TW201316662A - Power circuit - Google Patents

Abstract

The invention discloses a power circuit, which includes an output terminal, a low drop-out regulator circuit, a soft start controlling circuit and a switching module. The soft start controlling circuit provides a soft start current. In a soft start mode, the switching module couples the start controlling circuit to the output terminal, such that the soft start current is utilized to charge the output terminal. In a low drop-out regulation mode, the switching module couples the low drop-out regulator circuit to the output terminal.

Description

Power circuit

This invention relates to a power supply circuit and, more particularly, to a slow start architecture for use on a power supply circuit.

As people become increasingly dependent on electronic products, the functionality of electronic products is complicated. In contrast, depending on the functional requirements, different power supply equipment is also required, such as the very common Low Drop-out Regulator (LDO) circuit. The low-dropout regulator stabilizes the output voltage at a specific voltage level by sampling the output voltage with a series resistor and using the sampled value to control the output voltage.

Low-dropout regulators are widely used in various consumer electronic products (such as mobile phones, tablet computers, etc.). In order to meet the requirements of these precision electronic products, a low-dropout regulator is added to the input end of the power supply to ensure the power supply voltage of the electronic products. Stability.

However, at the moment when the conventional low-dropout regulator is activated, the level of its output voltage suddenly rises. At this time, a large amount of inrush current is poured in a moment. Inrush current can cause electromagnetic interference (EMI) in the entire circuit system, affecting the normal operation of peripheral circuits, or it may burn circuit components.

Referring to FIG. 1, a schematic diagram of a conventional low dropout regulator circuit 120 is shown. As shown in FIG. 1, the low-dropout regulator circuit 120 is configured to generate an output signal OUT to the output stage 200 according to the input voltage Vin. The load on the output stage 200 can be represented by an output capacitor 220, and the output signal OUT has a voltage level Vout. .

In order to avoid circuit damage caused by the inrush current at the start-up instant, some conventional low-dropout regulator circuits 120 may couple the timing circuit 140 as a soft start effect. As shown in FIG. 1, the conventional timing circuit 140 forms a fixed charging time through the constant current source 142 and the constant capacitance 144, and controls the low-dropout regulator circuit 120 to have a fixed charging time as a low-dropout regulator. The slow start time of circuit 120.

However, the slow start effect formed by such a timing circuit is limited because the inrush current relationship of the low dropout regulator circuit 120 at startup is as follows: Where C _out is the capacitance value of the output capacitor 220.

The voltage change amount dV and the change time dT (the slow start time formed by the timer circuit 140) in the above formula are both fixed values, and if the output capacitance 220 of the output stage 200 is too large, an excessive inrush current value may be caused. Therefore, the use of a conventional timing circuit to generate a fixed slow start time does not effectively prevent excessive inrush current, and may still cause noise or damage to circuit components.

In order to solve the above problem, the present disclosure proposes a slow start control circuit, which can be used with a low dropout regulator circuit. The slow start control circuit of the present invention can dynamically adjust the length of the slow start time according to the output capacitor size of the output stage, such that In this way, the inrush current problem of the low-dropout regulator circuit at the start-up moment can be effectively avoided.

One aspect of the present disclosure is to provide a power supply circuit including an output terminal, a low dropout regulator circuit, a slow start control circuit, and a switching module. The slow start control circuit provides a slow start current. In the slow start mode, the switching module is coupled to the slow start control circuit to the output end, so that the slow start current charges the output end, and in the low dropout adjustment mode, the switching module is coupled to the low dropout regulator Circuit to the output.

In accordance with an embodiment of the present disclosure, the slow start current is a predetermined current.

According to an embodiment of the present disclosure, the power supply circuit is configured to generate an output signal to the output end, the switching module includes a comparator, and the comparator receives one of the feedback voltages according to the output signal. The reference level is slowly started, and a control signal is output after comparison to switch the slow start mode or the low drop difference adjustment mode.

According to an embodiment of the present disclosure, when the feedback voltage is less than the slow start reference level, the switching module switches to the slow start mode according to the control signal, and otherwise switches to the low drop difference adjustment mode.

According to an embodiment of the present disclosure, the low dropout regulator circuit includes an amplifier and a first transistor. In the low voltage differential mode, a gate of the first transistor is coupled to the amplifier via the switching module. The output end is coupled. In the slow start mode, the gate of the first transistor and the output end of the amplifier are disconnected.

According to an embodiment of the present disclosure, the slow start control circuit further includes a current source and a second transistor, and the second transistor is coupled to the current source. The switching module further includes a first switching unit and a second switching unit. The first switching unit is coupled between the output of the amplifier and the gate of the first transistor. The second switching unit is coupled between the gate of the first transistor and the gate of the second transistor. In the slow start mode, the second switching unit is turned on, and in the low drop difference adjustment mode, the first switching unit is turned on.

According to an embodiment of the present disclosure, in the slow start mode, the second switching unit is turned on, so that the first transistor and the second transistor form a current mirror, so that the current mirror of the current source The predetermined current is generated by the first transistor.

According to an embodiment of the present disclosure, the low-dropout regulator circuit further includes a reference voltage generator and a feedback loop, the reference voltage generator is coupled to the amplifier, and the reference voltage generator is configured to generate a reference voltage to the amplifier . The feedback loop is coupled between the output terminal and the amplifier, and the feedback loop is configured to return a feedback voltage according to the output signal to the amplifier.

According to an embodiment of the present disclosure, in the low dropout adjustment mode, the first transistor is configured to generate the output signal, and the amplifier adjusts the first transistor generated according to the feedback voltage and the reference voltage. The output signal.

According to an embodiment of the present disclosure, the power supply circuit further includes a voltage dividing sampling module coupled to the first transistor and the output end, and the voltage dividing sampling module is configured to be based on the output The signal is subjected to partial voltage sampling to generate the feedback voltage.

In accordance with an embodiment of the present disclosure, one of the slow start modes has a duration that dynamically changes with an output capacitance on the output.

In accordance with an embodiment of the present disclosure, the length of the duration is proportional to the magnitude of one of the output capacitors on the output.

In order to make the description of the present disclosure more complete and complete, reference is made to the accompanying drawings and the accompanying drawings. However, the embodiments provided are not intended to limit the scope of the present invention, and the description of the operation of the circuit structure is not intended to limit the order of execution thereof. Any device that is recombined by components and produces equal devices is The scope of the invention is covered. On the other hand, well-known elements and steps are not described in the embodiments to avoid unnecessarily limiting the invention.

Referring to FIG. 2, a functional block diagram of a power supply circuit 300 in accordance with an embodiment of the present invention is shown. The power circuit 300 is configured to generate an output signal OUT to the output terminal 400 according to the input voltage, and the output signal OUT has a voltage level Vout. In this embodiment, the power supply circuit 300 includes a low dropout regulator circuit 320, a slow start control circuit 340, and a switching module 360. The low-dropout regulator circuit 320 is used to adjust the voltage level Vout of the output signal OUT, and the voltage level Vout can be stabilized at the rated output voltage by the feedback control method, thereby achieving the voltage stabilization effect of the stable voltage level Vout.

Generally, when the low-dropout regulator circuit 320 is activated, that is, when the input voltage is initially activated (such as connecting to a power outlet or turning on a power switch, etc.) and the low-dropout regulator circuit 320 starts to provide an output signal OUT, In particular, a momentary change in voltage level Vout may result in a large inrush current.

Therefore, the slow start control circuit 340 in this embodiment is configured to provide a slow start current Isoft for performing the slow start of the power circuit 300.

In an actual circuit, the load on output 400 is represented by output capacitor 420. In a slow start mode, the switching module 360 is coupled to the slow start control circuit 340 to the output terminal 400, so that the slow start current Isoft charges the load of the output terminal 400. The slow start current Isoft has a fixed current value, and the fixed current value can be Set to the amount of operating current that the circuit components in the load can withstand. The load (here represented by the output capacitor 420) is charged by the slow start current Isoft with a fixed current value, so that the voltage level Vout of the output signal OUT is gradually increased until the sample value of the voltage level Vout of the output signal OUT reaches a slow start. Reference level.

On the other hand, in the low-dropout adjustment mode, the switching module 360 is coupled to the low-dropout regulator circuit 320 to the output terminal 400, and uses the low-dropout regulator circuit 320 to generate a stable output signal OUT, thereby implementing the power supply circuit 300. Low dropout regulator function under normal operating conditions.

Embodiments of the power supply circuit 300 of the present invention are exemplified below using a circuit architecture. Please refer to FIG. 3 together. FIG. 3 is a schematic circuit diagram of the power supply circuit 300 according to an embodiment of the present invention. As shown in FIG. 3, the power supply circuit 300 includes a low dropout regulator circuit 320, a slow start control circuit 340, and a switching module 360.

The low dropout regulator circuit 320 includes an amplifier 322, a transistor M1, a reference voltage generator 324, and a feedback loop 326.

The output of the amplifier 322 is coupled to the gate of the transistor M1 for adjusting the conduction state of the transistor M1, whereby the amplifier 322 can control the voltage level Vout of the output signal OUT generated by the transistor M1.

The two input terminals of the amplifier 322 are respectively coupled to the reference voltage generator 324 and the feedback circuit 326. The reference voltage generator 324 is configured to generate a reference voltage to the amplifier 322, and the reference voltage can be used to determine the rated output voltage of the output signal OUT. Bit. The feedback loop 326 is coupled between the output pole 400 and the amplifier 322.

The feedback loop 326 is used to feedback the feedback voltage generated by the output signal OUT to the amplifier 322, where the feedback voltage can be directly the voltage level Vout of the output signal OUT or the sampling level generated according to the output signal OUT. Vadj. In this example, the power circuit 300 further includes a voltage dividing sampling module 380 coupled between the feedback circuit 326 and the output stage 400. The voltage dividing sampling module 380 is configured to generate a feedback voltage according to the voltage sampling of the output signal OUT. The feedback loop 326 is fed back according to the sampling level Vadj as a feedback voltage, but the invention is not limited thereto.

It should be noted that, in the actual circuit application, in order to facilitate the processing of the signal, the present embodiment uses the voltage dividing sampling module 380 to sample the sampling level Vadj of the output signal voltage level Vout as a feedback voltage, and uses it to perform various ratios. For the operation, the present invention is not limited thereto. In other embodiments, the voltage level Vout can be directly used as the feedback voltage for comparison. In the following description, if the sampling level Vadj is used, it may be directly implied. The voltage level Vout is used.

As shown in FIG. 3, the slow start control circuit 340 includes a current source 342 and a transistor M2. Wherein, the transistor M2 is coupled to the current source 342. The transistor M2 of the slow start control circuit 340 is selectively coupled to the gate of both the transistor M1 in the low dropout regulator circuit 320.

The switching module 360 includes a comparator 362, a switching unit S1, and a switching unit S2. The switching unit S1 is coupled between the output of the amplifier 322 and the gate of the transistor M1. The switching unit S2 is coupled between the gate of the transistor M1 and the gate of the transistor M2.

The switching unit S1 and the switching unit S2 are controlled by the output end of the comparator 362, and the comparator 362 receives the feedback voltage (in this example, the sampling level Vadj) obtained from the output signal OUT and the slow start reference level. Vref, after comparing the two, outputs a control signal Con for controlling whether the switching unit S1 and the switching unit S2 are turned on to switch the slow start mode or the low drop difference adjustment mode. When the feedback voltage (in this example, the sampling level Vadj) is less than the slow start reference level Vref, the switching module 360 switches to the slow start mode according to the control signal Con, otherwise switches to the low dropout adjustment mode.

Please refer to FIG. 4A, FIG. 4B and FIG. 5 together. FIG. 4A is a schematic diagram of the switching module 360 switched to the slow start mode in FIG. 3, and FIG. 4B is shown in FIG. The switch module 360 switches to a schematic diagram of the low dropout adjustment mode. FIG. 5 is a schematic diagram showing the timing of the signal after the power supply circuit 300 in FIG. 3 is started.

As shown in FIG. 4A and FIG. 5, when the power supply circuit 300 is initially started, the input voltage Vin changes to a high level. At this time, the sampling level Vadj of the voltage level Vout of the output signal is less than the slow start reference level Vref. That is, Vadj<Vref, when the comparator 362 in the switching module 360 compares that the feedback voltage (Vadj in this example) is less than the slow start reference level, the control signal Con is generated to switch to the slow start mode. At this time, the switching unit S1 in the switching module 360 is open and the switching unit S2 is turned on, so that the low-dropout regulator circuit 320 is switched to the slow-start mode, and the current mirror structure formed by the transistor M1 and the transistor M2 is used to make electricity. The output signal OUT generated by the crystal M1 has a fixed current value, which can be determined by the current source 342. The sampling level Vadj in FIG. 5 is obtained by voltage sampling of the voltage level Vout, so the changing waveforms are the same, and only the voltage magnitudes are different.

It should be added that, in the slow start mode, since the switching unit S1 is open circuit, the gate of the transistor M1 and the output end of the amplifier 322 are disconnected at this time, that is, the output of the amplifier 322 is not at this time. Influencing the conduction state of the transistor M1. At this time, in the slow start mode, the switching unit S2 is turned on, so that the transistor M1 and the transistor M2 form a current mirror, so that the current flowing through the current source 342 is mirrored on the transistor. M1 causes the transistor M1 to generate a slow start current Isoft of a predetermined current value.

At this time, as shown in FIGS. 4A and 5, the output terminal 400 charges the load on the output terminal (in this example, the output capacitor 420) with a slow start current Isoft, so that the voltage level Vout of the output signal OUT gradually Slowly improve. In this embodiment, the slow start mode continues until the sampling level Vadj reaches the slow start reference level Vref.

The setting of the slow start reference level Vref may correspond to 80% of the rated output voltage of the low dropout regulator circuit 320. In this example, the slow start reference level Vref may be 80% of the rated output voltage multiplied by the partial pressure sampling. The sampling ratio of the module 380, but the present invention is not limited to the above 80% or a specific sampling ratio, and the slow start reference level Vref can be set to any suitable slow start threshold voltage value.

It should be particularly noted that, in the slow start mode of the embodiment, the transistor M1 is switched to the state of the current mirror, and the slow start current Isoft of the predetermined current magnitude is generated to charge the output capacitor 420, so that the voltage of the output signal OUT is accurate. Bit Vout gradually increased gradually. In this way, the current value of the output signal OUT at the initial startup is limited by the predetermined current of the slow start current Isoft, so that an excessive inrush current is not generated. Moreover, the slow start mode of the present embodiment has a duration Tss (as shown in FIG. 5) proportional to the magnitude of the output capacitor 420, that is, the duration Tss may dynamically change with the output capacitance 420 on the output stage 400.

When the sampling level Vadj reaches the slow start reference level Vref, that is, Vadj>Vref, when the comparator 362 in the switching module 360 compares that the feedback voltage (in this example, Vadj) is greater than the slow start reference level. When referring to FIG. 4B and FIG. 5, the switching module 360 switches to the low-dropout adjustment mode, and the control signal Con generated by the comparator 362 in the switching module 360 turns on the switching unit S1 and the switching unit S2 is turned off. 322 adjusts the output signal OUT generated by the transistor M1 according to the feedback of the feedback loop 326 and the reference voltage generator 324. Thereby, the voltage regulation effect of the output signal OUT is achieved by the low-dropout regulator circuit 320, and the power supply circuit 300 is realized. Low dropout regulator function under normal operating conditions.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and modified without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

120. . . Low dropout regulator circuit

200. . . Output stage

140. . . Timing circuit

142. . . Constant current source

144. . . Constant capacitance

220. . . Output capacitor

300. . . Power circuit

400. . . Output stage

320. . . Low dropout regulator circuit

362. . . Comparators

340. . . Slow start control circuit

360. . . Switching module

OUT. . . Output signal

420. . . Output capacitor

Vin. . . Input voltage

Vout. . . Voltage level

324. . . Reference voltage generator

326. . . Feedback loop

380. . . Partial pressure sampling module

342. . . Battery

M1. . . Transistor

M2. . . Transistor

S1. . . Switching unit

S2. . . Switching unit

Vadj. . . Sampling level

Vref. . . Slow start reference level

Tss. . . duration

322. . . Amplifier

Con. . . control signal

The above and other objects, features, advantages and embodiments of the present invention will become more apparent and understood.

1 is a schematic diagram of a conventional low dropout regulator circuit;

2 is a functional block diagram of a power supply circuit according to an embodiment of the invention;

3 is a circuit diagram of a power supply circuit in accordance with an embodiment of the present invention;

FIG. 4A is a schematic diagram showing the switching module switched to the slow start mode in FIG. 3;

FIG. 4B is a schematic diagram showing the switching module switched to the low dropout adjustment mode in FIG. 3;

FIG. 5 is a schematic diagram showing the timing of the signal after the power circuit is started in FIG. 3.

300. . . Power circuit

400. . . Output stage

320. . . Low dropout regulator circuit

362. . . Comparators

340. . . Slow start control circuit

360. . . Switching module

OUT. . . Output signal

420. . . Output capacitor

Vin. . . Input voltage

Vout. . . Voltage level

324. . . Reference voltage generator

326. . . Feedback loop

380. . . Partial pressure sampling module

342. . . Battery

M1. . . Transistor

M2. . . Transistor

S1. . . Switching unit

S2. . . Switching unit

Vadj. . . Sampling level

Vref. . . Slow start reference level

322. . . Amplifier

Con. . . control signal

Claims (12)

A power supply circuit comprising: an output terminal; a low dropout regulator circuit; a slow start control circuit to provide a slow start current; and a switching module coupled to the slow start control circuit in a slow start mode The output terminal causes the slow start current to charge the output terminal. In a low dropout adjustment mode, the switching module is coupled to the low dropout regulator circuit to the output end. The power supply circuit of claim 1, wherein the slow start current is a predetermined current. The power supply circuit of claim 1, wherein the power supply circuit is configured to generate an output signal to the output end, the switching module includes a comparator, and the comparator receives a feedback voltage according to the output signal. A slow start reference level, after comparison, a control signal is output to switch the slow start mode or the low drop difference adjustment mode. The power supply circuit of claim 1, wherein when the feedback voltage is less than the slow start reference level, the switching module switches to the slow start mode according to the control signal, otherwise switches to the low drop difference adjustment mode. The power supply circuit of claim 1, wherein the low dropout regulator circuit comprises: an amplifier; and a first transistor, wherein the gate of the first transistor passes the switching module in the low voltage differential mode And coupled to the output end of the amplifier, in the slow start mode, the gate of the first transistor and the output end of the amplifier are open. The power supply circuit of claim 5, wherein the slow start control circuit further comprises: a current source; and a second transistor coupled to the current source; wherein the switching module further comprises: a first switch a unit coupled between the output of the amplifier and the gate of the first transistor; and a second switching unit coupled to the gate of the first transistor and the gate of the second transistor In the slow start mode, the second switching unit is turned on, and in the low drop difference adjustment mode, the first switching unit is turned on. The power supply circuit of claim 6, wherein in the slow start mode, the second switching unit is turned on, so that the first transistor and the second transistor form a current mirror, so that the current of the current source Mirroring the first transistor produces the predetermined current. The power supply circuit of claim 5, wherein the low dropout regulator circuit further comprises: a reference voltage generator coupled to the amplifier, the reference voltage generator for generating a reference voltage to the amplifier; and a feedback The loop is coupled between the output terminal and the amplifier, and the feedback loop is configured to return a feedback voltage according to the output signal to the amplifier. The power supply circuit of claim 8, wherein in the low dropout adjustment mode, the first transistor is configured to generate the output signal, and the amplifier adjusts the first transistor according to the feedback voltage and the reference voltage. The output signal. The power supply circuit of claim 3 or claim 8, further comprising a voltage dividing sampling module coupled to the first transistor and the output end, wherein the voltage dividing sampling module is used The feedback voltage is generated by performing voltage division sampling according to the output signal. The power supply circuit of claim 1, wherein one of the slow start modes has a dynamic change with an output capacitance of the output. The power supply circuit of claim 11, wherein the duration is proportional to the magnitude of one of the output capacitors on the output.