Switching power supply circuit for stable output of non-control output circuit

Abstract

The utility model discloses a switching power supply circuit with stable output of a non-control output circuit. The circuit structure comprises an AC input circuit, an EMI rectification filter circuit, a power transformer circuit, a PWM control output circuit, a non-control output circuit, a PWM regulation control circuit and a load switching circuit. According to the switching power supply circuit with stable output of the non-control output circuit, the load switching circuit is designed, so that the whole switching power supply not only can meet the requirement of no-load power consumption and energy efficiency, but also can meet the requirement of stable output of the non-control output circuit when the PWM control output circuit is in a no-load state, and the switching power supply circuit has very strong load capacity; the problem that the voltage of a non-PWM control output circuit cannot be adjusted due to the fact that a feedback mechanism has problems in multi-path output is solved, and the on-load function and practicability of the multi-path output switching power supply are enhanced. And under the condition of no isolation requirement among multipath outputs, the circuit design is simpler and more reliable, and the manufacturing cost can be reduced.

Description

TECHNICAL FIELD

[0001] The utility model belongs to switching power supply technical field, specifically relates to a kind of switching power supply circuit of non-control output circuit stable output. BACKGROUND

[0002] Multi-output switching power supply, only one output participates in primary PWM control, and the other several outputs do not participate in control. Due to the requirement of no-load power consumption, a dummy load cannot be added to the output end, so when the output of the primary PWM control does not carry a load, and the other several outputs carry a load, the output voltage will drop out of the specification requirement. Because the multi-output switching power supply usually only stabilizes the main output, the PWM controller can only accept one feedback signal. If the other outputs do not participate in control, their voltage regulation depends on the load condition of the main output. When the main output is unloaded, and the other outputs are loaded, the main output may not be able to provide sufficient feedback, resulting in unstable voltage of the other outputs. Therefore, the problem of multi-output is that the feedback mechanism of the main output cannot adjust the voltage of the other output circuits. The multi-output switching power supply can be replaced by one power supply instead of multiple single-output power supplies, reducing material cost and installation complexity, so it is necessary to design a multi-output switching power supply with non-control output circuit carrying load, and in the case of no isolation requirement between multi-output, the circuit design is as simple and reliable as possible. SUMMARY

[0003] The utility model aims at the above problem, provides a kind of switching power supply circuit of non-control output circuit stable output, so that the non-control output circuit of multi-output switching power supply can also carry load, enhance the function and practicality of multi-output switching power supply, and in the case of no isolation requirement between multi-output, the circuit design is as simple and reliable as possible.

[0004] The utility model is realized by the following technical solutions:

[0005] A kind of switching power supply circuit of non-control output circuit stable output, characterized by: its circuit structure includes AC input circuit, EMI rectification filter circuit, power transformer circuit, PWM control output circuit, non-control output circuit, PWM regulation control circuit and load switching circuit.

[0006] The output end of the AC input circuit is connected to an EMI rectification filter circuit, the positive output end of the EMI rectification filter circuit is connected to the positive end of the primary first winding of a power transformer T1 of a power transformer circuit, the negative end of the primary first winding is connected to the PWM control chip U1 of the PWM regulation control circuit; the primary second winding of the power transformer T1 provides working voltage for the PWM control chip U1 of the PWM regulation control circuit. The output of the secondary first winding of the power transformer T1 of the power transformer circuit is connected to the PWM control output circuit, the output of the secondary second winding of the power transformer T1 is connected to the non-control output circuit; the output of the PWM control output circuit inputs feedback signal to the feedback input end of the PWM control chip U1 of the PWM regulation control circuit through the optocoupler chip U4; the non-control output circuit comprises a voltage stabilizing chip U3, the voltage input end of the chip U3 is connected to the output end of the secondary second winding of the power transformer T1; the load switching circuit is connected between the PWM control output circuit and the non-control output circuit; the load switching circuit comprises transistors Q2 and Q3, and voltage stabilizing diodes Z1 and Z2; the voltage input end of the chip U3 of the non-control output circuit is connected to the base of the transistor Q2 through the series-connected voltage stabilizing diodes Z1 and Z2 and the resistor R38, one way of the collector of the transistor Q2 is connected to the positive output end Vo2 of the non-control output circuit through the resistor R32, the emitter of the transistor Q2 is connected to the signal ground SGND1 of the PWM control output circuit, the other way of the collector of the transistor Q2 is connected to the base of the transistor Q3 through the diode D1, the emitter of the transistor Q3 and the negative end of the non-control output circuit are both connected to the signal ground SGND1 of the PWM control output circuit, and the collector of the transistor Q3 is connected to the positive output end Vo1 through the parallel-connected load resistors R19, R21, R23 and R25; when neither the PWM control output circuit nor the non-control output circuit is connected to a load, the voltage stabilizing diodes Z1 and Z2 are reversely broken down.

[0007] Further, the AC input circuit is provided with the fuse F1 for overcurrent protection and the voltage-dependent resistor MOV1 for lightning protection.

[0008] Further, the voltage stabilizing chip U3 is of the model PL82051.

[0009] Further, the optocoupler chip U4 is of the model EL1019.

[0010] Further, the transistors Q2 and Q3 are both of the model 2222.

[0011] Further, the diode D1 is of the model 4148.

[0012] The utility model discloses a beneficial effect is: the utility model discloses a non -control output circuit steady output's switching power supply circuit, design has load switching circuit, makes whole switching power supply can satisfy no -load power consumption energy efficiency requirement, can satisfy the stable output of non -control output circuit when PWM control output circuit no -load, and has very strong load -carrying capacity;Solved the problem of voltage of non -PWM control output circuit that multiple output can not adjust because of the problem of feedback mechanism, enhanced the load -carrying function and practicality of multiple output switching power supply;And under the condition of no isolation requirement between multiple output, the circuit design is simpler and more reliable, can also reduce the manufacturing cost. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 It is the principle block diagram of the utility model.

[0014] Figure 2 It is the circuit principle diagram of the utility model.

[0015] Figure 3 It is Figure 2 the partial close -up.

[0016] In the drawing, 1, AC input circuit, 2, EMI rectification filter circuit, 3, power transformer circuit, 4, PWM control output circuit, 5, non -control output circuit, 6, PWM regulation control circuit, 7, load switching circuit. DETAILED DESCRIPTION

[0017] The utility model is further described below in combination with specific examples and drawings.

[0018] As Figures 1-3 shown, a kind of non -control output circuit steady output's switching power supply circuit, its circuit structure includes AC input circuit 1, EMI rectification filter circuit 2, power transformer circuit 3, PWM control output circuit 4, non -control output circuit 5, PWM regulation control circuit 6 and load switching circuit 7.

[0019] The alternating current input circuit 1 is provided with a fuse F1 for overcurrent protection and a lightning protection varistor MOV1. The output end of the alternating current input circuit 1 is connected to an EMI rectification filter circuit 2, the positive output end of the EMI rectification filter circuit 2 is connected to the positive end of the primary side first winding of a power transformer T1 of a power transformer circuit 3, the negative end of the primary side first winding is connected to the drain of a MOS tube Q1 of a PWM regulation control circuit 6, the gate of the MOS tube Q1 is connected to the control output pin of a PWM control chip U1 of type KP201E, the source of the MOS tube Q1 is connected to PGND through a resistor R7. The primary side second winding of the power transformer T1 provides working voltage for the chip U1, the positive end of the primary side second winding is connected to the VDD pin of the chip U1 through a diode D7, a resistor R9 and a diode D3. The output of the secondary side first winding of the power transformer T1 of the power transformer circuit 3 is connected to a PWM control output circuit 4, the output of the secondary side second winding of the power transformer T1 is connected to a non-control output circuit 5. The output of the PWM control output circuit 4 inputs a feedback signal to the feedback input end FB pin of the PWM control chip U1 of the PWM regulation control circuit 6 through an optocoupler chip U4, the type of the optocoupler chip U4 is EL1019. The non-control output circuit 5 comprises a voltage reduction stabilizing chip U3, the type of the chip U3 is PL82051, the voltage input end of the chip U3 is connected to the output end of the secondary side second winding of the power transformer T1. The PWM control output circuit 4 and the non-control output circuit 5 are connected with a load switching circuit 7. The load switching circuit 7 comprises a triode Q2, Q3, and stabilizing diodes Z1 and Z2. The triodes Q2 and Q3 are transistors of type 2222. The voltage input end of the chip U3 of the non-control output circuit 5 is connected to the base of the triode Q2 through the series connection of the stabilizing diodes Z1, Z2 and a resistor R38, one way of the collector of the triode Q2 is connected to the positive output end Vo2 of the non-control output circuit 5 through a resistor R32, the resistance value of the resistor R32 is 10KΩ, the emitter of the triode Q2 is connected to the signal ground SGND1 of the PWM control output circuit 4, the emitter and the base of the triode Q2 are connected with a parallel circuit composed of a resistor R35 and a resistor C6, the other way of the collector of the triode Q2 is connected to the base of the triode Q3 through a diode D1, the type of the diode D1 is 4148, the emitter of the triode Q3 and the negative end of the non-control output circuit 5 are both connected to the signal ground SGND1 of the PWM control output circuit 4, the emitter and the base of the triode Q3 are connected with a parallel circuit composed of a resistor R26 and a resistor C12, the collector of the triode Q3 and the positive output end Vo1 are connected with the parallel connection of load resistors R19, R21, R23 and R25, the resistance value of each of the resistors R19, R21, R23 and R25 is 1KΩ.When the PWM control output circuit 4 and the non-control output circuit 5 are not connected with the load, the voltage stabilizing diodes Z1 and Z2 are reversely broken down.

[0020] The existing multi-output switching power supply generally only stabilizes the main output, because the PWM controller can only accept one feedback signal. If other paths do not participate in control, their voltage regulation depends on the load condition of the main output. When the main output is idle and other paths are loaded, the main path may not provide sufficient feedback, resulting in unstable voltage of other paths. And when the main path is not loaded, the PWM controller may reduce the duty cycle to reduce energy transmission, but at this time other paths need energy, but due to the lack of independent feedback, the duty cycle cannot be adjusted, resulting in a decrease in the voltage of other paths. At the same time, due to the inability to add a dummy load, the main path cannot maintain sufficient voltage when it is lightly loaded or idle, further affecting other paths. These factors together cause the voltage of other non-control output circuits to exceed the specification under certain load conditions. The circuit design of the utility model increases the load switching circuit 7 between the PWM control output circuit 4 and the non-control output circuit 5, which can not only meet the energy efficiency requirements of idle power consumption, but also meet the stable output of the non-control output circuit 5 when the PWM control output circuit 4 is idle, and has strong load capacity.

[0021] The working principle is as follows: Figure 2 , Figure 3 The feedback signal of the PWM control output circuit 4 is transmitted to U1 through U2 and U4 to participate in the adjustment of PWM, and the non-control output circuit 5 does not participate in PWM control. When both outputs are not loaded, the voltage stabilizing diodes Z1 and Z2 are broken down, so that the transistor Q2 is turned on and the transistor Q3 is turned off. The parallel load resistors R21, R23, R25 and R19 do not function as a load at this time. Since the resistance value of the R32 resistor (10KΩ) is set to be very large, the idle power consumption of the power supply at this time is very low, meeting the energy efficiency requirements. When the PWM control output circuit 4 is idle and the non-control output circuit 5 is loaded, the voltage input end V1 of the chip U3 of the non-control output circuit 5 will drop at this time. At this time, the voltage stabilizing diodes Z1 and Z2 will not be broken down, so the transistor Q2 is turned off and the transistor Q3 is turned on. In this way, the parallel load resistors R21, R23, R25 and R19 (all with a resistance value of 1KΩ) function as the load of the PWM control output circuit 4, so that the pulse width of PWM is increased (or the frequency of PWM is increased). In this way, the non-control output circuit 5 is stabilized within its rated voltage range.

[0022] The above embodiments are only preferred embodiments of the present application, and are used for explaining the present application, but not limiting the present application. Any change, replacement, combination, simplification, modification and the like made by those skilled in the art without departing from the spirit and principle of the present application should be equivalent replacement mode, and should be included in the protection scope of the present application.

Claims

1. A switching power supply circuit with stable output without control circuitry, characterized in that: The circuit structure comprises an AC input circuit, an EMI rectification filter circuit, a power transformer circuit, a PWM control output circuit, a non-control output circuit, a PWM regulation control circuit and a load switching circuit. The output end of the AC input circuit is connected to the EMI rectification filter circuit, the positive output end of the EMI rectification filter circuit is connected to the positive end of the primary first winding of the power transformer T1 of the power transformer circuit, the negative end of the primary first winding is connected to the PWM regulation control circuit; the primary second winding of the power transformer T1 provides working voltage for the PWM control chip U1 of the PWM regulation control circuit; the output of the secondary first winding of the power transformer T1 of the power transformer circuit is connected to the PWM control output circuit, the output of the secondary second winding of the power transformer T1 is connected to the non-control output circuit; the output of the PWM control output circuit inputs feedback signal to the feedback input end of the PWM control chip U1 of the PWM regulation control circuit through the optocoupler chip U4; the non-control output circuit comprises a voltage reduction and stabilization chip U3, the voltage input end of the chip U3 is connected to the output end of the secondary second winding of the power transformer T1; the load switching circuit is connected between the PWM control output circuit and the non-control output circuit; the load switching circuit comprises transistors Q2 and Q3, and voltage stabilization diodes Z1 and Z2; the voltage input end of the chip U3 of the non-control output circuit is connected to the base of the transistor Q2 through the series-connected voltage stabilization diodes Z1 and Z2 and the resistor R38, one path of the collector of the transistor Q2 is connected to the positive output end Vo2 of the non-control output circuit through the resistor R32, the emitter of the transistor Q2 is connected to the signal ground SGND1 of the PWM control output circuit, the other path of the collector of the transistor Q2 is connected to the base of the transistor Q3 through the diode D1, the emitter of the transistor Q3 and the negative end of the non-control output circuit are both connected to the signal ground SGND1 of the PWM control output circuit, the collector of the transistor Q3 is connected to the positive output end Vo1 through the parallel-connected load resistors R19, R21, R23 and R25; when neither the PWM control output circuit nor the non-control output circuit is connected to a load, the voltage stabilization diodes Z1 and Z2 are reversely broken.

2. The switching power supply circuit of claim 1, wherein: The AC input circuit is provided with the fuse F1 for overcurrent protection and the MOV1 for lightning strike resistance.

3. The switching power supply circuit of claim 1, wherein: The model of the voltage reduction and stabilization chip U3 is PL82051.

4. The switching power supply circuit of claim 1, wherein: The model of the optocoupler chip U4 is EL1019.

5. The switching power supply circuit of claim 1, wherein: The transistors Q2 and Q3 are both 2222 model transistors.

6. The switching power supply circuit of claim 1, wherein: The model of the diode D1 is 4148 diode.

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