阅读说明：本技术 脉冲信号电平的计算方法和计算电路 (Pulse signal level calculation method and calculation circuit ) 是由 毛浪 于 2018-03-26 设计创作，主要内容包括：本发明公开了一种脉冲信号电平的计算方法和计算电路。本发明通过在脉冲信号电平变化时,检测时钟信号的状态,然后在所述脉冲信号的下个周期,根据所检测到的时钟信号的状态,控制时钟信号延迟不同时间触发,自所述时钟信号触发时刻起,分别对所述脉冲信号处于第一电平和当前周期内的时钟信号计数获得第一计数值和第二计数值,并据此获得所述脉冲信号的占空比。通过此方式获得的第一计数值、第二计数值及占空比在所述脉冲信号的每个周期内均相同,因此,可以有效地消除计数误差,提高占空比精度,消除屏幕闪烁。(The invention discloses a method and a circuit for calculating the level of a pulse signal. The invention detects the state of the clock signal when the level of the pulse signal changes, then controls the clock signal to delay different time triggering according to the detected state of the clock signal in the next period of the pulse signal, counts the clock signal of the pulse signal in the first level and the current period respectively from the triggering time of the clock signal to obtain a first count value and a second count value, and obtains the duty ratio of the pulse signal according to the first count value and the second count value. The first count value, the second count value and the duty ratio obtained in the mode are the same in each period of the pulse signal, so that the counting error can be effectively eliminated, the accuracy of the duty ratio is improved, and screen flicker is eliminated.)

1. A method for calculating a level of a pulse signal, comprising the steps of:

1) when a first detection signal representing the level jump of the pulse signal is received, a state signal representing the state of a clock signal is generated; the first detection signal is used for indicating that the pulse signal jumps from a first level to a second level;

2) in the next period of the pulse signal, generating a trigger signal according to the state signal to control the clock signal to delay different delay time triggers, so that after the delay time is delayed, the rising edge of the clock signal does not fall in a time interval for generating misjudgment on the rising edge of the clock signal;

3) counting the clock signals between the trigger signal and the first detection signal to obtain a first count value representing the duration of the first level.

2. The computing method of claim 1, further comprising the steps of: and obtaining a second count value representing the period length of the pulse signal based on the clock signal period, and obtaining the duty ratio of the first level of the pulse signal according to the ratio of the first count value and the second count value.

3. The computing method according to claim 2, characterized in that: counting the clock signal between the trigger signal and a second detection signal representing the level jump of the pulse signal to obtain the second count value, wherein the second detection signal represents the change of the pulse signal from the second level jump to the first level.

4. The computing method according to any one of claims 2 or 3, characterized in that: the first count value, the second count value, and the duty ratio are the same in each period of the pulse signal.

5. The computing method according to claim 1, characterized in that: the calculation method further comprises the following steps: calculating the first level duration length according to N1 × Tclock + Tdelay, where N1 is the first count value, Tclock is the period of the clock signal, and Tdelay is the delay time.

6. The computing method according to claim 1, wherein the step 2) comprises:

if the state signal represents that the clock signal is in a first state, delaying the clock signal for triggering by first delay time in the next period of the pulse signal;

and if the state signal represents that the clock signal is in a second state, delaying the clock signal for a second delay time for triggering in the next period of the pulse signal.

7. The computing method of claim 6, wherein: the first delay time is greater than the second delay time.

8. The computing method of claim 7, wherein: the difference between the first delay time and the second delay time is configured to be not more than n/2Tclock-Tnoise, where Tclock is the period of the clock signal, Tnoise is the time when noise and jitter affect the pulse signal and the clock signal, and n is a natural number.

9. The computing method of claim 6, wherein: delaying the clock signal by the first delay time trigger in a first cycle of the pulse signal.

10. The computing method according to claim 1, characterized in that: the delay time is an integral multiple of the clock signal period.

11. A circuit for calculating a level of a pulse signal, the circuit comprising:

the clock signal detection module is used for receiving a first detection signal representing the level change of the pulse signal and generating a state signal representing the state of the clock signal;

the delay triggering module is used for generating a triggering signal according to the state signal in the next period of the pulse signal to control the clock signal to delay different delay time triggering, so that after the delay time is delayed, the rising edge of the clock signal cannot fall into a time interval for generating misjudgment on the rising edge of the clock signal;

and the counter module is used for counting the clock signals from the trigger signal to the first detection signal to obtain a first count value, and the first detection signal represents that the pulse signal jumps from a first level to a second level.

12. The computing circuit of claim 11, wherein:

if the detected state of the clock signal is a first state, the delay triggering module generates the triggering signal to control the clock signal to delay a first delay time trigger in the next period of the pulse signal;

if the detected state of the clock signal is the second state, the delay triggering module generates the triggering signal to control the clock signal to delay the triggering of the second delay time in the next period of the pulse signal.

13. The computing circuit of claim 12, wherein the computing circuit further comprises:

and the duty ratio calculation module is used for obtaining the duty ratio of the first level of the pulse signal according to the ratio of the first count value and a second count value, wherein the second count value is obtained based on the period of the clock signal and is used for representing the period length of the pulse signal.

14. The computing circuit of claim 13, wherein: the counter module is further used for counting the clock signals from the trigger signal to a second detection signal to obtain a second count value, wherein the second detection signal represents that the pulse signal jumps from a second level to a first level.

15. The computing circuit of claim 14, wherein the computing circuit further comprises:

and the pulse signal detection module is used for detecting the level change of the pulse signal and generating the first detection signal and the second detection signal for representing the level change of the pulse signal.

16. The computing circuit of claim 14, wherein the delay trigger module comprises: a switch, a second delay time generating circuit and a third delay time generating circuit,

the second delay time generating circuit is connected in series with the third delay time generating circuit, the input end of the second delay time generating circuit receives the second detection signal, and the output end of the third delay time generating the trigger signal;

the switch is connected with the third delay time generation circuit in parallel, and the control end of the switch is controlled by the state signal; if the state signal represents that the clock signal is in a first state, the state signal controls the switch to be switched off in the next period of the pulse signal; if the state signal represents that the clock signal is in a second state, the state signal controls the switch to be closed to enable the third delay time generation circuit to be in a short circuit in the next period of the pulse signal;

the first delay time is the sum of a second delay time generated by the second delay time generating circuit and a third delay time generated by the third delay time generating circuit.

17. The computing circuit of any of claims 11-16, wherein the computing circuit further comprises: and the clock signal generating module is used for receiving the trigger signal and generating the clock signal.

Technical Field

The present invention relates to power electronics technologies, and in particular, to a method and a circuit for calculating a pulse signal level.

Background

The LED backlight analog dimming technology generally needs to obtain duty ratio information of a PWM signal, and currently, the counter method is most widely used. For example, the reference Clock signal Clock is used as a sampling signal to sample and count the high level time Ton and the whole period T of the PWM signal, and the duty ratio is the count ratio of Ton to T. The higher the frequency of the reference Clock signal Clock, the more accurate the calculated duty cycle.

However, the PWM signal and the reference Clock signal Clock may not be synchronized. As shown in fig. 1, a signal timing diagram for calculating the duty ratio of a PWM signal for a counter method. In fig. 1, since the lengths of the high time Ton and the period T of the PWM signal are not necessarily integer multiples of the reference Clock signal Clock, the counts of the high time Ton and the period T may be different in different PWM periods. In this case, the accuracy of the duty ratio calculation may be reduced.

In order to improve the accuracy of the duty ratio calculation, there is a method of synchronizing the PWM signal and the reference Clock signal Clock. As shown in fig. 2, a signal timing chart of the duty ratio of the PWM signal is calculated by a synchronization method. In fig. 2, the PWM signal and the reference Clock signal Clock are synchronized. The reference Clock signal Clock is detected to be high at the falling edge of the high time Ton of the PWM signal of the first period, and is detected to be low at the falling edge of the high time Ton of the next PWM period due to the falling edge being close to the rising edge of the reference Clock signal Clock under the influence of noise and signal jitter. Thus, there is 1 error in counting the high time Ton in the two PWM periods. The smaller the high time Ton, the larger the duty cycle variation in different periods due to the error. If the method is applied to a screen of an electronic device, when the change of the duty ratio reaches a certain value, human eyes can observe the phenomenon of flickering.

Disclosure of Invention

In view of this, embodiments of the present invention provide a method and a circuit for calculating a pulse signal level, so as to effectively eliminate a counting error, improve a duty ratio accuracy, and eliminate screen flicker.

In one aspect, the present invention provides a method for calculating a pulse signal level, including the following steps:

1) when a first detection signal representing the level jump of the pulse signal is received, a state signal representing the state of a clock signal is generated; the first detection signal is used for indicating that the pulse signal jumps from a first level to a second level;

2) in the next period of the pulse signal, generating a trigger signal according to the state signal to control the clock signal to delay different delay time triggers, so that after the delay time is delayed, the rising edge of the clock signal does not fall in a time interval for generating misjudgment on the rising edge of the clock signal;

3) counting the clock signals between the trigger signal and the first detection signal to obtain a first count value representing the duration of the first level.

Preferably, the calculation method further comprises the steps of: and obtaining a second count value representing the period length of the pulse signal based on the clock signal period, and obtaining the duty ratio of the first level of the pulse signal according to the ratio of the first count value and the second count value.

Preferably, the clock signal between the trigger signal and a second detection signal indicating the level transition of the pulse signal is counted to obtain the second count value, and the second detection signal indicating the level transition of the pulse signal from the second level to the first level.

Preferably, the first count value, the second count value, and the duty ratio are the same in each period of the pulse signal.

Preferably, the calculation method further comprises the steps of: calculating the first level duration length according to N1 × Tclock + Tdelay, where N1 is the first count value, Tclock is the period of the clock signal, and Tdelay is the delay time.

Preferably, step 2) comprises:

if the state signal represents that the clock signal is in a first state, delaying the clock signal for triggering by first delay time in the next period of the pulse signal;

and if the state signal represents that the clock signal is in a second state, delaying the clock signal for a second delay time for triggering in the next period of the pulse signal.

Preferably, the first delay time is greater than the second delay time.

Preferably, a difference between the first delay time and the second delay time is configured to be not greater than n/2Tclock-Tnoise, where Tclock is a period of the clock signal, Tnoise is a time at which noise and jitter affect the pulse signal and the clock signal, and n is a natural number.

Preferably, the clock signal is delayed by the first delay time trigger in a first cycle of the pulse signal.

Preferably, the delay time is an integer multiple of the period of the clock signal.

In another aspect, the present invention provides a pulse signal level calculating circuit, including:

the clock signal detection module is used for receiving a first detection signal representing the level change of the pulse signal and generating a state signal representing the state of the clock signal;

the delay triggering module is used for generating a triggering signal according to the state signal in the next period of the pulse signal to control the clock signal to delay different delay time triggering, so that after the delay time is delayed, the rising edge of the clock signal cannot fall into a time interval for generating misjudgment on the rising edge of the clock signal;

and the counter module is used for counting the clock signals from the trigger signal to the first detection signal to obtain a first count value, and the first detection signal represents that the pulse signal jumps from a first level to a second level.

Preferably, if the detected state of the clock signal is a first state, the delay triggering module generates the trigger signal to control the clock signal to delay the first delay time trigger in a next cycle of the pulse signal;

if the detected state of the clock signal is the second state, the delay triggering module generates the triggering signal to control the clock signal to delay the triggering of the second delay time in the next period of the pulse signal.

Preferably, the calculation circuit further comprises:

and the duty ratio calculation module is used for obtaining the duty ratio of the first level of the pulse signal according to the ratio of the first count value and a second count value, wherein the second count value is obtained based on the period of the clock signal and is used for representing the period length of the pulse signal.

Preferably, the counter module further counts the clock signal between the trigger signal and a second detection signal to obtain the second count value, and the second detection signal indicates that the pulse signal jumps from a second level to a first level.

Preferably, the calculation circuit further comprises:

and the pulse signal detection module is used for detecting the level change of the pulse signal and generating the first detection signal and the second detection signal for representing the level change of the pulse signal.

Preferably, the delay triggering module includes: a switch, a second delay time generating circuit and a third delay time generating circuit,

the second delay time generating circuit is connected in series with the third delay time generating circuit, the input end of the second delay time generating circuit receives the second detection signal, and the output end of the third delay time generating the trigger signal;

the switch is connected with the third delay time generation circuit in parallel, and the control end of the switch is controlled by the state signal; if the state signal represents that the clock signal is in a first state, the state signal controls the switch to be switched off in the next period of the pulse signal; if the state signal represents that the clock signal is in a second state, the state signal controls the switch to be closed to enable the third delay time generation circuit to be in a short circuit in the next period of the pulse signal;

the first delay time is the sum of a second delay time generated by the second delay time generating circuit and a third delay time generated by the third delay time generating circuit.

Preferably, the calculation circuit further comprises: and the clock signal generating module is used for receiving the trigger signal and generating the clock signal.

According to the technical scheme of the embodiment of the invention, when the level of the pulse signal changes, the state of the clock signal is detected, then in the next period of the pulse signal, the clock signal is controlled to delay different time triggers according to the detected state of the clock signal, and from the triggering time of the clock signal, the clock signals of the pulse signal in the first level and the current period are respectively counted to obtain a first count value and a second count value, and accordingly, the duty ratio of the pulse signal is obtained. The duty ratio value obtained by the method is the same in each period of the pulse signal, so that the counting error can be effectively eliminated, the duty ratio precision is improved, and the screen flicker is eliminated.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 is a signal timing diagram of a conventional counter method for calculating the duty ratio of a PWM signal;

FIG. 2 is a signal timing diagram of a prior art method for calculating the duty ratio of a PWM signal by using a synchronization method;

FIG. 3 is a flowchart of a method for calculating a duty cycle of a pulse signal according to an embodiment of the present invention;

FIG. 4 is a timing diagram of signals using the calculation method shown in FIG. 3;

FIGS. 5-7 show steady state timing diagrams for 3 different PWM signals, respectively, using the calculation shown in FIG. 3;

FIG. 8 is a block diagram of a pulse signal duty cycle calculation circuit according to an embodiment of the present invention;

fig. 9 is a schematic diagram of a delay trigger module according to an embodiment of the invention.

Detailed Description

The present invention will be described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details. Well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.

Further, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.

Meanwhile, it should be understood that, in the following description, a "circuit" refers to a conductive loop constituted by at least one element or sub-circuit through electrical or electromagnetic connection. When an element or circuit is referred to as being "connected to" another element or element/circuit is referred to as being "connected between" two nodes, it may be directly coupled or connected to the other element or intervening elements may be present, and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, it is intended that there are no intervening elements present.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, what is meant is "including, but not limited to".

In the description of the present invention, it is to be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.

Fig. 3 is a flowchart of a method for calculating a duty ratio of a pulse signal according to an embodiment of the present invention. As shown in fig. 3, the calculation method includes:

step S100: when a first detection signal representing the level transition of the pulse signal is received, a state signal representing the state of the clock signal is generated.

Step S200: and in the next period of the pulse signal, generating a trigger signal according to the state signal to control the clock signal to delay different delay time for triggering.

Step S200 specifically includes:

step S201: if the state signal indicates that the clock signal is in the first state, delaying the clock signal by a first delay time Tdelay1 for triggering in the next period of the pulse signal;

step S202: and if the state signal indicates that the clock signal is in the second state, delaying the clock signal by a second delay time Tdelay2 for the next period of the pulse signal.

The first delay time is greater than the second delay time. In one example, the first delay time Tdelay1 and the second delay time Tdelay2 satisfy: tnoise < Tdelay1-Tdelay2< n/2Tclock-Tnoise, wherein Tnoise is the influence time of noise and jitter on the pulse signal and the clock signal, Tclock is the period of the clock signal, and n is a natural number.

Step S300: counting the clock signals from the trigger signal to the first detection signal to obtain a first count value.

Step S400: counting the clock signals from the trigger signal to a second detection signal representing the level transition of the pulse signal to obtain a second value;

step S500: and obtaining the duty ratio of the pulse signal according to the first count value and the second count value.

Specifically, in step S500, since the delay time is small, the accuracy of the duty ratio is not affected, and therefore, the duty ratio of the pulse signal can be obtained according to the ratio of the first count value and the second count value. In one example, the first delay time and the second delay time may be set to be an integer multiple of the period of the clock signal, and the timing is set to start from the integer multiple of the period of the clock signal so that the timing at which the timing starts coincides with the trigger signal.

In the above or below embodiments, the pulse signal may be a PWM signal or other pulse signals with different levels; the first level may be a high level and the second level may be a low level accordingly; or the first level may be a low level and the second level may be a high level accordingly; the clock signal is a high frequency signal having a frequency higher than the pulse signal. Of course, the forms of the pulse signal and the clock signal are not limited to the above examples. The first state may be a low state and the second state may be a high state; or the first state may be a low state and the second state may be a high state. Of course, the forms of the first state and the second state are not limited to the above examples.

For a better understanding of the calculation method in fig. 3, a detailed description is given below in conjunction with fig. 4.

For clarity, the following description will take an example in which the pulse signal is a PWM signal and the first detection signal indicates that the PWM signal jumps from a high level to a low level, the second detection signal indicates that the PWM signal jumps from a low level to a high level and the first state of the clock signal is a low level state and the second state is a high level state.

As shown in fig. 4, a signal timing chart of the calculation method shown in fig. 3 is shown, wherein the Clock signals Clock1 and Clock2 respectively represent the timing of two different cases (i.e. the delay time is the first delay time and the second delay time).

First, the state of the Clock signal Clock is detected when the PWM signal jumps from a high level to a low level (i.e., a falling edge).

If the detected Clock signal Clock1 is in a low state, the Clock signal Clock1 is delayed by the first delay time Tdelay1 for the next period of the PWM signal.

If the detected Clock signal Clock2 is in a high state, the Clock signal Clock2 is delayed by a second delay time Tdelay2 for the next period of the PWM signal.

Previously, it was mentioned in the description of fig. 2 that, assuming that the influence time of noise and jitter on the PWM signal and the Clock signal is Tnoise, when the rising edge of the Clock signal Clock falls within the Tnoise interval, the count value has 1 error, i.e., the Tnoise interval is a time interval in which the rising edge of the Clock signal may be misjudged. After the calculation method shown in fig. 3 is adopted, as shown in fig. 4, no matter the delay time is the first delay time or the second delay time, the rising edge of the Clock signal Clock does not fall in the Tnoise interval, that is, after the delay time is delayed, the rising edge of the Clock signal does not fall in the time interval in which the rising edge of the Clock signal is misjudged, so that the counting error of the on-time and the period of the PWM signal is eliminated.

Fig. 5-7 show steady state timing diagrams for 3 different PWM signals, respectively, using the calculation of fig. 3.

As shown in fig. 5, at the falling edge of each PWM signal, the Clock signal Clock is detected to be low, and therefore, in the next period of each PWM signal, the Clock signal Clock is triggered with a delay of the first delay time Tdelay 1. A first count value obtained by counting the clock signals from the triggering time of the clock signal to the falling edge of the PWM signal is N1, and a second count value obtained by counting the clock signals from the triggering time of the clock signals to the time when the PWM signal again appears is N2, so that the high level time of the PWM signal is N1 Tclock + Tdelay1, and the period is N2 Tclock + Tdelay1, so that the duty ratio D (N1 Tclock + Tdelay1)/(N2 Tclock + Tdelay1) is negligible, and the duty ratio D can be simplified to be N1 Tclock/N3N 1/N2, that is, the duty ratio of the PWM signal can be obtained according to the ratio of the first count value and the second count value. In this case, the on-time and the count value of the period for the PWM signal are the same in each period.

As shown in fig. 6, at the falling edge of each PWM signal, the Clock signal Clock is detected to be high, and therefore, in the next period of each PWM signal, the Clock signal Clock is delayed by the second delay time Tdelay2 to trigger. As a first count value obtained by counting the clock signals from the triggering time of the clock signal to the falling edge of the PWM signal is N1 ', and a second count value obtained by counting the clock signals from the triggering time of the clock signal to the time when the PWM signal again rises is N2', it can be seen that the high level time of the PWM signal is N1 'Tclock + Tdelay2, and the period is N2' Tclock + Tdelay2, so that the duty ratio D is (N1 'Tclock + Tdelay 2)/(N2' Tclock + Tdelay2), and similarly, since the second delay time Tdelay2 is small, it is negligible, so the duty ratio D can be simplified to be N1 'Tclock/N2' lock N1 '/N2', that is the duty ratio of the first count value and the second count value of the PWM signal. Also in this case, the on-time and the count value of the period for the PWM signal are the same in each period.

As shown in fig. 7, the Clock signal Clock is detected to be in a low state at the falling edge of the first period of the PWM signal, and is delayed by a first delay time Tdealy1 to trigger at the second period of the PWM signal, and is detected to be in a high state at the end of the second period, and is delayed by a second delay time Tdelay2 to trigger. Then, during the third and the fourth periods N of the PWM signal … …, the operations in the first and the second periods are repeated, and the Clock signal Clock is triggered by alternately delaying the first delay time Tdelay1 and the second delay time Tdelay 2. In fig. 7, in the first period of the PWM signal, the first count value obtained by counting the clock signals from the triggering time of the clock signal to the falling edge of the PWM signal is N1 ", the second count value obtained by counting the clock signals from the triggering time of the clock signal to the rising edge of the PWM signal again is N2", it is known that the high level time of the PWM signal is N1 "× Tclock + Tdelay1, the period is N2" × Tclock + Tdelay1, so that the duty ratio D is (N1 "× Tclock + Tdelay 1)/(N2" × Tclock + Tdelay1), and similarly, since the delay time Tdelay1 is small, it is negligible, so that in the first period of the PWM signal, the calculation of the duty ratio D can be simplified to be D1 "× Tclock/N383"/73784 ". In the second period of the PWM signal, although the delay time is Tdelay2, the duty ratio D is calculated in the above manner, and is still simplified to be N1 "/N2". Therefore, whether the delay time is the first delay time Tdelay1 or the second delay time Tdelay2, the duty ratio of the PWM signal may be obtained according to the ratio of the first count value and the second count value. Also in this case, the on-time and the count value of the period for the PWM signal are the same in each period.

Fig. 8 is a block diagram of a pulse signal duty ratio calculation circuit according to an embodiment of the present invention. As shown in fig. 8, the pulse signal duty ratio calculation circuit 800 includes:

a clock signal detection module 801, configured to receive the first detection signal VT1 indicating the level change of the pulse signal, and generate a state signal VS indicating the state of the clock signal;

a delay Trigger module 802, configured to generate a Trigger signal Trigger according to the state signal VS in a next cycle of the pulse signal to control the clock signal to delay different delay times for triggering;

a counter module 803, configured to count the clock signals between the Trigger signal Trigger and the first detection signal VT1 to obtain a first count value N1; and counting the clock signals between the Trigger signal Trigger and a second detection signal VT2 to obtain a second value N2;

a duty ratio calculating module 804, configured to obtain a duty ratio D of the pulse signal according to the first count value N1 and the second count value N2.

In one embodiment, the pulse signal duty ratio calculation circuit 800 further includes: the pulse signal detection module 805 is configured to receive a pulse signal and generate a first detection signal VT1 and a second detection signal VT2 for indicating a level change of the pulse signal.

The first detection signal is used for indicating that the pulse signal jumps from a first level to a second level, and the second detection signal is used for indicating that the pulse signal jumps from the second level to the first level.

The pulse signal can be generated by an external device of the chip, such as a PWM signal generating circuit, and is converted into an internal PWM signal through a PWM pin of the chip; or may be given directly by the PWM signal generation circuit inside the chip. Of course, the generation of the pulse signal is not limited to the above manner.

In one embodiment, the pulse signal duty ratio calculation circuit 800 further includes: a Clock signal generating module 806, configured to receive the Trigger signal Trigger and generate the Clock signal Clock.

In one embodiment, the specific working principle of the delay triggering module 802 includes: for example, if the state signal VS indicates that the Clock signal Clock is in the first state, the Trigger signal Trigger controls the Clock signal Clock to Delay triggering by the first Delay time Delay1 relative to the second detection signal VT2 in the next cycle of the pulse signal, that is, when the second detection signal VT2 is received; if the state signal VS represents that the Clock signal Clock is in the second state, the Trigger signal Trigger controls the Clock signal Clock to Delay the second Delay time Delay2 relative to the second detection signal VT2 for triggering in the next cycle of the pulse signal, that is, when the second detection signal VT2 is received.

Fig. 9 is a schematic diagram of a delay trigger module according to an embodiment of the invention. As shown in fig. 9, the delay triggering module 802 includes a Switch, a second delay time generating circuit and a third delay time generating circuit.

The second delay time generating circuit is connected in series with the third delay time generating circuit, an input end of the second delay time generating circuit receives the second detection signal VT2, an output end of the third delay time generating the Trigger signal Trigger, the Switch is connected in parallel with the third delay time generating circuit, and a control end of the Switch is controlled by the state signal VS.

If the state signal VS indicates that the Clock signal Clock is in the first state, the state signal VS controls the Switch to be turned off in the next cycle of the pulse signal, and the Trigger signal Trigger controls the Clock signal Clock to Delay triggering by a first Delay time Delay1 relative to the second detection signal VT2, where the first Delay time Delay1 is the sum of a second Delay time Delay2 generated by the second Delay time generation circuit and a third Delay time Delay3 generated by the third Delay time generation circuit; if the state signal VS indicates that the Clock signal Clock is in the second state, in the next cycle of the pulse signal, the state signal VS controls the Switch to close, so that the third Delay time generation circuit is short-circuited, and thus the Trigger signal Trigger controls the Clock signal Clock to Delay triggering by a second Delay time Delay2 relative to the second detection signal VT 2.

In each of the above embodiments, as a preferable mode, the clock signal is delayed by a first delay time trigger in a first period of the pulse signal. Of course, the clock signal may also delay the second delay time trigger.

According to the technical scheme of the embodiment of the invention, when the level of the pulse signal changes, the state of the clock signal is detected, then in the next period of the pulse signal, the clock signal is controlled to delay different time triggers according to the detected state of the clock signal, and from the triggering time of the clock signal, the clock signals of the pulse signal in the first level and the current period are respectively counted to obtain a first count value and a second count value, and accordingly, the duty ratio of the pulse signal is obtained. The duty ratio value obtained by the method is the same in each period of the pulse signal, so that the counting error can be effectively eliminated, the duty ratio precision is improved, and the screen flicker is eliminated.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.