplifier for converting the voltage hold signal into a first transfer current; a second transduction amplifier for converting the voltage hold signal into a second transfer current; and a selector The light emitting diode component is coupled to the first conductive current or the second conductive current according to the comparison result to control the current amount of the light emitting diode component.