WO2020057135A1

WO2020057135A1 - Flashlight control circuit and mobile terminal

Info

Publication number: WO2020057135A1
Application number: PCT/CN2019/085295
Authority: WO
Inventors: 徐家林
Original assignee: 深圳市泰衡诺科技有限公司
Priority date: 2018-09-17
Filing date: 2019-04-30
Publication date: 2020-03-26
Also published as: CN109275246B; CN109275246A

Abstract

The present invention relates to the technical field of control and specifically relates to a flashlight control circuit and a mobile terminal. The flashlight control circuit comprises a flashlight and a current amplifying structure. The current amplifying structure comprises a first triode and a second triode. A current output end of the first triode is connected to a current input end of the second triode. A current amplified by the current amplifying structure flows into the flashlight. The present invention solves the problem of severe triode heating and reduces the amount of heat generated in the flashlight control circuit.

Description

Flash control circuit and mobile terminal

Technical field

The present invention relates to the field of control technology, and in particular, to a flash control circuit and a mobile terminal.

Background technique

With the continuous development of science and technology and the continuous improvement of people's living standards, electronic user terminal devices such as mobile phones, tablet computers, notebook computers, and cameras have become increasingly popular in people's lives. At the same time, with the advancement of digital image processing technology and charge coupled device (CCD), digital photography technology has reached an unprecedented level. In this context, existing user terminal devices have listed camera functions as basic equipment. On a user terminal having a photographing function, in addition to a lens necessary for photographing, a flash having a supplementary light effect is also required.

At present, there are mainly two types of control circuits for the flash in mobile terminals: one is controlled by an integrated chip (IC); the other is a discrete bipolar junction transistor (BJT) or MOS tube Take control. However, when an integrated chip is used for control, the current flowing through the flash is small and the brightness of the flash is weak. By adopting the control method of discrete devices, the current flowing through the flash can be made larger, and the brightness of the flash can be made higher.

FIG. 1 is a schematic diagram of a circuit structure for controlling a flash lamp by using discrete devices in the prior art. As shown in FIG. 1, the voltage applied to the base of the BJT11 is adjusted by the control chip 12 so that the BJT11 is turned on and the flash 10 is blinked. Although the control method in Figure 1 is simple, during the flashing of the flash, the BJT11 also plays a role of current amplification, that is, when the current that needs to flow through the flash 10 is large (such as 2A), it flows through the base of BJT11 The current will also be very large (for example, when the amplification gain of the BJT11 is 100, the current flowing through the base will be as high as 20 mA). Excessive current will cause BJT11 to heat up very seriously, and even cause BJT11 to burn out.

Therefore, how to reduce the heating problem of the flash control circuit, and at the same time ensure that a large current can flow into the flash, and improve the brightness of the flash is a technical problem that needs to be solved.

Summary of the Invention

The invention provides a flash control circuit and a mobile terminal, which are used to solve the problem that the flash control circuit has serious heat generation in the prior art.

In order to solve the above problem, the present invention provides a flash lamp control circuit including a flash lamp and a current amplification structure; the current amplification structure includes a first transistor and a second transistor, and a current output of the first transistor The terminal is connected to the current input terminal of the second transistor; the current amplified by the current amplification structure flows into the flash lamp.

Preferably, the current amplification structure can amplify the current input to the flash lamp by at least 1000 times.

Preferably, the first transistor and the second transistor are both NPN type transistors; the emitter of the first transistor is connected to the base of the second transistor; and the flash is simultaneously The collector of the first triode is connected to the collector of the second triode.

Preferably, the first transistor and the second transistor are both PNP type transistors; the base of the first transistor is connected to the emitter of the second transistor; and the flash is simultaneously The collector of the first triode is connected to the collector of the second triode.

Preferably, the first triode and the second triode have the same electrical performance.

Preferably, it further includes a first resistor, a second resistor, and a third resistor; one end of the first resistor is connected to the power output terminal, and the other end of the first resistor is simultaneously connected to the base of the first transistor and the second resistor. One end; the other end of the second resistor is grounded; one end of the third resistor is connected to the emitter of the second transistor, and the other end is grounded.

Preferably, the voltages applied to the first resistor, the second resistor, the third resistor, and the flash lamp are all 2.4V-2.8V.

Preferably, the resistance of the first resistor is equal to the resistance of the third resistor, and the resistance of the second resistor is 8-10 times the resistance of the first resistor.

Preferably, the resistance of the first resistor and the third resistor are both 1KΩ, and the resistance of the second resistor is 10KΩ.

In order to solve the above problem, the present invention further provides a mobile terminal including the flash control circuit according to any one of the above.

The strobe control circuit and mobile terminal provided by the present invention adopt a structure in which two triodes are connected in series as a current amplification structure to amplify the current flowing into the strobe, and the current amplification factor of the current amplification structure is the current amplification factor of the two triodes. The product can reduce the current flowing through the base of each transistor while ensuring that a large current flows in the flash and maintaining high brightness, which solves the serious problem of triode heating and reduces the heat generation in the flash control circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a circuit structure for controlling a flash lamp by using a discrete device in the prior art;

FIG. 2 is a schematic structural diagram of a flash control circuit in a specific embodiment of the present invention.

detailed description

The specific embodiments of the flash control circuit and the mobile terminal provided by the present invention will be described in detail below with reference to the drawings.

This embodiment provides a flash control circuit, and FIG. 2 is a schematic structural diagram of a flash control circuit in a specific embodiment of the present invention. As shown in FIG. 2, the strobe control circuit provided in this embodiment includes a strobe and a current amplification structure; the current amplification structure includes a first transistor T1 and a second transistor T2, and the first transistor The current output terminal of T1 is connected to the current input terminal of the second transistor T2; the current amplified by the current amplification structure flows into the flash lamp.

The position of the second ammeter A2 in FIG. 2 is the installation position of the flash. In this specific embodiment, the second ammeter A2 is used to detect the current flowing through the flash. In a practical application process, the second ammeter A2 in FIG. 2 is replaced with the flashlight to form the flashlight control circuit. The current amplification structure is used to amplify the current flowing into the flash lamp. In this specific embodiment, the current amplification structure is configured by using a first transistor T1 and a second transistor T2 connected in series, and then the total current amplification factor of the current amplification structure is the current of the first transistor T1. The product of the amplification factor and the current amplification factor of the second transistor T2. In this way, while ensuring a large current flowing in the flash and maintaining high brightness, the current flowing through the base of each triode is reduced, the problem of serious heat generation of the triode is solved, and the heat generation in the flash control circuit is reduced.

The first ammeter A1 in FIG. 2 is used to detect the current flowing through the base of the first transistor T1 to test the effect of the flash control circuit provided by this embodiment. In an actual application process, there is no need to set the first ammeter A1 in the flash control circuit. For example, if the current amplification factors of the first transistor T1 and the second transistor T2 are both 100 times, the total current amplification factor of the current amplification structure is 10,000 times; When the second ammeter A2 (that is, the current flowing into the flashlight) is 2A, the current detected by the first ammeter A1 (that is, the current flowing into the base of the first transistor T1) is only 200 μA. Compared with the control circuit in the prior art shown in FIG. 1 when the flash current is 2A and the current flowing through the BJT is 20 mA, this specific implementation greatly reduces the base current.

In this specific implementation manner, the current amplification factor of the first triode T1 and the second triode T2 may be the same or different. Those skilled in the art may select the first triode T1 according to actual needs. And the second transistor T2 to construct the current amplification structure with a suitable current amplification factor. Preferably, the current amplification structure can amplify the current input to the flash lamp by at least 1000 times. More preferably, the current amplification structure can amplify the current input to the flash lamp by at least 10,000 times.

Preferably, as shown in FIG. 2, the first triode T1 and the second triode T2 are both NPN type triodes; the emitter of the first triode T1 is connected to the second triode The base of the tube T2; the flash is connected to the collector of the first transistor T1 and the collector of the second transistor T2 at the same time. The electrical performance of the first transistor T1 and the second transistor T2 may be the same or different. In order to simplify the structure of the flash lamp control circuit and facilitate accurate control of the current flowing through the flash lamp, it is more preferable, and preferably, that the first transistor T1 and the second transistor T2 have the same electrical performance. The same electrical performance means that the first triode T1 and the second triode T2 have at least the same current amplification factor.

In other specific embodiments, the first transistor and the second transistor are both PNP type transistors; the base of the first transistor is connected to the emitter of the second transistor; The flash is connected to the collector of the first triode and the collector of the second triode simultaneously.

Preferably, the flash control circuit further includes a first resistor R1, a second resistor R2, and a third resistor R3; one end of the first resistor R1 is connected to the power output terminal, and the other end is simultaneously connected to the first transistor T1. The base of the second resistor R2 is connected to one end of the second resistor R2; the other end of the second resistor R2 is grounded; one end of the third resistor R3 is connected to the emitter of the second transistor T2, and the other end is grounded. More preferably, the voltages applied to the first resistor R1, the second resistor R2, the third resistor R3, and the flash lamp are all 2.4V-2.8V.

Specifically, as shown in FIG. 2, the first triode T1 and the second triode T2 are NPN type triodes having the same electrical performance. After the flash control circuit is turned on, the voltage drop between the base and the emitter of the first transistor T1 is 1.2V-1.4V, and the base and the emitter of the second transistor T2 are The voltage drop between them is also 1.2V-1.4V. In order to further simplify the structure of the flash control circuit, and to ensure that the transmitting junction of the first transistor T1 is forward-biased and the collector junction is reverse-biased, the current amplification structure can effectively amplify the current input to the flash. , A bias circuit for controlling the current amplifying structure needs to be provided to realize the bias voltage division of the first transistor T1 and the second transistor T2. In this specific embodiment, when the voltage is positive, the bias voltage of the current amplification structure is the voltage drop between the base and the emitter of the first transistor T1 and the voltage drop between the second transistor T2 and the second transistor T2. The sum of the voltage drop between the base and the emitter is 2.4V-2.8V. Therefore, the voltages applied to the first resistor R1, the second resistor R2, the third resistor R3, and the flash lamp are both 2.4V-2.8V to further precisely control the current amplification structure. Current amplification effect.

Similarly, the first transistor T1 and the second transistor T2 are PNP type transistors with the same electrical performance. When the voltage is negative, the bias voltage of the current amplification structure is the first transistor. The sum of the voltage drop between the base and the emitter of T1 and the voltage drop between the base and the emitter of the second transistor T2, that is, 2.4V-2.8V. At this time, the voltage applied to the first resistor R1, the second resistor R2, the third resistor R3, and the flash lamp should also be 2.4V-2.8V to further precisely control the current. The current amplification effect of the amplification structure.

The first resistor R1, the second resistor R2, and the third resistor R3 may all be fixed-value resistors or variable resistors, and those skilled in the art may choose according to actual needs. In order to further simplify the structure of the flash control circuit, preferably, the resistance of the first resistor R1 is equal to the resistance of the third resistor R3, and the resistance of the second resistor R2 is the first resistor 8-10 times the resistance of R1. More preferably, the resistance of the first resistor R1 and the third resistor R3 are both 1KΩ, and the resistance of the second resistor R2 is 10KΩ.

Not only that, this embodiment also provides a mobile terminal including the flash control circuit according to any one of the above. The mobile terminal may be, but is not limited to, a mobile phone, a notebook computer, and a tablet computer.

The strobe control circuit and mobile terminal provided by this specific embodiment use the structure of two triodes connected in series as a current amplification structure to amplify the current flowing into the strobe, and the current amplification factor of the current amplification structure is two triode current amplifications. The product of multiples, so as to ensure a large current flowing in the flash and maintain high brightness, reduce the current flowing through the base of each transistor, solve the serious problem of triode heating, and reduce the amount of heat in the flash control circuit .

The above is only a preferred embodiment of the present invention. It should be noted that, for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and retouches can be made. These improvements and retouches should also be viewed as It is the protection scope of the present invention.

Claims

A strobe control circuit is characterized in that it includes a strobe and a current amplifying structure. The current amplifying structure includes a first triode and a second triode, and a current output terminal of the first triode and the first triode. The current input terminals of the two transistors are connected; the current amplified by the current amplification structure flows into the flash lamp.
The flash control circuit according to claim 1, wherein the current amplification structure is capable of amplifying a current input to the flash by at least 1000 times.
The flash control circuit according to claim 1, wherein the first transistor and the second transistor are both NPN type transistors; an emitter of the first transistor is connected to the first transistor. The base of two triodes; the flash is connected to the collector of the first triode and the collector of the second triode simultaneously.
The flash control circuit according to claim 1, wherein the first transistor and the second transistor are both PNP type transistors; a base of the first transistor is connected to the first transistor. The emitter of the two triodes; the flash lamp is connected to the collector of the first triode and the collector of the second triode simultaneously.
The flash control circuit according to claim 3, wherein the first triode and the second triode have the same electrical performance.
The flash control circuit according to claim 5, further comprising a first resistor, a second resistor, and a third resistor; one end of the first resistor is connected to the power output terminal, and the other end is connected to the first three resistors simultaneously. The base of the transistor is connected to one end of the second resistor; the other end of the second resistor is grounded; one end of the third resistor is connected to the emitter of the second transistor, and the other end is grounded.
The flash control circuit according to claim 6, wherein the voltages applied to the first resistor, the second resistor, the third resistor, and the flash are all 2.4V-2.8V.
The flash control circuit according to claim 6, wherein a resistance value of the first resistor is equal to a resistance value of the third resistor, and a resistance value of the second resistor is the resistance value of the first resistor 8-10 times.
The flash control circuit according to claim 8, wherein the resistance of the first resistor and the third resistor are both 1KΩ, and the resistance of the second resistor is 10KΩ.
A mobile terminal, comprising the flash control circuit according to any one of claims 1-9.