Based on the switching power supply of pulse-width-modulating type
Technical field
The utility model relates to a kind of switching power supply, specifically refers to a kind of switching power supply based on pulse-width-modulating type.
Background technology
Along with continuous progress scientific and technological at present, electronic product also brings great convenience to people are in life while function from strength to strength.Voltage stabilizing circuit is just runed and gives birth to, and traditional series connection linear regulator type voltage stabilizing circuit has the features such as stability is high, output voltage is adjustable, ripple coefficient is little, circuit is simple.But the Correctional tube of these series connection linear regulator type voltage stabilizing circuits is always operating at magnifying state, and have electric current to flow through, therefore the power consumption of its pipe is comparatively large, the efficiency of circuit is not high, generally can only reach about 30% ~ 50% always.In order to overcome above-mentioned defect, people just have developed switching mode voltage stabilizing circuit.
In switching mode voltage stabilizing circuit, surge pipe is operated on off state, pipe alternation saturated with cut-off two states in.When pipe saturation conduction, though it is large to flow through pipe current, but tube voltage drop is very little; When pipe ends, tube voltage drop is large, but the electric current flow through is close to zero.Therefore, under power output the same terms, the efficiency of switching mode voltage stabilizer coin series regulator is high, generally can reach about 80% ~ 90%.But it is comparatively large that the switching mode voltage stabilizer that current people adopt but exists ripple coefficient, when Correctional tube constantly switches between saturated and cut-off state, radio frequency interference can be produced to circuit, circuit more complicated and cost is higher.
Utility model content
The purpose of this utility model is the defect that ripple coefficient is comparatively large, radio frequency interference is serious, circuit is complicated and efficiency is not high overcoming the existence of current switching mode voltage stabilizer, provides a kind of switching power supply based on pulse-width-modulating type.
The purpose of this utility model is achieved through the following technical solutions: based on the switching power supply of pulse-width-modulating type, primarily of diode rectifier U, power amplifier P1, transformer T, be serially connected in the switched filter circuit between diode rectifier U and power amplifier P1, the power output circuit be connected with the secondary coil L2 of transformer T, the transformation feedback circuit be connected with the secondary coil L3 of transformer T, the ON-OFF control circuit be connected with transformation feedback circuit, the oscillator be connected with ON-OFF control circuit, the current comparator I1 be connected with ON-OFF control circuit, the current comparator I2 be connected with ON-OFF control circuit, respectively with oscillator, the slope equalizer W that current comparator I1 is connected with current comparator I2, the PWM controller be connected with current comparator I1 with power amplifier P1 respectively, and output is connected with the tap on the primary coil L1 of transformer T, and the sliding damper that input is connected with the output of power amplifier P1 forms.
Further, described switched filter circuit is by triode Q, and electric capacity C1, electric capacity C2, resistance R1, resistance R2 and diode D1 form; The base stage of described triode Q forms loop with its collector electrode in turn after resistance R2, diode D1 and resistance R1, and electric capacity C1 and resistance R1 is in parallel, and electric capacity C2 and resistance R2 is in parallel; The collector electrode of triode Q is connected with the cathode output end of diode rectifier U, its grounded emitter; The cathode output end of diode rectifier U is then directly connected with the end of oppisite phase of power amplifier P1, and resistance R2 is then connected with the in-phase end of power amplifier P1 with the tie point of diode D1; The primary coil L1 of transformer T is then in parallel with diode D1.
The diode D2 that described power output circuit is connected with the Same Name of Ends of secondary coil L2 by P pole, N pole is connected with the non-same polarity of secondary coil L2 after electric capacity C3, and the inductance L 4 that one end is connected with the N pole of diode D2, the other end is connected with the non-same polarity of secondary coil L2 after electric capacity C4 forms.
Described transformation feedback circuit is made up of diode D3 and electric capacity C5; The P pole of described diode D3 is connected with the non-same polarity of secondary coil L3, its N pole is connected with the Same Name of Ends of secondary coil L3 after electric capacity C5, the Same Name of Ends ground connection of described secondary coil L3.
Described ON-OFF control circuit is made up of field effect transistor MOS, power amplifier P2, voltage comparator U1, inductance L 5 and resistance R3; Described inductance L 5 is serially connected between the output of power amplifier P1 and the N pole of diode D3, and the drain electrode of field effect transistor MOS is connected with the N pole of diode D3, its source electrode ground connection, its grid after resistance R3 are then connected with the output of power amplifier P2; The S end of voltage comparator U1 is connected with the output of oscillator, and its R end is connected with the output of current comparator I1, and its Q end is then connected with the end of oppisite phase of power amplifier P2; The in-phase end of power amplifier P2 is then connected with the drain electrode of field effect transistor MOS; The electrode input end of current comparator I2 is then connected with the two ends of resistance R3 with negative input, and its output is connected with the input of oscillator with the negative input of current comparator I1 respectively after slope equalizer W; The electrode input end of current comparator I1 is then connected with the output of power amplifier P1; An output of PWM controller is connected with the end of oppisite phase of power amplifier P1 with the negative input of current comparator I1 respectively, its another output ground connection after electric capacity C6.
The utility model comparatively prior art is compared, and has the following advantages and beneficial effect:
(1) the utility model make use of the controlling functions of PWM fully, can automatically regulate electric power output voltage value according to duty ratio, guarantees the stable of output valve.
(2) the utility model initiative slope equalizer and voltage, current comparator are used in a power, not only effectively reduce circuit self and external radio frequency interference, but also greatly simplify circuit structure, cost of manufacture and maintenance cost are had reduction by a relatively large margin.
(3) the utility model utilizes field effect transistor to form ON-OFF control circuit, the utility model is not only made to have possessed boost mode and decompression mode, but also making the change of full voltage range output current control between ± 0.1%, the output current change control range of more traditional switching power supply is greatly improved.
Accompanying drawing explanation
Fig. 1 is overall structure schematic diagram of the present utility model.
Embodiment
Below in conjunction with embodiment, the utility model is described in further detail, but execution mode of the present utility model is not limited thereto.
Embodiment
As shown in Figure 1, the switching power supply based on pulse-width-modulating type described in the utility model includes diode rectifier U, power amplifier P1, transformer T, switched filter circuit, power output circuit, transformation feedback circuit, ON-OFF control circuit, oscillator, current comparator I1, current comparator I2, slope equalizer W, PWM controller and sliding damper.Wherein, transformer T is by the primary coil L1 being arranged on its former limit, and the secondary coil L2 and the secondary coil L3 that are arranged on its secondary form.The utility model is provided with a sliding tap on the primary coil L1 of transformer T, this sliding tap is then controlled by sliding damper, to guarantee to adjust turn ratio between the primary coil L1 of transformer T and secondary coil L2 and secondary coil L3 according to the duty ratio of PWM controller and the common results of ON-OFF control circuit, thus realize the output of different voltage.
The input of diode rectifier U is used for the civil power of external 220V, between the cathode output end that switched filter circuit is then serially connected in this diode rectifier U and the in-phase end of power amplifier P1.As shown in Figure 1, this switched filter circuit is by triode Q, and electric capacity C1, electric capacity C2, resistance R1, resistance R2 and diode D1 form.Wherein, the base stage of triode Q forms loop with its collector electrode in turn after resistance R2, diode D1 and resistance R1.Electric capacity C1 and resistance R1 is in parallel, and electric capacity C2 and resistance R2 is in parallel, to form typical RC filter circuit.Meanwhile, the collector electrode of triode Q is connected with the cathode output end of diode rectifier U, its grounded emitter; The cathode output end of diode rectifier U is then directly connected with the end of oppisite phase of power amplifier P1, and resistance R2 is then connected with the in-phase end of power amplifier P1 with the tie point of diode D1.Primary coil L1 and the diode D1 of described transformer T are in parallel.
In this switched filter circuit, resistance R1, electric capacity C1 and diode D1 form feedback-clamp circuit, can improve the peak-inverse voltage of conversion efficiency and reduction power amplifier P1 in-phase end.
Power output circuit is used for the direct voltage of stable output, and it is made up of diode D2, electric capacity C3, inductance L 4 and electric capacity C4.During connection, the P pole of diode D2 is connected with the Same Name of Ends of secondary coil L2, and its N pole is connected with the non-same polarity of secondary coil L2 after electric capacity C3.One end of described inductance L 4 is connected with the N pole of diode D2, the other end is connected with the non-same polarity of secondary coil L2 after electric capacity C4.The two ends of electric capacity C4 then as the output of whole power supply, for external loading provides required voltage and current.
Transformation feedback circuit is used for providing feedback operation voltage, to guarantee that ON-OFF control circuit can control sliding damper according to feedback voltage for ON-OFF control circuit.This transformation feedback circuit is then made up of diode D3 and electric capacity C5.During connection, the P pole of described diode D3 is connected with the non-same polarity of secondary coil L3, its N pole is connected with the Same Name of Ends of secondary coil L3 after electric capacity C5, meanwhile, and the Same Name of Ends ground connection of this secondary coil L3.
ON-OFF control circuit is switching control section of the present utility model, and it is made up of field effect transistor MOS, power amplifier P2, voltage comparator U1, inductance L 5 and resistance R3.As shown in Figure 1, this inductance L 5 is serially connected between the output of power amplifier P1 and the N pole of diode D3, and the drain electrode of field effect transistor MOS is connected with the N pole of diode D3, its source electrode ground connection, its grid after resistance R3 are then connected with the output of power amplifier P2.
The S end of voltage comparator U1 is connected with the output of oscillator, and its R end is connected with the output of current comparator I1, and its Q end is then connected with the end of oppisite phase of power amplifier P2.The in-phase end of power amplifier P2 is then connected with the drain electrode of field effect transistor MOS.The electrode input end of current comparator I2 is connected with the two ends of negative input with resistance R3, and during to guarantee field effect transistor MOS conducting, it can collect operating voltage from resistance R3 two ends.
Simultaneously, the output of this current comparator I2 is connected with the input of oscillator with the negative input of current comparator I1 respectively after slope equalizer W, to guarantee that slope equalizer W can provide auxiliary slope-compensation for current comparator I1, make its working stability.
The electrode input end of current comparator I1 is then connected with the non-same polarity of primary coil L1 with the output of power amplifier P1; An output of PWM controller is connected with the end of oppisite phase of power amplifier P1 with the negative input of current comparator I1 respectively, its another output ground connection after electric capacity C6.
During use, the voltage acting on diode rectifier U carries out after filtering as the primary coil L1 of transformer T and power amplifier P1 provides operating voltage through switched filter circuit.When inductance coil L5 senses that external loading changes, when its induction reactance just changes, now power amplifier P2 impels field effect transistor MOS conducting under the acting in conjunction of voltage comparator U1 and inductance L 5, the pulse signal that PWM controller provides acts on power amplifier P1 and current comparator I1 after current comparator I1, sliding damper is obtained electric, and automatically regulate sliding tap according to the situation of change of load, thus change the primary coil L1 of transformer T and the turn ratio between secondary coil L2 and secondary coil L3, final realization is to the stable power-supplying function of load.
As mentioned above, just the utility model can well be realized.