CN2725311Y - Variable frequency constant potentiometer - Google Patents

Abstract

The utility model belongs to a rectification equipment, in particular to a variable frequency constant potentiometer using a frequency changer to replace the transformer, the controllable silicon and the diode rectification in the main circuit, comprising a control system and a main circuit system. The control system comprises a stabilized voltage power supply and a comparator; the control system is used for collecting the set signal and the reference signal, compared with the set signal and the reference signal, and sending the compared result to the main circuit. The main circuit comprises an AC power supply (1), a first AC/DC conversion (2), a variable frequency oscillation inversion (3), an impulse-width modulation (4), a secondary AC/DC conversion (5), a DC/DC depressurizing system (6), a filtering (7) and a DC output (8). The variable frequency oscillation inversion (3) section is provided with a control circuit (9) and a factor correcting line (10). The impulse-width modulation (4) section is provided with a pressure regulation (11) and a protective line (12). The utility model is more stable and reliable; the ripple coefficient of the DC output is very small and can be ignored almost; the utility model is economized, light in weight and low in the equipment manufacturing cost.

Description

The frequency conversion potentiostat

Technical field

The utility model belongs to a kind of rectifying installation, particularly a kind of frequency conversion potentiostat that replaces transformer, silicon controlled rectifier, diode rectification in main power circuit with frequency transformer.

Background technology

Sell in the market and the main power circuit of normally used galvanic protection potentiostat all is to adopt high-power transformer, pass through behind the transformer, interchange is become direct current and form by silicon controlled rectifier and diode rectification.The weak point of this potentiostat, the one, when load hour, thyristor operating angle is very little, produces most advanced and sophisticated pulse, ripple factor is bigger; The 2nd, less stable; The 3rd, weight is big.

Summary of the invention

The purpose of this utility model is to overcome the deficiencies in the prior art part, and a kind of technical feature height, weight is clear, cost is low frequency conversion potentiostat are provided.

Technical solution of the present utility model is: a kind of frequency conversion potentiostat, comprise Controlling System and main circuit system, Controlling System is made up of voltage stabilized source and comparer, be used to gather given signal and reference signal, and it is compared, give main power circuit with comparative result, it is characterized in that main power circuit comprises AC power 1, an AC/DC conversion 2, oscillation inverter inversion 3, width modulation 4, secondary AC/DC conversion 5, DC/DC depressurizing system 6, filtering 7, direct current output 8.

Oscillation inverter inversion 3 parts are provided with pilot circuit 9 and factor correcting circuit 10.

Width modulation 4 parts are provided with voltage-regulation 11 and protection circuit 12.

The utility model is according to the inverter circuit principle, the switch power supply made from vibrator and frequency transformer etc., the main power circuit that has replaced traditional transformer, silicon controlled rectifier, diode to form, existing potentiostat has more complete characteristic, and its advantage mainly shows the following aspects:

1. the performance of whole plant is stable more, reliable;

2. the ripple factor of direct current output is very little, almost can ignore;

3. raise the efficiency, saves energy is more than 10%;

Weight with the potentiostat of power relatively, alleviate 50%;

5. equipment manufacturing cost reduces about 10%.

Description of drawings

Below in conjunction with the drawings and specific embodiments the utility model is elaborated.

Fig. 1 is a main power circuit flow diagram of the present utility model.

Fig. 2 is the main power circuit schematic diagram

Fig. 3 is APFC figure

Fig. 4 is the electrical schematic diagram of high power switching power supply control

Fig. 5 is holding circuit figure

Among Fig. 1: 1. AC power, a 2. AC/DC conversion, 3. oscillation inverter inversion, 4. width modulation, 5. secondary AC/DC conversion, 6.DC/DC depressurizing system, 7. filtering, 8. direct current output, 9. pilot circuit, 10. APFC, 11. voltage-regulation, 12. protection circuits.

Embodiment

As shown in Figure 1, the utility model circuit comprises AC power 1, an AC/DC conversion 2, oscillation inverter inversion 3, width modulation 4, secondary AC/DC conversion 5, DC/DC depressurizing system 6, filtering 7, direct current output 8.This is the main power circuit of total system, and an AC/DC conversion 2 is cores of this frequency transformer.In order to realize the safe reliable of total system, the important step oscillation inverter inversion 3 of system is provided with pilot circuit 9 and factor correcting circuit 10, these two portions are effectively to produce HF oscillation and inversion in order to guarantee.Width modulation 4 parts are provided with and protection circuit 12, and voltage-regulation 11 is to be the set circuit of assurance width modulation size, and protection circuit 12 is to prevent that whole frequency transformer from damaging, and emphasis is the protection width modulation.

When this device and potentiostat pilot circuit linked, device started.220VDC voltage is through AC/DC conversion 2 conversions, produce inverter voltage by HF oscillation inversion 3, again after pulse-width regulated is carried out in pulsewidth modulation 4, carry out secondary AC/DC conversion 5 conversions, the dc voltage that conversion is come out is depressured to required voltage through DC/DC depressurizing system 6, and this voltage is directly delivered to direct current output 8 through filtering 7.

The utility model frequency conversion potentiostat has adopted Active Power Factor Correction Technology to realize the High Power Factor of system.The DC/DC main power circuit adopts half-bridge converter and a kind of new IGBT of current mode PWM chip VC3846 control to drive electrical control system.

The utility model has adopted twice conversion scheme of AC/DC/AC/DC.Volts DS after the rectification through the APFC link to improve the power factor of system, again after the inversion of semi-bridge alternation circuit, by the high-frequency transformer isolated buck, last rectification output dc voltage.The key link of system has DC/AC circuit power factor correcting circuit, pwm control circuit, voltage-regulation and holding circuit etc., is described below respectively.

1) main circuit system

V1, V2, C3, C4 and high-frequency transformer T1 form semibridge system AC/DC translation circuit among Fig. 2, and IGBT adopts the 8KM75GB123D module, and operating frequency fixes on 30KHz.High-frequency transformer adopts the EE85B magnetic core, adopts the coiling of syllogic method, to reduce leakage inductance.Commutation diode adopts fast diode, and reducing the influence of its reverse recovery time to output, R1, C1, R2, C2 be and at the absorption circuit at IGBT two ends, R3 and R4 play assurance capacitor C 3 and the C4 dividing potential drop acts on uniformly.CT is that primary current detects mutual inductor, and the current sampling during as current control is used.In order to prevent that power supply from producing the DC component that magnetic bias is directly proportional with imbalance weber value in 5 blocking-up of former limit windings in series capacitor C in operational process, each unequal weber is worth behind the balance cock, C5 adopts the noninductive electric capacity of CBB, transformer secondary and D1, D2 adopt full-wave rectification to add the two poles of the earth C-C filtering to satisfy the requirement of output ripple and low, and resistance R 7 and R8 are output voltage feedback sample resistance.

2) APFC system

The power factor of total system requires more than 0.9, adopts the VC3854 control chip to form power factor circuit for this reason.This control chip adopts Average Current Control, and power factor limits power network current distortion≤3% near 1.0, and Fig. 3 is the APFC by VC3854 control.

This circuit is made up of two portions, and VC3854 and peripheral component constitute the control that control section is realized two net side received currents and output voltage.Power section constitutes the Boost boost-up circuit by components and parts such as L2, and switching tube V selects the 8KM75GB123D module, and its operating frequency is selected in 35KHz, inductance L 2 adopt four 450V/470 μ F for 2mH/20 C5 chemical capacitor parallel connection.The pfc circuit of design mainly is to be used in the high power D C/DC circuit.So do not carry out power factor correction when load is light, circuit of power factor correction comes into operation automatically when load is big, and part control is partly realized by the comparer among Fig. 3.R10, R11 are load detection resistance, and by comparer, making its output terminal is lower level when load increases, and the D2 conducting blocks VC3854 for ENA (10 pin) lower level.ENA is that high level just allows VC3854 work when load is big, D3 receives SS (13 pin) soft start end, to make SS be lower level in the D3 conducting when load is light, and when load increases when requiring VC3854 work, the SS terminal potential is slowly opened control output pulse from zero and realized soft start with sky than slowly increasing.

3) pilot circuit system

The PWM of system partly adopts current control chip Vc3846 to form the fluctuation Waveform generating circuit, and Fig. 4 is the electrical schematic diagram of the PWM control of high power switching power supply.

R1 and C2 form the vibrator of Vc3846, and oscillation frequency is $f=\frac{2.2}{R1C1}$ In order to prevent the threeway of two switching tubes, set " Dead Time " that two-way output is all turn-offed, determined by the decline of electricoscillation zigzag wave, compensate as the ripple of adopting of current control to 4 pin SEV1 through R2 and C1 from 8 pin, to prevent harmonic oscillation effectively.The main power circuit signal is through current transformer CT, behind bridge rectifier and the capacitance-resistance filter as the current feedback signal of VC3846, VC3846 is to the output voltage pulse and the maximum current limit value of current amplifier, (output voltage by voltage and voltage error amplifier is determined) one by one compares, when the pulse switch electric current surpasses maximum current limit, VC3846 will block the output pulse, limited the maximum output current in switch circuit source, C5 is for realizing the electric capacity of soft start, the 1 pin current potential of VC3846 does not have pulsewidth output when being lower than 0.5V, connect electric capacity to ground at 1 pin, there is pulsewidth output the start back when being higher than 0.5V along with electric capacity charging capacitor voltage, and, finish soft start function along with the rising pulse of capacitance voltage broadens gradually.

The driving circuit that Fig. 4 adopted has the switching frequency height, driving power is big, simple in structure, have the advantages that negative pressure is turn-offed, V1～V4, D2～D5 have constituted the pulse transformer driving circuit, are applicable to drive powerful IGBT, and D1 and D6 help the shutoff of V1～V4.When Pwm1 is a high level, during the lower level of Pwm2 limit, V1 and V4 conducting; When Pwm1 and Pwm2 are lower level, in the transformer since partially sense store energy carry out afterflow by D5 and D4, make A1 point potential drop to-0.7V, though at this moment Pwm1 is a lower level, but V1 is conducting once more, then V1 be in the high frequency on off state and easily burn Pwm2 by high level to low transition.There is kindred circumstances in V2, add D6 can make afterflow the time A point control of Electric potentials at OV, thereby the shutoff of favourable V1 or V2.The effect of D1 in like manner is the shutoff that is beneficial to V3 or V4.

4) design of holding circuit

Fig. 5 is the holding circuit of system.Mainly be that control VC3846 stops half-bridge converter work.VC3846 16 pin SHDTDW are for turn-offing control pin, when V1 or V2 conducting occurring/do not make during under-voltage or overcurrent, D1 or D2 conducting, then 16 pin are the report V1 ground connection of the high level 1 pin warp that makes VC3846, when took place/when under-voltage the D1 conducting to make 16 pin be high level, when VC3846 turn-offed, the V1 conducting made the thyristor short circuit that inner 16 pin of VC3846 are connect it bear negative pressure and turn-offs.After mistake/under-voltage releasing, VC3846 can export pulse again can work umformer like this.And VC3846 blocks the output pulse at overcurrent, when overload situations occurs, and pulse can not recover when blocking releasing.

Claims (3)

1, a kind of frequency conversion potentiostat, comprise Controlling System and main circuit system, Controlling System is made up of voltage stabilized source and comparer, be used to gather given signal and reference signal, and it is compared, give main power circuit with comparative result, it is characterized in that main power circuit comprises AC power (1), AC/DC conversion (2), an oscillation inverter inversion (3), width modulation (4), secondary AC/DC conversion (5), DC/DC depressurizing system (6), filtering (7), direct current output (8).

2, frequency conversion potentiostat according to claim 1 is characterized in that oscillation inverter inversion (3) part is provided with pilot circuit (9) and factor correcting circuit (10).

3, frequency conversion potentiostat according to claim 1 and 2 is characterized in that width modulation (4) part is provided with voltage-regulation (11) and protection circuit (12).