WO2020199804A1

WO2020199804A1 - Switching power supply system employing hysteretic mode control

Info

Publication number: WO2020199804A1
Application number: PCT/CN2020/076936
Authority: WO
Inventors: 马忠亮
Original assignee: 无锡职业技术学院
Priority date: 2019-04-02
Filing date: 2020-02-27
Publication date: 2020-10-08
Also published as: CN109861527A; CN109861527B

Abstract

The present application relates to the field of switching power supply, and discloses a switching power supply system employing hysteretic mode control. In the switching power supply system, an error amplifier has a hysteretic design at a later stage thereof, and outputs COMP, which is an amplified signal obtained from a sampling signal of VOUT and a reference voltage, such that an output signal feedback node FB has a reduced amount of operating hysteresis, thereby achieving small output signal ripples. Moreover, a triangular wave signal Ramp is generated by a triangular wave generation circuit, and undergoes a hysteretic comparison with the COMP output by the error amplifier. A slope of the triangular wave signal Ramp is basically unrelated to the voltage at a sampling commutation point SW, such that the operating frequency of the system is mostly unrelated to output current load. The system also has fast transient response speed, and the operating frequency thereof is less affected by system inputs and outputs.

Description

A switching power supply system based on hysteresis mode control

Technical field

The invention relates to the field of switching power supplies, in particular to a switching power supply system based on hysteresis mode control.

Background technique

When the digital logic IC is working, it needs the system front-end DC-DC switching power supply to supply it. As the semiconductor process enters the nano-era, the chip area of the digital logic IC is continuously reduced, the working voltage is continuously reduced, and the working clock frequency is continuously increased. Therefore, more and more stringent requirements are put forward for the DC-DC switching power supply of the front stage of the digital logic IC system. The DC-DC switching power supply is required to have a smaller PCB area, higher switching frequency and conversion efficiency, and faster Transient response and lower output voltage ripple.

The switching power supply of hysteresis control mode is more and more commonly used in switching power supply products due to its simple compensation and high working frequency. The proposed switching power supply system based on the hysteresis control mode has the method of forcibly injecting a sampling commutation point (SW) voltage into the system output voltage feedback FB node to form a triangular wave signal, and then making a hysteresis comparison with the reference voltage Vref, see patent number US6147478 However, when the system is under heavy load, the pressure drop at the sampling commutation point causes the system to have inconsistent slopes of the injected signal under light and heavy loads, resulting in the system operating frequency changing with the load, and the system The output voltage ripple is still too large. There is also a method of sampling the inductor current ripple information through the RC network to form a triangular wave signal, and then compare the hysteresis with the COMP signal of the feedback voltage FB after the error amplifier EA. Refer to the patent number US8866450B2, but this method is in A separate transconductance amplifier is required in the system, and an RC network must be connected in parallel to both ends of the inductor, which increases the complexity of the system design.

Summary of the invention

technical problem

The patent number US6147478 provides a method when the system is under heavy load due to the decrease of the pressure drop at the sampling commutation point, which leads to the inconsistent slope of the signal injected into the system under light and heavy loads, which causes the system operating frequency to vary with the load, and the system The output voltage ripple is still too large. Another approach provided by the patent number US8866450B2 requires a separate transconductance amplifier in the system, and an RC network must be connected in parallel to both ends of the inductor, which increases the complexity of the system design.

The solution to the problem

Technical solutions

A switching power supply system based on hysteresis mode control. The switching power supply system includes a series circuit composed of an upper arm MOS switch and a lower arm MOS switch. One end of the series circuit is connected to the system input end of the switching power supply system and the other end is grounded. The upper arm MOS switch and The common end of the lower arm MOS switch is used as the sampling commutation point to connect to the output end of the switching power supply system through an inductor. The output end of the system is also connected to the first resistor, the first capacitor, and the second capacitor. The other end of the second capacitor is grounded. A resistor is connected to the other end of the first capacitor and then grounded through a second resistor. The common end of the first resistor and the second resistor is connected to the inverting input terminal of the error amplifier. The non-inverting input terminal of the error amplifier inputs the reference signal. The output terminal is connected to the hysteresis comparator circuit, the output terminal of the error amplifier is also connected to the compensation capacitor and the compensation resistor in turn, and then grounded. The error amplifier generates an error signal according to the input signal and outputs it to the hysteresis comparator circuit;

The input terminal of the voltage sampling circuit obtains the sampling signal, and the output terminal is connected to the input terminal of the triangle wave generating circuit. The voltage sampling circuit is used to generate a bias voltage according to the sampling signal and output it to the triangle wave generating circuit. The sampling signal is a fixed signal or the sampling signal is a reaction sampling The variable signal of the information characteristic of the signal at the commutation point; the triangle wave generating circuit includes a series circuit composed of a first switch and a second switch. One end of the series circuit is connected to the working voltage and the other end is grounded. The first switch and the second switch are common The third resistor and the third capacitor are sequentially connected to the third resistor and the third capacitor. The other end of the third capacitor is used as the input terminal of the triangle wave generating circuit to connect to the voltage sampling circuit, and the common terminal of the third resistor and the third capacitor is used as the output terminal of the triangle wave generating circuit to connect hysteresis Comparator circuit, the triangular wave generating circuit is used to generate a triangular wave signal according to the bias voltage and the control signal of the first switch and the control signal of the second switch and output it to the hysteresis comparator circuit; the output terminal of the hysteresis comparator circuit is connected to the logic control circuit At the input, the hysteresis comparator circuit is used to compare the error signal and the triangle wave signal according to the input first control signal to generate a modulated wave signal and output it to the logic control circuit. The logic control circuit logically processes the modulated wave signal to generate the upper arm The drive signal, the lower arm drive signal, the first control signal, the second control signal and the third control signal. The upper arm drive signal is opposite to the lower arm drive signal. The first control signal, the second control signal and the third control signal are coupled to the upper arm drive signal. , The lower arm drive signal has the same frequency as the upper and lower arm drive signals, the upper arm drive signal is used to drive the upper arm MOS switch, the lower arm drive signal is used to drive the lower arm MOS switch, and the first control signal is used as the control signal of the hysteresis comparator circuit Output to the hysteresis comparator circuit, the second control signal is output to the triangle wave generating circuit as the control signal of the first switch, and the third control signal is output to the triangle wave generating circuit as the control signal of the second switch.

A further technical solution is that the hysteresis comparator circuit includes a hysteresis generating circuit and a comparator, the input of the comparator is respectively connected to the output of the error amplifier and the output of the triangle wave generating circuit, and the output of the comparator is used as the hysteresis comparator circuit The output terminal is connected to the logic control circuit, and the first control signal generated by the logic control circuit is output to the hysteresis generating circuit; the hysteresis generating circuit is arranged at the output terminal of the error amplifier and generates a hysteresis signal to the error signal according to the first control signal, or the hysteresis generating circuit It is arranged at the output terminal of the triangle wave generating circuit and generates a hysteresis signal to the triangle wave signal according to the first control signal.

The further technical solution is that when the hysteresis generating circuit is arranged at the output terminal of the error amplifier, the hysteresis generating circuit is arranged between the output terminal of the error amplifier and the input terminal of the comparator, or the hysteresis generating circuit is arranged at two ends of the compensation resistor. end;

When the hysteresis generating circuit is arranged at the output terminal of the triangle wave generating circuit, the hysteresis generating circuit is arranged between the output terminal of the triangle wave generating circuit and the input terminal of the comparator.

The further technical solution is that when the hysteresis generating circuit is arranged between the output terminal of the error amplifier and the input terminal of the comparator, or the hysteresis generating circuit is arranged between the output terminal of the triangular wave generating circuit and the input terminal of the comparator, The hysteresis generating circuit includes:

A first series circuit composed of a first current source, a first hysteresis switch, a second hysteresis switch, and a second current source, and a first series circuit composed of a third current source, a second hysteresis switch, a first hysteresis switch, and a fourth current source Two series circuits. The positive poles of the first series circuit and the second series circuit are respectively connected to the working voltage, and the negative poles are respectively grounded. One end of the hysteresis resistance is connected to the common end of the first and second hysteresis switches in the first series circuit. The hysteresis resistance The other end of is connected to the common end of the first hysteresis switch and the second hysteresis switch in the second series circuit, and the common end of the first hysteresis switch and the second hysteresis switch in the first series circuit is used as the input end of the hysteresis generating circuit. Connection error The output terminal of the amplifier or the triangular wave generating circuit, the common terminal of the first hysteresis switch and the second hysteresis switch in the second series circuit is connected to the comparator as the output terminal of the hysteresis generating circuit; the first hysteresis switch and the second hysteresis switch in the first series circuit The first hysteresis switch in the two series circuits is controlled by the same control signal. The second hysteresis switch in the first series circuit and the second hysteresis switch in the second series circuit are controlled by the same control signal. The first hysteresis switch is controlled by the same control signal. The signal and the control signal of the second hysteresis switch are both coupled to the first control signal and the two control signals are opposite.

A further technical solution is that when the hysteresis generating circuit is arranged between the output terminal of the error amplifier and the input terminal of the comparator, the hysteresis generating circuit includes:

A series circuit composed of a current source, a second hysteresis switch, and a first hysteresis switch. The positive pole of the series circuit is connected to the working voltage and the negative pole is grounded. The common end of the second hysteresis switch and the first hysteresis switch is used to connect the compensation capacitor and the compensation resistor. At the end, the control signal of the first hysteresis switch and the control signal of the second hysteresis switch are both coupled to the first control signal and the two control signals are opposite.

A further technical solution is that the input terminal of the voltage sampling circuit is connected to a fixed voltage, and the sampling signal obtained by the voltage sampling circuit is a fixed voltage; or the input terminal of the voltage sampling circuit is coupled to the sampling commutation point, and the voltage sampling circuit obtains The sampling signal is the signal at the sampling commutation point; or, the input terminal of the voltage sampling circuit is connected to the logic control circuit, and the sampling signal obtained by the voltage sampling circuit includes the fourth control signal and the fifth control signal output by the logic control circuit. The control signal and the fifth control signal are coupled to the upper and lower arm drive signals, and the fourth control signal and the fifth control signal are opposite.

The further technical solution is that when the input terminal of the voltage sampling circuit is directly coupled to the sampling commutation point, the voltage sampling circuit includes: an RC filter circuit composed of a filter resistor and a filter capacitor, and the input terminal of the RC filter circuit is used as the voltage sampling circuit The input terminal is coupled to the sampling commutation point, and the output terminal of the RC filter circuit is connected to the output terminal of the voltage sampling circuit through a buffer.

A further technical solution is that when the input terminal of the voltage sampling circuit is connected to the logic control circuit, the voltage sampling circuit includes:

A series circuit composed of the first sampling switch and the second sampling switch. One end of the series circuit is connected to the working voltage and the other end is grounded. The common end of the first sampling switch and the second sampling switch is connected to the RC filter circuit composed of a filter resistor and a filter capacitor. Input terminal, the output terminal of the RC filter circuit is connected to the output terminal of the voltage sampling circuit through the buffer; the fourth control signal output by the logic control circuit is output to the voltage sampling circuit as the control signal of the first sampling switch, and the fifth control signal output by the logic control circuit The control signal is output to the voltage sampling circuit as a control signal of the second sampling switch.

A further technical solution is that the triangle wave generating circuit also includes a current generating circuit, the current generating circuit includes a first gain module, a second gain module, a divider and a voltage-current converter, and the input terminal of the first gain module is connected to the system input terminal , The input terminal of the second gain module is connected to the system output terminal, the output terminal of the first gain module and the output terminal of the second gain module are respectively connected to the two input terminals of the divider, and the output terminal of the divider is connected to the input of the voltage-current converter The output terminal of the voltage-current converter is connected to the output terminal of the triangle wave generating circuit as the output terminal of the current generating circuit.

The beneficial effects of the invention

Beneficial effect

This application discloses a switching power supply system based on hysteresis mode control. In the switching power supply system, the hysteresis design exists in the rear stage of the error amplifier. The output COMP is the sampling signal of VOUT and the amplified signal of the reference voltage, so the output The working hysteresis of the signal feedback node FB is small, so that a small output signal ripple can be realized; at the same time, the triangular wave signal Ramp, which is compared with the COMP output by the error amplifier, is generated by the triangular wave generating circuit. The slope of the triangular wave signal Ramp is exchanged with the sample The phase point SW voltage is basically irrelevant, so the operating frequency of the system has a very small relationship with the output current load. At the same time, the system also has a faster transient response speed, and the operating frequency changes little with the system input and system output.

Brief description of the drawings

Description of the drawings

FIG. 1 is a circuit structure diagram of a switching power supply system based on hysteresis mode control disclosed in the present application.

Figure 2 is a circuit diagram of a triangle wave generating circuit.

Figure 3 is another circuit diagram of the triangle wave generating circuit.

FIG. 4 is a circuit configuration diagram when the hysteresis comparator circuit in FIG. 1 is composed of a hysteresis generating circuit and a comparator.

Fig. 5 is a circuit diagram of a hysteresis generating circuit in the circuit shown in Fig. 4.

Fig. 6 is an operating waveform diagram of the hysteresis generating circuit shown in Fig. 5.

FIG. 7 is another circuit configuration diagram when the hysteresis comparator circuit in FIG. 1 is composed of a hysteresis generating circuit and a comparator.

Fig. 8 is a circuit diagram of a hysteresis generating circuit in the circuit shown in Fig. 7.

Fig. 9 is an operating waveform diagram of the hysteresis generating circuit shown in Fig. 8.

FIG. 10 is another circuit configuration diagram when the hysteresis comparator circuit in FIG. 1 is composed of a hysteresis generating circuit and a comparator.

Fig. 11 is a specific circuit diagram when the voltage sampling circuit is directly coupled to the sampling commutation point.

FIG. 12 is a circuit configuration diagram when the voltage sampling circuit in FIG. 4 is changed to the configuration in which the logic control circuit is connected.

Figure 13 is a specific circuit diagram when the voltage sampling circuit is connected to the logic control circuit.

Fig. 14 is a working waveform diagram of the voltage sampling circuit shown in Fig. 13.

Figure 15 is a circuit diagram of a logic control circuit.

Fig. 16 is a working waveform diagram of the circuit structure shown in Fig. 4 in CCM mode.

Fig. 17 is a working waveform diagram of the circuit structure shown in Fig. 4 in DCM mode.

Fig. 18 is a working waveform diagram of the circuit structure shown in Fig. 10 in CCM mode.

Invention embodiment

Embodiments of the invention

The specific embodiments of the present invention will be further described below in conjunction with the drawings.

This application discloses a switching power supply system based on hysteresis mode control. Please refer to Figure 1. The switching power supply system includes a series circuit composed of an upper arm MOS switch S1 and a lower arm MOS switch S2. One end of the series circuit is connected to the switching power supply system. The input terminal VIN of the system and the other terminal are grounded. The common terminal of the upper arm MOS switch S1 and the lower arm MOS switch S2 is used as the sampling commutation point SW to connect to the system output terminal VOUT of the switching power supply system through the inductor L. The output terminal VOUT of the system is also connected to the first resistor R1, the first capacitor C1 and the second capacitor C2 respectively. The other end of the second capacitor C2 is grounded. The other end of the first resistor R1 and the first capacitor C1 is connected through the second resistor R2. Ground. The common terminal of the first resistor R1 and the second resistor R2 is connected to the inverting input terminal of the error amplifier EA, and this node is the output signal feedback node FB. The non-inverting input terminal of the error amplifier EA inputs the reference signal VREF, the output terminal of the error amplifier EA is connected to the hysteresis comparator circuit CMP, and the output terminal of the error amplifier EA is connected to the compensation capacitor C _C and the compensation resistor R _{C in turn and} then grounded. The error amplifier EA generates an error signal COMP according to the input VOUT feedback signal and the reference signal VREF and outputs it to the hysteresis comparator circuit CMP.

The input terminal of the voltage sampling circuit obtains the sampling signal Vpe, and the output terminal is connected to the input terminal of the triangle wave generating circuit. The voltage sampling circuit is used to generate the bias voltage VDP according to the sampling signal Vpe and output it to the triangle wave generating circuit. The triangle wave generating circuit is also connected to a logic control circuit. The logic control circuit is used to output the second control signal Sense2 and the third control signal Sense3 to the triangle wave generating circuit. The triangle wave generating circuit is used to generate the triangle wave according to the bias voltage VDP, the second control signal Sense2 and the third control signal. The control signal Sense3 generates a triangular wave signal Ramp and outputs it to the hysteresis comparator circuit CMP.

The output terminal of the hysteresis comparator circuit CMP is connected to the input terminal of the logic control circuit. The hysteresis comparator circuit CMP is also connected to the logic control circuit. The logic control circuit is used to output the first control signal Sense1 to the hysteresis comparator circuit CMP. The hysteresis comparator circuit CMP is used to perform hysteresis comparison between the error signal COMP and the triangular wave signal Ramp according to the input first control signal Sense1 to generate a modulated wave signal PWM and output it to the logic control circuit. The logic control circuit includes a series of conventional logic devices. The logic control circuit performs logic processing on the modulation wave signal PWM to generate the upper arm drive signal DRU, the lower arm drive signal DRL, the first control signal Sense1, the second control signal Sense2 and the third control The signal Sense3, the upper arm drive signal DRU and the lower arm drive signal DRL are opposite, the first control signal Sense1, the second control signal Sense2 and the third control signal Sense3 are coupled to the upper and lower arm drive signals so as to be the same as the upper arm drive signal DRU and the lower arm drive signal DRL At the same frequency, the second control signal Sense2 and the third control signal Sense3 are two non-overlapping clock signals. The coupling means that the upper arm drive signal DRU or the lower arm drive signal DRL is directly used, or the upper arm drive signal DRU or the lower arm drive signal DRL is obtained through a series of logic control, that is, the sampling of the upper arm drive signal DRU or the lower arm drive signal DRL is realized . The first control signal Sense1 is output as the control signal of the hysteresis comparator circuit CMP to the hysteresis comparator circuit CMP, the second control signal Sense2 and the third control signal Sense3 are output as the control signals of the triangle wave generating circuit to the triangle wave generating circuit, and the upper arm drive signal DRU It is used to drive the upper arm MOS switch S1, and the lower arm drive signal DRL is used to drive the lower arm MOS switch S2, so as to achieve a stable voltage output at the system output terminal VOUT.

Please refer to Figure 2 for a circuit diagram of the triangle wave generating circuit. The triangle wave generating circuit includes a series circuit composed of a first switch S3 and a second switch S4. One end of the series circuit is connected to the working voltage VCC and the other end is grounded. VCC can be a fixed voltage inside the system or the input voltage of the input terminal VIN of the system. The common ends of the first switch S3 and the second switch S4 are sequentially connected to the third resistor R _R and the third capacitor C _R , and the other end of the third capacitor C _R is used as the input end of the triangle wave generating circuit for connecting the voltage sampling circuit to obtain the bias Set the voltage VDP, the common end of the third resistor R _R and the third capacitor C _R is connected to the hysteresis comparator circuit CMP as the output end of the triangle wave generating circuit. The second control signal Sense2 and the third control signal Sense3 as the control signal of the triangle wave generating circuit are specifically: the second control signal Sense2 is used as the control signal of the first switch S3, and the third control signal Sense3 is used as the control signal of the second switch S4.

Please refer to FIG. 3 for another circuit diagram of the triangle wave generating circuit in this application. FIG. 3 adds a current generating circuit to the output terminal on the basis of the circuit shown in FIG. 2. The current generating circuit includes a first gain module k1, a second gain module k2, a divider DIVIDER, and a voltage-current converter V/R. The input terminal of the first gain module k1 is connected to the system input terminal VIN, and the input terminal of the second gain module k2 Connect the system output terminal VOUT, the output terminal of the first gain module k1 and the output terminal of the second gain module k2 are respectively connected to the two input terminals of the divider DIVIDER, and the output terminal of the divider DIVIDER is connected to the input of the voltage-current converter V/R The output terminal of the voltage-current converter V/R is connected to the output terminal of the triangle wave generating circuit as the output terminal of the current generating circuit. The current generating circuit is controlled by the signals of the system input terminal VIN and the system output terminal VOUT. The input signal VIN and the output signal VOUT are sampled and operated respectively through two gain modules, and then the relationship between VOUT divided by VIN is realized through the divider DIVIDER, and then by The voltage-current converter V/R converts into a current related to the voltage of the input signal VIN and the output signal VOUT to participate in the change of the rising and falling slopes of the triangular wave signal Ramp, so as to reduce the system operating frequency as the input signal VIN and the output signal VOUT change. The purpose of the change, in this way, the effect that its operating frequency is further independent of the input signal VIN and the output signal VOUT can be achieved. The current involved in changing the triangular wave signal Ramp is inversely proportional to the input signal VIN and proportional to the output signal VOUT. The formula is IB=k*VOUT/VIN, where k represents a constant.

Figure 1 is the overall circuit architecture of the switching power supply system disclosed in this application. In actual implementation, each part of the circuit in the circuit architecture of Figure 1 has multiple implementation modes:

1. Multiple implementations of hysteresis comparator circuit CMP.

The hysteresis comparator circuit CMP mainly has two implementation methods: the first method is to directly use a commercially available hysteresis comparator, and the second method is to use a hysteresis generating circuit and a comparator. The circuit structure of a commercially available hysteresis comparator is directly adopted as the circuit structure of FIG. 1, wherein the hysteresis comparator circuit CMP can select a suitable model according to actual needs, which will not be described in detail in this application. This application mainly explains the self-built situation. When the hysteresis comparator circuit CMP includes a hysteresis generating circuit and a comparator P, the input terminal of the comparator P is connected to the output terminal of the error amplifier EA and the output terminal of the triangle wave generating circuit respectively, and the output terminal of the comparator P serves as the hysteresis comparator circuit The output terminal is connected to the logic control circuit, and the first control signal Sense1 generated by the logic control circuit is output to the hysteresis generating circuit for control. There are mainly three specific settings for the hysteresis generating circuit:

1. Please refer to Figure 4. The hysteresis generating circuit is set at the output of the error amplifier, and the hysteresis generating circuit is set between the output of the error amplifier EA and the input of the comparator P. In this case, the hysteresis generating circuit Please refer to Figure 5 for the specific circuit diagram. The hysteresis generating circuit includes a first series circuit composed of a first current source IBP1, a first hysteresis switch Sh1, a second hysteresis switch Sh2, and a second current source IBP2, and a third current source IBP3, a second hysteresis switch Sh2, and a first series circuit. The second series circuit formed by the hysteresis switch Sh1 and the fourth current source IBP4. The positive poles of the first series circuit and the second series circuit are respectively connected to the working voltage VCC, and the negative poles are respectively grounded. The working voltage VCC is defined above. One end of the hysteresis resistor Rhyst is connected to the common end of the first hysteresis switch Sh1 and the second hysteresis switch Sh2 in the first series circuit, and the other end of the hysteresis resistor Rhyst is connected to the first hysteresis switch Sh1 and the second hysteresis switch in the second series circuit. The public end of Sh2. The common terminal of the first hysteresis switch Sh1 and the second hysteresis switch Sh2 in the first series circuit is used as the input terminal IN of the hysteresis generating circuit, and the common terminal of the first hysteresis switch Sh1 and the second hysteresis switch Sh2 in the second series circuit is used as the input terminal IN of the hysteresis generating circuit. The output terminal OUT of the hysteresis generating circuit. The first hysteresis switch Sh1 in the first series circuit and the first hysteresis switch Sh1 in the second series circuit are controlled by the same control signal. The second hysteresis switch Sh2 in the first series circuit and the second hysteresis switch Sh2 in the second series circuit are controlled by the same control signal. The hysteresis switch Sh2 is controlled by the same control signal. As shown in FIG. 5, the control signal of the first hysteresis switch Sh1 and the control signal of the second hysteresis switch Sh2 are both coupled to the first control signal Sense1 and the two control signals are opposite. The coupling means that the two control signals are directly obtained by the first control signal Sense1 or generated by the first control signal Sense1 through logic control. FIG. 5 takes the first control signal Sense1 as an example, and FIG. 5 only shows the pair Control diagram of two hysteresis switches.

For the signal waveform diagram of the hysteresis generating circuit shown in Figure 5, please refer to Figure 6. The hysteresis generating circuit drives a current through a set of control signals related to the upper and lower arm drive signals to flow through a hysteresis resistor Rhyst to obtain a hysteresis coupling to the IN terminal signal. The OUT end signal of the signal, Vhysteretic in Figure 6 represents the hysteresis signal coupled to the IN end signal. In this case, the input terminal IN of the hysteresis generating circuit is connected to the output terminal of the error amplifier EA, and the output terminal OUT of the hysteresis generating circuit is connected to the input terminal of the comparator P. Therefore, the hysteresis generating circuit generates a hysteresis signal which is input at the IN terminal. The lagging COMP signal obtained from the error signal COMP is output from the OUT terminal to the comparator P, and the comparator P compares the triangular wave signal Ramp with the lagging COMP to generate a modulation wave signal PWM.

In case 1, due to the hysteresis design and the output end of the error amplifier EA, the output end COMP is the amplified signal of the sampling signal of VOUT and the reference signal VREF, so the working hysteresis of the FB end is small, and the system output VOUT can achieve very Small ripples.

2. Please refer to Figure 7. As in case 1, the hysteresis generating circuit is also set at the output end of the error amplifier EA, but the hysteresis generating circuit is set at both ends of the compensation resistor R _C to hysteresize the COMP signal output by the error amplifier EA. The circuit diagram of the hysteresis generating circuit is shown in Figure 8. The hysteresis generating circuit includes a series circuit composed of a current source IBP, a second hysteresis switch Sh2, and a first hysteresis switch Sh1. The positive pole of the series circuit is connected to the working voltage VCC and the negative pole is grounded. The common end of the second hysteresis switch Sh2 and the first hysteresis switch Sh1 is used to connect the common end of the compensation capacitor C _C and the compensation resistor R _C. The control signal of the first hysteresis switch Sh1 and the control signal of the second hysteresis switch Sh2 are both coupled to the first control signal Sense1 and the two control signals are opposite. For the meaning of the coupling, refer to Case 1. Figure 8 only shows two control signals A kind of hint.

For the signal waveform diagram of the hysteresis generating circuit shown in Figure 8, please refer to Figure 9. A set of control signals related to the upper and lower arm drive signals drive a current to flow through the compensation resistor R _{C to} achieve the effect of coupling a hysteresis signal Vhysteretic to the COMP signal . In this case, the hysteresis generating circuit also generates a hysteresis signal on the error signal COMP, and the comparator P compares the triangular wave signal Ramp with the delayed COMP to generate the modulated wave signal PWM, but compared to the case 1, due to the hysteresis control The compensation resistor R _C is generated at both ends, the control is simpler, and the possibility of the COMP signal being interfered in the signal transmission process can be further reduced.

3. Please refer to Figure 10. Different from

cases

1 and 2, in case 3, the hysteresis generating circuit is set at the output terminal of the triangle wave generating circuit, specifically between the output terminal of the triangle wave generating circuit and the input terminal of the comparator P, In this case, the specific circuit diagram of the hysteresis generating circuit is the same as that of Figure 5, and the waveform diagram is the same as that of Figure 6, except that the input terminal IN of the hysteresis generating circuit shown in Figure 5 is connected to the output terminal and output terminal OUT of the triangular wave generating circuit. Connect the input terminal of the comparator P, the hysteresis generating circuit generates a hysteresis signal on the triangular wave signal Ramp input at the IN terminal to obtain the lagging triangular wave signal Ramp from the OUT terminal to the comparator P, and the comparator P responds to the error signal COMP and the hysteresis The triangular wave signal Ramp is compared to generate the modulated wave signal PWM. Compared with

cases

1 and 2, the hysteresis control in this case is at the Ramp end, which can reduce the interference of the COMP signal during signal generation.

2. There are several ways to realize the voltage sampling circuit, mainly as follows:

1. The sampling signal obtained by the voltage sampling circuit reflects the information characteristics of the signal at the sampling commutation point. There are two main cases:

1.1. The input terminal of the voltage sampling circuit is directly coupled to the sampling commutation point SW, as shown in Figures 4, 7 and 10, the sampling signal obtained by the voltage sampling circuit is the signal at the sampling commutation point SW. In this case, please refer to Figure 11 for the circuit diagram of the voltage sampling circuit. The voltage sampling circuit includes an RC filter circuit composed of a filter resistor RF and a filter capacitor CF. The input of the RC filter circuit is directly coupled to the sampling commutation point as the input of the voltage sampling circuit. SW, the output terminal of the RC filter circuit is connected to the output terminal of the voltage sampling circuit through the buffer to output the bias voltage VDP. In this case, the voltage sampling circuit generates the bias voltage VDP according to the signal at the sampling commutation point SW It has the same information characteristics as the signal at the sampling commutation point SW. In this case, the slope of the triangular wave signal Ramp is basically independent of the size of the sampling commutation point SW, so the system operating frequency has a very small relationship with the output current load.

1.2. The input terminal of the voltage sampling circuit is not directly coupled to the sampling commutation point SW, but is connected to the logic control circuit. Please refer to Figure 12, which is a circuit structure obtained by changing the voltage sampling circuit on the basis of Figure 4. In this case, the sampling signal obtained by the voltage sampling circuit includes the fourth control signal Sense4 and the fifth control signal Sense5 output by the logic control circuit. The fourth control signal Sense4 and the fifth control signal Sense5 are both coupled to the upper and lower control signals. The arm drive signal and the fourth control signal Sense4 are opposite to the fifth control signal Sense5. The meaning of coupling is as above. Since the fourth control signal Sense4 and the fifth control signal Sense5 sample the upper arm drive signal DRU and the lower arm drive signal DRL respectively, the sampling signal obtained by the voltage sampling circuit reflects the information characteristics of the signal at the sampling commutation point SW, and the voltage sampling The bias voltage VDP generated by the circuit according to the sampling signal also has the same information characteristics as the signal at the sampling commutation point SW.

Please refer to Figure 13 for the voltage sampling circuit in this case. The voltage sampling circuit includes a series circuit composed of a first sampling switch S5 and a second sampling switch S6. One end of the series circuit is connected to the working voltage VCC and the other end is grounded. The common terminal of the S5 switch and the second sampling switch S6 is connected to the input terminal of the RC filter circuit formed by the filter resistor RF and the filter capacitor CF, and the output terminal of the RC filter circuit is connected to the output terminal of the voltage sampling circuit through the buffer to output the bias voltage VDP. The fourth control signal Sense4 output by the logic control circuit is output to the voltage sampling circuit as a control signal of the first sampling switch S5, and the fifth control signal Sense5 output by the logic control circuit is output to the voltage sampling circuit as a control signal of the second sampling switch S6. For the timing waveform diagrams of the voltage sampling circuit shown in Figure 13 in CCM mode and DEM mode, please refer to Figure 14. The left part of the figure is the S5, S6 state and VA node voltage waveforms in CCM mode; the right part is the voltage waveform of the VA node in DEM mode. S5, S6 state and VA node voltage waveform, when S5 and S6 are both off, the VA node voltage is equal to the input voltage VB of BUFFER. In this case, the bias voltage VDP entering the triangle wave generating circuit is completely independent of the signal size at the sampling commutation point SW, so the system operating frequency is completely independent of the output current load.

2. The sampling signal obtained by the voltage sampling circuit is a fixed signal. In this case, the input terminal of the voltage sampling circuit is directly connected to a fixed voltage, and the sampling signal obtained by the voltage sampling circuit is a fixed voltage, and the fixed voltage is internally buffered. After the device, the bias voltage VDP is output from the output terminal. This application will not show the circuit diagram of the voltage sampling circuit in this case.

This application introduces various circuit implementations of hysteresis comparator circuit, voltage sampling circuit and triangle wave generating circuit through the above content. In actual implementation, these multiple circuits can be combined with each other in different ways to form a variety of different circuit structures. For the circuit of the switching power supply system, this application does not illustrate every possible implementation in detail. In each of the above-mentioned embodiments, the logic control circuit includes various conventional logic devices, so that the input modulation wave signal PWM is logically processed to generate the required driving and control signals. The circuit construction of the specific logic control circuit can be based on The actual situation is self-configured. In this application, the logic control circuit outputs the upper arm drive signal DRU, the lower arm drive signal DRL and five control signals Sense1 to Sense5 as an example, and a possible circuit structure of the logic control circuit is shown in Figure 15. As shown, Figure 15 is for reference only and is not used to limit the logic control circuit.

Based on the above-mentioned circuit structure disclosed in this application, this application uses FIG. 4 and FIG. 10 as two typical circuit structures to show the working process of the switching power supply system disclosed in this application:

1. When the switching power supply system adopts the circuit structure shown in Figure 4, the hysteresis generation circuit is set between the error amplifier and the comparator to perform hysteresis control on the COMP signal, and the voltage sampling circuit is directly coupled to SW, then the switching power supply system is in CCM mode (Continuous mode) Please refer to Figure 16 for the working waveform diagram. When the upper arm MOS switch S1 is turned on and the lower arm MOS switch S2 is turned off, the hysteresis generating circuit generates a hysteresis signal Vhysteretic on the error signal COMP generated by the error amplifier to obtain the hysteresis. After the error signal, shown as COMP2 in Figure 16, the triangular wave signal Ramp voltage starts to rise linearly. When the Ramp voltage rises to equal to COMP2, the upper arm MOS switch S1 is turned off, and the lower arm MOS switch S2 is turned on. At this time, the COMP2 signal jumps a hysteresis Vhysteretic, and the Ramp signal linearly drops; when the Ramp signal drops to COMP2 again, The lower arm S2 is turned off and the upper arm S1 is turned on again. At this time, the COMP2 signal jumps by a hysteresis, the Ramp signal rises linearly again until the Ramp signal is equal to the COMP2 signal again, the upper arm MOS switch S1 is turned off, the lower arm MOS switch S2 is turned on, and the cycle repeats . The operating frequency of the system in CCM mode is:

Please refer to Figure 17 for the operating waveform of the switching power supply system in DCM mode (intermittent mode). When the system enters DCM, the lower arm MOS switch S2 is turned off. At this time, the upper and lower arm MOS switches are both in the off state, the SW voltage stabilizes at the output voltage VOUT value after oscillation, and the Ramp signal terminates the linear speed drop during the on-time of the lower arm MOS switch S2. Since both the upper and lower arm MOS switches are turned off, the system output voltage VOUT decreases after being consumed by the load, so that the output voltage COMP of the error amplifier EA increases.

2. When the switching power supply system adopts the circuit structure shown in Figure 10, the hysteresis generating circuit is set between the triangle wave generating circuit and the comparator to perform hysteresis control on the Ramp signal, and the voltage sampling circuit is directly coupled to SW, then the switching power supply system is in CCM Please refer to Figure 18 for the working waveform diagram in the continuous mode. When the upper arm MOS switch S1 is turned on and the lower arm MOS switch S2 is turned off, the Ramp signal starts to rise linearly. When the Ramp signal rises to equal to the COMP signal, the upper arm MOS The switch S1 is turned off and the lower arm MOS switch S2 is turned on. At this time, the Ramp signal jumps up by a hysteresis amount Vhysteretic, and then the Ramp signal begins to linearly decrease; when the Ramp signal drops to the COMP signal again, the lower arm MOS switch S2 is turned off , The upper arm MOS switch S1 is turned on again. At this time, the Ramp signal first jumps by a hysteresis amount Vhysteretic, and the Ramp signal rises linearly again until the Ramp signal is equal to the COMP signal again. The upper arm MOS switch S1 is turned off, and the lower arm MOS switch S2 is turned on, and the cycle starts again. .

The above are only the preferred implementation manners of the present application, and the present invention is not limited to the above embodiments. It can be understood that other improvements and changes directly derived or thought of by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims

A switching power supply system based on hysteresis mode control, characterized in that the switching power supply system includes a series circuit composed of an upper arm MOS switch and a lower arm MOS switch, and one end of the series circuit is connected to the system input end of the switching power supply system , The other end is grounded, the common end of the upper arm MOS switch and the lower arm MOS switch is used as a sampling commutation point to connect the system output end of the switching power supply system through an inductor, and the system output end is also connected to a first resistor and a first resistor, respectively. A capacitor and a second capacitor, the other end of the second capacitor is grounded, the first resistor is connected to the other end of the first capacitor and then grounded through a second resistor, the first resistor is connected to the second resistor The common terminal is connected to the inverting input terminal of the error amplifier, the non-inverting input terminal of the error amplifier inputs the reference signal, the output terminal of the error amplifier is connected to the hysteresis comparator circuit, and the output terminal of the error amplifier is also connected to the compensation capacitor and After the compensation resistor is grounded, the error amplifier generates an error signal according to the input signal and outputs it to the hysteresis comparator circuit;

The input terminal of the voltage sampling circuit obtains a sampling signal, and the output terminal is connected to the input terminal of the triangle wave generating circuit. The voltage sampling circuit is used to generate a bias voltage according to the sampling signal and output it to the triangle wave generating circuit. The sampling signal is The fixed signal or the sampling signal is a variable signal reflecting the information characteristics of the signal at the sampling commutation point; the triangle wave generating circuit includes a series circuit composed of a first switch and a second switch, one end of the series circuit is connected The working voltage and the other end are grounded. The common ends of the first switch and the second switch are sequentially connected to a third resistor and a third capacitor. The other end of the third capacitor is used as the input end of the triangle wave generating circuit to connect to the In the voltage sampling circuit, the common terminal of the third resistor and the third capacitor is used as the output terminal of the triangular wave generating circuit to be connected to the hysteresis comparator circuit, and the triangular wave generating circuit is used to connect the hysteresis comparator circuit according to the bias voltage and the The control signal of the first switch and the control signal of the second switch generate a triangular wave signal and output it to the hysteresis comparator circuit; the output terminal of the hysteresis comparator circuit is connected to the input terminal of the logic control circuit, the hysteresis comparator The circuit is used to perform a hysteresis comparison between the error signal and the triangular wave signal according to the input first control signal to generate a modulated wave signal and output it to the logic control circuit. The logic control circuit performs logic processing on the modulated wave signal The upper arm drive signal, the lower arm drive signal, the first control signal, the second control signal, and the third control signal are generated. The upper arm drive signal is opposite to the lower arm drive signal, and the first control signal, the second The control signal and the third control signal are coupled to the upper and lower arm drive signals and have the same frequency as the upper and lower arm drive signals. The upper arm drive signal is used to drive the upper arm MOS switch, and the lower arm drive signal is used to drive the upper arm. In the lower arm MOS switch, the first control signal is output to the hysteresis comparator circuit as a control signal of the hysteresis comparator circuit, and the second control signal is output to the hysteresis comparator circuit as a control signal of the first switch A triangle wave generating circuit, and the third control signal is output to the triangle wave generating circuit as a control signal of the second switch.
The switching power supply system according to claim 1, wherein the hysteresis comparator circuit comprises a hysteresis generating circuit and a comparator, and the input of the comparator is respectively connected to the output of the error amplifier and the triangular wave generator. An output terminal of the circuit, the output terminal of the comparator is connected to the logic control circuit as the output terminal of the hysteresis comparator circuit, and the first control signal generated by the logic control circuit is output to the hysteresis generating circuit; The hysteresis generating circuit is arranged at the output terminal of the error amplifier and generates a hysteresis signal to the error signal according to the first control signal, or the hysteresis generating circuit is arranged at the output terminal of the triangle wave generating circuit and according to The first control signal generates a hysteresis signal to the triangle wave signal.
The switching power supply system according to claim 2, wherein:

When the hysteresis generating circuit is arranged at the output terminal of the error amplifier, the hysteresis generating circuit is arranged between the output terminal of the error amplifier and the input terminal of the comparator, or the hysteresis generating circuit is arranged At both ends of the compensation resistor; when the hysteresis generating circuit is arranged at the output terminal of the triangle wave generating circuit, the hysteresis generating circuit is arranged at the output terminal of the triangle wave generating circuit and the input terminal of the comparator between.
The switching power supply system according to claim 3, wherein when the hysteresis generating circuit is arranged between the output terminal of the error amplifier and the input terminal of the comparator, or the hysteresis generating circuit is arranged at When between the output terminal of the triangle wave generating circuit and the input terminal of the comparator, the hysteresis generating circuit includes:

A first series circuit composed of a first current source, a first hysteresis switch, a second hysteresis switch, and a second current source, and a first series circuit composed of a third current source, a second hysteresis switch, a first hysteresis switch, and a fourth current source Two series circuits, the positive poles of the first series circuit and the second series circuit are respectively connected to the working voltage, and the negative poles are respectively grounded, and one end of the hysteresis resistor is connected to the first hysteresis switch and the second hysteresis switch in the first series circuit The other end of the hysteresis resistor is connected to the common end of the first hysteresis switch and the second hysteresis switch in the second series circuit, the common end of the first hysteresis switch and the second hysteresis switch in the first series circuit Terminal as the input terminal of the hysteresis generating circuit is connected to the error amplifier or the output terminal of the triangular wave generating circuit, the common terminal of the first hysteresis switch and the second hysteresis switch in the second series circuit is used as the hysteresis generating circuit The output terminal of the circuit is connected to the comparator; the first hysteresis switch in the first series circuit and the first hysteresis switch in the second series circuit are controlled by the same control signal, and the first hysteresis switch in the first series circuit The second hysteresis switch and the second hysteresis switch in the second series circuit are controlled by the same control signal. The control signal of the first hysteresis switch and the control signal of the second hysteresis switch are both coupled to the first control signal and both The control signals are opposite.
4. The switching power supply system of claim 3, wherein when the hysteresis generating circuit is arranged between the output terminal of the error amplifier and the input terminal of the comparator, the hysteresis generating circuit comprises:

A series circuit composed of a current source, a second hysteresis switch and a first hysteresis switch, the positive pole of the series circuit is connected to the working voltage and the negative pole is grounded, and the common terminal of the second hysteresis switch and the first hysteresis switch is used to connect the compensation The common terminal of the capacitor and the compensation resistor, the control signal of the first hysteresis switch and the control signal of the second hysteresis switch are all coupled to the first control signal, and the two control signals are opposite.
The switching power supply system according to claim 1, wherein:

The input terminal of the voltage sampling circuit is connected to a fixed voltage, and the sampling signal obtained by the voltage sampling circuit is the fixed voltage;

Alternatively, the input terminal of the voltage sampling circuit is coupled to the sampling commutation point, and the sampling signal acquired by the voltage sampling circuit is the signal at the sampling commutation point;

Alternatively, the input terminal of the voltage sampling circuit is connected to the logic control circuit, and the sampling signal acquired by the voltage sampling circuit includes a fourth control signal and a fifth control signal output by the logic control circuit, and the first The fourth control signal and the fifth control signal are coupled to the upper and lower arm drive signals, and the fourth control signal is opposite to the fifth control signal.
The switching power supply system according to claim 6, wherein when the input terminal of the voltage sampling circuit is directly coupled to the sampling commutation point, the voltage sampling circuit comprises: an RC composed of a filter resistor and a filter capacitor A filter circuit, the input terminal of the RC filter circuit as the input terminal of the voltage sampling circuit is coupled to the sampling commutation point, and the output terminal of the RC filter circuit is connected to the output terminal of the voltage sampling circuit through a buffer.
The switching power supply system according to claim 6, wherein when the input terminal of the voltage sampling circuit is connected to the logic control circuit, the voltage sampling circuit comprises:

A series circuit composed of a first sampling switch and a second sampling switch. One end of the series circuit is connected to the working voltage and the other end is grounded. The common end of the first sampling switch and the second sampling switch is connected to a filter resistor and a filter capacitor. The input terminal of the RC filter circuit, the output terminal of the RC filter circuit is connected to the output terminal of the voltage sampling circuit through a buffer; the fourth control signal output by the logic control circuit is output as the control signal of the first sampling switch For the voltage sampling circuit, the fifth control signal output by the logic control circuit is output to the voltage sampling circuit as a control signal of the second sampling switch.
The switching power supply system according to any one of claims 1 to 8, wherein the triangle wave generating circuit further includes a current generating circuit, and the current generating circuit includes a first gain module, a second gain module, a divider and In the voltage-current converter, the input terminal of the first gain module is connected to the system input terminal, the input terminal of the second gain module is connected to the system output terminal, and the output terminal of the first gain module is connected to the first gain module. The output terminals of the two gain modules are respectively connected to the two input terminals of the divider, the output terminal of the divider is connected to the input terminal of the voltage-current converter, and the output terminal of the voltage-current converter is used as the current generator The output terminal of the circuit is connected to the output terminal of the triangle wave generating circuit.