CN102565744B - Pointer instrument adopting capacitance voltage-reducing type power supply - Google Patents

Abstract

The invention relates to a pointer instrument adopting a capacitance voltage-reducing type power supply, which comprises a capacitance voltage-reducing circuit, a rectifier circuit, a protective circuit, a filter capacitor, a DC-DC voltage conversion circuit and a power supply filter capacitor, wherein a header control circuit comprises a keyboard circuit, a singlechip, an integrating circuit and a current-limiting resistor, the voltage-reducing circuit, the rectifier circuit, the protective circuit, the filter capacitor, the DC-DC voltage conversion circuit and the power supply filter capacitor are sequentially connected; and the keyboard circuit is electrically connected with an I/O pin of the singlechip, and the singlechip is used for converting physical quantities of voltage, power and the like acquired by a detection circuit into physical quantity signals, and the physical quantity signals are output through a pulse width modulation (PWM) module after operated and corrected, and then filtered through the integrating circuit to drive a pointer instrument header through the current-limiting resistor. The pointer instrument adopting the capacitance voltage-reducing type power supply, provided by the invention, has the advantages of high precision, small volume, less generated heat, low production cost, enhanced impact resistance and prolonged service life.

Description

A kind of pointer instrument that adopts the capacitor step-down power supply

Technical field

The present invention relates to a kind of pointer instrument, particularly a kind of high linearity pointer instrument that uses the capacitor step-down power supply.

Background technology

At present, all be accustomed to the operation conditions with generator on the indication boats and ships such as needle dc voltmeter, power meter, power factor meter, frequency meter on various ships.This class table is low in energy consumption, and its power supply mostly adopts by resistance 220V or 380V are reduced to the instrument required voltage; Perhaps with transformer, 220V or 380V lower voltage are arrived to the instrument required voltage.And one or more generator is generally arranged by grid-connected use on various ships, and can open at any time or close as required certain or a plurality of generator, larger to the impact of electrical network like this.Reduced the serviceable life of above all kinds of instrument.Can produce more heat during the work of the first resistance voltage dropping power supply, the gauge internal temperature is raise, affect accuracy of instrument; The second transformer pressure-reducing cost is high, and power volume is large.At present, other capacitor step-down power circuits, without the DC-DC voltage conversion circuit, forceful electric power has serial interference to power supply, can only be for controlling, can not for detection of.The indicated data of pointer instrument gauge outfit become non-linear with the electric current of input, and degree of accuracy is low.

Summary of the invention

In order to solve, the prior art degree of accuracy is low, cost is high, produce the problems such as heat is many, the invention provides that a kind of degree of accuracy is high, the step-down cost is low, produces that heat is few, the pointer instrument of shock resistance, long service life.

The technical scheme that the present invention solves the problems of the technologies described above is as follows: a kind of pointer instrument that adopts the capacitor step-down power supply comprises:

Capacity voltage dropping circuit, rectification circuit, holding circuit, filter capacitor, DC-DC voltage conversion circuit and power filtering capacitor, the gauge outfit control circuit comprises keyboard circuit, single-chip microcomputer, testing circuit, integrating circuit, current-limiting resistance and pointer instrument gauge outfit, the input end of described capacity voltage dropping circuit is electrically connected to external ac power source, the output terminal of described capacity voltage dropping circuit is electrically connected to the input end of rectification circuit, the output terminal of described rectification circuit is electrically connected to the input end of holding circuit, the output of described holding circuit is electrically connected to the input end of DC-DC voltage conversion circuit after filter capacitor, the output of DC-DC voltage conversion circuit again after power filtering capacitor as the output of power supply, in described gauge outfit control circuit, keyboard circuit is electrically connected to the single-chip microcomputer pin, the output of the pulse-width modulation PWM module on single-chip microcomputer is electrically connected to the input end of integrating circuit, the output terminal of integrating circuit is electrically connected to current-limiting resistance, and described current-limiting resistance and pointer instrument gauge outfit are connected in series.

On the basis of technique scheme, the present invention can also do following improvement.

Further, described capacity voltage dropping circuit comprises decompression capacitor, and described decompression capacitor is in parallel with the resistance that resistance is more than or equal to 10 megaohms, and described resistance bleeds off the stored electric charge of electric capacity two-plate while being used for having a power failure.

Further, described capacity voltage dropping circuit comprises the first decompression capacitor, the second decompression capacitor, described the first decompression capacitor and ac power input end U _nbe electrically connected to described the second decompression capacitor and ac power input end U _lbe electrically connected to, the electric capacity of described the first decompression capacitor and the second decompression capacitor equates, the capacitor value of decompression capacitor determined by static current of lcd I and the line voltage V of instrument,

When external ac power source is single-phase alternating current, the capacitive reactance of decompression capacitor is:

$X_C=\frac{V}{I}---\left(1\right),$

At this moment, the electric capacity of decompression capacitor can be tried to achieve by (2) formula:

$X_C={\mathrm{<figure-callout\; id="1"\; label="X\; C"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">X</figure-callout>}}_C+{\mathrm{<figure-callout\; id="2"\; label="X\; C"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">X</figure-callout>}}_C=\frac{1}{\mathrm{\&omega;}{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}+\frac{1}{\mathrm{\&omega;}{C}_2}---\left(2\right),$

ω=2 π f wherein, the frequency that f is alternating current, X _c1be the capacitive reactance of the first decompression capacitor, X _c2be the capacitive reactance of the second decompression capacitor, X _cit is the total capacitive reactance after two decompression capacitor series connection; C ₁be the electric capacity of the first decompression capacitor, C ₂it is the electric capacity of the second decompression capacitor;

When external ac power source is three-phase alternating current, described capacity voltage dropping circuit comprises the first decompression capacitor, the second decompression capacitor, the 3rd decompression capacitor, described the first decompression capacitor and ac power input end U _abe electrically connected to described the second decompression capacitor and ac power input end U _bbe electrically connected to described the 3rd decompression capacitor and ac power input end U _cbe electrically connected to, the electric capacity of described the first decompression capacitor, the second decompression capacitor and the 3rd decompression capacitor is equal, and the static current of lcd of instrument is:

$I=\frac{U_a}{X_{\mathrm{ca}}}+\frac{U_b}{X_{\mathrm{cb}}}+\frac{U_c}{X_{\mathrm{cc}}}=\frac{U_a}{\frac{1}{\mathrm{\&omega;}{\mathrm{<figure-callout\; id="5"\; label="C"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">C</figure-callout>}}_5}}+\frac{{\mathrm{<figure-callout\; id="1"\; label="U\; b"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">U</figure-callout>}}_b}{\frac{1}{\mathrm{\&omega;}{\mathrm{<figure-callout\; id="6"\; label="C"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">C</figure-callout>}}_6}}+\frac{{\mathrm{<figure-callout\; id="1"\; label="U\; c"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">U</figure-callout>}}_c}{\frac{1}{\mathrm{\&omega;}{C}_7}}---\left(3\right),$

At this moment, the electric capacity of decompression capacitor can be tried to achieve by (3) formula, ω=2 π f wherein, the frequency that f is alternating current, X _cabe the capacitive reactance of the first decompression capacitor, X _cbbe the capacitive reactance of the second decompression capacitor, X _ccbe the capacitive reactance of the 3rd decompression capacitor, the electric capacity that C5 is the first decompression capacitor, the electric capacity that C6 is the second decompression capacitor, the electric capacity that C7 is the 3rd decompression capacitor.

Further, described holding circuit is voltage stabilizing diode, and the negative pole of described voltage stabilizing diode is electrically connected to the output of the positive pole of rectifier bridge, and the positive pole of voltage stabilizing diode is electrically connected to the output of the negative pole of rectifier bridge.

Further, described rectifier bridge is two phase commit bridge or three-phase commutation bridge.

Further, the input voltage of described DC-DC voltage conversion circuit is greater than the instrument required voltage, and be up to 50V, the output voltage of DC-DC voltage conversion circuit is the instrument required voltage, the input voltage that is described DC-DC voltage conversion circuit is less than or equal to 50V, these two kinds of form of presentations have identical connotation, and the output voltage of DC-DC voltage conversion circuit is the instrument required voltage, are the power supplies such as single-chip microcomputer, testing circuit.

Further, described gauge outfit control circuit also comprises testing circuit, and for gathering the physical quantitys such as voltage, power, power factor, frequency, single-chip microcomputer converts the physical quantity collected to digital quantity and exports by the pulse-width modulation PWM module.Pulse-width modulation PWM module in single-chip microcomputer is 8,2 tunnel PWM, and its output forms 16 D/A conversions, and described 16 D/A conversion is divided into most-significant byte and least-significant byte, described most-significant byte is output as PWMO, with first integral resistance, be electrically connected to, described least-significant byte is output as PWM1, with second integral resistance, is electrically connected to.

Further, described integrating circuit comprises two integrating resistors, an integrating capacitor, two input ends of described integrating circuit connect respectively first integral resistance and second integral resistance, first integral resistance is electrically connected to integrating capacitor the first pin after being electrically connected to the output terminal of second integral resistance, is electrically connected to the second pin of described integrating capacitor and power supply.

Static current of lcd I when further, described first integral resistance R is by pointer instrument gauge outfit full scale _swith single-chip microcomputer operating voltage V, determine:

$R\&ap;\frac{V}{I_S}$

The second integral resistance is 2 of described first integral resistance ⁸doubly, consider that the maximum level of PWM output does not reach the supply voltage of single-chip microcomputer, the actual resistance of first integral resistance and second integral resistance should be less than calculated value.Current-limiting resistance is as the semifixed resistor in when calibration.During calibration, by program, allow 2 road PWM export maximum pulse width, the fine setting current-limiting resistance makes the pointer instrument meter pointer point to full scale, realizes the coupling of driving circuit and pointer instrument gauge outfit by the resistance of adjusting current-limiting resistance.

Further, described keyboard circuit for revising the non-linear of pointer instrument, patches it on circuit board during calibrated meter, calibrates complete taking off, and on-keyboard circuit while normally using can reduce cost and the volume of instrument.

The invention has the beneficial effects as follows: utilize decompression capacitor to carry out step-down to ac grid voltage, the volume of power supply is little, and cost is low, the generation heat is few; Adopt filter capacitor to carry out filtering to power supply, adopt voltage stabilizing diode to be protected circuit, so power supply has shock resistance, long service life; Utilize Single Chip Microcomputer (SCM) program control to flow into the electric current of pointer instrument gauge outfit, revise its non-linear with gauge outfit, make the accuracy of instrument rising.

The accompanying drawing explanation

The power supply architecture figure that Fig. 1 is the present invention's pointer ammeter of detecting the every parameter of single-phase alternating current;

Fig. 2 is the power supply architecture figure that the present invention detects the pointer ammeter of three-phase three-wire system or the every parameter of three-phase four-wire system alternating current;

Fig. 3 is pointer instrument gauge outfit control circuit structural drawing of the present invention;

Fig. 4 is the phase waveform schematic diagram of three-phase voltage of the present invention with respect to zero line;

Fig. 5 is the schematic diagram that concerns between pointer instrument gauge outfit deflection angle and drive current;

In accompanying drawing, the list of parts of each label representative is as follows:

1, external ac power source input end, 2, capacity voltage dropping circuit, 3, rectification circuit; 4, holding circuit; 5, filter capacitor, 6, the DC-DC voltage conversion circuit, 7, power filtering capacitor; 8, other partial circuits of instrument; 9, resistance R 1,10, decompression capacitor C1,11, resistance R 2; 12, decompression capacitor C2,13, external ac power source input end U _n, 14, external ac power source input end U _l, 15, commutation diode D1,16, commutation diode D2,17, commutation diode D3,18, commutation diode D4,19, external ac power source input end U _a, 20, external ac power source input end U _b, 21, external ac power source input end U _c, 22, resistance R 3,23, capacitor C 5,24, resistance R 4,25, capacitor C 6,26, resistance R 5,27, capacitor C 7,28, commutation diode D6,29, commutation diode D7,30, commutation diode D8,31, commutation diode D9,32, commutation diode D10,33, commutation diode D11,34, keyboard circuit, 35, testing circuit, 36, single-chip microcomputer, 37, integrating circuit, 38, current-limiting resistance R8,39, pointer instrument gauge outfit, 40, first integral resistance R 6,41, second integral resistance R 7,42, integrating capacitor C

Embodiment

Below in conjunction with accompanying drawing, principle of the present invention and feature are described, example, only for explaining the present invention, is not intended to limit scope of the present invention.

Embodiment 1

As shown in Figure 1, feed circuit for the instrument that detects each parameter of single-phase alternating current, the input end of described capacity voltage dropping circuit 2 is electrically connected to outside single phase alternating current power supply input end 1, the output terminal of described capacity voltage dropping circuit 2 is electrically connected to the input end of rectification circuit 3, the output terminal of described rectification circuit 3 is electrically connected to the input end of holding circuit 4, the output of described holding circuit 4 is electrically connected to the input end of DC-DC voltage conversion circuit 6 after filter capacitor 5 filtering, the output of DC-DC voltage conversion circuit 6 after power filtering capacitor 7 filtering, be again other partial circuits 8 of instrument as the gauge outfit control circuit in single-chip microcomputer, the power supplies such as testing circuit.

Capacity voltage dropping circuit 2 is in parallel with the resistance R 19 that a resistance is more than or equal to 10 megaohms for decompression capacitor C1 10, decompression capacitor C2 12 is in parallel with the resistance R 2 11 that a resistance is more than or equal to 10 megaohms, resistance R 19, R2 11 bleed off the stored electric charge of electric capacity two-plate when having a power failure, the electric current of the resistance R of flowing through during normal operation 19, R2 11 is very faint, can ignore.

The electric capacity C of decompression capacitor C1 10, decompression capacitor C2 12 equates, withstand voltage is much larger than line voltage, and the capacitor value of electric capacity determined by static current of lcd I and the line voltage V of instrument, and for single-phase alternating current, the capacitive reactance of electric capacity is as shown in Figure 1

$X_C=\frac{V}{I}---\left(1\right),$

The electric capacity of decompression capacitor C1 10, decompression capacitor C2 12 can be tried to achieve by following formula

$X_C={\mathrm{<figure-callout\; id="1"\; label="X\; C"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">X</figure-callout>}}_C+{\mathrm{<figure-callout\; id="2"\; label="X\; C"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">X</figure-callout>}}_C=\frac{1}{\mathrm{\&omega;}{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}+\frac{1}{\mathrm{\&omega;}{C}_2}---\left(2\right),$

ω=2 π f wherein, the frequency that f is alternating current, X _c1be capacitive reactance, the X of the first decompression capacitor C1 10 _c2be the capacitive reactance of the second decompression capacitor C2 12, X _cit is the total capacitive reactance after two decompression capacitor series connection; C ₁be electric capacity, the C of the first decompression capacitor C1 10 ₂it is the electric capacity of the second decompression capacitor C2 12.

Holding circuit 4 is voltage stabilizing diode, and the positive pole of described voltage stabilizing diode is electrically connected to the negative pole output of rectification circuit 3, and the negative pole of voltage stabilizing diode is electrically connected to the positive pole output of rectification circuit 3.

Rectification circuit 3 is the two phase commit bridge.

The static current of lcd of known instrument, can obtain according to (1) formula and (2) formula the electric capacity of decompression capacitor C1 10, decompression capacitor C2 12.Actual decompression capacitor C1 10, the comparable calculated value of decompression capacitor C2 12 electric capacity are slightly larger.Prevent voltage ripple of power network.Voltage stabilizing diode in holding circuit 4 is in order to prevent that voltage is higher and set; when voltage ripple of power network or instrument power consumption when on the low side; filter capacitor 5 both end voltage are during higher than the breakdown reverse voltage of the voltage stabilizing diode in holding circuit 4; voltage stabilizing diode reverse-conducting in holding circuit 4, protected subsequent conditioning circuit.Electric current, to filter capacitor 5 chargings, converts the required power supply of instrument to through DC-DC voltage conversion circuit 6, is the power supplies such as single-chip microcomputer, testing circuit.

DC-DC voltage conversion circuit 6 input voltages are greater than the instrument required voltage, and are less than or equal to 50V, are up to 50V, and output voltage is the instrument required voltage, are the power supplies such as single-chip microcomputer, testing circuit.

External ac power source 1 is the one-way communication electricity.

During first 1/4 cycle when alternating current in positive half cycle, electric current is by external ac power source input end u _n13 flow into power circuit, through decompression capacitor C1 10, commutation diode D1 15, filter capacitor 5, commutation diode D4 18, decompression capacitor C2 12, external ac power source input end u _l14 flow out, and this process electric current is to decompression capacitor C1 10, filter capacitor 5, decompression capacitor C2 12 chargings; During second 1/4 cycle of positive half cycle, electric current is by ac power input end u _l14 flow into power circuit, through decompression capacitor C2 12, commutation diode D2 16, filter capacitor 5, commutation diode D3 17, decompression capacitor C1 10, external ac power source input end u _n13 flow out, and this process electric current is to decompression capacitor C1 10, decompression capacitor C2 12 electric discharges, to filter capacitor 5 chargings.

During first 1/4 cycle when alternating current in negative half period, electric current is by external ac power source input end u _l14 flow into power circuit, through decompression capacitor C2 12, commutation diode D2 16, filter capacitor 5, commutation diode D3 17, decompression capacitor C1 10, external ac power source input end u _n13 flow out, and this process electric current is to decompression capacitor C1 10, filter capacitor 5, decompression capacitor C2 12 chargings.During second 1/4 cycle of negative half period, electric current is by external ac power source input end u _n13 flow into power circuit, through decompression capacitor C1 10, commutation diode D1 15, filter capacitor 5, commutation diode D4 18, decompression capacitor C2 12, ac power input end u _l14 flow out, and this process electric current is to decompression capacitor C1 10, decompression capacitor C2 12 electric discharges, to filter capacitor 5 chargings.No matter be positive half cycle or negative half period, always electric current hockets to decompression capacitor C1 10, discharging and recharging of decompression capacitor C2 12 both forward and reverse directions to filter capacitor 5 chargings.

As shown in Figure 3, in the gauge outfit control circuit, keyboard circuit 34 is electrically connected to the I/0 pin of single-chip microcomputer 36, the physical quantity that single-chip microcomputer collects testing circuit (as voltage, power, power factor, frequency etc.) converts digital quantity to, after computing, correction, through pulsewidth modulation (PWM) module, exports again.The output of the width modulation on single-chip microcomputer 36 (PWM) module is electrically connected to the input end of integrating circuit 37.

Described integrating circuit 37 comprises two integrating resistor R6 40, R7 41, an integrating capacitor C 42, two input ends of described integrating circuit connect respectively first integral resistance R 6 40 and second integral resistance R 7 41, first integral resistance R 6 40 is electrically connected to integrating capacitor C42 the first pin after being electrically connected to the output terminal of second integral resistance R 7 41, is electrically connected to the second pin of described integrating capacitor and power supply.

The PWM output of 8,2 tunnel of single-chip microcomputer 36 width modulations (PWM) module can form 16 D/A conversions, PWMO is as most-significant byte, PWM1 is as least-significant byte, and most-significant byte PWM output is electrically connected to first integral resistance R 6 40, and least-significant byte PWM output is electrically connected to second integral resistance R 7 41.

First integral resistance R 6 40 resistances during by pointer instrument gauge outfit full scale static current of lcd Is and single-chip microcomputer 36 operating voltage V determine:

$R\&ap;\frac{V}{I_S}$

Second integral resistance R 7 41 resistances are 2 of described first integral resistance R 6 40 resistances ⁸doubly.

Described keyboard circuit 34, for revising the non-linear of pointer instrument, patches it on circuit board during calibrated meter, calibrates complete taking off, and on-keyboard circuit while normally using can reduce cost and the volume of instrument.

Horizontal ordinate representative calibration signal source output signal in Fig. 5, instrument is for the measuring-signal of calibration; Become some equal minizones from 0 to instrument indication full scale interval division, as 10 minizones, from 0 to 10 these 11 data, 0 representation signal source output signal is the corresponding instrument full scale of 0,10 representation signal source output signal.Ordinate represents the amount of deflection of gauge pointer, 11 semaphores of corresponding horizontal ordinate input, the amount that ordinate presents should be linear with it, the angle of rotating due to pointer instrument gauge outfit 39 pointers and the electric current of input are non-linear, so should be calibrated by keyboard 34 on each input point, calibrator quantity deposits the EEPROM of single-chip microcomputer 36 in, according to 2 principles of determining a line, the continuous point of other of point-to-point transmission can think that in this interval be linear, can calculate the amount that should revise thus.

Embodiment 2

As shown in Figure 2, embodiment 2 and embodiment 1 difference are to detect the instrument of each parameter of three-phase alternating current, and feed circuit are three-phase alternating current, and with external ac power source input end u _a19, u _b20, u _c21 are electrically connected to, and rectification circuit 3 be three-phase commutation bridge, and three decompression capacitor C5 23, C6 25, C7 27 are arranged, and C5 23, C6 25, C7 27 electric capacitys are equal, and withstand voltage is far above power voltage line.

The power supply of the instrument that the power line parameters of three-phase four-wire system is detected can only be got energy from three live wires, and zero line does not connect, same three-phase three-wire system.Three-phase voltage u _a, u _b, u _cphase place with respect to the voltage of zero line differs successively

as shown in Figure 4, each moment three's algebraic sum is zero.The load of a, b, c three-phase can be similar to think only have C5 23, the capacitive reactance X of C6 25, C7 27 _ca, X _cb, X _cc.

The static current of lcd of instrument:

$I=\frac{U_a}{X_{\mathrm{ca}}}+\frac{U_b}{X_{\mathrm{cb}}}+\frac{U_c}{X_{\mathrm{cc}}}=\frac{U_a}{\frac{1}{\mathrm{\&omega;}{\mathrm{<figure-callout\; id="5"\; label="C"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">C</figure-callout>}}_5}}+\frac{{\mathrm{<figure-callout\; id="1"\; label="U\; b"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">U</figure-callout>}}_b}{\frac{1}{\mathrm{\&omega;}{\mathrm{<figure-callout\; id="6"\; label="C"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">C</figure-callout>}}_6}}+\frac{{\mathrm{<figure-callout\; id="1"\; label="U\; c"\; filenames="120119154827.png,120119154829.png"\; state="\{\{state\}\}">U</figure-callout>}}_c}{\frac{1}{\mathrm{\&omega;}{C}_7}}---\left(3\right)$

The electric capacity of decompression capacitor can be tried to achieve by (3) formula, ω=2 π f wherein, and the frequency that f is alternating current, as 50Hz, X _cabe the capacitive reactance of the first decompression capacitor C5 23, X _cbbe the capacitive reactance of the second decompression capacitor C6 25, X _ccbe the capacitive reactance of the 3rd decompression capacitor C7 27, the electric capacity C5 of the first decompression capacitor C5 23, the electric capacity C6 of the second decompression capacitor C6 25, the electric capacity C7 of the 3rd decompression capacitor C7 27, U _a, U _b, U _cfor outside electrical network phase voltage to be measured.

The static current of lcd of known instrument, can obtain according to above formula the electric capacity of decompression capacitor C5 23, decompression capacitor C6 25, decompression capacitor C7 27.Actual decompression capacitor C5 23, decompression capacitor C6 25, the comparable calculated value of decompression capacitor C7 27 electric capacity are slightly larger.Prevent voltage ripple of power network.Voltage stabilizing diode in holding circuit 4 is in order to prevent that voltage is higher and set; when voltage ripple of power network or instrument power consumption when on the low side; filter capacitor 5 both end voltage are during higher than the breakdown reverse voltage of the voltage stabilizing diode in holding circuit 4; voltage stabilizing diode reverse-conducting in holding circuit 4, protected subsequent conditioning circuit.Electric current, to filter capacitor 5 charging, converts the required power supply of instrument to through DC-DC voltage conversion circuit 6, for other partial circuits 8 of instrument as power supplies such as the single-chip microcomputer in the gauge outfit control circuit, testing circuits.

The foregoing is only preferred embodiment of the present invention, in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.

Claims (10)

1. a pointer instrument that adopts the capacitor step-down power supply, comprise capacity voltage dropping circuit, rectification circuit, holding circuit, filter capacitor, DC-DC voltage conversion circuit and power filtering capacitor, the gauge outfit control circuit comprises keyboard circuit, single-chip microcomputer, testing circuit, integrating circuit, current-limiting resistance and pointer instrument gauge outfit, it is characterized in that: the input end of described capacity voltage dropping circuit is electrically connected to external ac power source, the output terminal of described capacity voltage dropping circuit is electrically connected to the input end of rectification circuit, the output terminal of described rectification circuit is electrically connected to the input end of holding circuit, the output of described holding circuit is electrically connected to the input end of DC-DC voltage conversion circuit after filter capacitor, the output of DC-DC voltage conversion circuit again after power filtering capacitor as the output of power supply, in described gauge outfit control circuit, keyboard circuit is electrically connected to the single-chip microcomputer pin, the output of the pulse-width modulation PWM module on single-chip microcomputer is electrically connected to the input end of integrating circuit, the output terminal of integrating circuit is electrically connected to current-limiting resistance, and described current-limiting resistance and pointer instrument gauge outfit are connected in series,

Described capacity voltage dropping circuit comprises decompression capacitor, and the decompression capacitor of described capacity voltage dropping circuit comprises the first decompression capacitor, the second decompression capacitor, described the first decompression capacitor and ac power input end U _nbe electrically connected to described the second decompression capacitor and ac power input end U _lbe electrically connected to.

2. a kind of pointer instrument that adopts the capacitor step-down power supply according to claim 1, it is characterized in that: described decompression capacitor is in parallel with the resistance that resistance is more than or equal to 10 megaohms, and described resistance bleeds off the stored electric charge of electric capacity two-plate when having a power failure.

3. a kind of pointer instrument that adopts the capacitor step-down power supply according to claim 2, it is characterized in that: the electric capacity of described the first decompression capacitor and the second decompression capacitor equates, the capacitor value of decompression capacitor is determined by static current of lcd I and the line voltage V of instrument

When external ac power source is single-phase alternating current, the capacitive reactance of decompression capacitor is:

$X_C=\frac{V}{I}---\left(1\right),$

At this moment, the electric capacity of decompression capacitor can be tried to achieve by (2) formula:

$X_C=X_{C1}+X_{C2}=\frac{1}{{\mathrm{wC}}_1}+\frac{1}{{\mathrm{wC}}_2}---\left(2\right),$

W=2pf wherein, the frequency that f is alternating current, X _c1be the capacitive reactance of the first decompression capacitor, X _c2be the capacitive reactance of the second decompression capacitor, X _cit is the total capacitive reactance after two decompression capacitor series connection; C ₁be the electric capacity of the first decompression capacitor, C ₂it is the electric capacity of the second decompression capacitor;

When external ac power source is three-phase alternating current, described capacity voltage dropping circuit comprises the first decompression capacitor, the second decompression capacitor, the 3rd decompression capacitor, described the first decompression capacitor and ac power input end U _abe electrically connected to described the second decompression capacitor and ac power input end U _bbe electrically connected to described the 3rd decompression capacitor and ac power input end U _cbe electrically connected to, the electric capacity of described the first decompression capacitor, the second decompression capacitor and the 3rd decompression capacitor is equal, and the static current of lcd of instrument is:

$I=\frac{U_a}{X_{\mathrm{ca}}}+\frac{U_b}{X_{\mathrm{cb}}}+\frac{U_c}{X_{\mathrm{cc}}}=\frac{U_a}{\frac{1}{{\mathrm{wC}}_5}}+\frac{U_b}{\frac{1}{{\mathrm{wC}}_6}}+\frac{U_c}{\frac{1}{{\mathrm{wC}}_7}}---\left(3\right),$

At this moment, the electric capacity of decompression capacitor can be tried to achieve by (3) formula, w=2pf wherein, the frequency that f is alternating current, X _cabe the capacitive reactance of the first decompression capacitor, X _cbbe the capacitive reactance of the second decompression capacitor, X _ccbe the capacitive reactance of the 3rd decompression capacitor, the electric capacity that C5 is the first decompression capacitor, the electric capacity that C6 is the second decompression capacitor, the electric capacity that C7 is the 3rd decompression capacitor.

4. a kind of pointer instrument that adopts the capacitor step-down power supply according to claim 1; it is characterized in that: described holding circuit is voltage stabilizing diode; the negative pole of described voltage stabilizing diode is electrically connected to the output of the positive pole of rectifier bridge, and the positive pole of voltage stabilizing diode is electrically connected to the output of the negative pole of rectifier bridge.

5. a kind of pointer instrument that adopts the capacitor step-down power supply according to claim 4, it is characterized in that: described rectifier bridge is two phase commit bridge or three-phase commutation bridge.

6. according to the arbitrary described a kind of pointer instrument that adopts the capacitor step-down power supply of claim 1 to 5, it is characterized in that: the input voltage of described DC-DC voltage conversion circuit is greater than the instrument required voltage, and be up to 50V, the output voltage of DC-DC voltage conversion circuit is the instrument required voltage, is used to the power supplies such as single-chip microcomputer, testing circuit.

7. according to the arbitrary described a kind of pointer instrument that adopts the capacitor step-down power supply of claim 1 to 5, it is characterized in that: described gauge outfit control circuit also comprises testing circuit, for gathering voltage, power, power factor, the physical quantitys such as frequency, single-chip microcomputer converts the physical quantity collected to digital quantity and exports by the pulse-width modulation PWM module, pulse-width modulation PWM module in single-chip microcomputer is 8,2 tunnel PWM, its output forms 16 D/A conversions, described 16 D/A conversion is divided into most-significant byte and least-significant byte, described most-significant byte is output as PWM0, with first integral resistance, be electrically connected to, described least-significant byte is output as PWM1, with second integral resistance, be electrically connected to.

8. a kind of pointer instrument that adopts the capacitor step-down power supply according to claim 1, it is characterized in that: described integrating circuit comprises two integrating resistors, an integrating capacitor, two input ends of described integrating circuit connect respectively first integral resistance and second integral resistance, first integral resistance is electrically connected to integrating capacitor the first pin after being electrically connected to the output terminal of second integral resistance, is electrically connected to the second pin of described integrating capacitor and power supply.

9. a kind of pointer instrument that adopts the capacitor step-down power supply according to claim 8 is characterized in that: the calculating resistance of described first integral resistance is static current of lcd I during by pointer instrument gauge outfit full scale _swith single-chip microcomputer operating voltage V, determine:

$R>>\frac{V}{I_S}$

The calculating resistance of second integral resistance is 2 of described first integral resistance ⁸doubly, the actual resistance of first integral resistance and second integral resistance is less than calculated value, realizes the coupling of driving circuit and gauge outfit by the resistance of adjusting current-limiting resistance.

10. a kind of pointer instrument that adopts the capacitor step-down power supply according to claim 1, it is characterized in that: while utilizing described keyboard circuit correction pointer instrument non-linear, become some equal minizones by 0 to instrument indication full scale interval division, to each minizone, use respectively keyboard circuit input calibrator quantity, make the indication numerical value of pointer consistent with the value of standard signal source output, and calibrator quantity is deposited in to the EEPROM of single-chip microcomputer.

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