The utility model content
The technical problems to be solved in the utility model is, and is very low at the power factor of the constant-current drive circuit of prior art, increased the loss of electrical network and the defective of burden, provides a kind of power factor the higher constant-current drive circuit with power factor correction.
The technical scheme that its technical problem that solves the utility model adopts is: construct a kind of constant-current drive circuit with power factor correction, comprising the circuit of power factor correction of the waveform correction power factor of passing through the adjustment average current input, described circuit of power factor correction comprises: the switching circuit of adjusting the waveform of described average current input, control the control chip of the switching frequency of described switching circuit, supply with the start-up circuit of described control chip starting resistor, supply with the holding circuit of described control chip operating voltage, gather the input voltage feedback circuit of input voltage, gather the output voltage feedback circuit of output voltage, and the current foldback circuit that detects the electric current that passes through described switching circuit; Described switching circuit is connected with input, described output voltage feedback circuit and the described control chip of the constant-current drive circuit of described power factor correction respectively; Described start-up circuit is connected with the input and the described control chip of the constant-current drive circuit of described power factor correction respectively; Described holding circuit is connected with the input and the described control chip of the constant-current drive circuit of described power factor correction respectively; Described input voltage feedback circuit is connected with the input and the described control chip of the constant-current drive circuit of described power factor correction respectively; Described overcurrent protection electric current is connected with described switching circuit and described control chip respectively; Described output voltage feedback circuit is connected with the output of the constant-current drive circuit of described switching circuit, described control chip and described power factor correction respectively.
In the constant-current drive circuit with power factor correction described in the utility model, described switching circuit comprises transformer T1, switching tube Q2 and diode D5, the control end of described switching tube Q2 is connected with the pin GD of described control chip, the input of described switching tube Q2 is connected with the output of the main coil of described transformer T1 and the positive pole of described diode D5 respectively, the negative pole of described diode D5 is connected with the output of the constant-current drive circuit of described power factor correction, the output head grounding of described switching tube Q2, the input of the main coil of described transformer T1 is connected with the input of the constant-current drive circuit of described power factor correction.
In the constant-current drive circuit with power factor correction described in the utility model, described start-up circuit comprises resistance R 3, and described input with constant-current drive circuit of power factor correction is connected with the pin VCC of described control chip by described resistance R 3.
In the constant-current drive circuit with power factor correction described in the utility model, described holding circuit comprises the AC/DC change-over circuit, described AC/DC change-over circuit comprises resistance R 6, capacitor C 3, diode D3, diode D2 and capacitor C 2, one end of described resistance R 6 is by the inferior coil ground connection of described transformer T1, the other end of described resistance R 6 is connected with the negative pole of described diode D3 by described capacitor C 3, the plus earth of described diode D3, the positive pole of described diode D2 is connected with the negative pole of described diode D3, the negative pole of described diode D2 is by described capacitor C 2 ground connection, and the input of the main coil of the earth terminal of the inferior coil of described transformer T1 and described transformer T1 is an end of the same name.
In the constant-current drive circuit with power factor correction described in the utility model, described holding circuit also comprises linear voltage-stabilizing circuit, described linear voltage-stabilizing circuit comprises voltage-stabiliser tube ZD2, triode Q1, diode D1, capacitor C 9 and voltage-stabiliser tube ZD1, the collector electrode of described triode Q1 is connected with the negative pole of described diode D2, the base stage of described triode Q1 is connected with the negative pole of described voltage-stabiliser tube ZD2, the plus earth of described voltage-stabiliser tube ZD2, the emitter of described triode Q1 is connected with the positive pole of described diode D1, the negative pole of described diode D1 is connected with the pin VCC of described control chip, one end of described capacitor C 9 is connected with the negative pole of described voltage-stabiliser tube ZD1, the positive pole of the other end of described capacitor C 9 and described voltage-stabiliser tube ZD1 interconnects, the negative pole of described voltage-stabiliser tube ZD1 is connected the plus earth of described voltage-stabiliser tube ZD1 with the pin VCC of described control chip.
In the constant-current drive circuit with power factor correction described in the utility model, described input voltage feedback circuit comprises resistance R 1, resistance R 10 and capacitor C 5, the pin MU of one end of described resistance R 10, an end of described capacitor C 5 and described control chip interconnects, the other end of the other end of described resistance R 10 and described capacitor C 5 is ground connection simultaneously, and the pin MU of described control chip is connected with described input with constant-current drive circuit of power factor correction by described resistance R 1.
In the constant-current drive circuit with power factor correction described in the utility model, described output voltage feedback circuit comprises resistance R 8, resistance R 17 and capacitor C 7, one end of described resistance R 8 is connected with described output with constant-current drive circuit of power factor correction, the other end of described resistance R 8 is connected with an end of described resistance R 17, the other end ground connection of described resistance R 17, one end of described resistance R 17 is connected with the pin INV of described control chip and an end of described capacitor C 7 respectively simultaneously, and the other end of described capacitor C 7 is connected with the pin COMP of described control chip.
In the constant-current drive circuit with power factor correction described in the utility model; described current foldback circuit comprises capacitor C 8, resistance R 13 and resistance R 16; described resistance R 16 1 ends are connected with an end of resistance R 13 and the output of described switching tube Q2 respectively; the other end ground connection of described resistance R 16; the other end of described resistance R 13 is connected with an end of described capacitor C 8 and the pin CS of described control chip respectively, the other end ground connection of described capacitor C 8.
In the constant-current drive circuit with power factor correction described in the utility model, described constant-current drive circuit with power factor correction also comprises the diode D4 of the output of the output that is used to connect described constant-current drive circuit with power factor correction and described constant-current drive circuit with power factor correction.
In the constant-current drive circuit with power factor correction described in the utility model, described constant-current drive circuit with power factor correction also comprises and is used to prevent that circuit from opening, closing or the thermistor NTC1 of the surge current during short circuit, the end of described thermistor NTC1 is connected with the negative pole of described diode D5, and the other end of described thermistor NTC1 is connected with described output with constant-current drive circuit of power factor correction.
Implement the constant-current drive circuit with power factor correction of the present utility model, has following beneficial effect: because this constant-current drive circuit has adopted circuit of power factor correction to adjust the waveform of average current input, make that this constant-current drive circuit power factor is higher, reduced loss and pollution electrical network.
The waveform of average current input is adjusted in control by switching circuit, and is simple and convenient.Start-up circuit start-up control chip is started working.AC/DC change-over circuit and linear voltage-stabilizing circuit will offer the stable operating voltage of control chip.The stability of the output voltage that the output voltage feedback circuit guarantees.The input voltage feedback circuit has guaranteed the waveform consistency of average output current and input voltage.Current foldback circuit can prevent effectively that the electric current of switching tube Q2 is excessive.Diode D4 can so that input voltage directly export without circuit of power factor correction.Thermistor NTC1 can effectively suppress circuit and open, closes or the surge current during short circuit.
Embodiment
In order to make the purpose of this utility model, technical scheme and advantage clearer,, the utility model is further elaborated below in conjunction with drawings and Examples.Should be appreciated that specific embodiment described herein only in order to explanation the utility model, and be not used in qualification the utility model.
In the structural representation of the preferred embodiment of constant-current drive circuit with power factor correction of the present utility model shown in Figure 1; described constant-current drive circuit with power factor correction comprises that circuit of power factor correction comprises switching circuit 1, control chip 2, start-up circuit 3, holding circuit 4, input voltage feedback circuit 5, output voltage feedback circuit 6 and current foldback circuit 7 by the circuit of power factor correction of the waveform correction power factor of adjusting average current input.Switching circuit 1 is used to adjust the waveform of average current input; control chip 2 is used for the switching frequency of control switch circuit 1; start-up circuit 3 is used to supply with control chip 2 starting resistors; holding circuit 4 is used to supply with control chip 2 operating voltages; input voltage feedback circuit 5 is used to gather input voltage; output voltage feedback circuit 6 is used to gather output voltage, and current foldback circuit 7 is used to detect the electric current by switching circuit 1.Switching circuit 1 is connected with the output and the control chip 2 of the constant-current drive circuit of the input of the constant-current drive circuit of power factor correction, power factor correction respectively; Start-up circuit 3 is connected with the input and the control chip 2 of the constant-current drive circuit of power factor correction respectively; Holding circuit 4 is connected with the input and the control chip 2 of the constant-current drive circuit of power factor correction respectively; Input voltage feedback circuit 5 is connected with the input and the control chip 2 of the constant-current drive circuit of power factor correction respectively; The overcurrent protection electric current is connected with switching circuit 1 and control chip 2 respectively; Output voltage feedback circuit 6 is connected with the output of the constant-current drive circuit of switching circuit 1, control chip 2 and power factor correction respectively.When the constant-current drive circuit with power factor correction of the present utility model is worked, by switching circuit 1, control chip 2, start-up circuit 3, holding circuit 4 constitutes the main circuit of constant-current drive circuit, behind start-up circuit 3 start-up control chips 2, stable operating voltage is provided for control chip 2 by holding circuit 4, this circuit of power factor correction adopts the current feedback technology, constitute sample circuit by input voltage feedback circuit 5, adopt the input half-wave voltage signal be input to control chip 2, control chip 2 is received behind this voltage signal the duty ratio of switching tube Q2 in the control switch circuit 1, make that the half-wave voltage signal of average current input and input is synchronous, thereby reduced harmonic wave, increased the power factor of constant-current drive circuit.The voltage of the output of output voltage feedback circuit 6 sampling constant-current drive circuits is to adjust the output voltage values of constant-current drive circuit simultaneously.The electric current of current foldback circuit 7 sense switch circuit 1 when the electric current of the switching tube Q2 that flows through switching circuit 1 is excessive, can pass through control chip 2 off switch circuit 1, to play the effect of protection switch pipe Q2 and other elements of circuit.
In the circuit diagram of the preferred embodiment of constant-current drive circuit with power factor correction of the present utility model shown in Figure 2, switching circuit 1 comprises transformer T1, switching tube Q2 and diode D5, the control end of switching tube Q2 is connected with the pin GD of control chip 2, the input of switching tube Q2 is connected with the output of the main coil of transformer T1 and the positive pole of diode D5 respectively, the negative pole of diode D5 is connected with the output of the constant-current drive circuit of power factor correction, the output head grounding of switching tube Q2, the input of the main coil of transformer T1 is connected with the input of the constant-current drive circuit of described power factor correction.Start-up circuit 3 comprises resistance R 3, and the input with constant-current drive circuit of power factor correction is connected with the pin VCC of control chip 2 by resistance R 3.Holding circuit 4 comprises AC/DC change-over circuit and linear voltage-stabilizing circuit, the AC/DC change-over circuit comprises resistance R 6, capacitor C 3, diode D3, diode D2 and capacitor C 2, one end of resistance R 6 is by the inferior coil ground connection of transformer T1, the other end of resistance R 6 is connected with the negative pole of diode D3 by capacitor C 3, the plus earth of diode D3, the positive pole of diode D2 is connected with the negative pole of diode D3, the negative pole of diode D2 is by capacitor C 2 ground connection, and the input of the main coil of the earth terminal of the inferior coil of transformer T1 and transformer T1 is an end of the same name.Linear voltage-stabilizing circuit comprises voltage-stabiliser tube ZD2, triode Q1, diode D1, capacitor C 9 and voltage-stabiliser tube ZD1, the collector electrode of triode Q1 is connected with the negative pole of diode D2, the base stage of triode Q1 is connected with the negative pole of voltage-stabiliser tube ZD2, the plus earth of voltage-stabiliser tube ZD2, the emitter of triode Q1 is connected with the positive pole of diode D1, the negative pole of diode D1 is connected with the pin VCC of control chip 2, one end of capacitor C 9 is connected with the negative pole of voltage-stabiliser tube ZD1, the positive pole of the other end of capacitor C 9 and voltage-stabiliser tube ZD1 interconnects, the negative pole of voltage-stabiliser tube ZD1 is connected the plus earth of voltage-stabiliser tube ZD1 with the pin VCC of control chip 2.When originally having the constant-current drive circuit use of power factor correction, starting resistor is provided for control chip 2 by start-up circuit 3 by the input of constant-current drive circuit, prevents that certain resistive short from causing the damage of control chip 2 for the resistance R 3 a plurality of resistance of series connection (R4, R11).After control chip 2 started, control chip 2 sent the switching frequency of pwm signal control switch pipe Q2 to reach the purpose of the waveform of controlling average output current by pin GD.Simultaneously holding circuit 4 can offer the follow-up stable operating voltage of control chip 2, and when switching tube Q2 opened, transformer T1 conducting capacitor C 3 was charged by inferior coil, the resistance R 6 of diode D3, transformer T1; When switching tube Q2 closed, capacitor C 3 was by inferior coil, resistance R 6 discharges of diode D2, capacitor C 2, transformer T1, and the alternating current that inferior coil of transformer T1 is produced is converted to direct voltage and powers to control chip 2.Simultaneously linear voltage-stabilizing circuit forms galvanic current by capacitor C 9 and voltage-stabiliser tube ZD1 at the pin VCC of control chip 2 end and presses, and makes the work that control chip 2 can continue.The waveform of average current input is adjusted in control by switching circuit 1, and is simple and convenient.Start-up circuit 3 start-up control chips 2 are started working.AC/DC change-over circuit and linear voltage-stabilizing circuit will offer the stable operating voltage of control chip 2.
In the circuit diagram of the preferred embodiment of constant-current drive circuit with power factor correction of the present utility model shown in Figure 2, input voltage feedback circuit 5 comprises resistance R 1, resistance R 10 and capacitor C 5, the pin MU of one end of resistance R 10, an end of capacitor C 5 and control chip 2 interconnects, the other end of resistance R 10 is stated the other end while ground connection of capacitor C 5, and the pin MU of control chip 2 is connected by the input of resistance R 1 with the constant-current drive circuit with power factor correction.Input voltage feedback circuit 5 sends to control chip 2 with the waveform of input voltage, so that the waveform of average output current and input voltage is consistent.Certainly the influence that a plurality of resistance (R2) of also can connecting with resistance R 1 prevent that resistance R 1 short circuit from causing control chip 2, shunt capacitance C5 can well switch noise inhibiting.
In the circuit diagram of the preferred embodiment of constant-current drive circuit with power factor correction of the present utility model shown in Figure 2, output voltage feedback circuit 6 comprises resistance R 8, resistance R 17 and capacitor C 7, one end of resistance R 8 is connected with the output of the constant-current drive circuit with power factor correction, the other end of resistance R 8 is connected with an end of resistance R 17, the other end ground connection of resistance R 17, one end of resistance R 17 is connected with the pin INV of control chip 2 and an end of capacitor C 7 respectively simultaneously, and the other end of capacitor C 7 is connected with the pin COM of control chip 2.Can sample the voltage of output of constant-current drive circuit to adjust the output voltage values of constant-current drive circuit, the stability of the output voltage of assurance by between the pin INV of control chip 2 and pin COM, adding output voltage feedback circuit 6, making.Certainly sampling resistor can adopt the connection in series-parallel of multiple resistance to realize (as R9, R18, R17).
In the circuit diagram of the preferred embodiment of constant-current drive circuit with power factor correction of the present utility model shown in Figure 2; current foldback circuit 7 comprises capacitor C 8, resistance R 13 and resistance R 16; resistance R 16 1 ends are connected with an end of resistance R 13 and the output of switching tube Q2 respectively; the other end ground connection of resistance R 16; the other end of resistance R 13 is connected the other end ground connection of capacitor C 8 with an end of capacitor C 8 and the pin CS of control chip 2 respectively.The electric current of current foldback circuit 7 sense switch circuit 1 when the electric current of the switching tube Q2 that flows through switching circuit 1 is excessive, can pass through control chip 2 off switch circuit 1, to play the effect of protection switch pipe Q2 and other elements of circuit.Current foldback circuit 7 can prevent effectively that the electric current of switching tube Q2 is excessive.
In the circuit diagram of the preferred embodiment of constant-current drive circuit with power factor correction of the present utility model shown in Figure 2, constant-current drive circuit with power factor correction also comprise the output that is used to connect constant-current drive circuit with power factor correction and have power factor correction constant-current drive circuit output diode D4 and be used to prevent that circuit from opening, close or the thermistor NTC1 of the surge current during short circuit, the end of thermistor NTC1 is connected with the negative pole of diode D5, and the other end of thermistor NTC1 is connected with the output of the constant-current drive circuit with power factor correction.Diode D4 can so that input voltage directly export without circuit of power factor correction, when the input voltage of the output of the constant-current drive circuit with power factor correction exceeds the scope of requirement, can directly give the circuit supply of back, not influence the work of whole drive circuit by diode D4.Thermistor NTC1 can effectively suppress circuit and open, closes or the surge current during short circuit.
Specify the course of work of the constant-current drive circuit that originally has power factor correction below by the circuit diagram of Fig. 2.
This constant-current drive circuit can change into the direct voltage of the 140V-373V scope after the rectification constant-current circuit that stable 400V direct voltage energising was held C4 filtering and supplied with the back.When direct voltage is imported, by resistance R 3, the start-up circuit 3 that resistance R 4 and resistance R 11 constitute gives control chip 2 power supplies, make control chip 2 work, the conducting of the switching tube Q2 of control chip 2 output square wave control switch circuit 1 with end, pass through electric current on the transformer T1 like this, the auxiliary winding of transformer T1 induces alternating voltage, alternating voltage is by the resistance R 6 of AC/DC change-over circuit, capacitor C 3, become direct voltage behind diode D2 and the diode D3, pass through again by capacitor C 2, voltage-stabiliser tube ZD2, triode Q1, diode D1, capacitor C 9, the linear voltage-stabilizing circuit that capacitor C 10 and voltage-stabiliser tube ZD1 form, in capacitor C 9, capacitor C 10 two ends form galvanic current and press voltage after the normal startup to control chip 2 is provided, and make the control chip 2 can continuous firing.Resistance R 9, resistance R 8, resistance R 18, resistance R 17, resistance R 19 and capacitor C 7 are formed output voltage feedback circuit 6, the output voltage signal of sampling is fed back to control chip 2, control chip 2 is by changing the output duty cycle control switch pipe Q2 of oneself, makes output voltage stabilization.Resistance R 1, resistance R 2, resistance R 10 and capacitor C 5 constitute input voltage feedback circuit 5 voltage signal of sampling are fed back to control chip 2, control chip 2 is by changing the output duty cycle control Q2 of oneself, make the average current input waveform follow input voltage waveform, thereby improved power factor.Resistance R 16, resistance R 13 and capacitor C 8 constitute current foldback circuit 7; in case take place to cause the electric current of switching tube Q2 excessive unusually; current foldback circuit 7 will feed back to control chip 2, control chip 2 is quit work and has protected other elements of circuit to be without prejudice.The existence of thermistor NTC1 can effectively suppress start, the surge current when shutdown and output short-circuit.When input voltage exceeds the scope of requirement, can directly give the circuit supply of back by diode D4, do not influence the work of whole drive circuit.Constant-current drive circuit with power factor correction of the present utility model is connected on after the ballast and before the big electric capacity, can be provided to the power factor of light fixture constant-current drive circuit more than 0.95.
The above only is embodiment of the present utility model; be not so limit claim of the present utility model; every equivalent structure transformation that utilizes the utility model specification and accompanying drawing content to be done; or directly or indirectly be used in other relevant technical fields, all in like manner be included in the scope of patent protection of the present utility model.