Background technology
In daily life, interchange turns DC circuit and usually is applied in the fields such as charger, adapter, light fixture, and at present traditional AC-DC power conversion chip adopts five pin SOT23(Small Outline Transistor, small outline transistor usually) the formula encapsulation.
Fig. 1 shows the AC-DC power conversion chip of existing five pin encapsulation, comprising grounding pin 11, power pins 12, direct current output pin 13, feedback voltage pin 14, input pin 15, voltage regulation unit 16, modulating unit 17, reference cell 18 and comparing unit 19.
The input of voltage regulation unit 16 is connected with the inside input of power pins 12, the feedback end of voltage regulation unit 16 is connected with the inside link of feedback voltage pin 14, the output of voltage regulation unit 16 is connected with the input of modulating unit 17, the first input end of comparing unit 19 is connected with the output of reference cell 18, the second input of comparing unit 19 is connected with the inside link of input pin 15, the output of comparing unit 19 is connected with the control end of modulating unit 17, and the output of modulating unit 17 is connected with the inside link of direct current output pin 13.
Starting resistor inputs to voltage regulation unit 16 by power pins 12, it is the power supply of AC-DC power conversion chip 1 internal module that voltage regulation unit 16 is converted to internal supply voltage with the starting resistor of this high voltage direct current, modulation circuit 17 is low-voltage dc voltage with this voltage transitions further, export power-switching circuit to by direct current output pin 13, input pin 15 is used for by the external power source change-over circuit output low-voltage dc voltage being sampled, and the reference voltage that sampled signal and reference cell 18 are provided relatively, to modulation circuit 17 output control signals, to export the amplitude stability of low-voltage dc voltage by the pulse width modulation of control modulation circuit.
Fig. 2 shows the power-switching circuit of the AC-DC power conversion chip of existing five pin encapsulation, comprising:
AC-DC power conversion chip 1, current rectifying and wave filtering circuit 21, start-up circuit 22, switching circuit 23, transformer 24, feedback circuit 25 and filter circuit 26.
The input of current rectifying and wave filtering circuit 21 connects AC power, the output of current rectifying and wave filtering circuit 21 is connected with the input of start-up circuit 22, the output of start-up circuit 22 is connected with the outside link of the power pins 12 of AC-DC power conversion chip 1, the input of switching circuit 23 is connected with the outside link of AC-DC power conversion chip 1 direct current output pin 13, the sampling end of switching circuit 23 is connected with the outside link of the input pin 15 of AC-DC power conversion chip 1, the earth terminal of switching circuit 23 is connected with the outside link of the grounding pin of AC-DC power conversion chip 1, common ground, the output of switching circuit 23 is connected with the armature winding of transformer 24, the auxiliary winding of transformer 24 is connected with the input of feedback circuit 25, the output of feedback circuit 25 is connected with the outside link of the feedback voltage pin 14 of AC-DC power conversion chip 1, the secondary winding of transformer 24 is connected with the input of filter circuit 26, and the output of filter circuit 26 is the output of power-switching circuit of the AC-DC power conversion chip 1 of this five pin encapsulation.
AC power is through becoming the direct current of concussion high pressure behind the current rectifying and wave filtering circuit 21, this high voltage direct current is by charging with bootrom 1 to start-up circuit, make the direct current output pin 13 output low-voltage DCs of chip 1, this low-voltage DC is exported to the armature winding of transformer 24 by switch element 23, by secondary winding this voltage is passed to filter circuit 26, is undertaken becoming this power-switching circuit output voltage behind the secondary filtering by 26 pairs of these low-voltage DCs of filter circuit.
Feedback circuit 25 is sensed electric current by the auxiliary winding of transformer 24 and is fed back to voltage regulation unit 16 by feedback voltage pin 14, and voltage regulation unit 16 is adjusted the stable of chip internal supply power voltage by this feedback voltage.
Switching circuit 23 is converted to sampled signal with direct current output pin 13 output low-voltage DCs and exports to comparing unit 19 by signal controlling pin 15, is adjusted the stability of output low-voltage DC according to sampled signal control modulation circuit 17 by comparing unit 19.
Because the structure of five pins of above-mentioned AC-DC power conversion chip is so that this chip can only be selected the encapsulation of SOT23 formula at present, still, SOT23 formula packaging technology is complicated, and cost is high, is unfavorable for the extensive use of AC-DC power conversion chip.
Summary of the invention
The purpose of the embodiment of the invention is to provide a kind of AC-DC power conversion chip, is intended to solve the AC-DC power conversion chip cost of manufacture height of existing five leg structures, the problem of packaging technology complexity.
The embodiment of the invention is achieved in that a kind of AC-DC power conversion chip, comprises grounding pin, band-gap reference unit and pwm unit, and described chip also comprises:
Power pins is used for the input starting resistor or is used for input chip exterior supply power voltage and feedback signal;
The direct current output pin is used for the output low-voltage dc voltage, and described low-voltage dc voltage is inputted described chip as sampled signal;
Voltage regulation unit, the input of described voltage regulation unit is connected with the inside link of described power pins, the output of described voltage regulation unit is connected with the input of described pwm unit, be used for described starting resistor or chip exterior supply power voltage are converted to the chip internal supply power voltage, and adjust the amplitude of chip internal supply power voltage according to described feedback signal;
Comparing unit, the first input end of described comparing unit is connected with the output of described band-gap reference unit, the second input of described comparing unit is connected with the inside link of described direct current output pin, the output of described comparing unit is connected with the input of described pwm unit, be used for reference voltage that described sampled signal and described band-gap reference unit are provided relatively, described pwm unit is exported comparison control signal.
Another purpose of the embodiment of the invention is to provide a kind of power-switching circuit that adopts said chip, comprises rectification circuit, filter capacitor C1, and described power-switching circuit also comprises:
Start-up circuit, the input of described start-up circuit is connected with the end of described filter capacitor C1, and the output of described start-up circuit is connected with the bringing-out of described power pins, is used for charging when power supply electrifying, to described chip output starting resistor;
Switching circuit, the input of described switching circuit is connected with the outside link of described direct current output pin, the outside link common ground of the earth terminal of described switching circuit and described grounding pin is used for conducting when described chip is exported described low-voltage dc voltage, the output On current;
Transformer T1, the Same Name of Ends of the armature winding N1 of described transformer T1 is connected with the input of described start-up circuit, the different name end of described armature winding N1 is connected with the output of described switching circuit, the Same Name of Ends of the secondary winding N2 of described transformer T1 is the output negative pole of described power-switching circuit, the different name end of the secondary winding N2 of described transformer T1 is the output cathode of described power-switching circuit, the Same Name of Ends ground connection of the auxiliary winding N3 of described transformer T1, be used for described On current is converted to output voltage, and provide described supply power voltage and feedback signal for described chip;
Diode D6, the anode of described diode D6 is connected with the different name end of the auxiliary winding N3 of described transformer T1, the negative electrode of described diode D6 is connected with the bringing-out of described power pins, is used for transmitting the forward voltage of described supply power voltage and feedback signal, resists reverse voltage;
Filter circuit, the positive input terminal of described filter circuit is connected with the different name end of the secondary winding N2 of described transformer T1, the negative input end of described filter circuit is connected with the Same Name of Ends of the secondary winding N2 of described transformer T1, the positive output end of described filter circuit is the output cathode of described power-switching circuit, the negative output terminal of described filter circuit is the output negative pole of described power-switching circuit, for reducing the ripple in the low-voltage dc voltage of sensing.
In embodiments of the present invention, by changing AC-DC power conversion chip internal module structure and external power source change-over circuit, so that only can realize that by power pins, grounding pin and direct current output pin alternating current arrives galvanic conversion, effectively reduce cost of manufacture, and this structure is applicable to the encapsulation of TO92 formula, further simplify packaging technology, be conducive to the extensive use of AC-DC power conversion chip.
Embodiment
In order to make purpose of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, is not intended to limit the present invention.
The embodiment of the invention utilizes voltage regulation unit directly from the power pins receiving feedback signals, and directly detects the output low-voltage dc voltage from the direct current output pin by comparing unit, and the pin of AC-DC power conversion chip is reduced to three.
Fig. 3 illustrates the structure of the AC-DC power conversion chip that the embodiment of the invention provides, and for convenience of explanation, only shows part related to the present invention.
As the AC-DC power conversion chip 3 that one embodiment of the invention provides, comprise grounding pin 31, band-gap reference unit 36 and pwm unit 35, this chip 3 also comprises:
Power pins 32 is used for the input starting resistor or is used for input chip exterior supply power voltage and feedback signal;
Direct current output pin 33 is used for the output low-voltage dc voltage, and this low-voltage dc voltage is inputted AC-DC power conversion chip 3 as sampled signal;
Voltage regulation unit 34, the input of this voltage regulation unit 34 is connected with the inside link of power pins 32, the output of voltage regulation unit 34 is connected with the input of pwm unit 35, be used for starting resistor or chip exterior supply power voltage are converted to the chip internal supply power voltage, and adjust the amplitude of chip internal supply power voltage according to feedback signal;
Comparing unit 37, the first input end of this comparing unit 37 is connected with the output of band-gap reference unit 36, the second input of comparing unit 37 is connected with the inside link of direct current output pin 33, the output of comparing unit 37 is connected with the input of pwm unit 35, be used for reference voltage that sampled signal and band-gap reference unit 36 are provided relatively, comparison control signals are exported in pulse-width modulated unit 35.
As one embodiment of the invention, grounding pin 31 is drawn chip with the chip internal earth terminal, be connected with ground wire, behind the alternating voltage process rectifying and wave-filtering of input, form the high-voltage dc signal of concussion, this high-voltage dc signal inputs to voltage regulation unit 34 as the starting resistor of AC-DC power conversion chip 3 by power pins 32, it is chip 3 in-line powers that voltage regulation unit 34 is converted to stable direct current supply voltage with starting resistor, pwm unit 35 is converted to the low-voltage dc voltage of certain amplitude with this internal supply voltage, and exports chip exterior to by direct current output pin 33.
The low-voltage dc voltage of output can produce induced current as feedback signal by transformer, input to voltage regulation unit 34 by power pins 32, voltage regulation unit 34 is according to the amplitude of feedback signal adjustment chip internal supply power voltage, with the chip internal supply power voltage of stable output.
The low-voltage dc voltage of output also simultaneously inputs to comparing unit 37 as sampled signal, comparing unit 37 compares the reference voltage of this sampled signal and 36 generations of band-gap reference unit, when sampled signal during greater than reference voltage, comparing unit 37 is to pwm unit 35 output comparison control signals, make pwm unit 35 reduce the duty ratio of pulse width modulating signal, and then reduce the amplitude of output dc voltage, when sampled signal during less than reference voltage, comparing unit 37 is to pwm unit 35 output comparison control signals, make pwm unit 35 increase the duty ratio of pulse width modulating signal, and then the amplitude of increase output dc voltage, with stablizing of control output dc voltage amplitude.
In embodiments of the present invention, the parameters such as the efficient of AC-DC power conversion chip and reliability can reach the technical indicator identical with the AC-DC power conversion chip of existing five pin SOT23 formulas encapsulation.
As one embodiment of the invention, AC-DC power conversion chip 3 can adopt transistor T O92(Transistor outline, transistor outline) the formula encapsulation.
In embodiments of the present invention, utilize voltage regulation unit directly from the power pins receiving feedback signals, and pass through comparing unit and directly detect the output low-voltage dc voltage from the direct current output pin, the pin of AC-DC power conversion chip is reduced to three, effectively reduce cost of manufacture, and this structure is applicable to TO92 formula encapsulation, further simplified packaging technology, reduce packaging cost, be conducive to the extensive use of AC-DC power conversion chip.
Fig. 4 illustrates the structure of the power-switching circuit of the AC-DC power conversion chip that the embodiment of the invention provides, and for convenience of explanation, only shows part related to the present invention.
The power-switching circuit of this AC-DC power conversion chip can be used in charger, adapter, light fixture and the led drive circuit.
As one embodiment of the invention, the power-switching circuit of AC-DC power conversion chip comprises rectification circuit 41, filter capacitor C1, and described power-switching circuit also comprises:
Start-up circuit 42, the input of this start-up circuit 42 is connected with the end of filter capacitor C1, and the output of start-up circuit 42 is connected with the bringing-out of power pins 12, is used for charging when power supply electrifying, to chip 3 output starting resistors;
Switching circuit 43, the input of this switching circuit 43 is connected with the outside link of direct current output pin 33, the outside link common ground of the earth terminal of switching circuit 43 and grounding pin 31 is used for conducting when chip 3 output low-voltage dc voltage, the output On current;
Transformer T1, the Same Name of Ends of the armature winding N1 of this transformer T1 is connected with the input of start-up circuit 42, the different name end of armature winding N1 is connected with the output of switching circuit 43, the Same Name of Ends of the secondary winding N2 of transformer T1 is the output negative pole of the power-switching circuit of AC-DC power conversion chip, the different name end of the secondary winding N2 of transformer T1 is the output cathode of the power-switching circuit of AC-DC power conversion chip, the Same Name of Ends ground connection of the auxiliary winding N3 of transformer T1, be used for On current is converted to output voltage, and provide supply power voltage and feedback signal for chip;
Diode D6, the anode of diode D6 is connected with the different name end of the auxiliary winding N3 of transformer T1, and the negative electrode of diode D6 is connected with the bringing-out of power pins 32, is used for transmitting the forward voltage of described supply power voltage and feedback signal, resists reverse voltage;
Filter circuit 46, the positive input terminal of filter circuit 46 is connected with the different name end of the secondary winding N2 of transformer T1, the negative input end of filter circuit 46 is connected with the Same Name of Ends of the secondary winding N2 of transformer T1, the positive output end of filter circuit 46 is the output cathode of the power-switching circuit of AC-DC power conversion chip, the negative output terminal of filter circuit 46 is the output negative pole of the power-switching circuit of AC-DC power conversion chip, for reducing the ripple in the low pressure concussion direct voltage of sensing.
Below in conjunction with specific embodiment realization of the present invention is elaborated.
Fig. 5 illustrates the exemplary circuit structure of the power-switching circuit of the AC-DC power conversion chip that the embodiment of the invention provides, and for convenience of explanation, only shows part related to the present invention.
As one embodiment of the invention, start-up circuit 42 comprises: resistance R 1 and capacitor C 3, and an end of resistance R 1 is the input of start-up circuit 42, the other end of resistance R 1 is connected with an end of capacitor C 3, its link is the output of start-up circuit 42, the other end ground connection of capacitor C 3.
Switching circuit 43 comprises: triode Q1 and resistance R 3, the base stage of triode Q1 is the input of switching circuit 43, the current collection of triode Q1 is the output of switching circuit 43 very, and the emitter of triode Q1 is connected with an end of resistance R 3, and the other end of resistance R 3 is the earth terminal of switching circuit 43.
Filter circuit 46 comprises: diode D7, capacitor C 4 and resistance R 4, capacitor C 4 is in parallel with resistance R 4, capacitor C 4 is negative input end and the negative output terminal of filter circuit 46 with a common port of resistance R 4 simultaneously, capacitor C 4 is the positive output end of filter circuit 46 with another common port of resistance R 4, be connected with the negative electrode of diode D7, the anode of diode D7 is the positive input terminal of filter circuit 46.
In embodiments of the present invention, AC power becomes the high voltage direct current of concussion by 3 chargings of 1 pair of capacitor C of resistance R after through the rectification circuit 41 that is made of rectifier bridge and filter capacitor C1, when the voltage on the capacitor C 3 reaches the starting resistor 12V of chip 3, chip 3 is started working, power pins 32 is the power supplies of chip 3 internal modules with the supply power voltage that this starting resistor is converted to chip internal, and pass through direct current output pin 33 by pulse width modulation circuit 35 and export low-voltage dc voltages, this low-voltage dc voltage makes triode Q1 conducting, there is On current to flow through among the armature winding N1 of triode Q1 and transformer T1, at this moment, the auxiliary winding N3 of transformer T1 provides externally fed voltage to make chip 3 continuous firings by diode D6 to chip 3 induced current, this externally fed voltage inputs to voltage regulation unit 34 as feedback signal by power pins 32 simultaneously, being converted to the galvanic current pressure through voltage stabilizing circuit 34 is the chip internal power supply, comparing unit 37 gathers triode Q1 base stage by direct current output pin 33 voltage compares as sampled signal and reference voltage, low-voltage dc voltage with control impuls modulation circuit 35 stable outputs, this low-voltage dc voltage is sensed on the secondary winding N2 through the armature winding N1 of transformer T1, because this voltage is coil-induced voltage, with certain ripple, therefore the filter circuit 46 by diode D7 and capacitor C 4 and resistance R 4 compositions reduces ripple, the low-voltage dc voltage of stable output.
In embodiments of the present invention, by changing AC-DC power conversion chip internal module structure and external power source change-over circuit, so that only can realize that by power pins, grounding pin and direct current output pin alternating current arrives galvanic conversion, effectively reduce cost of manufacture, and this structure is applicable to the encapsulation of TO92 formula, further simplify packaging technology, be conducive to the extensive use of AC-DC power conversion chip.
As one embodiment of the invention, the power-switching circuit of AC-DC power conversion chip can also comprise:
Absorbing circuit 45, the input of absorbing circuit 45 is connected with the different name end of the armature winding N1 of transformer T1, and the output of absorbing circuit 45 is connected with the Same Name of Ends of the armature winding N1 of transformer T1, is used for absorbing leakage inductance current spike voltage.
This absorbing circuit 45 comprises: diode D5, capacitor C 2 and resistance R 2, resistance R 2 is in parallel with capacitor C 2, resistance R 2 is the output of absorbing circuit 45 with a common port of capacitor C 2, resistance R 2 is connected with the negative electrode of diode D5 with another common port of capacitor C 2, and the anode of diode D5 is the input of absorbing circuit 45.
In embodiments of the present invention, absorb the peak voltage that is produced by the Transformer Winding leakage inductance by absorptive unit, it is breakdown that switch element is difficult for, and increased the reliability of the power-switching circuit of AC-DC power conversion chip.
In embodiments of the present invention, utilize voltage regulation unit directly from the power pins receiving feedback signals, and pass through comparing unit and directly detect the output low-voltage dc voltage from the direct current output pin, the pin of AC-DC power conversion chip is reduced to three, and by changing its external power source change-over circuit, so that only pass through power pins, grounding pin and direct current output pin can realize that alternating current arrives galvanic conversion, effectively reduce cost of manufacture, simplified packaging technology, be conducive to the extensive use of AC-DC power conversion chip, absorb peak voltage by increasing absorptive unit in addition, increased the reliability of the power-switching circuit of AC-DC power conversion chip.
The above only is preferred embodiment of the present invention, not in order to limiting the present invention, all any modifications of doing within the spirit and principles in the present invention, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.