WO2010017718A1

WO2010017718A1 - Soft start method, device and system for power supply

Info

Publication number: WO2010017718A1
Application number: PCT/CN2009/072046
Authority: WO
Inventors: 程航; 李定; 宋伟
Original assignee: 华为技术有限公司
Priority date: 2008-08-15
Filing date: 2009-05-31
Publication date: 2010-02-18
Also published as: CN101340142A; CN101340142B

Abstract

A soft start method, device and system for a power supply. A small duty cycle signal generation unit (320, 122) receives a clock signal (CLK) and generates a signal with a small duty cycle according to the clock signal (CLK). The signal with a small duty cycle is output to a switch (330, 123) and controls the switch (330, 123) to switch on and off periodically. When the switch (330, 123) turns on, a charging current charges a capacitor (340, 124) through the switch (330, 123). When the switch (330, 123) turns off, the charging current is cut off. An analog multiplexer (350, 125) compares the voltage of the capacitor (340, 124) with a reference voltage (V_REF), and outputs the smaller one to one input of an error amplifier (360, 126). Another input of the error amplifier (360, 126) is connected to a feedback voltage (V_FB).

Description

Method, device and system for soft start of power supply

This application claims priority to Chinese Patent Application No. 200810147430.0, entitled "A Method, Apparatus and System for a Soft Start of Power Supply", filed on August 15, 2008, the entire contents of which are incorporated by reference. In this application.

Technical field

The embodiments of the present invention relate to the field of communications, and in particular, to a method, an apparatus, and a system for power soft start. Background technique

In the application of the power management chip or the power management control chip, it is generally required that the output power supply is slowly rising from the startup to the stable process, thereby avoiding possible voltage or current overshoot and causing damage to the system or the chip; The difference in application often imposes specific requirements on the rise time of the power supply, and this poses certain challenges to the design of the power management chip or system due to cost factors.

The prior art uses an integrator composed of an external resistor and a capacitor to implement a soft start function. As shown in FIG. 1, the dotted line frame includes an external resistor R, an external capacitor C, and a common ground. When the input voltage VJN is applied to the system, the chip first uses the soft-start function. The voltage on the capacitor C rises slowly from zero volts. During the rising process, if the voltage on the capacitor C is lower than VRE _F (reference source voltage;) , then the voltage input to the ERROR AMP (error amplifier) through the ANALOG MUX circuit is a slowly rising voltage signal below VRE _F. The output voltage V _OUT also rises slowly through the negative feedback control of the entire loop, thereby achieving the soft start function of the output power. The soft start time is determined by the size of the external resistor R and the external capacitor C. When the voltage on capacitor C continues to rise until it is greater than VRE _F , the voltage input to ERROR AMP through the ANALOG MUX circuit is VRE _F , which is maintained thereafter, thereby keeping the output power of the system constant.

In the process of implementing the present invention, the inventors have found that at least the following problems exist in the prior art: The soft start time is short; the soft start time is poorly adjustable. Summary of the invention Embodiments of the present invention provide a method, device, and system for soft start of a power supply, so as to realize a long-term soft start function with a small chip area, and can flexibly change the time of soft start of the power supply.

According to an aspect of the present invention, a method for soft start of a power supply is provided, comprising the steps of: detecting a clock signal;

Generating a duty cycle signal based on the detected clock signal;

The duty cycle signal is outputted to the switch to control the closing of the switch, thereby controlling the charging of the capacitor to achieve soft start of the power source.

According to another aspect of the present invention, an apparatus for soft start of a power supply is provided, including:

a detecting unit, configured to detect a clock signal;

a duty ratio generating unit, configured to generate a duty cycle soft start unit according to the clock signal detected by the detecting unit, configured to output the duty ratio signal generated by the duty ratio generating unit to the switch, and control the switch The closing, in turn, controls the charging of the capacitor to achieve a soft start of the power supply.

According to another aspect of the present invention, a system for power soft start is provided, including:

a duty cycle circuit, a switch, a capacitor, an analog multiplexer, an error amplifier, and a pulse modulation control circuit;

The closing of the switch is controlled by the duty cycle circuit, and the charging time of the capacitor is controlled by the duty cycle circuit; when the current charges the capacitor, the capacitor integrates the charge, and the voltage rises stepwise Comparing the voltage of the capacitor with a reference source voltage, outputting a smaller value of the capacitor voltage and the reference source voltage to the error amplifier; outputting a voltage to the error amplifier by the analog multiplexer The pulse modulation control circuit further increases the output voltage slowly by the negative feedback of the entire circuit, thereby realizing the soft start function of the output power supply.

According to another aspect of the present invention, there is also provided another system for power soft start, comprising: a duty cycle circuit, a switch, a capacitor, an analog multiplexer, and a voltage output subunit;

a duty cycle circuit for detecting a clock signal, generating a duty cycle signal according to the detected clock signal, outputting the duty cycle signal to the switch, and controlling closing of the switch;

The switch is respectively connected to the charging current and the capacitor for opening or closing under the control of the duty cycle circuit, thereby controlling the charging current to charge the capacitor;

An analog multiplexer for determining the voltage of the capacitor voltage or the lower plate voltage of the capacitor and the reference source voltage. Receiving a smaller voltage therein, outputting the smaller voltage to an error amplifier;

A voltage output subunit for generating an output voltage according to a voltage input by the analog multiplexer.

In the embodiment of the present invention, the soft start time is extended by the soft start circuit, and the soft start function can be realized for a longer time under the same chip area; the power supply can be flexibly changed by adjusting the size of the capacitor, the size of the duty cycle, and the length of the clock cycle. The time of startup. DRAWINGS

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 embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description For some embodiments of the present invention, other drawings may be obtained from those skilled in the art without departing from the drawings.

1 is a circuit diagram of an implementation of the prior art;

2 is a schematic flowchart of a method for providing a method according to an embodiment of the present invention;

3 is a circuit 1 of an implementation circuit of a method according to an embodiment of the present invention;

4 is a schematic flowchart 1 of a method for providing a method according to an embodiment of the present invention;

5a is a schematic diagram 1 of a method for implementing a small duty cycle according to an embodiment of the present invention;

FIG. 5b is a second schematic diagram of a method for implementing a small duty cycle according to an embodiment of the present invention; FIG.

6 is a schematic diagram of a soft start waveform of a method according to an embodiment of the present invention;

FIG. 7 is a circuit diagram 2 of an implementation method of a method according to an embodiment of the present invention; FIG.

8 is a circuit diagram 3 of an implementation method of a method according to an embodiment of the present invention;

FIG. 9 is a schematic flowchart 2 of a method for providing a method according to an embodiment of the present invention;

FIG. 10 is a schematic diagram of a basic structure of an apparatus according to an embodiment of the present invention; FIG.

FIG. 11 is a schematic structural diagram of a device according to an embodiment of the present invention;

FIG. 12 is a schematic diagram of a system according to an embodiment of the present invention. detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, one of ordinary skill in the art does not create All other embodiments obtained under the premise of sexual labor are within the scope of protection of the present invention. The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

FIG. 2 is a schematic diagram of a basic process of a method according to an embodiment of the present invention.

Embodiments of the present invention provide a method for soft start of a power supply, including the following steps:

Step s210, detecting a clock signal;

Step s220, generating a duty cycle signal according to the detected clock signal;

Step s230, outputting the above duty ratio signal to the switch, controlling the closing of the switch, thereby controlling the charging of the capacitor, and realizing the soft start of the power source. The embodiments of the present invention are further described in detail below. The duty cycle circuit takes a small duty cycle circuit as an example, and the switch uses a PMOS (P-channel metal oxide semiconductor) transistor as an example, and the charging current is generated by a current source.

The device of the embodiment of the present invention, as shown in FIG. 3, includes: a built-in current source 1 310, a small duty cycle circuit 320, a switch Ml 330, a built-in capacitor C 340, an analog multiplexer ANALOG MUX 350, and an error amplifier ERROR AMP 360.

The current source I 310 generates a charging current, which is output to the capacitor C 340 through the switch M1 330. The closing of the switch M1 330 is controlled by the small duty cycle circuit 320, and thus the charging time of the capacitor C 340 is controlled. When the current charges the capacitor C 340, the capacitor C 340 integrates the charge and the voltage rises stepwise; the analog multiplexer ANALOG MUX 350 compares the voltage of the capacitor C 340 with the reference source voltage, and outputs the smaller of the two to the error amplifier. ERROR AMP 360; The voltage is output by ERROR AMP 360, and the output voltage V _{OUT is} slowly increased by the negative feedback of the entire loop to realize the soft start function of the output power.

Wherein, the current source I 310 is used to generate a charging current; the small duty circuit 320 is used to control the switch to close; the switch Ml 330 is used to control the charging time of the capacitor; and the capacitor C 340 is used to integrate the charge to make the voltage ladder Analog riser; analog multiplexer ANALOG MUX 350, used to receive the smaller voltage value of capacitor C 340 and the reference source voltage, input to the error amplifier ERROR AMP 360; ERROR AMP 360, used to receive the voltage of the ANALOG MUX 350 input, Through the negative feedback of the whole loop, the output voltage V _{OUT is} slowly increased to realize the soft start function of the output power. As shown in FIG. 4, an embodiment of the present invention provides a method for soft start of a power supply, including the following steps: Step s410: An input power supply VIN is loaded into a soft start circuit, and a current source I outputs a charging current; a current source outputting a charging current is Constant value.

Step s420, the small duty cycle circuit detects the clock signal, and generates a small pulse signal according to the detected clock signal;

As shown in Figures 5a and 5b, respectively, a method for realizing a small duty cycle; in Fig. 5a, a small duty cycle is realized by an odd-numbered inverter and a NAND gate; in Fig. 5b, an odd-numbered inverter is used and/or The gate achieves a small duty cycle. A small duty cycle generating circuit can detect the rising or falling edge of the clock CLK signal, thereby generating a square wave with a small pulse width.

Step s430, the small duty cycle signal is transmitted to the switch M1 to control the switch M1 to be closed; the switch M1 is a PMOS transistor, when the high level signal in the small duty cycle signal is transmitted, the switch M1 is closed; otherwise, the switch M1 is off open.

Step s440, when the switch M1 is closed, the current generated by the current source I is charged to the capacitor C through the switch M1, so that the voltage of the capacitor C is stepped up;

The closing of the switch M1 is controlled by the small duty cycle signal. Since the small duty cycle signal is generated according to the clock cycle, the small duty cycle signal is controlled by changing the period of the clock signal, so that the closing time of the switch M1 can be adjusted. .

Since the pulse width of the voltage square wave in the small duty cycle signal is 4 ,, the capacitor C is charged for only a short period of time in one clock cycle, and the voltage of the capacitor C rises slowly and rises stepwise.

Step s450, ANALOG MUX determines the voltage of the capacitor C and the reference source voltage, receives the smaller of the two voltages and inputs the voltage to the ERROR AMP; ERROR AMP through the negative feedback of the entire loop output voltage;

Since the voltage on capacitor C rises slowly from zero volts, if the voltage on capacitor C is lower than the reference source during the rise

Voltage, then, as shown in Figure 6, the voltage input to the ERROR AMP after passing through the ANALOG MUX circuit is a slowly rising voltage signal lower than VRE _F ; ERROR AMP is controlled by the negative feedback of the entire loop so that the output voltage V _OUT is also Slow rise; When the voltage on the capacitor C is greater than the reference source voltage, the reference source voltage is always output to stabilize the output voltage, thereby achieving the soft start function of the output power. Capacity, cost savings; extended soft-start time by soft-start circuit, can achieve longer soft-start function under the same chip area; by adjusting the size of capacitor C, the size of current source I, the size of duty cycle and The length of the clock cycle can flexibly change the time of the soft start of the power supply. The embodiment of the invention further provides a method for soft-starting a power supply using a resistor R instead of a current source. As shown in FIG. 7, after a voltage is applied, a charging current is generated under the influence of a voltage difference.

The difference from the soft-start circuit using a current source is that the current of the soft-start circuit using the current source is constant current, and when the circuit of the resistor R is used, the magnitude of the current is affected by the applied voltage and the capacitor voltage, with the charging time. The increase has changed. The above-mentioned alternative circuit eliminates the problem that the capacitance voltage increase nonlinearity existing in the prior art is eliminated due to the use of periodic charging. The embodiment of the present invention further provides a method for gradually changing the voltage from high to low. As shown in FIG. 8, the circuit diagram of the method is as shown in FIG. 9, and includes the following steps:

Step 910, the input voltage is applied to both ends of the capacitor, and the voltage value of the lower plate of the capacitor is greater than the reference source voltage value. The ANALOG MUX compares the voltage of the lower plate of the capacitor with the reference source voltage, and transmits the reference source voltage with a smaller voltage value to the ERROR AMP. At this point, the entire loop output voltage is the largest.

Step 920, the small duty cycle generating circuit generates a small duty cycle signal, controls the closing of the switch, the capacitor is gradually charged, the capacitor voltage is stepwise increased, and the voltage of the lower plate of the capacitor is stepwise reduced.

Step 930, when the voltage of the lower plate of the capacitor is less than the reference source voltage value, the ANALOG MUX compares the two sizes and outputs the smaller capacitor lower plate voltage value to the ERROR AMP. At this time, the voltage of the lower plate of the capacitor gradually increases. Decrease, the entire loop output voltage is reduced.

As the capacitor is continuously charged, the capacitor voltage is stepped up. The ANALOG MUX transmits the stepped reduced capacitor lower plate voltage to the ERROR AMP, and the entire loop output voltage decreases with the stepwise decrease of the capacitor lower plate voltage. , to achieve a slow change in output power from high to low. The embodiment of the present invention further provides a device for soft-starting a power supply, as shown in FIG. 10, including: a detecting unit 1010, configured to detect a clock signal;

a duty ratio generating unit 1020, configured to generate a duty cycle signal according to the detected clock signal; The soft start unit 1030 is configured to output a duty cycle signal to the switch, control the closing of the switch, and thereby control the charging of the capacitor to implement soft start of the power source. The embodiment of the invention further provides a device for soft start of the power supply, as shown in FIG. 11, comprising: a loading unit 1110, configured to load an input power source.

The detecting unit 1120 is configured to detect a clock signal.

The duty ratio generating unit 1130 is configured to generate a duty cycle signal according to the detected clock signal. The soft start unit 1140 is configured to output a duty cycle signal to the switch, control the closing of the switch, and thereby control the charging of the capacitor to implement soft start of the power source.

The soft start unit 1140 includes:

a switch control subunit 1141 for periodically closing the duty cycle signal control switch;

The capacitor charging sub-unit 1142 is configured to periodically pass the charging current through the switch to increase the capacitor voltage stepwise;

The voltage judging subunit 1143 is used for the analog multiplexer. The ANALOG MUX determines the level of the capacitor voltage and the reference source voltage, and receives a smaller voltage value of the capacitor voltage and the reference source voltage;

The voltage output subunit 1144 is used for the ANALOG MUX to input the received voltage to the error amplifier ERROR AMP, and then output the voltage to achieve soft start of the output power. Capacity, cost savings; extended soft-start time by soft-start circuit, can achieve longer soft-start function under the same chip area; by adjusting the size of capacitor C, the size of current source I, the size of duty cycle and The length of the clock cycle can flexibly change the time of the soft start of the power supply. The embodiment of the invention further provides a system for power soft start, as shown in FIG. 12, including a built-in current source I 121, a duty cycle circuit 122, a switch M1 123, a built-in capacitor C 124, and an analog multiplexer ANALOG MUX. 125. Error amplifier ERROR AMP 126 and pulse modulation control circuit 127.

The current source I 121 generates a charging current, which is output to the capacitor C 124 through the switch M123. The closing of the switch M1 123 is controlled by the duty cycle circuit 122, and thus the charging time of the capacitor C 124 is controlled. When the current charges the capacitor C 124, the capacitor C 124 integrates the charge and the voltage rises stepwise; the analog multiplexer ANALOG MUX 125 compares the voltage of the capacitor C 124 with the reference source voltage, The smaller of the two is output to the error amplifier ERROR AMP 126; the voltage is output from the ERROR AMP 126 to the pulse modulation control circuit 127, and the output voltage V _{OUT is} slowly increased by the negative feedback of the entire loop to achieve soft output power. Start function. Capacity, cost savings; extended soft-start time by soft-start circuit, can achieve longer soft-start function under the same chip area; by adjusting the size of capacitor C, the size of current source I, the size of duty cycle and The length of the clock cycle can flexibly change the time of the soft start of the power supply. Through the description of the above embodiments, those skilled in the art can clearly understand that the present invention can be implemented by hardware or by means of software plus a necessary general hardware platform. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which may be stored in a non-volatile storage medium (which may be a CD-ROM, a USB flash drive, a mobile hard disk, etc.), including several The instructions are for causing a computer device (which may be a personal computer, server, or network device, etc.) to perform the methods described in various embodiments of the present invention.

In summary, the above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and scope of the invention are intended to be included within the scope of the invention.

Claims

Rights request

A method for soft start of a power supply, characterized in that:

Detecting a clock signal;

Generating a duty cycle signal based on the detected clock signal;

2. The method according to claim 1, wherein the outputting the duty cycle signal to the switch, the step of controlling the closing of the switch comprises:

The duty cycle signal controls a switch between the charging current and the capacitor to be periodically closed;

When the switch is closed, a charging current charges the capacitor through the switch.

3. The method of claim 2, wherein the duty cycle signal control switch periodic closure comprises:

When the duty cycle signal is a pulse signal, the switch is turned on; otherwise, the switch is closed.

The method according to any one of claims 1 to 3, wherein the step of controlling the charging of the capacitor to achieve soft start of the power source comprises:

The analog multiplexer determines the magnitude of the capacitor voltage and the reference source voltage, and receives the smaller of the capacitor voltage and the reference source voltage;

The analog multiplexer inputs the received voltage to an error amplifier to generate an output voltage.

The analog multiplexer determines the magnitude of the capacitor lower plate voltage and the reference source voltage, and receives the smaller voltage of the capacitor lower plate voltage and the reference source voltage;

The analog multiplexer inputs the received voltage to an error amplifier to obtain an output voltage.

The method according to any one of claims 1 to 3, wherein the switch is a P channel metal oxide semiconductor transistor or an N channel metal oxide semiconductor transistor;

The capacitor is a normal capacitor or a MOS capacitor.

7. A device for soft start of a power supply, comprising:

a detecting unit, configured to detect a clock signal;

a duty ratio generating unit, configured to generate a duty according to the clock signal detected by the detecting unit Ratio signal

The soft start unit is configured to output the duty cycle signal to the switch, control the closing of the switch, and thereby control the charging of the capacitor to implement soft start of the power source.

8. The apparatus according to claim 7, wherein the soft start unit comprises: a switch control subunit for outputting the duty cycle signal to a switch to control closure of the switch; and a capacitor charging subunit When the switch is closed, the charging current charges the capacitor through the switch; the voltage determining subunit is configured to determine the magnitude of the capacitor voltage and the reference source voltage, and receive the capacitor voltage and the reference source voltage. Small voltage

The voltage output subunit is configured to determine the voltage received by the subunit according to the voltage, and generate an output voltage.

9. A system for power soft start, characterized in that:

10. The system of claim 9 further comprising a current source, said current source generating a charging current output to said capacitor through said switch.

11. A system for power soft start, characterized in that:

Duty cycle circuit, switch, capacitor, analog multiplexer, voltage output subunit;

An analog multiplexer for determining a voltage of the capacitor voltage or the lower plate voltage of the capacitor and a reference source voltage, receiving a smaller voltage thereof, and outputting the smaller voltage to the error amplifier;

The system of claim 11, wherein the voltage output subunit comprises: an error amplifier, a pulse modulation control circuit, and a negative feedback loop;

An error amplifier receiving a voltage of the analog multiplexer input and a feedback voltage of the negative feedback loop, and inputting the generated voltage into the pulse modulation control circuit;

The pulse modulation control circuit and the negative feedback loop are used to generate an output voltage and a feedback voltage according to the voltage input from the error amplifier.

13. The system of claim 11 wherein the system further comprises: a current source coupled to the switch for generating the charging current.