阅读说明：本技术 控制电路和方法以及功率变换器 (Control circuit and method and power converter ) 是由 杨袁钰 蔡波 黎坚 于 2019-09-30 设计创作，主要内容包括：本发明揭露了一种控制电路和方法以及功率变换器,所述控制电路用以控制包括至少两路输出电信号的功率变换器,所述功率变换器包括功率级电路、恒流输出支路和恒压输出支路,所述控制电路被配置为根据所述恒流输出支路和所述恒压输出支路的工作状态,选择表征所述恒流输出支路的输出信息的第一反馈信号和表征所述恒压输出支路的输出信息的第二反馈信号中的两者之一作为所述控制电路的反馈输入信号,以控制功率级电路的主功率开关管的开关状态。本发明控制电路构造简单,器件较少,成本较低,系统稳定性较好,避免了LED轻载时能量损耗较大的问题。(The invention discloses a control circuit and a method and a power converter, wherein the control circuit is used for controlling the power converter comprising at least two paths of output electric signals, the power converter comprises a power stage circuit, a constant current output branch and a constant voltage output branch, and the control circuit is configured to select one of a first feedback signal representing the output information of the constant current output branch and a second feedback signal representing the output information of the constant voltage output branch as a feedback input signal of the control circuit according to the working states of the constant current output branch and the constant voltage output branch so as to control the switching state of a main power switching tube of the power stage circuit. The control circuit has the advantages of simple structure, fewer devices, lower cost and better system stability, and avoids the problem of larger energy loss when the LED is lightly loaded.)

1. A control circuit is used for controlling a power converter comprising at least two paths of output electric signals, the power converter comprises a power level circuit, a constant current output branch and a constant voltage output branch, and the control circuit is characterized in that:

the control circuit is configured to select one of a first feedback signal representing output information of the constant-current output branch and a second feedback signal representing output information of the constant-voltage output branch as a feedback input signal of the control circuit according to working states of the constant-current output branch and the constant-voltage output branch so as to control the switching state of a main power switch tube of the power stage circuit.

2. The control circuit of claim 1, wherein: and when the constant-current output branch and the constant-voltage output branch are in working states at the same time, selecting the first feedback signal as the feedback input signal.

3. The control circuit of claim 1, wherein: and when the constant-current output branch and the constant-voltage output branch are in working states at the same time, selecting the smaller value of the first feedback signal and the second feedback signal as the feedback input signal.

4. The control circuit of claim 1, wherein: and when the constant current output branch is in an inoperative state and the constant voltage output branch is in an operative state, selecting the second feedback signal as the feedback input signal.

5. The control circuit of claim 1, wherein: the control circuit includes:

the selection module selects one of a first feedback signal and a second feedback signal as the feedback input signal according to the working states of the constant-current output branch and the constant-voltage output branch;

the feedback module is used for converting the feedback input signal into a feedback output signal;

and the control module controls the switching state of a main power switching tube of the power level circuit according to the feedback output signal so as to control the input signals of the constant-current output branch and the constant-voltage output branch.

6. The control circuit of claim 5, wherein: the power stage circuit is configured as a flyback power stage circuit comprising at least two secondary windings;

the input end of the constant voltage output branch is coupled to one secondary winding, and the constant voltage output branch comprises a direct current-direct current converter to convert a received first input voltage into a constant output voltage;

the input end of the constant current output branch is coupled to the other secondary winding, the constant current output branch comprises at least one current branch, each current branch comprises a series structure formed by connecting a load and a current control circuit in series, the current control circuit controls the constant current passing through the load, and when the current branches are more than one, a plurality of current branches are connected in parallel.

7. The control circuit of claim 5, wherein: the power stage circuit is configured as a flyback power stage circuit including at least one secondary winding having a center tap,

the input end of the constant voltage output branch is coupled to one of the high potential end and the middle tap end of the secondary winding, and the constant voltage output branch comprises a direct current-direct current converter for converting the received first input voltage into a constant output voltage;

the input end of the constant current output branch is coupled to one of a high potential end and a middle tap end of the secondary winding, the constant current output branch comprises at least one current branch, each current branch comprises a series structure formed by connecting a load and a current control circuit in series, the current control circuit controls the constant current passing through the load, and when the number of the current branches is larger than one, a plurality of current branches are connected in parallel.

8. The control circuit according to claim 6 or 7, wherein: the first feedback signal is configured to characterize a maximum of the voltage drops across all of the loads; the second feedback signal is configured to characterize the first input voltage.

9. The control circuit of claim 8, wherein: the first feedback signal is configured as the minimum value of all the low-potential terminal voltages of the load; the second feedback signal is configured to be a second voltage that is a divided voltage of the first input voltage.

10. The control circuit of claim 9, wherein: the selection module comprises a first switch, a second switch and a minimum value circuit, wherein the input end of the minimum value circuit receives the voltage of all the low-potential ends of the load or the second voltage and the voltage of all the low-potential ends of the load, the output end of the minimum value circuit is connected to the output end of the selection module through the first switch, one end of the second switch receives the second voltage, the other end of the second switch is connected with the output end of the selection module, and the output end of the selection module outputs the feedback input signal.

11. The control circuit of claim 10, wherein: when the constant-current output branch and the constant-voltage output branch are in working states at the same time, the first switch is closed, and the second switch is opened; when the constant current output branch is in an inoperative state and the constant voltage output branch is in an operative state, the second switch is closed and the first switch is opened.

12. The control circuit of claim 5, wherein: the feedback module comprises an optical coupler, generates a compensation signal according to a feedback input signal and converts the compensation signal into the feedback output signal by using the optical coupler.

13. The control circuit of claim 12, wherein: the feedback module further comprises a transconductance operational amplifier and a first capacitor, wherein a first input end of the transconductance operational amplifier receives the feedback input signal, a second input end of the transconductance operational amplifier receives a reference voltage, an output end of the transconductance operational amplifier is connected with one end of the first capacitor, the other end of the first capacitor is coupled to the ground, the voltage at the output end of the transconductance operational amplifier is the compensation signal, and the compensation signal controls the primary side current of the optocoupler, so that the secondary side current of the optocoupler is controlled to generate and control the feedback output signal.

14. The control circuit of claim 13, wherein: the feedback module further comprises a first transistor and a first resistor, wherein the control end of the first transistor is connected with the output end of the transconductance operational amplifier, when the first input end of the transconductance operational amplifier is a forward input end and the second input end of the transconductance operational amplifier is a reverse input end, the first transistor and the primary side of the optocoupler are connected in series between a third voltage and the ground, the first resistor and the secondary side of the optocoupler are sequentially connected in series between a fourth voltage and the ground, and the voltage of the common end of the first resistor and the secondary side of the optocoupler is the feedback output signal.

15. The control circuit of claim 13, wherein: the feedback module further comprises a second transistor and a second resistor, wherein a control end of the second transistor is connected with an output end of the transconductance operational amplifier, when a first input end of the transconductance operational amplifier is a reverse input end and a second input end of the transconductance operational amplifier is a forward input end, a primary side of the second transistor and a primary side of the optocoupler are connected in parallel between a third voltage and the ground, the second resistor and a secondary side of the optocoupler are sequentially connected in series between a fourth voltage and the ground, and a voltage of a common end of the second resistor and the secondary side of the optocoupler is the feedback output signal.

16. The control circuit of claim 14 or 15, wherein: the third voltage is the input voltage of the constant voltage output branch or the output voltage of the constant voltage output branch, and the fourth voltage is a set voltage.

17. A control method is used for controlling a power converter comprising at least two paths of output electric signals, the power converter comprises a power level circuit, a constant current output branch and a constant voltage output branch, and the control method is characterized in that:

and selecting one of a first feedback signal representing the output information of the constant-current output branch and a second feedback signal representing the output information of the constant-voltage output branch as a feedback input signal of the control circuit according to the working states of the constant-current output branch and the constant-voltage output branch so as to control the switching state of a main power switching tube of the power stage circuit.

18. The control method according to claim 17, characterized in that: and when the constant-current output branch and the constant-voltage output branch are in working states at the same time, selecting the first feedback signal as the feedback input signal.

19. The control method according to claim 17, characterized in that: and when the constant-current output branch and the constant-voltage output branch are in working states at the same time, selecting the smaller value of the first feedback signal and the second feedback signal as the feedback input signal.

20. The control method according to claim 17, characterized in that: and when the constant current output branch is in an inoperative state and the constant voltage output branch is in an operative state, selecting the second feedback signal as the feedback input signal.

21. The control method according to claim 17, characterized in that: the power stage circuit is configured as a flyback power stage circuit comprising at least two secondary windings;

the input end of the constant voltage output branch is coupled to one secondary winding, and the constant voltage output branch comprises a direct current-direct current converter to convert a received first input voltage into a constant output voltage;

the input end of the constant current output branch is coupled to the other secondary winding, the constant current output branch comprises at least one current branch, each current branch comprises a series structure formed by connecting a load and a current control circuit in series, the current control circuit controls the constant current passing through the load, and when the current branches are more than one, a plurality of current branches are connected in parallel.

22. The control method according to claim 17, characterized in that: the power stage circuit is configured as a flyback power stage circuit including at least one secondary winding having a center tap,

the input end of the constant voltage output branch is coupled to one of the high potential end and the middle tap end of the secondary winding, and the constant voltage output branch comprises a direct current-direct current converter for converting the received first input voltage into a constant output voltage;

the input end of the constant current output branch is coupled to one of a high potential end and a middle tap end of the secondary winding, the constant current output branch comprises at least one current branch, each current branch comprises a series structure formed by connecting a load and a current control circuit in series, the current control circuit controls the constant current passing through the load, and when the number of the current branches is larger than one, a plurality of current branches are connected in parallel.

23. The control method according to claim 21 or 22, characterized in that: the first feedback signal is configured to characterize a maximum of the voltage drops across all of the loads; the second feedback signal is configured to characterize the first input voltage.

24. A power converter, comprising:

a power stage circuit configured to provide energy to the constant current output branch and the constant voltage output branch;

the constant current output branch circuit is configured to provide constant current for a load;

a constant voltage output branch configured to output a constant voltage; and

the control circuit of any of claims 1-16, configured to select one of a first feedback signal characterizing output information of the constant current output branch and a second feedback signal characterizing output information of the constant voltage output branch as a feedback input signal of the control circuit to control a switching state of a main power switch of the power stage circuit according to an operating state of the constant current output branch and the constant voltage output branch.

Technical Field

The present invention relates to the field of power electronics, and more particularly, to a control circuit and method and a power converter.

Background

In many occasions, the power converter is required to output constant current and constant voltage at the same time, so the constant-current and constant-voltage dual-output power converter is applied, has constant-current and constant-voltage dual outputs, and provides constant voltage at the same time when the constant-current output branch outputs the constant current. As shown in fig. 1, a constant current and constant voltage dual-output power converter generally utilizes a flyback conversion circuit to provide energy for a constant current output branch and a constant voltage output branch, where the constant current output branch includes an LED driving circuit, the LED driving circuit is connected in series with an LED, the LED driving circuit controls a current flowing through the LED to be a constant current, the constant voltage output branch outputs a constant voltage, and meanwhile, a feedback circuit receives a feedback signal at a secondary side of a transformer of the flyback conversion circuit to form a control signal at a primary side of the transformer to control a switching state of a main switching tube of the flyback conversion circuit, so as to control an output of the flyback conversion circuit, that is, an input signal of the constant current output branch and an input signal of the constant.

Disclosure of Invention

In view of this, the invention provides a control circuit and method with a simple circuit and less energy loss, and a power converter, which solve the technical problems in the prior art that a feedback circuit is more complex and has more devices, the system stability is poorer, the energy loss is larger when an LED is lightly loaded, and the like.

In a first aspect, the present invention provides a control circuit for controlling a power converter including at least two output electrical signals, the power converter including a power stage circuit, a constant current output branch and a constant voltage output branch;

the control circuit is configured to select one of a first feedback signal representing output information of the constant-current output branch circuit and a second feedback signal representing output information of the constant-voltage output branch circuit as a feedback input signal of the control circuit according to working states of the constant-current output branch circuit and the constant-voltage output branch circuit so as to control the switching state of a main power switch tube of the power stage circuit.

Preferably, when the constant current output branch and the constant voltage output branch are simultaneously in a working state, the first feedback signal is selected as the feedback input signal.

Preferably, when the constant current output branch and the constant voltage output branch are simultaneously in a working state, the smaller value of the first feedback signal and the second feedback signal is selected as the feedback input signal.

Preferably, when the constant current output branch is in an inactive state and the constant voltage output branch is in an active state, the second feedback signal is selected as the feedback input signal.

Preferably, the control circuit includes:

the selection module selects one of a first feedback signal and a second feedback signal as the feedback input signal according to the working states of the constant-current output branch and the constant-voltage output branch;

the feedback module is used for converting the feedback input signal into a feedback output signal;

and the control module controls the switching state of a main power switching tube of the power level circuit according to the feedback output signal so as to control the input signals of the constant-current output branch and the constant-voltage output branch.

Preferably, the power stage circuit is configured as a flyback power stage circuit comprising at least two secondary windings;

the input end of the constant voltage output branch is coupled to one secondary winding, and the constant voltage output branch comprises a direct current-direct current converter to convert a received first input voltage into a constant output voltage;

the input end of the constant current output branch is coupled to the other secondary winding, the constant current output branch comprises at least one current branch, each current branch comprises a series structure formed by connecting a load and a current control circuit in series, the current control circuit controls the constant current passing through the load, and when the current branches are more than one, a plurality of current branches are connected in parallel.

Preferably, the power stage circuit is configured as a flyback power stage circuit, the flyback power stage circuit comprising at least one secondary winding with a center tap,

the input end of the constant voltage output branch is coupled to one of the high potential end and the middle tap end of the secondary winding, and the constant voltage output branch comprises a direct current-direct current converter for converting the received first input voltage into a constant output voltage;

the input end of the constant current output branch is coupled to one of a high potential end and a middle tap end of the secondary winding, the constant current output branch comprises at least one current branch, each current branch comprises a series structure formed by connecting a load and a current control circuit in series, the current control circuit controls the constant current passing through the load, and when the number of the current branches is larger than one, a plurality of current branches are connected in parallel.

Preferably, the first feedback signal is configured to characterize a maximum of the voltage drops across all of the loads; the second feedback signal is configured to characterize the first input voltage.

Preferably, the first feedback signal is configured as the minimum value among the voltages at the low potential ends of all the loads; the second feedback signal is configured to be a second voltage that is a divided voltage of the first input voltage.

Preferably, the selection module includes a first switch, a second switch, and a minimum value circuit, an input terminal of the minimum value circuit receives the voltage of all the low potential terminals of the load or the second voltage and the voltage of all the low potential terminals of the load, an output terminal of the minimum value circuit is connected to an output terminal of the selection module through the first switch, one terminal of the second switch receives the second voltage, the other terminal of the second switch is connected to the output terminal of the selection module, and the output terminal of the selection module outputs a feedback input signal.

Preferably, when the constant current output branch and the constant voltage output branch are in working states at the same time, the first switch is closed, and the second switch is opened; when the constant current output branch is in an inoperative state and the constant voltage output branch is in an operative state, the second switch is closed and the first switch is opened.

Preferably, the feedback module includes an optical coupler, and the feedback module generates a compensation signal according to a feedback input signal and converts the compensation signal into the feedback output signal by using the optical coupler.

Preferably, the feedback module further includes a transconductance operational amplifier and a first capacitor, a first input end of the transconductance operational amplifier receives the feedback input signal, a second input end of the transconductance operational amplifier receives a reference voltage, an output end of the transconductance operational amplifier is connected to one end of the first capacitor, the other end of the first capacitor is grounded, a voltage at an output end of the transconductance operational amplifier is the compensation signal, and the compensation signal controls a primary side current of the optocoupler, so as to control a secondary side current of the optocoupler to generate and control the feedback output signal.

Preferably, the feedback module further includes a first transistor and a first resistor, a control end of the first transistor is connected to an output end of the transconductance operational amplifier, when a first input end of the transconductance operational amplifier is a forward input end and a second input end of the transconductance operational amplifier is a reverse input end, the first transistor and a primary side of the optocoupler are connected in series between a third voltage and ground, the first resistor and a secondary side of the optocoupler are sequentially connected in series between a fourth voltage and ground, and a voltage of a common end of the first resistor and the secondary side of the optocoupler is the feedback output signal.

Preferably, the feedback module further includes a second transistor and a second resistor, a control end of the second transistor is connected to an output end of the transconductance operational amplifier, when a first input end of the transconductance operational amplifier is a reverse input end and a second input end of the transconductance operational amplifier is a forward input end, the second transistor and a primary side of the optocoupler are connected in parallel between a third voltage and ground, the second resistor and a secondary side of the optocoupler are sequentially connected in series between a fourth voltage and ground, and a voltage at a common end of the second resistor and the secondary side of the optocoupler is the feedback output signal.

Preferably, the third voltage is an input voltage of the constant voltage output branch or an output voltage of the constant voltage output branch, and the fourth voltage is a set voltage.

In a second aspect, the present invention further provides a control method for controlling a power converter including at least two output electrical signals, where the power converter includes a power stage circuit, a constant current output branch and a constant voltage output branch, and includes:

and selecting one of a first feedback signal representing the output information of the constant-current output branch and a second feedback signal representing the output information of the constant-voltage output branch as a feedback input signal of the control circuit according to the working states of the constant-current output branch and the constant-voltage output branch so as to control the switching state of a main power switching tube of the power level circuit.

Preferably, when the constant current output branch and the constant voltage output branch are simultaneously in a working state, the first feedback signal is selected as the feedback input signal.

Preferably, when the constant current output branch and the constant voltage output branch are simultaneously in a working state, the smaller value of the first feedback signal and the second feedback signal is selected as the feedback input signal.

Preferably, when the constant current output branch is in an inactive state and the constant voltage output branch is in an active state, the second feedback signal is selected as the feedback input signal.

Preferably, the power stage circuit is configured as a flyback power stage circuit comprising at least two secondary windings;

the input end of the constant voltage output branch is coupled to one secondary winding, and the constant voltage output branch comprises a direct current-direct current converter to convert a received first input voltage into a constant output voltage;

the input end of the constant current output branch is coupled to the other secondary winding, the constant current output branch comprises at least one current branch, each current branch comprises a series structure formed by connecting a load and a current control circuit in series, the current control circuit controls the constant current passing through the load, and when the current branches are more than one, a plurality of current branches are connected in parallel.

Preferably, the power stage circuit is configured as a flyback power stage circuit, the flyback power stage circuit comprising at least one secondary winding with a center tap,

the input end of the constant voltage output branch is coupled to one of the high potential end and the middle tap end of the secondary winding, and the constant voltage output branch comprises a direct current-direct current converter for converting the received first input voltage into a constant output voltage;

the input end of the constant current output branch is coupled to one of a high potential end and a middle tap end of the secondary winding, the constant current output branch comprises at least one current branch, each current branch comprises a series structure formed by connecting a load and a current control circuit in series, the current control circuit controls the constant current passing through the load, and when the number of the current branches is larger than one, a plurality of current branches are connected in parallel.

Preferably, the first feedback signal is configured to characterize a maximum of the voltage drops across all of the loads; the second feedback signal is configured to characterize the first input voltage.

In a third aspect, the present invention further provides a power converter comprising:

a power stage circuit configured to provide energy to the constant current output branch and the constant voltage output branch;

the constant current output branch circuit is configured to provide constant current for a load;

a constant voltage output branch configured to output a constant voltage;

the control circuit described in any of the above is configured to select one of a first feedback signal representing output information of the constant current output branch and a second feedback signal representing output information of the constant voltage output branch as a feedback input signal of the control circuit according to working states of the constant current output branch and the constant voltage output branch, so as to control a switching state of a main power switch of a power stage circuit.

Compared with the prior art, the technical scheme of the invention has the following advantages: according to the working states of the constant-current output branch and the constant-voltage output branch, the control circuit selects one of a first feedback signal representing the output information of the constant-current output branch and a second feedback signal representing the output information of the constant-voltage output branch as a feedback input signal of the control circuit so as to control the switching state of a main power switching tube of the power stage circuit and further control the power stage circuit to provide energy for the constant-current output branch and the constant-voltage output branch of the subsequent stage. When the constant-voltage output branch and the constant-current output branch work simultaneously, a first feedback signal or a smaller value of the first feedback signal and a second feedback signal is used as a feedback input signal, when the constant-current output branch is in an inoperative state and the constant-voltage output branch is in an operative state, the second feedback signal is used as the feedback input signal, namely only one feedback signal is used as the feedback input signal in the working process. The control circuit has simple structure, fewer devices and lower cost; the system stability is better; when the LED is lightly loaded, the problem of large energy loss is avoided.

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 schematic of a prior art feedback circuit and power converter;

FIG. 2 is a circuit schematic of a prior art feedback circuit;

FIG. 3 is a schematic diagram of a prior art circuit for generating an LED driving compensation signal;

FIG. 4 is a functional block diagram of the control circuit and power converter of the present invention;

FIG. 5 is a block diagram of the control circuit of the present invention;

FIG. 6 is a schematic circuit diagram of a first embodiment of the control circuit and the power converter of the present invention;

FIG. 7 is a schematic circuit diagram of the current control circuit according to the present invention;

FIG. 8 is a schematic circuit diagram of a second embodiment of a control circuit according to the present invention;

FIG. 9 is a schematic circuit diagram of a third embodiment of the control circuit and power converter of the present invention;

fig. 10 is a schematic circuit diagram of a fourth embodiment of the control circuit of the present invention.

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.

Fig. 4 is a schematic block diagram of a control circuit and a power converter according to the present invention, where the control circuit 4 is configured to control the power converter including at least two output electrical signals, the power converter includes a power stage circuit 1, a constant current output branch 2, and a constant voltage output branch 3, the power stage circuit 1 provides energy to the constant current output branch 2 and the constant voltage output branch 3, and the control circuit 4 is configured to select one of a first feedback signal representing output information of the constant current output branch 2 and a second feedback signal representing output information of the constant voltage output branch 3 as a feedback input signal of the control circuit 4 according to working states of the constant current output branch 2 and the constant voltage output branch 3, so as to control a switching state of a main power switching tube of the power stage circuit 1. The control circuit 4 converts a feedback input signal into a feedback output signal, and controls the on-off state of a main power switch tube of the power stage circuit 1 by using the feedback output signal, so as to control the input energy of the constant-current output branch 2 and the constant-voltage output branch 3.

And when the constant current output branch 2 and the constant voltage output branch 3 are in working states at the same time, selecting the first feedback signal as the feedback input signal. When the constant current output branch 2 is in an inoperative state and the constant voltage output branch 3 is in an operative state, the second feedback signal is selected as the feedback input signal, so that the input voltage of the constant voltage output branch 3 is not less than a set value, and the stability of the output voltage of the constant voltage output branch 3 is ensured.

Optionally, in another embodiment, when the constant current output branch 2 and the constant voltage output branch 3 are simultaneously in an operating state, a smaller value of the first feedback signal and the second feedback signal is selected as the feedback input signal. The situation that the input voltage of the constant voltage output branch is too low when the load is changed or the working states of the constant current output branch and the constant voltage output branch are switched, namely the unstable state process, is avoided, and the constant voltage output branch can work normally.

FIG. 5 is a block diagram showing the constituent blocks of the control circuit of the present invention; the control circuit 4 comprises a selection module 41, a feedback module 42 and a control module 43, wherein the selection module 41 selects one of a first feedback signal and a second feedback signal as the feedback input signal according to the working states of the constant current output branch 2 and the constant voltage output branch 3; the feedback module 42 converts the feedback input signal into a feedback output signal; the control module 43 controls the on-off state of the main power switch tube of the power stage circuit according to the feedback output signal to control the input signals of the constant current output branch and the constant voltage output branch.

The power stage circuit 1 is configured as a flyback power stage circuit comprising at least two secondary windings; the two secondary windings here include the case of two secondary windings wound on the same magnetic core, and two secondary windings wound on different magnetic cores, respectively.

The input end of the constant voltage output branch 3 is coupled to one of the secondary windings, and the constant voltage output branch 3 comprises a dc-dc converter to convert the received first input voltage into a constant output voltage; the input end of the constant current output branch 2 is coupled to the other secondary winding, the constant current output branch 2 comprises at least one current branch, each current branch comprises a series structure formed by connecting a load and a current control circuit in series, the current control circuit controls the constant current passing through the load, and when the current branches are more than one, the multiple current branches are connected in parallel.

Optionally, in other embodiments, the power stage circuit 1 is configured as a flyback power stage circuit; the flyback power stage circuit includes at least one secondary winding having a center tap,

the input end of the constant voltage output branch 3 is coupled to one of the high potential end of the secondary winding and the middle tap end, and the constant voltage output branch 3 comprises a dc-dc converter for converting the received first input voltage into a constant output voltage; the input end of the constant current output branch 2 is coupled to one of a high potential end and a middle tap end of the secondary winding, the constant current output branch 2 comprises at least one current branch, each current branch comprises a series structure formed by connecting a load and a current control circuit in series, the current control circuit controls the constant current passing through the load, and when the current branch is larger than one branch, a plurality of current branches are connected in parallel;

the input end of the constant voltage output branch 3 and the input end of the constant current output branch 2 are not coupled to a high potential end or a middle tap end at the same time, that is, when the input end of the constant voltage output branch 3 is coupled to the high potential end, the constant current output branch 2 is coupled to the middle tap end; when the input end of the constant voltage output branch 3 is coupled to the middle tap end, the constant current output branch 2 is coupled to the high potential end.

Further, the first feedback signal is configured to characterize a maximum of the voltage drops across all of the loads; the second feedback signal is configured to characterize the first input voltage.

Further, the first feedback signal is configured as the minimum value of voltage at a low potential end of all loads of the constant current output branch; the second feedback signal is configured to be a second voltage, which is a divided voltage of the first input voltage of the constant voltage output branch.

The load of the present invention, which is not specifically described, refers to a load of the constant current output branch, and is described herein.

Further, in the present invention, the number of turns N1 of the secondary winding corresponding to the constant current output branch 2 and the number of turns N2 of the secondary winding corresponding to the constant voltage output branch 3 need to satisfy a certain relationship, so that:

1. the constant-voltage output branch 3 can still work normally under the condition of the lightest load of the constant-current output branch;

2. when the constant current output branch 2 does not work, the constant voltage output branch 3 can still work normally. The following embodiments all need to satisfy this relationship, and are not described in detail.

The control circuit is configured to use a first feedback signal or a smaller value of the first feedback signal and a second feedback signal as a feedback input signal when a constant voltage output branch and a constant current output branch work simultaneously, and use the second feedback signal as the feedback input signal when the constant current output branch is in a non-working state and the constant voltage output branch is in a working state, namely, only one feedback signal is used as the feedback input signal in the working process of the control circuit, and the control circuit has the advantages of simple structure, fewer devices and lower cost; the system stability is better; when the LED is in light load, the minimum value of the voltages of the low potential ends of all the loads is used as a feedback input signal in a normal working state, so that the problem of large energy loss caused by the fact that the voltage of the cathode of the LED is obviously higher than the reference voltage is solved.

The invention fig. 4 also provides a power converter, which is a constant-current and constant-voltage dual-output converter, and comprises: the power stage circuit 1, the constant current output branch 2, the constant voltage output branch 3 and the control circuit 4; the power stage circuit 1 is configured to provide energy to the constant current output branch and the constant voltage output branch; the constant current output branch 2 is configured to provide a constant current for a load; the constant voltage output branch 3 is configured to output a constant voltage; the control circuit 4 is configured to select one of a first feedback signal representing output information of the constant current output branch and a second feedback signal representing output information of the constant voltage output branch as a feedback input signal of the control circuit according to working states of the constant current output branch and the constant voltage output branch so as to control a switching state of a main power switch tube of the power stage circuit.

FIG. 6 is a schematic circuit diagram of a first embodiment of the control circuit and the power converter of the present invention; the power converter comprises a power stage circuit 1, a constant current output branch circuit 2, a constant voltage output branch circuit 3 and a control circuit 4, wherein the power stage circuit 1 is a flyback power stage circuit comprising two secondary windings, the input end of the constant voltage output branch circuit 3 is coupled to one secondary winding, and the input end of the constant current output branch circuit 2 is coupled to the other secondary winding; the constant current output branch 2 comprises four current branches, the four current branches are connected in parallel, each current branch comprises a series structure formed by connecting a load and a current control circuit in series, the current control circuit controls the constant current passing through the load, the load is an LED, and it needs to be noted that the LED in the invention can represent a single LED or an LED string formed by connecting a plurality of LEDs in series, which is not limited in the invention; taking the current control circuit in which the LED1 is connected in series as an example, the current control circuits of the other current branches have the same or similar structure, as shown in fig. 7, the current control circuit includes a transistor Qr1, a resistor Rs1 and an operational amplifier OP1, the LED1, the transistor Qr1 and the resistor Rs1 are connected in series between the high-potential end of the input voltage of the constant-current output branch and the ground, the anode of the LED is connected to the high-potential end of the input voltage of the constant-current output branch, a first input end of the operational amplifier OP1 is connected to the common end of the transistor Qr1 and the resistor Rs1, a second input end of the operational amplifier OP1 is connected to the control end of the transistor Qr 1. The current control circuit may be implemented in other ways in other embodiments, and embodiments in which the current control circuit functions to control the current flowing through the LED to be constant are within the scope of the present invention.

The constant voltage output branch 3 includes a dc-dc converter to convert the received first input voltage Vin into a constant output voltage. In one embodiment, the dc-dc converter is a buck converter. The buck converter may adopt control methods such as peak current control and valley current control, which are not limited in the present invention. In other embodiments, the dc-dc converter may be a boost converter or other converters, and the invention is not limited thereto.

As shown in fig. 6, the control circuit 4 includes a selection module 41, a feedback module 42 and a control module 43, and the first feedback signal is configured as the minimum value of voltage at low potential end of all loads of the constant current output branch 2; the second feedback signal is configured as a second voltage which is a divided voltage of the first input voltage of the constant voltage output branch 3, the selection module 41 includes a first switch S1, a second switch S2, and a minimum value circuit, an input terminal of the minimum value circuit receives the voltages of the low potential terminals of all the LEDs and outputs the minimum value of the voltages of the low potential terminals of the LEDs, an output terminal of the minimum value circuit is connected to an output terminal of the selection module 41 through the first switch S1, one terminal of the second switch S2 receives the second voltage V2, the other terminal of the second switch S2 is connected to the output terminal of the selection module 41, and the output terminal of the selection module 41 outputs the feedback input signal. The second voltage V2 is a divided voltage of the first input voltage, and the first input voltage is an input voltage of the constant voltage output branch 3. Specifically, the resistor Rv3 and the resistor Rv2 are connected in series between a first input voltage and ground, and the voltage at the common end of the resistor Rv3 and the resistor Rv2 is a second voltage V2.

When the constant current output branch 2 and the constant voltage output branch 3 are in a working state at the same time, that is, when LEDon in fig. 6 is active, the first switch S1 is closed, the second switch S2 is opened, and the feedback input signal is the minimum value of the voltages at the low potential ends of all the LEDs; when the constant current output branch 2 is in an inactive state and the constant voltage output branch 3 is in an active state, that is, when the LED is off in fig. 6, the second switch S2 is closed, the first switch S1 is opened, and the feedback input signal is the second voltage V2.

The feedback module 42 includes an opto-coupler OPC1, and the feedback module 42 generates a compensation signal from a feedback input signal and converts the compensation signal to the feedback output signal using the opto-coupler OPC 1.

The feedback module 42 further includes a transconductance operational amplifier GM1 and a first capacitor C1, a first input end of the transconductance operational amplifier GM1 receives the feedback input signal, a second input end of the transconductance operational amplifier GM1 receives a reference voltage Vref, an output end of the transconductance operational amplifier GM1 is connected to one end of the first capacitor C1, the other end of the first capacitor C1 is grounded, a voltage at an output end of the transconductance operational amplifier GM1 is the compensation signal, and the compensation signal controls a primary side current of the optocoupler, so as to control a secondary side current of the optocoupler to generate and control the feedback output signal. Optionally, the feedback module 42 further includes a resistor Rc1 connected between the first capacitor C1 and ground, that is, the transconductance operational amplifier output is connected to an Rc structure formed by the first capacitor C1 and the resistor Rc 1.

As shown in fig. 6, the feedback output signal and the compensation signal have the same variation trend in the first embodiment. Specifically, the feedback module 42 further includes a first transistor Qf1 and a first resistor R1, a control end of the first transistor Qf1 is connected to an output end of the transconductance operational amplifier GM1, when a first input end of the transconductance operational amplifier GM1 is a forward input end, a second input end of the transconductance operational amplifier GM1 is an inverting input end, a primary side of the first transistor Qf1 and the optical coupler OPC1 are connected in series between a third voltage and ground, a secondary side of the first resistor R1 and the optical coupler OPC1 are connected in series between a fourth voltage and ground, and a voltage of a common end of the first resistor R1 and the secondary side of the optical coupler OPC1 is the feedback output signal. The third voltage is an input voltage Vin of the constant voltage output branch or an output voltage Vout of the constant voltage output branch, and the fourth voltage is a setting voltage Vpref.

The control module 43 controls the on-off state of the main power switch tube of the power stage circuit according to the feedback output signal to control the input signals of the constant current output branch and the constant voltage output branch.

In addition, the control circuit further includes a resistor Rf1, a resistor Rf2, a resistor Rc1 and a capacitor Cf1, which are not essential features of the present invention and thus will not be described in detail herein.

FIG. 8 is a schematic circuit diagram of a second embodiment of a control circuit according to the present invention; a part of the feedback module 42 of the control circuit is different from the first embodiment, and the rest of the control circuit is the same as the first embodiment, and the description of the same part is omitted. The feedback module 42 includes an opto-coupler OPC2, and the feedback module 42 generates a compensation signal from a feedback input signal and converts the compensation signal to the feedback output signal using the opto-coupler OPC 2. The feedback module 42 further includes a transconductance operational amplifier GM1 and a first capacitor C1, a first input end of the transconductance operational amplifier GM1 receives the feedback input signal, a second input end of the transconductance operational amplifier GM1 receives a reference voltage Vref, an output end of the transconductance operational amplifier GM1 is connected to one end of the first capacitor C1, the other end of the first capacitor C1 is grounded, a voltage at an output end of the transconductance operational amplifier GM1 is the compensation signal, and the compensation signal controls a primary side current of the optocoupler, so as to control a secondary side current of the optocoupler to generate and control the feedback output signal.

As shown in fig. 8, the variation trend of the feedback output signal and the compensation signal in the second embodiment is opposite. The feedback module further comprises a second transistor Qf2 and a second resistor R2, a control end of the second transistor Qf2 is connected with an output end of the transconductance operational amplifier GM1, when a first input end of the transconductance operational amplifier GM1 is a reverse input end, a second input end of the transconductance operational amplifier is a forward input end, primary sides of the second transistor Qf2 and the optical coupler OPC2 are connected in parallel between a third voltage and ground, secondary sides of the second resistor R2 and the optical coupler OPC1 are sequentially connected in series between a fourth voltage and ground, and voltage of a common end of the second resistor R2 and the secondary side of the optical coupler OPC2 is the feedback output signal. The third voltage is an input voltage Vin of the constant voltage output branch or an output voltage Vout of the constant voltage output branch, and the fourth voltage is a setting voltage Vpref.

Similarly, the control circuit further includes a resistor Rf3, a resistor Rf4, a resistor Rf5, a resistor Rf6, a resistor Rc1 and a capacitor Cf2, which are not necessary features for implementing the present invention and will not be described in detail herein.

FIG. 9 is a schematic circuit diagram of a third embodiment of the control circuit and power converter of the present invention; the selecting module 41 of the control circuit 4 in fig. 9 is different from the first embodiment, and other parts are the same as the first embodiment, which is not repeated herein. The selection module 41 shown in the third embodiment in fig. 9 includes a first switch S1, a second switch S2, and a minimum value circuit, an input terminal of the minimum value circuit receives the second voltage V2 and the voltages of all the low-potential terminals of the load and outputs the minimum value of the voltages of the low-potential terminals of all the LEDs and the second voltage V2, an output terminal of the minimum value circuit is connected to an output terminal of the selection module 41 through the first switch S1, one terminal of the second switch S2 receives the second voltage V2, the other terminal of the second switch S2 is connected to the output terminal of the selection module 41, and the output terminal of the selection module 41 outputs a feedback input signal.

When the constant current output branch 2 and the constant voltage output branch 3 are simultaneously in a working state, that is, when LEDon in fig. 6 is active, the first switch S1 is closed, the second switch S2 is opened, and the feedback input signal is the minimum value of the low potentials of all the LEDs; when the constant current output branch 2 is in an inactive state and the constant voltage output branch 3 is in an active state, that is, when the LED is off in fig. 6, the second switch S2 is closed, the first switch S1 is opened, and the feedback input signal is the second voltage V2, that is, the divided voltage of the first input voltage.