CN108809097B - Synchronous rectifier applied to power converter and method of operation thereof - Google Patents

Abstract

The present invention discloses a synchronous rectifier applied to a power converter and an operation method thereof. The operation method includes that when the secondary side of the power converter is turned on, the control signal generating circuit in the synchronous rectifier generates a control signal corresponding to the previous cycle according to the detection voltage of the previous cycle corresponding to the secondary side, a first reference voltage and a second reference voltage; the pre-attenuation circuit in the synchronous rectifier pre-attenuates the gate control signal of the current cycle corresponding to the secondary side and generates a pre-attenuation signal corresponding to the current cycle according to the discharge time of the previous cycle corresponding to the secondary side. Therefore, when the load coupled to the secondary side is lightly loaded, the synchronous rectifier will not pre-attenuate the gate control signal corresponding to the current cycle in advance, and when the load is very heavily loaded, the gate control signal corresponding to the current cycle will not be directly turned off.

Description

Synchronous rectifier applied to power converter and method of operation thereof

technical field

The present invention relates to a synchronous rectifier applied to a power converter and an operation method thereof, in particular to a method that can pre-attenuate the corresponding power converter according to the discharge time corresponding to the previous cycle of the secondary side of the power converter A synchronous rectifier with a gate control signal of the current period of the secondary side and an operation method thereof.

Background technique

As shown in FIG. 1 , in the continuous conduction mode (CCM) of the power converter 100 , the synchronous rectifier 200 applied to the secondary side SEC of the power converter 100 is when the secondary side of the power converter 100 is When the SEC is turned on, a gate control signal GCS for controlling the synchronous switch 102 is generated according to a detection voltage VDET of the secondary side SEC of the power converter 100 (that is, the source voltage of the synchronous switch 102 ). In the continuous conduction mode, the prior art uses the synchronous rectifier 200 to quickly turn off the gate control signal GCS according to the detection voltage VDET to avoid the simultaneous opening of the primary side PRI of the power converter 100 and the secondary side SEC of the power converter 100 .

As shown in FIG. 2 , when the secondary side SEC of the power converter 100 is turned on, the detection voltage VDET gradually increases from the minimum value VMIM (about -0.7V). Therefore, at a time T1, when the detection voltage VDET increases to a first reference voltage VREF1 (about -50mV), the synchronous rectifier 200 will pre-attenuate the gate control signal GCS, and then at a time T2, when the detection voltage VDET is When increasing to a second reference voltage VREF2 (about -10mV), the synchronous rectifier 200 will completely turn off the gate control signal GCS.

However, when the load 104 coupled to the secondary side SEC of the power converter 100 is very heavily loaded, the synchronous rectifier 200 will not pre-attenuate the gate control signal because the detection voltage VDET may not increase to the first reference voltage VREF1 GCS, so that the synchronous rectifier 200 must directly turn off the gate control signal GCS. In addition, when the load 104 coupled to the secondary side SEC of the power converter 100 is lightly loaded, because the detection voltage VDET may increase to the first reference voltage VREF1 quickly, the synchronous switch 102 operates in the triode region most of the time (triode region), resulting in poor efficiency of the power converter 100 .

Therefore, how to improve the above-mentioned prior art has become an important issue for designers of the synchronous rectifier 200 .

SUMMARY OF THE INVENTION

An embodiment of the present invention discloses a synchronous rectifier applied to a power converter. The synchronous rectifier includes a control signal generating circuit, a pre-attenuation circuit and a gate driving circuit. The control signal generating circuit is used to generate a first reference voltage and a second reference voltage according to a detection voltage corresponding to the previous cycle of the secondary side, a first reference voltage and a second reference voltage when the secondary side of the power converter is turned on. The control signal corresponding to the previous cycle, wherein the control signal corresponding to the previous cycle is the discharge time corresponding to the previous cycle. The pre-attenuation circuit is coupled to the control signal generating circuit, and is configured to pre-attenuate the gate control signal corresponding to the current cycle of the secondary side and generate a gate control signal corresponding to the current cycle according to the discharge time corresponding to the previous cycle. Periodic pre-attenuated signal. The gate driving circuit is coupled to the control signal generating circuit and the pre-attenuating circuit, and is used for driving the gate control signal corresponding to the current period according to the control signal corresponding to the current period, and according to the control signal corresponding to the current period. The pre-attenuation signal of the current period is described below, and the gate control signal corresponding to the current period is stopped from driving.

Another embodiment of the present invention discloses an operation method of a synchronous rectifier applied to a power converter, wherein the synchronous rectifier includes a control signal generating circuit, a pre-attenuation circuit and a gate driving circuit. The operating method includes that when the secondary side of the power converter is turned on, the control signal generating circuit is based on a detection voltage corresponding to a previous cycle of the secondary side, a first reference voltage and a second reference voltage , to generate a control signal corresponding to the previous cycle, wherein the control signal corresponding to the previous cycle is the discharge time corresponding to the previous cycle of the secondary side; the pre-attenuation circuit Discharge time, pre-attenuate the gate control signal corresponding to the current period of the secondary side, and generate a pre-attenuation signal corresponding to the current period.

The invention discloses a synchronous rectifier applied to a power converter and an operation method thereof. The synchronous rectifier and the operating method utilize the control signal generating circuit of the synchronous rectifier when the secondary side of the power converter is turned on, according to the detected voltage corresponding to the previous cycle of the secondary side, a first a reference voltage and a second reference voltage, generate a control signal corresponding to the previous cycle, and use the pre-attenuation circuit of the synchronous rectifier according to the discharge time corresponding to the previous cycle (corresponding to the control signal of the previous cycle signal), pre-attenuate the gate control signal corresponding to the current cycle of the secondary side. Because the synchronous rectifier and the operating method pre-attenuate the gate control signal corresponding to the current cycle according to the discharge time corresponding to the previous cycle, when the power converter is coupled to the secondary side of the power converter When the load is light, the synchronous rectifier does not pre-damp the gate control signal corresponding to the current period in advance to avoid the synchronous switch operating in the triode region most of the time, and when the load is very heavy, The synchronous rectifier does not need to directly turn off the gate control signal corresponding to the current period.

Description of drawings

FIG. 1 is a schematic diagram illustrating a synchronous rectifier applied to the secondary side of a power converter.

FIG. 2 is a timing diagram illustrating detection voltages and gate control signals.

3 is a schematic diagram of a synchronous rectifier applied to the secondary side of a power converter disclosed in the first embodiment of the present invention.

FIG. 4 is a timing diagram illustrating a detection voltage, a control signal, a gate control signal, and a pre-attenuation pulse.

FIG. 5 is a flowchart of an operation method of a synchronous rectifier applied to a power converter disclosed in a second embodiment of the present invention.

Among them, the reference numerals are described as follows:

100 Power Converters

101 Primary winding

102 Sync switch

103 Power switch

104 loads

200, 300 Synchronous Rectifier

302 control signal generation circuit

304 Pre-attenuation circuit

306 gate drive circuit

308, 310 pins

3042 Pre-Attenuation Signal Generator

3044 Pulse Generator

3046 pull-down circuit

30462 The first N-type metal-oxide-semiconductor transistor

30464 Second N-type metal oxide semiconductor transistor

30466 Switch

CS control signal

CT current pre-attenuation time

GND ground

GCS gate control signal

PAS pre-attenuated signal

PAP Pre-Attenuation Pulse

PDT Pseudo Dead Time

PRI primary side

PV Predetermined voltage value

SEC Secondary Side

T1-T3 time

TDIS discharge time

VDET detection voltage

VREF1 first reference voltage

VREF2 second reference voltage

VREF3 third reference voltage

VMIM minimum

500-508 steps

Detailed ways

Please refer to FIG. 3 . FIG. 3 is a schematic diagram of a synchronous rectifier 300 applied to the secondary side SEC of the power converter 100 disclosed in the first embodiment of the present invention, wherein the primary side PRI of the power converter 100 is only the primary side Winding 101 and a power switch 103 are shown in FIG. 3 , the power converter 100 is an AC/DC power converter, the synchronous rectifier 300 is suitable for the continuous conduction mode of the power converter 100 , and GND represents a ground terminal. As shown in FIG. 3 , the synchronous rectifier 300 includes a control signal generating circuit 302 , a pre-attenuation circuit 304 and a gate driving circuit 306 , wherein the pre-attenuation circuit 304 is coupled to the control signal generating circuit 302 and the gate driving circuit 306 It is coupled to the control signal generating circuit 302 and the pre-attenuating circuit 304 . When the secondary side SEC of the power converter 100 is turned on, the control signal generating circuit 302 receives the detection voltage VDET corresponding to the current cycle of the secondary side SEC of the power converter 100 through the pin 308 of the synchronous rectifier 300 (that is, the power supply source voltage of the synchronous switch 102 of the secondary side SEC of the converter 100). After the control signal generation circuit 302 receives the detection voltage VDET corresponding to the current period, the control signal generation circuit 302 can generate a voltage VDET corresponding to the current period, a first reference voltage VREF1 and a second reference voltage VREF2 according to the detection voltage VDET, a first reference voltage VREF1 and a second reference voltage VREF2. For the control signal CS corresponding to the current period, the timing sequence of the detection voltage VDET corresponding to the current period and the control signal CS corresponding to the current period can be referred to FIG. 4 . As shown in FIG. 4 , at a time T1, the control signal generating circuit 302 can enable the control signal CS corresponding to the current period according to the detection voltage VDET corresponding to the current period and the first reference voltage VREF1, and at a time T2 , the control signal generating circuit 302 can turn off the control signal CS corresponding to the current period according to the detection voltage VDET corresponding to the current period and the second reference voltage VREF2 , where the second reference voltage VREF2 is greater than the first reference voltage VREF1 . Therefore, as shown in FIG. 4 , the control signal CS corresponding to the current period is the discharge time TDIS corresponding to the current period. In addition, as shown in FIG. 4 , the gate driving circuit 306 is configured to drive the gate control signal GCS corresponding to the current period and the gate control signal corresponding to the current period according to the control signal CS corresponding to the current period. GCS is transmitted to the synchronous switch 102 of the secondary side SEC of the power converter 100 through a pin 310 , and the gate control signal GCS corresponding to the current period is used to control the opening and closing of the synchronous switch 102 .

As shown in FIG. 3 , the pre-attenuation circuit 304 includes a pre-attenuation signal generator 3042, a pulse generator 3044 and a pull-down circuit 3046, wherein the pre-attenuation signal generator 3042 is coupled to the control signal generation circuit 302, and the pulse generator 3044 Coupled to the pre-attenuation signal generator 3042, the pull-down circuit 3046 is coupled to the pulse generator 3044 and the pre-attenuation signal generator 3042, and the pull-down circuit 3046 includes a first N-type MOS transistor 30462, a second N-type MOS transistor 30464 and a switch 30466. In addition, the control signal generating circuit 302, the gate driving circuit 306, the pre-attenuation signal generator 3042, the pulse generator 3044, the first NMOS transistor 30462, the second NMOS transistor 30464 and the switch 30466 The coupling relationship between them can be referred to FIG. 3 , which is not repeated here.

The pre-attenuation signal generator 3042 can generate the corresponding to the said The current pre-attenuation time CT of the current period (as shown in FIG. 4 ) and the pre-attenuation signal PAS corresponding to the current pre-attenuation time CT (wherein the pre-attenuation signal PAS corresponding to the current pre-attenuation time CT also corresponds to the current period). For example, initially the pre-attenuation signal generator 3042 can generate the first cycle corresponding to the secondary side SEC of the power converter 100 according to the discharge time corresponding to the zeroth cycle of the secondary side SEC of the power converter 100 and a preset time value The first pre-attenuation time of the power converter 100 and the pre-attenuation signal corresponding to the first pre-attenuation time; then the pre-attenuation signal generator 3042 can be based on the discharge time corresponding to the first cycle of the secondary side SEC of the power converter 100 and the first a pre-attenuation time, to generate a second pre-attenuation time corresponding to the second period of the secondary side SEC of the power converter 100 and a pre-attenuation signal corresponding to the second pre-attenuation time; then the pre-attenuation signal generator 3042 can The discharge time and the second pre-decay time of the second cycle of the secondary side SEC of the power converter 100 generate a third pre-decay time corresponding to the third cycle of the secondary side SEC of the power converter 100 and the second pre-decay time corresponding to the A pre-decay signal for a third pre-decay time; and so on, wherein the third period is after the second period, the second period is after the first period, and the first period is after the first period After the zeroth cycle. Therefore, the current pre-attenuation time CT of the current cycle corresponding to the secondary side SEC of the power converter 100 generated by the pre-attenuation signal generator 3042 according to the discharge time of the previous cycle corresponding to the secondary side SEC of the power converter 100 will gradually Approaching the discharge time corresponding to the previous cycle of the secondary side SEC of the power converter 100, but the pre-attenuation signal generator 3042 will make a pseudo dead time (PDT) as shown in FIG. 4 not less than one predetermined time interval.

In addition, in an embodiment of the present invention, the pre-attenuation signal generator 3042 averages the discharge time corresponding to the zeroth cycle and the preset time value to generate the first SEC corresponding to the secondary side of the power converter 100 . The first pre-attenuation time of the cycle, but the present invention is not limited to the pre-attenuation signal generator 3042 to average the discharge time corresponding to the zeroth cycle and the preset time value to generate a secondary side corresponding to the power converter 100 The first pre-attenuation time of the first cycle of the SEC, that is to say, the pre-attenuation signal generator 3042 may also weight the discharge time corresponding to the zeroth cycle and the preset time value to generate a secondary signal corresponding to the power converter 100 . The first pre-decay time of the first cycle of the side SEC. Therefore, as long as the pre-attenuation signal generator 3042 uses the discharge time corresponding to the previous cycle of the secondary side SEC of the power converter 100 to generate the current pre-attenuation time CT corresponding to the current cycle of the secondary side SEC of the power converter 100 fall within the scope of the present invention.

As shown in FIG. 3 , after the pre-attenuation signal generator 3042 generates the pre-attenuation signal PAS corresponding to the current period, the gate driving circuit 306 will stop driving the gate control signal GCS corresponding to the current period.

In addition, as shown in FIG. 4 , the pulse generator 3044 is configured to generate a pre-attenuation pulse PAP corresponding to the current period at a time T3 according to the pre-attenuation signal PAS corresponding to the current period. Therefore, as shown in FIG. 3, after the pulse generator 3044 generates the pre-attenuation pulse PAP corresponding to the current period, the first NMOS transistor 30462 is turned on because the gate driving circuit 306 stops driving the current period corresponding to the current period. period of the gate control signal GCS, so the gate control signal GCS corresponding to the current period will be pre-attenuated (as shown in FIG. 4 ). In addition, because the switch 30466 is turned on according to the pre-attenuation signal PAS corresponding to the current period, the second NMOS transistor 30464 is turned on according to a third reference voltage VREF3, resulting in a gate control signal corresponding to the current period The GCS is regulated to a predetermined voltage value PV (as shown in FIG. 4 ), wherein the predetermined voltage value PV can be determined by the third reference voltage VREF3 , the threshold voltage VTH30464 of the second N-type metal oxide semiconductor transistor 30464 and equation (1) :

PV=VREF3–VTH30464 (1)

In addition, in another embodiment of the present invention, the switch 30466 and the second NMOS transistor 30464 can be replaced by a clamp circuit, that is to say, the clamp circuit can be based on the preset corresponding to the current cycle. The attenuation signal PAS stabilizes the gate control signal GCS at a predetermined voltage value PV.

Because the synchronous rectifier 300 pre-attenuates the gate control signal GCS corresponding to the current cycle according to the discharge time corresponding to the previous cycle, the load 104 coupled to the secondary side SEC of the power converter 100 is lightly loaded. , the synchronous rectifier 300 does not pre-attenuate the gate control signal GCS corresponding to the current period in advance to avoid the synchronous switch 102 operating in the triode region most of the time, and when the load 104 is very heavy, the synchronous rectifier 300 does not have to directly The gate control signal GCS corresponding to the current period is turned off.

Please refer to FIGS. 3-5 . FIG. 5 is a flowchart of an operation method of a synchronous rectifier applied to a power converter disclosed in a second embodiment of the present invention. The operation method of FIG. 5 is described by using the power converter 100 and the synchronous rectifier 300 of FIG. 3 , and the detailed steps are as follows:

Step 500: start;

Step 502 : When the secondary side SEC of the power converter 100 is turned on, the control signal generating circuit 302 is based on the detection voltage VDET, the first reference voltage VREF1 and the second reference corresponding to the previous cycle of the secondary side SEC of the power converter 100 . The voltage VREF2 generates the control signal CS corresponding to the previous cycle of the secondary side SEC of the power converter 100;

Step 504: The pre-attenuation signal generator 3042 generates a pre-attenuation signal PAS corresponding to the current cycle of the secondary side SEC of the power converter 100 according to the control signal CS corresponding to the previous cycle;

Step 506: The pulse generator 3044 generates a pre-attenuation pulse PAP corresponding to the current period of the secondary side SEC of the power converter 100 according to the pre-attenuation signal PAS of the current period corresponding to the secondary side SEC of the power converter 100;

Step 508: The pull-down circuit 3046 pre-attenuates the gate control signal GCS corresponding to the current cycle of the secondary side SEC of the power converter 100 according to the pre-attenuation pulse PAP corresponding to the current cycle of the secondary side SEC of the power converter 100, and jumps back to Step 502.

In step 502, when the secondary side SEC of the power converter 100 is turned on in the previous cycle of the secondary side SEC of the power converter 100, the control signal generating circuit 302 receives the corresponding signal through the pin 308 of the synchronous rectifier 300 The detection voltage VDET of the previous cycle. After the control signal generation circuit 302 receives the detection voltage VDET corresponding to the previous cycle, the control signal generation circuit 302 can generate the detection voltage VDET corresponding to the previous cycle, the first reference voltage VREF1 and the second reference voltage VREF2 according to the detection voltage VDET corresponding to the previous cycle. Corresponds to the control signal CS of the previous cycle. Similarly, when the secondary side SEC of the power converter 100 is turned on in the current cycle of the secondary side SEC of the power converter 100, the control signal generating circuit 302 can also be based on the detection voltage VDET corresponding to the current cycle, the first reference The voltage VREF1 and the second reference voltage VREF2 generate the control signal CS corresponding to the current period.

In step 504 , as shown in FIG. 3 , the pre-attenuation signal generator 3042 can be based on the discharge time of the previous cycle corresponding to the secondary side SEC of the power converter 100 (corresponding to the previous cycle of the secondary side SEC of the power converter 100 ) Periodic control signal CS) to generate a current pre-attenuation time CT (as shown in FIG. 4 ) corresponding to the current period and a pre-attenuation signal PAS corresponding to the current pre-attenuation time CT. Therefore, the current pre-attenuation time CT of the current cycle corresponding to the secondary side SEC of the power converter 100 generated by the pre-attenuation signal generator 3042 according to the discharge time of the previous cycle corresponding to the secondary side SEC of the power converter 100 will gradually Approaching the discharge time corresponding to the previous cycle of the secondary side SEC of the power converter 100, but the pre-attenuation signal generator 3042 makes the pseudo dead time PDT as shown in FIG. 4 not less than the predetermined time interval.

In steps 506 and 508 , as shown in FIG. 4 , the pulse generator 3044 generates a pre-attenuation pulse PAP corresponding to the current period at time T3 according to the pre-attenuation signal PAS corresponding to the current period. Therefore, as shown in FIG. 3, after the pulse generator 3044 generates the pre-attenuation pulse PAP corresponding to the current period, the first NMOS transistor 30462 is turned on because the gate driving circuit 306 stops driving the current period corresponding to the current period. period of the gate control signal GCS, so the gate control signal GCS corresponding to the current period will be pre-attenuated (as shown in FIG. 4 ). In addition, because the switch 30466 is turned on according to the pre-attenuation signal PAS corresponding to the current period, the second NMOS transistor 30464 is turned on according to the third reference voltage VREF3, resulting in the gate control signal GCS corresponding to the current period is regulated at a predetermined voltage value PV (as shown in Figure 4).

In addition, as shown in FIGS. 3 and 4 , the gate driving circuit 306 can drive the gate control signal GCS corresponding to the current period according to the control signal CS corresponding to the current period, and generate a corresponding signal in the pre-attenuation signal generator 3042 After the pre-attenuation signal PAS of the current period, the gate driving circuit 306 will stop driving the gate control signal GCS corresponding to the current period.

To sum up, the synchronous rectifier applied to the power converter and the operation method thereof disclosed in the present invention utilize the control signal generating circuit when the secondary side of the power converter is turned on, according to the corresponding secondary side The detection voltage of the previous cycle, the first reference voltage and the second reference voltage, generate a control signal corresponding to the previous cycle, and use the pre-attenuation circuit according to the discharge time corresponding to the previous cycle. (corresponding to the control signal of the previous cycle), pre-attenuate the gate control signal corresponding to the current cycle of the secondary side. Because the synchronous rectifier and the operating method pre-attenuate the gate control signal corresponding to the current cycle according to the discharge time corresponding to the previous cycle, when the power converter is coupled to the secondary side of the power converter When the load is light, the synchronous rectifier does not pre-damp the gate control signal corresponding to the current period in advance to avoid the synchronous switch operating in the triode region most of the time, and when the load is very heavy, The synchronous rectifier does not need to directly turn off the gate control signal corresponding to the current period.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. a synchronous rectifier applied to a power converter is characterized in that comprising: a control signal generating circuit for turning on the control corresponding to the previous cycle according to the detection voltage corresponding to the previous cycle of the secondary side and a first reference voltage when the secondary side of the power converter is turned on signal, and turn off the control signal corresponding to the previous cycle according to the detection voltage corresponding to the previous cycle of the secondary side and a second reference voltage, wherein the control signal corresponding to the previous cycle is the control signal corresponding to the previous cycle the discharge time of the cycle; a pre-attenuation circuit, coupled to the control signal generating circuit, configured to pre-attenuate the gate control signal corresponding to the current cycle of the secondary side and generate a gate control signal corresponding to the current cycle according to the control signal corresponding to the previous cycle a periodic pre-attenuated signal; and a gate driving circuit, coupled to the control signal generating circuit and the pre-attenuation circuit, for driving the gate control signal corresponding to the current period according to the control signal corresponding to the current period, and according to the control signal corresponding to the current period The pre-attenuation signal of the current period is described below, and the gate control signal corresponding to the current period is stopped from driving. 2 . The synchronous rectifier of claim 1 , wherein the detection voltage is the source voltage of the synchronous switch on the secondary side. 3 . 3 . The synchronous rectifier according to claim 1 , wherein the gate control signal of the current period is used to control the opening and closing of the synchronous switch of the secondary side. 4 . 4. The synchronous rectifier of claim 1, wherein the pre-attenuation circuit comprises: a pre-attenuation signal generator, coupled to the control signal generating circuit, for generating a pre-attenuation signal corresponding to the current period according to the control signal corresponding to the previous period; a pulse generator, coupled to the pre-attenuation signal generator, for generating a pre-attenuation pulse corresponding to the current period according to the pre-attenuation signal corresponding to the current period; and A pull-down circuit, coupled to the pulse generator and the pre-attenuation signal generator, is configured to pre-attenuate the gate control signal corresponding to the current period according to the pre-attenuation pulse corresponding to the current period. 5. An operation method of a synchronous rectifier applied to a power converter, wherein the synchronous rectifier comprises a control signal generating circuit, a pre-attenuation circuit and a gate drive circuit, characterized by comprising: When the secondary side of the power converter is turned on, the control signal generating circuit turns on the control signal corresponding to the previous cycle according to the detection voltage corresponding to the previous cycle of the secondary side and a first reference voltage, and turn off the control signal corresponding to the previous cycle according to the detection voltage corresponding to the previous cycle of the secondary side and a second reference voltage, wherein the control signal corresponding to the previous cycle is corresponding to the secondary side the discharge time of the previous cycle; and The pre-attenuation circuit pre-attenuates the gate control signal corresponding to the current period of the secondary side and generates a pre-attenuation signal corresponding to the current period according to the control signal corresponding to the previous period. 6. operating method as claimed in claim 5 is characterized in that additionally comprising: The gate driving circuit drives the gate control signal corresponding to the current period according to the control signal corresponding to the current period; and The gate driving circuit stops driving the gate control signal corresponding to the current period according to the pre-attenuation signal corresponding to the current period. 7. The operating method of claim 5, wherein the detection voltage is a source voltage of a synchronous switch of the secondary side. 8 . The operation method of claim 5 , wherein the gate control signal of the current period is used to control the opening and closing of the synchronous switch of the secondary side. 9 . 9 . The operation method of claim 5 , wherein the pre-attenuation circuit pre-attenuates the gate control signal corresponding to the current period and generates a gate control signal corresponding to the current period according to the discharge time corresponding to the previous period. 10 . The periodic pre-attenuated signal contains: The pre-attenuation signal generator of the pre-attenuation circuit generates a pre-attenuation signal corresponding to the current period according to the control signal corresponding to the previous period; The pulse generator of the pre-attenuation circuit generates a pre-attenuation pulse corresponding to the current period according to the pre-attenuation signal corresponding to the current period; and The pull-down circuit of the pre-attenuation circuit pre-attenuates the gate control signal corresponding to the current period according to the pre-attenuation pulse corresponding to the current period.

Images