Power circuit
Technical field
The present invention relates to a kind of power circuit.
Background technology
See also Fig. 1, it is a kind of electrical block diagram of prior art power circuit.This power circuit 10 comprises that one first current rectifying and wave filtering circuit 11, a protective circuit 13, isolate high frequency transformer 14, one second current rectifying and wave filtering circuit 15, a transistor 17, a feedback circuit 18 and a PWM controller 19.Wherein, This first current rectifying and wave filtering circuit 11 comprises two inputs 111,112, a full bridge rectifier 113, a filter capacitor 114 and an output 115; This isolation high frequency transformer 14 comprises an elementary winding 141 and a level winding 142; This second current rectifying and wave filtering circuit 15 comprises two inputs 151,152 and an output 150, and this PWM controller 19 comprises a control end 191 and a voltage sample end 192.
Two inputs of this full bridge rectifier 113 i.e. two inputs 111,112 of this first current rectifying and wave filtering circuit; The positive output end of this full bridge rectifier 113 i.e. the output 115 of this first current rectifying and wave filtering circuit; The negative output terminal ground connection of this full bridge rectifier 113, this filter capacitor 114 is connected in parallel between the positive output end and negative output terminal of this full bridge rectifier 113.This protective circuit 13 is parallelly connected with this elementary winding 141 of isolating high frequency transformer 14.These elementary winding 141 1 ends of isolating high frequency transformer 14 are electrically connected with the output 115 of this first current rectifying and wave filtering circuit 11, and its other end is electrically connected with the source electrode of this transistor 17.This secondary winding 142 of isolating high frequency transformer 14 is electrically connected with two inputs 151,152 of this second current rectifying and wave filtering circuit 15.The grid of this transistor 17 is electrically connected with the control end of this PWM controller 19; The drain electrode of this transistor 17 is electrically connected with the voltage sample end 192 of this PWM controller 19 through this feedback circuit 18, and the drain electrode of this transistor 17 is simultaneously through a current-limiting resistance 170 ground connection.
Extraneous alternating voltage inputs to two inputs 111,112 of this first current rectifying and
wave filtering circuit 11, through being output as direct voltage after these first current rectifying and wave filtering circuit, 11 rectifications, the filtering.When these
transistor 17 conductings; This
filter capacitor 114, this elementary winding 141, this
transistor 17 and this current-limiting
resistance 170 of isolating
high frequency transformer 14 constitute a loop; At this moment; These
filter capacitor 114 equivalences are a direct current power supply; These elementary winding 141 equivalences are an inductance, and by formula:
(V representes the voltage of
filter capacitor 114, and L representes the inductance of
elementary winding 141; I represent the to flow through electric current of this elementary winding 141) can know linear the increasing of electric current in the
elementary winding 141, reach maximum at last.This
feedback circuit 18 is with the
voltage sample end 192 of Voltage Feedback to this
PWM controller 19 of this current-limiting
resistance 170; This
PWM controller 19 compares this feedback voltage and its reference voltage; When feedback voltage was higher than its reference voltage, control
end 191 output low levels of this
PWM controller 19 quit work to control this
transistor 17.
When this transistor 17 ended, the electric energy transmitting that this elementary winding 141 stores was to this secondary winding 142, and the output galvanic current is pressed after these second current rectifying and wave filtering circuit, 15 rectifications, filtering.The exciting current of this elementary winding 141 consumes through this protective circuit 13.
So, the AC power that is connected when input 111,112 not simultaneously, the mistake flow point of its output 150 changes greatly.For example, when AC power was 100V, recording flow point at output 150 was 2.61A, and when AC power was 240V, recording flow point at output 150 was 3.70A.When the voltage of the AC power that is connected when input 111,112 was very high, the electric current in the circuit was also corresponding bigger, if when input side or outlet side break down, this power circuit 10 just possibly burnt.
Summary of the invention
For the mistake flow point that solves power circuit output end in the prior art changes problem greatly, the present invention provides a kind of mistake flow point stable power circuit that makes output.
A kind of power circuit, it comprises one first current rectifying and wave filtering circuit, an isolation high frequency transformer, one second current rectifying and wave filtering circuit, a transistor, a feedback circuit, a PWM controller and a compensating circuit.Wherein, This first current rectifying and wave filtering circuit comprises two inputs and an output; This isolation high frequency transformer comprises an elementary winding, level winding and an auxiliary winding; This second current rectifying and wave filtering circuit comprises two inputs and an output, and this PWM controller comprises that a control end and a voltage sample end and its have reference voltage.This elementary winding one end of isolating high frequency transformer is electrically connected with the output of this first current rectifying and wave filtering circuit, and its other end is electrically connected with this transistorized source electrode; This secondary winding of isolating high frequency transformer is electrically connected with two inputs of this second current rectifying and wave filtering circuit; This auxiliary winding one end of isolating high frequency transformer is electrically connected its other end ground connection through this compensating circuit with the voltage sample end of this PWM controller.This transistorized grid is electrically connected with the control end of this PWM controller; This transistor drain is electrically connected with the voltage sample end of this PWM controller so that feedback voltage to be provided through this feedback circuit, and this transistor drain is ground connection simultaneously.This compensating circuit comprises a diode, one first resistance and one second resistance; The positive pole of this diode is electrically connected with auxiliary winding one end of this isolation high frequency transformer; Its negative pole is electrically connected with the voltage sample end of this PWM controller through this first resistance, and the voltage sample end of this PWM controller is simultaneously through this second grounding through resistance.Wherein, When two AC powers that input connected of this first current rectifying and wave filtering circuit change; This compensating circuit will assist voltage sample end that the induced voltage of winding feeds back to this PWM controller so that the induction feedback voltage to be provided; This induction feedback voltage and this feedback voltage are superimposed to be total feedback voltage; This PWM controller should total feedback voltage and its reference voltage compares and send control signal corresponding controlling this transistor by this control end, thereby makes the mistake flow point of output of this power circuit stable.
Compared with prior art; Power circuit of the present invention increases by a compensating circuit and feeds back with the voltage to input side; When AC power that input connected changes; This compensating circuit will assist the induced voltage of winding to feed back to the voltage sample end of this PWM controller; The feedback voltage of this feedback voltage and this feedback circuit is superimposed, this PWM controller should total feedback voltage and its reference voltage compare and send control signal corresponding controlling this transistor, thereby make the mistake flow point of this power circuit output end stable.
Description of drawings
Fig. 1 is a kind of electrical block diagram of prior art power circuit.
Fig. 2 is the electrical block diagram of power circuit of the present invention.
Embodiment
See also Fig. 2, it is the electrical block diagram of power circuit of the present invention.This power circuit 20 comprises that one first current rectifying and wave filtering circuit 21, a protective circuit 23, isolate high frequency transformer 24, one second current rectifying and wave filtering circuit 25, a transistor 27, a feedback circuit 28, a PWM controller 29 and a compensating circuit 31; Wherein, this first current rectifying and wave filtering circuit 21 comprises two inputs 211,212, a full bridge rectifier 213, a filter capacitor 214 and an output 215.This isolation high frequency transformer 24 comprises an elementary winding 241, a level winding 242 and an auxiliary winding 30.This second current rectifying and wave filtering circuit 25 comprises two inputs 251,252 and an output 250.This PWM controller 29 comprises a control end 291 and a voltage sample end 292.This compensating circuit 31 comprises an input 310, an output 315, a diode 313, one first resistance 311 and one second resistance 312.
Two inputs of this full bridge rectifier 213 are as two inputs 211,212 of this first current rectifying and wave filtering circuit 21; The positive output end of this full bridge rectifier 213 is as the output 215 of this first current rectifying and wave filtering circuit 21; The negative output terminal ground connection of this full bridge rectifier 21, this filter capacitor 214 is connected in parallel between the positive output end and negative output terminal of this full bridge rectifier 213.This protective circuit 23 is parallelly connected with this elementary winding 241 of isolating high frequency transformer 24.These elementary winding 241 1 ends of isolating high frequency transformer 24 are electrically connected with the output 215 of this first current rectifying and wave filtering circuit 21, and its other end is electrically connected with the source electrode of this transistor 27.This secondary winding 242 of isolating high frequency transformer 24 is electrically connected with two inputs 251,252 of this second current rectifying and wave filtering circuit 25.The grid of this transistor 27 is electrically connected with the control end 291 of this PWM controller 29; The drain electrode of this transistor 27 is electrically connected with the voltage sample end 292 of this PWM controller 29 through this feedback circuit 28, and the drain electrode of this transistor 27 is simultaneously through a current-limiting resistance 270 ground connection.These auxiliary winding 30 1 ends of isolating high frequency transformer 24 are electrically connected its other end ground connection with the input 310 of this compensating circuit 31.This diode 313 and this first resistance 311 are serially connected between the input 310 and output 315 of this compensating circuit 31; And the negative pole of this diode 313 is connected with this first resistance 311; The output 315 of this compensating circuit 31 is electrically connected with the voltage sample end 292 of this PWM controller 29, and it is simultaneously through these second resistance, 312 ground connection.
Extraneous alternating voltage inputs to two inputs 211,212 of this first current rectifying and wave filtering circuit 21, through being output as direct voltage after these first current rectifying and wave filtering circuit, 21 rectifications, the filtering.When these transistor 27 conductings; This filter capacitor 214, this elementary winding 241, this transistor 27 and this current-limiting resistance 270 of isolating high frequency transformer 24 constitute a loop; At this moment; These filter capacitor 214 equivalences are a direct current power supply; These elementary winding 241 equivalences are an inductance, and by formula:
![Figure GDA0000067220270000051](https://patentimages.storage.googleapis.com/24/41/a2/8ae7360cf1a26b/GDA0000067220270000051.png)
(V representes the voltage of filter capacitor 214, and L representes the inductance of elementary winding 241; I represent the to flow through electric current of this elementary winding 241) can know linear the increasing of electric current in the elementary winding 241, reach maximum at last.This feedback circuit 28 is with the voltage sample end 292 of Voltage Feedback to this PWM controller 29 of this current-limiting resistance 270.
Should assist winding 30, this diode 313, this first resistance 311 and this second resistance 312 also to constitute a loop; At this moment; Should auxiliary winding 30 equivalences be a power supply; By formula:
![Figure GDA0000067220270000052](https://patentimages.storage.googleapis.com/22/d6/28/201b6099799976/GDA0000067220270000052.png)
(ε representes the induced electromotive force of auxiliary winding 30; M representes that the elementary winding 241 and the mutual inductance of auxiliary winding 30 are several; I representes the electric current in the elementary winding 241) in the time of can knowing the electric current linear change in the elementary winding 241, the induced electromotive force of this auxiliary winding 30 remains unchanged, the voltage sample end 292 of the Voltage Feedback of this second resistance 312 to this PWM controller 29; The feedback voltage of this feedback voltage and feedback circuit 28 is superimposed; This PWM controller 29 should total feedback voltage and its reference voltage compare, when feedback voltage was higher than its reference voltage, control end 291 output low levels of this PWM controller 29 quit work to control this transistor 27.
When this transistor 27 ended, the electric energy transmitting that this elementary winding 241 stores was to this secondary winding 242, and the output galvanic current is pressed after these second current rectifying and wave filtering circuit, 25 rectifications, filtering.The exciting current of this elementary winding 241 consumes through this protective circuit 23.
This power circuit 20 was carried out the flow point test: when input voltage was 100V, recording flow point at output 250 was 2.61A, and when input voltage was 240V, recording flow point at output 250 was 2.62A.This shows that the mistake flow point of these second current rectifying and wave filtering circuit, 25 outputs 250 is constant basically.
Compared with prior art; Power circuit 20 of the present invention increases by a compensating circuit 31 and feeds back with the voltage to input side; When the AC power that is connected when input 211,212 changes; This compensating circuit 20 will assist the induced voltage of winding 30 to feed back to the voltage sample end 292 of this PWM controller 29; The feedback voltage of this feedback voltage and this feedback circuit 28 is superimposed, this PWM controller 29 should total feedback voltage and its reference voltage compare and send control signal corresponding controlling this transistor 27, thereby make the mistake flow point of these power circuit 20 outputs stable.