CN113972639A

CN113972639A - Pulse width modulation-based overcurrent protection circuit and operation method thereof

Info

Publication number: CN113972639A
Application number: CN202010715324.9A
Authority: CN
Inventors: 朱立程
Original assignee: Realtek Semiconductor Corp
Current assignee: Realtek Semiconductor Corp
Priority date: 2020-07-23
Filing date: 2020-07-23
Publication date: 2022-01-25

Abstract

An overcurrent protection circuit based on pulse width modulation and an operation method thereof are provided, the overcurrent protection circuit comprises a pulse width modulation circuit, a charge pump and a load detection circuit, wherein the charge pump is connected with a power switch circuit, the charge pump outputs voltage to the power switch circuit according to a frequency voltage signal, and the load detection circuit can detect overcurrent passing through the power switch circuit according to the load of the power switch circuit at the output end. Therefore, when the load detection circuit detects the overcurrent, the pulse width modulation circuit controls the duty cycle width of the charge pump to restrain the voltage output by the charge pump, so as to correct the output voltage of the power switch circuit and avoid or reduce the overcurrent.

Description

Pulse width modulation-based overcurrent protection circuit and operation method thereof

Technical Field

The present invention discloses an overcurrent protection scheme, and more particularly, to a protection circuit for suppressing overcurrent in a power control circuit by using a pulse width modulation technique and an operating method thereof.

Background

An overcurrent protection circuit is commonly designed in a power supply circuit of an electronic device, and is used for clamping current at a certain current, so that the problem that the current is too large in the circuit can be suppressed, the damage caused by the fact that large current passes through components in the circuit is avoided, and the overcurrent protection circuit has the function of protecting the circuit.

Referring to fig. 1, a schematic diagram of a power switch circuit disposed in a circuit system is shown, taking a control circuit of universal serial bus Type-C (USB Type-C) as an example, in which the power switch circuit 10 is responsible for controlling a current (ICC) between a power terminal (VCONN) of a source terminal (source) and a Common Collector terminal (CC) of a SINK terminal (SINK) that consumes power. This is a Power MOS (Power MOS) architecture, in which a large current flows from the Power supply (VCONN) to the common Collector Circuit (CC) due to the load of the SINK (SINK) that exceeds the expected load, and an overcurrent protection device is used to clamp the circuit passing through the usb type C to a certain value.

In the prior art, the current protection device adopts a Burst Mode (Burst Mode) mechanism, when the current (ICC) between the power supply terminal (VCONN) and the common collector terminal (CC) exceeds the rated range, the overcurrent protection device sends an overcurrent protection Voltage (VOCP) from 0 to 1, so as to adjust the frequency signal (CLK) in the circuit to suppress the output Voltage (VCP) of the Charge Pump (Charge Pump)12, so that the voltage at the GATE (GATE) of the transistor in the power switch circuit 10 is reduced, and the current (ICC) is reduced.

Fig. 2A shows the variation of the output Voltage (VCS) after overcurrent protection is performed in the burst mode, fig. 2B shows the corresponding clock signal in the burst mode, and fig. 2C shows the timing chart of the generation of the overcurrent protection Voltage (VOCP).

Typically, the charge pump 12 in the circuit generates a frequency voltage signal (VDUTY) according to the fixed time period to provide an output Voltage (VCP), such as 10V, via a gate terminal of a power switch (power switch). When an overcurrent is detected, the punch die is activated to perform overcurrent protection, and an overcurrent protection Voltage (VOCP) is generated, as shown in fig. 2C, and then the frequency voltage signal (VDUTY) is adjusted by the current protection Voltage (VOCP), as shown in fig. 2B, the voltage supplied to the gate terminal of the power switch by the charge pump 12 can be reduced in this way, and the corrected output Voltage (VCS) of the power switch can be shown with reference to fig. 2A, where VREF is the reference voltage provided by the circuit, thereby showing that the correction drop is Δ V1.

However, the conventional drawback of performing the over-current protection in the burst mode is that the voltage ripple of the output Voltage (VCP) of the charge pump 12 is too large due to the too long duration of the frequency voltage signal (VDUTY), and the output Voltage (VCS) supplies too much energy each time in the burst mode, and the too long suppression time affects the current ripple of the power switch.

Disclosure of Invention

In view of the fact that the conventional overcurrent protection measures cannot solve all the problems, for example, the problem of ripple at the voltage end due to excessive energy transmitted each time in a burst mode for suppressing overcurrent is solved, the present invention provides an overcurrent protection circuit based on pulse width modulation and an operating method thereof, which provide a method for adjusting the pulse width (pulse width) of the duty cycle (duty cycle) of a current pump (charge pump) in a circuit to modulate the current passing through a power switch (power switch), so as to effectively suppress overcurrent and avoid output voltage ripple.

According to the embodiments of the present disclosure, the method for operating the pwm-based overcurrent protection circuit mainly detects the overcurrent through the power switch circuit according to the load at the output terminal of the power switch circuit, where the load is derived from the output voltage of the power switch circuit. When the overcurrent is detected, the pulse width modulation circuit controls the work period width of a charge pump which provides the voltage of the power switch circuit, and the work period width is adjusted to inhibit the voltage output to the power switch circuit by the charge pump, so that the output voltage output by the power switch circuit is corrected to inhibit the overcurrent.

Furthermore, the power switch circuit is connected to a load detection circuit, and the load detection circuit determines whether an overcurrent exists according to a load of the power switch circuit at an output end.

Furthermore, when the overcurrent is detected, the load detection circuit generates the overcurrent protection voltage, so that the pulse width modulation circuit can adjust the frequency voltage signal output to the charge pump according to the overcurrent protection voltage, and the width of the working period of the output voltage of the charge pump is controlled.

Preferably, the pulse width modulation circuit can dynamically adjust the frequency voltage signal according to the overcurrent protection voltage to dynamically control the width of the duty cycle of the output voltage of the charge pump. For example, the pwm circuit can dynamically reduce the duty cycle width to the ratio of the original duty cycle width, such as fifty percent, depending on the situation.

Furthermore, the method can be applied to a universal serial bus C type, and the power switch circuit is a power switching circuit in a control circuit.

The method for executing the overcurrent protection circuit based on the pulse width modulation utilizes the pulse width modulation circuit, can judge overcurrent according to the load of the power switch circuit, and can control the duty cycle width of the charge pump when the overcurrent is detected so as to inhibit the voltage output to the power switch circuit by the charge pump, thereby correcting the output voltage output by the power switch circuit. Thus, the overcurrent passing through the power switch circuit can be effectively inhibited.

For a better understanding of the nature and technical aspects of the present invention, reference should be made to the following detailed description and accompanying drawings which are provided to illustrate and not limit the invention.

Drawings

FIG. 1 shows a schematic diagram of a power switching circuit;

FIG. 2A is a graph showing the variation of output voltage for performing over-current protection using a punch die;

FIG. 2B shows the frequency signal in the burst die mode;

FIG. 2C is a timing diagram illustrating the generation of the over-current protection voltage;

FIG. 3 is a diagram of an embodiment of a PWM-based over-current protection circuit;

FIG. 4 is a flowchart of an embodiment of a method for operating a PWM-based over-current protection circuit;

FIG. 5A is a graph showing the variation of output voltage for performing over-current protection by PWM;

FIG. 5B shows a frequency signal under the PWM method;

FIG. 5C is a timing diagram illustrating the generation of the over-current protection voltage;

FIG. 6 is a diagram of one embodiment of a PWM-based overcurrent protection circuit;

fig. 7 is a diagram of another embodiment of a pwm-based overcurrent protection circuit.

Description of the symbols:

in order to make the above and other objects, features, advantages and embodiments of the present invention more comprehensible, the following description is given:

10: power switch circuit

VCONN: power supply terminal

CC: common collector circuit

ICC: electric current

CLK: frequency signal

12: charge pump

VCP: output voltage

VOCP, VOCP': over-current protection voltage

Δ V1, Δ V2: correcting drop height

VCS, VCS': output voltage

VDUTY, VDUTY': frequency voltage signal

VREF: reference voltage

VPL: pulse signal

30: pulse width modulation circuit

31: charge pump

33: power switch circuit

35: load detection circuit

65: power switch circuit

62: charge pump

63: voltage drop control circuit

67: load detection circuit

60: pulse width modulation circuit

70: pulse width modulation circuit

701: flip-flop

703: flip-flop

Steps S401 to S407: pulse width modulation based operation process of over-current protection circuit

Detailed Description

All words used herein have their ordinary meaning. The above words are defined in commonly used dictionaries and the use of any word discussed herein in the context of this specification is by way of example only and should not be taken as limiting the scope and meaning of the present application. As such, the present application is not limited to the various embodiments shown in this specification.

The following description is given of embodiments of the present invention by way of specific examples, and it will be apparent to those skilled in the art from this disclosure that the advantages and effects of the present invention can be obtained. The invention is capable of other and different embodiments and its several details are capable of modifications and various changes in detail without departing from the spirit and scope of the present invention. It should be noted that the drawings of the present invention are merely schematic illustrations and are not drawn to actual dimensions. The following embodiments will further explain the related art of the present invention in detail, but the disclosure is not intended to limit the scope of the present invention.

It will be understood that, although the terms "first," "second," "third," etc. may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are used primarily to distinguish one element from another element or from one signal to another signal. In addition, the term "or" as used herein should be taken to include any one or combination of more of the associated listed items as the case may be.

The present invention relates to an overcurrent protection scheme, and more particularly to a protection circuit for suppressing an overcurrent in a power control circuit using a pulse width modulation technique, and a method for operating the overcurrent protection circuit based on the pulse width modulation.

The pulse width modulation-based overcurrent protection circuit can be applied to power management circuits in various electronic devices, such as a connector circuit with a specific industrial specification, for example, but not limited to, a Universal Serial Bus (USB) Type-C in various specifications, the proposed pulse width modulation-based overcurrent protection circuit scheme is an improved universal serial bus Type-C internal power Switch (VCONN Switch) overcurrent protection circuit, which is a power switching circuit in a universal serial bus Type-C control circuit, such as a switching circuit implemented by a Metal Oxide Semiconductor (MOS).

For example, in a Universal Serial Bus (USB) C-type connector circuit, referring to fig. 1, unlike the conventional Burst Mode control method, in the disclosed scheme, a pulse modulation control method, such as a Pulse Width Modulation (PWM) method, is used instead to modulate the duty cycle width of a Charge Pump (Charge Pump) according to the load size, so as to modulate the amount of power provided in each duty cycle, adjust the output voltage of the power switch circuit, and thus achieve the purpose of low voltage/current ripple and output more stable voltage through pulse modulation.

The main concept of the pwm-based overcurrent protection circuit is shown in fig. 3.

The figure shows that a pulse width modulation circuit 30 is arranged in a protection circuit of a power switch circuit 33, the pulse width modulation circuit 30 is connected with a charge pump 31 and a load detection circuit 35, the charge pump 31 supplies energy required by the power switch circuit 33, the output end of the power switch circuit 33 is provided with the load detection circuit 35, and the load detection circuit 35 can judge whether an overcurrent phenomenon occurs or not according to the load of the power switch circuit 33 at the output end. The operation method of the pwm-based overcurrent protection circuit can also refer to the process shown in fig. 4.

In the electronic apparatus (such as a connector) adopting the above-mentioned scheme, the power switch circuit 33 is used for controlling power supply, and the load detection circuit 35 at one end of the power switch circuit 33 detects the output Voltage (VCS) of the power switch circuit 33 (step S401), and determines whether there is an overcurrent according to the load at the output end thereof (step S403).

In the case where there is no overcurrent (no), step S401 is continuously executed; on the contrary, when the load determines that the overcurrent exists, step S405 is executed to adjust the duty cycle of the charge pump 31 of the power switch circuit 33 through the pwm circuit 30, that is, to control the output voltage of the charge pump 31 (step S407). In this way, it is possible to adjust the output voltage of the power switching circuit 33 while suppressing (avoiding or reducing) the generated overcurrent.

The main concept of the over-current protection can refer to the output voltage variation graph of fig. 5A, the frequency signal graph of fig. 5B and the timing chart of fig. 5C, which are used to perform the over-current protection by the pwm method.

Compared with the conventional overcurrent protection method using burst mode as shown in fig. 2A to fig. 2C, the overcurrent protection circuit proposed in this specification mainly uses pulse width modulation (pwm) technology, and when an overcurrent occurs, the load detection circuit that detects the overcurrent can generate the overcurrent protection voltage (VOCP ') as shown in fig. 5C, and provide the overcurrent protection voltage (VOCP ') to the pwm circuit, so that the pwm circuit adjusts the frequency voltage signal (VDUTY ', fig. 5B) according to the overcurrent protection voltage to control the duty cycle width of the output voltage of the charge pump.

That is, by modulating the frequency voltage signal (VDUTY ') provided to the charge pump of the power switch circuit, i.e., modulating the duty cycle of the charge pump at a ratio of each operating frequency, the charge pump can output a periodic voltage to the power switch circuit at each operating cycle, so as to avoid an excessively long period to reduce the voltage output by the charge pump to the power switch circuit, and the power switch circuit can output the voltage (VCS', VREF is the reference voltage provided by the circuit) as shown in fig. 5A, which shows the effect of suppressing the over-current, and the correction drop is Δ V2.

For example, if the current through the power switch circuit is controlled within the rated current range, the pulse width modulation circuit outputs a frequency voltage signal (VDUTY') that is 50% of the original frequency voltage signal. In this way, the efficiency of the charge pump can be maximized.

Fig. 6 shows a diagram of an embodiment of an overcurrent protection circuit based on pwm.

A power switch circuit 65 is shown, which is an example of a power switch in a control circuit of the universal serial bus C-type, and which is able to determine whether the current (ICC) between the power supply terminal (VCONN) and the common collector terminal (CC) is excessive by the output Voltage (VCS) of the circuit load.

The power switch circuit 65 is provided with a working voltage (Vcp) by the charge pump 62, the power switch circuit 65 generates an output Voltage (VCS) when operating, the output end of the power switch circuit is provided with a load detection circuit 67, and the load detection circuit 67 can judge an overcurrent according to a load of the power switch circuit 65 at the output end by comparing a reference Voltage (VREF). To suppress the over current, the pwm circuit 60 generates a frequency voltage signal (VDUTY) for modulating the duty cycle width of the charge pump 62 according to the over current protection Voltage (VOCP) generated by the load detection circuit 67.

The charge pump 62 outputs a Voltage (VCP) to the power switch circuit 65 according to the frequency voltage signal (VDUTY). When an over-current occurs, the over-current protection Voltage (VOCP) generated by the load detection circuit 67 triggers the pwm circuit 60 to operate, and the duty cycle of the charge pump 62 can be modulated by generating a frequency voltage signal (VDUTY), and on the other hand, the voltage drop circuit 63 in the circuit can be controlled, and the voltage drop circuit 63 can be controlled by generating a pulse signal (VPL) to control the switch of the voltage drop circuit 63, so as to adjust the voltage (Vcp) output from the charge pump 62 to the power switch circuit 65. The output Voltage (VCS) of the power supply switch circuit 65 is corrected by suppressing the voltage (Vcp) output by the charge pump 62 to the power supply switch circuit 65.

In one embodiment, the pwm circuit 60 dynamically adjusts the frequency-voltage signal (VDUTY) output to the charge pump 62 according to the over-current protection Voltage (VOCP) to dynamically control the duty cycle width of the output voltage of the charge pump 62, i.e., the pwm circuit 60 dynamically reduces the duty cycle width of the charge pump 62 to the ratio of the original duty cycle width according to the over-current protection Voltage (VOCP).

Fig. 7 is a diagram of another embodiment of the pwm-based overcurrent protection circuit, which mainly proposes an embodiment of the pwm circuit 70, and this embodiment shows a flip-flop (FF) 701 having two inputs and two outputs in the pwm circuit 70, which is used to process the two inputs and appropriately generate two outputs according to the two signals, and is used with an adder to generate the pulse signal VPL provided to the voltage drop circuit 63 and the clock voltage signal (VDUTY) provided to the charge pump 62.

In operation, one end of the pwm circuit 70 receives the over-current protection Voltage (VOCP) generated by the load detection circuit 67 according to the over-current detection result, and the flip-flop 703 in the reference circuit operates according to the clock signal CLK to determine the pulse signal (VPL) and the pulse voltage signal (VDUTY) through the operation of the flip-flop 701, so as to suppress the voltage (Vcp) output from the charge pump 62 to the power switch circuit 65 and correct the output Voltage (VCS).

In summary, according to the pwm-based overcurrent protection circuit and the related operation process described in the above embodiments, the main concept of the proposed overcurrent protection is that when an overcurrent is determined according to a load of a power switch, a duty cycle of a charge pump providing power energy can be modulated according to the load, and in addition to using the duty cycle of the pulse width modulation charge pump to reduce an output voltage ripple or a current ripple phenomenon on a switch circuit, a more stable voltage can be output.

The disclosure is only a preferred embodiment of the invention and should not be taken as limiting the scope of the invention, so that the invention is not limited by the disclosure of the invention.

Claims

1. An overcurrent protection circuit based on pulse width modulation, the overcurrent protection circuit comprising:

the pulse width modulation circuit is connected with the charge pump and the load detection circuit, and the charge pump and the load detection circuit are connected with the power switch circuit; wherein the charge pump outputs a voltage to the power switching circuit according to a frequency voltage signal, and the load detection circuit detects an overcurrent through the power switching circuit according to a load of the power switching circuit at an output terminal;

when the load detection circuit detects the overcurrent, the pulse width modulation circuit controls the duty cycle width of the charge pump to inhibit the voltage output by the charge pump to the power switch circuit, so as to correct the output voltage output by the power switch circuit.

2. The pwm-based overcurrent protection circuit according to claim 1, wherein when the load detection circuit detects the overcurrent, the load detection circuit generates an overcurrent protection voltage, such that the pwm circuit adjusts the frequency-voltage signal according to the overcurrent protection voltage to control a width of the duty cycle during which the charge pump outputs the voltage.

3. The pwm-based overcurrent protection circuit according to claim 2, wherein the pwm circuit dynamically adjusts the frequency-voltage signal according to the overcurrent protection voltage to dynamically control a width of a duty cycle during which the charge pump outputs the voltage.

4. The pwm-based overcurrent protection circuit according to claim 2, wherein the pwm circuit dynamically reduces the duty cycle width of the charge pump to a ratio of an original duty cycle width according to the overcurrent protection voltage.

5. The pwm-based overcurrent protection circuit according to claim 1, wherein the load detection circuit compares a load of the power switch circuit with a reference voltage to detect the overcurrent.

6. The PWM-based overcurrent protection circuit as claimed in any one of claims 1 to 5, wherein the power switch circuit is a power switching circuit in a control circuit of a USB type C.

7. An operating method of an overcurrent protection circuit based on Pulse Width Modulation (PWM), the operating method comprising:

detecting an overcurrent through a power switching circuit according to a load of the power switching circuit at an output terminal; and

when the overcurrent is detected, the duty cycle width of the charge pump is controlled by the pulse width modulation circuit so as to inhibit the voltage output by the charge pump to the power switch circuit, and therefore the output voltage output by the power switch circuit is corrected so as to inhibit the overcurrent.

8. The method as claimed in claim 7, wherein the power switch circuit is connected to a load detection circuit, and the load detection circuit determines whether the over-current exists according to a load of the power switch circuit at the output terminal.

9. The method as claimed in claim 8, wherein the pwm circuit adjusts the frequency voltage signal outputted to the charge pump according to the overcurrent protection voltage generated by the load detection circuit, so as to control the duty cycle width of the output voltage of the charge pump.

10. The method as claimed in claim 9, wherein the pwm circuit dynamically adjusts the clock voltage signal according to the overcurrent protection voltage to dynamically control a duty cycle width of the charge pump outputting the voltage.