CN114257223A - Pulse width modulation signal generating device - Google Patents
Pulse width modulation signal generating device Download PDFInfo
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- CN114257223A CN114257223A CN202011011275.7A CN202011011275A CN114257223A CN 114257223 A CN114257223 A CN 114257223A CN 202011011275 A CN202011011275 A CN 202011011275A CN 114257223 A CN114257223 A CN 114257223A
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K7/00—Modulating pulses with a continuously-variable modulating signal
- H03K7/08—Duration or width modulation ; Duty cycle modulation
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Abstract
The invention discloses a pulse width modulation signal generating device, which comprises a first constant current source, a triangular wave signal generator and a pulse width modulation signal converter. The first constant current source comprises a plurality of resistors and a first operational amplifier, and the first constant current source generates a first constant current. The triangular wave signal generator is coupled with the first constant current source, receives the first constant current and generates a triangular wave signal according to the first constant current. The pulse width modulation signal converter is coupled with the triangular wave signal generator, receives the triangular wave signal and a dimming signal and compares the triangular wave signal with the dimming signal to generate an accurate pulse width modulation signal.
Description
Technical Field
The present invention relates to a signal generating device, and more particularly, to a pulse width modulation signal generating device.
Background
In the application of light-emitting diode (LED) dimming, a Pulse Width Modulation (PWM) signal is often used to perform dimming, i.e., the dc voltage at the power output terminal of the LED is chopped into a PWM waveform for output, and the duty cycle of the output voltage and current is changed to change the brightness of the LED. The PWM signal generating circuit commonly used at present is realized by utilizing a single chip, so that the PWM signal generating circuit has the advantages of simple circuit, convenient modulation and high single chip cost, and is not beneficial to saving the cost and carrying out mass production.
Secondly, the method is also realized by an independent circuit, but the independent circuit has large error, is greatly influenced by environment and has poor batch consistency, for example, a Zhongxing communication CN201610263832.1 PWM generating circuit is a typical PWM generating circuit formed by independent elements, but the method has obvious defects, for example, an adjustable resistor and a transistor in a constant current source circuit belong to elements with large error, and the dispersibility of the resistance value of the adjustable resistor can cause the independent adjustment of the adjustable resistor when leaving a factory, thereby influencing the production efficiency; the transistor is a triode which is greatly affected by temperature; the current of the whole constant current source circuit has great dispersion, which causes errors.
Therefore, the present invention provides a pwm signal generating apparatus to solve the above-mentioned problems in the prior art.
Disclosure of Invention
The present invention provides a pulse width modulation signal generating apparatus which overcomes the high cost brought by using a single chip and the problem that the frequency and the period of a pulse width modulation signal have high dispersion because of using a transistor, an adjustable resistor and other elements with high dispersion in a constant current source, so that the finally generated pulse width modulation signal becomes very accurate with an error from the expected frequency and period within a range of 3%.
The invention provides a pulse width modulation signal generating device, which comprises a first constant current source, a triangular wave signal generator and a pulse width modulation signal converter. The first constant current source comprises a plurality of resistors and a first operational amplifier, wherein the first constant current source is used for generating a first constant current. The triangular wave signal generator is coupled to the first constant current source, wherein the triangular wave signal generator is used for receiving the first constant current and generating a triangular wave signal according to the first constant current. The pulse width modulation signal converter is coupled to the triangular wave signal generator, wherein the pulse width modulation signal converter is used for receiving the triangular wave signal and a dimming signal and comparing the triangular wave signal with the dimming signal to generate a pulse width modulation signal.
In an embodiment of the present invention, all the resistors include a first resistor, a second resistor, a third resistor, a fourth resistor and a fifth resistor. The first resistor is coupled between the positive input terminal of the first operational amplifier and a high voltage terminal. The second resistor is coupled to the negative input terminal and a low voltage terminal of the first operational amplifier. One end of the third resistor is coupled to the negative input terminal of the first operational amplifier and the second resistor, and the other end is coupled to the output terminal of the first operational amplifier. One end of the fourth resistor is coupled to the positive input end of the first operational amplifier and the first resistor, and the other end is coupled to the triangular wave signal generator. One end of the fifth resistor is coupled to the output end of the first operational amplifier and the third resistor, and the other end is coupled to the fourth resistor and the triangular wave signal generator. The resistance value of the first resistor divided by the resistance value of the fourth resistor is equal to the resistance value of the second resistor divided by the resistance value of the third resistor. The first operational amplifier is used for receiving a high voltage of the high voltage end and a low voltage of the low voltage end through the first resistor and the fourth resistor respectively, and generating a first constant current through the fifth resistor by utilizing the high voltage, the low voltage, the third resistor and the fourth resistor.
In an embodiment of the present invention, the triangular wave signal generator includes an energy storage, a voltage divider, a second operational amplifier and an electronic switch. The energy storage is coupled between a low voltage end and the first constant current source, wherein the energy storage is used for receiving the first constant current to store energy. The voltage divider is coupled to the energy storage in parallel, wherein the voltage divider is used for receiving energy and generating a driving voltage according to the energy. The negative input terminal of the second operational amplifier is coupled to a high voltage terminal, and the positive input terminal is coupled to the voltage divider, wherein the second operational amplifier is used for receiving the driving voltage and the high voltage of the high voltage terminal, and generating a control voltage accordingly. The electronic switch is coupled to the output end of the second operational amplifier, the low voltage end and the energy storage device, wherein the electronic switch is used for receiving the control voltage and releasing or storing energy in the energy storage device according to the control voltage, and further generating a triangular wave signal on the energy storage device.
In one embodiment of the present invention, the electronic switch includes a transistor switch.
In one embodiment of the present invention, the pwm signal converter includes an operational amplifier.
In an embodiment of the invention, the pwm signal generating apparatus further includes a filter coupled to the pwm signal converter, the filter is configured to receive the dimming signal and filter the dimming signal to generate an analog voltage, and the pwm signal converter is configured to receive the analog voltage and compare the triangular wave signal with the analog voltage to generate the pwm signal.
In one embodiment of the present invention, the filter is a low pass filter.
In an embodiment of the invention, the pwm signal generating apparatus further includes a second constant current source and an input resistor. The second constant current source is used for generating a second constant current, the input resistor is coupled between a low voltage end and the second constant current source, the second constant current source and the input resistor are coupled with the pulse width modulation signal converter, and the second constant current passes through the input resistor to adjust the dimming signal.
In an embodiment of the present invention, the second constant current source includes a plurality of resistors and an operational amplifier.
In an embodiment of the invention, the input resistor is an adjustable resistor.
Based on the above, the embodiment of the present invention utilizes the advantage of the batch consistency and the temperature stability of the operational amplifier in the constant current source over the transistor, so as to establish the negative feedback loop by cooperating with the plurality of resistors to enhance the stability, accuracy, performance and practical value of the pwm signal generating apparatus.
Drawings
FIG. 1 is a circuit diagram of a PWM signal generating apparatus according to a first embodiment of the present invention.
FIG. 2 is a circuit diagram of a PWM signal generating apparatus according to a second embodiment of the present invention.
FIG. 3 is a circuit diagram of a third embodiment of a PWM signal generating apparatus according to the present invention.
FIG. 4 is a circuit diagram of a fourth embodiment of a PWM signal generating apparatus according to the present invention.
FIG. 5 is a circuit diagram of a fifth embodiment of a PWM signal generating apparatus according to the present invention.
Fig. 6 is a circuit diagram of an embodiment of a filter according to the present invention.
Fig. 7 is a circuit diagram of a second constant current source according to an embodiment of the invention.
List of reference numerals: 10-a pulse width modulation signal generating means; 12-a first constant current source; 121-a first operational amplifier; 122 — a first resistance; 123-a second resistance; 124-third resistance; 125-fourth resistance; 126-fifth resistance; 14-a triangular wave signal generator; 141-an energy storage; 1411-a first capacitance; 142-a voltage divider; 1421 — first divider resistor; 1422 — second divider resistor; 1423 — second capacitance; 143-a second operational amplifier; 144-an electronic switch; 1441-transistor switch; 1442 — switching resistance; 16-a pulse width modulation signal converter; 18-a filter; 181-filter resistance; 182-a filter capacitor; 20-a second constant current source; 201-a third operational amplifier; 202-sixth resistance; 203-seventh resistance; 204-eighth resistance; 205-ninth resistance; 206-tenth resistance; 22-input resistance; v1 — high voltage; v2 — high voltage; v3 — high voltage; i1-first constant current; i2-second constant current; dim-dimming signal; a T-triangular wave signal; a P-pulse width modulation signal; a-an analog voltage; d-a drive voltage; c-control voltage.
Detailed Description
Embodiments of the invention will be further illustrated by the following description in conjunction with the related drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the description to refer to the same or like parts. In the drawings, the shape and thickness may be exaggerated for simplicity and convenience. It is to be understood that elements not specifically shown in the drawings or described in the specification are of a type well known to those of ordinary skill in the art. Many variations and modifications may be made by one of ordinary skill in the art in light of the teachings of the present invention.
Certain terms are used throughout the description and claims to refer to particular components. However, those of ordinary skill in the art will appreciate that the various elements may be referred to by different names. The specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. Also, the term "coupled" as used herein includes any direct or indirect connection. Therefore, if a first element is coupled to a second element, the first element may be directly connected to the second element through an electrical connection or a signal connection such as wireless transmission or optical transmission, or may be indirectly connected to the second element through another element or a connection means.
The description below of "one embodiment" or "an embodiment" refers to a particular element, structure, or feature associated with at least one embodiment. Thus, appearances of the phrases "one embodiment" or "an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Unless specifically stated otherwise, conditional expressions or words, such as "can", "possibly" (result) "," perhaps (light) ", or" may ", are generally intended to convey that embodiments of the present invention have, but may also be interpreted as having, features, elements, or steps that may not be required. In other embodiments, these features, elements, or steps may not be required.
FIG. 1 is a circuit diagram of a PWM signal generating apparatus according to a first embodiment of the present invention. Referring to fig. 1, a first embodiment of a pwm signal generating apparatus 10 according to the present invention is described. The first embodiment of the PWM signal generating apparatus 10 comprises a first constant current source 12, a triangular wave signal generator 14 and a PWM signal converter 16. The triangular wave signal generator 14 is coupled to the first constant current source 12, and the pulse width modulation signal converter 16 is coupled to the triangular wave signal generator 14. The first constant current source 12 must include a plurality of resistors and a first operational amplifier 121. Since the first operational amplifier 121 has better batch consistency and temperature stability than a transistor, the first operational amplifier 121 can be matched with a plurality of resistors to establish a negative feedback loop without an external transistor, so as to improve the stability and accuracy of the first constant current source 12 and improve the stability, accuracy, performance and practical value of the pwm signal generating apparatus 10.
The first constant current source 12 generates a first constant current I1, and the triangular signal generator 14 receives the first constant current I1 and generates a triangular signal T according to the first constant current I1, wherein the triangular signal T may also be a sawtooth signal. The pwm signal converter 16 receives the triangular wave signal T and a dimming signal Dim, and compares the triangular wave signal T and the dimming signal Dim to generate a pwm signal P. For example, the dimming signal Dim can be an analog voltage of 0-10 volts or a pulse width modulation voltage, but the invention is not limited thereto. In order to generate the pwm signal P, in some embodiments of the present invention, the pwm signal converter 16 may include an operational amplifier, a positive input terminal of the operational amplifier of the pwm signal converter 16 receives the dimming signal Dim, and a negative input terminal thereof is coupled to the triangular wave signal generator 14 and receives the triangular wave signal T. The operational amplifier of the PWM signal converter 16 will also be used in the following embodiments, but the present invention is not limited to such a PWM signal converter 16.
In some embodiments of the present invention, the plurality of resistors of the first constant current source 12 include a first resistor 122, a second resistor 123, a third resistor 124, a fourth resistor 125 and a fifth resistor 126, but the present invention is not limited thereto. The first resistor 122 is coupled between the positive input terminal of the first operational amplifier 121 and a high voltage terminal, which is referred to as a first high voltage terminal. The second resistor 123 is coupled to the negative input terminal of the first operational amplifier 121 and a low voltage terminal, such as a ground terminal. One end of the third resistor 124 is coupled to the negative input terminal of the first operational amplifier 121 and the second resistor 123, and the other end is coupled to the output terminal of the first operational amplifier 121. One end of the fourth resistor 125 is coupled to the positive input end of the first operational amplifier 121 and the first resistor 122, and the other end is coupled to the triangular wave signal generator 14. One end of the fifth resistor 126 is coupled to the output end of the first operational amplifier 121 and the third resistor 124, and the other end is coupled to the fourth resistor 125 and the triangular wave signal generator 14. The first operational amplifier 121 receives the high voltage V1 at the first high voltage end and the low voltage at the low voltage end through the first resistor 122 and the fourth resistor 125, respectively, and generates the first constant current I1 through the fifth resistor 126 by using the high voltage V1, the low voltage, the third resistor 124 and the fourth resistor 125. Since the resistance R1 of the first resistor 122 divided by the resistance R4 of the fourth resistor 125 is equal to the resistance R2 of the second resistor 123 divided by the resistance R3 of the third resistor 124, R2/(R2+ R3) ═ R1/(R1+ R4), so that the precision influence of the resistors is negligible. In other words, when the voltage difference between the two ends of the fifth resistor 126 changes, the voltages at the positive input end and the negative input end of the first operational amplifier 121 also change, so that the first constant current I1 passing through the fifth resistor 126 is constant. In addition, the first operational amplifier 121, the third resistor 124 and the fourth resistor 125 form a negative feedback loop to ensure the good performance and stability of the first constant current source 12. The first constant current source 12 overcomes the high cost due to the use of a single chip and the problem that the frequency and the period of the pulse width modulation signal have high dispersion due to the use of a transistor, an adjustable resistor, and other components having high dispersion in the constant current source, so that the finally generated pulse width modulation signal P becomes very accurate with an error of 3% from the expected frequency and period.
FIG. 2 is a circuit diagram of a PWM signal generating apparatus according to a second embodiment of the present invention. Referring to fig. 2, a second embodiment of the pwm signal generating apparatus 10 according to the present invention will be described. The second embodiment differs from the first embodiment in that the second embodiment may further comprise a filter 18, such as a low pass filter. The filter 18 is coupled to the pwm signal converter 16. For example, if the pwm signal converter 16 is implemented as an operational amplifier, the filter 18 is coupled to a positive input terminal of the operational amplifier. The filter 18 receives the dimming signal Dim and filters the dimming signal Dim to generate an analog voltage a. In some embodiments of the present invention, if the filter 18 is a low-pass filter, the frequency of the dimming signal Dim can be limited to be below 100 khz to prevent the dimming signal Dim from passing through the filter 18. The pwm signal converter 16 receives the analog voltage a and compares the triangular wave signal T with the analog voltage a to generate the pwm signal P.
FIG. 3 is a circuit diagram of a third embodiment of a PWM signal generating apparatus according to the present invention. Referring to fig. 3, a third embodiment of the pwm signal generating apparatus 10 according to the present invention is described. The difference between the third embodiment and the first embodiment is that the third embodiment further includes a second constant current source 20 and an input resistor 22. The second constant current source 20 generates a second constant current I2. The input resistor 22 is coupled between the low voltage terminal and the second constant current source 20, and the second constant current source 20 and the input resistor 22 are coupled to the pwm signal converter 16, for example, if the pwm signal converter 16 is implemented as an operational amplifier, the second constant current source 20 and the input resistor 22 are coupled to the positive input terminal of the operational amplifier. The second constant current I2 passes through the input resistor 22 to adjust the dimming signal Dim, and the second constant current I2 is limited to microampere (μ a) level, so that the dimming signal Dim is not interfered. In addition, since the second constant current I2 can also establish a voltage difference across the input resistor 22 through the input resistor 22, when the dimming signal Dim disappears, the voltage difference can also be used as another dimming signal to be sent to the pwm signal converter 16. In some embodiments of the present invention, the input resistor 22 may be an adjustable resistor, thereby adjusting the dimming signal sent to the pwm signal converter 16. When the filter 18 of fig. 2 is applied to the structure of fig. 3, the input terminal of the filter 18 can be coupled to the second constant current source 20 and the input resistor 22 simultaneously, so as to filter the second constant current I2 to establish a voltage difference across the input resistor 22.
FIG. 4 is a circuit diagram of a fourth embodiment of a PWM signal generating apparatus according to the present invention. Referring to fig. 4, a fourth embodiment of the pwm signal generating apparatus 10 according to the present invention will be described. The triangle wave signal generator 14 of the fourth embodiment may include an energy storage 141, a voltage divider 142, a second operational amplifier 143, and an electronic switch 144. The triangular wave generator 14 of FIG. 4 can also be applied to the architecture of FIG. 3 and other embodiments, however, the present invention is not limited to this triangular wave generator 14. The energy storage 141 is coupled between the low voltage terminal and the first constant current source 12. For example, the energy storage 141 is coupled to the fourth resistor 125 and the fifth resistor 126 of fig. 1. The voltage divider 142 is coupled in parallel to the energy storage 141. The negative input terminal of the second operational amplifier 143 is coupled to a high voltage terminal, and the positive input terminal is coupled to the voltage divider 142, wherein the high voltage terminal is referred to as a second high voltage terminal. The electronic switch 144 is coupled to the output terminal of the second operational amplifier 143, the low voltage terminal and the energy storage 141.
The energy storage 141 receives the first constant current I1 to store energy, the voltage divider 142 receives the energy and generates a driving voltage D accordingly, and the second operational amplifier 143 receives the driving voltage D and the high voltage V2 at the second high voltage end and generates a control voltage C accordingly. The electronic switch 144 receives the control voltage C and accordingly releases or stores energy in the energy storage 141, thereby generating a triangular wave signal T on the energy storage 141. Specifically, the driving voltage D is higher as the energy stored in the energy storage 141 is more. When the driving voltage D is greater than the high voltage V2, the control voltage C turns on the electronic switch 144 to release the energy stored in the energy storage 141. The driving voltage D is lower as the energy stored in the energy storage 141 is more released. When the driving voltage D is less than the high voltage V2, the control voltage C turns off the electronic switch 144 to store energy in the energy storage 141, so that the energy stored in the energy storage 141 is continuously increased. Based on the above-mentioned periodic operation, the energy stored in the energy storage 141 forms a periodic triangular wave signal T. The magnitude of the first constant current I1 influences the frequency of the triangular wave signal T.
FIG. 5 is a circuit diagram of a fourth embodiment of a PWM signal generating apparatus according to the present invention. Referring to fig. 5, a fifth embodiment of the pwm signal generating apparatus 10 according to the present invention will be described. The triangular wave generator 14 of FIG. 5 can also be applied to the architecture of FIG. 4 and other embodiments, however, the present invention is not limited to this triangular wave generator 14. In the fifth embodiment, the energy storage 141 is implemented by a first capacitor 1411, the first capacitor 1411 is coupled between the low voltage terminal and the first constant current source 12, and the frequency of the triangular wave signal T can be changed by changing the capacitance of the first capacitor 1411. The voltage divider 142 includes a first voltage dividing resistor 1421, a second voltage dividing resistor 1422 and a second capacitor 1423. The first voltage divider resistor 1421 has one end coupled to the first capacitor 1411 and the other end coupled to the positive input of the second operational amplifier 143. The second voltage-dividing resistor 1422 has one end coupled to the positive input terminal of the second operational amplifier 143 and the other end coupled to the low voltage terminal. The second capacitor 1423 is coupled to the second voltage divider 1422 in parallel. The first divider resistor 1421, the second divider resistor 1422, and the second capacitor 1423 generate a driving voltage D between the first divider resistor 1421 and the second divider resistor 1422 by using the energy stored in the energy storage 141. Changing the resistance of the first voltage dividing resistor 1421 and the second voltage dividing resistor 1422 can change the amplitude of the triangular signal T. The electronic switch 144 includes a transistor switch 1441 and a switching resistor 1442, wherein the transistor switch 1441 is coupled between the low voltage terminal and the first capacitor 1411, and the switching resistor 14421 is coupled between the low voltage terminal and the control terminal of the transistor switch 1441. The transistor switch 1441 receives the control voltage C and releases or stores energy in the first capacitor 1411, thereby generating a triangular wave signal T on the first capacitor 1411.
Fig. 6 is a circuit diagram of an embodiment of a filter according to the present invention. The filter of fig. 6 can be applied in the architecture of fig. 2 or other embodiments, but the invention is not limited to this filter. The filter 18 may include a filter resistor 181 and a filter capacitor 182, wherein one end of the filter resistor 181 receives the dimming signal Dim and the other end is coupled to the pwm signal converter 16. The filter capacitor 182 has one end coupled to the filter resistor 181 and the other end coupled to the low voltage end. If the pwm signal converter 16 is implemented as an operational amplifier, the positive input terminal of the operational amplifier is coupled to the filter resistor 181 and the filter capacitor 182. The filter resistor 181 and the filter capacitor 182 receive the dimming signal Dim and convert the dimming signal Dim into an analog voltage a.
Fig. 7 is a circuit diagram of a second constant current source according to an embodiment of the invention. The second constant current source of FIG. 7 can be applied to the architecture of FIG. 3 or other embodiments, but the invention is not limited to this second constant current source. The second constant current source 20 includes a third operational amplifier 201, a sixth resistor 202, a seventh resistor 203, an eighth resistor 204, a ninth resistor 205 and a tenth resistor 206. Since the third operational amplifier 201 is superior to a transistor in terms of batch uniformity and temperature stability, the third operational amplifier 201 also does not need an external transistor. The sixth resistor 202 is coupled between the positive input terminal of the third operational amplifier 201 and a high voltage terminal, which is referred to as the third high voltage terminal. The seventh resistor 203 is coupled to the negative input terminal and the low voltage terminal of the third operational amplifier 201. One end of the eighth resistor 204 is coupled to the negative input terminal of the third operational amplifier 201 and the seventh resistor 203, and the other end is coupled to the output terminal of the third operational amplifier 201. One end of the ninth resistor 205 is coupled to the positive input end of the third operational amplifier 201 and the sixth resistor 202, and the other end is coupled to the pwm signal converter 16 and the input resistor 22. One end of the tenth resistor 206 is coupled to the output end of the third operational amplifier 201 and the eighth resistor 204, and the other end is coupled to the ninth resistor 205, the pwm signal converter 16 and the input resistor 22. The third operational amplifier 201 receives the high voltage V3 at the third high voltage end and the low voltage at the low voltage end through the sixth resistor 202 and the ninth resistor 205, respectively, and generates the second constant current I2 through the tenth resistor 206 by using the high voltage V3, the low voltage, the eighth resistor 204 and the ninth resistor 205. Since the resistance R6 of the sixth resistor 202 divided by the resistance R9 of the ninth resistor 205 is equal to the resistance R7 of the seventh resistor 203 divided by the resistance R8 of the eighth resistor 204, R7/(R7+ R8) ═ R6/(R6+ R9), so that the precision influence of the resistors is negligible. In other words, when the voltage difference between the two ends of the tenth resistor 206 changes, the voltages at the positive input terminal and the negative input terminal of the third operational amplifier 201 also change, so that the second constant current I2 passing through the tenth resistor 206 is not changed. In addition, the third operational amplifier 201, the eighth resistor 204 and the ninth resistor 205 form a negative feedback loop to ensure the good performance and stability of the second constant current source 20. When the filter 18 of fig. 2 is applied to the architecture of fig. 7, the input terminal of the filter 18 can be coupled to the ninth resistor 205 and the tenth resistor 206 simultaneously. The second constant current source 20 can also overcome the high cost caused by using a single chip, and overcome the problem that the frequency and the period of the pwm signal have high dispersion caused by using the components with high dispersion such as transistors and adjustable resistors in the constant current source, so that the finally generated pwm signal P becomes very accurate, and the error from the expected frequency and period is within 3%.
In summary, the above embodiments utilize the batch consistency and temperature stability of the operational amplifier in the constant current source to be superior to those of the transistor, so as to cooperate with a plurality of resistors to establish a negative feedback loop to enhance the stability, precision, performance and practical value of the pwm signal generating apparatus.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, so that equivalent variations and modifications in the shape, structure, characteristics and spirit of the present invention as described in the claims should be included in the claims of the present invention.
Claims (10)
1. A pulse width modulation signal generating apparatus, comprising:
a first constant current source including a plurality of resistors and a first operational amplifier, wherein the first constant current source is used for generating a first constant current;
a triangular wave signal generator coupled to the first constant current source, wherein the triangular wave signal generator is configured to receive the first constant current and generate a triangular wave signal according to the first constant current; and
the pulse width modulation signal converter is coupled to the triangular wave signal generator, and is configured to receive the triangular wave signal and a dimming signal and compare the triangular wave signal with the dimming signal to generate a pulse width modulation signal.
2. The pwm signal generating apparatus according to claim 1, wherein the plurality of resistors includes:
a first resistor coupled between the positive input terminal of the first operational amplifier and a high voltage terminal;
a second resistor coupled to the negative input terminal and a low voltage terminal of the first operational amplifier;
a third resistor, one end of which is coupled to the negative input terminal of the first operational amplifier and the second resistor, and the other end of which is coupled to the output terminal of the first operational amplifier;
a fourth resistor, one end of which is coupled to the positive input end of the first operational amplifier and the first resistor, and the other end of which is coupled to the triangular wave signal generator; and
a fifth resistor, one end of which is coupled to the output end of the first operational amplifier and the third resistor, and the other end of which is coupled to the fourth resistor and the triangular wave signal generator, wherein a resistance value of the first resistor divided by a resistance value of the fourth resistor is equal to a resistance value of the second resistor divided by a resistance value of the third resistor, and the first operational amplifier is configured to receive a high voltage at the high voltage end and a low voltage at the low voltage end through the first resistor and the fourth resistor, respectively, and generate the first constant current through the fifth resistor by using the high voltage, the low voltage, the third resistor and the fourth resistor.
3. The pwm signal generating apparatus according to claim 1, wherein the triangular wave signal generator includes:
an energy storage device coupled between a low voltage terminal and the first constant current source, wherein the energy storage device is configured to receive the first constant current to store energy;
a voltage divider coupled in parallel to the energy storage device, wherein the voltage divider is used for receiving the energy and generating a driving voltage accordingly;
a second operational amplifier having a negative input terminal coupled to a high voltage terminal and a positive input terminal coupled to the voltage divider, wherein the second operational amplifier is configured to receive the driving voltage and a high voltage of the high voltage terminal and generate a control voltage accordingly; and
and an electronic switch coupled to the output terminal of the second operational amplifier, the low voltage terminal and the energy storage device, wherein the electronic switch is configured to receive the control voltage, and accordingly release the energy or store the energy in the energy storage device, thereby generating the triangular wave signal on the energy storage device.
4. The pwm signal generating apparatus according to claim 3, wherein the electronic switch comprises a transistor switch.
5. The pwm signal generating apparatus according to claim 1, wherein the pwm signal converter includes an operational amplifier.
6. The pwm signal generating apparatus according to claim 1, further comprising a filter coupled to the pwm signal converter, the filter being configured to receive the dimming signal and filter the dimming signal to generate an analog voltage, the pwm signal converter being configured to receive the analog voltage and compare the triangular wave signal with the analog voltage to generate the pwm signal.
7. The pwm signal generating apparatus according to claim 6, wherein the filter is a low-pass filter.
8. The pwm signal generating apparatus according to claim 1, further comprising:
a second constant current source for generating a second constant current; and
an input resistor coupled between a low voltage terminal and the second constant current source, wherein the second constant current source and the input resistor are coupled to the pwm signal converter, and the second constant current passes through the input resistor to adjust the dimming signal.
9. The apparatus according to claim 8, wherein the second constant current source comprises a plurality of resistors and an operational amplifier.
10. The pwm signal generating apparatus according to claim 8, wherein the input resistor is an adjustable resistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011011275.7A CN114257223A (en) | 2020-09-23 | 2020-09-23 | Pulse width modulation signal generating device |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011011275.7A CN114257223A (en) | 2020-09-23 | 2020-09-23 | Pulse width modulation signal generating device |
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| CN114257223A true CN114257223A (en) | 2022-03-29 |
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| CN202011011275.7A Pending CN114257223A (en) | 2020-09-23 | 2020-09-23 | Pulse width modulation signal generating device |
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