CN207677637U - A kind of primary side feedback circuit - Google Patents

Abstract

The utility model discloses a kind of primary side feedback circuits, including power supply chip PWM, the 1 series resistor R9 of pin of the power supply chip PWM is electrically connected with the grid of field-effect tube Q1, the drain series resistor R2 ground connection of field-effect tube Q1, the drain of field-effect tube Q1 connects the ports D of the primary side winding N1 of transformer T1, and the pin 2 of power supply chip PWM is sequentially connected in series diode ZD1, resistance R7 and resistance R6 and is electrically connected with the C-terminal mouth of the primary side winding N1 of transformer T1.The rectifier diode D30 conductings of this primary side feedback circuit discharge the flux being stored in transformer T1, by the filtering of capacitance C31, obtain steady dc voltage；A voltage part on capacitance C1 is charged by resistance R3 current limlitings to capacitance C3 again, the VCC power supplies of power supply source chip PWM, to reach energy-efficient purpose；The whole control that can be achieved to output voltage, energy saving, height when control accuracy relatively has feedback winding, circuit is simple and reliable, and the volume of product further decreases, and electronic component is realized integrated.

Description

A kind of primary side feedback circuit

Technical field

The utility model is related to electronic circuit technology field, specially a kind of primary side feedback circuit.

Background technology

In the small power switches such as LED driver, modular power source, charger source, it is anti-that basic circuit, which opens up general structural circuit, Swash formula circuit, is not there are many chips that no optocoupler may be implemented now under very high requirement for output voltage precision Output voltage is controlled, and control accuracy can be realized substantially 3% hereinafter, Fig. 2 is exactly typical primary side feedback circuit, Output voltage precision may be implemented in 3% hereinafter, in fig. 2, the size for adjusting output voltage be by feedback winding N3 and it is secondary around The coupling of group N2, resistance R4 and resistance R5 will give IC feedback port FB after N3 windings partial pressure, come what is realized；Diode D1, resistance R1 and capacitance C1 form absorbing circuit, by the leakage inductance between the primary side winding N1 and secondary windings N2 of transformer T1 when Q1 is turned off The peak absorbing of generation falls；The relationship of output voltage FB and output voltage Vo are as follows：Vo=VFB*(1+R4/R5)*(N2/N3）, N2/N3 is the turn ratio between winding N2, N3, and in this formula, the voltage of VFB is high-frequency signal, is substantially by secondary windings N2 high Frequency voltage signal is coupled to feedback winding N3, and feedback winding N3 divides to obtain a high-frequency signal again by resistance R4 and resistance R5 Voltage Vo1 is compared with VFB, carries out duty cycle adjustment to control PWM IC, output voltage size is adjusted to reach Purpose only has high-frequency ac composition, without direct current part in this formula in Vo1；Therefore it is had a disadvantage that in Fig. 2 circuits：1, Coupling size between feedback winding and secondary windings can influence output voltage precision, and this improves the technological requirement of transformer It is very high, the production cost of production transformer can be increased in this way；2, more windings can increase the Material Cost for depressor；3 are difficult to The miniaturization for realizing transformer, because of a more winding technique, it is necessary to need transformer have larger window area could around going down, This allows for transformer and miniaturises；4, the peak absorbing generated when Q1 is turned off, which falls, to be inhaled by resistance R1, capacitance C1 It receives and generates heat and lose；To solve the above problems, therefore needing a kind of primary side feedback circuit.

Utility model content

The purpose of this utility model is to provide a kind of primary side feedback circuit, has and can be achieved with pair without feedback winding N3 The control of output voltage, energy saving, height when control accuracy relatively has feedback winding, circuit is simple and reliable, and the volume of product further subtracts It is small, integrated advantage is realized for electronic component, solves output voltage precision susceptible in the prior art, production cost Height, volume is big, the big problem of energy loss.

To achieve the above object, the utility model provides the following technical solutions：A kind of primary side feedback circuit, including power supply core The 1 series resistor R9 of pin of piece PWM, the power supply chip PWM are electrically connected with the source electrode of field-effect tube Q1, the grid of field-effect tube Q1 Grade series resistor R2 ground connection, the drain of field-effect tube Q1 connect the ports D of the primary side winding N1 of transformer T1, power supply chip PWM's Pin 2 is sequentially connected in series diode ZD1, resistance R7 and resistance R6 and is electrically connected with the C-terminal mouth of the primary side winding N1 of transformer T1, resistance The input terminal series diode D2 and resistance R3 of R6 is electrically connected with the output end of diode ZD1, the input terminal concatenation of diode D2 Capacitance C1 ground connection, the output end of resistance R3 are sequentially connected in series the ends D of the primary side winding N1 of resistance R1 and diode D1 and transformer T1 Mouth electrical connection；The ports D of the primary side winding N1 of the transformer T1 are sequentially connected in series resistance R4, resistance R5 and capacitance CY1 and transformation The ports B of the primary side winding N2 of device T1 are electrically connected, and the output end of the output termination capacitor C4 and resistance R5 of resistance R4 simultaneously connect；It is described The ports B of the primary side winding N2 of transformer T1 meet leading-out terminal-Vout, and the ports the A concatenation of the primary side winding N2 of transformer T1 is whole Stream diode D30 meets input terminal+Vout, the input termination capacitor C35 and resistance R9 and rectifier diode of rectifier diode D30 The output end of D30 is in parallel, and the ports B of the primary side winding N2 of the output termination capacitor C31 and transformer T1 of rectifier diode D30 are simultaneously Connection.

Preferably, the pin 3 of the power supply chip PWM concatenates the input terminal of subtracter and resistance R5 and connects, resistance R7's Output termination input signal Vin is electrically connected with subtracter.

Preferably, it the input terminal of the input termination capacitor C3 and diode ZD1 of the resistance R3 and connects.

Compared with prior art, the beneficial effects of the utility model are as follows：

For this primary side feedback circuit when rectifier diode D30 cut-offs are not turned on, energy storage is in transformer T1, rectification two Pole pipe D30 conductings, the flux being stored in transformer T1 is discharged, by the filtering of capacitance C31, obtains stable DC Pressure obtains a direct current after field-effect tube Q1 shutdowns by sending to capacitance C1 to be filtered peak voltage by resistance R1 Voltage, the voltage part on capacitance C1 give capacitance C3 to charge by resistance R3 current limlitings again, the VCC power supplies of power supply source chip PWM, To reach energy-efficient purpose；Whole to can be achieved with the control to output voltage without feedback winding N3, energy saving, control accuracy is high, Circuit is simple and reliable, and the volume of product further decreases, and electronic component is realized integrated.

Description of the drawings

Fig. 1 is the circuit diagram of the utility model；

Fig. 2 is the typical primary side feedback circuit diagram of the utility model.

Specific implementation mode

The following will be combined with the drawings in the embodiments of the present invention, carries out the technical scheme in the embodiment of the utility model Clearly and completely describe, it is clear that the described embodiments are only a part of the embodiments of the utility model, rather than whole Embodiment.Based on the embodiments of the present invention, those of ordinary skill in the art are without making creative work The every other embodiment obtained, shall fall within the protection scope of the present invention.

Referring to Fig. 1, a kind of primary side feedback circuit, including the pin 1 of power supply chip PWM, the power supply chip PWM concatenate Resistance R9 is electrically connected with the source electrode of field-effect tube Q1, the grid grade series resistor R2 ground connection of field-effect tube Q1, the leakage of field-effect tube Q1 Grade connects the ports D of the primary side winding N1 of transformer T1, the pin 2 of power supply chip PWM be sequentially connected in series diode ZD1, resistance R7 and Resistance R6 is electrically connected with the C-terminal mouth of the primary side winding N1 of transformer T1, the input terminal series diode D2 and resistance R3 of resistance R6 It is electrically connected with the output end of diode ZD1, the input terminal serial capacitance C1 ground connection of diode D2, the output end of resistance R3 is gone here and there successively Connecting resistance R1 and diode D1 is electrically connected with the ports D of the primary side winding N1 of transformer T1；The primary side winding of the transformer T1 The ports D of N1 are sequentially connected in series resistance R4, resistance R5 and capacitance CY1 and are electrically connected with the ports B of the primary side winding N2 of transformer T1, electricity It hinders the output end of the output termination capacitor C4 and resistance R5 of R4 and connects；The ports B of the primary side winding N2 of the transformer T1 connect defeated Go out terminal-Vout, the ports the A concatenation rectifier diode D30 of the primary side winding N2 of transformer T1 connects input terminal+Vout, rectification The input termination capacitor C35 and resistance R9 of diode D30 is in parallel with the output end of rectifier diode D30, rectifier diode D30's It is in parallel with the ports B of primary side winding N2 of transformer T1 to export termination capacitor C31；The pin 3 of power supply chip PWM concatenates subtracter With the input terminal of resistance R5 and connect, the output termination input signal Vin of resistance R7 is electrically connected with subtracter, power supply chip PWM's Pin 3 concatenates the input terminal of subtracter and resistance R5 and connects, and the output termination input signal Vin of resistance R7 is electrically connected with subtracter It connects；The input terminal of the input termination capacitor C3 and diode ZD1 of resistance R3 simultaneously connect；Primary side feedback circuit scene effect pipe Q1 is opened When logical, input terminal voltage anode by the primary side winding N1 of transformer T1 to input terminal, the primary side winding of transformer T1 at this time The D port voltages that N1 is connected with field-effect tube Q1 drain electrodes are cathode, and similarly the ports A of the primary side winding N2 of transformer T1 are also negative Pole, so rectifier diode D30 cut-offs, are not turned on, energy is stored in transformer T1, when scene effect pipe Q1 is turned off, is become The port voltage that the primary side winding N1 of depressor T1 is connected with field-effect tube Q1 is anode, similarly the primary side winding N2 of transformer T1 The ports A are also anode, and the flux being stored in transformer T1 is discharged, passes through the filter of capacitance C31 by rectifier diode D30 conductings Wave, obtains steady dc voltage, after field-effect tube Q1 shutdowns, due to the presence of leakage inductance, in the drain electrode of scene effect pipe Q1 Being exactly ports D on N1 windings has larger peak voltage, while the voltage of the ports D is anode, so diode D1 conductings, by this Peak voltage, send to capacitance C1 to be filtered and obtains a DC voltage by resistance R1, the voltage part on capacitance C1 It is charged again to capacitance C3 by resistance R3 current limlitings, the VCC power supplies of power supply source chip PWM, to reach energy-efficient purpose；Pass through increase Subtracter so that at work, D port voltages are VD=Vo* (N2/N1）What+Vin, resistance R4 and resistance R5 carried out dividing extremely Vo2 has N2/N1+ dc component Vin, and for radio-frequency component, dc component Vin signals are 0, so Vo={ VFB* (1+R4/ R5)-Vin } * (N1/N2)；Whole to can be achieved with the control to output voltage without feedback winding N3, energy saving, control accuracy relatively has High when feedback winding, circuit is simple and reliable, and the volume of product further decreases, and electronic component is realized integrated.

In summary：When this primary side feedback circuit scene effect pipe Q1 is opened, input terminal voltage anode passes through transformer T1 Primary side winding N1 to input terminal, the ports D that the primary side winding N1 of transformer T1 is connected with field-effect tube Q1 drain electrode at this time are electric Pressure is cathode, and similarly the ports A of the primary side winding N2 of transformer T1 are also cathode, so rectifier diode D30 cut-offs, do not lead Logical, energy is stored in transformer T1, when scene effect pipe Q1 is turned off, the primary side winding N1 and field-effect tube Q1 of transformer T1 Connected port voltage is anode, and similarly the ports A of the primary side winding N2 of transformer T1 are also anode, and rectifier diode D30 is led It is logical, the flux being stored in transformer T1 is discharged, by the filtering of capacitance C31, obtains steady dc voltage, field-effect tube After Q1 shutdowns, due to the presence of leakage inductance, there are larger spike electricity in the ports D in the drain electrode of scene effect pipe Q1 namely on N1 windings Pressure, while the voltage of the ports D is anode, so diode D1 conducting, by this peak voltage, by resistance R1 send to capacitance C1 into Row filtering obtains a DC voltage, and the voltage part on capacitance C1 is charged by resistance R3 current limlitings to capacitance C3 again, is supplied The VCC of power supply chip PWM powers, to reach energy-efficient purpose；By increasing subtracter so that at work, D port voltages are VD=Vo*(N2/N1）The Vo2 that+Vin, resistance R4 and resistance R5 carry out dividing extremely has N2/N1+ dc component Vin, for high frequency For ingredient, dc component Vin signals are 0, so Vo={ VFB* (1+R4/R5)-Vin } * (N1/N2)；It is whole without feedback around Group N3 can be achieved with the control to output voltage, energy saving, and height when control accuracy relatively has feedback winding, circuit is simple and reliable, product Volume further decrease, for electronic component realize it is integrated.

While there has been shown and described that the embodiments of the present invention, for the ordinary skill in the art, It is appreciated that can these embodiments be carried out with a variety of variations in the case where not departing from the principles of the present invention and spirit, repaiied Change, replace and modification, the scope of the utility model are defined by the appended claims and the equivalents thereof.

Claims (3)

1. a kind of primary side feedback circuit, including power supply chip PWM, it is characterised in that：The pin 1 of the power supply chip PWM concatenates Resistance R9 is electrically connected with the source electrode of field-effect tube Q1, the grid grade series resistor R2 ground connection of field-effect tube Q1, field-effect tube Q1's Drain connects the ports D of the primary side winding N1 of transformer T1, and the pin 2 of power supply chip PWM is sequentially connected in series diode ZD1, resistance R7 It is electrically connected with the C-terminal mouth of the primary side winding N1 of transformer T1 with resistance R6, the input terminal series diode D2 and resistance of resistance R6 R3 is electrically connected with the output end of diode ZD1, and the input terminal serial capacitance C1 ground connection of diode D2, the output end of resistance R3 is successively Series resistor R1 and diode D1 is electrically connected with the ports D of the primary side winding N1 of transformer T1；The primary side of the transformer T1 around The ports D of group N1 are sequentially connected in series resistance R4, resistance R5 and capacitance CY1 and are electrically connected with the ports B of the primary side winding N2 of transformer T1, The output end of the output termination capacitor C4 and resistance R5 of resistance R4 simultaneously connect；The ports B of the primary side winding N2 of the transformer T1 connect The ports the A concatenation rectifier diode D30 of the primary side winding N2 of leading-out terminal-Vout, transformer T1 meet input terminal+Vout, whole The input termination capacitor C35 and resistance R9 for flowing diode D30 are in parallel with the output end of rectifier diode D30, rectifier diode D30 Output termination capacitor C31 it is in parallel with the ports B of primary side winding N2 of transformer T1.

2. a kind of primary side feedback circuit according to claim 1, it is characterised in that：The pin 3 of the power supply chip PWM is gone here and there It connects the input terminal of subtracter and resistance R5 and connects, the output termination input signal Vin of resistance R7 is electrically connected with subtracter.

3. a kind of primary side feedback circuit according to claim 1, it is characterised in that：The input termination capacitor of the resistance R3 The input terminal of C3 and diode ZD1 simultaneously connects.