TW201840114A - Power converter and control method thereof - Google Patents

Abstract

A power converter includes a primary-side switching circuit, a resonant circuit, a transformer including primary and secondary windings, a secondary-side rectifying circuit, voltage and current sensing circuits, and a processing circuit. The primary-side switching circuit controls switches to be on or off based on a pulse signal to convert an input voltage to a square wave signal. The resonant circuit is coupled to the primary-side switching circuit and receives the square wave signal to provide a primary-side current. The primary winding is coupled to the resonant circuit. The secondary-side rectifying circuit is coupled to the secondary winding and rectifies the secondary ac signal output by the secondary winding and outputs an output voltage. The voltage and the current sensing circuits detect the voltage and current of the primary winding and respectively output voltage and current sensing signals. The processing circuit outputs the pulse signal according to the voltage and current sensing signals.

Description

Power converter and control method thereof

The present disclosure is directed to a power converter, and more particularly to a resonant power converter.

The LLC resonant converter achieves a stable output voltage through frequency modulation. Recently, the LLC resonant converter is widely used in renewable energy power supply systems such as solar photovoltaic power generation because it is suitable for a wide range of input voltages and high power output.

However, in the existing converter control strategy, the output voltage of the secondary side must be sampled and fed back to the primary side for control. Therefore, a high withstand voltage isolation element must be provided for signal transmission, resulting in an increase in circuit cost. Therefore, how to improve the existing power converter control method is an important research topic in the current related field.

One aspect of the present disclosure is a power converter. The power converter comprises: a primary switching circuit, comprising a plurality of switches, wherein the primary switching circuit is configured to switch the opening and closing of the switches according to a pulse signal to convert the DC input voltage into a one-wave signal; a resonant circuit Electrically connected to the primary switching circuit for receiving the square wave signal to provide a primary current; a transformer, wherein a primary winding of the transformer is electrically connected to the resonant circuit; and a secondary rectifier circuit Electrically connected to a side winding of the transformer for rectifying a side AC signal outputted by the secondary winding and outputting an output voltage; a voltage detecting circuit for detecting both ends of the primary winding Cross-voltage and output a voltage detection signal; a current detection circuit for detecting the primary current and outputting a current detection signal; and a processing circuit for detecting a signal according to the voltage The current detecting signal outputs the pulse signal.

In some embodiments, the processing circuit is configured to adjust a switching frequency of the switches through the pulse signal to control the output voltage.

In some embodiments, the processing circuit obtains a relationship between a voltage across the primary winding and the output voltage through a transformer model corresponding to the transformer, and adjusts the pulse signal accordingly.

In some embodiments, the transformer model includes a turns ratio parameter, a primary winding resistance parameter, and a secondary winding resistance parameter.

In some embodiments, the processing circuit further obtains a relationship between the voltage across the primary winding and the output voltage through the transformer model, the primary current, and the voltage drop of the diode in the secondary rectifier circuit. .

In some embodiments, the power converter further includes a driving circuit electrically connected to the processing circuit and the switches in the primary switching circuit, and the processing circuit detects the signal and the current according to the voltage The detection signal outputs a pulse frequency modulation signal, and the driving circuit outputs a plurality of driving signals to the switches according to the pulse frequency modulation signal to switch the opening and closing of the switches.

In some embodiments, the resonant circuit includes a resonant capacitor unit and a resonant inductor unit in series with one another.

In some embodiments, the switches include: a first switch, a first end of the first switch is electrically connected to a positive terminal of an input voltage source, and a second end of the first switch is electrically Connected to a first end of the resonant circuit; a second switch, a first end of the second switch is electrically connected to the first end of the resonant circuit, and a second end of the second switch is electrically connected a third switch, a first end of the third switch is electrically connected to the positive end of the input voltage source, and a second end of the third switch is electrically connected to the positive end of the third switch a second end of the resonant circuit; and a fourth switch, a first end of the fourth switch is electrically connected to the second end of the resonant circuit, and a second end of the fourth switch is electrically connected to The negative terminal of the input voltage source.

In some embodiments, the secondary rectifier circuit includes: a first diode, an anode end of the first diode is electrically connected to a first end of the secondary winding, the first diode a cathode end is electrically connected to a first end of an output capacitor; a second diode, an anode end of the second diode is electrically connected to a second end of the output capacitor, the second a cathode end of the pole body is electrically connected to the anode end of the first diode; a third diode, an anode end of the third diode is electrically connected to a second end of the secondary winding a cathode end of the third diode is electrically connected to the first end of the output capacitor; and a fourth diode, an anode end of the fourth diode is electrically connected to the output capacitor The second end of the fourth diode is electrically connected to the anode end of the third diode.

Another aspect of the present disclosure is a power converter. The power converter comprises: a primary circuit comprising a plurality of switches, wherein the switches are respectively selectively turned on or off according to the plurality of driving signals; and a transformer comprising: a primary winding electrically connected to the original The edge circuit is configured to receive a primary side square wave signal from the primary side circuit; a secondary side winding for outputting a side alternating current signal corresponding to the primary side square wave signal; and a voltage detecting circuit for detecting The voltage across the primary winding is outputted with a voltage detection signal; a current detection circuit is configured to detect a primary current flowing through the primary circuit and output a current detection according to the primary current a side rectifier circuit electrically connected to the secondary winding for rectifying the secondary AC signal and outputting an output voltage; and a processing circuit for detecting the signal and the current detection according to the voltage The test signal controls a switching frequency of the drive signals.

In some embodiments, the processing circuit obtains a relationship between a voltage across the primary winding and the output voltage through a transformer model corresponding to the transformer, thereby adjusting the switching frequency.

In some embodiments, the transformer model includes a turns ratio parameter, a primary winding resistance parameter, and a secondary winding resistance parameter.

In some embodiments, the processing circuit further obtains a relationship between the voltage across the primary winding and the output voltage through the transformer model, the primary current, and the voltage drop of the diode in the secondary rectifier circuit. .

In some embodiments, the power converter further includes a driving circuit electrically connected to the processing circuit and the switches in the primary circuit, and the processing circuit detects the signal and the current detection according to the voltage The test signal outputs a pulse frequency modulation signal, and the driving circuit outputs the driving signals to the switches according to the pulse frequency modulation signal to switch the opening and closing of the switches.

In some embodiments, the primary circuit further includes a resonant circuit including a resonant capacitor unit and a resonant inductor unit connected in series with each other.

In some embodiments, the switches in the primary circuit include: a first switch, a first end of the first switch is electrically connected to a positive terminal of an input voltage source, and the first switch a second end is electrically connected to a first end of the resonant circuit; a second switch, a first end of the second switch is electrically connected to the first end of the resonant circuit, and a second switch The second end is electrically connected to a negative terminal of the input voltage source; a third switch, a first end of the third switch is electrically connected to the positive terminal of the input voltage source, and a third switch The second end is electrically connected to a second end of the resonant circuit; and a fourth switch, a first end of the fourth switch is electrically connected to the second end of the resonant circuit, and a fourth switch The two ends are electrically connected to the negative terminal of the input voltage source.

In some embodiments, the secondary rectifier circuit includes: a first diode, an anode end of the first diode is electrically connected to a first end of the secondary winding, the first diode a cathode end is electrically connected to a first end of an output capacitor; a second diode, an anode end of the second diode is electrically connected to a second end of the output capacitor, the second a cathode end of the pole body is electrically connected to the anode end of the first diode; a third diode, an anode end of the third diode is electrically connected to a second end of the secondary winding a cathode end of the third diode is electrically connected to the first end of the output capacitor; and a fourth diode, an anode end of the fourth diode is electrically connected to the output capacitor The second end of the fourth diode is electrically connected to the anode end of the third diode.

A further aspect of the present disclosure is a method for controlling a power converter, comprising: detecting, by a current detecting circuit in a power converter, a primary current flowing through a primary circuit of the power converter, Obtaining a current detecting signal; detecting, by a voltage detecting circuit in the power converter, a voltage across a transformer of the power converter that is electrically coupled to one end of one of the primary windings of the primary side circuit Obtaining a voltage detection signal; obtaining a relationship between a voltage across the primary winding and an output voltage of the power converter through a transformer model corresponding to the transformer; based on the voltage across the primary winding The relationship between the output voltage and the output voltage is controlled according to the voltage detection signal and the current detection signal to adjust the switching frequency of the plurality of switches in the primary circuit.

In some embodiments, the transformer model includes a turns ratio parameter, a primary winding resistance parameter, and a secondary winding resistance parameter. The relationship between the voltage across the primary winding and the output voltage is further included: The relationship between the voltage across the primary winding and the output voltage is obtained by the transformer model, the primary current, and the voltage drop of the diode in a secondary rectifier circuit of the power converter.

In some embodiments, controlling the switching frequency of the switches comprises: calculating, by the processing circuit, a pulse frequency modulation signal according to the current detection signal and the voltage detection signal; and receiving, by a driving circuit The pulse frequency modulates the signal, and outputs a plurality of driving signals according to the pulse frequency modulation signal to selectively turn on or off the switches to adjust the switching frequency of the switches.

The embodiments are described in detail below to better understand the aspects of the disclosure, but the embodiments are not intended to limit the scope of the disclosure, and the description of the structural operation is not used. In order to limit the order in which they are performed, any device that has been re-combined by the components, resulting in equal functionality, is covered by this disclosure. In addition, according to industry standards and practices, the drawings are only for the purpose of assisting the description, and are not drawn according to the original size. In fact, the dimensions of the various features may be arbitrarily increased or decreased for convenience of explanation. In the following description, the same elements will be denoted by the same reference numerals for explanation.

The terms used in the entire specification and the scope of the patent application, unless otherwise specified, generally have the ordinary meaning of each term used in the field, the content disclosed herein, and the particular content. Certain terms used to describe the disclosure are discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in the description of the disclosure.

In addition, the terms "including", "including", "having", "containing", and the like, as used herein, are all open terms, meaning "including but not limited to". Further, "and/or" as used herein includes any one or combination of one or more of the associated listed items.

As used herein, when an element is referred to as "connected" or "coupled", it may mean "electrically connected" or "electrically coupled". "Connected" or "coupled" can also be used to indicate that two or more components operate or interact with each other. In addition, although the terms "first", "second", and the like are used herein to describe different elements, the terms are used only to distinguish the elements or operations described in the same technical terms. The use of the term is not intended to be a limitation or a

Please refer to Figure 1. FIG. 1 is a schematic diagram of a power converter 100 in accordance with some embodiments of the present disclosure. As shown in FIG. 1 , in some embodiments, the power converter 100 includes a primary switching circuit 120 , a resonant circuit 140 , a transformer 160 , a secondary rectifier circuit 180 , a voltage detection circuit 110 , a current detection circuit 130 , and processing Circuit 150 and drive circuit 170. In some embodiments, the power converter 100 can be applied to a DC-to-DC conversion device in a solar photovoltaic system to convert the DC voltage output by the solar panel to an appropriate voltage level. In this way, the inverter of the latter stage can convert the DC power into AC power in phase with the same frequency of the power grid, and realize the grid connection of the renewable energy and the commercial power.

Structurally, the primary side switching circuit 120 and the resonant circuit 140 form a primary side circuit of the power converter 100, and are electrically coupled to the primary winding Np of the transformer 160. Specifically, the input side of the primary side switching circuit 120 is electrically connected to the input voltage source for receiving the DC input voltage Vin. The output side of the primary switching circuit 120 is electrically coupled to the input side of the resonant circuit 140 for outputting a square wave signal to the resonant circuit 140. The output side of the resonant circuit 140 is electrically connected to the primary winding Np of the transformer 160. The secondary winding Ns of the transformer 160 is electrically connected to the input side of the secondary rectifier circuit 180. The output side of the secondary side rectifier circuit 180 is electrically coupled to the output capacitor Co to provide a DC output voltage Vo to the subsequent stage circuit. In this way, the primary side switching circuit 120, the resonant circuit 140, the transformer 160, and the secondary side rectifier circuit 180 can form the circuit architecture of the LLC resonant converter.

In addition, as shown in FIG. 1 , the voltage detecting circuit 110 is electrically coupled to the two ends of the primary winding Np for detecting the voltage across the primary winding Np and outputting the voltage detecting signal Sig_V. The current detecting circuit 130 is disposed on the line of the resonant circuit 140 to detect the primary current Ip flowing through the resonant circuit 140. For example, the voltage detecting circuit 110 can include a voltage detecting unit 112 and a rectifying unit 114. The current detecting circuit 130 can include a current detecting unit 132 and a rectifying unit 134. In some embodiments, the voltage detecting unit 112 and the current detecting unit 132 can be implemented by using an induction coil or the like, but the disclosure is not limited thereto. The rectifying unit 114 is electrically coupled to the voltage detecting unit 112 for rectifying the detection signal obtained by the voltage detecting unit 112, so that the output voltage detecting signal Sig_V represents the magnitude of the voltage across the primary winding Np. The rectifying unit 134 is electrically coupled to the current detecting unit 132 for rectifying the detecting signal obtained by the current detecting unit 132 to output a current detecting signal Sig_I representing the magnitude of the primary current Ip.

Structurally, the processing circuit 150 is electrically connected to the voltage detecting circuit 110 and the current detecting circuit 130. The driving circuit 170 is electrically connected between the processing circuit 150 and the primary switching circuit 120. In some embodiments, the processing circuit 150 may include a Voltage-To-Frequency Converter for outputting a Pulse Frequency Modulation (PFM) according to the voltage detection signal Sig_V and the current detection signal Sig_I. Signal PFM to drive circuit 170. After receiving the pulse frequency modulation signal PFM from the processing circuit 150, the driving circuit 170 can output a plurality of driving signals CS1 CS CS4 to the switches S1 S S4 in the primary switching circuit 120 according to the pulse frequency modulation signal PFM. The switching frequency switching switches S1 to S4 of the signals CS1 to CS4 are turned on and off. Thereby, the processing circuit 150 can change the switching frequency of the square wave signal output by the primary side switching circuit 120 through the pulse frequency modulation signal PFM. In some embodiments, the voltage to frequency converter in processing circuit 150 can be implemented by various circuits, such as an integrator and a comparator, the details of which are not described herein.

Thereby, as the switching frequency of the square wave signal output by the primary switching circuit 120 changes, the impedance of the resonant circuit 140 also changes with the switching frequency. As a result, the voltage of the primary winding Np of the transformer 160 changes with the change of the switching frequency, and the corresponding DC output voltage Vo is outputted via the secondary winding Ns of the secondary side and the secondary rectifier circuit 180. In other words, the DC output voltage Vo can be controlled by the switching frequency of the driving signals CS1 to CS4.

In particular, in various embodiments, primary switching circuit 120 can be implemented through a half bridge, full bridge, or other type of switching circuit. For example, in the embodiment shown in FIG. 1, the primary side switching circuit 120 can be implemented by a full bridge circuit. The primary side switching circuit 120 includes switches S1, S2, S3, and S4. As shown, the first end of the switch S1 is electrically connected to the positive terminal of the input voltage source. The second end of the switch S1 is electrically connected to the first end of the resonant circuit 140. The first end of the switch S2 is electrically connected to the first end of the resonant circuit 140. The second end of the switch S2 is electrically connected to the negative terminal of the input voltage source. The first end of the switch S3 is electrically connected to the positive terminal of the input voltage source. The second end of the switch S3 is electrically connected to the second end of the resonant circuit 140. The first end of the switch S4 is electrically connected to the second end of the resonant circuit 140. The second end of the switch S4 is electrically connected to the negative terminal of the input voltage source.

Therefore, when the switches S1 and S4 are turned on according to the corresponding driving signals CS1 and CS4, and the switches S2 and S3 are turned off according to the corresponding driving signals CS2 and CS3, the first end of the resonant circuit 140 is electrically connected to the positive input source. Extremely, the second end of the resonant circuit 140 is electrically coupled to the negative terminal of the input voltage source. In contrast, when the switches S1 and S4 are turned off according to the corresponding driving signals CS1 and CS4, and the switches S2 and S3 are turned on according to the corresponding driving signals CS2 and CS3, the first end of the resonant circuit 140 is electrically connected to the negative of the input voltage source. Extremely, the second end of the resonant circuit 140 is electrically coupled to the positive terminal of the input voltage source. In this way, the primary side switching circuit 120 can switch the opening and closing of the switches S1 to S4 according to the switching frequency, and convert the DC input voltage Vin into a square wave signal with a duty cycle of 50% to be transmitted to the resonant circuit 140.

In some embodiments, the resonant circuit 140 includes a resonant capacitor unit Cr and a resonant inductor unit Lr. Structurally, the resonant capacitor unit Cr and the resonant inductor unit Lr are connected in series to each other. For example, as shown in FIG. 1, the first end of the resonant capacitor unit Cr is electrically connected to the first end of the resonant circuit 140 to be electrically connected to the switches S1 and S2. The second end of the resonant capacitor unit Cr is electrically connected to the first end of the resonant inductor unit Lr. The second end of the resonant inductor unit Lr is electrically connected to the first end of the primary winding Np. The second end of the primary winding Np is electrically connected to the second end of the resonant circuit 140 to be electrically connected to the switches S3 and S4, but the disclosure is not limited thereto. In some embodiments, the resonant inductor unit Lr may be formed by the leakage inductance of the transformer 160. In other embodiments, the resonant capacitor unit Cr and the resonant inductor unit Lr can also be electrically connected in different manners and matched with the magnetizing inductance in the transformer 160 to implement the LLC resonant circuit.

In this way, the primary winding Np can receive the primary side square wave signal from the resonant circuit 140. The secondary winding Ns can output the secondary side alternating current signal to the secondary side rectifier circuit 180 corresponding to the primary side square wave signal, so that the transformer 160 realizes energy transfer between the primary side and the secondary side.

In various embodiments, secondary rectifier circuit 180 can be implemented through a half bridge, full bridge, or other type of rectifier circuit. For example, in the embodiment shown in FIG. 1, the secondary side rectifier circuit 180 can be implemented by a full bridge rectifier circuit. The secondary side rectifier circuit 180 includes diodes D1, D2, D3, and D4. As shown, the anode end of the diode D1 is electrically connected to the first end of the secondary winding Ns, and the cathode end of the diode D1 is electrically connected to the first end of the output capacitor Co. The anode end of the diode D2 is electrically connected to the second end of the output capacitor Co, and the cathode end of the diode D2 is electrically connected to the anode end of the diode D1. The anode end of the diode D3 is electrically connected to the second end of the secondary winding Ns. The cathode end of the diode D3 is electrically connected to the first end of the output capacitor Co. The anode end of the diode D4 is electrically connected to the second end of the output capacitor Co, and the cathode end of the diode D4 is electrically connected to the anode end of the diode D3.

Thereby, the secondary side alternating current signal Vo is outputted by the secondary side rectifying circuit 180 and the output capacitor Co rectifying and filtering the secondary side alternating current signal induced and output by the secondary side winding Ns.

In this way, through the operation of the above circuit, the power converter 100 can convert the DC input voltage Vin into a DC output voltage Vo having an appropriate voltage level to be supplied to the subsequent stage circuit.

It is worth noting that in some embodiments, the DC output voltage Vo is a medium voltage level. When the power converter 100 directly detects the DC output voltage Vo of the secondary side and returns the signal to the primary side, the feedback voltage of the secondary side needs to be returned to the primary side by the isolation component with high withstand voltage and current resistance. Lead to rising costs. In some embodiments of the present invention, the voltage across the primary side winding Np of the primary side of the power converter 100 can be directly detected by the voltage detecting circuit 110 and transmitted through the processing circuit 150 according to the transformer model corresponding to the transformer 160. The relationship between the voltage across the primary winding Np and the output voltage Vo is adjusted according to the pulse signal, so that the primary switching circuit 120 switches the switches S1 to S4 according to the pulse signal to convert the DC input voltage Vin into a square. Wave signal. In this way, the processing circuit 150 can adjust the switching frequency of the switches S1 S S4 through the pulse signal to control the output voltage Vo. The following paragraphs will be described in detail with respect to the transformer model of the transformer 160, the relationship between the voltage across the primary winding Np and the output voltage Vo, and the specific operation of the processing circuit 150 to adjust the switching frequency of the switches S1 to S4.

Please refer to Figure 2. FIG. 2 is a schematic diagram of a transformer model of transformer 160 according to some embodiments of the present disclosure. As shown in FIG. 2, in some embodiments, the equivalent circuit model of the transformer 160 includes a primary winding resistance Rp, a primary leakage inductance Lp, a secondary winding resistance Rs, a secondary leakage inductance Ls, and a magnetizing inductance Lm. And an ideal primary winding Np and a secondary winding Ns. Specifically, the primary winding resistance Rp and the secondary winding resistance Rs represent the copper losses of the primary and secondary sides in the transformer 160, respectively.

It is worth noting that the transformer equivalent circuit model shown in Figure 2 is for illustrative purposes only and is not intended to limit the case. For example, in other embodiments, the transformer equivalent circuit model may further include a hysteresis iron loss resistance on the excitation branch or ignore the magnetization inductance Lm on the excitation branch to simplify the equivalent circuit. Since the voltage levels of the primary side and the secondary side of the transformer are different, in order to facilitate circuit analysis, the transformer equivalent circuit model can be further referred to the primary side or the secondary side.

Please refer to Figure 3. FIG. 3 is a schematic diagram of an equivalent circuit model of the primary side voltage Vp and the output voltage Vo after the transformer 160 is referenced to the primary side according to some embodiments of the present disclosure, wherein Rtrace represents the trace resistance, and Vd1 and Vd2 represent the pair. The diode in the side rectifying circuit 180 turns on the voltage drop and ignores the magnetizing inductance Lm and the hysteresis iron loss resistance on the excitation branch to simplify the equivalent circuit.

Specifically, the turns ratio a between the primary winding Np and the secondary winding Ns represents the ratio of the voltage Vp of the primary winding Np to the voltage Vs of the secondary winding Ns, and also represents the primary current Ip and The inverse ratio of the secondary current Is. Therefore, the turns ratio a can be expressed as the following formula.

Based on the above formula, when the equivalent circuit model of the transformer 160 illustrated in FIG. 2 is referenced to the primary side, the equivalent resistance value and the equivalent leakage inductance value of the primary winding resistance Rp and the primary leakage inductance Lp are not change. On the other hand, the equivalent resistance value after the reference to the primary side and the equivalent leakage inductance value of the secondary winding resistance Rs and the secondary leakage inductance Ls are multiplied by the equivalent value of the primary secondary winding resistance Rs and the secondary leakage inductance Ls. The number of turns is a squared ratio of a. Further, the voltage value on the secondary side of the transformer 160 is also multiplied by the turns ratio a to refer to the primary side, such as the diode turn-on voltage drops Vd1, Vd2 and the output voltage Vo in the secondary side rectifier circuit 180.

In order to explain the operational flow of the power converter 100 and the diode turn-on voltage drops Vd1, Vd2 in the secondary side rectifier circuit 180, please refer to FIGS. 4 and 5. 4 and 5 are schematic diagrams showing the operation of the power converter 100 according to some embodiments of the present disclosure. As shown in Fig. 4, in the upper half cycle, the switches S1, S4 are turned on. The primary current Ip flows into the primary winding Np, and transmits energy to the secondary winding Ns through the transformer 160, and finally outputs the current Id1 via the turned-on diodes D1, D4.

As shown in Fig. 5, in the second half cycle, switches S2 and S3 are turned on. The primary side current Ip flows in the opposite direction to the upper half period, flows into the primary winding Np, transmits energy to the secondary winding Ns through the transformer 160, and finally outputs the current Id3 via the turned-on diodes D2 and D3.

Therefore, regardless of the upper half cycle or the second half cycle, the voltage across the secondary winding Ns across the voltage Vs must pass through two sets of diode turn-on voltage drop Vd1 (eg, the turn-on voltage drop of the diode D1 or the diode D3). , Vd2 (such as: diode D2 or diode D4 conduction voltage drop).

In this way, the relationship between the voltage across the primary winding Np and the output voltage Vo can be obtained as the equivalent circuit model shown in FIG. Specifically, according to Figure 3, the relationship can be expressed as:

The above formula is available after finishing.

In this way, the voltage across the primary winding Np and the output voltage Vo can be expressed as a turns ratio a, a primary current Ip, a primary winding resistance Rp, a secondary winding resistance Rs, a trace resistance Rtrace, and two. The polar body conduction voltage drops Vd1 and Vd2 are used as a relational expression of calculation parameters. Among them, the primary winding resistance Rp, the secondary winding resistance Rs, and the routing resistance Rtrace can be further integrated into the equivalent resistance Req. (ie: the sum of Rp, a ² Rs, Rtrace).

Since the turns ratio a, the diode turn-on voltage drop Vd1, Vd2, and the related parameters in the equivalent resistance Req are all the hard parameters of the transformer 160 and the secondary side rectifier circuit 180, they can be regarded as known fixed values. Thereby, the processing circuit 150 can output a pulse signal (eg, a pulse frequency modulation signal PFM) according to the voltage detection signal Sig_V and the current detection signal Sig_I, and control the switching frequency of the driving signals CS1, CS2, CS3, and CS4.

For example, the processing circuit 150 can obtain the current voltage Vp of the primary winding Np and the value of the primary current Ip according to the voltage detection signal Sig_V and the current detection signal Sig_I, and calculate the current output voltage through the above relational model. The size of Vo is compared to the target value. When the current output voltage Vo is greater than the target value (eg, at light load), the processing circuit 150 may output a corresponding pulse frequency modulation signal PFM to the driving circuit 170, such as increasing the switching frequency of the driving signals CS1, CS2, CS3, CS4. In contrast, when the current output voltage Vo is less than the target value (eg, when the load is heavy), the processing circuit 150 may output the corresponding pulse frequency modulation signal PFM to the driving circuit 170, such as reducing the driving signals CS1, CS2, CS3, CS4. The frequency is switched to stabilize the output voltage Vo.

In other words, the processing circuit 150 can obtain the relationship between the voltage across the primary winding Np and the output voltage Vo through the transformer model, the primary current Ip, and the voltage drop of the diodes D1 to D4 in the secondary rectifier circuit 180. To adjust the switching frequency of the driving signals CS1, CS2, CS3, CS4.

In this way, when the DC output voltage Vo is at the medium voltage level, the power converter 100 does not need to detect the DC output voltage Vo of the secondary side, and is fed back to the primary side through the isolation element. In contrast, the voltage detection side signal and the current detection side signal as the feedback signal can be directly implemented on the primary side of the transformer 160. Since the signal feedback is on the same side of the processing circuit 150, the driving circuit 170, and the primary switching circuit 120, the signal conversion is not required through the isolation component, the circuit cost can be reduced, and the signal is prevented from being converted between the primary side and the secondary side. Error, which in turn improves the accuracy and speed of feedback control.

It should be noted that the equivalent circuit model shown in FIG. 3 is only one of the possible implementation modes of the present case, and is not intended to limit the case. For example, in other embodiments, in an application where the allowable error of the output voltage Vo is sufficient, the equivalent circuit model can be further simplified according to actual needs, and for example, the diode turn-on voltage drops Vd1, Vd2, etc. are omitted. System parameters. For example, in other embodiments, the equivalent circuit model can be more accurate in applications where the tolerance of the output voltage Vo is relatively accurate. For example, the system parameters such as the diode turn-on voltage drop Vd1, Vd2 can be based on the flow. The model is further developed by current and temperature. In other words, those skilled in the art can use a suitable transformer model or a different relationship to calculate the relationship between the voltage across the primary winding Np and the output voltage Vo.

Please refer to Figure 6. FIG. 6 is a flow chart of a method 600 of controlling the power converter 100 in accordance with some embodiments of the present disclosure. For convenience and clarity of description, the following control method 600 is described with reference to the embodiments shown in FIGS. 1 to 5, but is not limited thereto, and any person skilled in the art can avoid the spirit of the disclosure. And within the scope, when the various changes and retouching can be made. As shown in FIG. 6, the control method 600 includes steps S610, S620, S630, and S640.

First, in step S610, the current detecting circuit 130 in the power converter 100 detects the primary current Ip flowing through the primary side circuit of the power converter 100 to obtain the current detecting signal Sig_I.

In step S620, the voltage detecting circuit 110 in the power converter 100 detects the voltage across the primary winding Np of the transformer 160 in the power converter 100 that is electrically coupled to the primary winding Np of the primary circuit. Obtain the voltage detection signal Sig_V.

In step S630, the relationship between the voltage across the primary winding Np and the output voltage Vo of the power converter 100 is obtained by the transformer model corresponding to the transformer 160.

Specifically, in some embodiments, the transformer model includes a turns ratio parameter, a primary winding resistance parameter, and a secondary winding resistance parameter, and the step S630 includes a transmission transformer model, a primary current Ip, and a secondary side of the power converter 100. The voltage drop of the diodes D1 to D4 in the rectifier circuit 180 obtains a relational expression between the voltage across the primary winding Np and the output voltage Vo.

In step S640, based on the relationship between the voltage across the primary winding Np and the output voltage Vo, the switching frequency of the switches S1 to S4 in the primary circuit is controlled according to the voltage detection signal Sig_V and the current detection signal Sig_I to adjust Output voltage Vo.

Specifically, in some embodiments, the switching frequency of the control switches S1 to S4 in step S640 includes: calculating, by the processing circuit 150, the pulse frequency modulation signal PFM according to the current detection signal Sig_I and the voltage detection signal Sig_V; The pulse frequency modulation signal PFM is received by the driving circuit 170, and the switching signals S1 to S4 are selectively turned on or off according to the pulse frequency modulation signal PFM output driving signals CS1 to CS4, respectively, to adjust the switching frequency of the switches S1 to S4.

Those skilled in the art can directly understand how this control method 600 is based on the power converter 100 in the above various embodiments to perform such operations and functions, and thus will not be described again.

While the methods disclosed are shown and described herein as a series of steps or events, it is understood that the order of the steps or events shown should not be construed as limiting. For example, some of the steps may occur in a different order and/or concurrently with other steps or events other than those illustrated or/or described herein. In addition, not all of the steps shown herein are required in the practice of one or more aspects or embodiments described herein. Moreover, one or more steps herein may also be performed in one or more separate steps and/or stages.

The present disclosure has been disclosed in the above embodiments, and is not intended to limit the disclosure, and the present disclosure may be variously modified and retouched without departing from the spirit and scope of the present disclosure. The scope of protection of the content is subject to the definition of the scope of the patent application.

100‧‧‧Power Converter

110‧‧‧Voltage detection circuit

112‧‧‧Voltage detection unit

114‧‧‧Rectifier unit

120‧‧‧ primary switching circuit

130‧‧‧ Current detection circuit

132‧‧‧current detection unit

134‧‧‧Rectifier unit

140‧‧‧Resonance circuit

150‧‧‧Processing circuit

160‧‧‧Transformers

170‧‧‧ drive circuit

180‧‧‧Sub-side rectifier circuit

600‧‧‧Control method

S610～S640‧‧‧Steps

S1～S4‧‧‧ switch

D1～D4‧‧‧ diode

Cr‧‧‧Resonant capacitor unit

Lr‧‧‧Resonant Inductance Unit

Lm‧‧‧ Magnetized Inductance

Np‧‧‧ primary winding

Ns‧‧‧ secondary winding

Co‧‧‧ output capacitor

PFM‧‧‧ pulse frequency modulation signal

CS1～CS4‧‧‧ drive signal

Sig_I‧‧‧current detection signal

Sig_V‧‧‧ voltage detection signal

Vin‧‧‧Input voltage

Vo‧‧‧ output voltage

Vp, Vs‧‧‧ cross pressure

Ip‧‧‧ primary current

Is‧‧‧ secondary current

A‧‧‧ turns ratio

Rp‧‧‧ primary winding resistance

Lp‧‧‧ primary leakage inductance

Rs‧‧‧ secondary winding resistance

Ls‧‧‧Subside leakage inductance

Rtrace‧‧‧Wire resistance

Vd1, Vd2‧‧‧ diode conduction voltage drop

Id1, Id3‧‧‧ current

FIG. 1 is a schematic diagram of a power converter according to some embodiments of the present disclosure. FIG. 2 is a schematic diagram of a transformer model according to some embodiments of the present disclosure. FIG. 3 is a schematic diagram of an equivalent circuit model of the primary side voltage and the output voltage after the transformer is referenced to the primary side according to some embodiments of the present disclosure. 4 and 5 are schematic diagrams showing the operation of the power converter according to some embodiments of the present disclosure. FIG. 6 is a flow chart of a method of controlling a power converter according to some embodiments of the present disclosure.

Claims (20)

A power converter comprising: a primary switching circuit comprising a plurality of switches, wherein the primary switching circuit switches the switching of the switches according to a pulse signal to convert the DC input voltage into a one-way signal; a resonant circuit electrically connected to the primary switching circuit for receiving the square wave signal to provide a primary current; a transformer, wherein a primary winding of the transformer is electrically connected to the resonant circuit; The circuit is electrically connected to a secondary winding of the transformer for rectifying a secondary AC signal outputted by the secondary winding and outputting an output voltage; a voltage detecting circuit for detecting the primary winding The voltage across the two ends is outputted by a voltage detecting signal; a current detecting circuit for detecting the primary current and outputting a current detecting signal; and a processing circuit for detecting the voltage according to the voltage detecting circuit The signal and the current detecting signal output the pulse signal. The power converter of claim 1, wherein the processing circuit is configured to adjust a switching frequency of the switches through the pulse signal to control the output voltage. The power converter of claim 2, wherein the processing circuit obtains a relationship between a voltage across the primary winding and the output voltage through a transformer model corresponding to the transformer, thereby adjusting the pulse signal. The power converter of claim 3, wherein the transformer model includes a turns ratio parameter, a primary winding resistance parameter, and a secondary winding resistance parameter. The power converter of claim 3, wherein the processing circuit further obtains a voltage across the transformer winding, the primary current, and a voltage drop of the diode in the secondary rectifier circuit to obtain a voltage across the primary winding The relationship between the output voltages. The power converter of claim 2, further comprising a driving circuit electrically connected to the processing circuit and the switches in the primary switching circuit, the driving circuit respectively outputting a plurality of signals according to the pulse signal Drive signals to the switches to switch the switches on and off. The power converter of claim 1, wherein the resonant circuit comprises a resonant capacitor unit and a resonant inductor unit connected in series with each other. The power converter of claim 1, wherein the switches comprise: a first switch, a first end of the first switch is electrically connected to a positive terminal of an input voltage source, and the first switch The second end is electrically connected to a first end of the resonant circuit; a second switch, a first end of the second switch is electrically connected to the first end of the resonant circuit, and a second end of the second switch The second end is electrically connected to a negative end of the input voltage source; a third switch, a first end of the third switch is electrically connected to the positive end of the input voltage source, and a second end of the third switch The first end of the fourth switch is electrically connected to the second end of the resonant circuit, and the second end of the fourth switch is electrically connected to a second end of the resonant circuit, and a fourth switch The terminal is electrically connected to the negative terminal of the input voltage source. The power converter of claim 1, wherein the secondary rectifier circuit comprises: a first diode, an anode end of the first diode is electrically connected to a first end of the secondary winding, a cathode end of the first diode is electrically connected to a first end of an output capacitor; a second diode, an anode end of the second diode is electrically connected to a second end of the output capacitor a cathode end of the second diode is electrically connected to the anode end of the first diode; a third diode, an anode end of the third diode is electrically connected to the secondary winding a second end of the third diode is electrically connected to the first end of the output capacitor; and a fourth diode, an anode end of the fourth diode is electrically connected to The second end of the output capacitor is electrically connected to the anode end of the third diode. A power converter comprising: a primary circuit comprising a plurality of switches respectively for selectively turning on or off according to a plurality of driving signals; a transformer comprising: a primary winding electrically connected to The primary circuit is configured to receive a primary side square wave signal from the primary side circuit; and a secondary side winding for outputting a secondary side alternating current signal corresponding to the primary side square wave signal; a voltage detecting circuit Detecting a voltage across the primary winding and outputting a voltage detection signal; a current detecting circuit for detecting a primary current flowing through the primary circuit and outputting a current according to the primary current a current detecting signal; a secondary side rectifying circuit electrically connected to the secondary winding for rectifying the secondary side alternating current signal and outputting an output voltage; and a processing circuit for detecting the signal according to the voltage The current detection signal controls a switching frequency of the driving signals. The power converter of claim 10, wherein the processing circuit obtains a relationship between a voltage across the primary winding and the output voltage through a transformer model corresponding to the transformer, thereby adjusting the switching frequency. The power converter of claim 11, wherein the transformer model includes a turns ratio parameter, a primary winding resistance parameter, and a secondary winding resistance parameter. The power converter of claim 11, wherein the processing circuit further obtains a voltage across the transformer winding, the primary current, and a voltage drop of the diode in the secondary rectifier circuit, and obtains a voltage across the primary winding The relationship between the output voltages. The power converter of claim 10, further comprising a driving circuit electrically connected to the processing circuit and the switches in the primary circuit, the processing circuit detecting the signal and the current according to the voltage The detection signal outputs a pulse frequency modulation signal, and the driving circuit outputs the driving signals to the switches according to the pulse frequency modulation signal to switch the opening and closing of the switches. The power converter of claim 10, wherein the primary circuit further comprises a resonant circuit comprising a resonant capacitor unit and a resonant inductor unit connected in series with each other. The power converter of claim 15, wherein the switches in the primary side circuit comprise: a first switch, a first end of the first switch is electrically connected to a positive terminal of an input voltage source, a second end of the first switch is electrically connected to a first end of the resonant circuit; a second switch is electrically connected to a first end of the second switch a second end of the second switch is electrically connected to a negative end of the input voltage source; a third switch, a first end of the third switch is electrically connected to the positive end of the input voltage source, the first a second end of the third switch is electrically connected to a second end of the resonant circuit; and a fourth switch, a first end of the fourth switch is electrically connected to the second end of the resonant circuit, the first A second end of the four switch is electrically connected to the negative end of the input voltage source. The power converter of claim 10, wherein the secondary rectifier circuit comprises: a first diode, an anode end of the first diode is electrically connected to a first end of the secondary winding, a cathode end of the first diode is electrically connected to a first end of an output capacitor; a second diode, an anode end of the second diode is electrically connected to a second end of the output capacitor a cathode end of the second diode is electrically connected to the anode end of the first diode; a third diode, an anode end of the third diode is electrically connected to the secondary winding a second end of the third diode is electrically connected to the first end of the output capacitor; and a fourth diode, an anode end of the fourth diode is electrically connected to The second end of the output capacitor is electrically connected to the anode end of the third diode. A method for controlling a power converter includes: detecting, by a current detecting circuit in a power converter, a primary current flowing through a primary circuit of the power converter to obtain a current detecting signal; A voltage detecting circuit of the power converter detects a voltage across a primary winding of a power transformer in the power converter to obtain a voltage detecting signal; Obtaining a relationship between a voltage across the primary winding and an output voltage of the power converter through a transformer model corresponding to the transformer; and based on a relationship between a voltage across the primary winding and the output voltage, The switching frequency of the plurality of switches in the primary circuit is controlled according to the voltage detection signal and the current detection signal to adjust the output voltage. The control method of the power converter according to claim 18, wherein the transformer model includes a turns ratio parameter, a primary winding resistance parameter, and a secondary winding resistance parameter, and the cross voltage between the two ends of the primary winding is obtained. The relationship between the output voltages further includes: obtaining the voltage across the primary winding and the output voltage through the transformer model, the primary current, and the voltage drop of the diode in a secondary rectifier circuit of the power converter Relationship. The control method of the power converter of claim 18, wherein controlling the switching frequency of the switches comprises: calculating, by the processing circuit, a pulse frequency modulation signal according to the current detection signal and the voltage detection signal And receiving, by the driving circuit, the pulse frequency modulation signal, and outputting the plurality of driving signals according to the pulse frequency modulation signal to selectively turn on or off the switches to adjust the switching frequency of the switches.