CN216414184U - Power converter and current sampling circuit thereof - Google Patents
Power converter and current sampling circuit thereof Download PDFInfo
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- CN216414184U CN216414184U CN202122389454.0U CN202122389454U CN216414184U CN 216414184 U CN216414184 U CN 216414184U CN 202122389454 U CN202122389454 U CN 202122389454U CN 216414184 U CN216414184 U CN 216414184U
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
A power converter and a current sampling circuit thereof are disclosed. The primary winding of the transformer is connected in series in a resonant circuit of the resonant converter in the power converter, and then the secondary winding of the transformer is used for sampling the resonant current so as to adapt to different requirements.
Description
Technical Field
The utility model relates to the technical field of power electronics, in particular to a power converter and a current sampling circuit thereof.
Background
In recent years, users have higher and higher requirements for LED driving power supplies, for example, low harmonic, high PF value, no stroboflash, small size, high efficiency, and low cost, because a conventional bridge rectifier and capacitor filter circuit adopted by a common LED driving power supply can cause serious waveform distortion of AC input current, and a large amount of higher harmonics are injected into a power grid, a power factor at the power grid side is not high, and the large amount of higher harmonics cause serious harmonic pollution and interference to the power grid and other electrical devices, so that the other electrical devices cannot normally operate, and therefore, in order to reduce harmonic interference, a power factor correction circuit (i.e., PFC) is added in the LED driving power supply to increase the power factor in the LED driving power supply, thereby reducing harmonic interference.
As shown in fig. 1, a circuit diagram of a power converter in the prior art is given. The power converter is used for driving the LED and includes an input rectifying module 11, a charge pump PFC module 12, an input filter capacitor C1, and a resonant converter 13. The resonant capacitor Cr, the primary winding Lp and the resonant inductor Lr are connected in series between the charge pump PFC and a middle node HB of the power tubes Q1 and Q2, and a resonant network is formed. The resonant converter 13 further comprises a control circuit for deriving a current sampling signal CS (current sampling signal CS is I) from a sampling resistor Rs connected in series in the resonant networkLrXrs) to generate drive control signals Vgs1 and Vgs2 to drive power transistors Q1 and Q2, respectively. However, the reference ground of the sampling resistor Rs is the intermediate node HB of the power transistors Q1 and Q2 rather than the reference ground GND of the power transistor Q2 (i.e., the reference ground of the input filter capacitor), which makes the design of the control circuit more complicated.
In addition, in the case of dial application, that is, with the function of realizing different output currents by one dial switch, as shown in fig. 2, the variable resistor Rb needs to be connected in parallel to both ends of the sampling resistor Rs, and the variable resistor Rb needs to be led to a proper position by two longer wires. At the moment, the current sampling signal CS is ILrX (Rs// Rb), where "//" denotes parallel. This causes severe EMI because the sampling resistor Rs has one end connected to the intermediate node HB, which is a high voltage trip point, with a steep trip edge.
SUMMERY OF THE UTILITY MODEL
In view of the above, an object of the present invention is to provide a power converter and a current sampling circuit thereof, which sample a resonant current by adding a transformer to a resonant tank, so as to realize that a sampling resistor and an input filter capacitor are grounded together, and simplify the design of a control circuit. In addition, on the occasion of dial-up application, the variable resistor can be converted to the position with relatively gentle jump by adding the transformer, so that a better EMI effect is obtained.
According to a first aspect of the present invention, a current sampling circuit for a power converter is provided, where the power converter includes a charge pump PFC module and a resonant converter, and is characterized in that the sampling circuit includes a second transformer, where a primary winding of the second transformer is connected in series with a primary winding of a first transformer in the resonant converter, so as to obtain a current sampling signal representing a resonant current of the resonant converter on a secondary winding of the second transformer.
Specifically, the primary winding of the second transformer is connected in series in a resonant tank formed by connecting the resonant capacitor of the resonant converter, the primary winding of the first transformer, and the resonant inductor in series.
Specifically, the reference ground of the secondary winding of the second transformer is the reference ground of the direct-current input voltage of the resonant converter.
Specifically, the secondary winding of the second transformer is connected in parallel with a sampling resistor to obtain the current sampling signal at a non-ground terminal of the sampling circuit.
Specifically, the sampling resistor is connected in parallel with a variable resistor, so that the variable resistor is adjusted through a dial switch to generate different output currents.
Specifically, one end of the primary winding of the second transformer is connected to one end of the resonant capacitor of the resonant converter.
Specifically, the primary winding of the second transformer is connected in series between the resonant capacitor of the resonant converter and the primary winding of the first transformer.
Specifically, the secondary winding of the second transformer is connected in parallel with a sampling resistor, one end of the sampling resistor is connected to an intermediate node, and the other end of the sampling resistor generates the current sampling signal, wherein the intermediate node is a common node of the first power tube and the second power tube in the resonant converter.
Specifically, the primary winding of the second transformer is connected in parallel with a variable resistor, so that the variable resistor is adjusted through a dial switch to generate different output currents.
According to a second aspect of the present invention, there is provided a power converter comprising:
an input rectification module for rectifying an ac input voltage to output a rectified voltage;
the charge pump PFC module is connected with the output end of the input rectifying module to realize power factor correction;
the input filter capacitor is connected between the output end of the charge pump PFC module and a reference ground so as to convert the rectified voltage into a direct-current input voltage;
a resonant converter configured to convert the DC input voltage to an output voltage or output current to power a load; and
the current sampling circuit of any preceding claim.
Specifically, the charge pump PFC module includes:
a first diode and a second diode configured to be connected in series between a positive output terminal of the input rectification block to a positive input terminal of the resonant converter to form a unidirectional conduction path from the input rectification block to the resonant converter; and
and a boost capacitor connected between an intermediate node of the first and second diodes and the reference ground.
Specifically, the boost capacitor is further configured to be connected to a resonant capacitor in the resonant converter.
In summary, the present invention discloses a power converter and a current sampling circuit thereof. The primary winding of the transformer is connected in series in a resonant circuit of the resonant converter in the power converter, and then the secondary winding of the transformer is used for sampling the resonant current so as to adapt to different requirements.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:
fig. 1 is a circuit diagram of a prior art power converter;
FIG. 2 is a circuit diagram of a prior art power converter with dial up application;
FIG. 3 is a circuit diagram of a first power converter according to an embodiment of the utility model;
FIG. 4 is a block diagram of a control circuit in the power converter according to the embodiment of the utility model;
FIG. 5 is a circuit diagram of a second power converter according to an embodiment of the present invention; and
fig. 6 is a circuit diagram of a third power converter according to an embodiment of the utility model.
Detailed Description
The present invention will be described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details. Well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.
Further, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.
Meanwhile, it should be understood that, in the following description, a "circuit" refers to a conductive loop constituted by at least one element or sub-circuit through electrical or electromagnetic connection. When an element or circuit is referred to as being "connected to" another element or element/circuit is referred to as being "connected between" two nodes, it may be directly coupled or connected to the other element or intervening elements may be present, and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, it is intended that there are no intervening elements present.
Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, what is meant is "including, but not limited to".
In the description of the present invention, it is to be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.
Fig. 3 is a circuit diagram of a first power converter according to an embodiment of the utility model. As shown in fig. 3, the power converter includes an input rectification module 11, a charge pump PFC module 12, an input filter capacitor C1, and a resonant converter 13. The input rectifying module 11 is a rectifying bridge, and is configured to rectify the ac input voltage Vac to output a rectified voltage. The charge pump PFC module 12 performs a boost function using the resonant current drawn from the resonant tank and a current drawn from the rectified voltage to achieve power factor correction, and to provide current to the input filter capacitor C1. In the present embodiment, the charge pump PFC module 12 includes diodes D1 and D2 and a boost capacitor Cb. The diodes D1 and D2 are connected in series between the positive output terminal of the input rectifying module 11 and the positive input terminal of the resonant converter 13, thereby forming a unidirectional conductive path from the input rectifying module 11 to the resonant converter 13. The boost capacitor Cb is connected between the common point of the diodes D1 and D2 and the ground GND. The common point of the diodes D1 and D2 is also connected to one terminal of a resonant capacitor Cr in the resonant converter 13.
It should be understood that the charge pump PFC module 12 can be implemented in many different conversion forms, for example, the boost circuit Cb can be connected in parallel with the diode D2, the present invention is not limited to the circuit structure of the charge pump PFC, and any circuit capable of implementing the function of the charge pump PFC can be applied to the present invention.
An input filter capacitor C1 is connected between the output of the charge pump PFC module 12 and ground GND to convert the rectified voltage to a smoothed dc input voltage Vbus. The resonant converter 13 receives a dc input voltage Vbus for converting the dc input voltage Vbus into an output voltage or an output current for supplying power to a load, here an LED. The resonant converter 13 is a half-bridge LLC resonant converter, and the primary side includes power tubes Q1 and Q2 connected in series between the dc input voltage Vbus and ground GND, and a resonant tank formed by a resonant capacitor Cr, a resonant inductor Lr, and a primary winding Lp of a first transformer T1 connected in series. Specifically, the resonant capacitor Cr is connected between the charge pump PFC and one end (i.e., a non-dotted end) of the primary winding Lp, and the resonant inductor Lr is connected between the other end (i.e., a dotted end) of the primary winding Lp and the intermediate node HB. It should be understood that the resonant inductor Lr may also be connected between the resonant capacitor Cr and the primary winding Lp as long as the three are connected in series in the resonant tank. The secondary side comprises a rectifier circuit, here a full-wave rectifier circuit consisting of a secondary winding and diodes D3 and D4, and the output of the rectifier circuit is connected to an output capacitor Co, which is connected in parallel with the load LED. In addition, the resonant converter 13 further includes a control circuit for generating driving signals Vgs1 and Vgs2 to drive the power transistors Q1 and Q2, respectively, according to the current sampling signal CS and the output voltage feedback signal FB.
In contrast to fig. 1, in this embodiment, the sampling resistor Rs is not directly connected in series with the primary winding Lp, but a second transformer T2 is connected in series in the resonant tank for current sampling. In this embodiment, the sampling circuit includes a second transformer T2 and a sampling resistor Rs, where the second transformer T2 includes a primary winding T2A and a secondary winding T2B, which have opposite ends, and T2A: T2B ═ n: 1, wherein n is a positive integer, and in general, n is 1. For convenience of description, n is 1 in the following description.
In the present embodiment, the primary winding T2A of the second transformer T2 is connected in series between the resonant inductor Lr and the intermediate node HB, and the same-name end of the secondary winding is the same as the primary winding Lp, so that the resonant current I is obtainedLrAnd (4) flowing out of the end with the same name. The secondary winding T2B is connected in parallel with a sampling resistor Rs, and specifically, one end of the secondary winding T2B is directly connected to the ground GND of the dc input voltage Vbus, and the other end is connected to the ground GND via the sampling resistor Rs so as to be connected to the ground GND atSampling the non-grounded end of the resistor Rs to obtain the characteristic resonant current ILrThe current sampling signal CS.
Of course, it is understood that the primary winding T2A can be connected in series at any position in the resonant tank, for example, the primary winding T2A can also be connected in series between the resonant inductor Lr and the primary winding Lp, or between the resonant capacitor Cr and the primary winding Lp, or between the charge pump PFC and the resonant capacitor Cr, as long as the resonant current ILrAnd through the primary winding T2A.
The resonant current I flows out from the end with the same name of the primary winding T2ALrTherefore, the current ITB flowing into the dotted terminal of the secondary winding T2B is ILrSo that the current sampling signal CS is ILrXrs, and resonant current ILrProportional relation, so that the resonant current I can be characterizedLr。
Fig. 4 is a block diagram of a control circuit in the power converter according to the embodiment of the present invention. As shown in fig. 4, the control circuit includes a main control unit, a first driving circuit, a second driving circuit, and a signal conversion circuit, where the main control unit and the second driving circuit both use GND as a reference ground, and the first driving circuit uses the intermediate node HB as a reference ground. The main control unit is used for generating a compensation signal Vcomp (not shown) according to the current sampling signal CS and the output voltage feedback signal FB, and further generating switch control signals G1 and G2 according to the compensation signal Vcomp. The switch control signal G2 is sent directly to the second driving circuit to generate the driving signal Vgs2 to drive the power transistor Q2. The signal conversion circuit receives the switch control signal G1 for level conversion or isolation, so as to generate a switch control signal G1' to be transmitted to the first driving circuit, so that the first driving circuit outputs a driving signal Vgs1 with the intermediate node HB as a reference ground to drive the power tube Q1. It should be understood that there are many kinds of circuits for transforming the switch control signal G1 with GND as reference ground into the switch control signal G1' with HB as reference ground, and the present disclosure is not limited thereto. In addition, the control circuit may be packaged together or separately, that is, the portions with GND as the reference ground are packaged together, and the portions with HB as the reference ground are packaged together, which is not limited herein.
In summary, due to the addition of the second transformer T2, the reference ground of the current sampling signal CS is GND, so that the main control unit in the control circuit can use GND as the reference ground, and the design of the control circuit is simplified.
Fig. 5 is a circuit diagram of a second power converter according to an embodiment of the present invention. When the sampling resistor Rs is used in an occasion needing dial-up application, namely an occasion that adjustable output current can be achieved through one dial-up switch, the variable resistor Rb needs to be connected in parallel at two ends of the sampling resistor Rs, and the variable resistor Rb is led to a proper position through two longer lead wires, so that the resistance value of the variable resistor Rb is changed through the dial-up switch, and then the change of the output current is achieved. As shown in fig. 5, the sampling circuit is the same as that of fig. 3 in that a second transformer T2 is added to connect the sampling resistor Rs between the secondary winding T2B and the ground GND, which will not be described in detail. In contrast, the sampling circuit further includes a variable resistor Rb, and since the variable resistor Rb is connected in parallel with the sampling resistor Rs, one end of the variable resistor Rb is connected to the ground GND, which is a relatively stable potential, and does not continuously jump between high and low levels like the intermediate node HB, and thus, even if the lead is long, no serious EMI is caused. In this embodiment, the current sampling signal CS is I due to the addition of the variable resistor RbLr×(Rs//Rb)。
That is, the resonant current is sampled by adding the transformer in the resonant circuit, so that the sampling resistor and the direct current input voltage of the resonant converter are grounded, and the design of the control circuit is simplified. In addition, on the occasion of dial-up application, the variable resistor can be converted to the position with relatively gentle jump by adding the transformer, so that a better EMI effect is obtained.
Fig. 6 shows a circuit diagram of a third power converter according to an embodiment of the present invention. In a case where it is not necessary to make the main control unit in the control circuit share the dc input voltage with the Ground (GND), the main control unit may be referenced to the intermediate node HB. The resonant current sampling can be performed by adding a second transformer T3, and one end of the variable resistor Rb can be connected to a position where the potential is relatively stable, so as to satisfy the function of realizing different output currents through the dial switch.
Specifically, as shown in fig. 5, the sampling circuit includes a second transformer T3, a sampling resistor Rs, and a variable resistor Rb. The second transformer T3 includes a primary winding T3A and a secondary winding T3B, where T3A: T3B ═ 1: n, n are positive integers, and in general, n is 1, and for convenience of description, n is 1 in the following description.
The primary winding T3A is connected in parallel with the variable resistor Rb, the secondary winding T3B is connected in parallel with the sampling resistor Rs, and one end of the primary winding T3A is connected to one end of the resonant capacitor Cr, specifically, the primary winding T3A is connected in series between the resonant capacitor Cr and the primary winding Lp of the first transformer T1. At this time, one end of the variable resistor Rb is connected to the resonant capacitor Cr, and the voltage variation of the end is relatively smooth compared to HB, so that no serious EMI is generated. This connection does not affect the resonant current sampling, as will be described in more detail below.
When the secondary side of the transformer T3 is converted to the primary side, which is equivalent to the parallel connection of the variable resistor Rb and Rs, the voltage across the primary winding T3A is ILrX (Rb// Rs), and then according to the original secondary turn ratio, the voltage across the secondary winding T3B is ILrX (Rb// Rs), which is the value of the current sampling signal CS (as in fig. 2), is directly proportional to the resonant current ILr, and thus can characterize the value of the resonant current.
In summary, in the case where the main control unit uses HB as a reference ground and needs dial-up application, the transformer is added, so that the variable resistor can be connected to a position where the potential is relatively stable on the basis of realizing sampling of the resonant current, thereby avoiding generation of serious EMI.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (12)
1. A current sampling circuit for a power converter, wherein the power converter comprises a charge pump PFC module and a resonant converter, and is characterized in that the sampling circuit comprises a second transformer, wherein a primary winding of the second transformer is connected in series with a primary winding of a first transformer in the resonant converter, so as to obtain a current sampling signal representing a resonant current of the resonant converter on a secondary winding of the second transformer.
2. The current sampling circuit of claim 1, wherein the primary winding of the second transformer is connected in series in a resonant tank formed by a resonant capacitor of the resonant converter, the primary winding of the first transformer, and a resonant inductor in series.
3. The current sampling circuit of claim 1, wherein the reference ground of the secondary winding of the second transformer is a reference ground of the dc input voltage of the resonant converter.
4. The current sampling circuit of claim 2, wherein the secondary winding of the second transformer is connected in parallel with a sampling resistor to obtain the current sampling signal at a non-ground terminal of the sampling circuit.
5. The current sampling circuit of claim 4, wherein the sampling resistor is connected in parallel with a variable resistor, such that the variable resistor is adjusted by a toggle switch to produce different output currents.
6. The current sampling circuit of claim 1, wherein one end of the primary winding of the second transformer is connected to one end of a resonant capacitor of the resonant converter.
7. The current sampling circuit of claim 6, wherein the primary winding of the second transformer is connected in series between the resonant capacitor of the resonant converter and the primary winding of the first transformer.
8. The current sampling circuit of claim 7, wherein the secondary winding of the second transformer is connected in parallel with a sampling resistor, one end of the sampling resistor is connected to an intermediate node, and the other end of the sampling resistor generates the current sampling signal, wherein the intermediate node is a common node of the first and second power transistors in the resonant converter.
9. The current sampling circuit of claim 7, wherein the primary winding of the second transformer is connected in parallel with a variable resistor, such that the variable resistor is adjusted by a dial switch to produce different output currents.
10. A power converter, comprising:
an input rectification module for rectifying an ac input voltage to output a rectified voltage;
the charge pump PFC module is connected with the output end of the input rectifying module to realize power factor correction;
the input filter capacitor is connected between the output end of the charge pump PFC module and a reference ground so as to convert the rectified voltage into a direct-current input voltage;
a resonant converter configured to convert the DC input voltage to an output voltage or output current to power a load; and
the current sampling circuit of any one of claims 1-9.
11. The power converter of claim 10, wherein the charge pump PFC module comprises:
a first diode and a second diode configured to be connected in series between a positive output terminal of the input rectification block to a positive input terminal of the resonant converter to form a unidirectional conduction path from the input rectification block to the resonant converter; and
and a boost capacitor connected between an intermediate node of the first and second diodes and the reference ground.
12. The power converter of claim 11, wherein the boost capacitor is further configured to be coupled to a resonant capacitor in the resonant converter.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115226270A (en) * | 2022-09-16 | 2022-10-21 | 广东高斯宝电气技术有限公司 | Constant current control circuit of LED power supply |
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2021
- 2021-09-29 CN CN202122389454.0U patent/CN216414184U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115226270A (en) * | 2022-09-16 | 2022-10-21 | 广东高斯宝电气技术有限公司 | Constant current control circuit of LED power supply |
| CN115226270B (en) * | 2022-09-16 | 2023-01-24 | 广东高斯宝电气技术有限公司 | Constant current control circuit of LED power supply |
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