CN201830145U

CN201830145U - Switching power supply

Info

Publication number: CN201830145U
Application number: CN2010205654199U
Authority: CN
Inventors: 马鹏飞
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-10-19
Filing date: 2010-10-19
Publication date: 2011-05-11
Anticipated expiration: 2020-10-19

Abstract

The utility model relates to a switching power supply. A voltage is output after an input voltage is processed by a high-voltage rectifier filter circuit, a switch conversion circuit and a low-voltage rectifier filter circuit sequentially. An optoelectronic isolating device sampling circuit is designed for carrying out sampling on an output. The sampled output and an input circuit sampling signal are fed to a control circuit to regulate the switch conversion circuit so as to make the output voltage stabilized. Moreover, a circuit for adsorbing spike pulses is added at the switching position for adsorbing the spike pulses generated by the circuits.

Description

Switching Power Supply

Affiliated technical field

The utility model relates to employing photoelectricity and isolates the introducing feedback signal, and the stabilized voltage supply device that the containment spike disturbs has especially been introduced two switching power supplies that voltage stabilizing is carried out in the feedback signal acting in conjunction.

Background technology

At present, switching power supply is at computer, television set, and fields such as communication and space technology have obtained using widely.Ripple and noise contribution are bigger in the known switching power supply output voltage, complex structure, and the feedback signal of introducing is single, and voltage regulation result is not very desirable.

Summary of the invention

Carry out voltage stabilizing in order better to introduce feedback signal, overcome the interference that spike causes, improve the stability of power supply, the utility model provides a kind of Switching Power Supply, this Switching Power Supply has designed the circuit that absorbs spike, and introduces two feedbacks and relatively carry out voltage stabilizing with reference voltage.

The technical scheme that its technical problem that solves the utility model adopts is: absorb the circuit of spike in the design of the two ends of switch, make that the spike that produces in the circuit is effectively absorbed.Adopt a photoisolator that input signal is introduced control circuit at the output of stabilized voltage power supply, compare voltage stabilizing with the reference voltage of control circuit.End at control circuit is introduced a feedback voltage, and the feedback voltage of introducing with photoisolator one works, and relatively and after the difference amplification with the two delivers to pulse modulated circuit with reference voltage, and the duty ratio of impulse waveform is changed.This pulse signal the time scale of adjusting the pipe conducting and ending is also changed thereupon, thereby average value of output voltage remains unchanged after making filtering as the input signal of switch adjustment pipe.

The beneficial effects of the utility model are, can suppress spike and disturb, and the common voltage stabilizing of two feedback signals and reference voltage makes the stable fine of whole power supply, and output voltage is very stable.

Description of drawings:

Below in conjunction with drawings and Examples the utility model is further specified.

Fig. 1 is circuit theory diagrams of the present utility model.

Fig. 2 is the switching power supply block diagram.

The inner theory diagram of Fig. 3 UC3842.

Fig. 4 TIL117 photoisolator line map

Embodiment

In Fig. 1, input voltage is through the bridge-type high-voltage rectifying, and R1 and C1 filtering directly are rectified into direct voltage, and direct voltage provides the cut-in voltage of a 16V to control chip UC3842 through divider resistance R2 step-down, control circuit is started working, and this direct voltage is as the supply voltage of metal-oxide-semiconductor simultaneously.Switching tube under the control circuit effect, the time and during conducting and end, so direct voltage is become ac square wave.Chopping voltage can obtain required direct voltage after the secondary rectification.C2, C3 carries out overcurrent protection, and R11, C8, D2 and C9, R12, D4 form two symmetrical structures respectively in order to absorb the spike that produces in the circuit.MOS source resistance R9 is the overcurrent sampling resistor.When overcurrent, U _R9Increase, through R ₁₀3 ends of delivering to UC3842 are to realize the purpose of overcurrent protection.The N1 circle of serving as theme, N2, N3 are secondary coil.D3, C10 constitutes the lower pressure rectifier filter circuit, N3, D3, C10 constitutes output circuit.Output signal is through the R13 step-down, after the D5 voltage stabilizing by feeding back to the control circuit end behind the photoisolator TIL117.R3 draws back one tunnel feedback signal and also feeds back to the control circuit end.N type metal-oxide-semiconductor is as switching circuit, and other circuit is the peripheral protective circuit of control chip UC3842.

In Fig. 2, at first, input voltage directly is rectified into direct voltage without the power transformer step-down.This direct voltage is as the supply voltage of switching tube V.Switching tube under the control circuit effect, the time and end during conducting, so again direct voltage " copped wave " is become ac square wave (Here it is DC → AC, promptly so-called inverter).Chopping frequency is generally tens～hundreds of KHz.Chopping voltage through a high frequency small transformers isolate, step-down, and after the secondary rectification, can obtain required direct voltage.Voltage stabilizing mechanism depends on negative feedback, output voltage U ₀After the dividing potential drop, arrive the error amplifier end of oppisite phase through optical coupling (isolation), after relatively amplifying with the in-phase end reference voltage, the input of an output comparator C.The output of another termination triangular wave oscillator of comparator C, the two obtains the identical and impulse wave of EDM Generator of Adjustable Duty Ratio of frequency after relatively.This impulse wave adds to the power MOS pipe grid, with the conducting of control MOS and deadline ratio, thereby the mean value of control transformer output AC waveform finally reaches the purpose of voltage stabilizing.

In Fig. 3, design circuit selects for use UC3842 chip UC3842 to adopt the controlled modulation system of steady job frequency pulse width, have 8 pins, each pin function is as follows: 1. pin is the output of error amplifier, and external resistor and capacitor component is used to improve the gain and the frequency characteristic of error amplifier; 2. pin is the feedback voltage input, and the 2.5V reference voltage of this pin voltage and error amplifier in-phase end compares, and produces error voltage, thus the control impuls width; 3. pin is the current detecting input, dwindles pulse duration and make power supply be in the discontinuous operation state when detecting voltage above 1V; 4. pin is regularly an end, and the operating frequency of internal oscillator is by external capacity-resistance time constant decision, and f=1.8/ (RT * CT); 5. pin is a common; 6. pin is for recommending output, and inside is the totem pillar, rises, only for the 50ns driving force be ± 1A fall time; 7. pin is the DC power supply end, have owe, the over-voltage locking function, chip power-consumption is 15mW; 8. pin is the 5V reference voltage output end, and the load capacity of 50mA is arranged.

In Fig. 4, the photoisolator transmission signals adopts photoelectricity transformation principle, signal input part (primary side) and signal is received and output (primary side) realization electric insulation.Therefore, can eliminate noise signal in the input circuit, altogether land clutter etc. disturbs the signal of output loop, realize direct current signal to exchange or pulse signal between transmission.The TIL117 photoisolator is one tunnel outputs of biserial 6 pin, and the electric principle of its transmission signals as shown in figure 11.D ₁Pass through electric current I _FAfter, just send infrared light, T ₂Be subjected to produce electric current I after the optical excitation _cThereby, at R _LLast generation pressure drop V _o, primary side and secondary side are that electricity is isolated fully, and I _cBe worth too little and I _FRelevant.

Claims

1. Switching Power Supply, the filtering of input voltage process high-voltage rectifying, switch change-over, through voltage of lower pressure rectifier filtering output, the design sample circuit is taken a sample to output again, feed back to control circuit and adjust switch transformed circuit, make output voltage stabilization, it is characterized in that adopting optical isolation to sample, adopt the different feedback signal of two-way to control control circuit jointly to control circuit, increase the circuit that absorbs spike, reach the voltage stabilizing purpose.

2. Switching Power Supply according to claim 1, it is characterized in that: adopt optical isolation TIL117 to sample, employing is introduced two-way feedback signal control control circuit from output and control circuit end, utilizes diode and resistance, and electric capacity constitutes the circuit that absorbs spike.