A switching power supply boost circuit

Abstract

The present invention belongs to the technical field of power supply. The present invention is a switching power supply boost circuit, including a transformer, a first voltage output branch and a second voltage output branch are arranged on the secondary side of the transformer; the first voltage output branch includes a first diode and a first capacitor, and the second voltage output branch includes a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a second diode and a third diode; one end of the second capacitor is connected to the secondary winding, one end of the third capacitor is connected to the cathode of the first diode, the common end of the second capacitor and the third capacitor is connected to the anode of the third diode via the fourth capacitor, and the fifth capacitor is connected to the cathode of the third diode. A secondary boost branch is added on the basis of the flyback circuit, and the branch uses the peak voltage at the moment of switching to charge the boost capacitor, and the voltage is easily raised to the driving voltage required by the controllable switch device, and the circuit structure is simple, efficient, low cost and small size.

Description

Technical Field

[0001] The invention belongs to the technical field of power supply, and in particular relates to a switching power supply boost circuit. Background Art

[0002] When performing charging operations, the charger needs to detect whether the battery is connected to avoid no-load. At the same time, it is also necessary to perform emergency power-off for abnormal situations that may occur during the charging process. The most direct way to do this is to set a controllable switch device (such as MOS tube, thyristor, gallium nitride, silicon carbide, etc.) controlled by the charger chip at the electrical output end of the charger. Generally, the driving voltage required by the controllable switch device is higher than the charging output voltage, so the charger's boost circuit needs to be designed. The conventional practice is to add windings or use multi-tap windings on the secondary side of the transformer in the boost circuit, but this structure will obviously increase the volume of the circuit, and the added coil (equivalent to inductance) is not conducive to EMC / EMI testing. Summary of the invention

[0003] In view of the problems mentioned in the background technology, the present invention proposes a switching power supply boost circuit to meet the requirements of charging voltage output and driving voltage output, which is specifically achieved by the following technical means:

[0004] The switching power supply boost circuit of the present invention comprises a transformer, and a first voltage output branch and a second voltage output branch are provided on the secondary side of the transformer;

[0005] The first voltage output branch includes a first diode and a first capacitor, wherein the positive electrode of the first diode is connected to the secondary winding of the transformer, and the negative electrode thereof is connected to the output end of the first voltage output branch, one end of the first capacitor is connected to the negative electrode of the first diode, and the other end of the first capacitor is grounded;

[0006] The second voltage output branch includes a first resistor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a second diode and a third diode; one end of the second capacitor is connected to the secondary winding, and the other end thereof is connected to the third capacitor; one end of the third capacitor is connected to the cathode of the first diode via the first resistor, the common end of the second capacitor and the third capacitor is connected to the anode of the third diode via one end of the fourth capacitor, the cathode of the third diode is connected to the output end of the second voltage output branch, one end of the fifth capacitor is connected to the cathode of the third diode, and the other end of the fifth capacitor is grounded or connected to the anode of the first capacitor; the anode of the second diode is grounded or connected to the anode of the first capacitor, and its cathode is connected to the other end of the fourth capacitor.

[0007] In one or more embodiments of the present invention, one end of the fifth capacitor is connected to the cathode of the third diode, and the other end is grounded.

[0008] In one or more embodiments of the present invention, one end of the fifth capacitor is connected to the cathode of the third diode, and the other end is connected to the anode of the first capacitor.

[0009] In one or more embodiments of the present invention, there are two fifth capacitors, one of which is connected between the cathode of the third diode and the ground, and the other is connected between the cathode of the third diode and the anode of the first capacitor.

[0010] Another switching power supply boost circuit of the present invention comprises a transformer, an LLC half-bridge module is connected to the primary side of the transformer, a first voltage output branch and a second voltage output branch are provided on the secondary side of the transformer, and the secondary winding of the transformer is provided with a first tap and a second tap located at both ends, and a third tap located between the first tap and the second tap;

[0011] The first voltage output branch includes a first diode, a fourth diode and a first capacitor, the positive electrode of the first diode is connected to the first tap of the secondary winding of the transformer, and the negative electrode thereof is connected to the output end of the first voltage output branch, the high voltage end of the first capacitor is connected to the negative electrode of the first diode, and the low voltage end thereof is grounded; the positive electrode of the fourth diode is connected to the second tap of the secondary winding of the transformer, and the negative electrode thereof is connected to the high voltage end of the first capacitor; the third tap is grounded;

[0012] The second voltage output branch includes a first resistor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a second diode and a third diode; one end of the second capacitor is connected to the first tap of the secondary winding, and the other end thereof is connected to the third capacitor; one end of the third capacitor is connected to the cathode of the first diode via the first resistor, the common end of the second capacitor and the third capacitor is connected to the anode of the third diode via one end of the fourth capacitor, the cathode of the third diode is connected to the output end of the second voltage output branch, one end of the fifth capacitor is connected to the cathode of the third diode, and the other end of the first capacitor is connected to the anode of the first capacitor;

[0013] The second voltage output branch also includes a seventh capacitor, an eighth capacitor, a ninth capacitor, a third resistor, a fifth diode and a sixth diode; one end of the seventh capacitor is connected to the second tap of the secondary winding, and the other end thereof is connected to the eighth capacitor; one end of the eighth capacitor is connected to the cathode of the fourth diode via the third resistor, the common end of the seventh capacitor and the eighth capacitor is connected to the anode of the sixth diode via one end of the ninth capacitor, and the cathode of the sixth diode is connected to the output end of the second voltage output branch;

[0014] The anodes of the second diode and the fifth diode are respectively connected to the anode of the first capacitor, the cathode of the second diode is connected to the other end of the fourth capacitor, and the cathode of the fifth diode is connected to the other end of the ninth capacitor.

[0015] Another switching power supply boost circuit of the present invention comprises a transformer, an LLC half-bridge module is connected to the primary side of the transformer, a first voltage output branch and a second voltage output branch are provided on the secondary side of the transformer, and the secondary winding of the transformer is provided with a first tap and a second tap located at both ends, and a third tap located between the first tap and the second tap;

[0016] The first voltage output branch includes a first diode, a fourth diode, a first capacitor, a third resistor, a seventh capacitor and an eighth capacitor, wherein the positive electrode of the first diode is connected to the first tap of the secondary winding of the transformer, and the negative electrode thereof is connected to the output end of the first voltage output branch, the high voltage end of the first capacitor is connected to the negative electrode of the first diode, and the low voltage end thereof is grounded; the positive electrode of the fourth diode is connected to the second tap of the secondary winding of the transformer, and the negative electrode thereof is connected to the high voltage end of the first capacitor; the third tap is grounded; one end of the seventh capacitor is connected to the second tap of the secondary winding, and the other end thereof is connected to the eighth capacitor; one end of the eighth capacitor is connected to the negative electrode of the fourth diode via the third resistor;

[0017] The second voltage output branch includes a first resistor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a second diode and a third diode; one end of the second capacitor is connected to the first tap of the secondary winding, and the other end thereof is connected to the third capacitor; one end of the third capacitor is connected to the cathode of the first diode via the first resistor, the common end of the second capacitor and the third capacitor is connected to the anode of the third diode via one end of the fourth capacitor, the cathode of the third diode is connected to the output end of the second voltage output branch, one end of the fifth capacitor is connected to the cathode of the third diode, and the other end of the first capacitor is connected to the anode of the first capacitor; the anode of the second diode is connected to the cathode of the first capacitor, and the cathode of the second diode is connected to the other end of the fourth capacitor.

[0018] Another switching power supply boost circuit of the present invention comprises a transformer, an LLC half-bridge module is connected to the primary side of the transformer, a first voltage output branch and a second voltage output branch are provided on the secondary side of the transformer, and the secondary winding of the transformer is provided with a first tap and a second tap located at both ends, and a third tap located between the first tap and the second tap;

[0019] The first voltage output branch includes a first diode, a first capacitor, a first resistor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a second diode and a third diode; the cathode of the first diode is connected to the first tap of the secondary winding of the transformer, and the anode thereof is grounded; the high voltage end of the first capacitor is connected to the anode of the second diode, and the low voltage end thereof is grounded; one end of the second capacitor is connected to the first tap of the secondary winding, and the other end thereof is connected to the third capacitor; one end of the third capacitor is connected to the anode of the first diode via the first resistor, the common end of the second capacitor and the third capacitor is connected to the anode of the third diode via one end of the fourth capacitor, the second diode is connected to the other end of the fourth capacitor, and the cathode of the third diode is connected to the first voltage output end;

[0020] The second voltage output branch includes a fourth diode, a seventh capacitor, an eighth capacitor, a ninth capacitor, a third resistor, a fifth diode and a sixth diode; the cathode of the fourth diode is connected to the second tap of the secondary winding of the transformer, and the positive electrode thereof is grounded; one end of the seventh capacitor is connected to the second tap of the secondary winding, and the other end thereof is connected to the eighth capacitor; one end of the eighth capacitor is connected to the positive electrode of the fourth diode via the third resistor, the common end of the seventh capacitor and the eighth capacitor is connected to the positive electrode of the sixth diode via one end of the ninth capacitor, and the cathode of the sixth diode is connected to the first voltage output end; the cathode of the fifth diode is connected to the other end of the ninth capacitor, and the positive electrode thereof is connected to the high voltage end of the first capacitor, and the high voltage end of the first capacitor is connected to the second voltage output end; the fifth capacitor is connected between the first voltage output end and the second voltage output end.

[0021] Another switching power supply boost circuit of the present invention comprises a transformer, an LLC half-bridge module is connected to the primary side of the transformer, and the secondary winding of the transformer is provided with a first tap and a second tap located at two ends, and a third tap located between the first tap and the second tap;

[0022] A first diode, a fourth diode, a first capacitor, a first resistor, a third resistor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a seventh capacitor, an eighth capacitor, a second diode and a third diode are provided on the secondary side of the transformer; the cathode of the first diode is connected to the first tap of the secondary winding of the transformer, and the anode thereof is grounded; the cathode of the fourth diode is connected to the second tap of the secondary winding of the transformer, and the anode thereof is grounded; one end of the seventh capacitor is connected to the second tap of the secondary winding, and the other end thereof is connected to the eighth capacitor; one end of the eighth capacitor is connected to the anode of the fourth diode via the third resistor;

[0023] The high voltage end of the first capacitor is connected to the positive electrode of the second diode, and the low voltage end thereof is grounded; one end of the second capacitor is connected to the first tap of the secondary winding, and the other end thereof is connected to the third capacitor; one end of the third capacitor is connected to the positive electrode of the first diode via the first resistor, the common end of the second capacitor and the third capacitor is connected to the positive electrode of the third diode via the fourth capacitor, and the cathode of the third diode is connected to the first voltage output end; the high voltage end of the first capacitor is connected to the second voltage output end; a fifth capacitor is connected between the first voltage output end and the second voltage output end.

[0024] Compared with the prior art, the advantages of the present invention are as follows: a secondary boost branch is added on the basis of the flyback circuit (switching power supply output rectification, winding single side), and the branch uses the peak voltage at the switching moment to charge the boost capacitor, easily raising the voltage to the driving voltage required by the controllable switch device, and the circuit structure is simple, efficient, low-cost, small in size, and easy to implement. At the same time, the branch obtains the peak voltage through three capacitor split modes, has better electrical isolation than the original secondary side output circuit, is not easy to generate interference ripples, and abandons the traditional technical habit of raising the electrical bias by adding winding coils, and avoids the use of inductive devices in the branch to the greatest extent, which is conducive to passing EMC / EMI testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a circuit diagram of Example 1 of the present invention.

[0026] Figure 2 This is a circuit diagram of Embodiment 2 of the present invention.

[0027] Figure 3 4 is a circuit diagram of embodiment 3 of the present invention.

[0028] Figure 4 This is a circuit diagram of embodiment 4 of the present invention.

[0029] Figure 5 This is a circuit diagram of Example 5 of the present invention.

[0030] Figure 6 The utility model is a schematic diagram of the application principle framework in the charger circuit.

[0031] Figure 7 This is a circuit diagram of Example 6 of the present invention.

[0032] Figure 8 This is a circuit diagram of Example 7 of the present invention.

[0033] Fig. 9 This is an equivalent circuit diagram of the diode D1 of Example 4 when it is reverse cutoff.

[0034] Fig.10 1 is an equivalent circuit diagram of the diode D1 of Example 4 when it is forward-conducting. DETAILED DESCRIPTION

[0035] The present application scheme is further described as follows in conjunction with the accompanying drawings:

[0036] Example 1

[0037] See attached Figure 1 The switching power supply boost circuit includes a transformer T1A, a diode D1, a diode D2, a diode D3, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a resistor R1 and a resistor R2. The primary winding of the transformer T1A is connected to a DC source VBUS (such as: the positive electrode of the primary side input capacitor) and a drain MOS_D of the MOS tube. One end of the secondary winding of the transformer T1A is connected to the positive electrode of the diode D1, and the other end is grounded; the negative electrode of the diode D1 is connected to the positive electrode of the capacitor C1, and the negative electrode of the capacitor C1 is grounded; the diode D1 and the capacitor C1 form a first voltage output branch, and the positive electrode of the capacitor C1 outputs a charging voltage VA for subsequent battery charging. The capacitors C2, C3 and C4 are star-connected, one end of the capacitor C2 is connected to the secondary winding of the transformer T1A to obtain the induced voltage VB, one end of the capacitor C3 is connected to the cathode of the diode D1 via the resistor R1, one end of the capacitor C4 is connected to the anode of the diode D3, the anode of the diode D2 is grounded, and the other end is connected to the capacitor C4; one end of the capacitor C5 is connected to the cathode of the diode D3, and the other end is grounded; the second voltage output branch is composed of the diode D2, the diode D3, the capacitor C2, the capacitor C3, the capacitor C4, the capacitor C5, the resistor R1 and the resistor R2, one end of the capacitor C5 is connected to the output end of the second voltage output branch, and the other end is grounded, and the capacitor C5 outputs a driving voltage VC for powering subsequent switching devices.

[0038] The current flyback (switching power supply) circuit is more used for voltage reduction, and is rarely used for voltage boost. This circuit adds a secondary boost branch (i.e., the second voltage output branch) on the basis of the flyback topology. This branch uses the peak voltage (the peak component in the induced voltage VB) generated by the secondary winding of the transformer T1A at the switching moment to charge the capacitor C5 (boost capacitor), thereby easily raising the voltage to the driving voltage required by the controllable switch device. Specifically, the circuit is improved on the basis of the secondary absorption resistor R1 and the capacitor C2. The branch obtains the peak voltage through the voltage division of the capacitors C2, C3 and C4, that is, the capacitors C2 and C3 are first connected in series, and the voltage ratio of the common ends of the two is controlled by designing the capacitance values ​​of the capacitors C2 and C3. The voltage is then obtained by the capacitor C4 and charged to the capacitor C5 after passing through the diode D3. This structure connected by capacitors allows the second voltage output branch to have better electrical isolation relative to the first voltage output branch, and is not easy to generate mutually interfering voltage ripples. In addition, the capacitor C3 and the resistor R1 play a role of voltage division on the one hand, and on the other hand, they also take into account the peak clipping effect on the output voltage of the diode D1, and filter out the peak components that are not beneficial to the first voltage output branch, protect the first voltage output branch and make its output stable. In addition, the second voltage output branch abandons the traditional technical habit of raising the electrical bias by adding a winding coil, and avoids the use of inductive devices in the branch to the greatest extent, which is conducive to passing the EMC / EMI test.

[0039] The above circuit can be applied to an adjustable pulse boost circuit. The pulse can be provided by a switching power supply transformer, an MCU, a half-bridge node, etc., and different voltages can be obtained by adjusting the capacitor ratio.

[0040] Due to the unidirectional conduction of the diode D3, the charge of the capacitor C4 will be fully charged after several cycles and cannot be further charged, resulting in the circuit being unable to continue to work. Therefore, the diode D2 is added as a discharge loop of the capacitor C4 to balance the charge of the capacitor C4.

[0041] In this embodiment, the diode D1 is the first diode, the diode D2 is the second diode, the diode D3 is the third diode, the capacitor C1 is the first capacitor, the capacitor C2 is the second capacitor, the capacitor C3 is the third capacitor, the capacitor C4 is the fourth capacitor, the capacitor C5 is the fifth capacitor, and the resistor R1 is the first resistor.

[0042] Working principle of the circuit:

[0043] 1) When the primary side of transformer T1A is turned on, the secondary side is reversed and cut off.

[0044] When reaching steady state, the circuit composed of capacitors C2, C3 and C4 can be equivalent to C3 / / C4 and then connected in series with C2. From the formula for series and parallel connection of capacitors, it can be obtained that when C2:C3:C4=2:1:1, the voltages on the three capacitors are equal, which can effectively reduce the withstand voltage of the device.

[0045] For the flyback topology, V1=VBUS*NS / NP; V2=VA; VBUS primary bus voltage, NS transformer secondary turns, NP transformer primary turns, then:

[0046] (1)

[0047] 2) When the primary side of transformer T1A is turned off and the secondary side diode D2 is turned on, ignoring the voltage drops of diodes D1 and D3, we have: ; (2)

[0048] When the steady state is reached, the charge flowing through C4 is balanced, and ;(3)Get: ; (4)

[0049] IC4avg is the average forward current flowing through capacitor C4, which is equal to the supply current of VC to the charger output control module in steady state. T is the switching period, and ΔVC4 is the voltage change across capacitor C4.

[0050] The capacitance can be estimated by combining formulas (1)-(4). The final capacitance should be fine-tuned according to the actual EMC debugging situation and the actual driving current of the charger output control module to meet the actual use.

[0051] Based on the principle of embodiment 1, the present utility model also proposes embodiments 2-5 for fine-tuning the circuit structure.

[0052] Example 2

[0053] See attached Figure 2The switching power supply boost circuit includes a transformer T1A, a diode D1, a diode D2, a diode D3, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a resistor R1 and a resistor R2; the primary winding of the transformer T1A is connected to a DC source VBUS (such as: the positive electrode of the primary side input capacitor) and a drain MOS_D of the MOS tube, one end of the secondary winding of the transformer T1A is connected to the positive electrode of the diode D1, and the other end is grounded; the negative electrode of the diode D1 is connected to the positive electrode of the capacitor C1, and the negative electrode of the capacitor C1 is grounded; the diode D1 and the capacitor C1 form a first voltage output branch, and the positive electrode of the capacitor C1 outputs a charging voltage VA for subsequent battery charging. The capacitors C2, C3 and C4 are star-connected, one end of the capacitor C2 is connected to the secondary winding of the transformer T1A to obtain the induced voltage VB, one end of the capacitor C3 is connected to the cathode of the diode D1 via the resistor R1, one end of the capacitor C4 is connected to the anode of the diode D3, the diode D2 is used to balance the charge of the capacitor C4, the anode of the diode D2 is connected to the anode of the capacitor C1, and the cathode of the diode D2 is connected to the capacitor C4; one end of the capacitor C5 is connected to the cathode of the diode D3, and the other end is grounded; the second voltage output branch is formed by the diode D2, the diode D3, the capacitor C2, the capacitor C3, the capacitor C4, the capacitor C5, the resistor R1 and the resistor R2, one end of the capacitor C5 is connected to the output end of the second voltage output branch, and the other end is grounded, and the capacitor C5 outputs a driving voltage VC for powering subsequent switching devices.

[0054] In this embodiment, the diode D1 is the first diode, the diode D2 is the second diode, the diode D3 is the third diode, the capacitor C1 is the first capacitor, the capacitor C2 is the second capacitor, the capacitor C3 is the third capacitor, the capacitor C4 is the fourth capacitor, the capacitor C5 is the fifth capacitor, and the resistor R1 is the first resistor.

[0055] Example 3

[0056] See attached Figure 3The switching power supply boost circuit includes a transformer T1A, a diode D1, a diode D2, a diode D3, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C6, a resistor R1 and a resistor R2; the primary winding of the transformer T1A is connected to a DC source VBUS (such as: the positive electrode of the primary side input capacitor) and a drain MOS_D of the MOS tube, one end of the secondary winding of the transformer T1A is connected to the positive electrode of the diode D1, and the other end is grounded; the negative electrode of the diode D1 is connected to the positive electrode of the capacitor C1, and the negative electrode of the capacitor C1 is grounded; the diode D1 and the capacitor C1 form a first voltage output branch, and the positive electrode of the capacitor C1 outputs a charging voltage VA for subsequent battery charging. The capacitors C2, C3 and C4 are star-connected, one end of the capacitor C2 is connected to the secondary winding of the transformer T1A to obtain the induced voltage VB, one end of the capacitor C3 is connected to the cathode of the diode D1 via the resistor R1, one end of the capacitor C4 is connected to the anode of the diode D3, the anode of the diode D2 is grounded, and the other end is connected to the capacitor C4, which plays a role in balancing the charge of the capacitor C4; one end of the capacitor C5 is connected to the cathode of the diode D3, and the other end is grounded; the second voltage output branch is composed of the diode D2, the diode D3, the capacitor C2, the capacitor C3, the capacitor C4, the capacitor C6, the resistor R1 and the resistor R2, the capacitor C6 outputs the driving voltage VC for powering the subsequent switching device, and the two ends of the capacitor C6 are respectively connected between the output ends of the first voltage output branch and the second voltage output branch, and the capacitor C6 stabilizes the voltage difference between the voltages VA and VC.

[0057] In this embodiment, the diode D1 is the first diode, the diode D2 is the second diode, the diode D3 is the third diode, the capacitor C1 is the first capacitor, the capacitor C2 is the second capacitor, the capacitor C3 is the third capacitor, the capacitor C4 is the fourth capacitor, the capacitor C5 is the fifth capacitor, and the resistor R1 is the first resistor.

[0058] Example 4

[0059] See attached Figure 4The switching power supply boost circuit includes a transformer T1A, a diode D1, a diode D2, a diode D3, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C6, a resistor R1 and a resistor R2; the primary winding of the transformer T1A is connected to a DC source VBUS (such as: the positive electrode of the primary side input capacitor) and a drain MOS_D of the MOS tube, one end of the secondary winding of the transformer T1A is connected to the positive electrode of the diode D1, and the other end is grounded; the negative electrode of the diode D1 is connected to the positive electrode of the capacitor C1, and the negative electrode of the capacitor C1 is grounded; the diode D1 and the capacitor C1 form a first voltage output branch, and the positive electrode of the capacitor C1 outputs a charging voltage VA for subsequent battery charging. The capacitors C2, C3 and C4 are star-connected, one end of the capacitor C2 is connected to the secondary winding of the transformer T1A to obtain the induced voltage VB, one end of the capacitor C3 is connected to the cathode of the diode D1 via the resistor R1, one end of the capacitor C4 is connected to the anode of the diode D3, the diode D2 is used to balance the charge of the capacitor C4, the anode of the diode D2 is connected to the anode of the capacitor C1, and the cathode of the diode D2 is connected to the capacitor C4; one end of the capacitor C5 is connected to the cathode of the diode D3, and the other end is grounded; the second voltage output branch is composed of the diode D2, the diode D3, the capacitor C2, the capacitor C3, the capacitor C4, the capacitor C6, the resistor R1 and the resistor R2, the capacitor C6 outputs the driving voltage VC for powering the subsequent switching device, and the two ends of the capacitor C6 are respectively connected between the output ends of the first voltage output branch and the second voltage output branch, and the capacitor C6 stabilizes the voltage difference between the voltages VA and VC.

[0060] In this embodiment, the diode D1 is the first diode, the diode D2 is the second diode, the diode D3 is the third diode, the capacitor C1 is the first capacitor, the capacitor C2 is the second capacitor, the capacitor C3 is the third capacitor, the capacitor C4 is the fourth capacitor, the capacitor C6 is the fifth capacitor, and the resistor R1 is the first resistor.

[0061] This embodiment can not only effectively reduce the voltage borne by the capacitors through the voltage-dividing effect of capacitors C2, C3 and C4, but also obtain different voltage ratios by adjusting the capacities of capacitors C2, C3 and C4, so as to better obtain the required VC voltage.

[0062] 1) When the diode D1 is reverse cutoff, the equivalent circuit is as follows Fig. 9 As shown, in order to simplify the calculation, VA is used as the reference point. At this time, C3 / / C4 is connected in series with C2, then

[0063] (1)

[0064] The voltage across capacitor C4 is: (2)

[0065] 2) When the diode D1 is forward conducting, the equivalent circuit is as follows Fig.10 As shown, at this time: C2 / / C3 is connected in series with C4, then

[0066] (3)

[0067] When reaching steady state, within one switching cycle,

[0068] (4)

[0069] Charge balance, we have:

[0070] (5)

[0071] Among them, I is the minimum current required by the charger output control module in steady state, T is the primary side working cycle, and U is the calculation result of formula 4. It can be obtained from formula 4 that the voltage change across capacitor C4 is not only related to the capacity of capacitors C2, C3 and C4, but also to the refracted voltage of transformer T1A and the expected boost voltage. The capacity of capacitor C4 is also affected by the load of the actual circuit.

[0072] The above deduces the relationship between the capacity of capacitors C2, C3 and C4 and the result. Finally, the values ​​of capacitors C2, C3 and C4 need to be fine-tuned according to comprehensive factors such as the actual circuit, EMC, and temperature rise.

[0073] Example 5

[0074] See attached Figure 5The switching power supply boost circuit includes a transformer T1A, a diode D1, a diode D2, a diode D3, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C6, a resistor R1 and a resistor R2; the primary winding of the transformer T1A is connected to a DC source VBUS (such as: the positive electrode of the primary side input capacitor) and a drain MOS_D of the MOS tube, one end of the secondary winding of the transformer T1A is connected to the positive electrode of the diode D1, and the other end is grounded; the negative electrode of the diode D1 is connected to the positive electrode of the capacitor C1, and the negative electrode of the capacitor C1 is grounded; the diode D1 and the capacitor C1 form a first voltage output branch, and the positive electrode of the capacitor C1 outputs a charging voltage VA for subsequent battery charging. Capacitor C2, capacitor C3 and capacitor C4 are star-connected, one end of capacitor C2 is connected to the secondary winding of transformer T1A, one end of capacitor C3 is connected to the cathode of diode D1 via resistor R1, one end of capacitor C4 is connected to the anode of diode D3, the diode D2 is used to balance the charge of capacitor C4, the anode of diode D2 is connected to the anode of capacitor C1, and the cathode of diode D2 is connected to capacitor C4; one end of capacitor C5 is connected to the cathode of diode D3, and the other end is grounded; a second voltage output branch is formed by diode D2, diode D3, capacitor C2, capacitor C3, capacitor C4, capacitor C5, capacitor C6, resistor R1 and resistor R2, and capacitor C5 and capacitor C6 jointly output a driving voltage VC for powering subsequent switching devices, one end of capacitor C5 is connected to the output end of the second voltage output branch, and the other end is grounded, and the two ends of capacitor C6 are respectively connected between the output ends of the first voltage output branch and the second voltage output branch, and this dual capacitor structure plays an active role in stabilizing voltages VA and VC.

[0075] In this embodiment, the diode D1 is the first diode, the diode D2 is the second diode, the diode D3 is the third diode, the capacitor C1 is the first capacitor, the capacitor C2 is the second capacitor, the capacitor C3 is the third capacitor, the capacitor C4 is the fourth capacitor, the capacitor C5 and the capacitor C6 are equivalent to the fifth capacitor, and the resistor R1 is the first resistor.

[0076] In the charger products used in this patent, the output control module of the charger is generally composed of two NMOS tubes back to back, and its function is defined as: when the NMOS tube does not receive a valid control signal, it blocks the current at the VA terminal from flowing to the battery and the battery current from flowing to VA. When the charger's MCU detects that the battery is connected and there is no abnormality, it needs to control the output control module to conduct to form a current loop from the VC terminal-output control module-VA terminal-capacitor C5-VC terminal, that is, the attached Figure 6 The operating current is shown in the current I.

[0077] In the above-mentioned embodiments 4 and 5, the discharge loop is composed of the resistor R1, the capacitor C2, the capacitor C3, the capacitor C4 and the capacitor C5 (the capacitor C6). Since the driving current required by the NMOS tube when working is very small (uA level), a 20K-100K resistor is generally placed between GS to ensure that the MOS tube remains in a closed state when there is no driving. Taking a 10V driving voltage as an example, the current I needs to be guaranteed to be at least 0.5mA.

[0078] 1) Selection of capacitor C3 and resistor R1

[0079] Taking the flyback topology circuit as an example, capacitor C3 and resistor R1 are placed at both ends of diode D1 to reduce the spikes at both ends of diode D1. The specific values ​​of capacitor C3 and resistor R1 are balanced according to the actual winding of transformer T1A, the selection of the withstand voltage of diode D1, and the loss and temperature rise.

[0080] 2) Selection of capacitor C2

[0081] The main function of capacitor C2 is to reduce the withstand voltage of capacitors C4 and C3, that is, the star topology formed by capacitors C2, C3 and 4 can make the circuit suitable for using capacitors with low withstand voltage, thereby compatibility between circuit cost and performance.

[0082] 3) Selection of capacitor C4

[0083] Since the average charging current of capacitor C4 should be ≥ I to ensure the driving voltage, it is found in the experiment that when the capacitance of capacitor C4 is equal to the capacitance of capacitor C3, it can ensure that the VC terminal voltage is at least 8V greater than the VA terminal voltage. Therefore, increasing the capacitance of C4 can obtain a higher VC voltage.

[0084] Since the flyback circuit adjusts the output voltage by adjusting the duty cycle, the average forward current flowing through capacitor C4 will be different under different output loads, different switching frequencies and different diode D1 models. Therefore, the value of capacitor C4 and the voltage difference between the VC terminal and the VA terminal are determined by the actual circuit debugging.

[0085] Example 6

[0086] See attached Figure 7 The switching power supply boost circuit includes a transformer T1A, a diode D1, a diode D2, a diode D3, a diode D4, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C7, a capacitor C8, a resistor R1, a resistor R2 and a resistor R3. The LLC half-bridge module is connected to the primary side of the transformer T1A. The secondary winding of the transformer T1A is provided with a first tap 5 and a second tap 7 at both ends, and a third tap 6 located between the first tap 5 and the second tap 7;

[0087] The positive electrode of the diode D1 is connected to the first tap 5 of the secondary winding of the transformer T1A, and the negative electrode thereof is connected to the output terminal VA. The high voltage end of the capacitor C1 is connected to the negative electrode of the diode D1, and the low voltage end thereof is grounded; the positive electrode of the diode D4 is connected to the second tap 7 of the secondary winding of the transformer T1A, and the negative electrode thereof is connected to the high voltage end of the capacitor C1; the third tap 6 is grounded; one end of the capacitor C1 is connected to the first tap 5 of the secondary winding, and the other end thereof is connected to the capacitor C3; one end of the capacitor C3 is connected to the negative electrode of the diode D1 via the resistor R1, the common end of the capacitor C2 and the capacitor C3 is connected to the positive electrode of the diode D3 via the capacitor C4, the negative electrode of the diode D3 is connected to the output terminal VC, and the capacitor 5 is connected between the output terminal VA and the output terminal VC; one end of the capacitor C7 is connected to the second tap 7 of the secondary winding, and the other end thereof is connected to the capacitor C8; one end of the capacitor C8 is connected to the negative electrode of the diode D4 via the resistor R3;

[0088] As a redundant design, it also includes capacitor C9, diode D5 and diode D6; the common end of the capacitor C7 and the capacitor C8 is connected to the positive electrode of the diode D6 via the capacitor C9, and the negative electrode of the diode D6 is connected to the output terminal VC; the positive electrodes of the diode D2 and the diode D5 are respectively connected to the positive electrode of the capacitor C1, the negative electrode of the diode D2 is connected to the capacitor C4, and the negative electrode of the diode D5 is connected to the capacitor C9.

[0089] In this embodiment, the diode D1 is the first diode, the diode D2 is the second diode, the diode D3 is the third diode, the diode D4 is the fourth diode, the diode D5 is the fifth diode, the diode D6 is the sixth diode, the capacitor C1 is the first capacitor, the capacitor C2 is the second capacitor, the capacitor C3 is the third capacitor, the capacitor C4 is the fourth capacitor, the capacitor C5 is the fifth capacitor, the capacitor C7 is the seventh capacitor, the capacitor C8 is the eighth capacitor, the capacitor C9 is the ninth capacitor, the resistor R1 is the first resistor, and the resistor R3 is the third resistor.

[0090] Example 7

[0091] See attached Figure 8The switching power supply boost circuit includes a transformer T1A, a diode D1, a diode D2, a diode D3, a diode D4, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C7, a capacitor C8, a resistor R1, a resistor R2 and a resistor R3. The LLC half-bridge module is connected to the primary side of the transformer T1A. The secondary winding of the transformer T1A is provided with a first tap 5 and a second tap 7 at both ends, and a third tap 6 located between the first tap 5 and the second tap 7; the cathode of the diode D1 is connected to the first tap 5 of the secondary winding of the transformer T1A, and the anode thereof is grounded; the cathode of the diode D4 is connected to the second tap 7 of the secondary winding of the transformer T1A, and the anode thereof is grounded; the cathode of the capacitor C7 is connected to the second tap 7 of the secondary winding of the transformer T1A, and the anode thereof is grounded; The first end of the secondary winding is connected to the second tap 7 of the secondary winding, and the other end is connected to the capacitor C8; one end of the capacitor C8 is connected to the positive electrode of the diode D4 via the resistor R3; the high voltage end of the capacitor C1 is connected to the positive electrode of the diode D2, and the low voltage end is grounded; one end of the capacitor C2 is connected to the first tap 5 of the secondary winding, and the other end is connected to the capacitor C3; one end of the capacitor C3 is connected to the positive electrode of the diode D1 via the resistor R1, the common end of the capacitor C2 and the capacitor C3 is connected to the positive electrode of the diode D3 via the capacitor C4, and the cathode of the diode D3 is connected to the voltage output terminal VC; the high voltage end of the capacitor C1 is connected to the voltage output terminal VA; a capacitor C5 is connected between the voltage output terminal VA and the voltage output terminal VC, and the third tap of the secondary winding is connected to the voltage output terminal VA.

[0092] As a redundant design, it also includes capacitor C9, diode D5 and diode D6; the common end of the capacitor C7 and the capacitor C8 is connected to the positive electrode of the diode D6 via the capacitor C9, and the negative electrode of the diode D6 is connected to the output terminal VC; the positive electrodes of the diode D2 and the diode D5 are respectively connected to the positive electrode of the capacitor C1, the negative electrode of the diode D2 is connected to the capacitor C4, and the negative electrode of the diode D5 is connected to the capacitor C9.

[0093] In this embodiment, the diode D1 is the first diode, the diode D2 is the second diode, the diode D3 is the third diode, the diode D4 is the fourth diode, the diode D5 is the fifth diode, the diode D6 is the sixth diode, the capacitor C1 is the first capacitor, the capacitor C2 is the second capacitor, the capacitor C3 is the third capacitor, the capacitor C4 is the fourth capacitor, the capacitor C5 is the fifth capacitor, the capacitor C7 is the seventh capacitor, the capacitor C8 is the eighth capacitor, the capacitor C9 is the ninth capacitor, the resistor R1 is the first resistor, and the resistor R3 is the third resistor.

[0094] The above-mentioned Embodiment 6 and Embodiment 7 are respectively extended applications of the circuit of the present patent, in which an LLC circuit (LLC_HB, i.e., LLC half-bridge node) is added on the primary side of the transformer T1A. The difference between Embodiment 6 and Embodiment 7 lies in the different rectification directions. Embodiment 6 is high-side rectification (connected to the positive pole), and Embodiment 7 is low-side rectification (connected to the negative pole or ground). Among them, the P part refers to a redundant design, the function of which is to enhance the stability of the voltage output, and the addition / deletion is selected according to the actual situation.

[0095] In the above embodiments, the diode D2 may be a diode or a voltage regulator diode. When a voltage regulator diode is used, the VC voltage can be clamped to prevent the VC voltage from being too high when the driving current is small and thus damaging the MOS tube.

[0096] The above-mentioned preferred implementation modes should be regarded as illustrative examples of the implementation modes of the present application scheme. Any technical deductions, replacements, improvements, etc. that are identical or similar to the present application scheme or made based on this scheme should be regarded as within the scope of protection of this patent.

Claims

1. A switching power supply boost circuit, comprising a transformer, characterized in that: A first voltage output branch and a second voltage output branch are provided on the secondary side of the transformer; The first voltage output branch includes a first diode and a first capacitor, wherein the positive electrode of the first diode is connected to the secondary winding of the transformer, and the negative electrode thereof is connected to the output end of the first voltage output branch, one end of the first capacitor is connected to the negative electrode of the first diode, and the other end of the first capacitor is grounded; The second voltage output branch includes a first resistor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a second diode and a third diode; one end of the second capacitor is connected to the secondary winding, and the other end thereof is connected to the third capacitor; one end of the third capacitor is connected to the cathode of the first diode via the first resistor, the common end of the second capacitor and the third capacitor is connected to the anode of the third diode via one end of the fourth capacitor, the cathode of the third diode is connected to the output end of the second voltage output branch, one end of the fifth capacitor is connected to the cathode of the third diode, and the other end of the fifth capacitor is grounded or connected to the anode of the first capacitor; The anode of the second diode is grounded or connected to the anode of the first capacitor, and the cathode of the second diode is connected to the other end of the fourth capacitor.

2. The switching power supply boost circuit according to claim 1, characterized in that: One end of the fifth capacitor is connected to the cathode of the third diode, and the other end is grounded.

3. The switching power supply boost circuit according to claim 1, characterized in that: One end of the fifth capacitor is connected to the cathode of the third diode, and the other end is connected to the anode of the first capacitor.

4. The switching power supply boost circuit according to claim 1, characterized in that: There are two fifth capacitors, one of which is connected between the cathode of the third diode and the ground, and the other is connected between the cathode of the third diode and the anode of the first capacitor.

5. A switching power supply boost circuit, comprising a transformer, characterized in that: An LLC half-bridge module is connected to the primary side of the transformer, a first voltage output branch and a second voltage output branch are provided on the secondary side of the transformer, and the secondary winding of the transformer is provided with a first tap and a second tap located at both ends, and a third tap located between the first tap and the second tap; The first voltage output branch includes a first diode, a fourth diode and a first capacitor, the positive electrode of the first diode is connected to the first tap of the secondary winding of the transformer, and the negative electrode thereof is connected to the output end of the first voltage output branch, the high voltage end of the first capacitor is connected to the negative electrode of the first diode, and the low voltage end thereof is grounded; the positive electrode of the fourth diode is connected to the second tap of the secondary winding of the transformer, and the negative electrode thereof is connected to the high voltage end of the first capacitor; the third tap is grounded; The second voltage output branch includes a first resistor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a second diode and a third diode; one end of the second capacitor is connected to the first tap of the secondary winding, and the other end thereof is connected to the third capacitor; one end of the third capacitor is connected to the cathode of the first diode via the first resistor, the common end of the second capacitor and the third capacitor is connected to the anode of the third diode via one end of the fourth capacitor, the cathode of the third diode is connected to the output end of the second voltage output branch, one end of the fifth capacitor is connected to the cathode of the third diode, and the other end of the first capacitor is connected to the anode of the first capacitor; The second voltage output branch also includes a seventh capacitor, an eighth capacitor, a ninth capacitor, a third resistor, a fifth diode and a sixth diode; one end of the seventh capacitor is connected to the second tap of the secondary winding, and the other end thereof is connected to the eighth capacitor; one end of the eighth capacitor is connected to the cathode of the fourth diode via the third resistor, the common end of the seventh capacitor and the eighth capacitor is connected to the anode of the sixth diode via one end of the ninth capacitor, and the cathode of the sixth diode is connected to the output end of the second voltage output branch; The anodes of the second diode and the fifth diode are respectively connected to the anode of the first capacitor, the cathode of the second diode is connected to the other end of the fourth capacitor, and the cathode of the fifth diode is connected to the other end of the ninth capacitor.

6. A switching power supply boost circuit, comprising a transformer, characterized in that: An LLC half-bridge module is connected to the primary side of the transformer, a first voltage output branch and a second voltage output branch are provided on the secondary side of the transformer, and the secondary winding of the transformer is provided with a first tap and a second tap located at both ends, and a third tap located between the first tap and the second tap; The first voltage output branch includes a first diode, a fourth diode, a first capacitor, a third resistor, a seventh capacitor and an eighth capacitor, wherein the positive electrode of the first diode is connected to the first tap of the secondary winding of the transformer, and the negative electrode thereof is connected to the output end of the first voltage output branch, the high voltage end of the first capacitor is connected to the negative electrode of the first diode, and the low voltage end thereof is grounded; the positive electrode of the fourth diode is connected to the second tap of the secondary winding of the transformer, and the negative electrode thereof is connected to the high voltage end of the first capacitor; the third tap is grounded; one end of the seventh capacitor is connected to the second tap of the secondary winding, and the other end thereof is connected to the eighth capacitor; one end of the eighth capacitor is connected to the negative electrode of the fourth diode via the third resistor; The second voltage output branch includes a first resistor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a second diode and a third diode; one end of the second capacitor is connected to the first tap of the secondary winding, and the other end thereof is connected to the third capacitor; one end of the third capacitor is connected to the cathode of the first diode via the first resistor, the common end of the second capacitor and the third capacitor is connected to the anode of the third diode via one end of the fourth capacitor, the cathode of the third diode is connected to the output end of the second voltage output branch, one end of the fifth capacitor is connected to the cathode of the third diode, and the other end of the first capacitor is connected to the anode of the first capacitor; the anode of the second diode is connected to the cathode of the first capacitor, and the cathode of the second diode is connected to the other end of the fourth capacitor.

7. A switching power supply boost circuit, comprising a transformer, characterized in that: An LLC half-bridge module is connected to the primary side of the transformer, a first voltage output branch and a second voltage output branch are provided on the secondary side of the transformer, and the secondary winding of the transformer is provided with a first tap and a second tap located at both ends, and a third tap located between the first tap and the second tap; The first voltage output branch includes a first diode, a first capacitor, a first resistor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a second diode and a third diode; the cathode of the first diode is connected to the first tap of the secondary winding of the transformer, and the anode thereof is grounded; the high voltage end of the first capacitor is connected to the anode of the second diode, and the low voltage end thereof is grounded; one end of the second capacitor is connected to the first tap of the secondary winding, and the other end thereof is connected to the third capacitor; one end of the third capacitor is connected to the anode of the first diode via the first resistor, the common end of the second capacitor and the third capacitor is connected to the anode of the third diode via one end of the fourth capacitor, the cathode of the second diode is connected to the other end of the fourth capacitor, and the cathode of the third diode is connected to the first voltage output end; The second voltage output branch includes a fourth diode, a seventh capacitor, an eighth capacitor, a ninth capacitor, a third resistor, a fifth diode and a sixth diode; the cathode of the fourth diode is connected to the second tap of the secondary winding of the transformer, and the positive electrode thereof is grounded; one end of the seventh capacitor is connected to the second tap of the secondary winding, and the other end thereof is connected to the eighth capacitor; one end of the eighth capacitor is connected to the positive electrode of the fourth diode via the third resistor, the common end of the seventh capacitor and the eighth capacitor is connected to the positive electrode of the sixth diode via one end of the ninth capacitor, and the cathode of the sixth diode is connected to the first voltage output end; the cathode of the fifth diode is connected to the other end of the ninth capacitor, and the positive electrode thereof is connected to the high voltage end of the first capacitor, and the high voltage end of the first capacitor is connected to the second voltage output end; the fifth capacitor is connected between the first voltage output end and the second voltage output end.

8. The switching power supply boost circuit according to claim 7, comprising a transformer, characterized in that: The third tap of the secondary winding is connected to the second voltage output terminal.

9. A switching power supply boost circuit, comprising a transformer, characterized in that: An LLC half-bridge module is connected to the primary side of the transformer, wherein the secondary winding of the transformer is provided with a first tap, a second tap, and a third tap located between the first tap and the second tap; A first diode, a fourth diode, a first capacitor, a first resistor, a third resistor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a seventh capacitor, an eighth capacitor, a second diode and a third diode are provided on the secondary side of the transformer; the cathode of the first diode is connected to the first tap of the secondary winding of the transformer, and the anode thereof is grounded; the cathode of the fourth diode is connected to the second tap of the secondary winding of the transformer, and the anode thereof is grounded; one end of the seventh capacitor is connected to the second tap of the secondary winding, and the other end thereof is connected to the eighth capacitor; one end of the eighth capacitor is connected to the anode of the fourth diode via the third resistor; The high voltage end of the first capacitor is connected to the positive electrode of the second diode, and the low voltage end thereof is grounded; one end of the second capacitor is connected to the first tap of the secondary winding, and the other end thereof is connected to the third capacitor; one end of the third capacitor is connected to the positive electrode of the first diode via the first resistor, the common end of the second capacitor and the third capacitor is connected to the positive electrode of the third diode via the fourth capacitor, and the cathode of the third diode is connected to the first voltage output end; the high voltage end of the first capacitor is connected to the second voltage output end; a fifth capacitor is connected between the first voltage output end and the second voltage output end.

Images