CN101610024B - Frequency generator and pulse width modulation controller with frequency dithering - Google Patents

Abstract

The invention relates to a frequency generator with frequency jitter and a pulse width modulation controller, wherein the conventional pulse width modulation controller changes the frequency of the pulse width modulation controller by an input power supply to reduce electromagnetic interference, but the method can cause uncertain range of the frequency jitter and difficulty in circuit design due to the influence of input voltage and output load. The frequency generator with frequency jitter and the pulse width modulation controller with frequency jitter of the invention utilize the signal in a fixed potential range to adjust the frequency signal of the frequency generator, thereby not only avoiding the frequency jitter range from being influenced by input voltage and output load, but also fixing the frequency jitter range in a preset percentage range no matter the operating frequency of the pulse width modulation controller, and leading the circuit setting to be simpler and more convenient.

Description

Frequency generator and pulse width modulation controller with frequency dithering

technical field

The present invention relates to a frequency generator with frequency jitter (Frequency JitterGenerator), in particular to a pulse width modulation controller which uses the frequency generator to change the operating frequency within a predetermined percentage.

Background technique

Since the power used by most electronic equipment is direct current, a power supply (or rectifier) must be provided to convert the alternating current into various direct current voltages to provide the power required by the electronic equipment. According to the different circuit structures, power supplies can be divided into two types: linear and switching power supplies. Although the circuit structure of the switching power supply is more complicated than that of the linear power supply, the pulsation is relatively large, and the electromagnetic interference is relatively large, but the advantages of the switching power supply are high conversion efficiency, low power consumption at no-load, and light weight. But overall, switching power supplies are still better than linear power supplies, so the current power supply market is dominated by switching power supplies.

Typically switching power supplies operate at high frequencies to minimize the size of the required electronic components. However, it also brings electromagnetic interference (Electromagnetic Interfrence, EMI). In addition to causing noise on the power supply and affecting other electronic equipment, electromagnetic interference will also affect adjacent communication equipment or radio and television signal transmission due to external radiation.

The traditional method of reducing electromagnetic interference is to add an EMI filter at the input end of the power supply. EMI filters are generally composed of inductors, capacitors and resistors to filter out electromagnetic interference. However, the greater the electromagnetic interference, the greater the required EMI filter, resulting in an increase in circuit cost, and the EMI filter cannot handle EMI radiation.

Please refer to Figure 1, which shows a common power supply with frequency jitter. The rectifier 10 rectifies the AC voltage 5 filtered by the EMI filter 120 to generate a rectified voltage 15 . The rectified voltage 15 is filtered by the input filter capacitor 20 and then input to the primary side coil 35 of the transformer 40 , and then output by the secondary side coil 45 . The output of the secondary coil 45 passes through the secondary rectifier 50 and the output capacitor 55 to provide an output voltage 60 at the power output terminal 65 . The pulse width modulation controller 90 receives the feedback signal of the feedback loop formed by the feedback resistor 80, the Zener diode 75 and the optocoupler 70 at the feedback pin 85, and adjusts the duty cycle of the built-in transistor switch accordingly, so as to The function of adjusting the input power of the primary side coil 35 to stabilize the output voltage 60 is achieved.

The pulse width modulation controller 90 receives the jitter current 135 input through the electromagnetic interference resistor 140 at the frequency jitter pins 125 and 130, and the jitter current 135 will change with the ripple component on the rectified voltage 15 and change the pulse width modulation control The frequency of the triangular wave signal of the frequency generator in the device 90. The triangular wave signal of the frequency generator is used as a comparison reference with the feedback signal, thus affecting the switching frequency of the transistor switch. In this way, the switching frequency of the transistor switch is expanded in a relatively large frequency bandwidth, which reduces the peak of electromagnetic interference and achieves the advantage of reducing electromagnetic interference.

However, since the ripple component will vary with the input voltage and output load, it is further difficult to select an appropriate EMI resistor 140 in practical applications. Moreover, the range (percentage) of frequency jitter will also vary with the magnitude of the input voltage, causing inconvenience and difficulty in practical use and design.

It can be seen that the above-mentioned existing pulse width modulation controller obviously still has inconvenience and defects in structure and use, and needs to be further improved urgently. In order to solve the above-mentioned problems, the relevant manufacturers have tried their best to find a solution, but no suitable design has been developed for a long time, and the general products do not have a suitable structure to solve the above-mentioned problems. This is obviously the relevant industry. urgent problem to be solved. Therefore, how to create a new type of power supply and pulse width modulation controller with frequency jitter is one of the current important research and development topics, and it has also become a goal that the industry needs to improve.

In view of the defects in the above-mentioned existing pulse width modulation controllers, the inventor actively researches and innovates based on years of rich practical experience and professional knowledge engaged in the design and manufacture of such products, and cooperates with the application of academic theories, in order to create a new type of pulse width modulation controller. The pulse width modulation controller can improve the general existing pulse width modulation controller and make it more practical. Through continuous research, design, and after repeated trial samples and improvements, the present invention with practical value is finally created.

Contents of the invention

The main purpose of the present invention is to overcome the defects of the existing pulse width modulation controller, and provide a new type of frequency generator with frequency jitter and pulse width modulation controller. The technical problem to be solved is to make it used in A signal with a fixed potential range is used to adjust the frequency signal of the frequency generator, which not only avoids the range of frequency jitter being affected by the input voltage and output load, but also regardless of the operating frequency of the pulse width modulation controller, the frequency jitter according to the present invention The range can be fixed within a predetermined percentage range, which makes circuit setting easier.

The purpose of the present invention and the solution to its technical problems are achieved by adopting the following technical solutions. According to the frequency generator with frequency jitter provided by the present invention, it includes a frequency generator and a frequency jitter controller. The frequency generator has a charging current source, a discharging current source and a capacitor, the charging current source and the discharging current source are electrically connected to the capacitor to charge and discharge it, the frequency generator receives a first reference level signal and a second reference level signal, and charge and discharge the capacitor according to the first reference level signal and the second reference level signal, so that the voltage of the capacitor is between the first reference level signal and the second reference level signal The level signal is changed to generate a frequency signal. The frequency jitter controller is coupled to the frequency generator to control the current magnitude of at least one of the charging current source and the discharging current source to vary within a predetermined range.

The purpose of the present invention and its technical problems can also be further realized by adopting the following technical measures.

The aforementioned frequency generator with frequency jitter, wherein the frequency jitter controller includes a ramp generator for generating a ramp signal to control the current magnitude of the charging current source and the discharging current source, the ramp The frequency of the signal is less than the frequency of the signal.

In the aforementioned frequency generator with frequency jitter, the frequency jitter controller further includes a voltage divider, and the ramp signal is divided by the voltage divider to control the currents of the charging current source and the discharging current source .

In the aforementioned frequency generator with frequency jitter, the charging current source is a voltage-to-current converter for converting the level of the ramp signal into a charging current.

In the aforementioned frequency generator with frequency jitter, the discharge current source is a voltage-to-current converter for converting the level of the ramp signal into a discharge current.

The purpose of the present invention and the solution to its technical problem also adopt the following technical solutions to achieve. The pulse width modulation controller with frequency dithering provided by the present invention includes a feedback processor, a frequency dithering controller, a frequency generator and a pulse width modulation signal generator. The feedback processor generates a feedback processing signal according to a detection signal representing a load state. The frequency jitter controller generates a ramp signal, wherein the level of the ramp signal changes within a predetermined interval. The frequency generator is used to generate a frequency signal, and the frequency of the frequency signal changes within a predetermined frequency interval according to the ramp signal. The pulse width modulation signal generator generates a switch control signal according to the feedback processing signal and the frequency signal to control switching of at least one semiconductor switch.

The purpose of the present invention and its technical problems can also be further realized by adopting the following technical measures.

The aforementioned pulse width modulation controller with frequency jitter, wherein the frequency jitter controller includes a ramp generator for generating the ramp signal, the frequency of the ramp signal is lower than the frequency of the frequency signal.

The aforementioned pulse width modulation controller with frequency jitter, wherein the frequency generator has a charging current source, a discharging current source and a capacitor, the charging current source and the discharging current source are electrically connected to the capacitor, so as to To charge and discharge it, the frequency generator receives a first reference level signal and a second reference level signal, and charges and discharges the capacitor according to the first reference level signal and the second reference level signal, so that The voltage of the capacitor varies between the first reference level signal and the second reference level signal to generate the frequency signal.

In the aforementioned pulse width modulation controller with frequency jitter, at least one of the charging current source and the discharging current source varies within a predetermined range according to the ramp signal.

The aforementioned pulse width modulation controller with frequency jitter, wherein the frequency jitter controller further includes a voltage divider, and the ramp signal is divided by the voltage divider to control the charging current source and the discharging current source Current size.

In the aforementioned pulse width modulation controller with frequency jitter, the charging current source is a voltage-to-current converter for converting the level of the ramp signal into a charging current.

In the aforementioned pulse width modulation controller with frequency jitter, the discharge current source is a voltage-to-current converter for converting the level of the ramp signal into a discharge current.

Compared with the prior art, the present invention has obvious advantages and beneficial effects. By means of the above technical solution, the frequency generator and pulse width modulation controller with frequency jittering of the present invention have at least the following advantages and beneficial effects:

The frequency generator with frequency jitter and the pulse width modulation controller with frequency jitter of the present invention use a signal in a predetermined fixed potential range to adjust the frequency signal of the frequency generator, which not only avoids the range of frequency jitter being affected by the input voltage and In addition to the influence of the output load, regardless of the operating frequency of the PWM controller, the range of the frequency jitter according to the present invention can be fixed within a predetermined percentage range, which makes circuit setting easier. Moreover, the range of its frequency jitter can be adjusted by the ratio of the frequency jitter resistor JR and the frequency setting resistor RT, which not only makes the adjustment more precise, but also can be adjusted corresponding to different circuits, further expanding its applicable range.

In summary, the frequency generator with frequency jitter and the pulse width modulation controller with frequency jitter of the present invention use a signal in a fixed potential range to adjust the frequency signal of the frequency generator, not only avoiding the range of frequency jitter In addition to being affected by the input voltage and output load, and regardless of the operating frequency of the PWM controller, the range of the frequency jitter according to the present invention can be fixed within a predetermined percentage range, making circuit setting easier. The present invention has the above-mentioned many advantages and practical value, it has great improvement no matter in product structure or function, has remarkable progress in technology, and has produced easy-to-use and practical effect, and compared with existing pulse width modulation The controller has enhanced outstanding functions, so it is more suitable for practical use, and has wide application value in the industry. It is a novel, progressive and practical new design.

The above description is only an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the description, and in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable , the following preferred embodiments are specifically cited below, and are described in detail as follows in conjunction with the accompanying drawings.

Description of drawings

Figure 1 shows a common power supply with frequency jitter.

FIG. 2 is a schematic circuit diagram of a frequency generator with frequency dithering according to a preferred embodiment of the present invention.

FIG. 3 is a schematic circuit diagram of the charging current source in the embodiment of FIG. 2 .

FIG. 4 is a timing diagram of the level of the ramp signal Ramp, the magnitude of the charging current I, and the pulse signal Pulse.

FIG. 5 is a schematic circuit diagram of a PWM controller with frequency dithering according to a preferred embodiment of the present invention.

5: AC voltage 10: Rectifier

15: rectified voltage 20: input filter capacitor

35: Primary coil 40: Transformer

45: Secondary side coil 50: Secondary side rectifier

55: output capacitance 60: output voltage

65: Power output terminal 70: Optocoupler

75: Zener diode 80: Feedback resistor

85: Feedback pin 90: Pulse width modulation controller

120: EMI filter 125: Frequency jitter pin

130: frequency jitter pin 135: jitter current

140: EMI resistance 210: Frequency jitter controller

212: ramp generator 214: voltage divider

216: ramp signal 220: frequency generator

222: Charging current source 224: Discharging current source

226: capacitor 230: first comparator

232: The second comparator 238: The third comparator

228: The fourth comparator 234: The first NAND gate

236: The second NAND gate 240: The first switch

242: Second switch 244: Frequency signal

250: Error signal amplifier 252: Transistor switch

260: Current Mirror 310: Feedback Processor

320: Pulse Width Modulation Signal Generator 322: Pulse Width Modulation Comparator

324: SR flip-flop 330: Frequency jitter controller

340: frequency generator 350: semiconductor switch

JR: frequency jitter resistor RT: frequency setting resistor

Ramp: ramp signal Vref1: first reference level signal

Vref2: Second reference level signal Vref3: Third reference level signal

I: Current I1: Current

Pulse: pulse signal R: resistance

FB: Detection signal Vref: Reference voltage signal

Prot: Protection signal Max-Duty: Maximum duty cycle signal

Detailed ways

In order to further explain the technical means and effects that the present invention adopts to achieve the predetermined invention purpose, the following in conjunction with the accompanying drawings and preferred embodiments, the specific frequency generator and pulse width modulation controller with frequency jitter proposed according to the present invention Embodiments, structures, features and effects thereof are described in detail below.

The aforementioned and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of preferred embodiments with reference to the drawings. For convenience of description, in the following embodiments, the same elements are denoted by the same numbers.

Please refer to FIG. 2 , which is a circuit diagram of a frequency generator with frequency dithering according to a preferred embodiment of the present invention. A frequency generator includes a frequency jitter controller 210 and a frequency generator 220 , wherein the frequency jitter controller 210 is coupled to the frequency generator 220 . The frequency jitter controller 210 includes a ramp generator 212 for generating a ramp signal 216; the frequency jitter controller 210 further includes a voltage divider 214, the voltage divider 214 is composed of a frequency jitter resistor JR and a frequency setting resistor RT to divide the ramp signal 216 to output the ramp signal Ramp. The frequency generator 220 has a charging current source 222 , a discharging current source 224 and a capacitor 226 , the charging current source 222 and the discharging current source 224 are electrically connected to the capacitor 226 to charge and discharge it. The frequency generator 220 receives a first reference level signal Vref1 and a second reference level signal Vref2, and charges and discharges the capacitor 226 according to the first reference level signal Vref1 and the second reference level signal Vref2, so that the capacitor 226 The voltage varies between the first reference level signal and the second reference level signal to generate a frequency signal 244 . In this embodiment, the charging current source 222 receives the divided ramp signal Ramp, and changes the magnitude of the current I generated by it according to the ramp signal Ramp, so that the magnitude of the current I changes within a predetermined range. In this way, regardless of the frequency The frequency of the generator 220 is high or low, and the frequency jitter range of the frequency generator 220 is changed within a predetermined percentage. In practice, the charge current source 222 and/or the discharge current source 224 may receive the divided ramp signal Ramp, and vary the magnitude of the generated current according to the ramp signal 216 . Here, the frequency of the ramp signal Ramp is lower than the operating frequency of the frequency generator 220 .

The frequency generator 220 further includes a first comparator 230, a second comparator 232, a first NAND gate 234, a second NAND gate 236, a third comparator 238, a first switch 240, A second switch 242 and a fourth comparator 228 . The first comparator 230 compares the frequency signal 244 with the first reference level signal Vref1 and outputs a comparison result signal, and the second comparator 232 compares the frequency signal 244 with the second reference level signal Vref2 and outputs a comparison result signal. The first NAND gate 234 receives the output of the first comparator 230 and the second NAND gate 236 for NAND operation, and the second NAND gate 236 receives the output of the second comparator 232 and the first NAND gate 234 for Perform AND operation. The third comparator 238 receives the outputs of the first NAND gate 234 and the second NAND gate 236 to control switching of the first switch 240 and the second switch 242 . When the level of the frequency signal 244 rises higher than the first reference level signal Vref1 , the first switch 240 is turned off and the second switch is turned on, so that the capacitor 226 starts to discharge. When the level of the frequency signal 244 drops below the second reference level signal Vref2 , the first switch 240 is turned on and the second switch is turned off, so that the capacitor 226 starts to charge. The frequency signal 244 of the ramp signal is generated by repeating this cycle. The fourth comparator 228 compares the frequency signal 244 of the ramp signal and a third reference level signal Vref3 to convert and generate the pulse signal Pulse.

Next, please refer to FIG. 3 , which is a schematic circuit diagram of the charging current source in the embodiment of FIG. 2 . The charging current source 222 is a voltage-to-current converter that converts a charging current I according to the level of the ramp signal Ramp, and includes an error amplifier 250 , a transistor switch 252 , a resistor R and a current mirror 260 . Wherein, the error signal amplifier 250 and the transistor switch 252 form a voltage follower, so that the potential at the connection point between the transistor switch 252 and the resistor R is equal to the level of the ramp signal Ramp, so that the current I1 flowing through the resistor R (I1=V /R, V is the level of the ramp signal Ramp) is mirrored by the current mirror 260 to become the charging current I. Similarly, the discharge current source 224 can also use the same circuit structure to achieve the function of changing the discharge current according to the level of the ramp signal Ramp.

Referring to FIG. 4 , it is a timing diagram of the level of the ramp signal Ramp, the magnitude of the charging current I and the pulse signal Pulse. When the level of the ramp signal Ramp rises, the charging current I increases accordingly, increasing the frequency of the pulse signal Pulse; conversely, when the level of the ramp signal Ramp decreases, the charging current I decreases accordingly, making the pulse signal Pulse frequency is reduced.

Referring next to FIG. 5 , it is a schematic circuit diagram of a PWM controller with frequency dithering according to a preferred embodiment of the present invention. The PWM controller includes a feedback processor 310 , a frequency dithering controller 330 , a frequency generator 340 and a PWM signal generator 320 . The feedback processor 310 includes an error amplification signal generator for generating a feedback processing signal according to a detection signal FB representing a load state and a reference voltage signal Vref. The frequency dithering controller 330 generates a ramp signal, and the level of the ramp signal changes within a predetermined interval. The frequency generator 340 is coupled to the frequency jitter controller 330 for generating a frequency signal, wherein the frequency of the frequency signal varies within a predetermined frequency range according to the ramp signal. The pulse width modulation signal generator 320 generates a switch control signal according to the feedback processing signal and the frequency signal to control switching of a semiconductor switch 350 . The PWM signal generator 320 includes a PWM comparator 322 , an SR flip-flop 324 and an AND gate 326 . The PWM comparator 322 receives the feedback processing signal and the triangular wave signal generated by the frequency generator 340 , and outputs the comparison result to the R terminal of the SR flip-flop 324 . The S terminal of the SR flip-flop 324 receives the pulse signal generated by the frequency generator 340 and outputs a switch control signal at the output terminal Q. The AND gate 326 receives the switch control signal, a protection signal Prot, and a maximum duty ratio signal Max-Duty to control switching of the semiconductor switch 350 .

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this field Those skilled in the art, without departing from the scope of the technical solution of the present invention, can use the technical content disclosed above to make some changes or modify equivalent embodiments with equivalent changes, but all the content that does not depart from the technical solution of the present invention, according to the present invention Any simple modifications, equivalent changes and modifications made to the above embodiments by the technical essence still belong to the scope of the technical solution of the present invention.

Claims (10)

1. the frequency generator of a tool frequency jitter is characterized in that it comprises:

One frequency generator; Have a charging current source, a discharging current source and an electric capacity, this charging current source and this discharging current source electrically connect this electric capacity, so that it is discharged and recharged; This frequency generator receives one first reference level signal and one second reference level signal; And according to this first reference level signal and this second reference level signal to this capacitor charge and discharge, the voltage of this electric capacity is changed, to produce a frequency signal between first reference level signal and this second reference level signal; And

One frequency jitter controller; Couple this frequency generator; In a preset range, make the wobble variation of electric current with the electric current of the one of which at least of controlling this charging current source and this discharging current source, wherein, described frequency jitter controller comprises: a ramp generator; In order to produce a ramp signal to control the size of current in this charging current source and this discharging current source, the frequency of this ramp signal is less than the frequency of this frequency signal; And a voltage divider, this ramp signal is controlled the size of current in this charging current source and this discharging current source after this voltage divider dividing potential drop.

2. the frequency generator of tool frequency jitter according to claim 1 is characterized in that wherein said charging current source is that a voltage changes current converter, becomes a charging current with the level conversion according to this ramp signal.

3. the frequency generator of tool frequency jitter according to claim 1 is characterized in that wherein said discharging current source is that a voltage changes current converter, becomes a discharging current with the level conversion according to this ramp signal.

4. the PDM keyer of a tool frequency jitter is characterized in that it comprises:

One feedback processor produces a feedback processing signal according to a detection signal of representing load condition;

One frequency jitter controller produces a ramp signal, and the level of this ramp signal changes in a predetermined interval;

One frequency generator, in order to produce a frequency signal, the frequency of this frequency signal changes in a preset frequency interval according to this ramp signal; And

One pulse-duration modulation signal generator produces a switch controlling signal according to this feedback processing signal and this frequency signal, to control the switching of semiconductor switch at least;

Wherein this frequency jitter controller comprises a voltage divider, and this ramp signal changes in a preset frequency interval through the frequency of this frequency signal of control after this voltage divider dividing potential drop.

5. the PDM keyer of tool frequency jitter according to claim 4 is characterized in that wherein said frequency jitter controller comprises a ramp generator, and in order to produce this ramp signal, the frequency of this ramp signal is less than the frequency of this frequency signal.

6. the PDM keyer of tool frequency jitter according to claim 5; It is characterized in that wherein said frequency generator; Have a charging current source, a discharging current source and an electric capacity, this charging current source and this discharging current source electrically connect this electric capacity, so that it is discharged and recharged; This frequency generator receives one first reference level signal and one second reference level signal; And according to this first reference level signal and this second reference level signal to this capacitor charge and discharge, the voltage of this electric capacity is changed, to produce this frequency signal between this first reference level signal and this second reference level signal.

7. the PDM keyer of tool frequency jitter according to claim 6 is characterized in that the one of which at least in wherein said charging current source and this discharging current source changes in a preset range according to this ramp signal.

8. the PDM keyer of tool frequency jitter according to claim 7 is characterized in that wherein said ramp signal, and the electric current of controlling the one of which at least in this charging current source and this discharging current source is made the wobble variation of electric current in a preset range.

9. according to the PDM keyer of claim 6 or 8 described tool frequency jitters, it is characterized in that wherein said charging current source is that a voltage changes current converter, becomes a charging current with the level conversion according to this ramp signal.

10. according to the PDM keyer of claim 6 or 8 described tool frequency jitters, it is characterized in that wherein said discharging current source is that a voltage changes current converter, becomes a discharging current with the level conversion according to this ramp signal.

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