Zero-current soft switching Boost circuit

Abstract

The utility model discloses a zero current soft switching Boost circuit. The circuit comprises an input power supply BT, an inductor L, a fly-wheel diode D, an output capacitor C, a power switch tube Q, a resonant capacitor Cs, a resonant capacitor Cr, a resonant inductor Lr and a resonant silicon controlled rectifier Dr, the positive electrode of the input power supply BT is connected with one end of the inductor L, and the other end of the inductor L is connected with the positive electrode of the fly-wheel diode D, the drain electrode of the power switch tube Q, one end of the resonant capacitor Cs and one end of the resonant inductor Lr. The cathode of the fly-wheel diode D is connected with one end of the output capacitor C, the other end of the resonant inductor Lr is connected with one end of the resonant capacitor Cr, the other end of the resonant capacitor Cr is connected with one end of the resonant silicon controlled rectifier Dr, and the cathode of the input power supply BT is connected with the other end of the resonant silicon controlled rectifier Dr, the other end of the output capacitor C, the source electrode of the power switch tube Q and the other end of the resonant capacitor Cs. The utility model has the beneficial effect that the service life of the battery of the electric bicycle can be prolonged.

Description

Technical Field

[0001] The utility model relates to the technical field of Boost circuits, in particular to a zero-current soft-switching Boost circuit. Background Art

[0002] Electric bicycles are a "miracle" in our country. Just as the United States has no high-speed rail and bicycles are popular in Northern Europe, they are all dominated by the economic and technological conditions in each place, and very simple changes can be extremely difficult; however, there are indeed "defects" in the design of electric bicycles. Due to economic reasons, electric bicycles cannot have as many battery supplies as electric vehicles. Therefore, the series-connected batteries of electric bicycles inherently have the phenomenon of overcharging and over-discharging, resulting in problems with the battery life of electric bicycles.

[0003] It is difficult to question the current method of battery supply for electric bicycles. When the batteries are new, using a series-connected battery supply form should be the simplest and most effective form; however, series-connected batteries require the voltage of each battery to be highly averaged. If there are differences, it will cause the weaker ones to get out of control, and there is a vicious cycle of the weaker ones becoming even weaker; fortunately, when a group of batteries fails and the weaker batteries are scrapped after the failure of the battery pack, we find that there are still other batteries in the failed battery pack that can be used.

[0004] For the batteries that can be used in the failed battery pack, the current popular treatment method is to recycle, repair and test them and use them as repaired batteries; however, if the recycled batteries continue to be used in series-connected batteries, it is very obvious that the usage effect is difficult to compare with that of new batteries. Therefore, this is only one of the treatment methods for failed battery packs. Content of the Utility Model

[0005] The utility model aims to overcome the above-mentioned deficiencies in the prior art and provides a zero-current soft-switching Boost circuit that can improve the battery life of electric bicycles.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A zero-current soft-switching Boost circuit, comprising an input power supply BT, an inductor L, a freewheeling diode D, an output capacitor C, a power switch Q, a resonant capacitor Cs, a resonant capacitor Cr, a resonant inductor Lr, a resonant thyristor Dr and a load. The positive pole of the input power supply BT is connected to one end of the inductor L. The other end of the inductor L is respectively connected to the anode of the freewheeling diode D, the drain of the power switch Q, one end of the resonant capacitor Cs and one end of the resonant inductor Lr. The cathode of the freewheeling diode D is respectively connected to one end of the output capacitor C and one end of the load. The other end of the resonant inductor Lr is connected to one end of the resonant capacitor Cr. The other end of the resonant capacitor Cr is connected to one end of the resonant thyristor Dr. The negative pole of the input power supply BT is respectively connected to the other end of the resonant thyristor Dr, the other end of the output capacitor C, the source of the power switch Q, the other end of the resonant capacitor Cs and the other end of the load.

[0008] The utility model uses a boost circuit to boost the voltage of the battery and replaces the series connection mode of the battery with a parallel connection mode to solve the drawback of the vicious cycle of the battery pack where the weaker one becomes even weaker in a series-connected battery pack. Especially if this battery is the surviving battery of a failed battery pack, compared to the work of repairing, testing, transporting, etc., adding an economically feasible boost circuit to these batteries is another effective solution to the battery life of electric bicycles. If the boost parallel battery solution is effective, the boost circuit needs to be reliable. If there is no way to make the boost circuit reliable and it is even less reliable than repairing the battery, then this solution fails. Therefore, we cannot require the manufacturer in terms of manufacturing process, nor can we require the supplier in terms of device quality. However, we can make this circuit more advanced in technical design. This is the purpose of our unique soft-switching patent proposed for this classic boost BOOST circuit. Especially when the power switch is turned off, a resonant circuit is used to divert the current that originally flowed through the power switch, gradually reducing the current flowing through the power switch to zero instead of simply turning off the power switch passively and allowing the current to flow elsewhere, which can make the zero-current turn-off of the power switch more effective.

[0009] Preferably, the resonant capacitor Cs and the inductor L form a first soft-switching resonant circuit branch. After the inductor L releases energy, the first soft-switching resonant circuit branch resonates, and the energy of the resonant capacitor Cs is transformed to change the potential of the output end of the inductor L to achieve zero-voltage turn-on of the power switch Q. At this time, the current Iq flowing through the power switch Q is zero.

[0010] Preferably, the resonant inductor Lr, the resonant capacitor Cr, and the resonant thyristor Dr form the second branch of the soft-switching resonant circuit; before the power switch Q turns off, the resonant thyristor Dr is activated, and the second branch of the soft-switching resonant circuit resonates to divert the current flowing through the power switch Q. When the current of the resonant capacitor Cr in the second branch of the resonant circuit develops to be the same as the current of the inductor L, zero-current turn-off of the power switch Q is achieved. At this time, the voltage Vq between the drain and source of the power switch Q is zero.

[0011] Preferably, one end of the resonant capacitor Cs is connected to the other end of the inductor L; the resonant inductor Lr, the resonant capacitor Cr, and the resonant thyristor Dr are connected in series in sequence. One end of the resonant inductor Lr is connected to the anode of the freewheeling diode D, thereby realizing lossless operation of the circuit in each switching cycle.

[0012] Preferably, an auxiliary circuit is connected between one end of the resonant capacitor Cs and one end of the resonant capacitor Cr. The auxiliary circuit includes an analog switch SW1A and an amplifier OP1A. The output end of the analog switch SW1A is connected to the non-inverting input end of the amplifier OP1A. The inverting input end and the output end of the amplifier OP1A are both connected to one end of the resonant capacitor Cs. The two input ends of the analog switch SW1A are respectively connected to one end of the resonant capacitor Cr and one end of the resonant capacitor Cs. The control end of the analog switch SW1A is connected to a single-chip microcomputer.

[0013] The beneficial effects of the present utility model are as follows: It solves the drawback of the vicious cycle of weaker battery packs in series battery packs and can improve the battery life of electric bicycles. Description of the Drawings

[0014] Figure 1 is a schematic diagram of the circuit working state of the present utility model in the stage from t0 to t1;

[0015] Figure 2 is a schematic diagram of the circuit working state of the present utility model in the stage from t1 to t2;

[0016] Figure 3 is a schematic diagram of the circuit working state of the present utility model in the stage from t2 to t3;

[0017] Figure 4 is a schematic diagram of the circuit working state of the present utility model in the stage from t3 to t4;

[0018] Figure 5 is a schematic diagram of the circuit working state of the present utility model in the stage from t4 to t5;

[0019] Figure 6 is a schematic diagram of the circuit working state of the present utility model in the stage from t5 to t6 (t0);

[0020] Figure 7 is the timing diagram of the circuit working state of the present invention;

[0021] Figure 8 is the schematic diagram of the auxiliary circuit in the t2 - t3 stage of the present invention. Specific Embodiments

[0022] The following further describes the present utility model in conjunction with the accompanying drawings and specific embodiments.

[0023] As Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 In the described embodiments, a zero - current soft - switching Boost circuit includes an input power supply BT, an inductor L, a free - wheeling diode D, an output capacitor C, a power switch Q, a resonant capacitor Cs, a resonant capacitor Cr, a resonant inductor Lr, a resonant thyristor Dr, and a load. The positive pole of the input power supply BT is connected to one end of the inductor L. The other end of the inductor L is respectively connected to the anode of the free - wheeling diode D, the drain of the power switch Q, one end of the resonant capacitor Cs, and one end of the resonant inductor Lr. The cathode of the free - wheeling diode D is respectively connected to one end of the output capacitor C and one end of the load. The other end of the resonant inductor Lr is connected to one end of the resonant capacitor Cr. The other end of the resonant capacitor Cr is connected to one end of the resonant thyristor Dr. The negative pole of the input power supply BT is respectively connected to the other end of the resonant thyristor Dr, the other end of the output capacitor C, the source of the power switch Q, the other end of the resonant capacitor Cs, and the other end of the load.

[0024] The resonant capacitor Cs and the inductor L form the first soft - switching resonant circuit branch. After the inductor L releases energy, the first soft - switching resonant circuit branch resonates, and the energy of the resonant capacitor Cs is transformed to change the potential of the output end of the inductor L, so as to realize the zero - voltage turn - on of the power switch Q. At this time, the current Iq flowing through the power switch Q is zero.

[0025] The resonant inductor Lr, the resonant capacitor Cr, and the resonant thyristor Dr form the second soft - switching resonant circuit branch. Before the power switch Q turns off, the resonant thyristor Dr starts, and the second soft - switching resonant circuit branch resonates to divert the current flowing through the power switch Q. When the current of the resonant capacitor Cr in the second resonant circuit branch develops to be the same as the current of the inductor L, the zero - current turn - off of the power switch Q is realized. At this time, the voltage Vq between the drain and the source of the power switch Q is zero.

[0026] One end of the resonant capacitor Cs is connected to the other end of the inductor L; the resonant inductor Lr, the resonant capacitor Cr, and the resonant thyristor Dr are connected in series in sequence. One end of the resonant inductor Lr is connected to the anode of the freewheeling diode D, thereby realizing the lossless operation of the circuit within each switching period.

[0027] As Figure 8 shown, an auxiliary circuit is connected to one end of the resonant capacitor Cs and one end of the resonant capacitor Cr. The auxiliary circuit includes an analog switch SW1A and an amplifier OP1A. The output end of the analog switch SW1A is connected to the non-inverting input end of the amplifier OP1A. The inverting input end and the output end of the amplifier OP1A are both connected to one end of the resonant capacitor Cs. The two input ends of the analog switch SW1A are respectively connected to one end of the resonant capacitor Cr and one end of the resonant capacitor Cs. The control end of the analog switch SW1A is connected to a single-chip microcomputer.

[0028] The operating mode of this zero-current soft-switching Boost circuit is the discontinuous current operating mode, and there are six states within each switching period. Assuming that the voltage at the negative terminal of the input power supply BT is 0V and the voltage at the positive terminal of the input power supply BT is 12V, the end of the inductor L connected to the positive terminal of the input power supply BT is the inlet end, and the voltage at the inlet end of the inductor L always remains consistent with the voltage at the positive terminal of the input power supply BT. The other end of the inductor L is the outlet end, and specifically as follows:

[0029] (1) Stage t0 - t1: At moment t0, the voltage at the outlet end of the inductor L is 0V, the voltage of the resonant capacitor Cr is a fixed value, the resonant thyristor Dr is started, the power switch tube Q is in the on state, and the resonant capacitor Cs is clamped by the power switch tube Q and is in a non-operating state; as time goes on, the current I of the inductor L flows to the power switch tube Q, and the current I of the inductor L linearly rises, and at the same time stores energy. A resonant circuit is formed through the resonant thyristor Dr, the resonant capacitor Cr, and the resonant inductor Lr to work stably. The current Ir of the resonant capacitor Cr flows to the power switch tube Q, and the voltage Vr of the resonant capacitor Cr changes from positive to negative, and the current Ir of the resonant capacitor Cr first linearly rises and then linearly falls; as Figure 1 shown.

[0030] (2) Stage t1 - t2: At time t1, the voltage at the output terminal of inductor L is still 0V, the voltage of resonant capacitor Cr is negative, and the current Ir of resonant capacitor Cr is zero. As time continues, the current Ia flowing through resonant inductor Lr reverses. The power switch Q remains in the on state, and the current I of inductor L still flows towards power switch Q. Moreover, the current I of inductor L continues to linearly increase and store energy simultaneously. However, the current passing through power switch Q is diverted by the current Ia of resonant inductor Lr, and the current Ia of resonant inductor Lr linearly increases. The voltage of resonant capacitor Cr also linearly increases. The current Ia of resonant inductor Lr forms a resonant circuit through resonant thyristor Dr, resonant capacitor Cr, and resonant inductor Lr to operate stably until time t2, when the current Ia of resonant inductor Lr becomes equal to the current I flowing through inductor L, and the current flowing through power switch Q is zero. At this time, power switch Q turns off with zero current, and the voltage between the drain and source of power switch Q is zero; as Figure 2 shown.

[0031] (3) Stage t2 - t3: At time t2, the voltage of resonant capacitor Cr becomes zero, and power switch Q is in the off state. As time continues, resonant capacitor Cs starts to store energy. As the voltage of resonant capacitor Cs rises, the voltage at the output terminal of inductor L is continuously pulled up. During the period until the voltage at the output terminal of inductor L is the same as the voltage at the input terminal of inductor L, the current I of inductor L continues to linearly increase and store energy simultaneously. After that, the voltage at the output terminal of inductor L is greater than the voltage at the input terminal of inductor L, and the current I of inductor L starts to linearly decrease and release energy. Part of the current I of inductor L flows as current Ib to resonant capacitor Cs, and the other part of the current I of inductor L flows as current I - Ib to resonant capacitor Cr. The voltages of both resonant capacitor Cr and resonant capacitor Cs linearly increase. Since power switch Q is in the off state, its voltage changes with the voltage of resonant capacitor Cs until freewheeling diode D conducts. Among them, the current flowing into the resonant circuit composed of resonant inductor Lr, resonant capacitor Cr, and resonant thyristor Dr remains constant; as Figure 3 shown.

[0032] To ensure that during the period from when power switch Q turns off to when the voltages of resonant capacitor Cs and resonant capacitor Cr rise to make the freewheeling diode conduct, the current flowing into the resonant circuit composed of resonant inductor Lr, resonant capacitor Cr, and resonant thyristor Dr remains constant, an auxiliary circuit is designed to achieve this, as Figure 8As shown, it includes analog switch SW1A and amplifier OP1A. The output terminal of analog switch SW1A is connected to the non-inverting input terminal of amplifier OP1A. The inverting input terminal and the output terminal of amplifier OP1A are both connected to one end of resonant capacitor Cs. The two input terminals of analog switch SW1A are respectively connected to one end of resonant capacitor Cr and one end of resonant capacitor Cs. The control terminal of analog switch SW1A is connected to a single-chip microcomputer; a resonant circuit composed of resonant thyristor Dr, resonant capacitor Cr, and resonant inductor Lr starts to generate a ringing phenomenon from the current cycle t3. The voltage on resonant capacitor Cr swings up and down between 48V and 0V. If no control is applied, the voltage on resonant capacitor Cr will finally stay at 24V; but if the number of ringing times is controlled, when the resonant current Ir is equal to zero during a certain ringing, 24V > the voltage on resonant capacitor Cr > 0V, control the resonant thyristor Dr to turn off. At this time, the voltage on resonant capacitor Cr determines the current flowing into the resonant circuit composed of resonant thyristor Dr, resonant capacitor Cr, and resonant inductor Lr at the next cycle t2, that is, all the current flowing out of inductor L at the next cycle t2, making the current flowing through power switch tube Q zero, and power switch tube Q turns off. The current flowing through the resonant circuit composed of resonant thyristor Dr, resonant capacitor Cr, and resonant inductor Lr is equal to the current of inductor L. While turning off power switch tube Q, the single-chip microcomputer issues a control signal to start analog switch SW1A, making the non-inverting input terminal of amplifier OP1A connect to the voltage of resonant capacitor Cr, ensuring that the voltages of resonant capacitor Cs and resonant capacitor Cr are the same. Then the voltage of resonant inductor Lr is zero, that is, the voltage at the inlet of resonant inductor Lr is equal to the voltage at the outlet of resonant inductor Lr. At this time, the current flowing through resonant inductor Lr does not change, that is, the current flowing into resonant capacitor Cr becomes constant starting from the next cycle t2, and the current flowing through inductor L changes with time. The changing part all flows into resonant capacitor Cs, and through the adjustment of amplifier OP1A, ensure that resonant capacitor Cs and resonant capacitor Cr rise synchronously. The time process is the t2 - t3 stage of the next cycle.

[0033] (4) Stage t3 - t4: At time t3, the voltage at the output terminal of inductor L is 24V, the voltages of resonant capacitor Cs and power switch Q are both 24V, the voltage of resonant capacitor Cr is a fixed voltage, and freewheeling diode D conducts forward. As time goes on, inductor L starts to charge output capacitor C, and the current I flowing through inductor L decreases linearly until it reaches zero, and the circuit reaches a stable operating state. Since there is no current flowing in or out of resonant capacitor Cs, the voltage of resonant capacitor Cs remains 24V. At the same time, the voltage at the output terminal of inductor L is the same as the voltage of resonant capacitor Cs, and the voltage of power switch Q remains 24V because it is in the off state. Ringing occurs on resonant capacitor Cr, and the ringing amplitude changes gradually from large to small. At this time, according to the magnitude of the maximum current flowing into resonant inductor Lr and resonant capacitor Cr in the previous cycle, the voltage of resonant capacitor Cr is determined by feedback. During the ringing process, at a certain cycle time, when the resonant current is zero, the voltage of the resonant capacitor <24V and >0V, the resonant thyristor is turned off, so that the voltage on the resonant capacitor can ensure that at the next cycle t2, the voltage of resonant capacitor Cr is zero, and the current flowing into resonant capacitor Cr is equal to the current flowing out through inductor L that needs to be turned off (the current flowing to the power switch is zero); as Figure 4 shown.

[0034] (5) Stage t4 - t5: At time t4, freewheeling diode D turns off, the discharge of inductor L ends, the current of inductor L is zero, the voltage at the output terminal of inductor L is 24V, the voltages of resonant capacitor Cs and power switch Q are both 24V, the voltage of resonant capacitor Cr is a fixed value, and resonant thyristor Dr is turned off. As time goes on, resonant capacitor Cs discharges, the current Ic of resonant capacitor Cs flows through inductor L to input battery BT, and resonant capacitor Cs and inductor L resonate. The voltage of resonant capacitor Cs decreases linearly. As the voltage of resonant capacitor Cs decreases, the voltage at the output terminal of inductor L is continuously pulled down until the voltage at the output terminal of inductor L is the same as the voltage at the input terminal of inductor L. During this period, the current I of inductor L continues to increase linearly. After that, the voltage at the output terminal of inductor L is less than the voltage at the input terminal of inductor L, and the current I of inductor L starts to decrease linearly until at time t5, the voltage at the positive terminal of resonant capacitor Cs is zero (the voltage across both ends is -12V). Among them, resonant thyristor Dr is always in the off state, the current of resonant capacitor Cr is zero, and the voltage remains unchanged. Power switch Q is also always in the off state, the current of power switch Q is zero, and the energy of inductor L flows back into input battery BT reversely without passing through power switch Q. The voltage of power switch Q has a decreasing process after the discharge of resonant capacitor Cs, that is, from 24V to 0V; as Figure 5 shown.

[0035] (6) Stage t5 - t6 (t0): At time t5, the voltage at the output terminal of inductor L is zero, the current through inductor L is zero, power switch Q turns on, and the voltage across power switch Q is zero. As time progresses, the current I through inductor L starts to increase linearly from zero, and the circuit reaches a stable operating state. Among them, resonant thyristor Dr remains in the off state, the current through resonant capacitor Cr is zero, and the voltage remains unchanged. Power switch Q remains in the on state, resonant capacitor Cs is clamped by power switch Q and is in a non - working state, the current through resonant capacitor Cs is zero, and the voltage remains unchanged. As Figure 6 shown.

[0036] Among them, the specific timing diagrams of the six states existing in each switching cycle are as Figure 7 shown.

[0037] The utility model uses a boost circuit to boost the voltage of the battery and replaces the series connection of the batteries in parallel to solve the problem of the vicious cycle of the weaker batteries in the series battery pack; especially if this battery is the surviving battery of a failed battery pack, compared with the work of repair, testing, transportation, etc., adding an economically viable boost circuit to these batteries is another effective solution to the battery life of electric bicycles.

[0038] If the boost - parallel battery solution is effective, the boost circuit needs to be reliable; if there is no way to make the boost circuit reliable and it is even less reliable than the reliability of repairing the battery, then this solution is a failure. Therefore, we cannot require the manufacturer in the manufacturing process, nor can we require the supplier in terms of device quality, but we can make this circuit more advanced in the technical design. This is the purpose of our unique soft - switch patent proposed for this classic boost BOOST circuit; especially when the power switch is turned off, a resonant circuit is used to divert the current that originally flowed through the power switch, allowing the current that originally flowed through the power switch to gradually decrease to zero, rather than simply turning off the power switch passively and letting the current flow elsewhere, which can make the zero - current turn - off of the power switch more effective.

Claims

1. A zero current soft switching Boost circuit, characterized in that: It includes an input power supply BT, an inductor L, a freewheeling diode D, an output capacitor C, a power switch tube Q, a resonant capacitor Cs, a resonant capacitor Cr, a resonant inductor Lr, a resonant thyristor Dr and a load. The positive electrode of the input power supply BT is connected to one end of the inductor L, and the other end of the inductor L is respectively connected to the anode of the freewheeling diode D, the drain of the power switch tube Q, one end of the resonant capacitor Cs and one end of the resonant inductor Lr. The cathode of the freewheeling diode D is respectively connected to one end of the output capacitor C and one end of the load. The other end of the resonant inductor Lr is connected to one end of the resonant capacitor Cr, and the other end of the resonant capacitor Cr is connected to one end of the resonant thyristor Dr. The negative electrode of the input power supply BT is respectively connected to the other end of the resonant thyristor Dr, the other end of the output capacitor C, the source of the power switch tube Q, the other end of the resonant capacitor Cs and the other end of the load.

2. A zero current soft switching Boost circuit according to claim 1, characterized in that: The resonant capacitor Cs and the inductor L form a soft switching resonant circuit branch 1; After the inductor L releases energy, the soft-switching resonant circuit branch resonates, and the energy of the resonant capacitor Cs is transformed to change the potential of the output end of the inductor L, so as to realize the zero-voltage turn-on of the power switch tube Q. At this time, the current Iq flowing through the power switch tube Q is zero.

3. The zero current soft switching Boost circuit according to claim 1, characterized in that: The resonant inductor Lr, the resonant capacitor Cr and the resonant thyristor Dr form a second branch of a soft switching resonant circuit; before the power switch tube Q is turned off, the resonant thyristor Dr is started, and the second branch of the soft switching resonant circuit resonates, draining the current through the power switch tube Q. When the current of the resonant capacitor Cr in the second branch of the resonant circuit develops to the same as the current of the inductor L, the zero current shutdown of the power switch tube Q is achieved, and at this time, the voltage Vq between the drain and source of the power switch tube Q is zero.

4. The zero current soft switching Boost circuit according to claim 1, characterized in that: One end of the resonant capacitor Cs is connected to the other end of the inductor L; the resonant inductor Lr, the resonant capacitor Cr and the resonant thyristor Dr are connected in series in sequence, and one end of the resonant inductor Lr is connected to the anode of the freewheeling diode D, thereby achieving lossless operation of the circuit in each switching cycle.

5. The zero current soft switching Boost circuit according to claim 1, characterized in that: An auxiliary circuit is connected to one end of the resonant capacitor Cs and one end of the resonant capacitor Cr, and the auxiliary circuit includes an analog switch SW1A and an amplifier OP1A, wherein the output end of the analog switch SW1A is connected to the non-inverting input end of the amplifier OP1A, the inverting input end of the amplifier OP1A and the output end of the amplifier OP1A are both connected to one end of the resonant capacitor Cs, the two input ends of the analog switch SW1A are respectively connected to one end of the resonant capacitor Cr and one end of the resonant capacitor Cs, and the control end of the analog switch SW1A is connected to a single-chip microcomputer.

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