CN102316284A - System for realizing drive of EMCCD signal by transformer - Google Patents

Abstract

The invention relates to the CCD driving technology, more particularly to a system for realizing drive of an EMCCD signal by a transformer. According to the invention, problems that a current driving method has high power and is difficult to be realized can be solved. An amplitude adjustment of an output signal of the system is carried out by changing a resistance value of a digital potentiometer in a first adjustable voltage transformer, so that an output voltage of the first adjustable voltage transformer is changed and thus a primary coil voltage of a high frequency transformer; therefore, a digital control on the output signal amplitude is realized; according to a digital parameter value received by the second adjustable transformer, a resistance value of a digital potentiometer in the second adjustable transformer is changed, thereby changing an output voltage value in a DC-DC boosted circuit; and a direct current polarization is provided for an RLC resonant circuit through a direct current level clamped circuit, so that the high and low levels of the output signal are still in a normal working range after the change of the amplitude value of the output signal each time. According to the invention, circuit power consumption and dependence on a high speed and high power device are substantially reduced.

Description

A kind of transformer is realized the system that the EMCCD signal drives

Technical field

The present invention relates to the Driving technique of a kind of CCD, be specifically related to the realization system of the high speed and high pressure drive signal of a kind of EMCCD.

Background technology

When dark target is carried out to picture, if the sense amplifier noise ratio of CCD is bigger, usually can cover useful signal, especially under the reading speed condition with higher, reading noise can increase along with the raising of reading speed.Along with the continuous development of CCD manufacture craft, the appearance of EMCCD makes small signal also can overcome the noise of sense amplifier, and this type of CCD can access the much the same picture quality with ICCD under the situation of additional structure; The basic structure of EMCCD and traditional frame transfer CCD are roughly the same, but between readout register and sense amplifier, have added hundreds of gain register, and its electrode structure is different from branch register, and signal has obtained gain here.In gain register; Realize that the required high voltage electric field of avalanche multiplication is formed by big potential difference between adjacent electrode in gain register; The amplitude signal of about 20～50V on the common electrode and another electrode keeps low Dc bias, thus the potential difference regulation and control multiplication factor between two electrodes changed through the high level of regulating the amplitude pulse.

How the digitizing technique with Analog Electronics Technique and computer combines, and for the driving of EMCCD new technological means being provided is technical problem to be solved by this invention.

Summary of the invention

The present invention provides a kind of transformer to realize the system that the EMCCD signal drives for solving the problem that existing driving method power consumption is big and be difficult to realize.

A kind of transformer is realized the system that the EMCCD signal drives, and this system comprises that controller, analog to digital conversion circuit, MOSFET, integrated drive, the first adjustable electric depressor, the second adjustable electric depressor, amplitude calculating circuit, alternating current component are extracted circuit, DC component is extracted circuit, pressure sampling circuit, the clamped circuit of DC level, high frequency transformer, controllable impedance and adjustable resistance;

The output of said controller is connected with the input of the first adjustable electric depressor, the input of the second adjustable electric depressor and the input of integrated drive respectively; Said controller is to integrated drive input timing drive signal, and controller is respectively to the first adjustable electric depressor and the corresponding digital parameters value of second adjustable electric depressor output;

The output of integrated drive is connected with the grid of MOSFET, and the drive signal of integrated drive output is as the drive signal of MOSFET; The drain electrode of said MOSFET is connected with an end of high frequency transformer primary coil; The high frequency transformer primary coil is as the load of MOSFET; The output of the said first adjustable electric depressor is connected with the other end of high frequency transformer primary coil; The voltage of first adjustable electric depressor output is as the supply power voltage of high frequency transformer primary coil; One end of said high frequency transformer secondary coil is connected with the input of the clamped circuit of DC level; The other end of high frequency transformer secondary coil is connected with an end of controllable impedance, and the other end of controllable impedance is connected with an end of adjustable resistance, and the other end of adjustable resistance is connected with the pin of EMCCD; The equivalent capacity of the pin of said high frequency transformer, controllable impedance, adjustable resistance and EMCCD is formed the series resonant circuit of RLC, the said second adjustable electric depressor output voltage through the clamped circuit of DC level to RLC resonant circuit bias current;

The input of said pressure sampling circuit is connected with the pin of EMCCD; The output of pressure sampling circuit extracts the input of circuit with alternating current component respectively, the input that DC component is extracted circuit is connected; The output that said alternating current component is extracted circuit is connected with the input of amplitude calculating circuit; The output of amplitude calculating circuit is connected with the input of analog to digital conversion circuit; The output that said DC component is extracted circuit is connected with the input of analog to digital conversion circuit, and the output of analog-digital conversion circuit as described is connected with the input of controller; The low-voltage signal of the proportional relation of pin signal of said pressure sampling circuit collection and EMCCD; Said low-voltage signal obtains to exchange level signal and dc level signal respectively after alternating current component is extracted circuit and DC component is extracted circuit; Said interchange level signal is sent to analog to digital conversion circuit behind amplitude calculating circuit; Analog-digital conversion circuit as described with dc level signal be sent to controller after the amplitude leyel signal digital that exchanges level signal quantizes; Said controller obtains the highest and minimum level value of current output signal according to the digital signal of input, carries out closed-loop control.

Beneficial effect of the present invention:

One, high speed and high pressure drive signal of the present invention mainly adopts the equivalent capacity of EMCCD pin and the inductance composition RLC series resonant circuit of external transformer to obtain; Greatly reduce requirement, also greatly reduce the power consumption of this circuit simultaneously driving element;

Two, thereby the amplitude adjusted of output signal changes the output voltage of the first adjustable electric depressor through the resistance value that changes digital regulation resistance in the first adjustable electric depressor and then has changed the primary coil voltage of high frequency transformer in the system of the present invention, has realized the digital control of amplitude output signal;

Three, the digital parameters value that receives through the second adjustable electric depressor of the present invention; Change the resistance value of digital regulation resistance in the second adjustable electric depressor; Thereby change the output voltage values in the DC-DC booster circuit; And to the RLC resonant circuit direct current biasing being provided through the clamped circuit of DC level, the high-low level that makes output signal after each change amplitude output signal value is still in normal working range;

Four, the present invention adopts analogy method to handle the output signal, can monitor the highest minimum level value of this high speed and high pressure drive signal in real time, realizes the closed-loop control of output signal level, guarantees that simultaneously this pin voltage is in normal working range all the time.

Description of drawings

Fig. 1 is the schematic diagram that a kind of transformer of the present invention is realized the system that the EMCCD signal drives;

Fig. 2 is that a kind of transformer of the present invention is realized the system block diagram that the EMCCD signal drives.

Embodiment

Embodiment one, combination Fig. 1 and Fig. 2 explain this execution mode; A kind of transformer is realized the system that the EMCCD signal drives, and this system comprises that controller, analog to digital conversion circuit, MOSFET, integrated drive, the first adjustable electric depressor, the second adjustable electric depressor, amplitude calculating circuit, alternating current component are extracted circuit, DC component is extracted circuit, pressure sampling circuit, the clamped circuit of DC level, high frequency transformer, controllable impedance and adjustable resistance; The input of the input of said controller output end and integrated drive, the first adjustable electric depressor input, the second adjustable electric depressor is connected; Said controller is to integrated drive input timing drive signal; And according to current gain requirement, respectively to the first adjustable electric depressor and the corresponding digital parameters value of second adjustable electric depressor output; The output of said integrated drive links to each other with the grid of MOSFET, and the signal of its output is as the drive signal of MOSFET; Said high frequency transformer primary coil is as the load of MOSFET, and the one of which end links to each other with the drain electrode of MOSFET; The output of the first adjustable electric depressor is connected with the other end of high frequency transformer primary coil; According to the corresponding voltage of digital parameters value output that receives; This voltage can be realized the digital control of amplitude output signal like this as the supply power voltage of the primary coil of high frequency transformer; One end of high frequency transformer secondary coil is connected with the clamped circuit of DC level, and the other end is connected with controllable impedance, adjustable resistance and EMCCD pin, forms the series resonant circuit of RLC; The said second adjustable electric depressor is exported corresponding voltage according to the digital parameters value that receives, and to the RLC resonant circuit direct current biasing is provided through the clamped circuit of DC level; The controllable impedance effect is to guarantee that rlc circuit circuit under specific operating frequency is in resonance condition; Adjustable resistance is used for the quality factor q of trimming circuit, can in the debug process of circuit resonance, be used for current limliting simultaneously and prevent that the signal on the EMCCD pin from exceeding the normal range of operation of this device.The low-voltage signal of the proportional relation of pin signal of said pressure sampling circuit collection and EMCCD extracts circuit and DC component extraction circuit through alternating current component respectively, obtains DC level and AC signal; Dc level signal can directly be sent into analog to digital conversion circuit and carry out digital quantization; AC signal in amplitude calculating circuit through square, two times amplify and extracting operation after obtain the amplitude information of sinusoidal signal, also send into analog to digital conversion circuit then and carry out digital quantization; Analog-digital conversion circuit as described the two paths of signals digital quantization after, send in the controller; Controller can calculate the highest minimum level value of current output signal according to the digital feedback signal of input, carries out closed-loop control;

The described controller of this execution mode is the FPGA of Xilinx company; Described integrated drive is the high-speed driver of Intersil company; Said MOSFET is the MOSFET of the model FDD5612 of fairchild company production.

The described high frequency transformer of this execution mode is a customed product, can adjust concrete parameter according to instructions for use; The second adjustable electric depressor mainly comprises DC-DC booster power chip and digital regulation resistance, and the denumerable tone of Chinese characters of output voltage is whole; The clamped circuit of DC level is mainly the speed-sensitive switch diode; The first adjustable electric depressor mainly comprises DC-DC power supply chip and digital regulation resistance, and the denumerable tone of Chinese characters of output voltage is whole.

The described controllable impedance of this execution mode is the inductance of manual coiling, can carry out meticulous inductance value adjustment, and dc resistance is very little; Adjustable resistance is the bigger resistance of rated disspation; Said EMCCD is the EMCCD of E2V company; Described pressure sampling circuit is mainly resistance; It is high pass filter that alternating current component is extracted circuit; It is low pass filter that DC component is extracted circuit; Said amplitude calculating circuit is mainly analog multiplier; Described analog to digital conversion circuit is mainly the high-speed digital-analog conversion chip of two-way.

The model that CCD of the present invention drives pin is the series connection of resistance (resistance is less) and electric capacity; The model of high frequency transformer secondary coil is the self-induction of a resistance, secondary coil and the series connection of primary coil mutual inductance, requires the resistance value in the high frequency transformer model very little in the present invention; In conjunction with Fig. 1, R1 is the equivalent d.c. resistance of the primary coil of high frequency transformer, and R2 is the secondary coil of high frequency transformer and the equivalent resistance sum that CCD drives pin; C1 is the equivalent capacity that EMCCD drives pin, and the appearance value is C, and its voltage value is U _OThe drive signal amplitude of input is U _S, angular frequency is ω (frequency is f); The primary coil self-induction of high frequency transformer is L ₁, the secondary coil self-induction is L ₂, mutual inductance is M;

The capacitive reactance of electric capacity $X_C=\frac{1}{\mathrm{\ω\; C}}=\frac{1}{2\mathrm{\π\; FC}},$

When the sinusoidal signal amplitude that requires its two ends is 50V, when frequency was 20MHz, when the appearance value was 100pF, then current amplitude did $I=\frac{U}{X_C}=2\mathrm{\π\; f}{U}_{O}C=2\mathrm{\π}\×20\×{10}^6\×50\×100\×{10}^{-12}=0.2\mathrm{\π}\left(A\right);$

When adopting the traditional driving working method, the peak power P=U of driver output _OI=10 π (W); The maximum working voltage of integrated high-speed driver now can not satisfy the requirement about 50V about 20V; Adopt two discrete high-speed high-power MOSFET to satisfy and drive requirement, but optional MOSFET kind is limited and buy difficulty, the power consumption of entire circuit is big, has increased the weight of the EMCCD low temperature environment burden of work down.

In conjunction with Fig. 1, according to Thevenin's theorem, when capacitor C 1 was broken off, the voltage at its two ends was:

$U_{\∞}=\frac{\mathrm{j\ωM}{U}_S}{R_1+\mathrm{j\ω}{L}_1}$

The equivalent internal resistance of circuit is anti-to be:

$Z_O=\mathrm{j\ω}{L}_2+\frac{{\mathrm{\ω}}^2{M}^2}{R_1+\mathrm{j\ω}{L}_1}+R_{\text{2}}$

The total impedance in high frequency transformer secondary coil loop is:

When $Z_G=\mathrm{J\ω}{L}_2+\frac{{\mathrm{\ω}}^2{M}^2}{R_1+\mathrm{J\ω}{L}_1}+\frac{1}{\mathrm{J\ω}{C}_1}+R_2$ Imaginary part be 0 o'clock,

Then the high frequency transformer out-secondary is in resonance condition, establishes R _2aEquivalent resistance when being in resonance condition for the high frequency transformer out-secondary, then the signal amplitude on the capacitor C 1 is:

$U_O=\frac{{\mathrm{MU}}_S}{(R_1+\mathrm{j\ω}{L}_1)R_{2a}C}$

The quality factor of circuit $Q=\frac{U_O}{U_S}=\frac{M}{(R_1+\mathrm{J\ω}{L}_1)R_{2a}C};$

Adopt analogy method of the present invention to handle the high speed sinusoidal signal on the CCD pin, obtain that it is the highest following with the method minimum level value:

Drive signal on the CCD pin can superpose with direct current and AC signal and represent,

Asin(ωt)+A _O

When doing through the signal that obtains behind the pressure sampling circuit

kAsin(ωt)+kA _O(0＜k＜1)

DC component is kA _O, alternating current component is kAsin (ω t)

After alternating current component is simultaneously sent into multiplier as multiplier and multiplicand

${\left[\mathrm{kA}\sin \left(\mathrm{\ωt}\right)\right]}^2=k^2{A}^2{\sin }^2\left(\mathrm{\ωt}\right)=\frac{k^2{A}^2[1-\cos \left(2\mathrm{\ωt}\right)]}{2};$

After the alternating current component of filtering result of product again the signal that obtains of two times of amplifications be k ²A ²Can obtain signal kA through extracting operation, said kA can obtain the amplitude A of sinusoidal signal after divided by scale factor k; KA _ODivided by the DC level value A that can obtain sinusoidal signal behind the scale factor k _OThe maximum level value that then can finally calculate the output signal is A _O+ A, the minimum level value is A _O-A;

The present invention can realize digital control to the output signal, greatly reduces circuit power consumption and to the dependence of high-speed high-power device, and through real-time monitoring output signal, guarantees that its high-low level value is all in the working range that device allows.

Claims (2)

1. a transformer is realized the system that the EMCCD signal drives, and this system comprises that controller, analog to digital conversion circuit, MOSFET, integrated drive, the first adjustable electric depressor, the second adjustable electric depressor, amplitude calculating circuit, alternating current component are extracted circuit, DC component is extracted circuit, pressure sampling circuit, the clamped circuit of DC level, high frequency transformer, controllable impedance and adjustable resistance; It is characterized in that the output of said controller is connected with the input of the first adjustable electric depressor, the input of the second adjustable electric depressor and the input of integrated drive respectively; Said controller is to integrated drive input timing drive signal, and controller is respectively to the first adjustable electric depressor and the corresponding digital parameters value of second adjustable electric depressor output;

The output of integrated drive is connected with the grid of MOSFET, and the drive signal of integrated drive output is as the drive signal of MOSFET; The drain electrode of said MOSFET is connected with an end of high frequency transformer primary coil; The high frequency transformer primary coil is as the load of MOSFET; The output of the said first adjustable electric depressor is connected with the other end of high frequency transformer primary coil; The voltage of first adjustable electric depressor output is as the supply power voltage of high frequency transformer primary coil; One end of said high frequency transformer secondary coil is connected with the input of the clamped circuit of DC level; The other end of high frequency transformer secondary coil is connected with an end of controllable impedance, and the other end of controllable impedance is connected with an end of adjustable resistance, and the other end of adjustable resistance is connected with the pin of EMCCD; The equivalent capacity of the pin of said high frequency transformer, controllable impedance, adjustable resistance and EMCCD is formed the series resonant circuit of RLC, the said second adjustable electric depressor output voltage through the clamped circuit of DC level to RLC resonant circuit bias current;

The input of said pressure sampling circuit is connected with the pin of EMCCD; The output of pressure sampling circuit extracts the input of circuit with alternating current component respectively, the input that DC component is extracted circuit is connected; The output that said alternating current component is extracted circuit is connected with the input of amplitude calculating circuit; The output of amplitude calculating circuit is connected with the input of analog to digital conversion circuit; The output that said DC component is extracted circuit is connected with the input of analog to digital conversion circuit, and the output of analog-digital conversion circuit as described is connected with the input of controller; The low-voltage signal of the proportional relation of pin signal of said pressure sampling circuit collection and EMCCD; Said low-voltage signal obtains to exchange level signal and dc level signal respectively after alternating current component is extracted circuit and DC component is extracted circuit; Said interchange level signal is sent to analog to digital conversion circuit behind amplitude calculating circuit; Analog-digital conversion circuit as described with dc level signal be sent to controller after the amplitude leyel signal digital that exchanges level signal quantizes; Said controller obtains the highest and minimum level value of current output signal according to the digital signal of input, carries out closed-loop control.

2. a transformer is realized the system that the EMCCD signal drives, and it is characterized in that the described first adjustable electric depressor and the second adjustable electric depressor mainly comprise DC-DC booster power chip and digital regulation resistance, output adjustable digital voltage.

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