CN102403892A - Power switching circuit and network camera using same - Google Patents

Abstract

The invention provides a power switching circuit and a network camera using the same. The network camera comprises a system power source and a light sensing element, and the power switching circuit comprises a voltage division circuit and a voltage conversion module. The voltage division circuit comprises a first voltage division element and a second voltage division element which are in series connection with each other, and the voltage conversion module comprises a linear voltage regulator. The linear voltage regulator comprises an input end, a feedback end and an output end, wherein the input end is in electrical connection with the system power source, the feedback end is electrically connected between the first voltage division element and the second voltage division element, and the output end is in electric connection with the first voltage division element. The power switching circuit improves universality of a network camera mainboard and reduces design difficulty of the mainboard.

Description

Power-switching circuit and use the network camera of this power-switching circuit

Technical field

The present invention relates to a kind of power-switching circuit, relate in particular to a kind of power-switching circuit that is applied to network camera.

Background technology

In the design of network camera; Usually with central processing unit (Central processing unit; CPU)/system level chip (System on Chip; SOC), image compression chip, audio chip, network chip and system power supply be arranged on the mainboard, simultaneously with complementary metal oxide semiconductors (CMOS) (Complementary Metal Oxide Semiconductor, CMOS) transducer or Charged Coupled Device (Charge Coupled Device; CCD) Photosensing Units such as transducer and be arranged on the daughter board for this Photosensing Units provides the sub-power supply of operating voltage, wherein this sub-power source voltage is provided by system power supply.Yet, when needs are changed the Photosensing Units of different model, not only need on daughter board, carry out the dismounting operation under most of situations, and supply line's design that need change mainboard simultaneously thinks that the Photosensing Units of newly changing provides suitable operating voltage.Obviously, this design can increase the design difficulty of mainboard, and is unfavorable for improving the versatility of mainboard.

Summary of the invention

In view of above situation, be necessary to provide a kind of mainboard versatility that improves, support mainboard and polytype daughter board shared power-switching circuit.

In addition, also be necessary to provide a kind of network camera of using said power-switching circuit.

A kind of power-switching circuit; It is applied to a network camera, and this network camera comprises a system power supply and a Photosensing Units, and this power-switching circuit comprises a bleeder circuit and a voltage transformation module; This bleeder circuit comprises one first sectional pressure element and one second sectional pressure element that is in series; This voltage transformation module comprises a linear voltage regulator, and this linear voltage regulator comprises an input, a feedback end and an output, and this input and system power supply electrically connect; This feedback end is electrically connected between first sectional pressure element and second sectional pressure element, and this output is electrically connected at first sectional pressure element.

A kind of network camera; It comprises a system power supply and a Photosensing Units and a power-switching circuit; This power-switching circuit comprises a bleeder circuit and a voltage transformation module, and this bleeder circuit is in order to produce a feedback voltage and to feed back to voltage transformation module, and this voltage transformation module is preset a reference voltage; This voltage transformation module comparison reference voltage and feedback voltage, and the voltage transitions of regulating system power supply through negative feedback becomes a burning voltage for Photosensing Units work.

Above-mentioned power-switching circuit feeds back a feedback voltage through bleeder circuit to linear voltage regulator, makes linear voltage regulator export a stable voltage for Photosensing Units work.This power-switching circuit is through changing the operating voltage that first sectional pressure element or second sectional pressure element can obtain different Photosensing Units; The supply line's design that need not to change mainboard can make the multiple daughter board of the mainboard Photosensing Units different with the installing model shared; Improve the versatility of mainboard, reduced the design difficulty of mainboard simultaneously.

Description of drawings

Fig. 1 is the circuit diagram of the network camera of preferred embodiments of the present invention;

Fig. 2 is the circuit diagram of the power-switching circuit of network camera shown in Figure 1.

The main element symbol description

Power-switching circuit	100
		Voltage transformation module	10
Linear voltage regulator	12
		Input	VIN
Output	VOUT
		Feedback end	FB
First electric capacity	C1
		Second electric capacity	C2
The 3rd electric capacity	C3
		Bleeder circuit
	20
		First sectional pressure element	22
Second sectional pressure element	24
		Node	A
Feedback voltage	Vfb
		Analog/digital converter	30
Network camera	200
		Mainboard	220
System level chip	222
		System power supply	224
Daughter board	240
		Photosensing Units	242
Sub-power supply	244

Embodiment

See also Fig. 1, the present invention provides a kind of power-switching circuit 100, and it is applied in the network camera 200.

This network camera 200 comprises a mainboard 220 and a daughter board 240.This mainboard 220 is provided with electronic building bricks such as a system level chip (SOC) 222, a system power supply 224 and audio chip, network chip (figure does not show).This system level chip 222 is through calling each class method of storage inside, so that network camera 200 is final through network output video information.These system power supply 224 usefulness think that the electronic building brick on mainboard 220 and the daughter board 240 provides operating voltage.This daughter board 240 is provided with a Photosensing Units 242 and a sub-power supply 244.This Photosensing Units 242 can be a CMOS or ccd sensor, in order to convert optical signalling into digital electric signal, uses and realizes obtaining, store and transmitting of image.This sub-power supply 244 electrically connects with Photosensing Units 242 and for Photosensing Units 242 suitable operating voltage is provided.

This power-switching circuit 100 is electrically connected between system power supply 224 and the sub-power supply 244, in order to the voltage of receiving system power supply 224, and this voltage is adjusted the back export burning voltages to sub-power supply 244.This power-switching circuit 100 comprises a voltage transformation module 10, a bleeder circuit 20 and an analog/digital converter (analog-to-digital converter, ADC) 30.

Please combine to consult Fig. 2, this voltage transformation module 10 is arranged on the mainboard 220, and it comprises a linear voltage regulator 12, one first capacitor C 1 and one second capacitor C 2.In the present embodiment, this linear voltage regulator 12 is that (Low Dropout Regulator, LDO), it is preset with a reference voltage Vref to a low dropout voltage regulator.This linear voltage regulator 12 is used for a comparison reference voltage Vref and a feedback voltage Vfb, produces a control signal by this with through the constant voltage of inner negative feedback adjustment output one.This linear voltage regulator 12 comprises an input VIN, an output VOUT and a feedback end FB.This input VIN and system power supply 224 electrically connects, in order to the direct voltage of receiving system power supply 224, and through DC-DC (DC-to-DC) conversion after output VOUT output.This feedback end FB is in order to receive said feedback voltage Vfb from bleeder circuit 20.This first capacitor C 1 and second capacitor C 2 all strobe, and be steady with the voltage that makes input VIN and output VOUT respectively, reduces ripple.Wherein, these first capacitor C, 1 one ends and input VIN electrically connect, other end ground connection.These second capacitor C, 2 one ends and output VOUT electrically connect, other end ground connection.

This bleeder circuit 20 is arranged on the daughter board 240, in order to producing said feedback voltage Vfb, and feeds back to linear voltage regulator 12.This bleeder circuit 20 comprises one first sectional pressure element 22, one second sectional pressure element 24 and one the 3rd capacitor C 3.In the present embodiment, this first sectional pressure element 22 and second sectional pressure element 24 are a resistance.These first sectional pressure element, 22 1 ends and sub-power supply 244 electrically connect, and are electrically connected at the output VOUT of linear voltage regulator 12 simultaneously through modes such as soft arranging wire or splicing ear cablings, and the other end and second sectional pressure element 24 electrically connect, and form a node A.This node A electrically connects through the feedback end FB of modes such as soft arranging wire or splicing ear cabling with linear voltage regulator 12, by this with linear voltage regulator 12 formation one feedback control loop.Obviously, the voltage at this node A place is said feedback voltage Vfb.The other end ground connection of this second sectional pressure element 24.The 3rd capacitor C 3 is a filter capacitor, and the one of which end is electrically connected to the end that first sectional pressure element 22 is connected with output VOUT, other end ground connection.

This analog/digital converter 30 is arranged on the daughter board 240, and the one of which end is electrically connected to the end that first sectional pressure element 22 is connected with output VOUT, and the other end is electrically connected at system level chip 222 through I2C (Inter-Integrated Circuit) bus.This analog/digital converter 30 is used to gather the stable voltage value signal of the output VOUT of linear voltage regulator 12; And this voltage value signal is sent to system level chip 222 after analog/digital conversion; So that system level chip 222 is judged the model of Photosensing Units 242 in running order on the daughter board 240 according to the magnitude of voltage of output VOUT output, and export corresponding control program.

When these network camera 200 work, the output VOUT voltage of setting linear voltage regulator 12 is V, and the resistance value of first sectional pressure element 22 is R1, and the resistance value of second sectional pressure element 24 is R2, by:

$\mathrm{Vfb}=\frac{\mathrm{VR}2}{R1+R2}$

Draw:

V＝Vfb×(1+R1/R2)

Simultaneously; These linear voltage regulator 12 comparison reference voltage Vref and feedback voltage Vfb; And equal reference voltage Vref until feedback voltage Vfb through the voltage V that output VOUT is regulated in negative feedback; Output VOUT will export stable voltage V this moment, and send this stable voltage V to sub-power supply 244 for Photosensing Units 242 work.This analog/digital converter 30 is gathered the stable voltage signal of output VOUT simultaneously, and finally through 242 work of system level chip 222 control Photosensing Units.

When needs are changed Photosensing Units 242; Because each LDO all has a reference voltage Vref; And reference voltage Vref=feedback voltage Vfb can be known when being stablized by this power-switching circuit 100; Only need change the voltage V that the first different sectional pressure elements 22 or second sectional pressure element 24 can change linear voltage regulator 12 output VOUT this moment, and then for Photosensing Units 242 needed operating voltage is provided.

Be appreciated that first sectional pressure element 22 of the present invention and second sectional pressure element 24 can not be also to can be other passive blocks such as electric capacity, inductance by resistance.

Be appreciated that sub-power supply 244 of the present invention also can omit, the output VOUT of linear voltage regulator 12 directly was electrically connected at Photosensing Units 242 and got final product this moment.

The present invention is by a linear voltage regulator 12 is set on the mainboard 220 of network camera 200; And a bleeder circuit 20 is set on daughter board 240, regulate that through linear voltage regulator 12 negative feedbacks output VOUT is worked for Photosensing Units 242 to sub-power supply 244 outputs one stable voltage.This power-switching circuit 100 is through changing the operating voltage that first sectional pressure element 22 or second sectional pressure element 24 can obtain different Photosensing Units 242; And the supply line's design that need not to change mainboard 220 can make the multiple daughter board 240 of mainboard 220 Photosensing Units 242 different with the installing model shared; Improve the versatility of mainboard 220, reduced the design difficulty of mainboard 220 simultaneously.

Claims (11)

1. power-switching circuit; It is applied to a network camera, and this network camera comprises a system power supply and a Photosensing Units, it is characterized in that: this power-switching circuit comprises a bleeder circuit and a voltage transformation module; This bleeder circuit comprises one first sectional pressure element and one second sectional pressure element that is in series; This voltage transformation module comprises a linear voltage regulator, and this linear voltage regulator comprises an input, a feedback end and an output, and this input and system power supply electrically connect; This feedback end is electrically connected between first sectional pressure element and second sectional pressure element, and this output is electrically connected at first sectional pressure element.

2. power-switching circuit as claimed in claim 1 is characterized in that: said power-switching circuit also comprises an analog/digital converter, and said analog/digital converter is electrically connected at the output of linear voltage regulator.

3. power-switching circuit as claimed in claim 1; It is characterized in that: said voltage transformation module also comprises one first electric capacity and one second electric capacity; The input of said first electric capacity, one end and linear voltage regulator electrically connects; Other end ground connection, the output of said second electric capacity, one end and linear voltage regulator electrically connects, other end ground connection.

4. power-switching circuit as claimed in claim 1 is characterized in that: said bleeder circuit also comprises one the 3rd electric capacity, and said the 3rd electric capacity one end is electrically connected to the end that first sectional pressure element is connected with the output of linear voltage regulator, other end ground connection.

5. power-switching circuit as claimed in claim 1 is characterized in that: the other end ground connection of said second sectional pressure element.

6. power-switching circuit as claimed in claim 1 is characterized in that: said first sectional pressure element and second sectional pressure element are a resistance.

7. power-switching circuit as claimed in claim 1 is characterized in that: said linear voltage regulator is a low dropout voltage regulator.

8. network camera; It comprises a system power supply and a Photosensing Units; It is characterized in that: this network camera also comprises a power-switching circuit; This power-switching circuit comprises a bleeder circuit and a voltage transformation module, and this bleeder circuit is in order to produce a feedback voltage and to feed back to voltage transformation module, and this voltage transformation module is preset a reference voltage; This voltage transformation module comparison reference voltage and feedback voltage, and the voltage transitions of regulating system power supply through negative feedback becomes a burning voltage for Photosensing Units work.

9. network camera as claimed in claim 8 is characterized in that: said network camera comprises a mainboard and a daughter board, and said system power supply and voltage transformation module are arranged on the mainboard, and said bleeder circuit is arranged on the daughter board.

10. network camera as claimed in claim 8; It is characterized in that: said network camera also comprises a system level chip; Said power-switching circuit also comprises an analog/digital converter; Said analog/digital converter becomes digital signal and is sent to system level chip in order to the burning voltage conversion of signals with voltage transformation module output, and said system level chip is judged the model of current in running order Photosensing Units and output corresponding control programs according to the digital signal that receives.

11. network camera as claimed in claim 8; It is characterized in that: said bleeder circuit comprises one first sectional pressure element and one second sectional pressure element that is in series; Said voltage transitions mould comprises a linear voltage regulator, and this linear voltage regulator comprises an input, a feedback end and an output, and this input and system power supply electrically connect; This feedback end is electrically connected between first sectional pressure element and second sectional pressure element, and this output is electrically connected at first sectional pressure element.

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