CN106487222B - Power supply operating in ripple control mode and control method thereof - Google Patents

Abstract

The present invention proposes a power supply operating in a ripple control mode and a control method thereof. The power supply is used to supply power to a load, and includes a power converter, a far output power supply terminal, a transmission line, a feedback circuit, and a power controller. The power converter is used to convert an input power supply into a near output power supply. The power converter has a power input terminal for receiving the input power supply, and a near output power supply terminal for outputting the near output power supply. The far output power supply terminal provides a far output power supply to the load. The transmission line is connected between the near output power supply terminal and the far output power supply terminal. The feedback circuit generates a feedback signal based on the potential of the far output power supply terminal and the near output power supply terminal. The power controller controls the power converter, and outputs a pulse to the power converter based on the feedback signal and a reference signal, thereby converting the input power supply into the near output power supply.

Description

Power supply operating in ripple control mode and its control method

technical field

The present invention relates to a power supply and its control method, in particular to a feedback control method of a switching power supply.

Background technique

Switching mode power supply (switching mode power supply), because it has quite good conversion efficiency, is widely used in the conversion between power sources of different voltages.

FIG. 1 shows a known switch mode power supply 10 for supplying power to a load 20 . The switch-mode power supply 10 includes a buck converter 12 for converting a relatively high-voltage input voltage V _IN into a relatively low-voltage output V _ON . The voltage information of the output voltage source V _ON is fed back to the feedback terminal FB of the power controller 14 through the voltage divider circuit 16 . The power controller 14 generates a pulse-width-modulation (PWM) signal accordingly to control the step-down power converter 12 so that the output voltage V _ON is substantially stable at a preset value. For example, when the feedback voltage V _FB on the feedback terminal FB is lower than a set value, the power controller 14 provides a pulse on the high-side terminal HS to make the high-side power switch SW _HS turn on for a time T _ON maintain conduction. At this moment, the input voltage source V _IN starts to supply electric energy to the inductor L and the output capacitor C _O . After the on-time T _ON ends, the power controller 14 turns on the low-side power switch SW _LS through the low-side terminal LS until the energy stored in the inductor L is completely released to the output capacitor C _O. If the feedback voltage V _FB has exceeded the set value, the high-side power switch SW _HS is always kept in the off state. In other words, when the voltage of the output voltage power supply V _ON is low, the input voltage power supply V _IN converts electric energy to the output voltage power supply V _ON through the inductor L, and pulls up its voltage; otherwise, when the voltage of the output voltage power supply V _ON is high, the electric energy The conversion doesn't happen. Therefore, the voltage of the output voltage source V _ON- can be substantially stabilized at a predetermined value. However, in some applications, the power converter and the load being driven are very far away from each other. As shown in FIG. 1 , the load 20 is not directly connected to the output voltage source V _ON , and there is a considerable length of conductive wire 18 , such as a printed copper wire on a printed circuit board (PCB), between the two. For the convenience of description, the connection between the conductive line 18 and the power converter 12 is called the near output power supply terminal _ON in this specification, and the connection between the conductive line 18 and the load 20 is called the far output power supply terminal _OR . The output voltage power _{V ON} on the near output power supply terminal ON is also referred to as the near-end output power V _ON , and the remote output power supply terminal _OR is provided with the remote output power V _OR .

Although the switch mode power supply 10 in FIG. 1 can stabilize the voltage of the near-end output power V _ON approximately at a preset value, it cannot stabilize the voltage of the remote output power V _OR . For example, when the load 20 is very light or no-load, the current flowing through the conductive line 18 is almost negligible, so the voltage of the remote output power V _OR and the near-end output power V _ON will be about the same. However, when the load 20 is heavy, the current flowing through the conduction line 18 will be considerable, so the voltage drop generated by the parasitic resistance of the conduction line 18 will cause the voltage of the remote output power V _OR to significantly decrease. A voltage lower than the near-end output supply V _ON . The remote output power V _OR is the real power supply to the load 20 , so the stability of its voltage is very important and should not be affected by changes in the load 20 .

Contents of the invention

The present invention provides a power supply for supplying power to a load, including a power converter, a remote output power supply terminal, a conductive line, a feedback circuit, and a power controller. The power converter is used for converting an input power into a near-end output power. The power converter has a power input end for receiving the input power, and a near output power supply end for outputting the near output power. The remote output power supply terminal provides a remote output power supply to the load. The conducting wire is connected between the near output power supply end and the far output power supply end. The feedback circuit generates a feedback signal according to the potentials of the far output power supply terminal and the near output power supply terminal. The power controller controls the power converter, outputs a pulse to the power converter according to the feedback signal and a reference signal, and converts the input power into the near-end output power.

The invention also provides a control method for controlling a power supply to supply power to a load. The power supply includes a power input terminal and a near output power supply terminal. The power supply input end receives an input power supply, and the near-end output power supply end outputs a near-end output power generated by conversion of the input power supply. A remote output power supply provides a remote output power to supply power to a load. A conductive line is connected between the near output power supply end and the far output power supply end. The power control method includes: receiving the far-end output power; receiving the near-end output power; generating a feedback signal according to the potential of the far-end output power and the potential of the near-end output power; according to the feedback signal and a reference signal generating a pulse; and converting the input power into the near-end output power according to the pulse.

Description of drawings

In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

FIG. 1 is a known switch mode power supply.

Figure 2 is another switching power supply.

FIG. 3 is a power supply implemented according to the present invention.

FIG. 4 shows the signal S _HS on the high-side terminal HS, the signal S _LS on the low-side terminal LS, the feedback signal V _FB on the feedback terminal FB, and the digital comparison result S _OUT .

Fig. 5 shows a control method of the turn-on time T _ON .

FIG. 6 shows another control method of the on-time T _ON .

The component numbers in the figure are explained as follows:

10: Switching power supply

12: Buck power converter

14: Power controller

16: Voltage divider circuit

18: Conductive wire

20: load

30: Switching power supply

60: Power supply

62: Power controller

64: Comparator

68: Pulse generator

70: Feedback circuit

90, 92, 94, 96, 97, 98: steps

C _DECAP : Decoupling capacitance

C _FB : Feedback capacitor

C _o : output capacitance

FB: feedback terminal

GND: ground terminal

HS: high side

L: inductance

LS: low side

_ON : Near the output power supply terminal

O _R : remote output power supply terminal

R ₁ : resistance

R2 _: resistance

S _HS : signal

S _LS : signal

S _OUT : digital comparison result

SW _HS : High-side power switch

SW _LH : Low-side power switch

t ₀ , t ₁ , t ₂ : time

T _CYC : Conversion cycle

T _CYC-TAR : target conversion cycle

T _OFF : off time

T _ON : Turn on time

V _FB : Feedback signal

V _REF : Reference signal

V _IN : Input voltage supply

V _ON : output voltage power supply, near-end output power supply

V _OR : Remote output power supply

Detailed ways

Aiming at the shortcomings in the prior art, a possible solution is to change the near-end monitoring in FIG. 1 to remote sensing (remote sensing), as shown in FIG. 2 . FIG. 2 shows another switching power supply 30 for supplying power to a load 20 . The voltage dividing circuit 16 in FIG. 2 is connected between the remote output power supply terminal _OR and a ground terminal GND, detects the voltage of the remote output power supply V _OR , and feeds back the detection result to the feedback terminal FB of the power controller 14.

Theoretically, since the power controller 14 in FIG. 2 monitors the voltage of the remote output power V _OR , the switch mode power supply 30 should be able to stabilize the voltage of the remote output V _OR at a preset value. However, the implementation of the switch mode power supply 30 in FIG. 2 may still cause the voltage instability of the remote output power V _OR or the problem of excessive output ripple. Even in the application manuals of many power controllers, it is clearly pointed out that the power controllers cannot be used for remote monitoring. One of the reasons is the influence of the parasitic inductance and resistance in the conductive line 18 . Once the conductive line 18 is quite long, the parasitic inductance and resistance therein become considerable. Inductance and resistance form a low-pass circuit, which causes signal delay and also leads to instability of the entire control loop.

FIG. 3 is a power supply 60 implemented according to the present invention to supply power to the load 20 . The power supply 60 can stabilize the voltage of the remote output power V _OR .

The power supply 60 includes a power controller 62 , a step-down power converter 12 , a conductive line 18 , and a feedback circuit 70 .

The power controller 62 can be an integrated circuit, having (but not limited to) pins of a feedback terminal FB, a high-side terminal HS, and a low-side terminal LS. The step-down power converter 12 is used for converting a relatively high voltage input voltage V _IN into a relatively low voltage near-end output V _ON . The conduction line 18 is connected between the near output power supply terminal ON and the far output power supply terminal _OR , and its parasitic inductance and resistance form a low _- pass circuit, so it is a low-pass conduction line. The output capacitor _{C o} is connected between the near output power supply terminal ON and the ground terminal GND, and the decoupling capacitor C _DECAP is connected between the far output power supply terminal _OR and the ground terminal GND.

The feedback circuit 70 includes a feedback capacitor C _FB , a resistor R ₁ , and a resistor R ₂ . The feedback capacitor _{C FB} is connected between the near output power supply terminal ON and the feedback terminal FB. _The resistors R1 and R2 are connected in series between the remote output power supply terminal _OR and the ground terminal _GND with the feedback terminal FB as the connection point. Through simple circuit derivation, it can be seen that the relationship between the feedback signal V _FB , the remote output power V _OR and the near-end output power V _ON can be expressed as the following formula (1)

Among them, VFB, VON, and VOR are divided into the voltage of the feedback signal V _FB , the near-end output power V _ON , and the far-end output power V _OR , CFB is the capacitance value of the feedback capacitor C _FB , i is an imaginary number, f is the signal frequency, R1 R1 and R2 are the resistance values _of resistors R1 and _R2 respectively, and R1//R2 represents the equivalent resistance value after resistors _R1 and _R2 are connected in parallel.

The feedback circuit 70 provides low-pass filtering of the remote output power V _OR on the remote output power supply terminal _OR , and can generate a low-pass signal of the remote output power V _OR at the feedback terminal FB (ie, the second half of the formula (1)) . The feedback circuit 70 also provides high-pass filtering of the near-end output power V _ON on the near-output power supply terminal ON, and can generate a high-pass signal of the near-end output power V _ON at the feedback terminal FB (ie, the first half of _formula (1)). Therefore, in Fig. 3, the feedback signal V _FB on the feedback terminal FB is approximately a potential of the far-end output power V _OR (in this embodiment, the low-pass signal), and a potential of the near-end output power V _ON (In this embodiment, it is the high-pass signal), the combination of the two. In other embodiments, the feedback circuit 70 can be composed of other circuit architectures, as long as the feedback terminal FB can provide the potential of the remote output power V _OR and the potential of the near-end output power V _ON , the same effect can be achieved. .

The power controller 62 can operate in a ripple mode. The so-called ripple control mode refers to the power conversion performed by the power converter, which is an operation mode triggered by the voltage of the output power. For example, the power controller 62 has a comparator 64 and a pulse generator 68 . The comparator 64 compares the feedback signal V _FB with a reference signal V _REF , and the reference signal V _REF may be a fixed 2.5V. According to the difference between the feedback signal V _FB and the reference signal V _REF , the comparator 64 outputs a digital comparison result S _OUT . When the digital comparison result S _OUT changes from logic "0" to "1" (the feedback signal V _FB is lower than the reference signal V _REF ), the pulse generator 68 is triggered to provide a pulse on the high-side terminal HS . When the comparison result S _OUT maintains logic “0” (the feedback signal V _FB is higher than the reference signal V _REF ), the pulse is not provided. Compared with the general power controller using an operational amplifier, the power controller 62 operating in the ripple control mode has a faster response speed, so that the remote output power V _OR has lower output ripple.

The buck power converter 12 has a high-side power switch SW _HS , a low-side power switch SW _LH , and an inductor L. As shown in FIG. The pulse width of a pulse on the high-side terminal HS roughly determines the turn-on time T _ON of the high-side power switch SW _HS . For example, when the feedback signal V _FB is lower than the reference signal V _REF , the comparator 64 outputs a digital comparison result S _OUT with a logic value of "1", and the pulse generator 68 accordingly provides a pulse at the high-side terminal HS, Turn on the high-side power switch SW _HS .

FIG. 4 shows the signal S _HS on the high-side terminal HS, the signal S _LS on the low-side terminal LS, the feedback signal V _FB on the feedback terminal FB, and the digital comparison result S _OUT . Signal S _HS has several pulses. The pulse width of each pulse is called the on-time T _ON . Between two consecutive pulses, it is called the off-time T _OFF . The combination of an on-time T _ON and an off-time T _OFF is called a switching period T _CYC . At time t ₀ , when the feedback signal V _FB is lower than the reference signal V _REF , a pulse appears on the signal S _HS , the high-side power switch SW _HS is turned on, and the on-time T _ON begins. After the on-time T _ON is over, another pulse appears on the signal S _LS to turn on the low-side power switch SW _LS . The low-side power switch SW _LS is used to provide a synchronous rectifier (synchronous rectifier, SR) function.

The power controller 62 can operate in a minimum OFF-time mode, that is, the off-time T _OFF after an on-time T _ON cannot be less than a minimum off-time T _OFF-MIN . In other words, after the high-side power switch SW _HS is turned off at time t ₁ , at least the minimum off-time T _OFF-MIN is required before being turned on again to enter the next on-time T _ON . For example, in FIG. 3 , when the feedback signal V _FB is lower than the reference signal V _REF and the off-time T _OFF exceeds the minimum off-time T _OFF-MIN , the pulse generator 6 is at the high-side terminal HS at time _t2 . Provide another pulse on , starting the next on-time T _ON .

The power controller 62 can operate in a constant ON-time mode, that is, the on-time T _ON is always a constant value. However, in another embodiment, although each of the on-times T _ON in several adjacent switching cycles is approximately the same, the on-time T _ON can still be slowly adjusted according to the detection results in the long run.

FIG. 5 shows a control method of the on-time T _ON , which can be used in the power controller 62 . In step 90, the pulse generator 68 detects the voltages of the input voltage source V _IN and the near-end output power source V _ON ; then step 92 determines the on-time T _ON according to the detection result. For example, T _ON =K*VON/VIN (Formula 1), wherein K is a constant, VON is the voltage of the near-end output power V _ON , and VIN is the voltage of the input voltage power V _IN . When the turn-on time T _ON is controlled according to Equation 1 and the buck power converter 12 operates in a continuous conduction mode (CCM), the switching period T _CYC can be maintained approximately at a constant. The so-called CCM means that at the end of a conversion cycle, the energy stored in the inductance element has not been fully released, and the next conversion cycle begins; in contrast, the discontinuous conduction mode (discontinuous conduction mode, DCM) refers to a conversion At the end of the cycle, the energy stored in the inductive element must be completely released, and the next conversion cycle will start.

FIG. 6 shows another control method of the on-time T _ON , which is also applicable to the power controller 62 . Step 94 detects the time length of the switching period T _CYC . For example, step 94 detects the time length between two consecutive rising edges or falling edges in the signal S _HS . Step 96 compares the switching period T _CYC with a target switching period T _CYC-TAR . If the switching period T _CYC is greater than the target switching period T _CYC-TAR , step 98 decreases the on-time T _ON . The turn-on time T _ON is relatively short, because the inductor L stores relatively little power, so the near-end output power V _ON and the remote output power V _OR will drop earlier, which can shorten the subsequent conversion cycle T _CYC . Conversely, if the switching period T _CYC is smaller than the target switching period T _CYC-TAR , step 97 increases the on-time T _ON . The control method in FIG. 6 can make the conversion period T _CYC approach to the target conversion period T _CYC-TAR .

Using a far-end output value of the far-end output power V _OR and a near-end output value of the near-end output power V _ON as feedback, the power supply 60 in FIG. 3 can provide a fast enough response speed to stabilize the far-end output The voltage of the power supply V _OR .

Although FIG. 3 takes a synchronous rectification buck power converter operating in ripple control mode as an example, the present invention is not limited thereto. For example, the present invention is also applicable to asynchronous power converters, and the present invention is also applicable to a boost converter.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be defined by the claims.

Claims (14)

1. A power supply for supplying power to a load, comprising: A power converter is used to convert an input power to a near-end output power, including: a power input terminal for receiving the input power; and a near-output power supply end for outputting the near-end output power; A remote output power supply terminal, providing a remote output power supply to the load; a conducting wire connected between the near output power supply end and the far output power supply end; a feedback circuit, generating a feedback signal according to the potential of the far-end output power supply and the potential of the near-end output power supply; and A power controller outputs a pulse to the power converter according to the feedback signal and a reference signal, and the power converter converts the input power into the near-end output power according to the pulse; Wherein, the feedback circuit includes: a voltage divider circuit with two resistors connected in series between the far output power supply terminal and a ground terminal through a feedback terminal; and a feedback capacitor connected between the feedback terminal and the near output power supply terminal. between the ends. 2. The power supply according to claim 1, wherein the power converter is a step-down converter with a power switch controlled by the pulse, and a pulse width of the pulse is the same as that of the power switch of a turn-on time. 3. The power supply as claimed in claim 2, wherein the power controller detects the input power to control the pulse width. 4. The power supply as claimed in claim 2, wherein the power controller detects the near-end output power to control the pulse width. 5. The power supply as claimed in claim 2, wherein the power controller detects a switching cycle of the power converter to control the pulse width switching cycle. 6. The power supply according to claim 1, wherein the power controller comprises: a comparator, comparing the feedback signal and the reference signal to generate a digital comparison result; and A pulse generator, connected to the comparator, outputs the pulse when the digital comparison result is in transition. 7. The power supply as claimed in claim 1, wherein the remote output power is a low-pass signal, and the near-end output power is a high-pass signal. 8. A control method for controlling a power supply to supply power to a load, the power supply comprising a power input terminal receiving an input power supply, and a near output power supply terminal outputting a near-end output power converted from the input power supply , and a remote output power supply terminal provides a remote output power supply to the load, and is characterized in that it also includes a feedback circuit, the feedback circuit includes: a voltage divider circuit with two resistors connected in series to the remote terminal through a feedback Between the output power supply terminal and a ground terminal; and a feedback capacitor connected between the feedback terminal and the near output power supply terminal; the near output power supply terminal and the far output power supply terminal are connected through a conductive line, the control method Include: receiving the remote output power; receiving the near-end output power; generating a feedback signal according to the potential of the remote output power supply, the potential of the near-end output power supply, the resistance of the two resistors, and the capacitance of the feedback capacitor; generating a pulse according to the feedback signal and a reference signal; and The input power is converted into the near-end output power according to the pulse. 9. The control method according to claim 8, wherein the power supply further comprises a power switch, and the control method further comprises: The power switch is turned on to adjust the voltage of the near-end output power supply, wherein a pulse width of the pulse is related to a turn-on time of the power switch. 10. The control method as claimed in claim 9, further comprising: The input power is sensed to control the pulse width. 11. The control method as claimed in claim 9, further comprising: The proximal output power is sensed to control the pulse width. 12. The control method according to claim 9, wherein the step of converting the input power to the near-end output power according to the pulse has a conversion period, and the control method further comprises: The switching period is detected to control the pulse width. 13. The control method according to claim 8, wherein the step of generating the pulse feedback according to the feedback signal and the reference signal comprises: comparing the feedback signal and the reference signal to generate a digital comparison result; and The pulse is output when the digital comparison result transitions. 14. The control method according to claim 8, wherein the remote output power is a low-pass signal, and the near-end output power is a high-pass signal.