CN102307044A - Switching power supply PWM (pulse width modulation) controller with variable frequencies - Google Patents

Switching power supply PWM (pulse width modulation) controller with variable frequencies Download PDF

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CN102307044A
CN102307044A CN201110271345A CN201110271345A CN102307044A CN 102307044 A CN102307044 A CN 102307044A CN 201110271345 A CN201110271345 A CN 201110271345A CN 201110271345 A CN201110271345 A CN 201110271345A CN 102307044 A CN102307044 A CN 102307044A
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resistor
capacitor
transistor
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power supply
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CN102307044B (en
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胡杰
王骞
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Shenzhen Academy of Aerospace Technology
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Abstract

本发明适用于电子电路领域,提供了一种频率可变的开关电源脉冲宽度调制控制器,包括:锯齿波发生电路,频率控制电路以及PWM发生器,所述PWM发生器的输出端与所述频率控制电路的输入端相连,所述频率控制电路的输出端与所述锯齿波发生器的输入端相连,所述锯齿波发生器的输出端与所述PWM发生器的输入端相连。利用脉冲宽度调制信号的占空比值作为其频率的控制信号,提取PWM信号的直流分量,来控制锯齿波发生电路,实现振荡频率的变化,达到PWM信号频率的变化。这样,就可以根据开关电源的输入、输出条件自动改变脉冲宽度调制信号的频率,优化不同工况下的电源转换效率,同时可解决占空比非常大时脉冲变压器驱动不可靠的问题。

The present invention is applicable to the field of electronic circuits, and provides a frequency-variable switching power supply pulse width modulation controller, including: a sawtooth wave generating circuit, a frequency control circuit and a PWM generator, and the output terminal of the PWM generator is connected to the The input end of the frequency control circuit is connected, the output end of the frequency control circuit is connected with the input end of the sawtooth wave generator, and the output end of the sawtooth wave generator is connected with the input end of the PWM generator. Using the duty cycle value of the pulse width modulation signal as the control signal of its frequency, the DC component of the PWM signal is extracted to control the sawtooth wave generating circuit to realize the change of the oscillation frequency and the change of the frequency of the PWM signal. In this way, the frequency of the pulse width modulation signal can be automatically changed according to the input and output conditions of the switching power supply, and the power conversion efficiency under different working conditions can be optimized. At the same time, the problem of unreliable driving of the pulse transformer when the duty cycle is very large can be solved.

Description

一种频率可变的开关电源脉冲宽度调制控制器A Pulse Width Modulation Controller of Switching Power Supply with Variable Frequency

技术领域 technical field

本发明属于电子电路领域,尤其涉及一种频率可变的开关电源脉冲宽度调制控制器。 The invention belongs to the field of electronic circuits, in particular to a frequency-variable switching power supply pulse width modulation controller.

背景技术 Background technique

开关电源中,磁性元件的大小主要由开关频率和输入、输出条件决定,对于输入或输出电压变化范围很宽的电源,其电感的设计通常以最严酷的条件下不饱和为依据,而在输入输出条件宽松,即输入输出相差很小时,电感的设计裕度就很大,造成体积和效率的不均衡状态。通过采用开关频率变化的开关电源脉宽调制控制方法可以选用感值更优的电感,提高功率密度和电源效率。 In switching power supplies, the size of magnetic components is mainly determined by the switching frequency and input and output conditions. For power supplies with a wide range of input or output voltages, the design of the inductance is usually based on unsaturation under the most severe conditions. The output conditions are loose, that is, when the difference between input and output is small, the design margin of the inductor is very large, resulting in an unbalanced state of volume and efficiency. The inductance with better inductance value can be selected by adopting the pulse width modulation control method of switching power supply with switching frequency change, and the power density and power supply efficiency can be improved.

对于输入、输出电压范围宽的隔离型拓扑,如正激拓扑,随着输入、输出电压的变化,当占空比较大时,变压器的激磁电流也较大,为了防止饱和,变压器的原边电感量和磁芯大小均需较大;而当占空比减小时,同样的电感量和磁芯大小,变压器难以饱和,此时适当可以降低开关频率,以实现效率上的提升。 For isolated topologies with wide input and output voltage ranges, such as forward topology, as the input and output voltages change, when the duty ratio is large, the excitation current of the transformer is also large. In order to prevent saturation, the primary inductance of the transformer Both the inductance and the size of the magnetic core need to be large; and when the duty cycle is reduced, the transformer is difficult to saturate with the same inductance and magnetic core size. At this time, the switching frequency can be appropriately reduced to achieve an increase in efficiency.

对于非隔离型升压拓扑,如BOOST拓扑,当输出电压较高,占空比较大时,电感电流的纹波也较大,为了满足指标要求,电感的设计往往以此时的纹波系数为参考,当输出电压变低,占空比减小时,电感电流纹波相应减小,但只需满足同样纹波系数,便可达到指标要求,故可降低开关频率以实现效率的优化。 For non-isolated boost topology, such as BOOST topology, when the output voltage is high and the duty cycle is large, the ripple of the inductor current is also large. In order to meet the requirements of the index, the design of the inductor is often based on the ripple coefficient at this time. For reference, when the output voltage becomes lower and the duty cycle decreases, the inductor current ripple decreases accordingly, but only the same ripple coefficient is required to meet the target requirements, so the switching frequency can be reduced to optimize efficiency.

对于非隔离型降压拓扑也如此,如BUCK拓扑,只是其开关频率的变化趋势应为随着占空比的增大而减小。 The same is true for the non-isolated step-down topology, such as the BUCK topology, except that the switching frequency should decrease with the increase of the duty cycle.

发明内容 Contents of the invention

为了解决上述技术问题,本发明实施例的目的在于提供一种频率可变的开关电源脉冲宽度调制控制器。 In order to solve the above-mentioned technical problems, the purpose of the embodiments of the present invention is to provide a frequency-variable switching power supply pulse width modulation controller.

本发明实施例是这样实现的,一种频率可变的开关电源脉冲宽度调制控制器,所述控制器包括: The embodiment of the present invention is achieved in this way, a frequency variable switching power supply pulse width modulation controller, the controller includes:

一个频率随控制电压增大而增大或降低的锯齿波发生电路,一个频率控制电路以及一个PWM发生器, A sawtooth wave generating circuit whose frequency increases or decreases as the control voltage increases, a frequency control circuit and a PWM generator,

    所述PWM发生器的输出端与所述频率控制电路的输入端相连,所述频率控制电路的输出端与所述锯齿波发生器的输入端相连,所述锯齿波发生器的输出端与所述PWM发生器的输入端相连。 The output end of the PWM generator is connected to the input end of the frequency control circuit, the output end of the frequency control circuit is connected to the input end of the sawtooth wave generator, and the output end of the sawtooth wave generator is connected to the input end of the sawtooth wave generator. connected to the input of the PWM generator.

进一步地,所述控制器还包括: Further, the controller also includes:

与所述PWM发生器的输入端相连的误差放大器。 An error amplifier connected to the input of the PWM generator.

进一步地,所述锯齿波发生电路包括: Further, the sawtooth wave generating circuit includes:

定时器、电容C1003、电源VCC、电阻R1001、电阻R1002、电阻R1003、电容C1001以及PNP三极管Q1001, Timer, capacitor C1003, power supply VCC, resistor R1001, resistor R1002, resistor R1003, capacitor C1001 and PNP transistor Q1001,

所述电阻R1001和电阻R1002串联,三极管Q1001的基极连接到R1001和R1002的串联点,电阻R1001的另一端接频率控制信号1007,Q1001的发射极接电阻R1002,R1002的另一端接固定电源电压,Q1001的集电极接电容C1001,所述定时器的高触发端、低触发端和放电端接到一起,同时接到电容C1001的正端,所述电压控制端接电容C1003的正端,清零端接电源电压。 The resistor R1001 is connected in series with the resistor R1002, the base of the triode Q1001 is connected to the series connection point of R1001 and R1002, the other end of the resistor R1001 is connected to the frequency control signal 1007, the emitter of Q1001 is connected to the resistor R1002, and the other end of R1002 is connected to a fixed power supply voltage , the collector of Q1001 is connected to capacitor C1001, the high trigger terminal, low trigger terminal and discharge terminal of the timer are connected together, and at the same time connected to the positive terminal of capacitor C1001, the voltage control terminal is connected to the positive terminal of capacitor C1003, clear Zero terminal is connected to supply voltage.

进一步地,所述锯齿波发生电路1200包括: Further, the sawtooth wave generating circuit 1200 includes:

定时器、电容C1203、电源VCC、电阻R1201、电阻R1202、电阻R1203、电容C1201以及PNP三极管Q1201, Timer, capacitor C1203, power supply VCC, resistor R1201, resistor R1202, resistor R1203, capacitor C1201 and PNP transistor Q1201,

所述电阻R1201和电阻R1203串联,三极管Q1201的基极连接到R1201和R1203的串联点,电阻R1201的另一端接定时器,Q1201的发射极接电阻R1202,R1202的另一端接频率控制电路,Q1201的集电极接电容C1201,所述定时器的高触发端、低触发端和放电端接到一起,同时接到电容C1201的正端,所述电压控制端接电容C1203的正端,清零端接电源电压。 The resistor R1201 and the resistor R1203 are connected in series, the base of the triode Q1201 is connected to the series connection point of R1201 and R1203, the other end of the resistor R1201 is connected to the timer, the emitter of Q1201 is connected to the resistor R1202, and the other end of R1202 is connected to the frequency control circuit, Q1201 The collector of the timer is connected to the capacitor C1201, the high trigger terminal, the low trigger terminal and the discharge terminal of the timer are connected together, and at the same time connected to the positive terminal of the capacitor C1201, the voltage control terminal is connected to the positive terminal of the capacitor C1203, and the reset terminal Connect to the supply voltage.

进一步地,所述频率控制电路包括:电阻R1006、电阻R1004、电阻R1005、电容C1002和运算放大器U1001, Further, the frequency control circuit includes: a resistor R1006, a resistor R1004, a resistor R1005, a capacitor C1002 and an operational amplifier U1001,

电阻R1006和电容C1002组成RC滤波电路,提取PWM信号的占空比值,并且,所述电阻R1006分别与电容C1002的一端、运算放大器U1001的同相输入端相连,所述电容C1002的另一端接地; The resistor R1006 and the capacitor C1002 form an RC filter circuit to extract the duty cycle value of the PWM signal, and the resistor R1006 is respectively connected to one end of the capacitor C1002 and the non-inverting input end of the operational amplifier U1001, and the other end of the capacitor C1002 is grounded;

电阻R1004、电阻R1005和运算放大器U1001构成同相放大器,对频率控制信号进行调理,并且所述电阻R1004、电阻R1005的一端均连接至运算放大器U1001的反相输入端,所述电阻R1004的另一端接运算放大器U1001的输出端,所述电阻R1005的另一端接地。 Resistor R1004, resistor R1005 and operational amplifier U1001 form a non-inverting amplifier to adjust the frequency control signal, and one end of the resistor R1004 and resistor R1005 is connected to the inverting input terminal of the operational amplifier U1001, and the other end of the resistor R1004 is connected to The output end of the operational amplifier U1001, the other end of the resistor R1005 is grounded.

进一步地,所述误差放大器包括:运算放大器1005和外围补偿电路。 Further, the error amplifier includes: an operational amplifier 1005 and a peripheral compensation circuit.

进一步地,所述锯齿波发生电路包括:电阻R301、电阻R302、电阻R303、电容C301、电容C302、三极管Q301、三极管Q302,定时器以及对上述元件进行供电的电源VCC, Further, the sawtooth wave generating circuit includes: a resistor R301, a resistor R302, a resistor R303, a capacitor C301, a capacitor C302, a transistor Q301, a transistor Q302, a timer, and a power supply VCC for supplying power to the above components,

所述电阻R301一端连接到三极管Q301的射极,另一端连接到电阻R303的一端,所述电阻R303的另一端连接到三极管Q301的集电极,所述三极管Q301的基极连接三极管Q302的基极,所述三极管Q302的集电极分别连接电容C301的一端以及定时器,所述定时器还连接了电容C302。 One end of the resistor R301 is connected to the emitter of the transistor Q301, the other end is connected to one end of the resistor R303, the other end of the resistor R303 is connected to the collector of the transistor Q301, and the base of the transistor Q301 is connected to the base of the transistor Q302 , the collector of the triode Q302 is respectively connected to one end of the capacitor C301 and the timer, and the timer is also connected to the capacitor C302.

进一步地,所述锯齿波发生电路包括:电阻R501、电阻R502、电阻R503、电容C501、电容C502、三极管Q501、三极管Q502、定时器以及对上述元件供电的电源VCC, Further, the sawtooth wave generating circuit includes: a resistor R501, a resistor R502, a resistor R503, a capacitor C501, a capacitor C502, a transistor Q501, a transistor Q502, a timer, and a power supply VCC for supplying power to the above components,

所述三极管Q501的射极与电阻R501相连,所述三极管Q501的集电极与电容C501相连,所述三极管Q501的基极连接三极管Q502的基极,所述三极管Q502的集电极连接电阻R503,所述三极管Q502的射极连接电阻R502的一端,所述电阻R502、三极管Q501的集电极均与定时器连接,所述定时器还连接了电容C502。 The emitter of the triode Q501 is connected to the resistor R501, the collector of the triode Q501 is connected to the capacitor C501, the base of the triode Q501 is connected to the base of the triode Q502, and the collector of the triode Q502 is connected to the resistor R503. The emitter of the triode Q502 is connected to one end of the resistor R502, the resistor R502 and the collector of the triode Q501 are both connected to the timer, and the timer is also connected to the capacitor C502.

进一步地,所述锯齿波发生电路包括:电容C901、电阻R901、电阻R902、电阻R903、电阻R904、三极管Q901、三极管Q902以及比较器U901, Further, the sawtooth wave generating circuit includes: capacitor C901, resistor R901, resistor R902, resistor R903, resistor R904, transistor Q901, transistor Q902 and comparator U901,

所述三极管Q901的射极与电阻R901相连,所述三极管Q901的集电极与电容C901相连,所述三极管Q901的基极连接于电阻R902与电阻R903之间,所述三极管Q902的集电极连接至三极管Q901的集电极,所述三极管Q902的射极连接电容C901的另一端,所述电阻R902、三极管Q901的集电极均与定时器连接,所述定时器还连接了电容C902。 The emitter of the transistor Q901 is connected to the resistor R901, the collector of the transistor Q901 is connected to the capacitor C901, the base of the transistor Q901 is connected between the resistor R902 and the resistor R903, and the collector of the transistor Q902 is connected to The collector of the transistor Q901 and the emitter of the transistor Q902 are connected to the other end of the capacitor C901, the resistor R902 and the collector of the transistor Q901 are both connected to the timer, and the timer is also connected to the capacitor C902.

在本发明的实施例中,利用脉冲宽度调制信号的占空比值作为其频率的控制信号,提取PWM信号的直流分量,表示占空比的大小,来控制锯齿波发生电路,实现振荡频率的变化,达到PWM信号频率的变化。这样,就可以根据开关电源的输入、输出条件自动改变脉冲宽度调制信号的频率,优化不同工况下的电源转换效率,同时可解决占空比非常大时脉冲变压器驱动不可靠的问题。 In the embodiment of the present invention, the duty cycle value of the pulse width modulation signal is used as the control signal of its frequency, and the DC component of the PWM signal is extracted to represent the size of the duty cycle to control the sawtooth wave generating circuit to realize the change of the oscillation frequency , to achieve the change of PWM signal frequency. In this way, the frequency of the pulse width modulation signal can be automatically changed according to the input and output conditions of the switching power supply, and the power conversion efficiency under different working conditions can be optimized. At the same time, the problem of unreliable driving of the pulse transformer when the duty cycle is very large can be solved.

附图说明 Description of drawings

图1是本发明实施例提供的频率自动变化的开关电源脉冲宽度调制方法的控制原理; Fig. 1 is the control principle of the switching power supply pulse width modulation method with automatic frequency change provided by the embodiment of the present invention;

图2是本发明实施例提供的开关频率可自动调整的脉冲宽度调制控制方法的实现示意框图; Fig. 2 is a schematic block diagram of a pulse width modulation control method with an automatically adjustable switching frequency provided by an embodiment of the present invention;

图3是本发明第一实施例提供的振荡频率随控制电压的增大而降低的锯齿波发生器的电路结构图; Fig. 3 is a circuit structure diagram of a sawtooth wave generator whose oscillation frequency decreases as the control voltage increases according to the first embodiment of the present invention;

图4是图3所示锯齿波发生器电路的仿真波形图; Fig. 4 is the emulation waveform diagram of sawtooth wave generator circuit shown in Fig. 3;

图5为本发明第二实施例提供的振荡频率随控制电压的减小而降低的锯齿波发生器的电路结构图; FIG. 5 is a circuit structure diagram of a sawtooth wave generator whose oscillation frequency decreases as the control voltage decreases according to the second embodiment of the present invention;

图6是图5所示锯齿波发生器电路的仿真波形图; Fig. 6 is the emulation waveform diagram of sawtooth wave generator circuit shown in Fig. 5;

图7是图3所示的振荡频率随控制电压增大而降低的锯齿波发生器的简化实现形式; Fig. 7 is the simplified implementation form of the sawtooth wave generator that the oscillation frequency shown in Fig. 3 decreases as the control voltage increases;

图8是图5所示的振荡频率随控制电压减小而降低的锯齿波发生器的简化实现形式; Fig. 8 is a simplified implementation form of the sawtooth wave generator whose oscillation frequency shown in Fig. 5 decreases with the decrease of the control voltage;

图9是本发明第三实施例提供的锯齿波发生器的结构原理图; Fig. 9 is a schematic diagram of the structure of the sawtooth wave generator provided by the third embodiment of the present invention;

图10是开关频率随占空比增大而减小的开关电源脉冲宽度调制控制方法的具体实现电路; Fig. 10 is a specific realization circuit of the switching power supply pulse width modulation control method in which the switching frequency decreases as the duty ratio increases;

图11是图10所述开关电源脉冲宽度调制控制器的输出波形图; Fig. 11 is an output waveform diagram of the switching power supply pulse width modulation controller described in Fig. 10;

图12是开关频率随占空比减小而减小的开关电源脉冲宽度调制方法的具体实现电路; Fig. 12 is the specific implementation circuit of the pulse width modulation method of the switching power supply in which the switching frequency decreases with the decrease of the duty cycle;

图13是图12所述开关电源脉冲宽度调制控制器的输出波形图。 FIG. 13 is an output waveform diagram of the pulse width modulation controller of the switching power supply shown in FIG. 12 .

具体实施方式 Detailed ways

为了使本发明的目的、技术方案及优点更加清楚明白,以下结合附图及实施例,对本发明进行进一步详细说明。应当理解,此处所描述的具体实施例仅仅用以解释本发明,并不用于限定本发明。 In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

本发明涉及一种开关电源脉冲宽度调制控制方法及其实现方式,其可根据输入、输出条件自动改变脉冲宽度调制信号的频率,优化不同工况下的电源转换效率,同时可解决占空比非常大时脉冲变压器驱动不可靠的问题。本发明利用脉冲宽度调制信号的占空比值作为其频率的控制信号,提取PWM信号的直流分量,表示占空比的大小,来控制锯齿波发生电路,实现振荡频率的变化,达到PWM信号频率的变化。 The invention relates to a switching power supply pulse width modulation control method and its implementation, which can automatically change the frequency of the pulse width modulation signal according to the input and output conditions, optimize the power conversion efficiency under different working conditions, and at the same time solve the problem of extremely high duty cycle. The problem of unreliable driving of large pulse transformers. The present invention uses the duty cycle value of the pulse width modulation signal as its frequency control signal, extracts the DC component of the PWM signal, represents the size of the duty cycle, controls the sawtooth wave generating circuit, realizes the change of the oscillation frequency, and reaches the frequency of the PWM signal. Variety.

本发明涉及到一种开关频率可自动调整的脉冲宽度调制控制方法及其实现方式,改方法从控制器输出的PWM信号中提取占空比信息,根据占空比的大小控制锯齿波发生器实现频率的增加或降低。 The invention relates to a pulse width modulation control method with automatic switching frequency adjustment and its implementation. The modified method extracts duty cycle information from the PWM signal output by the controller, and controls the sawtooth wave generator according to the duty cycle to realize increase or decrease in frequency.

图1示出了频率自动变化的开关电源脉冲宽度调制方法的控制原理, Figure 1 shows the control principle of the switching power supply pulse width modulation method with automatic frequency change,

PWM发生器的输出端与频率控制电路相连,所述频率控制电路的输出端与锯齿波发生器相连,所述锯齿波发生器的输出端与所述PWM发生器相连。 The output end of the PWM generator is connected to the frequency control circuit, the output end of the frequency control circuit is connected to the sawtooth wave generator, and the output end of the sawtooth wave generator is connected to the PWM generator.

PWM发生器输出PWM信号,频率控制电路从PWM信号中提取占空比的大小,输出频率控制信号给所述锯齿波发生电路,从而控制锯齿波发生电路的锯齿波频率,从而PWM发生器输出的PWM信号频率相应改变。 The PWM generator outputs the PWM signal, and the frequency control circuit extracts the size of the duty ratio from the PWM signal, and outputs the frequency control signal to the sawtooth wave generating circuit, thereby controlling the sawtooth wave frequency of the sawtooth wave generating circuit, so that the PWM generator outputs The PWM signal frequency changes accordingly.

图2示出了开关频率可自动调整的脉冲宽度调制控制方法的实现示意框图, Fig. 2 shows a schematic block diagram of a pulse width modulation control method whose switching frequency can be automatically adjusted,

201为锯齿波发生器,其频率可根据控制信号改变,202为误差放大器,对电源的误差信号进行运算,实现闭环稳定,203为PWM发生器,其将误差放大器的输出信号和锯齿波信号进行比较,产生脉宽调制信号,通过驱动电路205控制开关电源中开关管的导通和关闭。204为电压-频率控制电路的示意图,其根据PWM信号的占空比大小,产生锯齿波发生器的控制信号,实现锯齿波频率的增大和减小。 201 is a sawtooth wave generator, its frequency can be changed according to the control signal, 202 is an error amplifier, which performs calculations on the error signal of the power supply, and realizes closed-loop stability, and 203 is a PWM generator, which converts the output signal of the error amplifier and the sawtooth wave signal In comparison, a pulse width modulation signal is generated, and the drive circuit 205 controls the switching on and off of the switching tube in the switching power supply. 204 is a schematic diagram of the voltage-frequency control circuit, which generates a control signal of the sawtooth wave generator according to the duty cycle of the PWM signal, so as to realize the increase and decrease of the frequency of the sawtooth wave.

图3为本发明第一实施例提供的频率可变的锯齿波发生电路的电路结构,其利用555定时器的固有特性产生锯齿波。 Fig. 3 is the circuit structure of the frequency-variable sawtooth wave generation circuit provided by the first embodiment of the present invention, which utilizes the inherent characteristics of the 555 timer to generate the sawtooth wave.

所述锯齿波发生电路包括:电阻R301、电阻R302、电阻R303、电容C301、电容C302、三极管Q301、三极管Q302,定时器以及对上述元件进行供电的电源VCC。所述电阻R301一端连接到三极管Q301的射极,另一端连接到电阻R303的一端,所述电阻R303的另一端连接到三极管Q301的集电极,所述三极管Q301的基极连接三极管Q302的基极,所述三极管Q302的集电极分别连接电容C301的一端以及定时器,所述定时器还连接了电容C302。 The sawtooth wave generating circuit includes: resistor R301, resistor R302, resistor R303, capacitor C301, capacitor C302, transistor Q301, transistor Q302, a timer, and a power supply VCC for supplying power to the above components. One end of the resistor R301 is connected to the emitter of the transistor Q301, the other end is connected to one end of the resistor R303, the other end of the resistor R303 is connected to the collector of the transistor Q301, and the base of the transistor Q301 is connected to the base of the transistor Q302 , the collector of the triode Q302 is respectively connected to one end of the capacitor C301 and the timer, and the timer is also connected to the capacitor C302.

在图3中,电阻R301、电阻R302、晶体管Q301、晶体管Q302和电阻R303组成电流镜电路,对电容C301进行恒流充电,使C301的端电压,即303处的电压线性升高。305为555定时器,当303的电压超过555定时器的内部阈值时,其内部集成三极管导通,将C301的电荷瞬间泄放掉,使303的电压降为零,同时使555定时器的内部三极管截止,电流镜重新对C301进行充电,如此产生锯齿波,锯齿波的频率由其电压上升斜率决定,通过改变301的电压,可以改变电流镜的电流,从而改变锯齿波的电压上升斜率,实现对锯齿波频率的改变。 In Fig. 3, resistor R301, resistor R302, transistor Q301, transistor Q302 and resistor R303 form a current mirror circuit to charge capacitor C301 with a constant current, so that the terminal voltage of C301, that is, the voltage at 303, increases linearly. 305 is a 555 timer. When the voltage of 303 exceeds the internal threshold of the 555 timer, its internal integrated transistor is turned on, and the charge of C301 is released instantly, so that the voltage of 303 drops to zero, and at the same time, the internal of the 555 timer The triode is turned off, and the current mirror recharges C301, so that a sawtooth wave is generated. The frequency of the sawtooth wave is determined by its voltage rising slope. By changing the voltage of 301, the current of the current mirror can be changed, thereby changing the voltage rising slope of the sawtooth wave. Changes to the sawtooth frequency.

参阅图3,随着电压Vf的增大,302的电压也增大,由电流镜的原理,304的电压也增大,流过电阻R304的电流降低,即电容C301的充电电流降低,充电速率减慢,则锯齿波的频率降低,从而实现频率随控制电压的增大而降低。 Referring to Fig. 3, as the voltage Vf increases, the voltage of 302 also increases. According to the principle of the current mirror, the voltage of 304 also increases, and the current flowing through the resistor R304 decreases, that is, the charging current of the capacitor C301 decreases, and the charging rate Slow down, the frequency of the sawtooth wave decreases, so that the frequency decreases with the increase of the control voltage.

请参阅图4,图4为图3所示锯齿波发生器电路的仿真波形,n_408为301的波形,n_392为303的波形,即锯齿波输出,可见随着控制电压Vf的增大,锯齿波的开关频率降低。 Please refer to Figure 4, Figure 4 is the simulation waveform of the sawtooth wave generator circuit shown in Figure 3, n_408 is the waveform of 301, n_392 is the waveform of 303, that is, the sawtooth wave output, it can be seen that with the increase of the control voltage Vf, the sawtooth wave The switching frequency is reduced.

请参阅图5,其锯齿波频率随控制电压的增大而增大。同样,其利用555定时器的固有特性产生锯齿波。 Please refer to Figure 5, the frequency of the sawtooth wave increases with the increase of the control voltage. Also, it takes advantage of the inherent characteristics of the 555 timer to generate a sawtooth wave.

所述锯齿波发生电路包括:电阻R501、电阻R502、电阻R503、电容C501、电容C502、三极管Q501、三极管Q502、定时器以及对上述元件供电的电源VCC, The sawtooth wave generating circuit includes: a resistor R501, a resistor R502, a resistor R503, a capacitor C501, a capacitor C502, a transistor Q501, a transistor Q502, a timer, and a power supply VCC for supplying power to the above components,

所述三极管Q501的射极与电阻R501相连,所述三极管Q501的集电极与电容C501相连,所述三极管Q501的基极连接三极管Q502的基极,所述三极管Q502的集电极连接电阻R503,所述三极管Q502的射极连接电阻R502的一端,所述电阻R502、三极管Q501的集电极均与定时器连接,所述定时器还连接了电容C502。 The emitter of the triode Q501 is connected to the resistor R501, the collector of the triode Q501 is connected to the capacitor C501, the base of the triode Q501 is connected to the base of the triode Q502, and the collector of the triode Q502 is connected to the resistor R503. The emitter of the triode Q502 is connected to one end of the resistor R502, the resistor R502 and the collector of the triode Q501 are both connected to the timer, and the timer is also connected to the capacitor C502.

其中,电阻R501、电阻R502、晶体管Q501、晶体管Q502和电阻R503组成电流镜电路,对电容C501进行恒流充电,使C501的端电压,即503处的电压线性升高。 Among them, resistor R501, resistor R502, transistor Q501, transistor Q502 and resistor R503 form a current mirror circuit, which charges capacitor C501 with a constant current, so that the terminal voltage of C501, that is, the voltage at 503, increases linearly.

参阅图5,随着电压Vf的增大,电阻R501两端的电压也增大,流过电阻R501的电流增大,即电容C501的充电电流变大,充电速率加快,则锯齿波的频率提高,从而实现频率随控制电压的增大而增大。 Referring to Figure 5, as the voltage Vf increases, the voltage at both ends of the resistor R501 also increases, and the current flowing through the resistor R501 increases, that is, the charging current of the capacitor C501 becomes larger, the charging rate is accelerated, and the frequency of the sawtooth wave increases. Thus, the frequency increases with the increase of the control voltage.

请参阅图6所示的仿真波形,n_487为501的波形,n_392为503的波形,即锯齿波输出,可见随着控制电压Vf的降低,锯齿波的开关频率降低。 Please refer to the simulation waveform shown in Figure 6, n_487 is the waveform of 501, and n_392 is the waveform of 503, that is, the sawtooth wave output. It can be seen that the switching frequency of the sawtooth wave decreases with the decrease of the control voltage Vf.

图7为图3所示的振荡频率随控制电压增大而降低的锯齿波发生器的简化实现形式。 FIG. 7 is a simplified implementation form of the sawtooth wave generator shown in FIG. 3 whose oscillation frequency decreases as the control voltage increases.

在该实施例中,所述锯齿波发生电路包括:电阻R701、电阻R702、电阻R703、电容C701、电容C702、三极管Q702,定时器以及对上述元件进行供电的电源VCC。所述电阻R701一端连接到三极管Q702的基极,另一端连接到电阻R703的一端,所述电阻R703的另一端连接到三极管Q702的基极,所述三极管Q702的集电极分别连接电容C701的一端以及定时器,所述定时器还连接了电容C702。所述电容C701另一端接地。所述三极管Q702的射极接电阻R702的一端,R702的另一端接定时器。 In this embodiment, the sawtooth wave generating circuit includes: a resistor R701, a resistor R702, a resistor R703, a capacitor C701, a capacitor C702, a transistor Q702, a timer, and a power supply VCC for supplying power to the above components. One end of the resistor R701 is connected to the base of the transistor Q702, the other end is connected to one end of the resistor R703, the other end of the resistor R703 is connected to the base of the transistor Q702, and the collector of the transistor Q702 is respectively connected to one end of the capacitor C701 As well as a timer, the timer is also connected with a capacitor C702. The other end of the capacitor C701 is grounded. The emitter of the transistor Q702 is connected to one end of the resistor R702, and the other end of the R702 is connected to the timer.

在本实施例中,是在图3所示的实施例的基础上少用了一个三极管,即Q301。 In this embodiment, on the basis of the embodiment shown in FIG. 3 , one triode, that is, Q301 is omitted.

图8为图5所示的振荡频率随控制电压减小而降低的锯齿波发生器的简化实现形式。 FIG. 8 is a simplified implementation of the sawtooth generator shown in FIG. 5 whose oscillation frequency decreases as the control voltage decreases.

在本实施例中,所述锯齿波发生电路包括:电阻R801、电阻R802、电阻R803、电容C801、电容C802、三极管Q801、定时器以及对上述元件供电的电源VCC, In this embodiment, the sawtooth wave generating circuit includes: a resistor R801, a resistor R802, a resistor R803, a capacitor C801, a capacitor C802, a transistor Q801, a timer, and a power supply VCC for supplying power to the above components,

所述三极管Q801的射极与电阻R801相连,所述三极管Q801的集电极与电容C801相连,所述三极管Q801的基极分别连接电阻R802、电阻R803的一端,所述三极管Q801的集电极分别与电容C801及定时器相连。所述电阻R802的另一端接定时器。所述电阻R803的另一端接地。所述定时器还连接了电容C802。 The emitter of the triode Q801 is connected to the resistor R801, the collector of the triode Q801 is connected to the capacitor C801, the base of the triode Q801 is respectively connected to one end of the resistor R802 and the resistor R803, and the collector of the triode Q801 is respectively connected to The capacitor C801 is connected with the timer. The other end of the resistor R802 is connected with a timer. The other end of the resistor R803 is grounded. The timer is also connected with a capacitor C802.

本实施例是在图5所示的实施例的基础上,减少使用了一个三极管,即图5中的Q502。 In this embodiment, on the basis of the embodiment shown in FIG. 5 , one transistor is reduced, that is, Q502 in FIG. 5 .

图9为锯齿波发生器的另一种实现方式。该锯齿波发生电路包括:电容C901、电阻R901、电阻R902、电阻R903、电阻R904、三极管Q901、三极管Q902以及比较器U901。 FIG. 9 is another implementation of the sawtooth generator. The sawtooth wave generating circuit includes: a capacitor C901, a resistor R901, a resistor R902, a resistor R903, a resistor R904, a transistor Q901, a transistor Q902 and a comparator U901.

所述三极管Q901的射极与电阻R901相连,所述三极管Q901的集电极与电容C901相连,所述三极管Q901的基极连接于电阻R902与电阻R903之间,所述三极管Q902的集电极连接至三极管Q901的集电极,所述三极管Q902的射极连接电容C901的另一端,所述电阻R902、三极管Q901的集电极均与定时器连接,所述定时器还连接了电容C902。 The emitter of the transistor Q901 is connected to the resistor R901, the collector of the transistor Q901 is connected to the capacitor C901, the base of the transistor Q901 is connected between the resistor R902 and the resistor R903, and the collector of the transistor Q902 is connected to The collector of the transistor Q901 and the emitter of the transistor Q902 are connected to the other end of the capacitor C901, the resistor R902 and the collector of the transistor Q901 are both connected to the timer, and the timer is also connected to the capacitor C902.

通过比较器U901控制开关管Q902的导通和关断,给充电电容C901放电,取代555定时器,产生锯齿波,锯齿波的幅值由比较器U901的反相输入端基准电压决定。 The switching tube Q902 is controlled by the comparator U901 to discharge the charging capacitor C901 to replace the 555 timer to generate a sawtooth wave. The amplitude of the sawtooth wave is determined by the reference voltage of the inverting input terminal of the comparator U901.

图10为开关频率随占空比增大而减小的开关电源脉冲宽度调制控制方法的具体实现方式。 FIG. 10 is a specific implementation of a switching power supply pulse width modulation control method in which the switching frequency decreases as the duty cycle increases.

所述锯齿波发生电路1000包括:定时器、电容C1003、电源VCC、电阻R1001、电阻R1002、电阻R1003、电容C1001以及PNP三极管Q1001, The sawtooth wave generating circuit 1000 includes: a timer, a capacitor C1003, a power supply VCC, a resistor R1001, a resistor R1002, a resistor R1003, a capacitor C1001 and a PNP transistor Q1001,

所述电阻R1001和电阻R1002串联,三极管Q1001的基极连接到R1001和R1002的串联点,电阻R1001的另一端接频率控制信号1007,Q1001的发射极接电阻R1002,R1002的另一端接固定电源电压,Q1001的集电极接电容C1001,所述定时器的高触发端、低触发端和放电端接到一起,同时接到电容C1001的正端,所述电压控制端接电容C1003的正端,清零端接电源电压。 The resistor R1001 is connected in series with the resistor R1002, the base of the triode Q1001 is connected to the series connection point of R1001 and R1002, the other end of the resistor R1001 is connected to the frequency control signal 1007, the emitter of Q1001 is connected to the resistor R1002, and the other end of R1002 is connected to a fixed power supply voltage , the collector of Q1001 is connected to capacitor C1001, the high trigger terminal, low trigger terminal and discharge terminal of the timer are connected together, and at the same time connected to the positive terminal of capacitor C1001, the voltage control terminal is connected to the positive terminal of capacitor C1003, clear Zero terminal is connected to supply voltage.

PWM发生器1001由比较器1003和外围电路组成,误差放大器由运算放大器1005和外围补偿电路组成,驱动电路1002提高PWM信号的输出能力。锯齿波发生电路1000、频率控制电路1001、驱动电路1002、PWM发生器1003和误差放大器1005共同组成了频率自动变化的开关电源脉冲宽度调制控制器。 The PWM generator 1001 is composed of a comparator 1003 and peripheral circuits, the error amplifier is composed of an operational amplifier 1005 and a peripheral compensation circuit, and the driving circuit 1002 improves the output capability of the PWM signal. The sawtooth wave generating circuit 1000, the frequency control circuit 1001, the drive circuit 1002, the PWM generator 1003 and the error amplifier 1005 together constitute a switching power supply pulse width modulation controller with automatic frequency change.

所述频率控制电路1001包括:电阻R1006、电阻R1004、电阻R1005、电容C1002和运算放大器U1001, The frequency control circuit 1001 includes: a resistor R1006, a resistor R1004, a resistor R1005, a capacitor C1002 and an operational amplifier U1001,

电阻R1006和电容C1002组成RC滤波电路,提取PWM信号的占空比值,并且,所述电阻R1006分别与电容C1002的一端、运算放大器U1001的同相输入端相连,所述电容C1002的另一端接地; The resistor R1006 and the capacitor C1002 form an RC filter circuit to extract the duty cycle value of the PWM signal, and the resistor R1006 is respectively connected to one end of the capacitor C1002 and the non-inverting input end of the operational amplifier U1001, and the other end of the capacitor C1002 is grounded;

电阻R1004、电阻R1005和运算放大器U1001构成同相放大器,对频率控制信号进行调理,并且所述电阻R1004、电阻R1005的一端均连接至运算放大器U1001的反相输入端,所述电阻R1004的另一端接运算放大器U1001的输出端,所述电阻R1005的另一端接地。 Resistor R1004, resistor R1005 and operational amplifier U1001 form a non-inverting amplifier to adjust the frequency control signal, and one end of the resistor R1004 and resistor R1005 is connected to the inverting input terminal of the operational amplifier U1001, and the other end of the resistor R1004 is connected to The output end of the operational amplifier U1001, the other end of the resistor R1005 is grounded.

图11 中n_392为锯齿波发生器的输出,即1004的波形,n_556为PWM输出,即1006的波形。 In Figure 11, n_392 is the output of the sawtooth generator, which is the waveform of 1004, and n_556 is the PWM output, which is the waveform of 1006.

请参阅图12,图12为开关频率随占空比减小而减小的开关电源脉冲宽度调制方法的具体实现方式。 Please refer to FIG. 12 . FIG. 12 is a specific implementation of the pulse width modulation method of the switching power supply in which the switching frequency decreases as the duty cycle decreases.

在本实施例中,所述锯齿波发生电路1200包括: In this embodiment, the sawtooth wave generating circuit 1200 includes:

定时器、电容C1203、电源VCC、电阻R1201、电阻R1202、电阻R1203、电容C1201以及PNP三极管Q1201。 Timer, capacitor C1203, power supply VCC, resistor R1201, resistor R1202, resistor R1203, capacitor C1201 and PNP transistor Q1201.

所述电阻R1201和电阻R1203串联,三极管Q1201的基极连接到R1201和R1203的串联点,电阻R1201的另一端接定时器,Q1201的发射极接电阻R1202,R1202的另一端接频率控制电路,Q1201的集电极接电容C1201,所述定时器的高触发端、低触发端和放电端接到一起,同时接到电容C1201的正端,所述电压控制端接电容C1203的正端,清零端接电源电压。 The resistor R1201 and the resistor R1203 are connected in series, the base of the triode Q1201 is connected to the series connection point of R1201 and R1203, the other end of the resistor R1201 is connected to the timer, the emitter of Q1201 is connected to the resistor R1202, and the other end of R1202 is connected to the frequency control circuit, Q1201 The collector of the timer is connected to the capacitor C1201, the high trigger terminal, the low trigger terminal and the discharge terminal of the timer are connected together, and at the same time connected to the positive terminal of the capacitor C1201, the voltage control terminal is connected to the positive terminal of the capacitor C1203, and the reset terminal Connect to the supply voltage.

本实施例与图10所示电路不同在于,图10所示为频率随占空比增大而减小。而图12所示电路为频率随占空比增大而增大。表现于电路,主要在于:三极管的接法不同。 The difference between this embodiment and the circuit shown in Fig. 10 is that Fig. 10 shows that the frequency decreases as the duty cycle increases. The circuit shown in Figure 12 shows that the frequency increases with the increase of the duty cycle. It is manifested in the circuit, mainly in that the connection of the triode is different.

图13中n_392锯齿波发生器的输出,即1204的波形,n_556为PWM输出,即1206的波形。 In Figure 13, the output of n_392 sawtooth wave generator is the waveform of 1204, and n_556 is the PWM output, which is the waveform of 1206.

以上所述仅为本发明的较佳实施例而已,并不用以限制本发明,凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等,均应包含在本发明的保护范围之内。 The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (9)

1.一种频率可变的开关电源脉冲宽度调制控制器,其特征在于,所述控制器包括: 1. A frequency-variable switching power supply pulse width modulation controller, characterized in that the controller comprises: 一个频率随控制电压增大而增大或降低的锯齿波发生电路,一个频率控制电路以及一个PWM发生器, A sawtooth wave generating circuit whose frequency increases or decreases as the control voltage increases, a frequency control circuit and a PWM generator,     所述PWM发生器的输出端与所述频率控制电路的输入端相连,所述频率控制电路的输出端与所述锯齿波发生器的输入端相连,所述锯齿波发生器的输出端与所述PWM发生器的输入端相连。 The output end of the PWM generator is connected to the input end of the frequency control circuit, the output end of the frequency control circuit is connected to the input end of the sawtooth wave generator, and the output end of the sawtooth wave generator is connected to the input end of the sawtooth wave generator. connected to the input of the PWM generator. 2.根据权利要求1所述的频率可变的开关电源脉冲宽度调制控制器,其特征在于,所述控制器还包括: 2. the variable frequency switching power supply pulse width modulation controller according to claim 1, is characterized in that, described controller also comprises: 与所述PWM发生器的输入端相连的误差放大器。 An error amplifier connected to the input of the PWM generator. 3.根据权利要求1所述的频率可变的开关电源脉冲宽度调制控制器,其特征在于,所述锯齿波发生电路包括: 3. The frequency-variable switching power supply pulse width modulation controller according to claim 1, wherein the sawtooth wave generating circuit comprises: 定时器、电容C1003、电源VCC、电阻R1001、电阻R1002、电阻R1003、电容C1001以及PNP三极管Q1001, Timer, capacitor C1003, power supply VCC, resistor R1001, resistor R1002, resistor R1003, capacitor C1001 and PNP transistor Q1001, 所述电阻R1001和电阻R1002串联,三极管Q1001的基极连接到R1001和R1002的串联点,电阻R1001的另一端接频率控制信号1007,Q1001的发射极接电阻R1002,R1002的另一端接固定电源电压,Q1001的集电极接电容C1001,所述定时器的高触发端、低触发端和放电端接到一起,同时接到电容C1001的正端,所述电压控制端接电容C1003的正端,清零端接电源电压。 The resistor R1001 is connected in series with the resistor R1002, the base of the triode Q1001 is connected to the series connection point of R1001 and R1002, the other end of the resistor R1001 is connected to the frequency control signal 1007, the emitter of Q1001 is connected to the resistor R1002, and the other end of R1002 is connected to a fixed power supply voltage , the collector of Q1001 is connected to capacitor C1001, the high trigger terminal, low trigger terminal and discharge terminal of the timer are connected together, and at the same time connected to the positive terminal of capacitor C1001, the voltage control terminal is connected to the positive terminal of capacitor C1003, clear Zero terminal is connected to supply voltage. 4.根据权利要求1所述的频率可变的开关电源脉冲宽度调制控制器,其特征在于,所述锯齿波发生电路1200包括: 4. The frequency-variable switching power supply pulse width modulation controller according to claim 1, wherein the sawtooth wave generating circuit 1200 comprises: 定时器、电容C1203、电源VCC、电阻R1201、电阻R1202、电阻R1203、电容C1201以及PNP三极管Q1201, Timer, capacitor C1203, power supply VCC, resistor R1201, resistor R1202, resistor R1203, capacitor C1201 and PNP transistor Q1201, 所述电阻R1201和电阻R1203串联,三极管Q1201的基极连接到R1201和R1203的串联点,电阻R1201的另一端接定时器,Q1201的发射极接电阻R1202,R1202的另一端接频率控制电路,Q1201的集电极接电容C1201,所述定时器的高触发端、低触发端和放电端接到一起,同时接到电容C1201的正端,所述电压控制端接电容C1203的正端,清零端接电源电压。 The resistor R1201 and the resistor R1203 are connected in series, the base of the triode Q1201 is connected to the series connection point of R1201 and R1203, the other end of the resistor R1201 is connected to the timer, the emitter of Q1201 is connected to the resistor R1202, and the other end of R1202 is connected to the frequency control circuit, Q1201 The collector of the timer is connected to the capacitor C1201, the high trigger terminal, the low trigger terminal and the discharge terminal of the timer are connected together, and at the same time connected to the positive terminal of the capacitor C1201, the voltage control terminal is connected to the positive terminal of the capacitor C1203, and the reset terminal Connect to the supply voltage. 5.根据权利要求1所述的频率可变的开关电源脉冲宽度调制控制器,其特征在于,所述频率控制电路包括:电阻R1006、电阻R1004、电阻R1005、电容C1002和运算放大器U1001, 5. The variable frequency switching power supply pulse width modulation controller according to claim 1, wherein the frequency control circuit comprises: a resistor R1006, a resistor R1004, a resistor R1005, a capacitor C1002 and an operational amplifier U1001, 电阻R1006和电容C1002组成RC滤波电路,提取PWM信号的占空比值,并且,所述电阻R1006分别与电容C1002的一端、运算放大器U1001的同相输入端相连,所述电容C1002的另一端接地; The resistor R1006 and the capacitor C1002 form an RC filter circuit to extract the duty cycle value of the PWM signal, and the resistor R1006 is respectively connected to one end of the capacitor C1002 and the non-inverting input end of the operational amplifier U1001, and the other end of the capacitor C1002 is grounded; 电阻R1004、电阻R1005和运算放大器U1001构成同相放大器,对频率控制信号进行调理,并且所述电阻R1004、电阻R1005的一端均连接至运算放大器U1001的反相输入端,所述电阻R1004的另一端接运算放大器U1001的输出端,所述电阻R1005的另一端接地。 Resistor R1004, resistor R1005 and operational amplifier U1001 form a non-inverting amplifier to adjust the frequency control signal, and one end of the resistor R1004 and resistor R1005 is connected to the inverting input terminal of the operational amplifier U1001, and the other end of the resistor R1004 is connected to The output end of the operational amplifier U1001, the other end of the resistor R1005 is grounded. 6.根据权利要求1所述的频率可变的开关电源脉冲宽度调制控制器,其特征在于,所述误差放大器包括:运算放大器1005和外围补偿电路。 6 . The frequency-variable switching power supply pulse width modulation controller according to claim 1 , wherein the error amplifier comprises: an operational amplifier 1005 and a peripheral compensation circuit. 7.根据权利要求1所述的频率可变的开关电源脉冲宽度调制控制器,其特征在于,所述锯齿波发生电路包括:电阻R301、电阻R302、电阻R303、电容C301、电容C302、三极管Q301、三极管Q302,定时器以及对上述元件进行供电的电源VCC, 7. The variable frequency switching power supply pulse width modulation controller according to claim 1, wherein the sawtooth wave generating circuit comprises: resistor R301, resistor R302, resistor R303, capacitor C301, capacitor C302, transistor Q301 , transistor Q302, timer and power supply VCC for supplying power to the above components, 所述电阻R301一端连接到三极管Q301的射极,另一端连接到电阻R303的一端,所述电阻R303的另一端连接到三极管Q301的集电极,所述三极管Q301的基极连接三极管Q302的基极,所述三极管Q302的集电极分别连接电容C301的一端以及定时器,所述定时器还连接了电容C302。 One end of the resistor R301 is connected to the emitter of the transistor Q301, the other end is connected to one end of the resistor R303, the other end of the resistor R303 is connected to the collector of the transistor Q301, and the base of the transistor Q301 is connected to the base of the transistor Q302 , the collector of the triode Q302 is respectively connected to one end of the capacitor C301 and the timer, and the timer is also connected to the capacitor C302. 8.根据权利要求1所述的频率可变的开关电源脉冲宽度调制控制器,其特征在于,所述锯齿波发生电路包括:电阻R501、电阻R502、电阻R503、电容C501、电容C502、三极管Q501、三极管Q502、定时器以及对上述元件供电的电源VCC, 8. The variable frequency switching power supply pulse width modulation controller according to claim 1, characterized in that, the sawtooth wave generating circuit comprises: resistor R501, resistor R502, resistor R503, capacitor C501, capacitor C502, transistor Q501 , transistor Q502, timer and the power supply VCC for supplying power to the above components, 所述三极管Q501的射极与电阻R501相连,所述三极管Q501的集电极与电容C501相连,所述三极管Q501的基极连接三极管Q502的基极,所述三极管Q502的集电极连接电阻R503,所述三极管Q502的射极连接电阻R502的一端,所述电阻R502、三极管Q501的集电极均与定时器连接,所述定时器还连接了电容C502。 The emitter of the triode Q501 is connected to the resistor R501, the collector of the triode Q501 is connected to the capacitor C501, the base of the triode Q501 is connected to the base of the triode Q502, and the collector of the triode Q502 is connected to the resistor R503. The emitter of the triode Q502 is connected to one end of the resistor R502, the resistor R502 and the collector of the triode Q501 are both connected to the timer, and the timer is also connected to the capacitor C502. 9.根据权利要求1所述的频率可变的开关电源脉冲宽度调制控制器,其特征在于,所述锯齿波发生电路包括:电容C901、电阻R901、电阻R902、电阻R903、电阻R904、三极管Q901、三极管Q902以及比较器U901, 9. The frequency variable switching power supply pulse width modulation controller according to claim 1, characterized in that, the sawtooth wave generating circuit comprises: capacitor C901, resistor R901, resistor R902, resistor R903, resistor R904, transistor Q901 , transistor Q902 and comparator U901, 所述三极管Q901的射极与电阻R901相连,所述三极管Q901的集电极与电容C901相连,所述三极管Q901的基极连接于电阻R902与电阻R903之间,所述三极管Q902的集电极连接至三极管Q901的集电极,所述三极管Q902的射极连接电容C901的另一端,所述电阻R902、三极管Q901的集电极均与定时器连接,所述定时器还连接了电容C902。 The emitter of the transistor Q901 is connected to the resistor R901, the collector of the transistor Q901 is connected to the capacitor C901, the base of the transistor Q901 is connected between the resistor R902 and the resistor R903, and the collector of the transistor Q902 is connected to The collector of the transistor Q901 and the emitter of the transistor Q902 are connected to the other end of the capacitor C901, the resistor R902 and the collector of the transistor Q901 are both connected to the timer, and the timer is also connected to the capacitor C902.
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