CN202395670U

CN202395670U - High-low frequency AC (alternating current)/DC (direct current) switching circuit

Info

Publication number: CN202395670U
Application number: CN201120485213XU
Authority: CN
Inventors: 何曙光
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-11-28
Filing date: 2011-11-28
Publication date: 2012-08-22
Anticipated expiration: 2021-11-28

Abstract

The utility model discloses an AC (alternating current)/DC (direct current) switching circuit for capable of adapting to high frequency, low frequency and high-low frequency modulation input. The AC/DC switching circuit provided by the utility model is characterized in that two diodes of adjacent bridge arms are respectively connected in parallel with two elements, namely an inductor and a capacitor which are connected in series on the basis of the traditional full wave bridge rectifier circuit. The AC/DC switching circuit provided by the utility model can efficiently converting various AC inputs of various wave forms into DC, and comprises a DC input; and the AC/DC switching circuit is suitable for output characteristic of different power sources and power source adapters. The switching circuit can provide high-efficiency and large-power follow-up applications such as various functional circuits and LED (light-emitting diode) constant-current sources, as well as the application occasions requiring for compatibility and adaptation of various power sources and power source adapters.

Description

A kind of high and low frequency AC/DC change-over circuit

Technical field

The utility model is a high and low frequency AC/DC change-over circuit, belongs to power technique fields, is widely used in the AC/DC conversion.So-called AC/DC conversion is that the alternating current (AC) (containing direct current) with various wave modes and classification converts direct current (DC) into, and this circuit is formed AC/DC supply convertor product as the input transducer of DC/DC converter with follow-up DC/DC translation circuit jointly.The DC/DC converter can be boost type, step-down type or other type, and this DC/DC supply convertor is mainly used in various functional circuits and LED light fixture constant-current source driven product.

Background technology

A lot of electronic products need low-voltage DC supply, and power demand number watt does not wait to tens of watts.Low-voltage DC potential source source is varied, useful Industrial Frequency Transformer step-down rectifier, the output rectification of useful electronic transformer obtains low-voltage DC, also has directly with DC power supply.Though all be low-voltage DC, their load characteristic difference is very big.The low-voltage DC that for example obtains with the Industrial Frequency Transformer step-down rectifier, it is no problem to light the LED light fixture, and it is also no problem directly to light halogen quartz lamp with electronic transformer.And with after the electronic transformer rectification to low-voltage DC, but do not work LED light fixture or the phenomenon that the LED flicker does not stop takes place of appearance point, this is the generation because the output characteristic of load characteristic and power supply does not match.For example: electronic transformer be input as the 220V electric main, be output as the low pressure high-frequency alternating current, frequency is about 30KHz～50KHz, is a kind of Switching Power Supply, circuit is the half-bridge topology form.Because the electronic transformer volume is little, in light weight,, save copper material without silicon steel sheet; Cost is low; In being output as several watts to tens of watts power brackets, replaced Industrial Frequency Transformer basically, a lot of LED light fixtures must adopt the electronic transformer supply power mode; To substitute halogen quartz lamp, because halogen quartz lamp adopts the electronic transformer supply power mode always.But the low pressure high-frequency alternating current of electronic transformer output is through over commutation, the basic point that the has LED light fixture that do not work, the LED flicker that makes that has does not stop, though also have can light the LED light fixture, luminous faint output not power.So, alternative halogen quartz lamp runs into technical barrier, promotes the LED light fixture and is restricted, and is unfavorable for energy-conserving and environment-protective.

Summary of the invention

To the halogen quartz lamp design, the halogen quartz lamp power consumption is many originally for electronic transformer, and power reaches tens watts; Its internal feedback governing loop also is to design greatly according to power consumption, and halogen quartz lamp is ohmic, as osram lamp; The cold conditions internal resistance is low; Do not mind that power supply is to exchange or direct current, be lower than rated voltage and can light yet that the light that only sends is dark; And the power of LED light fixture is much little, has only several watts usually, and for example the LED lamp power of MR16 shell has only 1～3W, and also necessary direct current supply is lower than the rated voltage absolute point and does not work.

The producer that produces electronic transformer is for practicing thrift cost, pursuing High Power Factor; Filter capacitor value to behind the commercial power rectification is very little, is approximately 0.1～0.47 μ F, and filter effect is very poor; Cause the output of electronic transformer to have the envelope of civil power 50Hz frequency; Envelope still exists after the rectification, and its frequency has become 100Hz, and is shown in Figure 4 like accompanying drawing.Moreover, the unloaded output voltage virtual height of electronic transformer, behind the bringing onto load output voltage fall fairly obvious, the power supply classification of Here it is low frequency modulations high frequency.

It seems that from Fig. 4 the output voltage instantaneous value u of electronic transformer is to be lower than the rated value U that lights LED light fixture voltage in some time period, adds the loss of rectification, the voltage that obtains is lower.That is to say that voltage is low to be main cause.

How to improve voltage? The utility model is transformed the conventional bridge rectification circuit; The series circuit of all parallelly connected last inductance of two rectifier diodes (L) of adjacent brachium pontis, electric capacity (C); That kind as Fig. 1 of Figure of description representes is transformed into similar full wave bridge type voltage multiplying rectifier to traditional full-wave bridge rectifier, and this several elements have been arranged; It has carried out energy storage to the HFS in the electronic transformer output, and makes the normally bridge-type conversion of low frequency envelope.Have only a diode in its loop, starting characteristic is good, can reduce dead band, loop voltage, reduces resistance, near the incandescent lamp characteristic, has received good effect.As long as this electronic transformer can be lighted halogen quartz lamp, just can light the LED light fixture, and the LED scintillation no longer takes place; Can obtain enough power outputs from electronic transformer, can light a plurality of LED light fixtures, the efficient of circuit is high, and is identical with classical circuit; The element that circuit increases is few, with low cost.

Description of drawings

Fig. 1 is the utility model AC/DC change-over circuit;

Fig. 2, Fig. 3 are other two kinds of forms of the utility model circuit.

Fig. 4 is the oscillogram after electronic transformer adopts the conventional bridge rectification, and wherein u is the instantaneous value of output voltage, and U is a rated value of lighting LED light fixture voltage.

Embodiment

Come the technical characterictic of figures and explanation the utility model below in conjunction with embodiment.

Fig. 1 is embodiment of the utility model AC/DC change-over circuit.Wherein, after inductance L 1 was connected with capacitor C 1, VD1 was in parallel with diode, and after inductance L 3 was connected with capacitor C 3, VD3 was in parallel with diode, and C5 is the filter capacitor after the rectification, R _LIt is load; INa and INb are two inputs, connect the output of electronic transformer.

If this circuit removes L1, L3, C1, four elements of C3; Just become traditional full-wave bridge rectifier circuit, four diode VD1～VD4 claim that traditionally each diode is " brachium pontis "; With regard to Fig. 1; Wherein VD1 and VD2 are in first half custom and are called " going up brachium pontis ", and VD3 and VD4 are in the Lower Half custom and are called " following brachium pontis ", and two diodes have the custom of common tie point to be called " adjacent brachium pontis "; For example VD1 and VD3, VD1 and VD2, VD2 and VD4, VD4 and VD3 have common tie point, all are called " adjacent brachium pontis ".The similar full wave bridge type two voltage doubling rectifying circuit of the utility model effect, be exactly on brachium pontis VD1 and VD3 the parallel connection LC series element, its principle Analysis is following:

When INa end for just, in the half period, the electric current one side is by INa → VD1 → R when negative for the INb end _L→ VD4 → INb is to load R _LPower supply is charged to capacitor C 3 by INa → L3 → C3 → VD4 → INb approach on the other hand, and the voltage of charging back C3 is near the peak value of input terminal voltage.

Hold in the half period in correct time for negative, INb when the INa end, the voltage on the capacitor C 3 is superimposed upon on the input terminal voltage, and maximum is near the twice of the peak value of input terminal voltage, and electric current is on the one hand by INb → VD2 → R _L→ VD3 → INa is to load R _LPower supply, load R _LOn voltage near the twice of input terminal voltage; Charged to capacitor C 1 by INb → VD2 → L1 → C1 → INa approach on the other hand, the voltage on the C1 of charging back is near the peak value of input terminal voltage.

Be recycled to INa end for just, INb end half period when negative, capacitor C 1 has been filled electricity with at this moment, is superimposed upon on the input terminal voltage, is equivalent to the twice input terminal voltage to load R _LSupplied power.

Operating state so circulation is gone down, and this has just solved this special out-put supply application problem of low frequency modulations high frequency.The efficient of surveying this circuit is high, and is identical with classical circuit; An electronic transformer can be exported its rated power supply load, and the power output of electronic transformer is fully used.

Inductance L 1 in this circuit, L3; Play the effect of limiting capacitance C1, C3 charging current climbing; Reduced impulse current to C1, C3; In the useful life of favourable prolongation capacitor C 1, C3, the transient current that has also limited electronic transformer output simultaneously is excessive, meets the supplied character of electronic transformer more.Facts have proved and remove inductance L 1, L3, the circuit cisco unity malfunction.

Fig. 2, Fig. 3 are other two kinds of forms of the utility model AC/DC change-over circuit, Fig. 2 circuit be in parallel connection on the last brachium pontis diode VD1 inductance L 1 after being in series with capacitor C 1 two elements and on the brachium pontis diode VD2 parallel connection two elements of inductance L 2 after being in series with capacitor C 2.Fig. 3 circuit be on following brachium pontis diode VD3 parallel connection inductance L 3 after being in series with capacitor C 3 two elements and down on the brachium pontis diode VD4 parallel connection two elements of inductance L 4 after being in series with capacitor C 4.

Following to Fig. 2 circuit analysis:

When INa end for just, in the half period, the electric current one side is by INa → VD1 → R when negative for the INb end _L→ VD4 → INb is to load R _LPower supply is charged to capacitor C 2 by INa → VD1 → L2 → C2 → INb approach on the other hand, and the voltage of charging back C2 is near the peak value of input terminal voltage.

Hold in the half period in correct time for negative, INb when the INa end, the voltage on the capacitor C 2 is superimposed upon on the input terminal voltage, and maximum is near the twice of the peak value of input terminal voltage, and electric current is on the one hand by INb → VD2 → R _L→ VD3 → INa is to load R _LPower supply, load R _LOn voltage near the twice of input terminal voltage; Charged to capacitor C 1 by INb → VD2 → L1 → C1 → INa approach on the other hand, the voltage on the C1 of charging back is near the peak value of input terminal voltage.

Following to Fig. 3 circuit analysis:

Hold in the half period in correct time for negative, INb when the INa end, the voltage on the capacitor C 3 is superimposed upon on the input terminal voltage, and maximum is near the twice of the peak value of input terminal voltage, and electric current is on the one hand by INb → VD2 → R _L→ VD3 → INa is to load R _LPower supply, load R _LOn voltage near the twice of input terminal voltage; Charged to capacitor C 4 by INb → L4 → C4 → VD3 → INa approach on the other hand, the voltage on the C4 of charging back is near the peak value of input terminal voltage.

Be recycled to INa end for just, INb end half period when negative, capacitor C 4 has been filled electricity with at this moment, is superimposed upon on the input terminal voltage, is equivalent to the twice input terminal voltage to load R _LSupplied power.

Fig. 1, Fig. 2, Fig. 3 are the forms of AC/DC change-over circuit, and their common features are: after L, the C element connected in series, be connected in parallel on two diodes of adjacent brachium pontis.

In sum, the characteristic of the utility model is: the AC/DC change-over circuit, on the basis of traditional full-wave bridge rectifier circuit, on two diodes of adjacent brachium pontis respectively parallel connection inductance and electric capacity two elements after being in series.

Claims

1. high and low frequency AC/DC change-over circuit is characterized in that: on the basis of traditional full-wave bridge rectifier circuit, on two diodes of adjacent brachium pontis respectively parallel connection inductance and electric capacity two elements after being in series.