CN217590623U

CN217590623U - Converter

Info

Publication number: CN217590623U
Application number: CN202221294645.7U
Authority: CN
Inventors: 江庆饶
Original assignee: Mornsun Guangzhou Science and Technology Ltd
Current assignee: Mornsun Guangzhou Science and Technology Ltd
Priority date: 2022-05-26
Filing date: 2022-05-26
Publication date: 2022-10-14
Anticipated expiration: 2032-05-26

Abstract

The utility model provides a converter, the converter includes controller, first blocking capacitor and transformer, the controller is connected between input voltage and the transformer, the first blocking capacitor is connected with the primary winding of the transformer; the converter further comprises a second blocking capacitor, one end of the second blocking capacitor is connected with the input voltage, and the other end of the second blocking capacitor is connected with one end of the first blocking capacitor and one end of the primary winding of the transformer respectively. The problem that output voltage is reduced due to the fact that input capacitance is increased can be solved at low cost, the capacitor with the large size and the high withstand voltage value and the capacitor value does not need to be selected, and the low-cost product has the advantages of small size and low cost.

Description

Converter

Technical Field

The utility model relates to a switching power supply field, more specifically the utility model relates to a converter.

Background

In recent years, the requirement for isolation voltage is higher and higher, and for industries such as IGBT, photovoltaic power supply, medical power supply and the like, the isolation voltage needs to reach 5000VAC and above. One of the limitations of the isolation voltage is the winding of the transformer, and if the requirement of the transformer on the isolation voltage is high, the distance between the input and output windings needs to be increased, so that the leakage flux is increased, that is, the leakage inductance of the transformer is increased. For an integrated PWM controller, a large leakage inductance transformer can cause large leakage inductance spikes, resulting in controller anomalies. In the application of the controller, how to reduce or even eliminate the influence of leakage inductance, some engineers may consider using the leakage inductance of the transformer as the resonant inductance in the LLC half-bridge converter to participate in resonance, so that on a micropower high isolation product, an open-loop fixed-frequency LLC half-bridge topology may be used, and thus the problem of large leakage inductance of the transformer will not influence the integrated controller.

Fig. 1 shows a conventional open-loop fixed-frequency LLC half-bridge topology, wherein an internal block diagram of a controller is shown in fig. 2, and for convenience of description, a leakage inductance of a transformer T1 is denoted by Lk and is labeled in the figure.

LLC resonant converters are generally in PFM control mode, i.e. the output voltage is regulated by changing the frequency, resulting in a stable output voltage. The primary side leakage inductance and the primary side inductance of the transformer T1 and the impedance of the blocking capacitor C3 are respectively as follows:

therefore, the relationship between the output voltage Vo and the impedances of the three is

It can be seen that the output voltage Vo varies with the frequency. In the case of open loop applications, the frequency is directly fixed, allowing the output to vary with the input voltage, so that the controller can also use a transformer with large leakage inductance.

However, the controller has two problems: 1. when the input capacitance increases, the output voltage decreases. 2. The indexes such as load regulation rate, efficiency and the like are poor, the performance of discrete devices is good, and an integrated controller is not dominant.

In addition, because the DC/DC power supply is a secondary power supply, the output capacitance of the primary power supply can directly influence the voltage precision of the secondary power supply, thereby leading to input under-voltage protection of a rear-end device or output overvoltage, and damaging a rear-stage device. This problem can be solved by adding an input capacitance, but there is a problem: the capacitor with high capacity and high withstand voltage has high cost and large volume, which has no advantage in the DC/DC micropower power supply product with small volume, and the problem of poor performance of the controller in the problem 2 can not be solved.

SUMMERY OF THE UTILITY MODEL

The utility model discloses aim at overcoming at least one kind defect among the above-mentioned prior art, provide a converter to thereby solve the increase of input capacitance and lead to output voltage to descend, and the relatively poor problem of indexes such as current converter load adjustment rate and efficiency.

In order to achieve the above purpose, the utility model adopts the following technical scheme:

a converter comprises a controller, a first blocking capacitor and a transformer, wherein the controller is connected between an input voltage and the transformer, and the first blocking capacitor is connected with a primary winding of the transformer; the converter further comprises a second blocking capacitor, one end of the second blocking capacitor is connected with the input voltage, and the other end of the second blocking capacitor is connected with one end of the first blocking capacitor and one end of the primary winding of the transformer respectively.

Preferably, the converter further includes an input capacitor, one end of the input capacitor is connected to the input voltage, and the other end of the input capacitor is connected to a ground terminal.

Preferably, one end of the first dc blocking capacitor is connected to the primary winding of the transformer, and the other end of the first dc blocking capacitor is connected to a ground terminal.

Preferably, the controller is a controller of an integrated half-bridge circuit.

Preferably, the controller is a controller of an integrated full bridge circuit.

The working principle of this application will combine specific implementation mode to carry out detailed analysis, and no longer give unnecessary details here, and the beneficial effect of this application is as follows: only one blocking capacitor is added between the input voltage of the converter and the first blocking capacitor, so that the problem that the output voltage changes along with the input capacitor is solved, and the product performance is greatly improved.

Drawings

FIG. 1 is a schematic diagram of a prior art half-bridge converter;

FIG. 2 is an internal schematic diagram of a prior art half-bridge converter;

fig. 3 is a schematic diagram of a converter provided by the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and the following detailed description. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 2 to 3, a converter applied to the field of switching power supplies includes: the device comprises a controller IC1, an input capacitor C, a first blocking capacitor C1, a second blocking capacitor C2 and a transformer T1; one end of the input capacitor C is connected with the input voltage Vin, and the other end of the input capacitor C is connected with the ground end GND; one end of the first blocking capacitor C1 is respectively connected with one end of the second blocking capacitor C2 and the synonym end of the primary winding of the transformer T1, and the other end of the first blocking capacitor C1 is respectively connected with the power supply end of the controller IC1 and the ground end GND; one end of a second blocking capacitor C2 is respectively connected with the input voltage Vin and the input end of the controller IC1, and the other end of the second blocking capacitor C2 is respectively connected with the first blocking capacitor C1 and the synonym end of the primary winding of the transformer T1;

a half-bridge circuit composed of a first MOS tube MN1 and a second MOS tube MN2 and a circuit for providing drive control for the first MOS tube MN1 and the second MOS tube MN2 are integrated in the controller IC 1; the drain electrode of the first MOS tube MN1 is respectively connected with one end of the input voltage Vin, the input capacitor C and the second blocking capacitor C2, and the source electrode of the first MOS tube MN1 is respectively connected with the drain electrode of the second MOS tube MN2 and the homonymous end of the primary winding of the transformer T1; the drain electrode of the second MOS tube MN2 is connected with the dotted terminal of the primary winding of the transformer T1, and the source electrode is respectively connected with the first blocking capacitor C1 and the grounding terminal GND.

The internal clock of the controller IC1 provides a complementary driving signal with a fixed frequency to the first MOS transistor MN1 and the second MOS transistor MN2, and there is a certain dead time to prevent the two transistors from being shared, and the specific working process of the controller IC1 is described below.

When the first MOS transistor MN1 is turned on and the second MOS transistor MN2 is turned off, the input capacitor C charges the first blocking capacitor C1 through the leakage inductance Lk and the inductor Lp, at this time, the voltage on the first blocking capacitor C1 rises, the voltage on the input capacitor C falls, the leakage inductance Lk and the inductor Lp are excited, and the current linearly rises. When the first MOS transistor MN1 is turned off and the second MOS transistor MN2 is turned on, the input voltage Vin charges the input capacitor C,the input capacitance C voltage rises. At this time, the current of the inductor Lp decreases linearly, the leakage inductor Lk and the first dc blocking capacitor C1 discharge in resonance, and the voltage on the first dc blocking capacitor C1 continuously decreases. Therefore, the output voltage varies according to the voltage variation of the leakage inductance Lk and the first dc blocking capacitor C1. Since the parameters of the transformer T1 are fixed, and the parameters of the leakage inductance Lk and the inductance Lp cannot be changed, when the capacitance value of the input capacitor C is too large, and the input capacitor C charges the first dc blocking capacitor C1 during the conduction period of the first MOS transistor MN1, the charge stored in the first dc blocking capacitor C1 increases. According to the formula Q = U × C, the voltage across the first blocking capacitor C1 increases during charging and discharging of the first blocking capacitor C1. According to formula V _in ＝V _Lp +V _Lk +V _C3 Since the voltage of the input voltage Vin is not changed, and the voltage of the first dc blocking capacitor C1 is increased, the voltage across the primary winding inductor Lp is decreased, and the output voltage is decreased.

Since the controller IC1 outputs a complementary signal with a fixed frequency, the output voltage cannot be adjusted by adjusting the frequency, and the most direct method for stabilizing the output voltage is to increase the capacitance of the input capacitor C. When the capacitance value of the input capacitor C is smaller, the voltage on the first blocking capacitor C1 is larger in fluctuation, and the average value changes, so that the output voltage changes along with the change of the input capacitor C; when the capacitance value of the input capacitor C1 is large, the voltage fluctuation on the first blocking capacitor C1 is small, the average value is basically unchanged, and therefore the output voltage is also unchanged.

On the other hand, increasing the capacitance of the input capacitor C means that the volume and cost of the input capacitor C will increase, and the withstand voltage will also decrease. Once the withstand voltage value of the input capacitor C is reduced, the range of the input voltage is narrowed, which is disadvantageous for the product.

From the above operation, the output voltage is mainly affected by the voltage on the first dc blocking capacitor C1. When the load at the output end is heavy, the current I is reflected to the primary side according to the turn ratio of the transformer, and the current I equivalent to the charging and discharging of the first blocking capacitor C1 is increased. According to the formula Q = I × T = U × C, the current I of the first blocking capacitor C1 directly affects the change of the voltage U of the first blocking capacitor C1, so that the amplitude of the voltage of the first blocking capacitor C1 increases as the current I of the first blocking capacitor C1 increases. Therefore, when the load is heavy-load or light-load, the output voltage difference between the two is very large, that is, the load regulation rate of the product is very poor.

Based on this, the utility model provides a converter can not receive too much restriction when choosing input capacitance's appearance value, and can effectual stable output voltage, promotes and produces property ability.

By analyzing the specific working process of the controller IC1, it can be seen that the main factor influencing the output voltage is the change of the voltage on the first dc-blocking capacitor C1. And the utility model discloses direct connect into a blocking electric capacity in input voltage Vin department, also establish ties first blocking electric capacity C1 and second blocking electric capacity C2, according to electric capacity series connection partial pressure principle, the voltage on the first blocking electric capacity C1 will distribute on first blocking electric capacity C1 and second blocking electric capacity C2. According to the formula

The voltage across the first dc blocking capacitor C1 is clamped by the input voltage Vin via the second dc blocking capacitor C2, so that the output voltage does not change with the change of the input capacitor C. When the load is switched, the output voltage change is also reduced, so that the load regulation rate of the product is improved.

After the second blocking capacitor C2 is added, the limitation of the input capacitor C is reduced, and the problem that the output voltage changes along with the input capacitor C1 is solved without a capacitor with a large capacitance value and high withstand voltage. At this time, the input capacitor C1 is only used as a filter capacitor, and does not affect the output voltage any more.

Compared with the product using the prior art, the product adopting the technical scheme has the following test data:

index (I)	Original scheme	Adopt the utility model
			Efficiency/%)	79.51	84.0
ripple/mV	334	200
			Load adjustment rate/%)	15.0	8.9

It can be seen from the table that, the product that adopts this technical scheme, not only output voltage is more stable, and indexes such as efficiency, ripple and load adjustment rate of product have all obtained great promotion moreover.

It will be appreciated by those skilled in the art that the invention can be embodied in other specific forms without departing from the spirit or essential attributes thereof. The embodiments disclosed above are therefore to be considered in all respects as illustrative and not restrictive. All changes that come within the scope of or equivalence to the scope of this application are intended to be embraced therein.

Claims

1. A converter comprises a controller, a first blocking capacitor and a transformer, wherein the controller is connected between an input voltage and the transformer, the first blocking capacitor is connected with a primary winding of the transformer, and the converter is characterized in that: the converter further comprises a second blocking capacitor, one end of the second blocking capacitor is connected with the input voltage, and the other end of the second blocking capacitor is connected with one end of the first blocking capacitor and one end of a primary winding of the transformer respectively.

2. The converter of claim 1, wherein: the input capacitor is connected with the input voltage at one end and connected with a grounding end at the other end.

3. The converter of claim 1, wherein: one end of the first blocking capacitor is connected with the primary winding of the transformer, and the other end of the first blocking capacitor is connected with the grounding end.

4. The converter of claim 1, wherein: the controller is a controller of an integrated half-bridge circuit.

5. The transducer of claim 1, wherein: the controller is a controller of an integrated full-bridge circuit.