TWI805148B - Switching power converter circuit, clock generator circuit and clock generation method having spread spectrum - Google Patents

Abstract

A spread spectrum switching power converter circuit includes: a power stage circuit which includes an inductor and a power switch and is configured to switch the power switch according to a switching signal having spread spectrum for power conversion; a variable frequency oscillator, configured to generate a spread spectrum clock signal according to a spread spectrum control signal; a spread spectrum control circuit configured to generate the spread spectrum control signal according to a first clock signal and a second clock signal; and a Pulse Width Modulation (PWM) circuit, configured to generate the switching signal according to a feedback signal based on the spread spectrum clock signal. The spread spectrum control circuit samples and operates a periodical wave and a random wave to generate the spread spectrum control signal. The random wave is generated according to the first clock signal and the periodical wave is generated according to the second clock signal.

Description

Spread spectrum switching power conversion circuit, clock generation circuit and clock generation method

The invention relates to a switchable power conversion circuit, in particular to a spread-spectrum switching power conversion circuit which can effectively improve the spread-spectrum effect and expand the applicable frequency range of the spread-spectrum. The present invention also relates to a clock generation circuit and a clock generation method capable of achieving spread spectrum.

Figure 1A and Figure 1B show the modulation waveform diagrams of the conventional spread frequency modulation method, wherein Figure 1A and Figure 1B use the sawtooth wave signal and the triangular wave signal respectively to spread the switching frequency Fsw, and the switching frequency range is △ f. FIG. 2 shows a modulation waveform diagram of another conventional spread spectrum modulation method, wherein FIG. 2 uses a pseudo random waveform to spread spectrum the switching frequency Fsw.

The disadvantage of the conventional spread spectrum modulation method shown in Fig. 1A, Fig. 1B and Fig. 2 is that the periodical analog spread spectrum modulation method shown in Fig. 1A and Fig. 1B only has a remarkable spread spectrum effect in the frequency band of 150kHz~30MHz, while The frequency hopping spread spectrum modulation method shown in Figure 2 is only effective in the 30MHz~1GHz frequency band spread spectrum. In other words, neither of the two spread spectrum modulation methods is applicable to both low frequency and high frequency frequency bands.

In view of this, the present invention aims at the deficiencies of the above-mentioned prior art, and proposes a spread-spectrum switching power conversion circuit, a clock generation circuit and a clock generation method that can effectively improve the spread-spectrum effect and expand the applicable frequency range of the spread-spectrum.

In one aspect, the present invention provides a spread-spectrum switching power conversion circuit, comprising: a variable-frequency oscillator for generating a spread-spectrum clock signal with spread-spectrum according to a spread-spectrum control signal, wherein the spread-spectrum The frequency clock signal has a basic frequency, and under the control of the spread spectrum control signal, it has a switching frequency variation range; a spread frequency control circuit is used to generate a frequency signal according to a first clock signal and a second clock signal The spread spectrum control signal; and a pulse width modulation (PWM, Pulse Width Modulation) circuit, which is used to generate a switching signal with spread spectrum according to a feedback signal based on the spread spectrum clock signal; wherein the switching signal is used To control a power stage circuit, the power stage circuit includes an inductor and at least one power switch coupled to each other, and is used to switch the power switch to perform power conversion according to the switching signal with spread frequency; wherein the spread frequency control The circuit includes: a first periodic waveform generator, which is used to generate a periodic first periodic waveform according to the second clock signal; a first random waveform generator, which is used to generate a periodic waveform according to the first clock signal. A first random waveform of randomness; and an operation unit for sampling the first random waveform and the first periodic waveform, and performing operations to generate the spread spectrum control signal.

In another viewpoint, the present invention provides a clock generation circuit for generating a spread frequency clock signal with spread frequency according to a first clock signal and a second clock signal, wherein the spread frequency The pulse signal has a fundamental frequency and a switching frequency range; the clock generating circuit includes: a variable frequency oscillator for generating the spread frequency clock signal with spread frequency according to a spread frequency control signal; and A frequency spread control circuit, used to generate the frequency spread control signal according to the first clock signal and the second clock signal; wherein the frequency spread control circuit includes: a first periodic wave A shape generator, used to generate a periodic first periodic waveform according to the second clock signal; a first random waveform generator, used to generate a first random waveform with randomness according to the first clock signal a waveform; and an operation unit, which is used to sample the first random waveform and the first periodic waveform, and perform operations to generate the spread spectrum control signal.

In yet another viewpoint, the present invention provides a clock generation method for generating a spread-spectrum clock signal with spread-spectrum based on a first clock signal and a second clock signal, wherein the spread-spectrum time The pulse signal has a basic frequency and has a switching frequency range; the clock generation method includes: generating the spread frequency clock signal with spread frequency according to a spread spectrum control signal; The second clock signal generates the spread spectrum control signal; wherein the step of generating the spread spectrum control signal includes: generating a periodic first cycle waveform according to the second clock signal; generating a periodic waveform according to the first clock signal A first random waveform with randomness; and sampling the first random waveform and the first periodic waveform, and performing operations to generate the spread spectrum control signal.

In one embodiment, the first periodic waveform is a triangle wave, a sawtooth wave or a sine wave.

In one embodiment, the first random waveform is a pseudo random staircase wave.

In one embodiment, the first periodic waveform generator includes an up-down counter or a look-up table circuit, which is used to generate the first periodic waveform by counting or looking up a table according to the second clock signal.

In one embodiment, the first clock signal is the spread spectrum clock signal, and the first random waveform is generated in a feedback manner, wherein the first clock signal and the second clock signal come from different sources and Independent of each other; the computing unit includes: a sampling synchronous circuit for sampling the first periodic waveform based on the first clock signal to generate a sampled periodic waveform, thereby making the sampled periodic waveform synchronized with the first One of the sampling frequencies of the random waveform; and an operator unit for The spread spectrum control signal is generated according to the sum of the sampled periodic waveform and a signal related to the first random waveform.

In one embodiment, it is characterized by one of the following: (1) wherein the operator unit is used to generate the spread spectrum control signal according to the sum of the sampled periodic waveform and the first random waveform; or (2) the The operation unit further includes a sampling control circuit for down-sampling the first random waveform to generate a down-frequency random waveform, wherein the operation sub-unit is used for determining the difference between the sampled periodic waveform and the down-frequency random waveform and generate the spread spectrum control signal.

In one embodiment, the operation unit further includes a frequency division unit, wherein the operation subunit generates a pre-spread control signal according to the sum of the sampled periodic waveform and a signal related to the first random waveform, wherein The frequency dividing unit reduces the frequency of the pre-spread control signal by m times to generate the spread control signal, wherein m is a positive integer.

In one embodiment, the computing unit further includes a control signal generator for generating a control switching signal with random properties, wherein the computing subunit uses the control switching signal to correlate the sampled periodic waveform with the A signal of the first random waveform is randomly added or subtracted to generate an operation result, and the spread spectrum control signal is generated according to the operation result.

In one embodiment, the computing unit includes: a control signal generator for generating a control switching signal, wherein the control switching signal has randomness; The first periodic waveform is randomly added or subtracted to a signal related to the first random waveform to generate an operation result, and the spread spectrum control signal is generated according to the operation result.

In one embodiment, the spread frequency control circuit further includes a sampling control circuit for down-sampling the first random waveform to generate a down-frequency random waveform, wherein the operator unit is used for switching based on the control The signal is randomly added or subtracted to the first cycle waveform and the down-frequency random waveform to generate an operation result, and the spread spectrum control signal is generated according to the operation result.

In one embodiment, the first clock signal used to generate the first random waveform is different and independent from a clock signal used to generate the control switching signal.

The advantage of the present invention is that the present invention can improve the spread spectrum effect and expand the applicable frequency range of spread spectrum by mixing two different spread spectrum techniques, and trigger the first random waveform generator to update the random seed by controlling the sampling control circuit The timing can further enhance the spread spectrum effect.

In the following detailed description by means of specific embodiments, it will be easier to understand the purpose, technical content, characteristics and effects of the present invention.

10: Spread spectrum switching power conversion circuit

11: Power stage circuit

12: Pulse width modulation (PWM) circuit

13: Spread spectrum control circuit

131, 731A, 731B: first cycle waveform generator

132: The first random waveform generator

133: Control signal generator

134: Addition and subtraction unit

135: Addition unit

136: sampling control circuit

137: Sampling synchronization circuit

14: Variable Frequency Oscillator

1413, 1513, 1613, 1713: spread spectrum control circuit

15, 1415, 1515, 1615, 1715: clock generation circuit

438,538,638,738: arithmetic unit

7311: counter

7312: look-up table circuit

BC, BC1, BC2: basic clock signal

CLK1, CLK2: clock signal

CKSYS: system clock

CKSW: Spread spectrum clock signal

CS1: Control switching signal

SSC, SSC’: spread spectrum control signal

FB: feedback signal

Fsw: switching frequency

Ff: fundamental frequency

Iout: output current

L: Inductor

LG, UG: switch signal

LX: switch node

PW1, PW1': first cycle waveform

QU,QL: power switch

RW1, RW1': the first random waveform

Vin: input power

VLX: switching node voltage

Vout: output power

△f: switching frequency range

FIG. 1A and FIG. 1B are modulation waveform diagrams showing conventional spread spectrum modulation methods.

FIG. 2 shows a frequency hopping waveform diagram of another conventional spread spectrum modulation method.

FIG. 3 is a circuit block diagram showing a spread spectrum switching power conversion circuit according to an embodiment of the present invention.

FIG. 4 is a circuit block diagram showing a spread spectrum control circuit according to an embodiment of the present invention.

FIG. 5 is a circuit block diagram showing a spread spectrum control circuit according to an embodiment of the present invention.

FIG. 6 is a circuit block diagram showing a spread spectrum control circuit according to an embodiment of the present invention.

7A-7B are circuit block diagrams showing a first period waveform generator according to a more specific embodiment of the present invention.

8 is a schematic diagram showing an embodiment of the first periodic waveform (triangular wave) and the first random waveform (virtual random waveform) and the generated spread spectrum control signal according to an embodiment of the present invention.

9 is a schematic diagram showing an embodiment of the first periodic waveform (sawtooth waveform) and the first random waveform (virtual random waveform) and the generated spread spectrum control signal according to another embodiment of the present invention.

FIG. 10 shows an embodiment of the first periodic waveform (sine wave) according to yet another embodiment of the present invention.

FIG. 11A shows a comparison between the power spectrum of an unmodulated narrowband interfering signal and the spectrum spread down to the lower frequency band according to an embodiment of the present invention.

11B shows a comparison between the power spectrum of an unmodulated narrowband interfering signal and the spectrum spread out from the center, according to one embodiment of the present invention.

12A to 12K show the synchronous or asynchronous step-down, step-up, reverse-voltage, buck-boost, boost-reverse, and flyback power stage circuits of the spread-spectrum switching power conversion circuit.

FIG. 13 is a block diagram showing a clock generation circuit and a spread spectrum control circuit according to a more specific embodiment of the present invention.

FIG. 14 is a block diagram showing a clock generation circuit and a spread spectrum control circuit according to a more specific embodiment of the present invention.

FIG. 15 is a block diagram showing a clock generation circuit and a spread spectrum control circuit according to a more specific embodiment of the present invention.

FIG. 16 is a block diagram showing a clock generation circuit and a spread spectrum control circuit according to a more specific embodiment of the present invention.

FIG. 17 is a comparison table showing the simulation results of Fast Fourier Transform (FFT, Fast Fourier Transform) of clock signals of various spread spectrum modulation methods.

The diagrams in the present invention are all schematic and mainly intended to show the coupling relationship between various circuits and the relationship between various signal waveforms. As for the circuits, signal waveforms and frequencies, they are not drawn to scale.

FIG. 3 is a circuit block diagram showing a spread spectrum switching power conversion circuit according to an embodiment of the present invention. As shown in FIG. 3 , the spread spectrum switching power conversion circuit 10 of the present invention includes a power stage circuit 11 , a pulse width modulation (PWM, Pulse Width Modulation) circuit 12 , a spread spectrum control circuit 13 and a variable frequency oscillator 14 . The power stage circuit 11 includes an inductor L and at least one power switch. This embodiment includes synchronously switched power switches QU, QL. The power switches QU, QL are used to switch the power switches according to the switching signals UG, LG respectively to perform power conversion. The power switch QU is coupled between the input power supply Vin and the switching node LX, the power switch QL is coupled between the switching node LX and the ground potential, and the inductor L is coupled between the switching node LX and the output power supply Vout, whereby the input The power supply Vin is converted into the output power supply Vout. In other words, the power stage circuit 11 of this embodiment is configured as a synchronous step-down power stage circuit.

It should be noted that this embodiment is only used for illustration rather than limiting the scope of the present invention. As shown in FIG. 12A to FIG. 12K , in other embodiments, the power stage circuit 11 can also be a boost type (boost), a reverse voltage type, a buck-boost type (buck-boost), a boost-reverse voltage type, or a flyback type, for example. Type (flyback) power stage circuit.

The variable frequency oscillator 14 is used to generate a spread frequency clock signal CKSW with spread frequency according to a spread frequency control signal SSC, wherein the spread frequency clock signal CKSW has a fundamental frequency Ff, and is controlled by the spread frequency control signal SSC , with switching frequency range Δf. In one embodiment, the variable frequency oscillator 14 can control the frequency of the spread spectrum clock signal CKSW according to the level of the spread spectrum control signal SSC, where the level of the spread spectrum control signal SSC can be, for example, a voltage level or a current level In other words, the variable frequency oscillator can be, for example, a voltage-controlled oscillator or a current-controlled oscillator.

The spread spectrum control circuit 13 is used for generating the spread spectrum control signal SSC according to the first clock signal CLK1 and the second clock signal CLK2 , the details of which will be described later. In one embodiment, the spread spectrum control circuit 13 and the variable frequency oscillator 14 can be integrated and configured as a clock generator circuit 15 for generating the spread spectrum clock signal CKSW according to the first clock signal CLK1 and the second clock signal CLK2 .

The PWM circuit 12 is used for generating the switching signals UG and LG according to the feedback signal FB based on the spread spectrum clock signal CKSW. In one embodiment, the feedback signal FB is related to the output power Vout, as shown in the figure, and in one embodiment, it can be, for example, a divided voltage of the output power Vout.

Since the spread-spectrum clock signal CKSW has the characteristic of spread-spectrum under the control of the spread-spectrum control signal SSC, the switching signals UG, LG, and the switching voltage generated by the power stage circuit 11 (for example, on the switching node LX The voltage VLX) and the current (such as the inductor current IL or the switch current IHS, ILS) also have spread-spectrum characteristics, thereby effectively reducing the electromagnetic interference caused by the switching of the power stage circuit 11 .

FIG. 4 is a circuit block diagram showing a spread spectrum control circuit (spread spectrum control circuit 413 ) according to an embodiment of the present invention. As shown in FIG. 4, in one embodiment, the spread spectrum control circuit 413 includes a first periodic waveform generator 131, a first random waveform generator 132, and an operation unit 138, wherein the first random waveform generator 132 is used to A clock signal CLK1 generates a first random waveform RW1 with a random property, and the first periodic waveform generator 131 is used to generate a first periodic waveform PW1 with a periodically changing property according to the second clock signal CLK2 . The calculation unit 138 is used for sampling the first random waveform RW1 and the first periodic waveform PW1 and performing calculations to generate the spread spectrum control signal SSC. In one embodiment, the first periodic waveform PW1 is, for example, a triangular wave (as shown in FIG. 8 ), a sawtooth wave (as shown in FIG. 9 ) or a sine wave (as shown in FIG. 10 ). In one embodiment, the first random waveform RW1 is, for example, a random staircase waveform. In one embodiment, the first random waveform RW1 is, for example, a pseudo random staircase wave.

FIG. 5 is a circuit block diagram showing a spread spectrum control circuit according to a more specific embodiment of the present invention. In this embodiment, as shown in FIG. 5 , the calculation unit 138 in the spread spectrum control circuit 513 includes a control signal generator 133 and an addition and subtraction unit 134 .

In one embodiment, the first clock signal CLK1 and the second clock signal CLK2 are different clocks, and are respectively coupled to the basic clock signals BC1 and BC2. In one embodiment, the first clock signal CLK1 and the second clock signal CLK2 are respectively directly connected to the basic clock signals BC1 and BC2 , or obtained after frequency division. In one embodiment, the first clock signal CLK1 is the basic clock signal BC1, and the second clock signal CLK2 is obtained by frequency-dividing the basic clock signal BC2. It should be noted that the basic clock signal BC1 used to generate the first random waveform RW1 is different and independent from the basic clock signal (eg BC2 ) used to generate the control switching signal CS1 .

In one embodiment, the control signal generator 133 is used to generate the control switching signal CS1. In one embodiment, the control signal generator 133 is used to generate the control switching signal CS1 (eg, obtained according to the basic clock signal BC2 ). The addition and subtraction unit 134 is used for randomly adding or subtracting the first periodic waveform PW1 and the first random waveform RW1 according to the control switching signal CS1 to generate the spread spectrum control signal SSC.

FIG. 6 is a circuit block diagram showing a spread spectrum control circuit according to an embodiment of the present invention. Spread spectrum control circuit 613 is similar to spread spectrum control circuit 513. As shown in FIG. The cycle of the clock signal CLK2 is sampled once to generate a down-frequency random waveform RW1', wherein n is a positive integer. In this embodiment, the addition and subtraction unit 134 is used to combine the first cycle waveform PW1 with the down-frequency signal according to the control switching signal CS1. The random waveform RW1' is randomly added or subtracted to generate the spread spectrum control signal SSC. In one embodiment, the sampling period n is, for example but not limited to, 1, 2, 4 or 8, preferably 8, for example. Under different sampling periods n, different spreading effects can be obtained. This example Among them, the control signal generator 133 , the addition and subtraction unit 134 and the sampling control circuit 136 form, for example, the operation unit 138 corresponding to the foregoing embodiments.

FIG. 7A is a circuit block diagram showing a first periodic waveform generator (first periodic waveform generator 731A) according to a more specific embodiment of the present invention. In one embodiment, the first periodic waveform generator 731A includes an up-down counter 7311 for counting up and down according to the second clock signal CLK2 to generate the aforementioned first periodic waveform PW1 .

FIG. 7B is a circuit block diagram showing a first periodic waveform generator (first periodic waveform generator 731B) according to a more specific embodiment of the present invention. In one embodiment, the first periodic waveform generator 731B includes a look-up circuit 7312 for storing a preset periodic waveform, and the look-up circuit 7312 performs a look-up according to the second clock signal CLK2 to read the preset periodic waveform , to generate the aforementioned first periodic waveform PW1.

FIG. 8 is a schematic diagram showing an embodiment of the first periodic waveform and the first random waveform and the generated spread spectrum control signal according to an embodiment of the present invention. In one embodiment, as shown in Figure 8, the first periodic waveform PW1 generated by the first periodic waveform generator can be a triangle wave, and the first random waveform RW1 generated by the first random waveform generator can be a virtual random waveform . The first periodic waveform PW1 and the first random waveform RW1 are randomly added or subtracted by the addition and subtraction unit 134 according to the control switching signal CS1 to generate the spread spectrum control signal SSC as shown in FIG. 8 .

It is worth noting that, as can be seen from FIG. 8, the spread spectrum control signal SSC generated in this embodiment has both the characteristics of part of the triangular wave and part of the characteristics of a virtual random waveform. In addition, because the first periodic waveform PW1 and the first The addition or subtraction of the random waveform RW1 is also determined by the random control switching signal CS1, so that the spread spectrum effect can be improved.

It should be noted that the levels of the first periodic waveform PW1 , the first random waveform RW1 and the spread spectrum control signal SSC can be voltage, current or digital values, which can be used to indicate the corresponding switching frequency. In one embodiment, the middle of the first periodic waveform PW1 and the first random waveform RW1 The intermediate values correspond to the fundamental frequency Ff, and the intermediate value of the spread spectrum control signal SSC also corresponds to the fundamental frequency Ff, and the range of the switching frequency is Δf.

FIG. 9 is a schematic diagram showing an embodiment of the first periodic waveform and the first random waveform and the generated spread spectrum control signal according to another embodiment of the present invention. In one embodiment, as shown in FIG. 9, the first periodic waveform PW1 generated by the first periodic waveform generator can be a sawtooth waveform, and the first random waveform RW1 generated by the first random waveform generator can be a virtual random waveform. waveform. The first periodic waveform PW1 and the first random waveform RW1 are randomly added or subtracted by the addition and subtraction unit according to the control switching signal CS1 to generate spread spectrum control signals as shown in FIG. 9 . It can be seen from FIG. 9 that the spread-spectrum control signal generated in this embodiment has both the characteristics of a part of a sawtooth wave and part of a characteristic of a pseudo-random waveform.

FIG. 10 shows an embodiment of the first cycle waveform according to yet another embodiment of the present invention. As shown in FIG. 10 , the first periodic waveform generated by the first periodic waveform generator can also be a sine wave. As mentioned above, similarly, the sine wave and the virtual random waveform generated by the first random waveform generator can be randomly added or subtracted by the addition and subtraction unit 134 to generate the spread spectrum control signal SSC.

FIG. 11A shows a comparison between the power spectrum of an unmodulated narrowband interfering signal and the spectrum spread down to the lower frequency band according to an embodiment of the present invention. 11B shows a comparison between the power spectrum of an unmodulated narrowband interfering signal and the spectrum spread out from the center, according to one embodiment of the present invention. According to the CISPR 25 standard, the electromagnetic interference measurement is carried out with a bandwidth resolution of 9kHz in the frequency band of 150kHz~30MHz, and with a bandwidth resolution of 120kHz in the frequency band of 30MHz~1GHz. As is well known in the art, periodic analog spread spectrum (periodic analog spread spectrum) has a better performance for reducing the peak energy in the frequency band of 150kHz~30MHz. In addition, based on the Carlson bandwidth rule, the periodic analog spread spectrum can modify the switching frequency range △f to improve the suppression effect. On the other hand, frequency hopping spread spectrum (frequency hopping spread spectrum) technology will randomly change the frequency, so Not affected by the 120kHz bandwidth resolution limitation. Therefore, the frequency hopping spread spectrum technology can have better performance in reducing the peak energy of the 30MHz~1GHz frequency band.

The spread-spectrum switchable power conversion circuit of the present invention randomly adds or subtracts two different spread-spectrum techniques. The spread-spectrum switching power conversion circuit of the present invention can not only maintain its own characteristics, but also bring about the performance of reducing electromagnetic interference in the 150kHz~1GHz frequency band. In addition, as mentioned above, the spread spectrum switching power conversion circuit of the present invention can also use the sampling control circuit to sample the first random waveform RW1 at different sampling periods n, so as to achieve different EMI reduction performance.

FIG. 13 is a block diagram showing a clock generation circuit and a circuit block diagram of a spread spectrum control circuit (clock generator circuit 1415, spread spectrum control circuit 1413) according to a more specific embodiment of the present invention. In one embodiment, as shown in FIG. 13 , the spread spectrum control circuit 1413 includes a first periodic waveform generator 131, a first random waveform generator 132, and a computing unit 438. In one embodiment, the computing unit 438 includes a sampling synchronization circuit 137 and adding unit 135 .

In this embodiment, the first random waveform generator 132 is used to generate the first random waveform RW1 according to the first clock signal CLK1. In this embodiment, the first clock signal CLK1 is correspondingly coupled to the spread spectrum clock signal CKSW, In other words, the first clock signal CLK1 is the spread spectrum clock signal CKSW. The first periodic waveform generator 131 is used for generating the first periodic waveform PW1 according to the second clock signal CLK2 (eg, coupled from a system clock CKSYS). The calculation unit 438 is used for calculating the first random waveform RW1 and the first periodic waveform PW1 to generate the spread spectrum control signal SSC. For the details of the first cycle waveform generator 131 , please refer to FIGS. 7A-7B and related descriptions.

In one embodiment, the first periodic waveform PW1 is, for example, a triangular wave (as shown in FIG. 8 ), a sawtooth wave (as shown in FIG. 9 ) or a sine wave (as shown in FIG. 10 ). In one embodiment, the first random waveform RW1 is, for example, a random staircase waveform. In one embodiment, the first random waveform RW1 is, for example, a pseudo random staircase wave.

It should be noted that, in one embodiment, the first clock signal CLK1 and the second clock signal CLK2 are independent clock signal sources from different sources. Specifically, the first clock signal CLK1 is coupled to The self-spreading clock signal CKSW has the characteristic of spreading. On the other hand, the second clock signal CLK2 (system clock CKSYS) may not have the characteristic of spreading.

In this embodiment, the sampling synchronization circuit 137 is used to sample the first periodic waveform PW1 based on the first clock signal CLK1 (spread spectrum clock signal CKSW) to generate the sampled periodic waveform PW1', thereby making the sampled periodic waveform PW1 'can be synchronized with the sampling frequency of the first random waveform RW1, and then the adding unit 135 is used to add the sampled periodic waveform PW1' to the first random waveform RW1 to generate the spread spectrum control signal SSC, and the variable frequency oscillator 14 then It is used for generating the spread spectrum clock signal CKSW according to the spread spectrum control signal SSC.

From a point of view, the spread spectrum clock signal CKSW of this embodiment is fed back to the spread spectrum control circuit 1413 for controlling the spread spectrum characteristics to generate the spread spectrum control signal SSC, and then control the variable frequency oscillator 14 in a feedback manner Generate the spread spectrum clock signal CKSW, thereby making the spread spectrum effect better.

FIG. 14 is a block diagram showing a clock generation circuit and a circuit block diagram of a spread spectrum control circuit (clock generation circuit 1515, spread spectrum control circuit 1513) according to a more specific embodiment of the present invention. This embodiment is similar to the embodiment shown in FIG. 13 , wherein the computing unit 538 in the spread spectrum control circuit 1513 further includes a sampling control circuit 136 for down-sampling the first random waveform RW1 to generate a down-frequency random waveform RW1' 6, its operation can refer to the related description of FIG. 6. In this embodiment, the adding unit 135 is used to add the sampled periodic waveform PW1' and the down-frequency random waveform RW1' to generate the spread spectrum control signal SSC.

Fig. 15 is a block diagram showing a clock generation circuit and a circuit block diagram of a spread spectrum control circuit (clock generation circuit 1615, spread spectrum control circuit 1613) according to a more specific embodiment of the present invention. This embodiment is similar to the embodiment of Fig. 14, wherein the operation unit in the spread spectrum control circuit 1613 Element 638 further includes a frequency dividing unit 139, which is used to add the sampled periodic waveform PW1' to the down-frequency random waveform RW1' to generate the spread-spectrum control signal SSC', and then down-frequency it by m times to generate the spread-spectrum control signal SSC , and further control the variable frequency oscillator 14 to generate the spread spectrum clock signal CKSW, wherein m is a positive integer. In one embodiment, the sampling control circuit 136 as shown in FIG. 15 can be omitted, and the sampled periodic waveform PW1' is directly added to the first random waveform RW1 to generate the spread spectrum control signal SSC'.

Fig. 16 is a block diagram showing a clock generation circuit and a circuit block diagram of a spread spectrum control circuit (clock generator circuit 1715, spread spectrum control circuit 1713) according to a more specific embodiment of the present invention. This embodiment is similar to the embodiment shown in FIG. 15 , wherein the computing unit 738 in the spread spectrum control circuit 1713 further includes a control signal generator 133 , and the adding unit 135 is replaced by an adding and subtracting unit 134 . The control signal generator 133 is used to generate the control switching signal CS1, wherein the control switching signal CS1 has a random property, and its generation method can refer to the embodiment in FIG. 5 . In this embodiment, the addition and subtraction unit 134 is used to randomly add or subtract the sampled periodic waveform PW1' and the down-frequency random waveform RW1' according to the control switching signal CS1, so as to generate the spread spectrum control signal SSC'. In this embodiment, the control signal generator 133 generates the control switching signal CS1 with a random property according to the basic clock signal BC. It should be noted that the first clock signal CLK1 used to generate the first random waveform RW1 is different and independent from the clock signal (eg BC) used to generate the control switching signal CS1.

In addition, in one embodiment, the sampling control circuit 136 as shown in FIG. 16 can be omitted, and the sampled periodic waveform PW1' is directly added to the first random waveform RW1 to generate the spread spectrum control signal SSC'. In one embodiment, the frequency division unit 139 as shown in FIG. 16 can be omitted, and the operation result of the addition and subtraction unit 134 is directly used as the spread spectrum control signal SSC.

Fig. 17 is a comparison table showing the measurement results of spread spectrum modulation methods with different waveform combinations corresponding to Fig. 5 and Fig. 6, wherein the input power supply Vin is 7V, the output current Iout is 2A, and the switching frequency Fsw is 2.1MHz. The output power supply Vout is 5.2V, and the switching frequency variation range △f is ±6%. It can be seen from Fig. 17 that the spread spectrum switching power conversion circuit of the present invention mixes two different spread spectrum techniques, For example, but not limited to, the triangular wave mixed virtual random waveform, the sawtooth wave mixed virtual random waveform, the triangular wave mixed virtual random waveform with a sampling period of 8, and the sawtooth wave mixed virtual random waveform with a sampling period of 8 as shown in Figure 17 can all make spread spectrum The effect is better than using a single spread spectrum technology (such as virtual random waveform) and can expand the applicable frequency range of spread spectrum.

As mentioned above, the spread spectrum switching power conversion circuit/spread spectrum control method of the present invention can improve the spread spectrum effect and expand the applicable frequency range of spread spectrum by mixing two different spread spectrum technologies, and the sampling control circuit Controlling the sampling period of the first random waveform generator can further enhance the spread spectrum effect.

The present invention has been described above with reference to preferred embodiments, but the above description is only for making those skilled in the art easily understand the content of the present invention, and is not intended to limit the scope of rights of the present invention. The various embodiments described are not limited to single application, and can also be used in combination. For example, two or more embodiments can be used in combination, and some components in one embodiment can also be used to replace another embodiment. corresponding components. In addition, under the same spirit of the present invention, those skilled in the art can think of various equivalent changes and various combinations. For example, the term "processing or computing according to a certain signal or generating a certain output result" in the present invention is not limited to According to the signal itself, it also includes performing voltage-to-current conversion, current-to-voltage conversion, and/or ratio conversion on the signal when necessary, and then processing or computing the converted signal to generate a certain output result. It can be seen that under the same spirit of the present invention, those skilled in the art can think of various equivalent changes and various combinations, and there are many combinations, which will not be listed here. Accordingly, the scope of the invention should encompass the above and all other equivalent variations.

131: The first cycle waveform generator

132: The first random waveform generator

135: Addition unit

137: Sampling synchronization circuit

14: Variable Frequency Oscillator

1413: spread spectrum control circuit

1415: clock generation circuit

438: Arithmetic unit

CLK1, CLK2: clock signal

CKSYS: system clock

CKSW: Spread spectrum clock signal

SSC: spread spectrum control signal

PW1, PW1': periodic waveform

RW1: the first random waveform

Claims (33)

A spread-spectrum switching power conversion circuit, comprising: a variable-frequency oscillator, used to generate a spread-spectrum clock signal with spread-spectrum according to a spread-spectrum control signal, wherein the spread-spectrum clock signal has a fundamental frequency, And under the control of the spread spectrum control signal, it has a switching frequency range; a spread spectrum control circuit, which is used to generate the spread spectrum control signal according to a first clock signal and a second clock signal; and a pulse A wide modulation (PWM, Pulse Width Modulation) circuit is used to generate a switching signal with spread frequency according to a feedback signal based on the spread frequency clock signal; wherein the switching signal is used to control a power stage circuit, the power The stage circuit includes an inductor and at least one power switch coupled to each other, and is used to switch the power switch according to the switching signal with spread frequency to perform power conversion to generate an output power, wherein the feedback signal is related to the Output power supply; wherein the spread spectrum control circuit includes: a first periodic waveform generator, which is used to generate a periodic first periodic waveform according to the second clock signal; a first random waveform generator, which is used to generate a periodic waveform according to the The first clock signal generates a first random waveform with randomness; and an operation unit is used for sampling the first random waveform and the first periodic waveform, and performing operations to generate the spread spectrum control signal. The spread-spectrum switching power conversion circuit according to Claim 1, wherein the first periodic waveform is a triangular wave, a sawtooth wave or a sine wave. The spread-spectrum switching power conversion circuit according to Claim 1, wherein the first random waveform is a pseudo-random ladder wave. The spread-spectrum switching power conversion circuit as described in claim 1, wherein the first cycle waveform generator includes an up-down counter or a look-up table circuit, which is used for counting or look-up table respectively according to the second clock signal way to generate the first periodic waveform. The spread frequency switching power conversion circuit as described in claim 1, wherein: the first clock signal is the spread frequency clock signal, and the first random waveform is generated in a feedback manner, wherein the first clock signal The second clock signal comes from a different source and is independent of each other; the computing unit includes: a sampling synchronization circuit for sampling the first periodic waveform based on the first clock signal to generate a sampled periodic waveform, thereby making the sampled periodic waveform synchronized with a sampling frequency of the first random waveform; and an operator unit for generating the spread spectrum according to the sum of the sampled periodic waveform and a signal related to the first random waveform control signal. The spread spectrum switching power conversion circuit as described in claim 5 is characterized by one of the following: (1) wherein the operator unit is used to generate the spread spectrum according to the sum of the sampled periodic waveform and the first random waveform or (2) the computing unit further includes a sampling control circuit for down-sampling the first random waveform to generate a down-frequency random waveform, wherein the computing sub-unit is used to The sum of the periodic waveform and the down-frequency random waveform generates the spread spectrum control signal. The spread-spectrum switching power conversion circuit as described in claim 5, wherein the operation unit further includes a frequency division unit, wherein the operation sub-unit is related to the cycle waveform after sampling according to The sum of the signals of the first random waveform generates a pre-spread control signal, wherein the frequency dividing unit down-converts the pre-spread control signal by m times to generate the spread control signal, wherein m is a positive integer. The spread-spectrum switching power conversion circuit as described in claim 5, wherein the computing unit further includes a control signal generator for generating a control switching signal with random properties, wherein the computing sub-unit is based on the control switching signal to Randomly add or subtract the sampled periodic waveform to the signal related to the first random waveform to generate an operation result, and generate the spread spectrum control signal according to the operation result. The spread-spectrum switching power conversion circuit as described in Claim 1, wherein the calculation unit includes: a control signal generator for generating a control switching signal, wherein the control switching signal has randomness; and an operation sub-unit, It is used for randomly adding or subtracting the first periodic waveform and a signal related to the first random waveform based on the control switching signal to generate an operation result, and generating the spread spectrum control signal according to the operation result. The spread frequency switching power conversion circuit as described in claim 9, wherein the spread frequency control circuit further includes a sampling control circuit for down-sampling the first random waveform to generate a down-frequency random waveform, wherein The operation subunit is used for randomly adding or subtracting the first periodic waveform and the down-frequency random waveform based on the control switching signal to generate the operation result, and to generate the spreading control signal according to the operation result. The spread spectrum switching power conversion circuit as described in claim 9, wherein the first clock signal used to generate the first random waveform is different and independent from a clock signal used to generate the control switching signal. A clock generation circuit for generating a spread frequency clock signal with spread frequency according to a first clock signal and a second clock signal, wherein the spread frequency clock signal has a fundamental frequency and a Switching frequency range; the clock generation circuit includes: a variable frequency oscillator, used to generate the spread frequency clock signal with spread frequency according to a spread frequency control signal; and a spread frequency control circuit, used to generate the spread frequency clock signal according to the spread frequency control signal The first clock signal and the second clock signal generate the spread spectrum control signal; wherein the spread spectrum control circuit includes: a first periodic waveform generator, which is used to generate a periodic waveform according to the second clock signal A first periodic waveform; a first random waveform generator, used to generate a first random waveform with randomness according to the first clock signal; and an arithmetic unit, used to sample the first random waveform and the first random waveform The periodic waveform is calculated to generate the spread spectrum control signal. The clock generator circuit according to claim 12, wherein the first periodic waveform is a triangular wave, a sawtooth wave or a sine wave. The clock generating circuit as claimed in claim 12, wherein the first random waveform is a pseudo-random staircase wave. The clock generating circuit as described in claim item 12, wherein the first periodic waveform generator includes an up-down counter or a look-up table circuit, which is used to generate the first cycle waveform. The clock generation circuit as described in claim 12, wherein: the first clock signal is the spread frequency clock signal, and the first random waveform is generated by feedback, wherein the first clock signal and the second clock signal The two clock signals come from different sources and are independent of each other; The operation unit includes: a sampling synchronous circuit, which is used to sample the first periodic waveform based on the first clock signal to generate a sampled periodic waveform, thereby making the sampled periodic waveform synchronized with the first random waveform A sampling frequency; and an operation subunit, used to generate the spread spectrum control signal according to the sum of the sampled periodic waveform and a signal related to the first random waveform. The clock generation circuit as described in claim 16 is characterized by one of the following: (1) wherein the operator unit is used to generate the spread spectrum control signal according to the sum of the sampled periodic waveform and the first random waveform ; or (2) the computing unit further includes a sampling control circuit for down-sampling the first random waveform to generate a down-frequency random waveform, wherein the computing sub-unit is used for the periodic waveform and the The sum of the down-frequency random waveforms generates the spread-spectrum control signal. The clock generating circuit as described in claim 16, wherein the operation unit further includes a frequency division unit, wherein the operation subunit generates a signal according to the sum of the sampled periodic waveform and the signal related to the first random waveform The pre-spread control signal, wherein the frequency dividing unit reduces the frequency of the pre-spread control signal by m times to generate the spread control signal, wherein m is a positive integer. The clock generating circuit as described in claim 16, wherein the operation unit further includes a control signal generator for generating a control switching signal with random properties, wherein the operation sub-unit samples the sample based on the control switching signal The latter cycle waveform is randomly added or subtracted to the signal related to the first random waveform to generate an operation result, and the spread spectrum control signal is generated according to the operation result. The clock generating circuit as described in claim 12, wherein the computing unit includes: a control signal generator for generating a control switching signal, wherein the control switching signal has randomness; and An operation subunit, used for randomly adding or subtracting the first periodic waveform and a signal related to the first random waveform based on the control switching signal to generate an operation result, and generate the operation result according to the operation result Spread spectrum control signal. The clock generation circuit as described in claim 20, wherein the spread spectrum control circuit further includes a sampling control circuit for down-sampling the first random waveform to generate a down-frequency random waveform, wherein the operator The unit is used for randomly adding or subtracting the first cycle waveform and the down-frequency random waveform based on the control switching signal to generate the operation result, and generate the spreading control signal according to the operation result. The clock generating circuit according to claim 20, wherein the first clock signal used to generate the first random waveform is different and independent from a clock signal used to generate the control switching signal. A clock generation method for generating a spread frequency clock signal with spread frequency according to a first clock signal and a second clock signal, wherein the spread frequency clock signal has a fundamental frequency and a Switching frequency variation range; the clock generation method includes: generating the spread spectrum clock signal with spread spectrum according to a spread spectrum control signal; and generating the spread spectrum clock signal according to the first clock signal and the second clock signal Control signal; wherein the step of generating the spread spectrum control signal includes: generating a periodic first periodic waveform according to the second clock signal; generating a first random waveform with randomness according to the first clock signal; And sampling the first random waveform and the first periodic waveform, and calculating them to generate the spread spectrum control signal. The clock generation method as claimed in claim 23, wherein the first periodic waveform is a triangular wave, a sawtooth wave or a sine wave. The clock generation method as claimed in claim 23, wherein the first random waveform is a pseudo-random staircase wave. The clock generating method according to claim 23, wherein the step of generating the periodic first periodic waveform includes: generating the first periodic waveform by counting or looking up a table according to the second clock signal. The clock generation method as described in Claim 23, wherein: the first clock signal is the spread frequency clock signal, and the first random waveform is generated by feedback, wherein the first clock signal and the second clock signal The two clock signals come from different sources and are independent of each other; wherein the step of generating the spread spectrum control signal includes: sampling the first periodic waveform based on the first clock signal to generate a sampled periodic waveform, thereby making the sampled The periodic waveform is synchronized with a sampling frequency of the first random waveform; and the spreading control signal is generated according to the sum of the sampled periodic waveform and a signal related to the first random waveform. The clock generation method as described in claim 27 is characterized by one of the following: (1) generating the spread spectrum control signal according to the sum of the sampled periodic waveform and the first random waveform; or (2) The first random waveform is down-sampled to generate a down-frequency random waveform, and the spreading control signal is generated according to the sum of the sampled periodic waveform and the down-frequency random waveform. The clock generation method as described in claim 27, wherein the step of generating the spread spectrum control signal further includes: generating a pre-spread spectrum control signal according to the sum of the sampled periodic waveform and the signal related to the first random waveform signal, and down-convert the pre-spread control signal by m times to generate the spread control signal, wherein m is a positive integer. The clock generation method as described in claim 27, wherein the step of generating the spread spectrum control signal further includes: generating a control switching signal with a random property; and based on the control switching signal to correlate the sampled periodic waveform with The signal of the first random waveform is randomly added or subtracted to generate an operation result, and the spread spectrum control signal is generated according to the operation result. The clock generation method as described in claim 23, wherein the step of generating the spread spectrum control signal includes: generating a control switching signal, wherein the control switching signal has randomness; and based on the control switching signal to the first period The waveform is randomly added or subtracted to a signal related to the first random waveform to generate an operation result, and the spread spectrum control signal is generated according to the operation result. The clock generation method as described in claim 31, wherein the step of generating the spread spectrum control signal further includes: down-sampling the first random waveform to generate a down-frequency random waveform; and based on the control switching signal to Randomly add or subtract the first cycle waveform and the down-frequency random waveform to generate the operation result, and generate the spread spectrum control signal according to the operation result. The clock generation method according to claim 31, wherein the first clock signal used to generate the first random waveform is different and independent from a clock signal used to generate the control switching signal.

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