Active clamp voltage conversion circuit and controller thereof

Abstract

An active clamp voltage conversion circuit and a controller thereof. The active clamp voltage conversion circuit includes a switching power supply circuit, an active clamp circuit, a current detector, a pulse width modulation controller, and a positive and negative voltage controller. The switching power supply circuit includes a transformer and a first switch. The first switch is coupled to a primary ground of the transformer. The active clamp circuit includes a second switch. The current detector is coupled between the primary ground and the second switch to generate a current detection signal. The current detection signal indicates a current flowing through the second switch. The pulse width modulation controller generates a pulse width modulation signal to the first switch to switch the first switch. The positive and negative voltage controller selectively outputs a negative voltage to the second switch according to the current detection signal during a dead time of the first switch and the second switch.

Description

Technical Field

[0001] A voltage conversion circuit, particularly an active clamping voltage conversion circuit and its controller. Background Technology

[0002] Current flyback architectures incorporate a CLC resonant circuit on the secondary side. This CLC resonant circuit lowers the secondary-side voltage, allowing for better transfer of primary-side excitation energy to the secondary side. However, the CLC resonant circuit contains capacitors, inductors, and other space-consuming electronic components, which inevitably contradicts the need to reduce product size. Summary of the Invention

[0003] In view of this, in some embodiments, an active clamping voltage conversion circuit is provided, comprising a switching power supply circuit, an active clamping circuit, a current detector, a pulse width modulation controller, and a positive / negative voltage controller. The switching power supply circuit includes a transformer and a first switch. The primary winding of the transformer has a main power terminal and a main ground terminal, and the first switch is coupled to the main ground terminal of the transformer. The active clamping circuit is coupled in parallel to the primary winding of the transformer and includes a second switch. The current detector is coupled between the main ground terminal of the transformer and the second switch to generate a current detection signal. The current detection signal indicates the current flowing through the second switch. The pulse width modulation controller is coupled to the first switch and generates a pulse width modulation signal to the first switch to switch the first switch. The positive / negative voltage controller is coupled to the second switch and the current detector, and selectively outputs a negative voltage to the second switch based on the current detection signal during the dead time between the first and second switches.

[0004] In some embodiments, a controller is provided for performing: generating a pulse width modulation signal to a first switch to cause the first switch to switch operation; obtaining a current detection signal indicating the current flowing through a second switch; and selectively outputting a negative voltage to the second switch based on the current detection signal during the dead time between the first switch and the second switch.

[0005] In summary, the active clamping voltage conversion circuit and its control method according to some embodiments of the present invention increase the voltage of the primary coil by sending a negative voltage to the second switch. This helps to transfer more excitation energy from the primary coil to the secondary coil, while reducing the flow of excitation energy to the clamping capacitor, thereby reducing losses in the energy recovery process. Furthermore, because the voltage of the primary coil is increased, there is no need to add a CLC-type resonant circuit on the secondary side of the transformer to reduce the voltage. Therefore, the hardware cost and volume of the CLC-type resonant circuit can be eliminated, which is beneficial for product miniaturization.

[0006] The following detailed description of the features and advantages of the present invention is sufficient to enable any person skilled in the art to understand the technical content of the present invention and implement it accordingly. Based on the content disclosed in this specification, the claims and the drawings, any person skilled in the art can easily understand the relevant objectives and advantages of the present invention. Attached Figure Description

[0007] Figure 1 This is a block diagram of an active clamping voltage conversion circuit in some embodiments of the present invention;

[0008] Figure 2 This is a circuit diagram of an active clamping voltage conversion circuit in some embodiments of the present invention;

[0009] Figure 3 This is a timing diagram of the signals received by the first switch and the second switch in some embodiments of the present invention;

[0010] Figure 4 This is a circuit diagram of the positive and negative pressure controller in some embodiments of the present invention;

[0011] Figure 5 This is a flowchart illustrating the control method of the active clamping voltage conversion circuit in some embodiments of the present invention;

[0012] Figure 6A Here is a comparative example of the current waveform at the main power supply terminal.

[0013] Figure 6B This is a current waveform diagram at the main power supply terminal in some embodiments of the present invention.

[0014] [Symbol Explanation]

[0015] 10: Input power

[0016] 100: Active clamping voltage conversion circuit

[0017] 102: Switching power supply circuit

[0018] 104: Active clamping circuit

[0019] 106: Current Detector

[0020] 108: Pulse Width Modulation Controller

[0021] 110: Positive and negative pressure controller

[0022] 112: Transformer

[0023] 114: First Switch

[0024] 114a, 122a: First end

[0025] 114b, 122b: Second end

[0026] 114c, 122c: Control terminals

[0027] 116: Main power supply terminal

[0028] 118: Main Location

[0029] 120: Primary side coil

[0030] 120': Secondary side coil

[0031] 122: Second Switch

[0032] 124: Positive and negative voltage generator

[0033] 126: Comparator

[0034] 128: Feedback Controller

[0035] 130: Controller

[0036] 200: Electronic devices

[0037] Sn1: Current detection signal

[0038] Sn2, Sn3: Pulse width modulation signals

[0039] Sn4: Positive and negative voltage signals

[0040] Sn5: Feedback signal

[0041] C1: Output capacitor

[0042] C2: Clamping capacitor

[0043] D1: Diode

[0044] DT1, DT2: Dead Time

[0045] T1, T2: Time points

[0046] S1, S2, S3, S4: Steps Detailed Implementation

[0047] Please see Figure 1 The active clamping voltage converter circuit 100 includes a switching power supply circuit 102, an active clamping circuit 104, a current detector 106, a pulse width modulation controller 108, and a positive / negative voltage controller 110. The switching power supply circuit 102 receives an input voltage provided by an input power source 10 and performs power conversion to generate an output voltage. Here, as an example, the active clamping voltage converter circuit 100 is coupled to an electronic device 200 to provide the output voltage to the electronic device 200.

[0048] The active clamping circuit 104 is connected in parallel with the switching power supply circuit 102 to reduce switching losses, voltage stress, and improve power conversion efficiency. A current detector 106 is coupled between the switching power supply circuit 102 and the active clamping circuit 104 and generates a current detection signal Sn1 to detect the current flowing from the switching power supply circuit 102 to the active clamping circuit 104. A pulse width modulation (PWM) controller 108 generates two PWM signals Sn2 and Sn3. The PWM controller 108 is coupled to the switching power supply circuit 102 to output one of the PWM signals Sn2 to control the operation of the switching power supply circuit 102. The PWM controller 108 is also coupled to a positive and negative voltage controller 110 to output the two PWM signals Sn2 and Sn3 to the positive and negative voltage controller 110. The positive and negative voltage controller 110 is coupled to the active clamping circuit 104, the current detector 106 and the pulse width modulation controller 108 to receive the two pulse width modulation signals Sn2 and Sn3 and the current detection signal Sn1, and output a positive and negative voltage signal Sn4 to control the operation of the active clamping circuit 104 via the positive and negative voltage signal Sn4.

[0049] Please refer to both together. Figure 2 and Figure 3 The switching power supply circuit 102 includes a transformer 112 and a first switch 114. The transformer 112 has a primary winding 120 and a secondary winding 120'. The primary winding 120 of the transformer 112 has a main power supply terminal 116 and a main ground terminal 118. The main power supply terminal 116 is coupled to the input power supply 10. The first switch 114 is coupled to the main ground terminal 118 of the transformer 112. Here, the switching power supply circuit 102 is exemplified by a flyback converter. Therefore, the switching power supply circuit 102 also includes a diode D1 and an output capacitor C1. The anode of the diode D1 is coupled to the secondary winding 120' of the transformer 112, and the cathode of the diode D1 is coupled to the output capacitor C1.

[0050] In some embodiments, the first switch 114 is a metal-oxide-semiconductor field-effect transistor (MOSFET). The first switch 114 has a first terminal 114a, a second terminal 114b, and a control terminal 114c, which are the drain, source, and gate, respectively. The first terminal 114a is coupled to a ground terminal 118, and the second terminal 114b is coupled to ground. The control terminal 114c is coupled to a pulse width modulation controller 108 to receive a pulse width modulation signal Sn2 output by the pulse width modulation controller 108, thereby determining whether the first switch 114 is turned on or off. Here, when the pulse width modulation signal Sn2 is at a high level, the first switch 114 is turned on; when the pulse width modulation signal Sn2 is at a low level, the first switch 114 is turned off. In some embodiments, the first switch 114 is a gallium nitride field-effect transistor (GaN FET).

[0051] When the first switch 114 is turned on, the input power supply 10 transmits current to the primary coil 120 of the transformer 112 for excitation, and the excitation energy is stored in the primary coil 120. At this time, the induced voltage of the secondary coil 120' of the transformer 112 is negative, causing the diode D1 to be reverse biased (turned off), and the output voltage is supplied by the output capacitor C1 coupled to the secondary coil 120'. When the first switch 114 is turned off, the excitation energy is coupled to the secondary coil 120', and the voltage polarity of the secondary coil 120' is reversed, causing the diode D1 to be forward biased (turned on), thus providing the output voltage to the electronic device 200.

[0052] An active clamping circuit 104 is connected in parallel to the primary winding 120 of transformer 112 to absorb the voltage spike generated on the first switch 114 by the leakage inductance of transformer 112 at the moment the first switch 114 is turned off. The active clamping circuit 104 includes a second switch 122 and a clamping capacitor C2. The second switch 122 and the clamping capacitor C2 are connected in series and coupled between the input power supply 10 and the main ground terminal 118 of transformer 112. After the first switch 114 is turned off, the second switch 122 is turned on, allowing the leakage inductance energy of transformer 112 to be stored in the clamping capacitor C2.

[0053] In some embodiments, the second switch 122 is a gallium nitride field-effect transistor. The second switch 122 has a first terminal 122a, a second terminal 122b, and a control terminal 122c, which are the source, drain, and gate, respectively. Here, the first terminal 122a is coupled to the main ground terminal 118 of the transformer 112, and the second terminal 122b is coupled to the clamping capacitor C2. The control terminal 122c is coupled to the positive and negative voltage controller 110 to receive the positive and negative voltage signals Sn4 output by the positive and negative voltage controller 110, thereby determining whether the second switch 122 is turned on or off. When the positive and negative voltage signal Sn4 is a positive voltage, the second switch 122 is turned on; when the positive and negative voltage signal Sn4 is a negative voltage or zero voltage, the second switch 122 is turned off.

[0054] Specifically, at the instant the first switch 114 is turned off (the pulse width modulation signal Sn2 changes from a high level to a low level), excitation energy is coupled to the secondary coil 120', and energy that fails to couple to the secondary coil 120' (i.e., leakage inductance energy) is also generated simultaneously. When the second switch 122 is turned on (the positive and negative voltage signals Sn4 are positive), the leakage inductance energy is transferred to the clamping capacitor C2, and this recovered energy can be reused. It should be noted that, due to the characteristics of gallium nitride field-effect transistors (unlike metal-oxide-semiconductor field-effect transistors which have a body diode), when a negative voltage is applied to the control terminal 122c of the second switch 122, the gallium nitride field-effect transistor operates in reverse conduction mode (i.e., the third quadrant), and has a forward voltage across the voltage V. F (As shown in Equation 1). V TH(GD) V is the threshold voltage between the gate and drain. GS(OFF) I is the gate-source voltage of the transistor in the off state. SD R is the current from the source to the drain. SD(ON) V is the equivalent channel resistance. F with I SD Proportional. Therefore, the forward transvoltage V of a gallium nitride field-effect transistor operating in reverse conduction mode is proportional. F Increasing the voltage of the primary coil 120 (making the voltage of the primary coil 120 greater than that of the secondary coil 120') helps to transfer more of the energy stored in the primary coil 120 to the secondary coil 120' (improving conversion efficiency), while reducing the flow of excitation energy to the clamping capacitor C2 (reducing energy loss during the recovery process).

[0055] V F =V TH +V GS(OFF) +I SD *R SD(ON) (Equation 1)

[0056] A current detector 106 is coupled between the main ground terminal 118 of the transformer 112 and the second switch 122. The current detector 106 detects the current (leakage inductance current) flowing from the transformer 112 to the second switch 122 to generate a current detection signal Sn1. That is, the current detection signal Sn1 indicates the current value flowing through the second switch 122. Here, the current detector 106 is used as an example with a resistor; the current detection signal Sn1 can be the voltage across the resistor.

[0057] After the first switch 114 is turned off and before the second switch 122 is turned on, that is, during a dead time (the period when both switches are off) of the first switch 114 and the second switch 122, the positive and negative voltage controller 110 selectively outputs a negative voltage to the second switch 122 according to the current detection signal Sn1, so as to help more excitation energy be transferred to the secondary coil 120'. In some embodiments, in response to the current detection signal Sn1 being greater than a threshold, the positive and negative voltage controller 110 outputs a negative voltage to the control terminal 122c of the second switch 122. Figure 3 As shown, when the dead time DT1 determines that the current detection signal Sn1 is greater than the threshold (taking 0 Amperes as an example), the positive and negative voltage controller 110 makes the positive and negative voltage signal Sn4 negative during the dead time DT2 of the next cycle. Conversely, the positive and negative voltage controller 110 makes the positive and negative voltage signal Sn4 zero during the dead time DT2 of the next cycle.

[0058] Please see Figure 4 In some embodiments, the positive and negative voltage controller 110 includes a positive and negative voltage generator 124 and a comparator 126. The positive and negative voltage generator 124 outputs positive and negative voltage signals Sn4. The comparator 126 receives a current detection signal Sn1 and a reference signal, respectively, and outputs a comparison result of the current detection signal Sn1 and the reference signal to the positive and negative voltage generator 124. Here, the reference signal serves as the aforementioned threshold. Thus, the positive and negative voltage generator 124 selectively generates a negative voltage based on the comparison result of the current detection signal Sn1 and the reference signal. For example, when the current detection signal Sn1 is greater than the reference signal, the comparator 126 generates a first comparison result, and the positive and negative voltage generator 124 generates a negative voltage based on the first comparison result. Conversely, when the reference signal is less than or equal to the reference signal, the comparator 126 generates a second comparison result, and the positive and negative voltage generator 124 generates a zero voltage based on the second comparison result.

[0059] The positive and negative voltage generator 124 also receives pulse width modulation signals Sn2 and Sn3 output from the pulse width modulation controller 108, thereby determining the dead time points of the first switch 114 and the second switch 122, so that the negative voltage level is within the correct dead time when it is required to generate a negative voltage. Specifically, the positive and negative voltage generator 124 can determine the off time point of the first switch 114 from the pulse width modulation signal Sn2, and the predetermined on and off times of the second switch 122 from the pulse width modulation signal Sn3. Therefore, the positive and negative voltage signal Sn4 is a high voltage during the period from the predetermined on time point to the predetermined off time point of the second switch 122, a negative voltage or zero voltage during the dead time, and a zero voltage at other times (i.e., during the on period of the first switch 114).

[0060] In some embodiments, the voltage value of the negative voltage is close to the upper limit of the negative voltage tolerance between the gate and source of the second switch 122, but the present invention is not limited thereto. For example, it can be any negative voltage value within the negative voltage tolerance range between the gate and source of the second switch 122.

[0061] In some embodiments, the negative voltage begins at a starting point of the dead time DT2. That is, the negative voltage begins when the pulse width modulation signal Sn2 changes from a high level to a low level. However, the invention is not limited thereto; for example, the negative voltage may occupy only a portion of the dead time DT2, rather than as shown. Figure 3 The diagram shows the entirety of the dead time DT2. The positive and negative voltage signals Sn4 are zero voltage during the non-negative voltage period within the dead time DT2.

[0062] In some embodiments, the positive and negative voltage controller 110 continues to output a positive voltage after the negative voltage is output, so as to immediately turn on the second switch 122 after increasing the voltage of the primary side coil 120.

[0063] In some embodiments, such as Figure 2 As shown, the active clamping voltage conversion circuit 100 also includes a feedback controller 128. The feedback controller 128 is coupled to the output capacitor C1 and the pulse width modulation controller 108, and generates a feedback signal Sn5 based on the output voltage. This feedback signal Sn5 indicates the voltage value of the output voltage. The pulse width modulation controller 108 receives the feedback signal Sn5 to adjust the pulse width modulation signals Sn2 and Sn3 according to the output voltage.

[0064] In some embodiments, the pulse width modulation controller 108, the positive and negative voltage controller 110, and the feedback controller 128 are located in a controller 130. The controller 130 is a microcontroller, a digital signal processor (DSP), a field-programmable gate array (FPGA), or an application-specific integrated circuit (ASIC).

[0065] Please see Figure 5 The controller 130 executes a control method with an active clamping voltage conversion circuit 100. The control method includes: generating a pulse width modulation signal Sn2 to the first switch 114 to switch the first switch 114 (step S1); obtaining a current detection signal Sn1, which indicates the current flowing through the second switch 122 (step S2); selectively outputting a negative voltage to the second switch 122 based on the current detection signal Sn1 during the dead time between the first switch 114 and the second switch 122 (step S3); and continuing to output a positive voltage after the negative voltage output ends (step S4). The detailed operations of these steps have been described above and will not be repeated here.

[0066] Please refer to the following: Figure 6A and Figure 6B . Figure 6A Here is a comparative example of the current waveform at the main power supply terminal 116; Figure 6B The following is a current waveform diagram of the main power supply terminal 116 in some embodiments of the present invention. Figure 6A and Figure 6B The waveform of the pulse width modulation signal Sn3 is shown below for comparison during the switching process of the second switch 122. For example... Figure 6A As shown, in the comparative example, no negative voltage is input to the second switch 122 during the dead time of the first switch 114 and the second switch 122 (i.e., zero input voltage); during the conduction period of the second switch 122, from time point T1 to time point T2, the current value at the main power supply terminal 116 changes from 1.66A to -0.96A. Figure 6B As shown, according to an embodiment of the present invention, a negative voltage is input to the second switch 122 during the dead time of the first switch 114 and the second switch 122; during the conduction period of the second switch 122, from time point T1 to time point T2, the current value at the main power supply terminal 116 changes from 1.48A to -0.86A. It can be seen that, compared to the comparative example, the embodiment of the present invention exhibits a smaller primary-side excitation current during energy coupling, indicating that more primary-side excitation energy is coupled to the secondary-side coil 120'.

[0067] In summary, the active clamping voltage conversion circuit 100 and its control method according to some embodiments of the present invention increase the voltage of the primary coil 120 by sending a negative voltage to the second switch 122. This helps to transfer more of the excitation energy of the primary coil 120 to the secondary coil 120', while reducing the flow of excitation energy to the clamping capacitor C2, thereby reducing losses in the energy recovery process. Furthermore, since the voltage of the primary coil 120 is increased, there is no need to add a CLC-type resonant circuit to the secondary side of the transformer 112 to reduce the voltage. Therefore, the hardware cost and volume of the CLC-type resonant circuit can be saved, which is beneficial for product miniaturization.

[0068] Although the technical content of the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any modifications and refinements made by those skilled in the art without departing from the spirit of the present invention should be included within the scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the appended claims.

Claims

1. An active clamping voltage conversion circuit, characterized in that, include: A switching power supply circuit includes a transformer and a first switch. A primary winding of the transformer has a main power terminal and a main ground terminal, and the first switch is coupled to the main ground terminal of the transformer. An active clamping circuit is coupled to the primary winding of the transformer and includes a second switch; A current detector is coupled between the main ground terminal of the transformer and the second switch to generate a current detection signal indicating the current flowing through the second switch; A pulse width modulation controller is coupled to the first switch and generates a pulse width modulation signal to the first switch to cause the first switch to switch operation; and A positive and negative voltage controller is coupled to the second switch and the current detector, and selectively outputs a negative voltage to the second switch according to the current detection signal during a dead time between the first switch and the second switch.

2. The active clamping voltage conversion circuit as described in claim 1, characterized in that, In response to the current detection signal being greater than a reference signal, the positive and negative voltage controller outputs the negative voltage to a control terminal of the second switch.

3. The active clamping voltage conversion circuit as described in claim 1, characterized in that, The positive and negative voltage controller also includes a positive and negative voltage generator and a comparator. The positive and negative voltage generator selectively generates the negative voltage based on a comparison result between the current detection signal and a reference signal by the comparator.

4. The active clamping voltage conversion circuit as described in claim 2 or 3, characterized in that, The reference signal is 0 amperes.

5. The active clamping voltage conversion circuit as described in claim 1, characterized in that, The negative voltage begins from the start point of the dead time.

6. The active clamping voltage conversion circuit as described in claim 1, characterized in that, The positive and negative voltage controller outputs a positive voltage after the negative voltage is output.

7. The active clamping voltage conversion circuit as described in claim 1, characterized in that, The negative voltage value is close to the upper limit of the negative voltage tolerance between the gate and the source of the second switch.

8. The active clamping voltage conversion circuit as described in claim 1, characterized in that, It also includes a feedback controller coupled to the primary side of the transformer and the pulse width modulation controller to transmit a feedback signal from the secondary side to the pulse width modulation controller, which generates the pulse width modulation signal based on the feedback signal.

9. A controller, characterized in that, Suitable for controlling an active clamping voltage conversion circuit, the active clamping voltage conversion circuit comprising a switching power supply circuit having a first switch and an active clamping circuit having a second switch, the controller being used to perform: A pulse width modulation signal is generated to the first switch to cause the first switch to switch operation; A current detection signal is obtained, which indicates the current flowing through the second switch; and During a dead time between the first switch and the second switch, a negative voltage is selectively output to the second switch based on the current detection signal.

10. The controller as claimed in claim 9, characterized in that, The relationship between selectively outputting the negative voltage to the second switch based on the current detection signal is as follows: in response to determining that the current detection signal is greater than a reference signal, the negative voltage is output to the second switch.

11. The controller as claimed in claim 10, characterized in that, The reference signal is 0 amperes.

12. The controller as claimed in claim 9, characterized in that, The negative voltage begins from the start point of the dead time.

13. The controller as claimed in claim 9, characterized in that, It is also used to: continue outputting a positive voltage after the negative voltage is output.

14. The controller as claimed in claim 9, characterized in that, The negative voltage value is close to the upper limit of the negative voltage tolerance between the gate and source of the second switch.

Images