An auxiliary source circuit

Abstract

The application discloses an auxiliary source circuit, which comprises an auxiliary winding, a starting and standby power supply circuit, a voltage reduction and stabilization circuit and a steady-state power supply circuit. After the starting of the main power circuit is completed, the starting and standby power supply circuit can automatically switch the power supply branch, thereby reducing the loss; the steady-state power supply circuit can realize soft switching and can operate at high frequency, which is beneficial to improving the efficiency and power density of the power supply device; when the steady-state power supply circuit fails, the starting and standby power supply circuit can continue to provide the auxiliary source power supply, thereby improving the fault tolerance of the auxiliary source circuit; the power switch tube and the control switch tube in the auxiliary source circuit can adopt MOS, which is easy to integrate and improve the power density.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of power electronic conversion technology, and particularly relates to an auxiliary source circuit. BACKGROUND

[0002] In order to meet the increasing demand of energy-saving and miniaturization of electrical equipment, high efficiency and high power density have become an important direction of switching power supply research. Figure 1 The four-switch buck-boost converter shown has the ability of buck-boost power conversion, and can realize high efficiency in a wide voltage range. Meanwhile, the converter circuit structure is simple, and all the switching tubes can realize soft switching, so that the converter can operate at high switching frequency to improve the power density of the converter. As the main power circuit of the power supply device, the four-switch buck-boost converter has been widely applied to various power conversion occasions requiring high efficiency and high power density. In the figure, S1-S4 are switching tubes, L f is an energy transfer inductance, C o is an output filter capacitor, V in and V o are input and output voltages of the converter, i Lf is a current flowing through the energy transfer inductance L f , v A is a midpoint voltage of the switching bridge arm composed of switching tubes S1 and S2, v B is a midpoint voltage of the switching bridge arm composed of switching tubes S3 and S4, t0-t4 are times, v GS1 -v GS4 are driving control signals of switching tubes S1-S4, T s is a switching period, and I N is a negative current.

[0003] The auxiliary source circuit is another core circuit outside the main power circuit of the power supply device. It works before the main power circuit and provides stable and reliable power supply for electrical devices in the main power circuit, such as controllers, drivers, operational amplifiers, logic gate circuits, etc., to ensure the reliable work of the main power circuit and continuous power supply for the load equipment. While the main power circuit of the power supply device realizes high efficiency and high power density, the auxiliary source circuit also needs to have the advantages of high efficiency and small size to further improve the efficiency and power density of the system.

[0004] The traditional way of taking power from the transformer input by LDO is simple in circuit implementation, but in wide input voltage applications, there is a problem of significant increase in loss at high input voltage, which reduces the overall efficiency of the power supply device, and additional measures are needed for heat dissipation, which is also not conducive to the improvement of power density. When the switching auxiliary source circuit, such as Buck converter, flyback converter, is applied at high frequency (increase frequency to reduce volume and improve power density), it also faces the problem of increased loss caused by hard switching. On the other hand, these auxiliary source circuit schemes do not have fault tolerance capability, and once a fault occurs, the main power circuit will lose power and cannot realize power conversion function, and the load power device will be powered off. SUMMARY

[0005] The purpose of the present application is to solve the problems existing in the prior art, and provide an auxiliary source circuit.

[0006] The technical solution for achieving the purpose of the present application is: an auxiliary source circuit, the circuit comprising an auxiliary winding, a start-up and backup power supply circuit, a voltage reduction and stabilization circuit, and a steady-state power supply circuit; the auxiliary winding is coupled with an energy transmission inductor L f of a main power circuit of a power supply device, i.e., a four-switch buck-boost converter C11 ; the start-up and backup power supply circuit outputs a first auxiliary power V in according to the input voltage V C11 of the main power circuit of the power supply device and the voltage V CC , and then converts it into a second auxiliary power V DD1 through a voltage reduction and stabilization circuit, V DD1 <V CC , the voltage reduction and stabilization circuit controls V DD1 to be stable at a set value V DD_ref ; the second auxiliary power V DD1 is outputted after a second diode D 12 , and a third auxiliary power V DD is outputted, and the steady-state power supply circuit takes power from the midpoint of the switch bridge arm composed of the switch tubes S3 and S4 of the four-switch buck-boost converter, i.e., v B , and outputs V DD , and the third auxiliary power V DD is the main auxiliary source, which supplies power to the power devices of the main power circuit.

[0007] Further, the start-up and backup power supply circuit comprises a power circuit and a control circuit, wherein the power circuit comprises a first switch tube Q 21 ~ a second switch tube Q 22 , a first resistor R 21 , and a third diode D 21 , and the control circuit comprises a sampling coefficient control circuit, a third switch tube Q23 Second resistor R 22 ~Fourth resistor R 24 Operational amplifier OP1, first impedance network Z 21 ~Second impedance network Z 22 and the fourth capacitor C 21 ;

[0008] The input voltage V in Connect the first switching transistor Q 21 The drain of the capacitor is simultaneously connected to the first resistor R. 21 Connect the first switching transistor Q 21 The gate of the second switch Q 22 The gate of the op-amp and the output of op-amp OP1 are connected through the fourth capacitor C. 21 Grounding, first switch Q 21 The source of the third diode D is connected. 21 The positive terminal; the output voltage V C11 Connect the second switching transistor Q 22 The drain of the sampling coefficient control circuit; the control signal v output by the sampling coefficient control circuit. gsQ23 Connect the third switch Q 23 The gate of the third switch Q 23 A fourth resistor R is connected in parallel between the source and drain. 24 Meanwhile, the third switch Q 23 The source is grounded, and the third switch Q is... 23 The drain is connected in series with the third resistor R. 23 Second resistor R 22 The third resistor R 23 Second resistor R 22 The common terminal is connected through the first impedance network Z. 21 Connect the negative input terminal of operational amplifier OP1, which is also connected to the second impedance network Z. 22 Connect the output terminal of op-amp OP1, and input the first voltage reference value V to the positive input terminal of op-amp OP1. ref1 The third diode D 21 The negative terminal, the second switching transistor Q 22 The source and the second resistor R 22 The other end is connected to the second output capacitor C. 12 Grounded, and simultaneously outputs the first auxiliary power supply V. CC Op-amp OP1 and first impedance network Z 21 ~Second impedance network Z 22 Composition V CC The voltage loop will set the first voltage reference V. ref1 With the second resistor R 22 and the third resistor R 23 Sampling feedback voltage V at the connection pointFB1 the error is amplified and an output control signal v CC_ctrl .

[0009] Alternatively, the control circuit comprises a sampling coefficient control circuit, a third switch tube Q 23 , a second resistor R 22 ~ a fourth resistor R 24 , a third impedance network Z 23 , a TL431 device U 21 and a fourth capacitor C 21 ; the control signal v gsQ23 output by the sampling coefficient control circuit is connected to the gate of the third switch tube Q 23 , the drain and source of the third switch tube Q 23 are connected in parallel with the fourth resistor R 24 , one end of the fourth resistor R 24 is grounded and connected to the anode A of the TL431 device U 21 , the other end outputs a first auxiliary power supply V 23 through the series connection of a third resistor R 22 and a second resistor R CC , the common end of the third resistor R 23 and the second resistor R 22 is connected to the ground through a third impedance network Z 23 and a fourth capacitor C 21 , and connected to the reference electrode R of the TL431 device U 21 , the common end of the third impedance network Z 23 and the fourth capacitor C 21 is connected to the cathode K of the TL431 device U 21 and the control signal v CC_ctrl ; V CC is divided by the second resistor R 22 ~ the fourth resistor R 24 to obtain a sampling feedback voltage V FB1 , the TL431 device U 21 amplifies the error between V FB1 and its internal voltage reference and outputs, and the size of v CC_ctrl is adjusted to achieve the voltage stabilization control of V CC .

[0010] Further, the steady-state power supply circuit comprises a power circuit and a control circuit, wherein the power circuit comprises an inductor L 31 , fourth diode D 31 ~ sixth diode D 33 and fourth switch tube Q 31 , and the control circuit comprises a fifth resistor R 31 ~ a sixth resistor R 32, the fourth impedance network Z 31 , the fifth impedance network Z 32 , the comparator CP1, the NOT gate N1, the AND gate AND1, the one-shot trigger circuit 1, the RS trigger RS1 and the fifth capacitor C 31 ; one end of the inductor L 31 is connected to the midpoint of the switch bridge arm composed of the switch tubes S3 and S4, i.e. v B , and the other end is connected to the output voltage V 31 of the four-switch buck-boost converter through the fourth diode D o , and simultaneously connected to the drain of the fourth switch tube Q 32 through the fifth diode D 31 , and the source of the fourth switch tube Q 31 is connected to the ground through the third capacitor C 13 , and also connected to the Q terminal of the RS trigger RS1 through the sixth diode D 33 , the fifth capacitor C 31 , and simultaneously connected to the positive input terminal of the operational amplifier OP2 through the fifth resistor R 31 , and the positive input terminal of the operational amplifier OP2 is also connected to the ground through the sixth resistor R 32 ; the anode of the second diode D 12 is connected to the second auxiliary power supply V DD1 , and the cathode is connected to the third auxiliary power supply V DD and the source of the fourth switch tube Q 31 and the common terminal of the fifth resistor R 31 ; the gate of the fourth switch tube Q 31 is connected to the common terminal of the sixth diode D 33 , the fifth capacitor C 31 , and also connected to the cathode of the sixth diode D 33 ; the negative input terminal of the operational amplifier OP2 is connected to the second voltage reference value V 31 through the fourth impedance network Z ref2 , and simultaneously connected to the output terminal of the operational amplifier OP2 and the negative input terminal of the comparator CP1 through the fifth impedance network Z 32 ; the positive input terminal of the comparator CP1 is connected to the triangular wave voltage signal of the main power circuit period timing, and the output terminal is connected to the AND gate AND1; the switch tube S4 drive control signal v GS4 is connected to the AND gate AND1 after passing through the NOT gate N1, and the output signal of the AND gate AND1 is connected to the S terminal of the RS trigger RS1 after passing through the one-shot trigger circuit 1, and the R terminal of the RS trigger RS1 inputs the off control signal of the switch tube S4 in the main power circuit.

[0011] Compared with the prior art, the present application has the following advantages:

[0012] (1) After the main power circuit is started, the startup and backup power supply circuit can automatically switch power supply branches to reduce losses.

[0013] (2) The steady-state power supply circuit can achieve soft switching and can operate at high frequency, which is beneficial to improving the efficiency and power density of the power supply device.

[0014] (3) When the steady-state power supply circuit fails, the startup and backup power supply circuits can continue to provide auxiliary power supply, which improves the fault tolerance of the auxiliary power supply circuit.

[0015] (4) Both the power switching transistor and the control switching transistor in the auxiliary source circuit can be MOSFETs, which are easy to integrate and improve power density.

[0016] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0017] Figure 1 The circuit topology diagram of a four-switch buck-boost converter is shown, where (a) is the circuit topology and (b) is a typical operating waveform diagram.

[0018] Figure 2 This is a schematic diagram of the auxiliary source circuit.

[0019] Figure 3 The diagram shows the startup and backup power supply circuit, where (a) is the circuit diagram and (b) is a typical operating waveform diagram.

[0020] Figure 4 This is another way to implement the control circuit in the startup and backup power supply circuit.

[0021] Figure 5 The diagram shows a steady-state power supply circuit, where (a) is a circuit diagram and (b) is a typical operating waveform diagram of the discontinuous current mode.

[0022] Figure 6 The equivalent circuits of the steady-state power supply circuit in each switching mode under the current discontinuous mode are shown, where (a) to (d) are the equivalent circuits under modes 1 to 4, respectively.

[0023] Figure 7 This is a typical operating waveform diagram of a steady-state power supply circuit in continuous current mode.

[0024] Figure 8 The equivalent circuits of the steady-state power supply circuit in each switching mode under continuous current mode are shown, where (a) to (c) are the equivalent circuits under modes 1 to 3, respectively.

[0025] Figure 9 The waveforms for simulation and experimental verification of the startup and backup power supply circuits are shown, where (a) is the simulation waveform and (b) is the experimental waveform.

[0026] Figure 10 The steady-state power supply circuit simulation and experimental verification waveform, wherein (a) is a simulation waveform, and (b) is an experimental waveform. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0028] It should be noted that if the present application embodiments involve "first", "second" and the like, the "first", "second" and the like are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features with "first", "second" can be explicitly or implicitly included at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the realization of ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the scope of protection claimed by the present application.

[0029] Figure 2 The auxiliary source circuit of the present application is given, which mainly includes an auxiliary winding, a first diode D 11 , a first capacitor C 11 , a starting and standby power supply circuit, a second capacitor C 12 , a voltage reduction and stabilization circuit, a second diode D 12 , a third capacitor C 13 and a steady-state power supply circuit.

[0030] The auxiliary winding in the auxiliary source circuit is coupled with the energy transmission inductor L f winding of the four-switch step-up and step-down converter (main power circuit of the power supply device), the output of the auxiliary winding is rectified by the first diode D 11 , filtered by the first capacitor C 11 , and the output voltage V C11 is:

[0031]

[0032] In the formula, n is the turn ratio of the L f winding relative to the auxiliary winding; the starting and standby power supply circuit takes power from the input of the converter and the two ends of the first capacitor C 11 , outputs the first auxiliary power V CC , and C 12 is its filter capacitor; the voltage reduction and stabilization circuit converts V CC into the second auxiliary power V DD1Output, and V DD1 < V CC ; V DD1 Through the second diode D 12 Get the third auxiliary power supply V DD , C 13 Its filter capacitor; steady-state power supply circuit from the four-switch buck-boost converter switch S3 and S4 switch bridge arm midpoint (ie V B ) take electricity, output V DD . The third auxiliary power supply V DD The main auxiliary source provides power to the power devices of the main power circuit.

[0033] Figure 3 The circuit composition and typical working waveform of the starting and standby power supply circuit are given. As shown in Figure 3 (a), the starting and standby power supply circuit mainly consists of a power circuit and a control circuit, wherein the power circuit of the starting and standby power supply circuit is composed of a first switch Q 21 ~ a second switch Q 22 , a first resistor R 21 and a third diode D 21 , and the control circuit thereof is composed of a sampling coefficient control circuit, a third switch Q 23 , a second resistor R 22 ~ a fourth resistor R 24 , an operational amplifier OP1, a first impedance network Z 21 ~ a second impedance network Z 22 and a fourth capacitor C 21 . In the figure, v CC_ctrl is a control signal output by the operational amplifier OP1, used to control the working state of the switches Q 21 and Q 22 , V ref1 is a first voltage reference value, v gsQ23 is a control signal output by the sampling coefficient control circuit, used to control the opening of the switch Q 23 , t 11 ~ t 14 is time.

[0034] Next, combined with the working state of the main power circuit (four-switch buck-boost converter) of the power supply device and Figure 3 (b) shows the typical working waveform, the working principle of the starting and standby power supply circuit is described as follows: before the main power circuit (four-switch buck-boost converter) starts to work, the input voltage V in is established first, V in charges the fourth capacitor C 21 through the first resistor R 21 , the first switch Q 21 and the second switch Q 22The gate voltage rises above its threshold voltage, the switch tube Q 21 and Q 22 channel starts to conduct, working in saturation region, the input voltage V in is charged through the channel of the first switch tube Q 21 , the third diode D 21 , the second capacitor C 12 , the first auxiliary power supply V CC starts to build up; since the main power circuit is not working at this time, the auxiliary winding output always remains low, the first diode D 11 is cut off, and the voltage V CC is charged through the channel of the second switch tube Q 22 to the first capacitor C 11 , and the voltage V C11 follows V CC and increases. At this time, the sampling coefficient control circuit outputs v gsQ23 high level, the third switch tube Q 23 is fully turned on, and the sampling feedback voltage V 22 at the connection point of the second resistor R 23 and the third resistor R FB1 is:

[0035]

[0036] The operational amplifier OP1 and the first impedance network Z 21 ~ the second impedance network Z 22 form a V CC voltage loop, amplify the error between the first voltage reference V ref1 and V FB1 , and output a control signal v CC_ctrl , and have

[0037] v CC_ctrl = G vcc (s)(V ref1 -V FB1 ) (3)

[0038] In the formula, G vcc (s) is the transfer function of the V CC voltage loop compensation network, and G vcc (s) = Z 22 (s) / Z 21 (s), where Z 21 (s) and Z 22 (s) are the transfer functions of the impedance networks Z 21 and Z 22 . When V CC is lower than the set value, i.e. V FB1 <V ref1 , V CCVoltage loop control v CC_ctrl increases, so that the gate-source voltage of the first switch tube Q 21 increases, the drain-source voltage difference of Q 21 is controlled to decrease, so that V CC increases until it is the same as the set value; when V CC is higher than the set value, V CC voltage loop control v CC_ctrl decreases, to increase the drain-source voltage difference of the first switch tube Q 21 , so as to decrease V CC until it is the same as the set value.

[0039] t 11 , the input voltage V in increases, and if v CC_ctrl remains unchanged, V CC will increase with V in , resulting in V FB1 >V ref1 , V CC voltage loop control v CC_ctrl decreases, the drain-source voltage difference of the first switch tube Q 21 increases, to avoid V CC from increasing, so that it remains stable at the set value. At t 13 , the sampling coefficient control circuit outputs v gsQ23 low level, the third switch tube Q 23 is turned off, the second resistor R 22 and the third resistor R 23 are connected, and the sampling feedback voltage V FB1 at the connection point becomes

[0040]

[0041] Since the changed sampling coefficient (R 23 +R 24 ) / (R 22 +R 23 +R 24 ) is greater than R 23 / (R 22 +R 23 ), at this time V FB1 will be greater than V ref1 , V CC voltage loop will control v CC_ctrl decrease, to increase the drain-source voltage difference of the first switch tube Q 21 , so as to decrease V CC until it is the same as the new set value. At t 14 , after the main power circuit starts to work, in the t0-t1 time period, the switch tubes S1 and S4 are turned on, and the L f winding voltage is Vin , the auxiliary winding voltage is V in / n, the first diode D 11 is turned on, and the first capacitor C 11 has a voltage equal to V in / n. Since v gsQ21 = v gsQ22 -V FD21 <v gsQ22 , where v gsQ21 and v gsQ22 are the gate-source voltages of the first switch Q 21 and the second switch Q 22 , V FD21 is the forward conduction voltage drop of the third diode D 21 , and V CC is the voltage across the first capacitor C 22 , V 11 is taken from the first capacitor C CC , the voltage loop controls v CC_ctrl to decrease to maintain V CC unchanged, while v gsQ21 is further decreased, so that the drain-source voltage difference of the first switch Q 21 is increased, V in is no longer supplied to V 21 through Q CC . The design is n>1, and is an integer, the Q 21 branch provides power supply before and during the start of the main power circuit, the Q 22 branch provides power supply after the start of the main power circuit, and the loss on the second switch Q 22 after the Q 22 branch supplies power is (V in / n-V CC )·I CC , where I CC is the load current of V CC , which will be lower than the loss on the third switch Q 21 when the Q 21 branch supplies power (is (V in -V CC )·I CC ), which can improve the overall efficiency of the system.

[0042] Figure 4 Another implementation of the control circuit in the start-up and standby power supply circuit is given, which is controlled by a sampling coefficient control circuit, a third switch Q 23 , second to fourth resistors R 22 ~ R 24 , a device TL431(U 21 ), a third impedance network Z 23 , and a fourth capacitor C21 The circuit principle is similar to that of the start-up and standby power supply circuit shown in Fig. Figure 3 (a), and the control circuit is similar to that of the start-up and standby power supply circuit shown in Fig. CC The voltage V 22 is divided by the second resistor R 24 ~ the fourth resistor R FB1 , and the voltage V 21 is obtained. FB1 The device TL431 (U CC_ctrl ) amplifies the error between V CC and its internal voltage reference and outputs it, and the size of v CC is adjusted to achieve voltage stabilization control of V DD1 .

[0043] Figure 2 The voltage V DD1 is converted into the second auxiliary power V DD_ref output by the voltage reduction and stabilization circuit in the auxiliary source circuit of the application shown in Fig. DD1 , and V DD_ref is controlled to be stable at the set value V DD . Before the start-up of the main power circuit is completed, the steady-state power supply circuit in the auxiliary source circuit does not have the ability to completely establish the third auxiliary power V DD at this time, V DD1 is charged to the capacitor C 12 by the second diode D 13 , and there is V DD = V DD1 -V FD12 = V DD_ref -V FD12 . Therefore, before and during the start-up, the main auxiliary power V DD of the main power circuit is provided by the start-up and standby power supply circuit through the voltage reduction and stabilization circuit and the second diode D 12 .

[0044] Figure 5 The circuit composition and typical working waveform of the steady-state power supply circuit are given. As shown in Fig. Figure 5 (a), the steady-state power supply circuit mainly consists of a power circuit and a control circuit, wherein the power circuit of the steady-state power supply circuit is composed of an inductor L 31 , a fourth diode D 31 ~ a sixth diode D 33 , and a fourth switch tube Q 31 , and the control circuit thereof is composed of a fifth resistor R 31 ~ a sixth resistor R 32 , an operational amplifier OP2, a fourth impedance network Z 31 ~ a fifth impedance network Z 32 , a comparator CP1, a NOT gate N1, an AND gate AND1, a monopulse trigger circuit 1, an RS flip-flop RS1, and a fifth capacitor C 31 .L31 For the current flowing through inductor L 31 The current, V ref2 The second voltage reference value, v er The error control signal output by OP2, v CTs The triangular wave voltage signal used for timing the main power circuit cycle, v S4_off The turn-off control signal for the main power transistor S4 (a high-level pulse signal, which is the same as the drive control signal v for the S4 transistor) is used in the main power circuit. GS4 (corresponding to the moment when it changes from high to low), v DD_ctrl The control signal output by RS1 of the RS flip-flop, v o_CP1 The output voltage of comparator CP1, v o_AND1 For the output voltage of the AND gate, v S_RS1 Let t be the voltage at the source (S) terminal of RS1 in the RS flip-flop. a ~t e t x ~t y For time.

[0045] Next, we will combine the working principle of the main power circuit and... Figure 5 (b) shows a typical operating waveform. The working principle of the steady-state power supply circuit is explained below, with the inductor (L) 31 In discontinuous current mode, the power circuit in the steady-state power supply circuit has four switching modes within one switching cycle.

[0046] Switching mode 1 [t] x ~t d In the main power circuit, switch S3 is turned on, and v B =V o ;t x After time t, the error control signal v er Less than v CTs The comparator CP1 outputs v o_CP1 High level, AND gate AND1 outputs v o_AND1 A high level signal triggers a single-pulse trigger circuit 1 to output a high-level pulse, controlling the RS flip-flop RS1 to set and output v. DD_ctrl High level controls the fourth switch Q. 31 Conduction, fifth diode D 32 On, inductor L 31 Current i L31 Linear increase, slope is (V) o -V DD ) / L 31 The equivalent circuit of the power circuit in the steady-state power supply circuit under this switching mode is as follows: Figure 6 As shown in (a).

[0047] Switching mode 2 [t]d ~t y ] : t d moment, switch S3 is off, and after a dead time, switch S4 is on, v B = 0; the fourth switch Q 31 , the fifth diode D 32 is on, inductor L 31 current i L31 decreases linearly with a slope of -V DD / L 31 , and the equivalent circuit of the power circuit in the steady-state power supply circuit under this switching mode is shown in Fig. Figure 6 (b).

[0048] Switching mode 3 [T y ~ T s + t b ] : t y moment, inductor L 31 current i L31 decreases to zero, the fifth diode D 32 is off with zero current, the fourth switch Q 31 is on, inductor L 31 current i L31 remains zero, and the equivalent circuit of the power circuit in the steady-state power supply circuit under this switching mode is shown in Fig. Figure 6 (c).

[0049] Switching mode 4 [T s + t b ~ T s + t x ] : T s + t b moment, switch S4 is off, and after a dead time, switch S3 is on, v B = V o ; at the same time when switch S4 is off, v S4_off signal controls RS flip-flop RS1 to reset, output v DD_ctrl low, controls the fourth switch Q 31 to be off, the sixth diode D 33 is on, and V DD charges the fifth capacitor C 31 ; at T s + t x moment, the front error control signal v er is greater than v CTs , comparator CP1 outputs v o_CP1 low, v DD_ctrl will remain low, and the fourth switch Q 31 remains off, and the equivalent circuit of the power circuit in the steady-state power supply circuit under this switching mode is shown in Fig. Figure 6As shown in (d). T s +t x After a certain time, it enters the next switching cycle; the operating process will not be described in detail here. Summarizing the operating process in discontinuous inductor current mode, we can see that the fifth diode D... 32 and the fourth switch Q 31 It can achieve zero-current switching, and can reduce losses when operating at high frequencies, which is beneficial to improving the overall system efficiency.

[0050] When V DD When the load current is large, the power circuit in the steady-state power supply circuit will operate in the continuous inductor current mode. The typical operating waveform of the circuit at this time is as follows: Figure 7 As shown, it has three switching modes within one switching cycle.

[0051] Switching mode 1 [t] x ~t d The operating process is consistent with the switching mode 1 in the discontinuous inductor current mode. The equivalent circuit is shown below. Figure 8 (a).

[0052] Switching mode 2 [t] d ~t y (T s +t b The operating process is consistent with the switching mode 2 in the discontinuous inductor current mode. The equivalent circuit is shown in [link to equivalent circuit]. Figure 8 (b)

[0053] Switching mode 3 [t] y (T s +t b )~T s +t x ]:t y (T s +t b Inductance L at any moment 31 Current i L31 The voltage has not decreased to zero. At this time, the switching transistor S4 in the main power circuit is turned off, and simultaneously v S4_off Signal control RS flip-flop RS1 reset, output v DD_ctrl Low level controls the fourth switch Q. 31 Turn off, fifth diode D 32 Turn off, fourth diode D 31 Freewheeling conduction, inductor L 31 current i L31 Keeping it unchanged, see the equivalent circuit. Figure 8 (c) Sixth diode D 33 On, V DD For the fifth capacitor C 31 Charging. s +t xAfter a certain time, the next switching cycle begins, and the working process will not be described in detail here.

[0054] Figure 5 In the steady-state power supply circuit shown in (a), the resistor R in the control circuit 31 and R 32 For V DD Perform voltage divider sampling to obtain the feedback voltage V FB2 (R 31 and R 32 Voltage at connection point), and V FB2 =[R 32 / (R 31 +R 32 )]·V DD Op-amp OP2 and fourth impedance network Z 31 ~Fifth impedance network Z 32 Composition V DD Voltage loop, V FB2 Second voltage reference V ref2 The error is amplified, and the output error control signal v is generated. er And there are

[0055] v er =G vdd (s)(V FB2 -V ref2 (5)

[0056] In the formula, G vdd (s) is V DD The transfer function of the voltage loop compensation network, and it has G vdd (s)=Z 32 (s) / Z 31 (s), where Z 31 (s) and Z 32 (s) represents the impedance network Z 31 and Z 32 The transfer function. When V DD Below the set value, i.e., V FB2 <V ref2 At that time, V DD Voltage loop control v er Decrease the duration of switching mode 1 (i.e., t) d -t x As the inductance L increases, 31 Increased energy storage, which in turn makes V DD Increase until it matches the set value; when V DD Higher than the set value, i.e., V FB2 >V ref2 At that time, V DD Voltage loop control v er Increasing this makes the duration of switching mode 1 (i.e., t) longer.d -t x The inductance L decreases. 31 Energy storage decreases, which in turn makes V DD Reduce until it matches the set value. The design includes V. ref2 =[R 32 / (R 31 +R 32 )]·V DD_ref That is, controlling V DD Stabilize at the set value V DD_ref Therefore, the steady-state power supply circuit has the capability to establish V DD And stabilized at V DD_ref back, Figure 2 The second diode D in the auxiliary source circuit of the present invention is shown. 12 It will be cut off at this time, that is, the main auxiliary power supply V of the main power circuit will be cut off. DD Powered by a steady-state power supply circuit, it is a switching circuit compared to the startup and backup power supply circuits, and can achieve soft switching, which can significantly reduce the losses of the auxiliary power source circuit and improve efficiency.

[0057] When the steady-state operating circuit fails, the startup and backup power supply circuit can continue to provide auxiliary power to the main power circuit, thus improving the fault tolerance of the auxiliary power supply circuit.

[0058] To further verify the effectiveness of the control method and circuit described in this invention, Figures 9-10 Simulation and experimental results for specific embodiments are given, and i in the figure Q21 and i Q22 For the current flowing through the switching transistor Q 21 and Q 22 The current. For example... Figure 9 As shown in (a), the startup and backup power supply circuits are at t a1 The sampling coefficient is changed constantly, and the control signal v CC_ctrl Decrease, V CC Quickly stabilizes at the new set value, at t a2 Power supply branch Q 21 Branch road changed to Q 22 Branch, control signal v CC_ctrl Further reduction, then Q 21 The branch circuit no longer provides energy, which helps reduce losses; such as Figure 9 As shown in (b), the startup and backup power supply circuit can follow the input voltage V. in Quickly build V CC , t b1 After the sampling coefficients are changed at any time, the control signal v CC_ctrl Decrease, V CC It quickly stabilizes at the new set value. For example... Figure 10As shown, the steady-state power supply circuit completes the startup of the main power circuit (V o After normal setup, it provides a stable V DD Power supply, inductor current i L31 When the switching device is discontinuous, it can achieve zero-current switching, which helps to reduce losses.

[0059] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention without departing from its spirit and scope should be included within the protection scope of the present invention.

Claims

1. An auxiliary source circuit, characterized in that, The circuit includes an auxiliary winding, a start-up and backup power supply circuit, a buck regulator circuit, and a steady-state power supply circuit; the auxiliary winding is connected to the main power circuit of the power supply unit, i.e., the energy transfer inductor L of the four-switch buck-boost converter. f The windings are mutually coupled, and the auxiliary winding outputs a voltage V after rectification and filtering. C11 The startup and backup power supply circuit is based on the input voltage V of the main power circuit of the power supply unit. in and the voltage V C11 Output first auxiliary power supply V CC Then, it is converted into a second auxiliary power supply V through a step-down regulator circuit. DD1 V DD1 <V CC The step-down voltage regulator circuit controls V DD1 Stabilize at the set value V DD_ref The second auxiliary power supply V DD1 via the second diode D 12 Third auxiliary power supply V output DD Meanwhile, the steady-state power supply circuit draws power from the midpoint of the switching bridge arm formed by switching transistors S3 and S4 in the four-switch buck-boost converter, i.e., v. B Power is drawn, and the output V is generated. DD Third auxiliary power supply V DD It serves as the main auxiliary power source, supplying power to the electrical components in the main power circuit. The startup and backup power supply circuit includes a power circuit and a control circuit, wherein the power circuit includes a first switching transistor Q. 21 ~Second switching transistor Q 22 First resistor R 21 and the third diode D 21 The control circuit includes a sampling coefficient control circuit and a third switching transistor Q. 23 Second resistor R 22 Third resistor R 23 Fourth resistor R 24 Operational amplifier OP1, first impedance network Z 21 ~Second impedance network Z 22 and the fourth capacitor C 21 ; The input voltage V in Connect the first switching transistor Q 21 The drain of the capacitor is simultaneously connected to the first resistor R. 21 Connect the first switching transistor Q 21 The gate of the second switch Q 22 The gate of the op-amp and the output of op-amp OP1 are connected through the fourth capacitor C. 21 Grounding, first switch Q 21 The source of the third diode D is connected. 21 The positive terminal; the voltage V C11 Connect the second switching transistor Q 22 The drain of the sampling coefficient control circuit; the control signal v output by the sampling coefficient control circuit. gsQ23 Connect the third switch Q 23 The gate of the third switch Q 23 A fourth resistor R is connected in parallel between the source and drain. 24 Meanwhile, the third switch Q 23 The source is grounded, and the third switch Q is... 23 The drain is connected in series with the third resistor R. 23 Second resistor R 22 The third resistor R 23 Second resistor R 22 The common terminal is connected through the first impedance network Z. 21 Connect the negative input terminal of operational amplifier OP1, which is also connected to the second impedance network Z. 22 Connect the output terminal of op-amp OP1, and input the first voltage reference value V to the positive input terminal of op-amp OP1. ref1 The third diode D 21 The negative terminal, the second switching transistor Q 22 The source and the second resistor R 22 The other end is connected to the second capacitor C 12 Grounded, and simultaneously outputs the first auxiliary power supply V. CC .

2. The auxiliary source circuit according to claim 1, characterized in that, The auxiliary winding output is transmitted via the first diode D. 11 Rectifier, first capacitor C 11 Filtering, voltage V C11 for: In the formula, n is L f The turns ratio of the winding relative to the auxiliary winding.

3. The auxiliary source circuit according to claim 1, characterized in that, The circuit also includes a second capacitor C. 12 As the first auxiliary power supply V CC Filter capacitors.

4. The auxiliary source circuit according to claim 1, characterized in that, The circuit also includes a third capacitor C. 13 As the third auxiliary power supply V DD Filter capacitors.

5. The auxiliary source circuit according to claim 1, characterized in that, The operational amplifier OP1 and the first impedance network Z 21 ~Second impedance network Z 22 Composition V CC The voltage loop will set the first voltage reference V. ref1 With the second resistor R 22 and the third resistor R 23 Sampling feedback voltage V at the connection point FB1 The error is amplified, and the output control signal v is used. CC_ctrl : v CC_ctrl =G vcc (s)(V ref1 -V FB1 ) In the formula, G vcc (s) is V CC The transfer function of the voltage loop compensation network, and it has G vcc (s)=Z 22 (s) / Z 21 (s), where Z 21 (s) and Z 22 (s) represents the impedance network Z 21 and Z 22 The transfer function; where the sampling coefficient control circuit outputs v gsQ23 When it is high level, v gsQ23 When it is low level, 6. The auxiliary source circuit according to claim 1, characterized in that, The control circuit is replaced with a sampling coefficient control circuit and a third switch Q. 23 Second resistor R 22 Third resistor R 23 Fourth resistor R 24 The third impedance network Z 23 TL431 device U 21 and the fourth capacitor C 21 The control signal v output by the sampling coefficient control circuit gsQ23 Connect the third switch Q 23 The gate of the third switch Q 23 A fourth resistor R is connected in parallel between the drain and source. 24 The fourth resistor R 24 One end is grounded, and it is also connected to the TL431 device U. 21 The anode A is connected to the other end via a third resistor R in series. 23 Second resistor R 22 Output first auxiliary power supply V CC The third resistor R 23 Second resistor R 22 The common terminal is connected through a third impedance network Z. 23 Fourth capacitor C 21 Grounded, and connected to TL431 device U. 21 The reference pole R, the third impedance network Z 23 and the fourth capacitor C 21 The common terminal connects to the TL431 device U. 21 Cathode K and control signal v CC_ctrl V CC Through the second resistor R 22 Third resistor R 23 Fourth resistor R 24 Voltage division is used to obtain the sampling feedback voltage V. FB1 TL431 device U 21 V FB1 The error between the voltage and its internal voltage reference is amplified and output, and the voltage is adjusted by v. CC_ctrl Size implementation V CC Voltage regulation control.

7. The auxiliary source circuit according to claim 1 or 4, characterized in that, The steady-state power supply circuit includes a power circuit and a control circuit, wherein the power circuit includes an inductor L. 31 Fourth diode D 31 Fifth diode D 32 The sixth diode D 33 and the fourth switch Q 31 The control circuit includes a fifth resistor R. 31 ~Sixth resistor R 32 Operational amplifier OP2, fourth impedance network Z 31 ~Fifth impedance network Z 32 Comparator CP1, NOT gate N1, AND gate AND1, single-pulse trigger circuit 1, RS flip-flop RS1, and fifth capacitor C 31 The inductor L 31 One end is connected to the midpoint of the switch bridge arm composed of switching transistors S3 and S4, i.e., v B The other end is connected to the fourth diode D. 31 The output voltage V of the four-switch buck-boost converter o Simultaneously through the fifth diode D 32 Connect the fourth switch Q 31 The drain of the fourth switch Q 31 The source is connected to the third capacitor C. 13 Grounding, also through the sixth diode D 33 Fifth capacitor C 31 Connect the Q terminal of RS flip-flop RS1, and simultaneously connect it to the fifth resistor R. 31 Connect the positive input terminal of op-amp OP2, which is also connected to the sixth resistor R. 32 Ground; Second diode D 12 The positive terminal is connected to the second auxiliary power supply V. DD1 The negative terminal is connected to the third auxiliary power supply V. DD and the fourth switch Q 31 The source and the fifth resistor R 31 The common terminal; the fourth switch Q 31 The gate of the sixth diode D is connected. 33 Fifth capacitor C 31 The common terminal, and the sixth diode D 33 The negative terminal is connected; the negative input terminal of the operational amplifier OP2 is connected through the fourth impedance network Z. 31 Connect the second voltage reference value V ref2 Simultaneously through the fifth impedance network Z 32 Connect the output of operational amplifier OP2 to the negative input of comparator CP1; the positive input of comparator CP1 is connected to the triangular wave voltage signal used for timing the main power circuit, and its output is connected to AND gate AND1; the switching transistor S4 drives the control signal v. GS4 After passing through NOT gate N1, it is connected to AND gate AND1. The output signal of AND gate AND1 is connected to the S terminal of RS flip-flop RS1 after passing through single pulse trigger circuit 1. The R terminal of RS flip-flop RS1 is input to the turn-off control signal of the switching transistor S4 in the main power circuit.

8. The auxiliary source circuit according to claim 7, characterized in that, The operational amplifier OP2 and the fourth impedance network Z 31 ~Fifth impedance network Z 32 Composition V DD Voltage loop, with the fifth resistor R 31 and the sixth resistor R 32 Voltage V at connection point FB2 Second voltage reference V ref2 The error is amplified, and the output error control signal v is generated. er And there are: v er =G vdd (s)(V FB2 -V ref2 ) In the formula, G vdd (s) is V DD The transfer function of the voltage loop compensation network, and it has G vdd (s)=Z 32 (s) / Z 31 (s), where Z 31 (s) and Z 32 (s) represents the impedance network Z 31 and Z 32 The transfer function; where V ref2 =[R 32 / (R 31 +R 32 )]·V DD_ref V FB2 =[R 32 / (R 31 +R 32 )]·V DD .

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