Self-adaptive linear PWM duty ratio adjusting system and method

Abstract

The invention discloses a self-adaptive linear PWM (Pulse Width Modulation) duty ratio adjusting system and method, belongs to the technical field of driving illumination, and solves the problem of discharge in an emergency scene and the problem of nonlinear influence on PWM duty ratio adjustment caused by voltage fluctuation generated by a lithium battery during discharge and non-discharge. Comprising a switched capacitor sampling circuit, a triangular wave generating circuit, a PWM signal generating circuit and a battery voltage clamping circuit. The input end of the battery voltage clamping circuit is used for being connected with battery voltage, and the output end of the battery voltage clamping circuit is connected with the first input end of the switched capacitor sampling circuit. According to the invention, by sampling the battery voltage and the reference voltage VBG, a triangular wave is generated to regulate the PWM duty ratio, and meanwhile, a low-voltage clamping technology is adopted to ensure that the brightness is stable; the sampling capacitor is sampled in the PWM high / low level stage, so that the interference of voltage fluctuation on PWM is effectively avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of driving lighting technology, in particular to a self-adaptive linear PWM duty cycle adjusting system and method. BACKGROUND

[0002] The discharge technology of emergency light is a key technical means for emergency light to safely, stably and effectively release the electrical energy stored in the battery in emergency situations, to provide power support for emergency lighting lamps to maintain the lighting function.

[0003] Taking a lithium battery as an example, during the discharge process of the lithium battery, the voltage gradually decreases from the full charge state to the cut-off voltage. The output voltage of the lithium battery remains relatively stable during most of the discharge process, but rapidly decreases near the end of the discharge, showing a nonlinear change relationship. The output voltage of the lithium battery is detected by a voltage detection circuit, and the MCU control unit outputs a PWM driving signal with a corresponding duty cycle according to the detected voltage, and the brightness of the LED lighting unit is controlled by the PWM control switch. This method can dynamically adjust the brightness of the emergency LED, and can reduce power consumption when the battery power is insufficient, thereby prolonging the use time of the emergency light. This is particularly important in emergency situations.

[0004] However, the lithium battery will generate voltage fluctuations when discharging and not discharging, which will have a nonlinear effect on the PWM duty cycle. When the battery voltage is low, the average output voltage under the same duty cycle decreases, resulting in unexpected brightness or power output. When the load suddenly changes, the battery voltage drops suddenly, and the PWM duty cycle cannot be adjusted in time, which will cause the brightness of the emergency light to fluctuate.

[0005] In order to solve the above problems, the prior art discloses a lithium battery charging control circuit in Chinese patent CN103151824A, which solves the problem of affecting the service life of lithium battery or even causing danger due to overcharging during the charging process of lithium battery. The signal processing circuit receives the voltage signal and the terminal voltage signal in the lithium battery to output a first voltage signal. The triangular wave generating circuit generates a triangular wave of a certain frequency. The pulse width modulation circuit has a reference voltage signal, and the first voltage signal and the reference voltage signal are compared to generate a second voltage signal. The second voltage signal and the triangular wave generated by the triangular wave generating circuit are compared to generate a PWM signal. The driving circuit amplifies the PWM signal of the pulse width modulation circuit to generate a first switching signal and a second switching signal. The charging control circuit is simple and reliable, and can ensure that the lithium ion battery pack is not overcharged, thereby ensuring the service life of the battery pack.

[0006] Similarly, a lithium-ion battery switching charging circuit with announcement number CN103457320B compares the battery voltage with a reference voltage and dynamically adjusts the charging current using a triangular wave / PWM signal to achieve smooth switching between constant current charging and constant voltage charging, ensuring charging safety and extending battery life.

[0007] Similarly, a balancing charging device for series battery packs, with announcement number CN101425694A, also achieves automatic switching between constant current charging and constant voltage charging through voltage sampling, comparison, and control logic.

[0008] However, the above applications cannot solve the discharge problem in emergency scenarios, and the voltage fluctuations that occur when lithium batteries are discharging and not discharging, which will bring nonlinear effects to PWM duty cycle adjustment.

[0009] Therefore, an adaptive linear PWM duty cycle adjustment system and method are proposed to solve or alleviate the above problems. Summary of the Invention

[0010] The purpose of this invention is to address the shortcomings of existing technologies by proposing an adaptive linear PWM duty cycle adjustment system and method.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] An adaptive linear PWM duty cycle adjustment system includes a switched capacitor sampling circuit, a triangular wave generation circuit, a PWM signal generation circuit, and a battery voltage clamping circuit.

[0013] The input terminal of the battery voltage clamping circuit is connected to the battery voltage. The output terminal of the battery voltage clamping circuit is connected to the first input terminal of the switched capacitor sampling circuit. The battery voltage clamping circuit locks the battery voltage divider when the battery voltage is lower than a preset threshold. The second input terminal of the switched capacitor sampling circuit is connected to the reference source voltage. The output terminal of the switched capacitor sampling circuit is connected to the first input terminal of the PWM signal generation circuit. The switched capacitor sampling circuit is controlled by the PWM signal to synchronously acquire the battery voltage divider and the reference source voltage. The output terminal of the triangular wave generation circuit is connected to the second input terminal of the PWM signal generation circuit. The triangular wave generation circuit generates a periodically changing triangular wave signal for comparison by the PWM signal generation circuit. The PWM signal generation circuit outputs a PWM signal by comparing the magnitude of the battery voltage divider signal and the triangular wave signal.

[0014] Preferably, the switched capacitor sampling circuit comprises a battery voltage division sampling circuit and a reference source voltage sampling circuit, the input end of the battery voltage division sampling circuit is connected with the output end of the battery voltage clamping circuit, the battery voltage division sampling circuit samples the battery voltage division and outputs a battery voltage division sampling signal, the input end of the reference source voltage sampling circuit is connected with a reference source voltage, and the reference source voltage sampling circuit samples the reference source voltage and outputs a VBG sampling voltage.

[0015] Preferably, the battery voltage division sampling circuit and the reference source voltage sampling circuit are controlled to start by the PWM signal.

[0016] Preferably, the triangular wave generating circuit comprises a charge-discharge circuit, a buffer and a first comparator, the first comparator controls the on-off of the triangular wave generating circuit based on the VBG sampling voltage to generate an on-off signal, the charge-discharge circuit generates a triangular wave signal based on the on-off signal, and the buffer isolates the triangular wave signal and outputs a buffered triangular wave signal.

[0017] Preferably, the battery voltage clamping circuit comprises an amplifier and a first NMOS tube, the amplifier outputs a control signal by comparing the battery voltage with a reference voltage, and the first NMOS tube is turned on or off according to the control signal to clamp the battery voltage division.

[0018] Preferably, the PWM signal generating circuit comprises a third comparator, and the third comparator compares the size of the battery voltage division sampling signal and the triangular wave signal to generate the PWM signal.

[0019] The application also provides an adaptive linear PWM duty cycle adjustment method, which is used in cooperation with the adaptive linear PWM duty cycle adjustment system as described above, and comprises the following steps:

[0020] Step 1: collecting the battery voltage division and the reference source voltage by the switched capacitor sampling circuit, and outputting the battery voltage division sampling signal and the VBG sampling voltage;

[0021] Step 2: generating a triangular wave by the triangular wave generating circuit in response to the VBG sampling voltage;

[0022] Step 3: comparing the size of the battery voltage division sampling signal and the triangular wave by the PWM signal generating circuit in response to the battery voltage division sampling signal, and controlling the duty cycle of the PWM output;

[0023] Step 4: keeping the battery voltage division unchanged by the clamping circuit when the battery voltage reaches a preset threshold.

[0024] Preferably, the step 1 comprises:

[0025] Step 11, sampling and outputting a battery voltage division sampling signal by sampling the battery voltage division through a battery voltage division sampling circuit of the switched capacitor sampling circuit; the battery voltage division is an original battery voltage division or a battery voltage division after clamping processing;

[0026] Step 12, sampling and outputting a VBG sampling voltage by sampling a reference source voltage through a reference source voltage sampling circuit of the switched capacitor sampling circuit.

[0027] Preferably, the step 2 comprises:

[0028] Step 21, generating an on-off signal by controlling the on-off of a triangular wave generation circuit based on the VBG sampling voltage through a first comparator;

[0029] Step 22, generating a triangular wave signal based on the on-off signal through a charge-discharge circuit;

[0030] Step 23, isolating the triangular wave signal through a buffer and outputting a buffered triangular wave signal.

[0031] Preferably, the step 4 comprises:

[0032] Step 41, outputting a control signal by comparing the battery voltage with the reference voltage through an amplifier;

[0033] Step 42, turning on or off to realize the clamping of the battery voltage division through a first NMOS transistor according to the control signal.

[0034] The present application has the following beneficial effects:

[0035] The present application generates a triangular wave signal by sampling the battery voltage division and the reference voltage VBG to regulate the PWM duty cycle, and adopts a low voltage clamping technology to ensure the stability of the brightness; the battery voltage division and the reference source voltage are sampled through the switched capacitor in the PWM high / low level stage, so that the interference of voltage fluctuation on the PWM is effectively avoided. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows, and it should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and other related drawings can also be obtained by those skilled in the art without creative labor on the premise of not paying creative labor.

[0037] Figure 1 It is a wiring diagram of the switched capacitor sampling circuit in the present application;

[0038] Figure 2 It is a wiring diagram of the triangular wave generation circuit in the present application;

[0039] Figure 3 The wiring diagram of the battery voltage clamping circuit in the present application;

[0040] Figure 4 The wiring diagram of the PWM signal generating circuit in the present application;

[0041] Figure 5 The signal waveform diagram of the triangular wave generating circuit in the present application;

[0042] Figure 6 The comparative waveform diagram of the sampling circuit with and without the switch sampling in the present application;

[0043] Figure 7 The waveform diagram of the PWM signal generating circuit in the present application;

[0044] Figure 8 The flow chart of the adaptive linear PWM duty cycle adjusting method in the present application.

[0045] 1, Switched-capacitor sampling circuit; 2, Triangular wave generating circuit; 3, PWM signal generating circuit; 4, Battery voltage clamping circuit. DETAILED DESCRIPTION

[0046] In order to make the objects, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0047] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present application.

[0048] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0049] In the description of the application, it should be understood that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly understood by those skilled in the art, and are only used to facilitate the description of the application and simplify the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the application.

[0050] In addition, the terms "first", "second", "third" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0051] In the description of the application, it should be noted that unless otherwise specified and limited, the terms "set", "install", "connect", "connect" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0052] An adaptive linear PWM duty cycle regulation system, comprising a switched capacitor sampling circuit 1, a triangular wave generating circuit 2, a PWM signal generating circuit 3, and a battery voltage clamping circuit 4;

[0053] The input end of the battery voltage clamping circuit 4 is used to connect the battery voltage, the output end of the battery voltage clamping circuit 4 is connected with the first input end of the switched capacitor sampling circuit 1, the battery voltage clamping circuit 4 locks the battery voltage when the battery voltage is lower than the preset threshold, the second input end of the switched capacitor sampling circuit 1 is connected with the reference source voltage, the output end of the switched capacitor sampling circuit 1 is connected with the first input end of the PWM signal generating circuit 3, the switched capacitor sampling circuit 1 is controlled by the PWM signal to synchronously collect the battery voltage and the reference source voltage, the output end of the triangular wave generating circuit 2 is connected with the second input end of the PWM signal generating circuit 3, the triangular wave generating circuit 2 generates a periodically changing triangular wave signal for the PWM signal generating circuit 3 to compare, and the PWM signal generating circuit 3 outputs a PWM signal by comparing the size of the battery voltage signal and the triangular wave signal.

[0054] When the adaptive linear PWM duty cycle regulation system is used, the battery voltage clamping circuit 4 first divides the battery voltage, while continuously monitoring the relationship between the divided battery voltage and the reference voltage. When the battery voltage is higher than the preset threshold, only normal voltage division is performed to output a stable battery voltage division. When the battery voltage is lower than the preset threshold, the battery voltage division is kept stable by self-adjustment, avoiding abnormal subsequent regulation caused by excessively low voltage.

[0055] Subsequently, the switched capacitor sampling circuit 1 synchronously collects the battery voltage division after clamping and the reference source voltage VBAT. Through sampling logic synchronized with the PWM signal, it only samples at a specific time and keeps the sampling signal, effectively avoiding the influence of voltage fluctuations of the battery during discharge and non-discharge on sampling accuracy, ensuring that the obtained battery voltage division sampling signal and VBG sampling voltage can truly reflect the actual state.

[0056] At the same time, the triangular wave generating circuit 2 generates a periodic triangular wave signal based on the VBG sampling voltage through internal adjustment, providing a stable reference waveform for PWM duty cycle regulation.

[0057] Next, the PWM signal generating circuit 3 compares the battery voltage division sampling signal output by the switched capacitor sampling circuit 1 with the triangular wave signal generated by the triangular wave generating circuit 2 in real time, and dynamically adjusts the duty cycle of the output PWM signal according to the voltage relationship between the two. When the battery voltage division sampling signal changes with the battery voltage, the PWM duty cycle changes linearly, achieving adaptive regulation of the load.

[0058] When the battery voltage is clamped, the battery voltage division sampling signal remains stable, and the PWM duty cycle also remains constant, ensuring the basic working brightness of the load in a low voltage state.

[0059] As a result, the system successfully solves the problems of non-linear PWM duty cycle, load brightness jitter, and unstable output at low voltage caused by battery voltage fluctuations in traditional regulation methods, achieving precise and stable control of the battery discharge process.

[0060] The switched capacitor sampling circuit 1 includes a battery voltage division sampling circuit and a reference source voltage sampling circuit. The input end of the battery voltage division sampling circuit is connected to the output end of the battery voltage clamping circuit 4. The battery voltage division sampling circuit samples the battery voltage division and outputs a battery voltage division sampling signal. The input end of the reference source voltage sampling circuit is connected to the reference source voltage VBAT. The reference source voltage sampling circuit samples the reference source voltage and outputs a VBG sampling voltage. The battery voltage division sampling circuit and the reference source voltage sampling circuit are controlled to start by the PWM signal.

[0061] More specifically, as Figure 1As shown, the battery voltage sampling circuit comprises a sixth switch S6 and a second sampling capacitor C2, one end of the sixth switch S6 is connected with the output end of the battery voltage clamping circuit 4, the other end of the sixth switch S6 is connected with one end of the second sampling capacitor C2, the other end of the second sampling capacitor C2 is grounded, and the sixth switch S6 is controlled to be on or off by the PWM signal.

[0062] As shown, Figure 1 As shown, the reference source voltage sampling circuit comprises a third switch S3 and a first capacitor Csk1, one end of the third switch S3 is connected with the reference source voltage VBAT, the other end of the third switch S3 is connected with one end of the first capacitor Csk1, the other end of the first capacitor Csk1 is grounded, the third switch S3 is controlled to be on or off by the PWM signal, the voltage across the second sampling capacitor C2 is the battery voltage sampling signal VBS, and the voltage across the first capacitor Csk1 is the reference source sampling signal VBG.

[0063] When the battery voltage sampling circuit works, in order to ensure that the battery voltage changes linearly, the battery voltage at the discharging moment is collected uniformly, when the PWM signal is high, the switch is controlled to be on, the battery voltage is sampled by the voltage division, the battery voltage charges the second sampling capacitor C2 through the switch, the voltage across the second sampling capacitor C2 gradually rises until it is equal to the battery voltage, and the sampling stage ends, at this time, the second sampling capacitor C2 stores the information of the battery voltage, and the corresponding battery voltage sampling signal is obtained.

[0064] When the PWM signal is low, the switch is controlled to be off, and the voltage across the second sampling capacitor C2 remains unchanged because the charge stored in the second sampling capacitor C2 is retained, so the voltage maintained by the second sampling capacitor C2, that is, the battery voltage sampling signal, can be processed and output by the subsequent circuit.

[0065] The present application sets the battery voltage sampling circuit, only when the PWM signal is high, the sampling state and the holding state are switched by the switch and the second sampling capacitor C2, this way avoids the sampling error caused by the change of the battery voltage signal, and further prevents the nonlinear influence of the fluctuation of the battery voltage on the PWM duty ratio when discharging and not discharging.

[0066] For the reference source voltage VBAT sampling circuit, considering that a large current will be generated when the chip is discharging, which will cause the battery voltage to change suddenly, and this change will affect the reference source voltage VBAT, if the reference source voltage VBAT is collected when the battery voltage changes suddenly, the collection result will be inaccurate, therefore, the present application uses the same sampling timing to complete the collection of the reference source voltage VBAT and the battery voltage.

[0067] The collection of the reference source voltage VBAT is controlled by the PWM signal, which ensures the consistency of the reference source voltage VBAT and the battery discharging state.

[0068] The PWM signal can control whether the reference source voltage VBAT is connected, the first capacitor Csk1 is used for keeping the input voltage signal, so that the input signal of the comparator is stable, and the first capacitor Csk1 and the third switch S3 form a switch sampling circuit.

[0069] When the PWM signal is high, the third switch S3 is controlled to be closed, the reference source voltage VBAT is sampled, the voltage across the first capacitor Csk1 gradually rises until it is equal to the reference source voltage VBAT, and the sampling stage ends, at this time, the first capacitor Csk1 stores the information of the reference source voltage VBAT, obtains the corresponding sampling voltage, and the sampled reference source voltage VBAT can be kept through the first capacitor Csk1, which further avoids the nonlinear influence of the fluctuation of the battery voltage on the PWM duty cycle when discharging and not discharging.

[0070] And since the sampled battery voltage is kept by the capacitor, when the PWM signal is low, the triangular wave signal and the battery voltage can still be compared.

[0071] When the PWM signal is high, the battery voltage can be collected again, and the comparison is performed with the new battery voltage, which ensures the linear change of the comparison voltage.

[0072] At the same time, the present application can collect the reference source voltage VBAT and the battery voltage at the same time when the PWM signal is high, and also can collect at the same time when the PWM signal is low, which further ensures the consistency of the reference source voltage VBAT and the battery discharge voltage, thereby preventing abnormal fluctuation of the PWM signal and avoiding the brightness of the emergency lamp in the subsequent circuit from changing.

[0073] The triangular wave generating circuit 2 includes a charge-discharge circuit, a buffer Buffer and a first comparator CMP1, the first comparator CMP1 controls the on-off of the triangular wave generating circuit 2 based on the VBG sampling voltage, generates an on-off signal, the charge-discharge circuit generates a triangular wave signal based on the on-off signal, and the buffer Buffer isolates and outputs the buffered triangular wave signal.

[0074] More specifically, as Figure 2 and Figure 5As shown, the triangular wave generating circuit 2 comprises a buffer Buffer, an upper and lower threshold selection circuit, a first comparator CMP1, a first current source I1, a second current source I2, a fourth switch S4, a fifth switch S5, a first sampling capacitor C1, the upper and lower threshold selection circuit comprises a first resistor R1, a second resistor R2, a third resistor R3, a first switch S1, a second switch S2, the first resistor R1, the second resistor R2, and the third resistor R3 are connected in series, one end of the first resistor R1 away from the second resistor R2 is connected with the output end of the buffer Buffer, one end of the third resistor R3 away from the second resistor R2 is grounded, one end of the first switch S1 is connected with the connection node between the first resistor R1 and the second resistor R2, the other end of the first switch S1 is connected with the non-inverting input end of the first comparator CMP1, one end of the second switch S2 is connected with the connection node of the second resistor R2 and the third resistor R3, the other end of the second switch S2 is connected with the non-inverting input end of the first comparator CMP1, the first current source is connected with one end of the first sampling capacitor C1 through the fourth switch S4, the second current source is connected with one end of the first sampling capacitor C1 through the fifth switch S5, the other end of the first sampling capacitor C1 is grounded, one end of the first sampling capacitor C1 is connected with the input end of the buffer Buffer, the output end of the buffer Buffer outputs a triangular wave signal, the inverting input end of the first comparator CMP1 is used for receiving a reference source sampling signal, and the output end of the first comparator CMP1 controls the on-off of the first switch S1, the second switch S2, the fourth switch S4, and the fifth switch S5.

[0075] When the triangular wave generating circuit 2 works, the first comparator CMP1 outputs high and low levels to form the rising and falling slopes, and then generates a periodic triangular wave signal.

[0076] The two current sources can provide constant currents, the charging current is set to be equal to the discharging current, the on-off of the first switch S1 and the second switch S2 is controlled by the charging and discharging control signal, the current source connected to the circuit can be selected, and the charging and discharging capacitor is controlled to charge and discharge to generate a triangular wave signal.

[0077] Specifically, the charging and discharging capacitor and the current source form a charging and discharging circuit, in the charging phase, the voltage across the charging and discharging capacitor gradually rises to form a rising edge, in the discharging phase, the voltage across the charging and discharging capacitor gradually decreases to form a falling edge, thereby generating an initial triangular wave signal. The initial triangular wave signal is isolated by the buffer Buffer to output a buffered triangular wave signal. This way can enhance the driving ability of the signal.

[0078] The buffered triangular wave signal output by the buffer Buffer is divided by the voltage dividing circuit composed of the three resistors, and the on-off of the third switch S3 and the fourth switch S4 is also controlled by the charging and discharging control signal.

[0079] When one of the control signals is high and the other is low, the first switch S1 is closed and the second switch S2 is open, and the charging and discharging capacitor is in the discharging phase, while the third switch S3 is open and the fourth switch S4 is closed, so as to select the lower threshold voltage of the triangular wave.

[0080] Similarly, when one of the control signals is low and the other is high, the first switch S1 is open and the second switch S2 is closed, and the charging and discharging capacitor is in the charging phase, while the third switch S3 is closed and the fourth switch S4 is open, so as to select the upper threshold voltage of the triangular wave.

[0081] Here, the lower threshold voltage corresponds to the lower limit value of the triangular wave signal, and the upper threshold voltage corresponds to the upper limit value of the triangular wave signal.

[0082] The first or second divided voltage is taken as the same-phase input voltage of the first comparator CMP1, and the reference source voltage VBAT is taken as the opposite-phase input voltage of the first comparator CMP1, and the output of the charging and discharging control signal is controlled by comparing the sizes of the two voltages. When the same-phase input voltage rises to the reference source voltage VBAT, the fourth switch S4 is switched to connect the second divided voltage, and the output state of the first comparator CMP1 is flipped. When the same-phase input voltage drops to the reference source voltage VBAT, the third switch S3 is switched to connect the first divided voltage, and the output state of the first comparator CMP1 is flipped again, so as to realize the switching of the charging and discharging state of the charging and discharging capacitor.

[0083] Wherein:

[0084] Lower threshold voltage:

[0085] Upper threshold voltage:

[0086] Upper threshold voltage of triangular wave:

[0087] Lower threshold voltage of triangular wave:

[0088] Voltage difference of triangular wave:

[0089] According to the basic formula of capacitor charging , we can get:

[0090] The period of the charging phase is:

[0091] The period of the discharging phase is:

[0092] Therefore, during the charging and discharging process, due to , the capacitor The above values are brought into the period of the triangular wave: Vp1 is the voltage of the triangular wave signal, VBAT is the voltage of the reference source.

[0093] As shown in Figure 5 , SW and SWN are square wave signals for controlling the charging and discharging circuit and the switching of the upper and lower threshold voltages, whose high and low level states alternate with time; VTN and VTP are the divided voltage signals of the Vp1 signal, used to define the change range of the ROUT signal and control the switching of the capacitor charging and discharging process; when ROUT is in the rising phase, the Vp1 signal is connected to VTP through the charging threshold switching; when ROUT is in the falling phase, the Vp1 signal is connected to VTN through the discharging threshold switching; the corresponding Vp1 signal is obtained through the switching of VTN and VTP voltages.

[0094] The battery voltage clamping circuit 4 includes an amplifier AMP and a first NMOS transistor N1, the amplifier AMP outputs a control signal by comparing the battery voltage with the reference voltage, and the first NMOS transistor N1 is turned on or off according to the control signal to realize the clamping of the battery voltage division.

[0095] More specifically, as shown in Figure 3 and Figure 6 , the battery voltage clamping circuit 4 includes an amplifier AMP, a first NMOS transistor N1, and a voltage dividing network, the voltage dividing network includes a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6, the fourth resistor R4, the fifth resistor R5, and the sixth resistor R6 are connected in series, one end of the fourth resistor R4 away from the fifth resistor R5 is connected to a power supply, one end of the sixth resistor R6 away from the fifth resistor R5 is connected to ground, the non-inverting input terminal of the amplifier AMP is used to connect the reference voltage VREF, the inverting input terminal of the amplifier AMP is connected to the connection node between the fifth resistor R5 and the sixth resistor R6, the gate of the first NMOS transistor N1 is connected to the output terminal of the amplifier AMP, the drain of the first NMOS transistor N1 is connected to the connection node between the fourth resistor R4 and the fifth resistor R5, the source of the first NMOS transistor N1 is connected to ground, and the connection node between the fourth resistor R4 and the fifth resistor R5 is the clamping point and outputs the battery voltage division to the switched capacitor sampling circuit 1.

[0096] When the battery voltage clamping circuit 4 is working, the amplifier AMP has a non-inverting input terminal and an inverting input terminal, the non-inverting input terminal is connected to the reference voltage, and the inverting input terminal is connected to the voltage after the battery voltage is divided by the three voltage dividing resistors.

[0097] ​Therefore, the voltage at the voltage-dividing point B between the first and second voltage-dividing resistors is called the clamping voltage, and the voltage at the voltage-dividing point A between the second and third voltage-dividing resistors is called the feedback voltage. The voltage at the voltage-dividing point B corresponds to the battery voltage VB, and the voltage at the voltage-dividing point A is input to the inverting input terminal of the amplifier AMP.

[0098] The amplifier AMP outputs a signal to control the state of the first NMOS transistor N1 by comparing the voltages at the two input terminals. The first NMOS transistor N1 serves as a controlled switching element, and its gate is connected to the output terminal of the amplifier AMP. The first NMOS transistor N1 is turned on or off according to the high or low level of the output signal of the amplifier AMP, thereby controlling the on-off state of the circuit and the voltage transmission. The voltage-dividing network formed by the three voltage-dividing resistors divides the battery voltage, and the divided voltage is fed back to the inverting input terminal of the amplifier AMP, thereby providing a reference for voltage comparison.

[0099] In the normal working state, when the battery voltage is higher than the threshold voltage set in the discharging process, the voltage at the voltage-dividing point B is , and the voltage at the voltage-dividing point A is . At this time, the voltage at the voltage-dividing point A is still higher than the reference voltage, i.e., the voltage at the non-inverting input terminal of the amplifier AMP is greater than the voltage at the inverting input terminal, and the amplifier AMP outputs a low-level signal.

[0100] The gate of the first NMOS transistor N1 receives a low-level signal. Since the gate-source voltage needs to be greater than the working voltage for the first NMOS transistor N1 to be turned on, the gate-source voltage is small at this time, and the first NMOS transistor N1 is in the off state. After the first NMOS transistor N1 is turned off, the path from the battery voltage to the first NMOS transistor N1 is disconnected, which means that the left circuit does not work, and the voltage-dividing network is directly connected to the ground through the third voltage-dividing resistor, thereby normally dividing the voltage without clamping.

[0101] In the clamping working state, when the battery voltage is lower than the discharging threshold voltage, the voltages at the voltage-dividing points B and A are both lower than in the normal working state. At this time, the voltage at the voltage-dividing point A is lower than the reference voltage, i.e., the voltage at the non-inverting input terminal of the amplifier AMP is less than the voltage at the inverting input terminal, and the amplifier AMP outputs a high-level signal. The gate of the first NMOS transistor N1 receives a high-level signal, the gate-source voltage increases and exceeds the working voltage, and the first NMOS transistor N1 is turned on. The node between the drain and source of the first NMOS transistor N1 is connected to the voltage-dividing network, thereby forcibly raising the voltage at the voltage-dividing point B to the clamping voltage .

[0102] As shown in Figure 4 and Figure 7 , the PWM signal generation circuit 3 includes a third comparator CMP3, which compares the battery voltage sampling signal with the triangular wave signal to generate a PWM signal.

[0103] More specifically, as shown in Figure 4 and Figure 7 , the PWM signal generation circuit 3 includes a third comparator CMP3, which compares the battery voltage sampling signal with the triangular wave signal to generate a PWM signal.As shown, the PWM signal generation circuit 3 comprises a third comparator CMP3, the non-inverting input terminal of the third comparator CMP3 is used for receiving the battery voltage division sampling signal output by the switched capacitor sampling circuit 1, the inverting input terminal of the third comparator CMP3 is used for receiving the triangular wave signal output by the triangular wave generation circuit 2, and the output terminal of the third comparator CMP3 outputs the PWM signal.

[0104] It should be noted that, considering that the triangular wave signal output by the buffer Buffer has a certain deviation, therefore, in the embodiment of the present application, the third comparator CMP3 is used to compare the triangular wave signal before buffering with the battery voltage division sampling signal, so that the influence of the additional offset introduced by the buffer Buffer on the comparison result can be avoided.

[0105] When the PWM signal generation circuit 3 works, mainly through the third comparator CMP3, as shown, Figure 7 the circuit works around the real-time comparison of two key signals, and finally generates a PWM signal that can be dynamically adjusted. The two key signals are the battery voltage division sampling signal from the switched capacitor sampling circuit 1 and the triangular wave signal generated by the triangular wave generation circuit 2. The core function of the PWM signal generation circuit 3 is to compare the voltage of the two signals to determine the high and low level state of the output PWM signal, and then realize the accurate regulation of the duty cycle.

[0106] When the voltage value of the battery voltage division sampling signal decreases to be tangent to the voltage value of the triangular wave signal, the output state of the third comparator CMP3 will be reversed.

[0107] This reversal is the key node of the whole PWM signal regulation. When the voltage of the battery voltage division sampling signal is higher than the voltage of the triangular wave signal, the third comparator CMP3 outputs high level.

[0108] When the voltage of the battery voltage division sampling signal is lower than the voltage of the triangular wave signal, the third comparator CMP3 outputs low level.

[0109] Due to the periodic variation characteristic of the triangular wave signal, its voltage gradually rises from the lower threshold voltage to the upper threshold voltage, and then gradually decreases from the upper threshold voltage to the lower threshold voltage, forming a continuous and regular fluctuation process. This periodic variation enables the comparison between the triangular wave signal and the battery voltage division sampling signal to continue, and the duration of the high level and the low level of the PWM signal output by the third comparator CMP3 also dynamically changes with the voltage relationship between the two signals, finally realizing the adaptive linear regulation of the duty cycle of the PWM signal.

[0110] When the triangular wave signal rises from the lower threshold voltage to the upper threshold voltage, the voltage value gradually increases. At this time, if the voltage value of the battery voltage sampling signal is higher, then during most of the time when the triangular wave signal rises, the voltage of the battery voltage sampling signal will be higher than the voltage of the triangular wave signal, which will make the time of the third comparator CMP3 outputting high level longer, and the duty cycle of the corresponding PWM signal larger.

[0111] On the contrary, if the voltage value of the battery voltage sampling signal is lower, the triangular wave signal will exceed the voltage of the battery voltage sampling signal faster, resulting in the time of the third comparator CMP3 outputting high level shortened, and the duty cycle of the PWM signal reduced.

[0112] And when the triangular wave signal falls from the upper threshold voltage to the lower threshold voltage, the voltage value gradually decreases, at this time the comparison logic of the battery voltage sampling signal and the triangular wave signal will present complementary characteristics with the rising phase, but ultimately the duty cycle will also be adjusted through the change of the high and low level duration.

[0113] This dynamic adjustment mechanism with the voltage relationship between the two signals ensures that the duty cycle of the PWM signal can closely follow the change of the battery voltage sampling signal, realizing the core requirement of "self-adaptation".

[0114] The calculation formula of the PWM duty cycle is represented as:

[0115]

[0116] Among them, The battery voltage sampling signal is represented as, from the formula, it can be found that since the sampled battery voltage is a variable value, the PWM duty cycle can be adaptively adjusted with the battery voltage sampling signal , and if the battery voltage sampling signal is stable, then the PWM duty cycle can be maintained stable, maintaining the basic brightness of the emergency light under low voltage.

[0117] Among them, Figure 6 The contrast waveform formed by the sampling circuit using the present application and the sampling circuit without using switch sampling is presented. From the figure, it can be clearly seen that the battery voltage sampling signal obtained by the circuit without using switch sampling has obvious sawtooth fluctuation, and is also accompanied by power jitter problem.

[0118] The root cause of this phenomenon lies in the fact that when the PWM signal is high, the circuit is in a discharging state, and the large current at this time causes the battery voltage to drop; while when the PWM signal is low, the circuit is not discharging, no current flows through the battery, and the voltage remains unchanged. This difference in battery voltage between discharging and non-discharging states directly leads to abnormal PWM signal generation. In contrast, this invention uses the high level of the PWM signal as the sampling signal. This design effectively avoids the nonlinear impact of battery voltage fluctuations during discharging and non-discharging on the PWM duty cycle, ensuring the stability of the sampling signal.

[0119] Figure 7 The diagram illustrates the waveform of the PWM generation circuit in this invention. When the amplitude of the battery voltage divider sampling signal is lower than the instantaneous value of the triangular wave reference signal, the output level of the comparator will flip, and the PWM signal will switch from high level to low level.

[0120] During this process, the duty cycle of the PWM signal exhibits a negative correlation with the dynamic change in the relative amplitude of the battery voltage divider sampling signal and the triangular wave reference signal. That is, the higher the relative amplitude of the battery voltage divider sampling signal, the longer the high-level duration of the PWM signal and the larger the duty cycle; conversely, the lower the relative amplitude, the smaller the duty cycle.

[0121] When the battery voltage is clamped, the battery voltage divider sampling signal is maintained at a constant value by the preceding battery voltage clamping circuit 4. At this time, the intersection of the battery voltage divider sampling signal and the triangular wave reference signal tends to be fixed, which allows the duty cycle of the PWM signal to remain constant, thus forming a stable voltage-duty cycle correspondence. This stable correspondence ensures that the emergency light receives stable power input even when the battery is in a low voltage state, thereby maintaining basic lighting brightness and meeting the need for stable lighting in emergency scenarios.

[0122] pass Figure 6 The comparison clearly shows that the switching sampling method adopted in this invention, by using the PWM high level as the sampling timing, successfully eliminates the interference of battery voltage fluctuations in different operating states on sampling accuracy.

[0123] Combined Figure 7 The operating characteristics of the PWM generation circuit enable the entire system to dynamically and stably adjust the PWM duty cycle according to the battery status. This solves the nonlinearity problem caused by voltage fluctuations in traditional circuits and ensures the basic brightness of the emergency light at low voltage, fully demonstrating the advantages of this invention in sampling stability and adjustment reliability.

[0124] This invention also provides an adaptive linear PWM duty cycle adjustment method, such as... Figure 8As shown, for matching the adaptive linear PWM duty cycle regulation system as above, including the following steps:

[0125] Step 1, through the switched capacitor sampling circuit 1 to collect the battery voltage and the reference source voltage, output the battery voltage sampling signal and the VBG sampling voltage;

[0126] Step 11, through the battery voltage sampling circuit of the switched capacitor sampling circuit 1, the battery voltage is sampled and the battery voltage sampling signal is output; The battery voltage is the original battery voltage or the battery voltage after clamping processing;

[0127] Step 12, through the reference source voltage sampling circuit of the switched capacitor sampling circuit 1, the reference source voltage is sampled and the VBG sampling voltage is output;

[0128] More specifically,

[0129] Battery voltage sampling: through the PWM signal to control the on-off of the sixth switch S6, when the PWM signal is high, the sixth switch S6 is closed, the battery voltage charges the second sampling capacitor C2, until the voltage across the second sampling capacitor C2 is equal to the battery voltage, the battery voltage sampling signal is obtained, when the PWM signal is low, the sixth switch S6 is opened, the second sampling capacitor C2 keeps the battery voltage sampling signal unchanged;

[0130] Reference source voltage VBAT sampling: through the PWM signal to control the on-off of the third switch S3, when the PWM signal is high, the third switch S3 is closed, the reference source voltage VBAT charges the first capacitor Csk1, until the voltage across the first capacitor Csk1 is equal to VBG, when the PWM signal is low, the third switch S3 is opened, the first capacitor Csk1 keeps the sampling voltage of the reference source voltage VBAT unchanged;

[0131] Wherein, the on-off state of the sixth switch S6 and the third switch S3 is synchronously controlled by the PWM signal;

[0132] Step 2, in response to the VBG sampling voltage, a triangular wave is generated by the triangular wave generating circuit 2;

[0133] Step 21, the first comparator CMP1 controls the on-off in the triangular wave generating circuit 2 based on the VBG sampling voltage, and generates an on-off signal;

[0134] Step 22, the charge-discharge circuit generates a triangular wave signal based on the on-off signal;

[0135] Step 23, the buffer Buffer isolates the triangular wave signal, and outputs the buffered triangular wave signal;

[0136] More specifically,

[0137] Charge-discharge control: the SW signal and SWN signal output by the first comparator CMP1 control the fourth switch S4 and the fifth switch S5, when the SW signal is low and the SWN signal is high, the fifth switch S5 is closed and the fourth switch S4 is opened, the second current source discharges the first sampling capacitor C1, and the voltage across the first sampling capacitor C1 linearly decreases, when the SW signal is high and the SWN signal is low, the fourth switch S4 is closed and the fifth switch S5 is opened, the first current source charges the first sampling capacitor C1, and the voltage across the first sampling capacitor C1 linearly increases;

[0138] Threshold switching: the SW signal and SWN signal synchronously control the first switch S1 and the second switch S2, when the first sampling capacitor C1 is charged, the first switch S1 is closed and the second switch S2 is opened, the lower threshold voltage of the connection node of the first resistor R1 and the second resistor R2 is connected to the non-inverting input terminal of the first comparator CMP1, when the first sampling capacitor C1 is discharged, the second switch S2 is closed and the first switch S1 is opened, the upper threshold voltage of the connection node of the second resistor R2 and the third resistor R3 is connected to the non-inverting input terminal of the first comparator CMP1;

[0139] Triangle wave output: the non-inverting input terminal of the first comparator CMP1 is connected to the VBG sampling voltage, the SW signal and the SWN signal are flipped by comparing the size of the lower threshold value / upper threshold value and the VBG sampling voltage, and the voltage across the first sampling capacitor C1 is isolated by the buffer Buffer and then outputs the triangle wave signal;

[0140] Step 3, in response to the battery voltage sampling signal, the PWM signal generation circuit 3 compares the battery voltage sampling signal and the triangle wave, and controls the duty cycle of the PWM output;

[0141] More specifically,

[0142] Signal comparison: the battery voltage sampling signal obtained in step 1 is connected to the non-inverting input terminal of the third comparator CMP3, and the triangle wave signal generated in step 2 is connected to the inverting input terminal of the third comparator CMP3;

[0143] Duty cycle adjustment: when the battery voltage sampling signal is greater than the triangle wave signal, the third comparator CMP3 outputs high, and when the battery voltage sampling signal is less than the triangle wave signal, the third comparator CMP3 outputs low;

[0144] Linear correlation: the duty cycle D of the PWM signal is calculated according to the formula D=(battery voltage sampling signal-Vtl) / ΔV×100%, which changes linearly with the battery voltage sampling signal, where Vtl is the lower threshold of the triangle wave, and ΔV is the voltage difference of the triangle wave;

[0145] Step 4, when the battery voltage reaches the preset threshold, the battery voltage is kept constant by the battery voltage clamping circuit 4;

[0146] Step 41, the amplifier AMP outputs a control signal by comparing the battery voltage with the reference voltage;

[0147] Step 42, the first NMOS tube N1 is turned on or off according to the control signal to realize the clamping of the battery voltage;

[0148] More specifically,

[0149] Voltage division detection: the battery voltage is divided by the voltage division network composed of the fourth resistor R4, the fifth resistor R5 and the sixth resistor R6, and the voltage at the feedback point and the battery voltage at the clamping point are obtained;

[0150] Threshold judgment: the voltage at the feedback point and the reference voltage are compared by the amplifier AMP, when the battery voltage is higher than the preset threshold, the voltage at the feedback point is greater than or equal to the reference voltage, the amplifier AMP outputs low level, the first NMOS tube N1 is turned off, and the battery voltage is kept at the natural voltage, when the battery voltage is lower than the preset threshold, the voltage at the feedback point is less than the reference voltage, the amplifier AMP outputs high level, and the first NMOS tube N1 is turned on;

[0151] Voltage clamping: after the first NMOS tube N1 is turned on, the battery voltage at the clamping point is forced to keep the clamping voltage VBC=reference voltage×(1+resistance value of the fifth resistor R5 / resistance value of the sixth resistor R6), so that the battery voltage sampling signal is stable.

[0152] The adaptive linear PWM duty cycle adjustment system is used to perform the adaptive linear PWM duty cycle adjustment method.

[0153] In the discharge demand of the emergency scene, the lithium battery voltage is collected by the battery voltage sampling circuit, and the triangular wave signal is generated by the triangular wave generating circuit 2.

[0154] The battery voltage is compared with the triangular wave signal to regulate the duty cycle of the PWM output; when the voltage collected by the battery voltage sampling circuit reaches the preset threshold, the battery voltage clamping circuit 4 maintains the voltage stable.

[0155] The battery voltage sampling accuracy is optimized, which can cope with the sampling drift of the battery in the discharge and non-discharge states, and ensure the high accuracy of the discharge monitoring.

[0156] At the same time, by dynamically comparing the triangular wave signal with the battery voltage, the duty cycle of the PWM output can be automatically adjusted according to the change of the battery voltage, the intelligent adjustment of the charging current is realized, the charging efficiency is improved, and the service life of the battery is effectively prolonged, and when the battery voltage reaches the preset threshold, the battery voltage clamping circuit 4 maintains the voltage stable, which can effectively guarantee the basic brightness of the emergency light.

[0157] And the setting of the switch sampling capacitor, can be in PWM high or low level to the battery voltage and reference source voltage VBAT sampling, avoid the battery in discharge and not discharge voltage fluctuation to the PWM duty cycle caused by non-linear effect, and prevent the power supply appears fluctuation.

[0158] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An adaptive linear PWM duty cycle adjustment system, characterized in that, It includes a switched capacitor sampling circuit (1), a triangular wave generation circuit (2), a PWM signal generation circuit (3), and a battery voltage clamping circuit (4). The input terminal of the battery voltage clamping circuit (4) is used to connect to the battery voltage. The output terminal of the battery voltage clamping circuit (4) is connected to the first input terminal of the switched capacitor sampling circuit (1). The battery voltage clamping circuit (4) locks the battery voltage divider when the battery voltage is lower than a preset threshold. The second input terminal of the switched capacitor sampling circuit (1) is connected to the reference source voltage. The output terminal of the switched capacitor sampling circuit (1) is connected to the first input terminal of the PWM signal generation circuit (3). The switched capacitor sampling circuit (1) is controlled by the PWM signal to synchronously collect the battery voltage divider and the reference source voltage. The output terminal of the triangular wave generation circuit (2) is connected to the second input terminal of the PWM signal generation circuit (3). The triangular wave generation circuit (2) generates a periodically changing triangular wave signal for comparison by the PWM signal generation circuit (3). The PWM signal generation circuit (3) outputs the PWM signal by comparing the magnitude of the battery voltage divider signal and the triangular wave signal.

2. The adaptive linear PWM duty cycle adjustment system according to claim 1, characterized in that, The switched capacitor sampling circuit (1) includes a battery voltage divider sampling circuit and a reference source voltage sampling circuit. The input terminal of the battery voltage divider sampling circuit is connected to the output terminal of the battery voltage clamping circuit (4). The battery voltage divider sampling circuit samples the battery voltage and outputs the battery voltage divider sampling signal. The input terminal of the reference source voltage sampling circuit is connected to the reference source voltage. The reference source voltage sampling circuit samples the reference source voltage and outputs the VBG sampling voltage.

3. The adaptive linear PWM duty cycle adjustment system according to claim 2, characterized in that, The battery voltage divider sampling circuit and the reference source voltage sampling circuit are started by PWM signal control.

4. The adaptive linear PWM duty cycle adjustment system according to claim 1, characterized in that, The triangular wave generating circuit (2) includes a charging and discharging circuit, a buffer, and a first comparator. The first comparator controls the on / off state of the triangular wave generating circuit (2) based on the VBG sampling voltage to generate an on / off signal. The charging and discharging circuit generates a triangular wave signal based on the on / off signal. The buffer isolates the triangular wave signal and outputs the buffered triangular wave signal.

5. The adaptive linear PWM duty cycle adjustment system according to claim 1, characterized in that, The battery voltage clamping circuit (4) includes an amplifier and a first NMOS transistor. The amplifier outputs a control signal by comparing the battery voltage with a reference voltage. The first NMOS transistor is turned on or off according to the control signal to achieve battery voltage clamping.

6. The adaptive linear PWM duty cycle adjustment system according to claim 1, characterized in that, The PWM signal generation circuit (3) includes a third comparator, which compares the magnitude of the battery voltage divider sampling signal with the magnitude of the triangular wave signal to generate a PWM signal.

7. An adaptive linear PWM duty cycle adjustment method, used in conjunction with the adaptive linear PWM duty cycle adjustment system as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Collect the battery voltage divider and reference source voltage through the switched capacitor sampling circuit (1), and output the battery voltage divider sampling signal and VBG sampling voltage; Step 2: In response to the VBG sampling voltage, a triangular wave is generated by the triangular wave generation circuit (2); Step 3: In response to the battery voltage divider sampling signal, the PWM signal generation circuit (3) compares the battery voltage divider sampling signal with the magnitude of the triangular wave and controls the duty cycle of the PWM output. Step 4: When the battery voltage reaches the preset threshold, the clamping circuit keeps the battery voltage constant.

8. The adaptive linear PWM duty cycle adjustment method according to claim 7, characterized in that, Step 1 includes: Step 11: The battery voltage is sampled and the battery voltage sampling signal is output through the battery voltage divider sampling circuit of the switched capacitor sampling circuit (1); the battery voltage divider is the original battery voltage divider or the battery voltage divider after clamping. Step 12: The reference source voltage is sampled and the VBG sampling voltage is output through the reference source voltage sampling circuit of the switched capacitor sampling circuit (1).

9. The adaptive linear PWM duty cycle adjustment method according to claim 7, characterized in that, Step 2 includes: Step 21: The first comparator controls the on / off state of the triangular wave generation circuit (2) based on the VBG sampling voltage to generate an on / off signal; Step 22: The charging and discharging circuit generates a triangular wave signal based on the on / off signal; Step 23: The buffer isolates the triangular wave signal and outputs the buffered triangular wave signal.

10. The adaptive linear PWM duty cycle adjustment method according to claim 7, characterized in that, Step 4 includes: Step 41: The amplifier outputs a control signal by comparing the battery voltage with the reference voltage; Step 42: The first NMOS transistor is turned on or off according to the control signal to achieve voltage clamping of the battery.

Images