CN102420888B - Constant-voltage flashlight drive circuit of mobile phone and method for driving flashlight by constant-voltage flashlight drive circuit - Google Patents
Constant-voltage flashlight drive circuit of mobile phone and method for driving flashlight by constant-voltage flashlight drive circuit Download PDFInfo
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- CN102420888B CN102420888B CN201110389968.4A CN201110389968A CN102420888B CN 102420888 B CN102420888 B CN 102420888B CN 201110389968 A CN201110389968 A CN 201110389968A CN 102420888 B CN102420888 B CN 102420888B
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Abstract
The invention discloses a constant-voltage flashlight drive circuit of a mobile phone and a method for driving a flashlight by the constant-voltage flashlight drive circuit. The constant-voltage flashlight drive circuit comprises a drive chip, a current-limiting resistor, a first capacitor, the flashlight and a microprocessor, wherein an output port of the drive chip is connected with a sampling port of the microprocessor through the current-limiting resistor, an anode of the flashlight is respectively connected with the sampling port of the microprocessor and the current-limiting resistor, a cathode of the flashlight is grounded, a control port of the drive chip is connected with a control port of the microprocessor, an input port of the drive chip is connected with a power supply, the first capacitor is serially connected between a C<+> port and a C<-> port of the drive chip; and the microprocessor is used for sampling the voltage of the flashlight and outputting a high level or outputting a PWM (Pulse Width Modulation) signal with corresponding frequency according to the sampling voltage, and controlling the current of the flashlight to be less than or equal to the maximum conducting current of the flashlight. The invention solves the problem of inconsistency of the currents of flashlights of different mobile phones due to difference of forward conducting voltages of the flashlights of the traditional flashlight drive circuit.
Description
Technical field
The present invention relates to the control of the drive current to constant pressure type photoflash lamp, particularly a kind of method of constant pressure type flashlight driving circuit of mobile phone and driving photoflash lamp thereof.
Background technology
The application of photoflash lamp in mobile phone is more and more extensive, and it can be used as a light filling equipment and ensures that user's shooting picture dim in the situation that is clear bright, also can be used as lighting apparatus and use.Flash lamp circuit in mobile phone generally comprises constant current mode drive circuit and constant pressure type drive circuit.Due to the advantage such as the price of constant pressure type drive circuit is low, circuit is simple, be widely used in cheaply in mobile phone.
Refer to Fig. 1, it is the drive circuit figure of prior art constant pressure type photoflash lamp, can learn from this circuit diagram, and in the time of the work of photoflash lamp, photoflash lamp electric current I
lEDfor:
.
In actual use, because the forward direction conducting voltage of the photoflash lamp of different batches is different, taking the SP-T352718W photoflash lamp of HARVATEK company as example, in the time that photoflash lamp is worked, its forward direction conducting voltage V
lEDfor 2.9-3.9V, On current I
lEDmaximum current be 90mA.
For ensureing On current I
lEDmaximum current be no more than 90mA, generally can only get at present V
lEDminimum value 2.9V select current-limiting resistance R11, according to above-mentioned formula, distortion can obtain:
Because 23.3ohm is non-standard resistance, thus current-limiting resistance R11=24ohm selected, the more above-mentioned formula of substitution can obtain: in the time that the forward direction conducting voltage VLED of photoflash lamp is 2.9V, I
lED_MAX=87.5mA, in the time that the forward direction conducting voltage VLED of photoflash lamp is 3.9V, I
lED_MIN=45.8mA.Due to the difference of the forward direction conducting voltage of photoflash lamp, the poorest in the situation that, can cause the photoflash lamp difference between current of different mobile phones to be: I
lED_MAX-I
lED_MIN=41.7mA.
Therefore, existing constant pressure type flashlight driving circuit, due to the forward direction conducting voltage V of photoflash lamp
lEDdifference can cause the photoflash lamp electric current of different mobile phones inconsistent, taking above-mentioned constant pressure type flashing light light drive circuit as example, the photoflash lamp difference between current of different mobile phones is up to 41.7mA.And minimum photoflash lamp electric current I
lED_MINonly have 45.8mA, cannot meet the clear bright demand of shooting picture in dim situation.Visible, existing constant pressure type flashlight driving circuit, due to the forward direction conducting voltage V of photoflash lamp
lEDdifference can cause the photoflash lamp electric current of different mobile phones to have very large difference, do not meet the take pictures requirement of mobile phone in low-light (level) situation.
Summary of the invention
In view of above-mentioned the deficiencies in the prior art part, the object of the present invention is to provide a kind of method of constant pressure type flashlight driving circuit and driving photoflash lamp thereof of mobile phone, can export corresponding control signal according to the difference of forward direction conducting voltage, make the electric current of photoflash lamp be less than or equal to the maximum On current of photoflash lamp.
In order to achieve the above object, the present invention has taked following technical scheme:
A constant pressure type flashlight driving circuit for mobile phone, it comprises driving chip, current-limiting resistance, the first electric capacity, photoflash lamp and microprocessor; The VOUT port of described driving chip is connected with the ADC sample port of microprocessor by described current-limiting resistance, and the positive pole of described photoflash lamp is connected with ADC sample port and the current-limiting resistance of described microprocessor respectively, minus earth; The SHND port of described driving chip is connected with the control port of microprocessor, drives the VIN port of chip to connect power supply, and described the first capacitance series is driving between the C+ port and C-port of chip; Described microprocessor is for the voltage of described photoflash lamp is sampled, and according to the pwm signal of sampled voltage output high level or output corresponding frequencies, the electric current of controlling photoflash lamp is less than or equal to the maximum On current of photoflash lamp.
In the constant pressure type flashlight driving circuit of above-mentioned mobile phone, the maximum On current of described photoflash lamp is 90mA.
In the constant pressure type flashlight driving circuit of above-mentioned mobile phone, described microprocessor is for calculating sample rate current according to described sampled voltage; In the time that sample rate current is greater than the maximum On current of photoflash lamp, drive chip described in the control of described microprocessor output pwm signal, in the time that sample rate current is less than the maximum On current of photoflash lamp, drive chip described in the control of described microprocessor output high level.
In the constant pressure type flashlight driving circuit of above-mentioned mobile phone, also comprise the second electric capacity, one end of described the second electric capacity connects the VOUT port that drives chip, other end ground connection.
In the constant pressure type flashlight driving circuit of above-mentioned mobile phone, also comprise the 3rd electric capacity, one end of described the 3rd electric capacity connects the VIN port that drives chip, other end ground connection.
The method of the constant pressure type flashlight driving circuit of mobile phone and driving photoflash lamp thereof drives a method for photoflash lamp, and it comprises:
Open constant pressure type flash lamp circuit;
By microprocessor, the output voltage that drives chip is sampled;
According to the pwm signal of sampled voltage output high level or output corresponding frequencies, the electric current of controlling photoflash lamp is less than or equal to the maximum On current of photoflash lamp.
In the method for above-mentioned driving photoflash lamp, the maximum On current of described photoflash lamp is 90mA.
In the method for above-mentioned driving photoflash lamp, described microprocessor calculates sample rate current according to described sampled voltage; In the time that sample rate current is greater than the maximum On current of photoflash lamp, drive chip described in the control of described microprocessor output pwm signal, in the time that sample rate current is less than the maximum On current of photoflash lamp, drive chip described in the control of described microprocessor output high level.
In the method for above-mentioned driving photoflash lamp, in the time that sampled voltage is greater than 3.8V, described in the control of described microprocessor output high level, drive chip, in the time that sampled voltage is less than 3.8V, drive chip controls to drive chip described in the pwm signal control of described microprocessor output corresponding frequencies.
Compared to prior art, the method of the constant pressure type flashlight driving circuit of a kind of mobile phone provided by the invention and driving photoflash lamp thereof is sampled to the voltage of photoflash lamp by microprocessor, and according to the pwm signal of sample voltage value output high level or output corresponding frequencies, the electric current of controlling photoflash lamp is being less than or equal to the maximum On current of photoflash lamp, thereby has solved the forward direction conducting voltage V of existing constant pressure type flashlight driving circuit due to photoflash lamp
lEDdifference and cause the photoflash lamp electric current of different mobile phones inconsistent, cannot environment under low-light (level) meet flash of light problem.
Brief description of the drawings
Fig. 1 is the driving circuit principle figure of prior art constant pressure type photoflash lamp.
Fig. 2 is the driving circuit principle figure of constant pressure type photoflash lamp of the present invention.
Fig. 3 is the voltage wave test shape figure that prior art is used high level control photoflash lamp.
Fig. 4 is the voltage tester oscillogram that the present invention adopts the pwm control signal control light lamp of 100Hz.
Fig. 5 is the voltage wave test shape figure of the present invention's pwm control signal control light lamp of adopting 10KHz.
Fig. 6 is the voltage tester oscillogram that the present invention adopts the pwm control signal control light lamp of 100KHz.
Fig. 7 is the graph of a relation of photoflash lamp voltage of the present invention and pwm signal.
Embodiment
The method that the invention provides a kind of constant pressure type flashlight driving circuit and driving photoflash lamp thereof of mobile phone, for making object of the present invention, technical scheme and effect clearer, clear and definite, developing simultaneously referring to accompanying drawing, the present invention is described in more detail for embodiment.Should be appreciated that specific embodiment described herein, only in order to explain the present invention, is not intended to limit the present invention.
Refer to Fig. 2, the constant pressure type flashlight driving circuit of the mobile phone that the embodiment of the present invention provides comprises driving chip U1, current-limiting resistance R1, the first capacitor C 1, photoflash lamp D1 and microprocessor U2.The VOUT port (output port) of described driving chip U1 is connected with the ADC sample port of microprocessor U2 by described current-limiting resistance R1, the positive pole of described photoflash lamp D1 is connected with ADC sample port and the current-limiting resistance R1 of described microprocessor U2 respectively, minus earth.The SHND port (control port) of described driving chip U1 is connected with the control port of microprocessor U2, drives the VIN port (input port) of chip U1 to connect power supply, and described the first capacitor C 1 is serially connected between the C+ port and C-port that drives chip U1; Described microprocessor U2 is for the voltage of described photoflash lamp D1 is sampled, and according to the pwm signal of sampled voltage output high level or output corresponding frequencies, the electric current of controlling photoflash lamp D1 is less than or equal to the maximum On current of photoflash lamp.
The constant pressure type photoflash lamp D1 drive circuit of mobile phone provided by the invention also comprises the second capacitor C 2 and the 3rd capacitor C 3, and one end of described the second capacitor C 2 connects the VOUT port that drives chip U1, other end ground connection; One end of described the 3rd capacitor C 3 connects the VIN port that drives chip U1, other end ground connection.
In the embodiment of the present invention, the maximum On current of described photoflash lamp D1 is 90mA, and described microprocessor U2 is for calculating sample rate current according to described sampled voltage; In the time that sample rate current is greater than the maximum On current of photoflash lamp D1, described in the control of described microprocessor U2 output pwm signal, drive the control port of chip U1, thereby control the electric current of described photoflash lamp, in the time that sample rate current is less than the maximum On current of photoflash lamp D1, described in the control of described microprocessor U2 output high level, drive the control port of chip U1, thereby control the electric current of described photoflash lamp.
In the embodiment of the present invention, described driving chip U1 adopts the integrated chip that model is SGM3110, its power supply that connects 2.7-5.0V by VIN port is to chip power supply, described the first capacitor C 1 is for driving the pumping electric capacity of chip U1, this first capacitor C 1 is serially connected between the C+ port and C-port that drives chip U1, drive the VOUT port of chip U1 generally to export the voltage of 5V, it is connected with the ADC sample port end of microprocessor U2 by resistance, drive the GND port ground connection of chip U1, SHND port is connected with the control end of microprocessor U2, this SHND port is the control pin that drives chip U1, in the time of microprocessor U2 output low level, drive chip U1 to close, now VOUT port output 0V voltage, photoflash lamp D1 does not work, in the time of microprocessor U2 output high level, drive chip U1 work, now VOUT port output 5V voltage, photoflash lamp D1 work, in the time that microprocessor U2 is output as pwm signal, drive chip U1 work, now VOUT port output 5V voltage, photoflash lamp D1 work.In the present embodiment, described the second capacitor C 2 and the 3rd capacitor C 3 are electric capacity of voltage regulation, and described current-limiting resistance R1 is used for controlling the operating current of photoflash lamp D1.
The present invention is still taking the SP-T352718W photoflash lamp D1 of HARVATEK company as Application Example, and the present invention need reselect current-limiting resistance R1.Get equally the forward direction conducting voltage V of photoflash lamp
lEDmaximum 3.9V and the maximum On current I of photoflash lamp D1
lEDfor 90mA selects current-limiting resistance R1, according to
distortion can obtain:
Because 12.2ohm is non-standard resistance, be 13ohm so the present embodiment is got the value of current-limiting resistance R1, thereby can draw: as the forward direction conducting voltage V of photoflash lamp D1
lEDduring for 2.9V, I
lED_MAX=161.5mA; As the forward direction conducting voltage V of photoflash lamp D1
lEDduring for 3.9V, I
lED_MIN=84.6mA.
While being 2.9V due to conducting voltage, the electric current of photoflash lamp D1 is 161.5mA, is greater than the maximum On current 90mA of photoflash lamp D1.The present invention adopts pwm signal to control the SHDN port that drives chip U1, thereby controls the fan-out capability of VOUT port, finally makes the electric current of photoflash lamp D1 maintain within the scope of maximum On current 90mA.
In specific implementation process, the frequency of pwm signal is to driving chip V
oUTalso there is impact in the voltage of output.Can find out from the contrast of Fig. 3, Fig. 4, Fig. 5 and Fig. 6 voltage waveform, work as V
oUTwhen port adopts high level, V
oUTthe fan-out capability maximum of port, while adopting pwm signal, the frequency of pwm signal is higher, V
oUTthe output of port is less, when the frequency of PWM reaches 100KHz when above, V
oUTbe output as 0V.
In the embodiment of the present invention, store the relation of photoflash lamp electric current and pwm signal in described microprocessor, its graph of a relation as shown in Figure 7.Wherein, the relation of photoflash lamp electric current and pwm signal draws by the related data of searching SGM3110 chip, also can between 2.9V-3.9V, get multiple points, and the test of the pwm signal of corresponding frequencies draws.
As the forward direction conducting voltage V of photoflash lamp
lEDduring for 2.9V, photoflash lamp electric current I
lED=161.5mA.Because electric current is now greater than the maximum On current 90mA of photoflash lamp, the pwm signal that the present embodiment proportion is 5000Hz is controlled the output of VOUT port, now can test the electric current I of photoflash lamp
lEDfor 88.2mA, it is less than the maximum On current I of photoflash lamp
lEDfor 90mA, meet the demands.
As the forward direction conducting voltage V of photoflash lamp
lEDduring for 3.9V, photoflash lamp electric current I
lED=84.6mA.Because electric current is now less than the maximum On current 90mA of photoflash lamp, the present invention only need adopt high level to control the SHDN port that drives chip.
The photoflash lamp voltage representing from Fig. 7 and the graph of a relation of pwm signal, known according to the relation in figure, even if the forward direction conducting voltage of the photoflash lamp of different mobile phones is inconsistent, the present invention can be according to the sampled voltage of microprocessor, the frequency of corresponding pwm signal is set by the relation in figure of searching, make the Current Control of photoflash lamp in 85-90mA, in the time that the forward direction conducting voltage of photoflash lamp is 3.8V-3.9V, the control of microprocessor output high level drives the SHDN port of chip, now pwm signal is 0Hz, in the time that the forward direction conducting voltage of photoflash lamp is less than 3.8V, the pwm signal of microprocessor output corresponding frequencies is controlled the SHDN port that drives chip, thereby solve the forward direction conducting voltage V of existing constant pressure type flashlight driving circuit due to photoflash lamp
lEDdifference and cause the inconsistent problem of photoflash lamp electric current of different mobile phones.
Based on above-mentioned drive circuit, the corresponding a kind of method that constant pressure type flashlight driving circuit driving photoflash lamp that adopts above-mentioned mobile phone is provided of the embodiment of the present invention, it comprises:
S11, unlatching constant pressure type flash lamp circuit;
S12, by microprocessor to driving the output voltage of chip to sample;
S13, according to the pwm signal of sampled voltage output high level or output corresponding frequencies, the electric current of controlling photoflash lamp is less than or equal to the maximum On current of photoflash lamp.
In the embodiment of the present invention, the maximum On current of described photoflash lamp is 90mA.Described microprocessor, in the time controlling the electric current of photoflash lamp, first calculates sample rate current according to described sampled voltage; Then sample rate current is compared with maximum On current and export corresponding control signal; In the time that sample rate current is greater than the maximum On current of photoflash lamp, drive chip described in the control of described microprocessor output pwm signal, in the time that sample rate current is less than the maximum On current of photoflash lamp, drive chip described in the control of described microprocessor output high level.
In other embodiments, can also realize the control to photoflash lamp by the corresponding relation (as shown in Figure 7) of store sample voltage and pwm signal in microprocessor.And in the time that sampled voltage is greater than 3.8V, drive chip described in the control of described microprocessor output high level, in the time that sampled voltage is less than 3.8V, drive chip controls to drive chip described in the pwm signal control of described microprocessor output corresponding frequencies.
In sum, the method of the constant pressure type flashlight driving circuit of a kind of mobile phone provided by the invention and driving photoflash lamp thereof is sampled to the voltage of photoflash lamp by microprocessor, and according to the pwm signal of sample voltage value output high level or output corresponding frequencies, the electric current of controlling photoflash lamp is being less than or equal to the maximum On current of photoflash lamp, thereby has solved the forward direction conducting voltage V of existing constant pressure type flashlight driving circuit due to photoflash lamp
lEDdifference and cause the photoflash lamp electric current of different mobile phones inconsistent, cannot environment under low-light (level) meet flash of light problem, make the electric current of photoflash lamp at 85mA-90mA, thereby make mobile phone can take clearly image.
Be understandable that, for those of ordinary skills, can be equal to replacement or change according to technical scheme of the present invention and inventive concept thereof, and all these changes or replacement all should belong to the protection range of the appended claim of the present invention.
Claims (7)
1. a constant pressure type flashlight driving circuit for mobile phone, is characterized in that, comprises and drives chip, current-limiting resistance, the first electric capacity, photoflash lamp and microprocessor; The VOUT port of described driving chip is connected with the ADC sample port of microprocessor by described current-limiting resistance, and the positive pole of described photoflash lamp is connected with ADC sample port and the current-limiting resistance of described microprocessor respectively, minus earth; The SHND port of described driving chip is connected with the control port of microprocessor, drives the VIN port of chip to connect power supply, and described the first capacitance series is driving between the C+ port and C-port of chip; Described microprocessor is for the voltage of described photoflash lamp is sampled, and according to the pwm signal of sampled voltage output high level or output corresponding frequencies, the electric current of controlling photoflash lamp is less than or equal to the maximum On current of photoflash lamp; Wherein, described microprocessor is specifically for calculating sample rate current according to described sampled voltage; In the time that sample rate current is greater than the maximum On current of photoflash lamp, described in the control of described microprocessor output pwm signal, drive chip operation, drive the VOUT port output 5V voltage of chip, make photoflash lamp work, in the time that sample rate current is less than the maximum On current of photoflash lamp, described in the control of described microprocessor output high level, drive chip operation, drive the VOUT port output 5V voltage of chip, make photoflash lamp work.
2. the constant pressure type flashlight driving circuit of mobile phone according to claim 1, is characterized in that, the maximum On current of described photoflash lamp is 90mA.
3. the constant pressure type flashlight driving circuit of mobile phone according to claim 1, is characterized in that, also comprises the second electric capacity, and one end of described the second electric capacity connects the VOUT port that drives chip, other end ground connection.
4. the constant pressure type flashlight driving circuit of mobile phone according to claim 1, is characterized in that, also comprises the 3rd electric capacity, and one end of described the 3rd electric capacity connects the VIN port that drives chip, other end ground connection.
5. adopt the constant pressure type flashlight driving circuit of mobile phone claimed in claim 1 to drive a method for photoflash lamp, it is characterized in that, described method comprises:
Open constant pressure type flash lamp circuit;
By microprocessor, the output voltage that drives chip is sampled;
According to the pwm signal of sampled voltage output high level or output corresponding frequencies, the electric current of controlling photoflash lamp is less than or equal to the maximum On current of photoflash lamp; It is specially: described microprocessor calculates sample rate current according to described sampled voltage; In the time that sample rate current is greater than the maximum On current of photoflash lamp, described in the control of described microprocessor output pwm signal, drive chip operation, drive the VOUT port output 5V voltage of chip, make photoflash lamp work, in the time that sample rate current is less than the maximum On current of photoflash lamp, described in the control of described microprocessor output high level, drive chip operation, drive the VOUT port output 5V voltage of chip, make photoflash lamp work.
6. the method for driving photoflash lamp according to claim 5, is characterized in that, the maximum On current of described photoflash lamp is 90mA.
7. the method for driving photoflash lamp according to claim 6, it is characterized in that, in the time that sampled voltage is greater than 3.8V, described in the control of described microprocessor output high level, drive chip, in the time that sampled voltage is less than 3.8V, drive chip controls to drive chip described in the pwm signal control of described microprocessor output corresponding frequencies.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201110389968.4A CN102420888B (en) | 2011-11-30 | 2011-11-30 | Constant-voltage flashlight drive circuit of mobile phone and method for driving flashlight by constant-voltage flashlight drive circuit |
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| CN201110389968.4A CN102420888B (en) | 2011-11-30 | 2011-11-30 | Constant-voltage flashlight drive circuit of mobile phone and method for driving flashlight by constant-voltage flashlight drive circuit |
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| CN102420888B true CN102420888B (en) | 2014-06-25 |
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| CN201252662Y (en) * | 2008-05-09 | 2009-06-03 | 深圳市东辰科技有限公司 | Constant current drive circuit for realizing high brightness LED lamp through utilizing switch power supply chip |
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| WO2011127227A1 (en) * | 2010-04-09 | 2011-10-13 | Microsemi Corporation | Sampling external voltage which may exceed integrated circuit maximum voltage rating |
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