High voltage doubling circuit for DC-DC conversion circuit

Abstract

The invention provides a high-voltage voltage-multiplying circuit for a DC-DC conversion circuit. The high-voltage voltage-multiplying circuit comprises a basic voltage-multiplying module and an expansion voltage-multiplying module, wherein the basic voltage-multiplying module consists of four rectification branches; the expansion voltage-multiplying module consists of two expansion rectification branches; each of the rectification branch and the expansion rectification branch is formed by connecting a unilateral diode and a capacitor in series; the four rectification branches in the basic voltage-multiplying module are connected in parallel, and the voltage-multiplying capability of four times of voltage is provided. In the expansion voltage-multiplying module, the unilateral diodes of the second expansion rectification branch and the first expansion rectification branch are reversely connected in parallel; m expansion voltage-multiplying modules are selected to be cascaded according to the required voltage-multiplying multiple; and the capacitor in the fourth rectification branch and the capacitor in the second expansion rectification branch in each expansion voltage-multiplying module are jointly connected in series to supply power to the load and provide 4 + 2m double voltage. According to the invention, the voltage-multiplying multiple of the output voltage can be changed by increasing or reducing the rectification branches, the voltage-multiplying capability is high, and the cost is saved.

Description

Technical Field

[0001] The invention relates to the technical field of circuit design, and in particular to a novel high-voltage voltage doubling circuit for a DC-DC conversion circuit. Background Art

[0002] In recent years, high-voltage DC power supplies have been widely used in fields such as X-ray systems, electrostatic dust removal, and high-voltage insulation testing. Therefore, high-voltage voltage doubler circuits play an important role in high-voltage DC power supplies. In high-voltage conversion systems, high-voltage voltage doubler circuits can be connected to the secondary side of the transformer to perform secondary voltage boosting on the voltage output from the secondary side of the transformer. Traditional DC-DC conversion circuits usually do not contain resonant circuits, and high voltage is achieved by increasing the transformer ratio, which increases the loss of the switch tube. Too large a transformer ratio will aggravate the non-idealization of the transformer. Adding a high-voltage voltage doubler circuit to the secondary side of the transformer and a resonant circuit to the primary side of the transformer enables the switch tube in the full-bridge circuit to achieve zero voltage switching or zero current switching, reducing the loss of the switch tube and reducing the transformer ratio.

[0003] The high voltage voltage doubler circuit is composed of a rectifier branch composed of multiple diodes and capacitors. By increasing the rectifier branch, a DC voltage that is a multiple of the input voltage can be achieved. Common voltage doubler rectifier circuits are CW voltage doubler circuits and Sinker voltage doubler circuits. When the number of rectifier branches is the same, the voltage doubler capability of the CW voltage doubler circuit is lower than that of the Sinker voltage doubler circuit. The capacitor voltage in the Sinker voltage doubler circuit increases step by step. As the number of voltage doublers increases, the voltage withstand requirements for the capacitor are also getting higher and higher. When the capacitor voltage withstand value is limited, the Sinker voltage doubler circuit is not suitable for use in occasions where the output voltage is particularly high.

[0004] The present invention combines a CW voltage doubling circuit and a Sinker voltage doubling circuit, which can overcome the situation where the Sinker voltage doubling circuit is not suitable for outputting high voltage, and relatively saves cost compared with the CW voltage doubling circuit. Summary of the invention

[0005] In view of this, the present invention provides a novel high-voltage voltage doubling circuit for a DC-DC conversion circuit, which can change the voltage doubling multiple of the output voltage by increasing or decreasing the rectifier branch, has high voltage doubling capability, and saves cost.

[0006] In order to solve the above technical problems, the present invention is implemented as follows.

[0007] The invention provides a high voltage voltage doubling circuit for a DC-DC conversion circuit, comprising: an AC power input terminal, a basic voltage doubling module and an extended voltage doubling module.

[0008] The basic voltage doubler module is composed of 4 rectifier branches, and the extended voltage doubler module is composed of 2 extended rectifier branches. Each rectifier branch and each extended rectifier branch have the same structure, and are both composed of a unidirectional diode and a capacitor in series, wherein the cathode of the unidirectional diode is connected to the capacitor, the anode of the unidirectional diode serves as the first end of the rectifier branch or the extended rectifier branch, and the end of the capacitor not connected to the unidirectional diode serves as the second end of the rectifier branch or the extended rectifier branch;

[0009] In the basic voltage doubling module, the first rectifier branch is connected in forward parallel with the input terminal of the AC power supply; the second rectifier branch is connected in reverse parallel with the unidirectional diode of the first rectifier branch; the third rectifier branch is connected in reverse parallel with the unidirectional diode of the second rectifier branch; the first end of the fourth rectifier branch is connected between the unidirectional diode and the capacitor in the third rectifier branch, and the second end is connected to the positive pole of the AC power supply input terminal.

[0010] That is, in the basic voltage doubling module, the first end of the first rectifier branch, the second end of the second rectifier branch and the second end of the fourth rectifier branch are connected to the positive pole of the AC power input terminal; the second end of the first rectifier branch is connected to the negative pole of the AC power input terminal; the first end of the second rectifier branch is connected between the unidirectional diode and the capacitor in the first rectifier branch; the third rectifier branch is connected in reverse parallel with the unidirectional diode of the second rectifier branch, that is, the two unidirectional diodes are connected in positive and negative directions; the first end of the fourth rectifier branch is connected between the unidirectional diode and the capacitor in the third rectifier branch.

[0011] In the expandable voltage doubling module, the second expansion rectifier branch is connected in reverse parallel with the unidirectional diode of the first expansion rectifier branch, that is, the first end of the second expansion rectifier branch is connected to the cathode of the unidirectional diode of the first expansion rectifier branch.

[0012] The connection relationship between the basic voltage doubler module and the first-stage extended voltage doubler module is that the first extended rectifier branch and the unidirectional diode of the fourth rectifier branch are connected in reverse parallel.

[0013] According to the required voltage multiplication factor, m expansion voltage multipliers are selected for cascading, and the first-stage expansion voltage multiplier module is connected to the basic voltage multiplier module. The specific connection relationship is: the first expansion rectifier branch of the first-stage expansion voltage multiplier module and the unidirectional diode of the fourth rectifier branch are connected in reverse parallel; between the cascaded expansion voltage multipliers, the first expansion rectifier branch in the rear-stage expandable voltage multiplier module and the unidirectional diode of the second expansion rectifier branch in the front-stage expandable voltage multiplier module are connected in reverse parallel;

[0014] The voltage multiplier generated by the basic voltage multiplier module is 4; according to the required overall voltage multiplier N, the number of expandable voltage multiplier modules is selected to be m=(N-4) / 2;

[0015] The capacitor in the fourth rectifier branch and the capacitor in the second expanded rectifier branch in each expandable voltage doubler module are connected in series to supply power to the load, providing a multiple voltage of 4+2m times.

[0016] Preferably, the unidirectional diode is a Schottky diode.

[0017] Preferably, the capacitor is a tantalum capacitor.

[0018] Wherein, the AC power input terminal can be connected to the secondary side of a high-frequency transformer.

[0019] If the required voltage multiplication factor is 4, the number of the expansion voltage multiplication modules is 0.

[0020] Beneficial effects:

[0021] (1) The multiple expandable rectifier branches of the present invention can rectify the voltage peak value at the input end of the AC power supply, and the capacitors connected in parallel after rectification can provide a high-voltage DC voltage for the load. The method of rectifying and boosting the AC input by expanding multiple rectifier branches can greatly reduce the boost turns ratio of the high-frequency transformer. In the prior art, the method of only increasing the turns ratio of the high-frequency transformer and then rectifying it to achieve high DC voltage will increase the loss and noise of the transformer. The high-voltage voltage doubling circuit of the present invention can be used after the high-frequency transformer to reduce the turns ratio of the transformer while keeping the output DC high voltage unchanged.

[0022] (2) Compared with the Sinker voltage doubling circuit, the capacitor voltage in the Sinker voltage doubling circuit increases step by step. As the number of voltage doubling stages increases, the withstand voltage requirement for the last output capacitor becomes higher and higher. When the withstand voltage value of the capacitor is limited, the Sinker voltage doubling circuit is not suitable for use in occasions where the output voltage is particularly high. The present invention doubles the input voltage into multiple groups of capacitors and connects the multiple groups of capacitors in series as the output voltage, which is equivalent to allocating the withstand voltage value of the output voltage to multiple groups of capacitors, thereby reducing the withstand voltage value required for each group of output capacitors.

[0023] (3) Compared with the CW voltage doubler circuit and the Sinker voltage doubler circuit, the present invention saves costs. Under the premise of the same output high voltage, the present invention requires the least number of capacitors; under the premise of the same output voltage, the last-level capacitor of the Sinker voltage doubler circuit is the output capacitor, and other capacitors except the output capacitor are "wasted" capacitors. However, under the premise of being able to output the same voltage, the present invention reduces the "wasted" capacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of a high voltage voltage doubling circuit of the present invention;

[0025] Figure 2 Schematic diagram of the rectifier branches in the high voltage voltage doubler circuit of the present invention; (a) is a group of rectifier branches; (b) is two groups of rectifier branches;

[0026] Figure 3 is the input power supply, capacitor charging voltage and current waveform;

[0027] Figure 4 These are the working modes of the high-voltage voltage doubler circuit of the present invention in steady state; (a) is mode 1; (b) is mode 2; (c) is mode 3; and (d) is mode 4. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0029] The present invention provides a high voltage doubler circuit for a DC-DC conversion circuit, such as Figure 1 As shown, it includes a basic voltage doubling module and an expansion voltage doubling module. The basic voltage doubling module is connected to the AC power input terminal and generates a voltage doubling factor of 4; the expansion voltage doubling module generates an additional voltage doubling factor of 2. According to the required overall voltage doubling factor, the number of expandable voltage doubling modules n is selected; then the voltage doubling circuit can provide a multiple voltage of 4+2n times.

[0030] Figure 1 The present invention is a structural diagram of a high-voltage voltage doubling circuit for a DC-DC conversion circuit. As shown in the figure, the basic voltage doubling module and the expanded voltage doubling module of the present invention are composed of a diode and a capacitor. The diode has the property of unidirectional conduction. The diode and the capacitor are connected to form a rectifier branch. If this branch is connected to both ends of an AC power supply, the AC power supply can be converted into a DC power supply and stored in the capacitor under the action of the diode. Thereby achieving the purpose of rectification, if multiple groups of rectifier branches are connected to the AC power supply, the AC power supply can be rectified into multiple DC powers and stored in the capacitor. If the capacitor is connected in series to supply power to the load, the voltage doubling effect can be achieved.

[0031] The high-voltage voltage doubling circuit proposed in the present invention is composed of 2n groups of rectifier branches, and the first 4 groups of rectifier branches constitute a basic voltage doubling module. The number of the subsequent multiple groups is optional, which is called an extended rectifier branch, and every two extended rectifier branches constitute an extended voltage doubling module. The AC power supply is rectified by each rectifier branch and stored in each capacitor in the form of a DC voltage. The purpose of voltage doubling is achieved by connecting each capacitor in series, and the AC power supply is rectified and voltage doubled to supply power to the load.

[0032] like Figure 1As shown, Vin is the input end of the AC power supply, and the input AC power supply amplitude is Vm. Capacitor C1 and diode D1 form the first rectifier branch; capacitor C2 and diode D2 form the second rectifier branch; capacitor C3 and diode D3 form the third rectifier branch; capacitor C4 and diode D4 form the fourth rectifier branch. In each rectifier branch, the capacitor and diode are connected in series, the cathode of the diode is connected to the capacitor, the anode of the diode serves as the first end of the branch, and the other end of the capacitor serves as the second end of the branch.

[0033] The first rectifier branch is connected in forward parallel between the positive and negative terminals of the AC power input terminal Vin, and the positive electrode of the diode D1 is connected to the positive electrode of Vin; the second rectifier branch is connected in reverse parallel between the two terminals of the diode D1, and the positive electrode of the diode D2 is connected to the negative electrode of D1. The third rectifier branch is connected in reverse parallel between the two terminals of the diode D2, and the positive electrode of the diode D3 is connected to the negative electrode of D2; in the fourth rectifier branch, the positive electrode of the diode D4 is connected to the negative electrode of the diode D3, and the end of the capacitor C4 not connected to the diode D4 is connected to the positive electrode of the AC power input terminal Vin.

[0034] Figure 1 The figure shows the situation of multiple expansion voltage doubler modules being cascaded. In the first expansion voltage doubler module, capacitor C5 and diode D5 form the first expansion rectifier branch, capacitor C6 and diode D6 form the second expansion rectifier branch; several expansion voltage doubler modules are omitted in the middle. In the last expansion voltage doubler module shown in the figure, capacitor C2n-1 and diode D2n-1 form the first expansion rectifier branch, capacitor C2n and diode D2n form the second expansion rectifier branch.

[0035] The anode of diode D5 is connected to the cathode of diode D4, and the end of capacitor C5 not connected to the diode is connected to the anode of diode D4, thereby realizing the connection between the first-stage expansion voltage doubler module and the basic voltage doubler module. Among multiple expansion voltage doubler modules, the unidirectional diodes of the first expansion rectifier branch of the rear stage and the second expansion rectifier branch of the front stage are reversely connected in parallel. Assuming n=4, the anode of D7 is connected to the cathode of D6, and C7 is connected to the anode of D6.

[0036] The capacitor C4 in the fourth rectifier branch and the capacitors C6 . . . C2n in the second expanded rectifier branch in each expanded voltage doubler module are connected in series to supply power to the load, providing a 2n-fold voltage.

[0037] The working principle of the high voltage voltage doubling circuit of the present invention is analyzed below.

[0038] In an ideal state and without load, the circuit is transiently analyzed. If the AC power wave forms a sinusoidal form, in the first positive half cycle, the polarity of the AC power is positive at the top and negative at the bottom, the diode D1 is turned on, and the AC power charges the capacitor C1 through the diode D1. When the voltage of the capacitor C1 is equal to the peak voltage Vm of the AC power, the charging of the capacitor C1 stops. The polarity of the capacitor C1 is negative on the left and positive on the right. Figure 2 As shown in Figure (a). In the first negative half cycle, the polarity of the AC power supply is negative at the top and positive at the bottom, diode D2 is turned on, D1 is turned off, and the AC power supply charges capacitor C2 through diode D2. When V C2 =V C1 +Vm, that is, the voltage of C2 is equal to 2Vm, the polarity is negative on the left and positive on the right, and this charging stage is terminated. Figure 2 As shown in Figure (b).

[0039] In the second positive half cycle, the polarity of the AC power supply is positive at the top and negative at the bottom. The diodes D1 and D3 are turned on. The AC power supply charges the capacitors C1 and C3 through the diodes D1 and D3 respectively. When the voltage of the capacitor C1 is equal to the peak voltage Vm of the AC power supply, the capacitor V C3 =V C1 +V C2 +Vm, that is, 2Vm, stops charging capacitors C1 and C3. In the second negative half cycle, the polarity of the AC power supply is negative at the top and positive at the bottom. Diodes D2 and D4 are turned on, and diodes D1 and D3 are turned off. The AC power supply charges capacitors C2 and C4 through diodes D2 and D4. When V C4 =V C1 +V C3 +Vm, that is, the voltage of C4 is equal to 4Vm, the polarity is negative on the left and positive on the right, and this charging stage is terminated. After several cycles, the circuit is in a stable state, and the voltages of capacitors C1, C2, C3, C4, C5...C2n are Vm, 2Vm, 2Vm, 4Vm, 2Vm...2Vm respectively. If capacitors C4...C2n are connected in series to supply power to the load, multiple voltages can be provided to the load, achieving the purpose of voltage doubling rectification.

[0040] In steady state, within an AC power cycle, the high voltage doubler circuit can be divided into four operating modes according to the on and off time of the diode, such as Figure 3 As shown, the time period t1-t2 is mode 1, the time period t2-t3 is mode 2, the time period t3-t4 is mode 3, and the time period t4-t5 is mode 4. The equivalent circuit in each mode is as follows Figure 4 As shown. In mode 1 and mode 3, the diode is turned on, the capacitor is in a charging state, and the voltage of the capacitor is in a rising state. In mode 2 and mode 4, no diode is turned on. The detailed state analysis in each mode is as follows:

[0041] Mode 1[t1-t2]: Figure 4As shown in (a), the power supply is in the positive half cycle, with the polarity of positive at the top and negative at the bottom. In this mode, diodes D1, D3...D2n-1 are turned on, and D2, D4...D2n are turned off. Capacitors C1, C3...C2n-1 are in a charged state and the voltage gradually increases. When the voltage of capacitors D1, D3...D2n-1 increases to Vm, 2Vm...2Vm respectively, this mode period ends and enters mode 2. In this mode, C4, C6...C2n are connected in series to supply power to the load.

[0042] Mode 2[t2-t3]: Figure 4 As shown in (b), the diodes are all in the off state at this stage. In this mode, C4, C6...C2n are connected in series to supply power to the load.

[0043] Mode 3[t3-t4]: Figure 4 As shown in (c), the power supply is in the negative half cycle, and the power supply polarity is negative at the top and positive at the bottom. In this mode, D2, D4...D 2n Conducting, diodes D1, D3...D 2n-1 Turn off, capacitors C2, C4...C 2n In the charged state, the voltage gradually increases. When the capacitors C2, C4...C 2n When the voltage rises to 4Vm, 2Vm...2Vm respectively, this mode time period ends and enters mode 4. In this mode, C4, C6...C2n are connected in series to supply power to the load.

[0044] Mode 4 [t4-t5]: Figure 4 As shown in (d), mode 4 is similar to mode 2, and the diodes are all in the off state. In this mode, C4, C6...C2n are connected in series to supply power to the load.

[0045] From the above analysis, it can be seen that when the peak voltage of the input AC power supply is Vm, the input power supply can be rectified and doubled by this high-voltage voltage doubler circuit. When n=2, the capacitor C4 can be charged to 4Vm when no-load. If C4 supplies power to the load, it can provide four times the AC power supply voltage. When n=3, the capacitor C4 can be charged to 4Vm when no-load, and the capacitor C6 can be charged to 2Vm. If C4 and C6 supply power to the load, it can provide six times the peak voltage of the AC power supply, that is, 6Vm. When n=4, the capacitor C4 can be charged to 4Vm when no-load, the capacitor C6 can be charged to 2Vm, and the capacitor C8 can be charged to 2Vm. If C4, C6 and C8 supply power to the load, it can provide eight times the peak voltage of the AC power supply, that is, 8Vm. By analogy, when n≥2, when no-load, C4...C2n are charged to 4Vm...2Vm. If C4...C2n supply power to the load, it can provide 2n times the peak voltage of the AC power supply, that is, (2n)Vm.

[0046] In the present invention, the diode used may be a Schottky diode, and the capacitor used may be a tantalum capacitor. The capacitor and the diode form a rectifier branch circuit structure, and the value of the output DC high voltage can be changed by increasing or decreasing the rectifier branch according to the need of outputting DC high voltage.

[0047] The AC power input terminal of the present invention can be connected to the secondary side of the high-frequency transformer, so as to realize the rectification and voltage doubling of the output voltage of the high-frequency transformer. In the prior art, the method of only increasing the turns ratio of the high-frequency transformer and then rectifying to obtain the DC high voltage will increase the loss and noise of the transformer. The high-voltage voltage doubling circuit of the present invention can be used after the high-frequency transformer to reduce the turns ratio of the transformer while keeping the output DC high voltage unchanged.

[0048] The above specific embodiments only describe the design principle of the present invention. The shapes and names of the components in the description may be different and are not limited. Therefore, those skilled in the art in the field of the present invention may modify or replace the technical solutions recorded in the above embodiments; and these modifications and replacements do not deviate from the creative purpose and technical solutions of the present invention and should all fall within the protection scope of the present invention.

Claims

1. A high voltage doubler circuit for a DC-DC conversion circuit, characterized in that: It includes a basic voltage doubler module composed of four rectifier branches and an extended voltage doubler module composed of two extended rectifier branches; the rectifier branch and the extended rectifier branch are both composed of a unidirectional diode and a capacitor connected in series; the positive electrode of the unidirectional diode is used as the first end of the branch, and the end of the capacitor not connected to the unidirectional diode is used as the second end of the branch; In the basic voltage doubling module, the first rectifying branch is connected in forward parallel with the input terminal of the AC power supply; the second rectifying branch is connected in reverse parallel with the unidirectional diode of the first rectifying branch; The third rectifying branch is connected in reverse parallel with the unidirectional diode of the second rectifying branch; the first end of the fourth rectifying branch is connected between the unidirectional diode and the capacitor in the third rectifying branch, and the second end is connected to the positive electrode of the AC power input terminal; In the expanded voltage doubling module, the second expanded rectifying branch is connected in reverse parallel with the unidirectional diode of the first expanded rectifying branch; According to the required voltage multiplication multiple, m expansion voltage multiplication modules are selected for cascade connection, the first expansion rectifier branch of the rear stage is connected in reverse parallel with the unidirectional diode of the second expansion rectifier branch of the front stage; the first expansion rectifier branch of the first stage expansion voltage multiplication module is connected in reverse parallel with the unidirectional diode of the fourth rectifier branch; The capacitor in the fourth rectifier branch and the capacitor in the second expanded rectifier branch in each expanded voltage doubler module are connected in series to supply power to the load, providing a voltage doubler of 4+2m.

2. The high voltage doubler circuit according to claim 1, characterized in that: The unidirectional diode is a Schottky diode.

3. The high voltage doubler circuit according to claim 1, characterized in that: The capacitor is a tantalum capacitor.

4. The high voltage doubler circuit according to claim 1, characterized in that: If the required voltage multiplication factor is 4, the number of the expansion voltage multiplication modules is 0.

5. The high voltage doubler circuit according to any one of claims 1 to 4, characterized in that: The AC power input terminal is connected to the secondary side of the high-frequency transformer.

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