TWM456022U - Switching regulator and control circuit thereof - Google Patents

Description

Switching power supply and its control circuit

The present invention relates to a switched power supply and a control circuit thereof, and more particularly to a switched power supply and a control circuit thereof for improving a voltage slew rate.

When supplying power to portable electronic devices, an earlier method is to use a step-down conversion method to provide a higher input voltage to the battery and convert it into a lower output voltage for supply to the portable electronic device. The conversion between the input voltage and the output voltage can be achieved, for example, using a buck switching power supply (Buck Switching Regulator).

With the improvement of battery technology, the battery voltage still has the power supply capability even if it is dropped to a low level. In this case, since the battery voltage is lower than the target value of the supply voltage, a boost type switching power supply (Boost Switching) is required. Regulator) to convert the lower input voltage to a higher output voltage.

The circuit structure of the step-up switching power supply is substantially as shown in FIG. 1. The step-up switching power supply 1 includes two power transistor switches QA and QB controlled by the control circuit 12; the control circuit 12 According to the feedback signal FB extracted from the output terminal OUT, the switch control signal is generated to control the opening and closing of the power transistor switches QA and QB to transfer the electric energy from the input terminal IN to the output terminal OUT, and the input voltage Vin is converted into an output. The voltage Vout is supplied to the load 19, such as but not limited to a power amplifier for a display panel in a portable electronic device (Power Amplifier). FIG. 2 shows an example of the internal structure of the control circuit 12. The error amplifier FB is compared with the reference voltage Vref by the error amplifier (EA) 16 to generate an error amplification signal VEA, and the PWM comparator 17 amplifies the error signal VEA with After the sawtooth signal is compared, a pulse width modulation (PWM) signal is generated, and then a sufficient driving voltage level is generated by the driving circuit 18 to drive the power transistor switches QA and QB in FIG. According to the principle of feedback control, when the circuit is balanced, the feedback signal FB will be equal to or have a known relationship with the reference voltage Vref, so changing the setting of the reference voltage Vref can change the target value of the output voltage Vout. The control mode shown in Fig. 2 is a voltage mode switching power supply, and the switching power supply can also be controlled by a current mode, the details of which are known to those skilled in the art. It is well known and will not be described here.

In addition to the step-up switching power supply 1 shown in Fig. 1, another prior art proposes a Buck-Boost Switching Regulator, as shown in Fig. 3. The step-up switching power supply 3 includes four power transistor switches QA-QD, which can be operated in boost and buck modes by switching between four power transistor switches, regardless of whether the input voltage is higher or lower than the output. The voltage works.

Figure 1 and Figure 3 show the synchronous switching power supply. If some of the power transistor switches are changed to diodes, they become asynchronous switching power supplies, such as the power in Figure 1. The transistor switch QB can be changed to a diode, or the power transistor switch QB and/or QD in Fig. 3 can be changed to a diode. For an example of the latter, please refer to the asynchronous boost type switching power supply of Fig. 4. Supply 3a.

A disadvantage of the prior art described above is that the boosted switching power supply has a lower current supply (as is the case when the buck-boost switching power supply operates in the boost mode), because In one cycle, a portion of the time current flows from the input IN through the power transistor switch QA to ground. Therefore, when the load 19 is switched from the standby state to the operating state and a higher voltage and current are required, the reaction time at which the overall circuit converts the input voltage Vin into the output voltage Vout is not fast enough. For example, please refer to Figure 5, the voltage slew rate required by the GSM specification is: the demand for a higher voltage from the load 19 (shown as a change in the reference voltage Vref), to the output voltage Vout to reach the target value It needs to be achieved within time T1, but the prior art described above at time T1, the output voltage Vout has not yet reached the required level, and the required level is not reached until time T2. Therefore, how to reduce the lack of prior art becomes a problem that needs to be overcome.

In view of this, the present invention proposes a switching power supply that can improve the voltage slew rate and its control circuit in view of the above-mentioned deficiencies of the prior art.

One of the purposes of this creation is to provide a switched power supply.

Another object of the present invention is to provide a control circuit for a switched power supply.

For the above purposes, in one of the points of view, the present invention provides a switched power supply comprising: a boost or buck-boost power stage, according to a first operational signal, controlling at least one of the power switches to An input voltage is converted to an output voltage to an output terminal; a first operating circuit generates the first operational signal according to the output voltage or its associated signal; and a bypass path circuit including a bypass transistor and a second operation a circuit, when the power supply needs to be quickly supplied to the output terminal, the second operating circuit turns on the bypass current crystal; when the input voltage Vin is equal to the output voltage, or equal to the output voltage plus a safety difference, the second The operating circuit turns off the bypass crystal.

In another opinion, this creation also provides a control of a switched power supply. a control circuit for controlling a boost or buck-boost power stage to convert an input voltage to an output voltage at an output, the control circuit comprising: a first operating circuit, generating a signal according to the output voltage or its associated signal The first operational signal controls the power stage; and a bypass path circuit includes a bypass transistor and a second operation circuit, the second operation circuit turns on the bypass crystal when the output is required to be quickly supplied to the output; when the input The second operating circuit turns off the bypass crystal when the voltage Vin is equal to the output voltage or equal to the output voltage plus a safety difference.

In a preferred embodiment, the bypass transistor includes a tunable polarity transistor having a parasitic diode of adjustable polarity direction or two series of connected transistors each having a parasitic phase of opposite polarity directions. Polar body. .

In a preferred embodiment, the first operating circuit generates the first operation signal according to the relationship between the output voltage or its associated signal and a reference voltage, and the switching power supply further includes: a reference voltage The setting circuit determines the reference voltage according to a set signal.

In a preferred embodiment, the second operating circuit controls the bypassing transistor to be turned on according to one of the following modes or a combination thereof: according to the level change of the reference voltage, setting according to the reference voltage setting circuit The signal, according to the level of the output voltage, or according to the relationship between the input voltage and the output voltage.

In a preferred embodiment, the second operating circuit controls the bypassing the crystal to be turned off according to one of the following modes or a combination thereof: according to the level of the output voltage, or according to the input voltage and the output voltage Relationship.

In a preferred embodiment, the bypass path circuit includes a low dropout regulator.

The details of the creation, the technical content, the features and the effects achieved by the present invention are more easily explained by the detailed description of the specific embodiments.

[study]

1‧‧‧Finding step-up switching power supply

3‧‧‧Sensual synchronous buck-boost switching power supply

3a‧‧‧Unknown non-synchronous buck-boost switching power supply

[this creation]

40‧‧‧Switching power supply

10‧‧‧Battery

12‧‧‧Control circuit

16‧‧‧Error amplifier

17‧‧‧PWM comparator

18‧‧‧Drive circuit

19‧‧‧ load

41‧‧‧Power level

42‧‧‧First operating circuit

43‧‧‧reference voltage setting circuit

44‧‧‧Input voltage detection circuit

45‧‧‧Bypass path circuit

451‧‧‧Second operation circuit

AVout‧‧‧ output voltage related signal

FB‧‧‧ feedback signal

IN‧‧‧ input

OUT‧‧‧ output

Q1‧‧‧ power-on crystal

QA~QD‧‧‧Power Switch

S1‧‧‧ first operation signal

S2‧‧‧second operation signal

TS1, TS2, T1, T2‧‧ ‧ time

VEA‧‧‧ error signal

Vin‧‧‧Input voltage

Vref‧‧‧reference voltage

Vout‧‧‧ output voltage

Figure 1 shows a schematic diagram of a prior art step-up switching power supply.

Figure 2 is a diagram showing the internal structure of a prior art control circuit.

Figure 3 shows a schematic diagram of a prior art synchronous buck-boost switching power supply.

Figure 4 shows a schematic diagram of a prior art non-synchronous buck-boost switching power supply.

Figure 5 shows the prior art voltage slew rate (Slew rate).

Fig. 6 is a view showing the switching power supply of the present embodiment.

Figures 7A-7F show several embodiments of power stage circuits.

Figure 8 shows the voltage slew rate (Slew rate) of this creation.

The above and other technical contents, features and effects of the present invention will be apparent from the following detailed description of the preferred embodiments. The directional terms mentioned in the following embodiments, such as up, down, left, right, front or back, etc., are only directions referring to the additional drawings. The drawings in this creation are all schematic representations, and are intended to represent the functional interaction between the various devices and components. The shapes, thicknesses, and widths are not drawn to scale.

Please refer to FIG. 6, which shows a schematic diagram of a switched power supply of an embodiment of the present invention. The switching power supply 40 of the present embodiment includes a power stage 41, a first operating circuit 42, an output voltage detecting circuit 43, a reference voltage setting circuit 44, and a bypass path circuit 45. The power stage 41 of this embodiment can be a synchronous or non-synchronous boost type (Boost) switching type. The power stage circuit, as shown in Figures 7A-7B, can be either a synchronous or non-synchronous Buck-Boost switching power stage circuit, as shown in Figure 7C-7F. Therefore, the switching power supply 40 of the embodiment can be a step-up switching power supply or a buck-boost switching power supply.

The output voltage detecting circuit 43 and the output end are coupled to the OUT for detecting the output voltage Vout to generate an output voltage related signal AVout. The output voltage detecting circuit 43 can be, for example, a resistor divider circuit, or if the level of the output voltage Vout is directly processed by the first operating circuit 42, the output voltage detecting circuit 43 can be omitted, and the first operation Circuit 42 can directly receive the output voltage Vout. The first operation circuit 42 generates a first operation signal S1 according to the input voltage related signal AVi to control the opening and closing of the power transistor switch in the power stage 41, thereby controlling the conversion between the input voltage Vin and the output voltage Vout; Circuit 42 is, for example but not limited to, a circuit that can be the second figure. The function of the reference voltage setting circuit 44 is to adjust the setting of the reference voltage Vref in the first operational circuit 42 in accordance with the set signal to change the target value of the output voltage Vout. The reference voltage setting circuit 44 can be omitted if the circuit application does not require changing the setting of the reference voltage Vref.

The first operating circuit 42, the output voltage detecting circuit 43, the reference voltage setting circuit 44, the bypass path circuit 45, and the power transistor switch in the power stage 41 may be integrated into a control circuit in whole or in part by integrated circuit fabrication techniques.

In this embodiment, when the load 19 is to enter the operating state from the standby state, the output voltage Vout needs to quickly reach a higher level from a lower level. At this time, the switching power supply 40 converts the input voltage Vin to the output voltage Vout to the output terminal OUT via the power stage 41 on the one hand, and simultaneously provides the direct input from the input terminal IN via the bypass path circuit 45. Power is supplied to the output terminal OUT.

In this embodiment, the bypass path circuit 45 includes, for example, a bypass transistor Q1 and a second operation circuit 451. When the power supply to the output terminal OUT needs to be quickly supplied, the second operation circuit 451 issues a second operation signal S2. The bypassing transistor Q1 is turned on. It should be noted that when the load 19 enters the stable operation state, the input voltage Vin is converted to the output voltage Vout for the boosting operation. At this time, the input voltage Vin is lower than the output voltage Vout, and cannot be simply turned on by the bypassing of the crystal Q1. The input terminal IN supplies power to the output terminal OUT, so the second operation circuit 451 turns on the bypass crystal Q1 only when the input voltage Vin is higher than the output voltage Vout, and turns off the bypass crystal Q1 when the input voltage Vin is equal to the output voltage Vout. . From a circuit control point of view, it is safer to do so when the input voltage Vin is not equal to and equal to the output voltage Vout (ie, when the input voltage Vin is only slightly higher than the output voltage Vout, Vin = Vout + ΔV, where ΔV can When a safety difference is determined by the designer, the bypass crystal Q1 is turned off.

The conduction of the bypass transistor Q1 can be controlled in various ways, for example, according to the level change of the reference voltage Vref, determined according to the setting signal received by the reference voltage setting circuit 44, determined according to the level of the output voltage Vout, or It is determined according to the relationship between the input voltage Vin and the output voltage Vout, and the like may be used in combination or in combination. In detail, if the level change of the reference voltage Vref or the set signal received by the reference voltage setting circuit 44 indicates that the output voltage Vout needs to rise from a lower level to a higher level, the bypass current crystal can be turned on. Q1. If the level of the output voltage Vout is lower than a certain level (the output voltage Vout or the output voltage related signal AVout can be compared with a reference level), the bypass crystal Q1 can also be turned on. For another example, when the output voltage Vout is lower than the input voltage Vin (the output voltage Vout or the output voltage related signal AVout can be compared with the related signal of the input voltage Vin or the input voltage Vin In comparison, the bypass crystal Q1 can also be turned on. In the last example (output voltage Vout is lower than the input voltage Vin), it is necessary to compare the relative relationship between the input voltage Vin and the output voltage Vout. At this time, the circuit can use a voltage detecting circuit (for example, a voltage dividing resistor) to obtain the input voltage Vin. The related signal, or directly input the input voltage Vin into the second operating circuit 451. The second operational circuit 451 can be a corresponding design depending on the control mode employed. In addition, the bypass crystal Q1 is not limited to being fully turned on; for example, the bypass path circuit 45 may be, but not limited to, a Low Drop Out (LDO) voltage regulator.

Please refer to Figure 8 (below Figure 5). When it is necessary to supply power to the output terminal OUT quickly (such as but not limited to the level change indicated by the reference voltage Vref), this creation is in time TS1, by the side. The action of the path circuit 45 causes the output voltage Vout to rapidly rise to be equal to or close to the input voltage Vin (the power stage 41 may or may not work during this time, but if the output voltage Vout rises naturally, the rate is naturally better), and In time TS2, when the output voltage Vout is equal to or close to the input voltage Vin, the bypass transistor Q1 can be turned off (the mode of the shutdown can be based on the level of the output voltage Vout or according to the relationship between the input voltage Vin and the output voltage Vout, or The combination of the two determines) that the switching power supply 40 converts the input voltage Vin to the output voltage Vout via the power stage 41 during this time. Thereby, the total time TS1+TS2 required for the switching power supply 40 to convert the input voltage Vin to the output voltage Vout is lower than the time T1 required by the GSM specification, and also lower than the time T2 required by the prior art. That is to say, the switched power supply 40 of the present invention can meet the voltage slew rate required by the GSM specification and is superior to the prior art.

It is worth noting that since the relative level relationship between the input voltage Vin and the output voltage Vout is not fixed, the design of the bypass transistor Q1 should take this into consideration. For example, the bypass transistor Q1 of the embodiment may include an adjustable a polar transistor, as shown in Figure 6, which has A parasitic diode with adjustable polarity. In another embodiment, the bypass crystal Q1 may be combined by two series connected transistors, each having a parasitic diode of opposite polarity direction, as shown in FIG. 6 below, that is, the second operation circuit 451 is issued second. The operation signal S2 simultaneously controls the two transistors (or at least controls the parasitic diodes in opposite directions to the current).

It should be noted that this creation is not limited to applications to solve the problem that the prior art does not comply with the GSM specifications. For example, in the case where the reference voltage Vref is fixed (the reference voltage setting circuit is not required at this time), the creation can also be performed when the power is turned on or restarted, or the load suddenly consumes a large amount of power so that the output voltage Vout suddenly drops sharply. The output voltage Vout is brought to the target level more quickly.

The present invention has been described above with reference to the preferred embodiments, and the above description is only for the purpose of making the present invention easy to understand the content of the present invention, and is not intended to limit the scope of the present invention. In the same spirit of the creation, those skilled in the art can think of various equivalent changes. For example, in the circuit of each embodiment shown, components that do not affect the main meaning of the signal, such as other switches, may be inserted; for example, each power switch QA~QD and the bypass transistor Q1 may be PMOS or NMOS, and the circuit may be used as a circuit. Corresponding transformations; for example, the second operational circuit 451 can be incorporated in the first operational circuit 42 without necessarily being a separate circuit. All of these can be derived from the teachings of this creation. Therefore, the scope of this creation should cover all of the above and all other equivalent changes. In addition, any implementation of the present invention does not necessarily have to achieve all of the objects or advantages, and therefore, the scope of the claimed patent should not be limited thereto.

40‧‧‧Switching power supply

10‧‧‧Battery

19‧‧‧ load

41‧‧‧Power level

42‧‧‧First operating circuit

43‧‧‧reference voltage setting circuit

44‧‧‧Input voltage detection circuit

45‧‧‧Bypass path circuit

451‧‧‧Second operation circuit

AVout‧‧‧ output voltage related signal

IN‧‧‧ input

OUT‧‧‧ output

Q1‧‧‧ power-on crystal

S1‧‧‧ first operation signal

S2‧‧‧second operation signal

Vin‧‧‧Input voltage

Vout‧‧‧ output voltage

Vref‧‧‧reference voltage

Claims (14)

A switching power supply comprising: a boosting or step-up power level, controlling at least one of the power switches according to a first operational signal to convert an input voltage into an output voltage at an output; An operation circuit, generating the first operation signal according to the output voltage or a related signal thereof; and a bypass path circuit including a bypass current crystal and a second operation circuit, when the power supply needs to be quickly supplied to the output terminal, the second operation The circuit turns on the bypass crystal; when the input voltage is equal to the output voltage, or equal to the output voltage plus a safety difference, the second operating circuit turns off the bypass crystal. The switching power supply device of claim 1, wherein the bypass current crystal comprises a tunable polarity transistor having a polarity-adjustable parasitic diode or two strings of transistors, each of which A parasitic diode having opposite polarity directions. The switching power supply of claim 1, wherein the first operating circuit generates the first operation signal according to the output voltage or a relationship between the related signal and a reference voltage, and the switching power supply The device further includes: a reference voltage setting circuit that determines the reference voltage according to a set signal. The switching power supply device of claim 3, wherein the second operating circuit controls the bypassing of the power-on crystal according to one of the following modes or a combination thereof: according to the level change of the reference voltage, according to the reference The setting signal received by the voltage setting circuit, the level according to the output voltage, or the relationship between the input voltage and the output voltage. The switching power supply of claim 1, wherein the first operating circuit generates the first operational signal according to the relationship between the output voltage related signal and a reference voltage, and wherein the second operational circuit is One of the following ways or a combination thereof to control the bypassing of the power-on crystal: according to the level change of the reference voltage, according to the output voltage The level of the input or the relationship between the input voltage and the output voltage. The switching power supply device of claim 1, wherein the second operating circuit controls the bypassing the crystal to be turned off according to one of the following modes or a combination thereof: according to the level of the output voltage, or according to The relationship between the input voltage and the output voltage. The switching power supply of claim 1, wherein the bypass path circuit comprises a low dropout regulator. A switching power supply control circuit controls a boost or buck-boost power stage to convert an input voltage into an output voltage at an output, the control circuit comprising: a first operating circuit, according to the output voltage Or a related signal, generating a first operation signal to control the power level; and a bypass path circuit comprising a bypass current crystal and a second operation circuit, the second operation circuit is turned on when it is required to rapidly supply power to the output terminal The power-on crystal is turned on; when the input voltage is equal to the output voltage, or equal to the output voltage plus a safety difference, the second operating circuit turns off the bypass crystal. The control circuit of the switching power supply device of claim 8, wherein the bypass current crystal comprises a tunable polarity transistor having a polarity-adjustable parasitic diode or two strings of connected transistors Each of them has a parasitic diode of opposite polarity directions. The control circuit of the switching power supply device of claim 8, wherein the first operating circuit generates the first operation signal according to the relationship between the output voltage or a related signal and a reference voltage, and the switching The power supply further includes: a reference voltage setting circuit that determines the reference voltage according to a set signal. The control circuit of the switching power supply according to claim 10, wherein the second operating circuit controls the conduction of the bypass crystal according to one of the following modes or a combination thereof: a level change according to the reference voltage And according to the reference signal received by the reference voltage setting circuit, according to the level of the output voltage, or according to the relationship between the input voltage and the output voltage. The control circuit of the switching power supply device of claim 8, wherein the first operating circuit generates the first operation signal according to the relationship between the output voltage related signal and a reference voltage, and wherein the second operation signal The operating circuit controls the bypassing of the crystal according to one of the following modes or a combination thereof: a level change according to the reference voltage, a level according to the output voltage, or a relationship between the input voltage and the output voltage. The control circuit of the switching power supply device of claim 8, wherein the second operating circuit controls the bypassing of the power-on crystal according to one of the following modes or a combination thereof: according to the level of the output voltage, Or based on the relationship between the input voltage and the output voltage. The control circuit of the switched power supply of claim 8, wherein the bypass path circuit comprises a low dropout regulator.