TWI650629B - Over-current protection method with frqueency modulation for voltage regulator and circuit thereof - Google Patents

Abstract

The present invention provides a frequency-modulated overcurrent protection method for a voltage regulator having a high side switch, a low side switch, and an inductor, the method comprising the following steps. First, during the conduction of the low side switch, the inductor current signal of the voltage regulator is compared with the low side conduction reference current signal to obtain a crossover interval, wherein the inductor current signal is greater than the low side conduction reference current signal in the crossover interval. . Then, the frequency of the pulse width modulation signal of the voltage regulator is linearly reduced according to the length of time of the crossover interval, thereby avoiding the case where the voltage regulator generates an overcurrent.

Description

Overcurrent protection method for frequency modulation of voltage regulator and electric power thereof road

The present invention relates to an overcurrent protection method, and more particularly to a frequency modulation overcurrent protection method for a voltage regulator and a circuit therefor.

Please refer to FIG. 1. FIG. 1 is a circuit diagram of a conventional voltage regulator. The voltage regulator is a voltage adjustment circuit for adjusting the input voltage to an output voltage. A typical voltage regulator has a high side switch 120, a low side switch 130, and an inductor 140, while the high side switch 120 and the low side switch 130 are controlled by the control circuit 110. The high side switch 120 is electrically connected to the first end of the voltage input terminal Vin and the inductor 140. The low side switch 130 is electrically connected to the first end of the inductor 140 and the ground end 150, and the second end of the inductor 140 is connected to the voltage output terminal Vout. The control circuit 110 alternately turns on the high side switch 120 and the low side switch 130 to adjust the output voltage of the output terminal Vout. When the high-side switch 120 is turned on, the inductor current I _L rises, and during the rising period, the high-side switch ON period HS when the high-side switch 120 is turned on indicates that when the low-side switch 130 is turned on, the inductor current I _L decreases, and the falling period thereof The low side switch on period LS when the low side switch 130 is turned on is indicated.

When the voltage difference between the input terminal Vin and the output terminal Vout is larger, the protection variation of the overcurrent of the high side switch is also larger. When the voltage of the input terminal Vin and the voltage of the output terminal Vout are much different, the current slope of the HS during the on-time of the high-side switch can be quite large, so that the change speed of the inductor current I _L is quite fast. Since the inductor current I _L sense control circuit 110 based on the sensed inductor current I _L to make adjustments to the size of the switch, the inductor current I _L when the rate of change is too fast, the operation control circuit 110 when the reaction is not originally The value of the sensed inductor current I _L , which would make the overcurrent protection mechanism variability. When the output terminal is short-circuited or a large current value is instantaneously pulled, the output voltage of the output terminal Vout is lowered, or the high-side minimum conduction time exceeds the duty cycle conversion ratio time (D=Vout/(Vin×fsw)), so that each The current of HS during the on-time of a high-side switch is greater than the current of HS during the on-time of the previous high-side switch. As shown in FIG. 2A, when the inductor current I _{L is} not effectively suppressed and continues to rise, and the circuit continues to operate, this may cause Excessive current can even cause component damage.

Embodiments of the present invention provide a method and a circuit for over-current protection of a voltage regulator for frequency modulation, in order to avoid a situation in which a voltage regulator generates an overcurrent.

Embodiments of the present invention provide a frequency modulation overcurrent protection method for a voltage regulator having a high side switch, a low side switch, and an inductor, the method comprising the following steps. First, during the conduction of the low side switch, the inductor current signal of the voltage regulator is compared with the low side conduction reference current signal to obtain a crossover interval, wherein the inductor current signal is greater than the low side conduction reference current signal in the crossover interval. . Then, according to the length of the crossover interval, the frequency of the pulse width modulation signal of the voltage regulator is linearly reduced, that is, the current low side conduction time is correspondingly increased according to the time length of the intersection interval, that is, the current pulse width is adjusted. The frequency of the variable signal is reduced.

Embodiments of the present invention provide a frequency-modulated overcurrent protection circuit for a voltage regulator having a high-side switch, a low-side switch, and an inductor, and the frequency-modulated overcurrent protection circuit includes an electric A sense current sensing unit and a control circuit. The inductor current sensing unit is electrically connected to the inductor to sense the current of the inductor to obtain an inductor current signal. The control circuit is electrically connected to the high side switch and the low side switch for controlling the high side switch and the low side switch, wherein the control circuit compares the inductor current signal of the voltage regulator with the low side conduction reference current signal during the period of turning on the low side switch A crossover interval is obtained in which the inductor current signal is greater than the low side conduction reference current signal, and the control circuit linearly reduces the frequency of the voltage regulator modulation signal of the voltage regulator according to the length of the crossover interval.

In summary, the embodiment of the present invention provides a frequency modulation overcurrent protection method for a voltage regulator and a circuit thereof, and the inductor current exceeds a comparison reference value according to the low side switch (the low side conduction reference current) The length of the crossover interval at the time of the signal) correspondingly linearly reduces the frequency of the pulse width modulation signal. That is, the frequency of the pulse width modulation signal linearly decreases as the inductor current when the low side switch is turned on exceeds the comparison reference value (low side conduction reference current signal).

The detailed description of the present invention and the accompanying drawings are to be understood by the claims The scope is subject to any restrictions.

110‧‧‧Control circuit

120‧‧‧ high side switch

130‧‧‧low side switch

140‧‧‧Inductance

IL‧‧‧Inductor Current

15, 250‧‧‧ grounding end

Vn‧‧‧ input

Vout‧‧‧ output

HS‧‧‧High-side switch during conduction

LS‧‧‧ low side switch during conduction

S310, S320‧‧‧ step process

VLSOC_ref‧‧‧Low side conduction current reference signal

VHSOC_ref‧‧‧High Side Conduction Current Reference Signal

210‧‧‧First current sensing unit

220‧‧‧Second current sensing unit

230, 240‧‧‧Resistive components

260, 270‧‧‧ comparator

VSO, Vsum‧‧‧ voltage

LSOCB, HSOC‧‧‧ comparison signal

280‧‧‧ oscillating circuit

290‧‧‧Logical unit

PWMin‧‧‧ pulse width modulation signal

CT‧‧‧Crossover interval

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments will be briefly described below. Obviously, the drawings in the following description are only some of the present invention. For the embodiments, other drawings may be obtained from those skilled in the art without any inventive labor.

Figure 1 is a circuit diagram of a conventional voltage regulator.

2A is a waveform diagram of an inductor current of a conventional voltage regulator.

2B is a waveform diagram of an inductor current signal and a low-side conduction reference current signal during an on-state of the low-side switch according to an embodiment of the present invention, wherein the inductor current signal is converted into a voltage form by the inductor current sensing unit. The reference current signal is also expressed in the form of voltage.

2C is a waveform diagram of a low side comparison signal corresponding to the intersection section of FIG. 2B.

FIG. 3 is a flowchart of a frequency modulation overcurrent protection method according to an embodiment of the present invention.

4 is a schematic diagram showing the frequency variation of a pulse width modulation signal when the time length of the crossover interval is gradually increased as provided by an example of the present invention.

Figure 5 is a partial circuit block diagram of a control circuit provided by an example of the present invention.

[An embodiment of an overcurrent protection method for frequency modulation of a voltage regulator and a circuit thereof]

Please refer to FIG. 1 and FIG. 3 simultaneously. FIG. 3 is a flowchart of a frequency modulation overcurrent protection method according to an embodiment of the present invention. The frequency-modulated overcurrent protection method of the present embodiment is for a voltage regulator, such as shown in FIG. 1, the voltage regulator having a high side switch 120, a low side switch 130, and an inductor 140. The high side switch 120 is electrically connected to the first end of the voltage input terminal Vin and the inductor 140. The low side switch 130 is electrically connected to the first end of the inductor 140 and the ground end 150, and the second end of the inductor 140 is connected to the voltage output terminal Vout. The high side switch 120 and the low side switch 130 may be, for example, a transistor switch, but the invention is not so limited. In general, as a voltage regulator, the high side switch 120 and the low side switch 130 are alternately turned on at a frequency of a pulse width modulation (PWM) signal. When the high side switch 120 is turned on, the inductor current I _{L of the} inductor 140 rises, which is indicated by the high side switch on period HS. When the low side switch 130 is turned on, the inductor current I _{L of the} inductor 140 decreases, and the low side switch is turned on during the LS period.

The method includes the following steps. First, in step S310, during the on-time period LS of the low-side switch 130, the inductor current signal of the voltage regulator (corresponding to the inductor current I _L ) is compared with the low-side conduction reference current signal to obtain a crossover interval CT, where The inductor current signal in the crossover interval CT is greater than the low side conduction reference current signal. The low side conduction reference current signal is a comparison reference of the inductor current I _L when the low side switch 130 is turned on (the low side switch on period LS), for example, the low side conduction reference current signal V _LSOC — ref of FIGS. 2B and 5 . The crossover interval is a time interval in which the inductor current I _{L is} greater than the comparison reference (low side conduction reference current signal), as shown in the subsequent FIG. 2B, and the detailed comparison manner will be further described later. The inductor current signal corresponds to the inductor current I _L and can be implemented, for example, in the form of a voltage in the design of the circuit, but the invention is not limited thereto. When the inductor current I _L during the on period of the low side switch 130 is greater than the comparison reference (low side conduction reference current signal), it means that the inductor current I _L on the inductor 140 is too large, and an over current condition may occur. The low-side conduction reference current signal as a comparison reference can be determined according to the actual circuit design, and serves as a basis for the overcurrent protection (OCP) triggering action. That is, step S310 is to determine whether an overcurrent condition has occurred (or will likely occur). Then, in step S320, the frequency of the pulse width modulation signal of the voltage regulator is linearly reduced according to the length of time of the intersection section CT (that is, the on-time of the current low-side switch is increased). When the time length of the crossover interval CT is longer, the frequency of the pulse width modulation signal is lower (that is, the longer the on-time of the current low-side switch is increased), and the shorter the time length of the crossover interval CT, the pulse The higher the frequency of the width modulation signal (ie, the shorter the conduction time of the current low side switch).

Further, according to the method step, the frequency-modulated overcurrent protection circuit of the embodiment includes an inductor current sensing unit and the control circuit 110 of FIG. The inductor current sensing unit is electrically connected to the inductor 140 for sensing the current of the inductor 140 to obtain an inductor current signal. The inductor current sensing unit is, for example, the first current sensing unit 210 or the second current sensing unit 220 of FIG. 5, and the art has an implementation of a sensing circuit that should be readily understood by a person skilled in the art to sense the current on the inductor. ,No longer. As shown in FIG. 1 , the control circuit 110 is electrically connected to the high side switch 120 and the low side switch 130 for controlling the high side switch 120 and the low side switch 130 , wherein the control circuit 110 is turned on during the low side switch 120 (LS). Comparing the inductor current signal of the voltage regulator (corresponding to the inductor current I _L ) with the low side conduction reference current signal to obtain a crossover interval CT, wherein the inductor current signal is greater than the low side conduction reference current in the crossover interval CT The signal, control circuit 110 linearly reduces the frequency of the pulse width modulation signal of the voltage regulator according to the length of time of the crossover interval CT.

Regarding the implementation of the step of the intersection section CT of step S310 and the step of linearly decreasing the frequency of the pulse width modulation signal of the voltage regulator according to the length of the intersection section CT of step S320, please refer to FIG. 2A, FIG. 2B and FIG. 5 and FIG. 2B are waveform diagrams of an inductor current signal and a low-side conduction reference current signal during a low-side switch conduction period according to an embodiment of the present invention, and FIG. 5 is a partial circuit block diagram of a control circuit provided by an example of the present invention. It should be noted that the control circuit of FIG. 5 is only one of the implementation manners of the embodiment of the present invention. The circuit of FIG. 5 is only for help, and the control-related logic circuit design is based on the control. In other embodiments, there are other The circuits of step S310 and step S320 of Fig. 3 are realized, and therefore, based on the description of the present embodiment, the art has a control circuit which is easily realized by other knowledge but with other functions but with the same function.

As shown in FIG. 5 , the inductor current sensing unit is implemented by the first current sensing unit 210 and the second current sensing unit 220 . When the high side switch is turned on during the high side switch 120, the first current sensing unit 210 senses the inductor current I _L . When the low side switch is turned on during the low side switch 130, the second current sensing unit 220 senses the inductor current I _L . The first current sensing unit 210 and the second current sensing unit 220 may also be the same circuit. The circuit representation of FIG. 5 is only used to represent the output signal of the state in different states, and is not intended to limit the present invention. .

The first current sensing unit 210 is electrically connected to the resistive component 230. The resistive component 230 is electrically connected to the ground terminal 250 such that the voltage V _sum is an inductor current signal when the high-side switch 120 is turned on. The comparison signal HSOC is obtained by comparing the voltage V _sum with the high side conduction current reference signal V _{HSOC —} ref by the comparator 260. The high-side conduction current reference signal V _{HSOC — ref} can be designed and determined according to the actual circuit, and the present invention is not limited thereto.

The second current sensing unit 220 is electrically connected to the resistive component 240. The resistive component 240 is electrically connected to the ground terminal 250 such that the voltage VSO is an inductor current signal when the low-side switch 120 is turned on (the low-side switch during the period LS). . As shown in FIG. 2B, the voltage VSO is a periodic signal, and the waveform of the voltage VSO when the low side switch 130 is turned on in each cycle is as in FIG. 2A. The comparison signal LSOB is obtained by comparing the voltage VSO with the low side on current reference signal V _{LSOC —} ref by the comparator 270. The low-side conduction current reference signal V _{LSOC — ref} may also be designed and determined according to an actual circuit, and the present invention is not limited thereto.

The comparison signal LSOB is input to the oscillating circuit 280 to linearly adjust the operating frequency for the pulse width modulation signal PWMin. The signal frequency output by the oscillating circuit 280 is transmitted to the logic unit 290. The logic unit generates a pulse width modulation signal PWMin according to the comparison signal HSOC, the comparison signal LSOB, and the signal frequency output by the oscillation circuit 280, and the pulse width modulation signal PWMin is used to control the high side. The duty cycle of the switch 120 and the low side switch 130, while the operating frequency of the pulse width modulation signal PWMin is the signal frequency output by the oscillating circuit 280. Those skilled in the art should readily understand the operation of voltage regulators that are pulse width modulated, whereby logic unit 290 of FIG. 5 and its associated circuit operations are also within the skill of the art and may be based on actual needs. Designed, will not repeat them here.

Based on the exemplary circuit of FIG. 5, in conjunction with FIG. 2A and FIG. 2B, if the inductor current I _{L of the} voltage regulator is gradually rising as shown in FIG. 2A during operation (ie, the current of the HS during each high-side switch is greater than the previous high) When the side switch is turned on during the current of the HS, and the current of each of the low side switch during the LS is greater than the current of the previous low side switch during the LS, when the low side switch 130 is turned on, the step S310 of the embodiment and the corresponding The operation of the control circuit compares the inductor current I _L represented by the voltage VSO with the low-side conduction current reference signal V _{LSOC_re} f , as shown in FIG. 2B , the crossover interval CT can be obtained, and the crossover interval CT is also the inductor current IL. A section larger than the comparison reference value (low side conduction current reference signal V _{LSOC — ref} ). Then, according to the crossover interval CT, the comparison signal LSOCB can be obtained, and the comparison signal LSOCB represents the time length of the crossover interval CT in each cycle. In FIG. 2C, the crossover interval CT is the low voltage level using the comparison signal LSOCB. (LOW) is shown, but the invention is not limited thereto. The comparison signal LSOCB indicates that the crossover interval CT can also be represented by a high voltage level (HIGH).

When the inductor current IL is larger, it can be found that the longer the time length of the crossover interval CT, the larger the inductor current IL as shown in FIG. 2A, the time length of the comparison signal LSOCB shown in FIG. 2C crossing the interval CT It is getting longer and longer. Thereby, the step S320 and the control circuit of the embodiment can linearly reduce the frequency of the pulse width modulation signal PWMin of the voltage regulator according to the time length of the crossover interval CT (that is, increase the current low side switch ON time). In an embodiment, according to the waveform of FIG. 2C, step S320 may periodically adjust the frequency of the pulse width variation signal PWMin, but the present invention is not limited thereto.

The manner of linearly adjusting the frequency of the pulse width modulation signal PWMin can be implemented, for example, by the oscillation circuit 280 of FIG. 5. The frequency output by the oscillation circuit 280 can be gradually decreased linearly according to the length of the intersection interval CT of the comparison signal LSOCB. . The oscillating circuit 280 linearly adjusts its output frequency according to the comparison signal LSOCB, whereby the operating frequency of the logic unit 290 can be linearly adjusted accordingly. As shown in FIG. 3, when the inductor current I _{L of} FIG. 2A is larger and larger, the amplitude of the frequency decrease of the pulse width modulation signal PWMin linearly decreases as the time length of the crossover interval CT increases. That is to say, the longer the time length of the crossover interval CT (the longer the on-time of the lower side switch is increased), the lower the frequency of the pulse width modulation signal PWMin, and the shorter the time length of the crossover interval CT ( The lower the on-time of the lower side switch is, the shorter the frequency is, and the higher the frequency of the pulse width modulation signal PWMin. In this way, the originally increasing inductor current I _L (the inductor current as shown in FIG. 2A) can be reduced due to the gradually decreasing frequency pulse width modulation signal PWMin, that is, the method according to the embodiment of the present invention can be used. The effect of the overcurrent protection is achieved by the fact that the inductor current IL rises due to the conventional circuit operation.

[Possible effects of the examples]

In summary, the embodiment of the present invention provides a frequency modulation overcurrent protection method for a voltage regulator and a circuit thereof, and the inductor current exceeds a comparison reference value according to the low side switch (the low side conduction reference current) The length of the crossover interval at the time of the signal) correspondingly linearly reduces the frequency of the pulse width modulation signal (i.e., increases the low side switch on time, thereby causing the current pulse width modulation signal frequency to decrease). That is, the frequency of the pulse width modulation signal linearly decreases as the inductor current when the low side switch is turned on exceeds the comparison reference value (low side conduction reference current signal). Furthermore, it can be seen from the present embodiment that, based on the length of the crossover interval, the longer the length of the crossover interval, the lower the frequency of the pulse width modulation signal (the longer the on-time switching time of the lower side switch increases) Crossover interval The shorter the length of time, the higher the frequency of the pulse width modulation signal (the shorter the on-time of the lower side switch is, the shorter it is), so that the purpose of linearly adjusting the frequency of the pulse width modulation signal can be achieved.

The above description is only an embodiment of the present invention, and is not intended to limit the scope of the invention.

Claims (8)

A frequency modulation overcurrent protection method for a voltage regulator having a high side switch, a low side switch, and an inductor, the method comprising: during the turning of the low side switch, the voltage One of the regulator inductor current signals is compared with a low side conduction reference current signal to obtain a crossover interval, wherein the inductor current signal is greater than the low side conduction reference current signal in the crossover interval; and according to the crossover interval The length of the time linearly reduces the frequency of a pulse width modulation signal of the voltage regulator; wherein the high side switch is electrically connected to a voltage input end and a first end of the inductor, and the low side switch is electrically connected to the inductor The first end is connected to a ground end, and the second end of the inductor is connected to a voltage output end. The frequency modulation overcurrent protection method of claim 1, wherein the high side switch and the low side switch are alternately turned on at a frequency of the pulse width modulation signal. The frequency-modulated overcurrent protection method of claim 1, wherein the amplitude of the frequency decrease of the pulse width modulation signal decreases linearly as the length of time of the intersection interval increases. According to claim 1, the frequency-modulated overcurrent protection method, wherein the step of linearly decreasing the frequency of the pulse width modulation signal of the voltage regulator according to the time length of the crossover interval is periodically Adjust the frequency of the pulse width modulation signal. A frequency-modulated overcurrent protection circuit for a voltage regulator having a high-side switch, a low-side switch, and an inductor, the frequency-modulated overcurrent protection circuit comprising: An inductor current sensing unit electrically connected to the inductor for sensing the current of the inductor to obtain an inductor current signal; and a control circuit electrically connected to the high side switch and the low side switch for controlling the a high side switch and the low side switch, wherein the control circuit compares the inductor current signal of the voltage regulator with a low side conduction reference current signal during the period of the low side switch to obtain a crossover interval. In the interval, the inductor current signal is greater than the low-side conduction reference current signal, and the control circuit linearly decreases the frequency of a pulse width modulation signal of the voltage regulator according to the length of the crossover interval; wherein the high-side switching electrical property Connecting a voltage input terminal and a first end of the inductor, the low side switch is electrically connected to the first end of the inductor and a ground end, and the second end of the inductor is connected to a voltage output end. The frequency-modulated overcurrent protection circuit of claim 5, wherein the amplitude of the frequency decrease of the pulse width modulation signal decreases linearly as the length of time of the crossover interval increases. According to claim 5, the frequency-modulated overcurrent protection circuit, wherein the step of linearly decreasing the frequency of the pulse width modulation signal of the voltage regulator according to the length of the crossover interval is periodically Adjust the frequency of the pulse width modulation signal. The frequency-modulated overcurrent protection circuit of claim 5, wherein the high-side switch and the low-side switch are alternately turned on at a frequency of the pulse width modulation signal.