TWI411225B - Error amplifier and led circuit comprising the same - Google Patents

Abstract

An error amplifier and a LED circuit comprising the same are provided. The LED circuit comprises an inductor, a group of LEDs and a power MOS connected to the inductor, an error amplifier and a pulse width modulator controlling the gate of the power MOS according to an error amplifier output. The error amplifier comprises a differential input stage, an output stage having a first NMOS, a first PMOS, a second NMOS, a second PMOS and a control switch module. During a first operation mode, the control switch module connects the first NMOS and PMOS and connects the second NMOS and PMOS, and during a second operation mode, control switch module disables the second NMOS and PMOS.

Description

Light-emitting diode circuit and its error amplifier

The present disclosure relates to an amplifier, and more particularly to an error amplifier and a light emitting diode circuit including the same.

Compared to traditional light bulb lighting tools, light emitting diodes (LEDs) are estimated to be four times more efficient than conventional light bulbs. Moreover, the light-emitting diode does not have a conventional light bulb containing toxic mercury, and has a longer service life than the light bulb. Under various factors, the light-emitting diode has become the latest mainstream technology of modern lighting technology.

In order to stabilize the voltage of the LED circuit, the setting of the inductor is often used to achieve the purpose. When the LED circuit starts to operate, a fast reaction time is required to quickly enter the operating mode, and a fast reaction time will cause the LED circuit to generate a relatively large current in a short time. However, the surge current generated by the light-emitting diode circuit having a fast response time is liable to cause the above-mentioned inductance to be unbearable and cause damage. Therefore, if the LED circuit does not have a mechanism for elastic adjustment of the reaction time, the inductor will continue to be subjected to the surge current in the operation mode, and is easily damaged, and the voltage regulation effect cannot be normally provided.

Therefore, how to design a new LED circuit and its error amplifier to provide flexible adjustment of the reaction time is an urgent problem to be solved in the industry.

Accordingly, one aspect of the present disclosure is to provide an error amplifier comprising: a differential input stage, an output stage, and a control switch module. The differential input stage contains a differential output. The output stage includes: a first N-type MOS transistor (NMOS), a first P-type MOS transistor (PMOS), a second N-type MOS transistor, and a second P-type MOS transistor. The first N-type MOS transistor includes a drain and a gate, wherein the drain is connected to the error amplifier output and the gate is connected to the differential output. The first P-type MOS transistor includes a gate and a drain, wherein the gate is connected to the gate controller and the drain is connected to the drain of the first N-type MOS transistor. The second P-type MOS transistor includes a drain, wherein the drain is connected to the drain of the second N-type MOS transistor. In the first mode of operation, the control switch module connects the gate of the second P-type MOS transistor to the gate controller, and connects the gate of the second N-type MOS transistor to the differential output And connecting the drain of the second P-type MOS transistor to the error amplifier output. In the second mode of operation, the control switch module is such that the second P-type MOS transistor and the second N-type MOS transistor are not connected to the gate controller, the differential output, and the error amplifier output.

According to an embodiment of the present disclosure, in the first operation mode, the control switch module increases the transduction value of the output stage. In the second mode of operation, the control switch module reduces the transduction value of the output stage.

According to another embodiment of the present disclosure, the control switch module includes: a first switch, a second switch, and a third switch. The first switch is connected between the drain of the second P-type MOS transistor and the output of the error amplifier. The second switch is connected between the gate of the second P-type MOS transistor and the gate controller. The third switch is connected between the gate of the second N-type MOS transistor and the differential output terminal.

According to still another embodiment of the present disclosure, the differential input stage further includes a first input end for receiving a reference voltage, and a second input end for receiving a variable voltage, wherein the differential output is The terminal generates a differential output voltage according to the reference voltage and the varying voltage.

According to still another embodiment of the present disclosure, the gate controller is a current source.

Another aspect of the present disclosure is to provide a light emitting diode (LED) circuit including: an inductor, a light emitting diode group, a power MOS transistor, an error amplifier, and a wave width modulation Device. The inductor is used to connect the supply voltage with the first end. A group of light emitting diodes is coupled to the first end. A power MOS transistor is coupled to the first end. The error amplifier includes: a differential input stage, an output stage, and a control switch module. The differential input stage contains a differential output. The output stage comprises: a first N-type MOS transistor, a first P-type MOS transistor, a second N-type MOS transistor, and a second P-type MOS transistor. The first N-type MOS transistor includes a drain and a gate, wherein the drain is connected to the error amplifier output and the gate is connected to the differential output. The first P-type MOS transistor includes a gate and a drain, wherein the gate is connected to the gate controller and the drain is connected to the drain of the first N-type MOS transistor. The second P-type MOS transistor includes a drain, wherein the drain is connected to the drain of the second N-type MOS transistor. In the first mode of operation, the control switch module connects the gate of the second P-type MOS transistor to the gate controller, and connects the gate of the second N-type MOS transistor to the differential output And connecting the drain of the second P-type MOS transistor to the error amplifier output. In the second mode of operation, the control switch module is such that the second P-type MOS transistor and the second N-type MOS transistor are not connected to the gate controller, the differential output, and the error amplifier output. The wave width modulator is configured to generate a switching signal according to the output of the error amplifier to control the power MOS transistor, and to charge or discharge the LED group.

According to an embodiment of the present disclosure, in the first operation mode, the control switch module increases the transduction value of the output stage. In the second mode of operation, the control switch module reduces the transduction value of the output stage.

According to another embodiment of the present disclosure, the control switch module includes: a first switch, a second switch, and a third switch. The first switch is connected between the drain of the second P-type MOS transistor and the output of the error amplifier. The second switch is connected between the gate of the second P-type MOS transistor and the gate controller. The third switch is connected between the gate of the second N-type MOS transistor and the differential output terminal.

According to still another embodiment of the present disclosure, the differential input stage further includes a first input end for receiving a reference voltage, and a second input end for receiving a variable voltage, wherein the differential output is The terminal generates a differential output voltage according to the reference voltage and the varying voltage. The varying voltage is the feedback voltage output from the group of light emitting diodes.

According to still another embodiment of the present disclosure, when the LED circuit starts to operate, the control switch module operates in the first operation mode to increase the transduction value of the output stage, when the LED circuit starts to operate, When the difference between the reference voltage and the varying voltage is less than the threshold, the control switch module operates in the second mode of operation to reduce the transduction value of the output stage.

According to another embodiment of the present disclosure, in the operation of the LED circuit, when the difference between the reference voltage and the variation voltage is greater than a threshold, the control switch module operates in the first operation mode to enhance the output stage. The transduction value, when the difference between the reference voltage and the fluctuating voltage is less than the critical value, the control switch module operates in the second operation mode to reduce the transduction value of the output stage.

According to another embodiment of the present disclosure, when the LED circuit starts to operate, the control switch module operates in the first operation mode to increase the transduction value of the output stage, when the LED circuit starts to operate. After a certain period of time, the control switch module operates in the second mode of operation to reduce the transduction value of the output stage.

According to an embodiment of the present disclosure, wherein the bandwidth modulator receives the oscillating voltage from the oscillator, the bandwidth modulator substantially generates the switching signal according to the output of the error amplifier and the oscillating voltage. The oscillating voltage is a sawtooth waveform voltage. The gate controller is a current source.

The advantage of applying the disclosure is that the above-mentioned purpose can be easily achieved by controlling the switch module, and changing the configuration of the error amplifier between different modes as needed, thereby changing the transduction value.

Please refer to Figure 1. FIG. 1 is a schematic diagram of a light-emitting diode circuit 1 in an embodiment of the present disclosure. The LED circuit 1 includes an inductor 10, a light emitting diode group 12, a power MOS transistor 14, an error amplifier 16, and a wave width modulator 18.

The inductor 10 is used to connect the supply voltage Vp with the first terminal 11 and provide a voltage stabilizing mechanism. The light emitting diode group 12 is connected between the first end 11 and the ground potential. In the present embodiment, the load 120 is substantially connected between the LED group 12 and the ground potential. The power MOS transistor 14 is connected between the first terminal 11 and the ground potential.

The error amplifier 16 is configured to receive the reference voltage Vref and the feedback voltage Vf. In the present embodiment, the feedback voltage Vf is an output from the LED group 12 as shown in FIG. In other embodiments, the feedback voltage Vf may be derived from other voltages associated with the LED group 12. The feedback voltage Vf is a varying voltage, and the value of the variation is related to the operation of the LED circuit 1. Error amplifier 16 produces an error amplifier output voltage Ve at the error amplifier output. The bandwidth modulator 18 receives the error amplifier output voltage Ve from the error amplifier output.

In the embodiment, the LED circuit 1 further includes an oscillator 180. The oscillator 180 generates an oscillating voltage Vo of a sawtooth waveform. The bandwidth modulator 18 simultaneously receives the error amplifier output voltage Ve and the oscillating voltage Vo, and accordingly generates a switching signal having an active period and an inactive period. The switching signal is further transmitted to the gate of the power MOS transistor 14 to control the switching of the power MOS transistor 14, further charging or discharging the LED group 12.

In one embodiment, the oscillating voltage Vo maintains the same waveform. Therefore, the magnitude of the error amplifier output voltage Ve will determine the active period of the switching signal and the length of the off period. When the switching signal causes the power MOS transistor 14 to initiate charging, the LED group 12 will turn on and illuminate. Conversely, when the switching signal causes the power MOS transistor 14 to initiate a discharge mechanism, the LED group 12 will be turned off. Therefore, the error amplifier output voltage Ve will determine the behavior of charging and discharging and determine the amount of current at the first terminal 11.

When the light-emitting diode circuit 1 starts to operate, a fast reaction time is required to allow the light-emitting diode circuit 1 to quickly enter the operating mode. By increasing the rate of change of the error amplifier output voltage Ve, a fast reaction time can be achieved. The fast reaction time will cause the LED circuit 1 to generate a relatively large current in a short time. However, the surge current generated by the light-emitting diode circuit 1 having a fast response time is liable to cause the inductance 10 to be unbearable and cause damage. Therefore, if the error amplifier 16 of the light-emitting diode circuit 1 does not have a mechanism for elastic adjustment of the reaction time, and the error amplifier output voltage Ve continues to maintain a high rate of change in the rise and fall, the inductor 10 will continue to suffer in the operating mode. The surge current is easily damaged and cannot provide normal voltage regulation.

Please refer to Figure 2. Figure 2 is a more detailed schematic diagram of the error amplifier 16 in one embodiment of the present disclosure. The error amplifier 16 includes a differential input stage 20, an output stage 22, and a control switch module.

The differential input stage 20 includes a first input, a second input, and a differential output. The first input terminal is for receiving the reference voltage Vref, and the second input terminal is for receiving the feedback voltage Vf. The differential output terminal generates a differential output voltage Vdi according to the reference voltage Vref and the varying voltage Vf. In this embodiment, the reference voltage Vref is a fixed value, and the feedback voltage Vf is a variable value, and the value of the variation is determined according to the operating state of the LED group 12 in FIG. .

The output stage 22 includes a first N-type MOS transistor 220, a first P-type MOS transistor 222, a second N-type MOS transistor 224, and a second P-type MOS transistor 226. The first N-type MOS transistor 220 includes a drain and a gate, wherein the drain is connected to an error amplifier output that produces an error amplifier output voltage Ve, and the gate is connected to a differential output that produces a differential output voltage Vdi. . In the present embodiment, the source of the first N-type MOS transistor 220 is connected to the ground potential. The first P-type MOS transistor 222 includes a gate and a drain, wherein the gate is coupled to the gate controller 24 and the drain is coupled to the drain of the first N-type MOS transistor 220. The gate controller 24 is a current source in this embodiment, and may be a control voltage for controlling the first P-type MOS transistor 222 in other embodiments. In this embodiment, the source of the first P-type MOS transistor 222 is connected to the supply voltage Vp. The drain of the second P-type MOS transistor 226 is connected to the drain of the second N-type MOS transistor 224. In the present embodiment, the source of the second P-type MOS transistor 226 is connected to the supply voltage Vp, and the source of the second N-type MOS transistor 224 is connected to the ground potential.

In this embodiment, the control switch module includes: a first switch 260, a second switch 262, and a third switch 264. The first switch 260 is coupled between the drain of the second P-type MOS transistor 226 and the output of the error amplifier. The second switch 262 is connected between the gate of the second P-type MOS transistor 226 and the gate controller 24. The third switch 264 is connected between the gate of the second N-type MOS transistor 224 and the differential output terminal.

In this embodiment, a control voltage (not shown) having a first state and a second state is used to control the operations of the first switch 260, the second switch 262, and the third switch 264. Please refer to both Figure 3A and Figure 3B. 3A and 3B are schematic diagrams of the error amplifier 16 in different modes of operation in an embodiment of the present disclosure.

In the first mode of operation, the control voltage is in the first state, so that the first switch 260, the second switch 262, and the third switch 264 are turned off, and the gate of the second P-type MOS transistor 226 is further transmitted. The second switch 262 is connected to the gate controller 24 such that the gate of the second N-type MOS transistor 224 is connected to the differential output terminal through the third switch 264, and the second P-type MOS transistor 226 The drain is connected to the error amplifier output through a first switch 260. FIG. 3A is an equivalent circuit diagram of the error amplifier 16 in the first mode of operation. As can be seen from FIG. 3A, in the first mode of operation, the first P-type MOS transistor 222 and the second P-type MOS transistor 226 are connected in parallel, and the first N-type MOS transistor 220 and the second N-type gold oxide semi-transistors 224 are connected in parallel.

In the second mode of operation, the control voltage is in the second state to cause the first switch 260, the second switch 262, and the third switch 264 to be in an open state, further to cause the second P-type MOS transistor 226 and the second N The MOS transistor 224 is not coupled to the gate controller 24, the differential output, and the error amplifier output. FIG. 3B is an equivalent circuit diagram of the error amplifier 16 in the second mode of operation. As can be seen from Fig. 3B, in the second mode of operation, only the first P-type MOS transistor 222 and the first N-type MOS transistor 220 are still operating.

Therefore, after switching from the second mode of operation to the first mode of operation, the transducing value of the output stage 22 of the error amplifier 16 will be boosted, and the reaction time can be made fast, that is, the error amplifier output voltage Ve can be rapidly changed. Conversely, after switching from the first mode of operation to the second mode of operation, the transducing value of the output stage 22 of the error amplifier 16 will decrease and the reaction time will also slow down.

In an embodiment, when the LED circuit 1 starts to operate, the control switch module operates in the first operation mode to increase the transconductance value of the output stage 22, and the error amplifier 16 has a fast response time. Further, the output voltage or current of the light-emitting diode circuit 1 can be rapidly increased, and the initial state of the circuit can be quickly switched to the operating mode. After the LED circuit 1 starts to operate for more than a certain time, the error amplifier 16 has been stably operated in the operation mode, and the control switch module will operate in the second operation mode to reduce the transduction value of the output stage 22, The voltage or current of the first terminal 11 no longer has a rapid rise and fall affecting the operation of the inductor 10.

In another embodiment, when the LED circuit 1 begins to operate, the control switch module operates in the first mode of operation to boost the transduction value of the output stage 22 as previously described. Then, a detection mechanism for the reference voltage Vref and the feedback voltage Vf is activated to determine that the LED circuit 1 has been stably operated when the difference between the reference voltage Vref and the feedback voltage Vf is less than a threshold value. In the working mode. Therefore, the control switch module will operate in the second mode of operation to reduce the transduction value of the output stage 22.

In still another embodiment of the present disclosure, in the operation of the LED circuit 1, the above detection mechanism can be continuously performed. When the difference between the reference voltage Vref and the feedback voltage Vf is larger than the critical value, it indicates that the light-emitting diode circuit 1 is in an unstable state. For example, if the feedback voltage Vf is too large or too small for a normal operating state, the control switch module will operate in the first mode of operation to increase the transduction value of the output stage 22 and rapidly decrease Or boost the voltage or current of the first terminal 11. When the difference between the reference voltage and the varying voltage is less than the critical value, it is judged that the light-emitting diode circuit 1 has been stably operated in the operating mode. Therefore, the control switch module operates in the second mode of operation to reduce the transduction value of the output stage 22.

It should be noted that the rise or fall of the output voltage of the error amplifier 16 is determined by the magnitude of the reference voltage Vref and the feedback voltage Vf. For example, in one embodiment, when the feedback voltage Vf is greater than the reference voltage Vref, the error amplifier 16 lowers the output voltage, and when the feedback voltage Vf is less than the reference voltage Vref, the error amplifier 16 raises the output voltage. On the other hand, the voltage current rise and fall rate of the LED circuit can also be determined by the magnitude of the reference voltage Vref and the feedback voltage Vf, that is, by changing the transconductance value of the output stage 22.

Therefore, the light-emitting diode circuit and the error amplifier included therein provide a mechanism for elastically adjusting the reaction time. By changing the transconductance value of the output stage in the error amplifier, the rise and fall rates of the output voltage of the error amplifier can be switched to appropriate values depending on the situation. Therefore, the current or voltage supplied to the group of light-emitting diodes can also be adjusted accordingly. Inductive inductors in the LED circuit can also be protected from damage.

The present disclosure has been disclosed in the above embodiments, but it is not intended to limit the disclosure, and any person skilled in the art can make various changes and refinements without departing from the spirit and scope of the disclosure. The scope of protection of the disclosure is subject to the definition of the scope of the patent application.

1. . . Light-emitting diode circuit

10. . . inductance

11. . . First end

12. . . Illuminating diode group

120. . . load

14. . . Power MOS semi-transistor

16. . . Error amplifier

18. . . Wave width modulator

180. . . Oscillator

20. . . Differential input stage

twenty two. . . Output stage

220. . . First N-type gold oxide semi-transistor

222. . . First P-type gold oxide semi-transistor

224. . . Second N-type gold oxide semi-transistor

226. . . Second P-type gold oxide semi-transistor

twenty four. . . Gate controller

260. . . First switch

262. . . Second switch

264. . . Third switch

The above and other objects, features, advantages and embodiments of the present disclosure will become more apparent and understood.

1 is a schematic diagram of a light emitting diode circuit in an embodiment of the present disclosure;

2 is a more detailed schematic diagram of an error amplifier in an embodiment of the present disclosure;

3A and 3B are schematic diagrams of an error amplifier in different modes of operation in an embodiment of the present disclosure.

16. . . Error amplifier

20. . . Differential input stage

twenty two. . . Output stage

220. . . First N-type gold oxide semi-transistor

222. . . First P-type gold oxide semi-transistor

224. . . Second N-type gold oxide semi-transistor

226. . . Second P-type gold oxide semi-transistor

twenty four. . . Gate controller

260. . . First switch

262. . . Second switch

264. . . Third switch

Claims (18)

An error amplifier includes: a differential input stage including a differential output; and an output stage comprising: a first N-type MOS transistor, comprising a drain and a gate a pole connected to an error amplifier output and the gate connected to the differential output; a first P-type MOS transistor comprising a gate and a drain, wherein The gate is connected to a gate controller, the drain is connected to the drain of the first N-type MOS transistor; a second N-type MOS transistor; and a second P-type MOS a crystal comprising a drain, wherein the drain is connected to the drain of the second N-type MOS transistor; and a control switch module; wherein in a first mode of operation, the control switch module causes the The gate of the second P-type MOS transistor is connected to the gate controller such that the gate of the second N-type MOS transistor is connected to the differential output terminal and the second P-type is The drain of the MOS transistor is coupled to the output of the error amplifier; in a second mode of operation, the control is turned on The second module P-type metal-oxide-semiconductor transistor and the second N-type metal-oxide-semiconductor transistor, does not, of the differential output terminal and the output terminal of the error amplifier is connected to the gate controller. The error amplifier of claim 1, wherein the first operation In the mode, the control switch module connects the gate of the second P-type MOS transistor to the gate controller, and connects the gate of the second N-type MOS transistor to the differential The output terminal and the drain of the second P-type MOS transistor are connected to the error amplifier output, and the transconductance of the output stage is boosted. The error amplifier of claim 1, wherein in the second mode of operation, the control switch module causes the second P-type MOS transistor and the second N-type MOS transistor to The gate controller, the differential output, and the error amplifier output are connected to reduce the transduction value of the output stage. The error amplifier of claim 1, wherein the control switch module comprises: a first switch connected between the drain of the second P-type MOS transistor and the output of the error amplifier; a switch connected between the gate of the second P-type MOS transistor and the gate controller; and a third switch connected to the gate of the second N-type MOS transistor and the difference Between the output terminals. The error amplifier of claim 1, wherein the differential input stage further comprises a first input end and a second input end, the first input end is for receiving a reference voltage, and the second input end is for receiving a varying voltage, wherein the differential output is based on the reference voltage and the varying voltage A differential output voltage is generated. The error amplifier of claim 1, wherein the gate controller is a current source. A light emitting diode (LED) circuit includes: an inductor for connecting a supply voltage and a first end; a group of light emitting diodes connected to the first end; a power metal oxygen a semi-transistor connected to the first end; an error amplifier comprising: a differential input stage comprising a differential output; and an output stage comprising: a first N-type MOS transistor comprising a 汲And a gate, wherein the drain is connected to an error amplifier output terminal and the gate is connected to the differential output terminal; a first P-type MOS transistor includes a gate and a drain, wherein The gate is connected to a gate controller, the drain is connected to the drain of the first N-type MOS transistor; a second N-type MOS transistor; and a second P-type MOS transistor a crystal comprising a drain, wherein the drain is connected to the drain of the second N-type MOS transistor; and a control switch module, wherein in a first mode of operation, the Controlling the switch module to connect the gate of the second P-type MOS transistor to the gate controller, connecting the gate of the second N-type MOS transistor to the differential output terminal and a drain of the second P-type MOS transistor is coupled to the error amplifier output; in a second mode of operation, the control switch module causes the second P-type MOS transistor and the second N-type a gold-oxygen semiconductor, not connected to the gate controller, the differential output, and the error amplifier output; and a pulse width modulator (PWM) for outputting the error amplifier A switching signal is generated to control the power MOS transistor, and the LED group is charged or discharged. The illuminating diode circuit of claim 7, wherein in the first mode of operation, the control switch module connects the gate of the second P-type MOS transistor to the gate controller, a gate of the second N-type MOS transistor is connected to the differential output terminal, and a drain of the second P-type MOS transistor is connected to the output of the error amplifier, and the turn of the output stage is raised Guide value. The illuminating diode circuit of claim 7, wherein in the second mode of operation, the control switch module causes the second P-type MOS transistor and the second N-type MOS transistor, Not connected to the gate controller, the differential output, and the error amplifier output, and the transduction value of the output stage is reduced. The light emitting diode circuit of claim 7, wherein the control The switch module includes: a first switch connected between the drain of the second P-type MOS transistor and the output terminal of the error amplifier; and a second switch connected to the second P-type MOS a gate of the crystal and the gate controller; and a third switch connected between the gate of the second N-type MOS transistor and the differential output. The illuminating diode circuit of claim 7, wherein the differential input stage further comprises a first input end and a second input end, wherein the first input end is configured to receive a reference voltage, the second input end And receiving a variable voltage, wherein the differential output generates a differential output voltage according to the reference voltage and the variable voltage. The illuminating diode circuit of claim 11, wherein the varying voltage is a feedback voltage outputted from the group of illuminating diodes. The illuminating diode circuit of claim 11, wherein when the illuminating diode circuit starts to operate, the control switch module operates in the first operating mode to increase the transducing value of the output stage. After the LED circuit starts to operate, when the difference between the reference voltage and the variation voltage is less than a threshold, the control switch module operates in the second operation mode to reduce the transduction value of the output stage. . The illuminating diode circuit of claim 11, wherein the illuminating diode circuit In the operation of the optical diode circuit, when a difference between the reference voltage and the varying voltage is greater than a threshold, the control switch module operates in the first operating mode to increase the transduction value of the output stage. When the difference between the reference voltage and the varying voltage is less than the threshold, the control switch module operates in the second mode of operation to reduce the transduction value of the output stage. The illuminating diode circuit of claim 11, wherein when the illuminating diode circuit starts to operate, the control switch module operates in the first operating mode to increase the transducing value of the output stage. After the LED circuit starts to operate for a certain period of time, the control switch module operates in the second mode of operation to reduce the transduction value of the output stage. The illuminating diode circuit of claim 7, wherein the undulating modulator receives an oscillating voltage from an oscillator, the undulating modulator is substantially generated according to the output of the error amplifier and the oscillating voltage The switch signal. The illuminating diode circuit of claim 16, wherein the oscillating voltage is a sawtooth waveform voltage. The illuminating diode circuit of claim 16, wherein the gate controller is a current source.