DC voltage converter with active clamping

Abstract

A DC voltage converter with active clamping comprises a transformer, a first secondary winding of which is connected to a filter capacitor via a series diode, and another secondary winding of which is connected at its end to a start of the first secondary winding and to an input of an L-shaped LC filter via a series diode, an output capacitor of the filter is connected in series with a filter capacitor. The input end of the L-shaped LC filter is connected to a common connection point of the filter capacitor through a shunt diode, and a load is connected with the common connection point in parallel. The technical effect is that the dynamic loss is reduced.

Description

Technical Field

[0001] This invention relates to electrical engineering, and in particular to DC-DC converters, which can be used in secondary power supply systems to convert, regulate and stabilize DC output voltages that are electrically isolated from DC input voltages, and reduce dynamic losses. Background Technology

[0002] DC-DC converters with active clamping are known [1].

[0003] A known drawback of DC-DC converters with active clamping is the lack of the ability to turn the power switch to zero current, which leads to increased dynamic losses when the power switch is on, and the trapezoidal current through the power switch, which results in additional losses when the power switch is on and dynamic losses when it is off.

[0004] The device most technically similar to the proposed device is a DC-DC converter with active clamping given in [1], which includes a primary winding of a transformer connected to the terminal of the input DC voltage source via a power adjustment key, and a clamping element consisting of a series capacitor and an additional switch connected in parallel. The transformer is used to provide electrical isolation and obtain the desired DC output voltage. The secondary winding of the transformer is connected to the input of an L-type LC filter via a rectifier diode, and the load is connected to the output of the filter. Summary of the Invention

[0005] The purpose of this invention is to eliminate the above-mentioned disadvantages.

[0006] The objective is achieved in a DC-DC converter with active clamping, where the primary winding of the transformer is connected to the terminal of the input DC voltage source via a power adjustment switch, and a clamping element is connected in parallel thereto. The two secondary windings of the transformer operate simultaneously during the time interval of the power adjustment switch being turned on. The first secondary winding is connected to the first filter capacitor via a rectifier diode, and the second secondary winding is connected to the input of an L-type LC filter via a rectifier diode. Its output capacitor is connected in series with the first filter capacitor. The load is connected in parallel across the two series capacitors. The input of the L-type LC filter is connected to the common connection point of the two filter capacitors via a shunt rectifier diode. Attached Figure Description

[0007] Figure 1 , Figure 2 and Figure 3 The diagram shows a basic circuit diagram of the proposed DC-DC converter embodiment with active clamping. Figure 1 The diagram shown is a basic circuit diagram of a DC-DC voltage converter with active clamping. Figure 2The diagram shows the basic circuit of a DC-DC voltage converter with active clamping that incorporates a small amount of linear inductance in the circuit. Figure 3 The diagram shows the basic circuit of a DC-DC voltage converter with active clamping that incorporates a third additional secondary winding in the circuit. Detailed Implementation

[0008] in( Figure 1 The primary winding 1 of transformer 2 is connected to the positive terminal of the input DC voltage source, and the end of the primary winding 1 is connected to the negative terminal of the input DC voltage source via a power control switch 3 implemented as a MOSFET field-effect transistor. A clamping element, implemented as a MOSFET field-effect transistor, is connected in parallel with the primary winding 1 of transformer 2 and consists of a series capacitor 4 and an additional switch 5. The anode of rectifier diode 7 is connected to the beginning of the secondary winding 6 of transformer 2, its cathode is connected to one terminal of capacitor 8, and its second terminal is connected to the end of winding 6. The beginning of winding 6 is connected to the end of winding 9, its beginning is connected to the anode of diode 10, its cathode is connected to the inductor 11 of the L-shaped LC filter, and its second terminal is connected to capacitor 12, which is the output capacitor of the LC filter, connected in series with capacitor 8, and with load 13 connected in parallel. The anode of shunt diode 14 is connected to the common connection point of capacitors 8 and 12, and its cathode is connected to the common connection point of inductor 11 and rectifier diode 10. The control electrodes of switches 3 and 5 are connected to pulse width controller 15.

[0009] We will consider the operating principle of the proposed DC-DC converter with active clamping based on the following assumptions: ideal key elements, stable operating mode, and continuous change of magnetic flux in the transformer core. We use... D This indicates the conduction state of key 3 relative to the period. T The duration. At this time. DT With switch 3 closed, energy is transferred to the load through the forward-biased rectifier diode 7 and the secondary winding 6. At this time, due to the time interval... DT and (1-D)T Charge balance at time, current I L / D The current flows through rectifier diode 7, where I L Given the load current, the voltage across capacitor 8 is given by the expression n 1 V IN Confirmed, among which n 1 represents the turns ratio of winding 6 to winding 1.

[0010] However, while energy is transferred to the load through secondary winding 6 and diode 7, energy is simultaneously transferred to the input of the L-shaped LC filter through secondary winding 9 and forward bias diode 10, the output capacitor 12 of which is connected in series with capacitor 8. Due to this energy transfer to the load, a voltage equal to [missing value] is formed on capacitor 12. n 2 V IN D The voltage, of which n 2 is the turns ratio of winding 9 to winding 1.

[0011] Since energy is simultaneously transferred to the load through the secondary windings 6 and 9 of transformer 2, the differential current ( I L / D – I L The current flowing through diode 7 is [value missing]. I L (1-D) / D This value is significantly smaller than I L / D Therefore, the losses in diode 7 and the voltage ripple in capacitor 8 are relatively small. Output voltage （n 1 V IN +n 2 V IN D） It equals the sum of the voltages across capacitors 8 and 12.

[0012] After switch 3 is closed, the additional switch 5 of the clamping element is opened, and the voltage on winding 1 of transformer 2 is fixed to the voltage on capacitor 4, which is equal to... V IN D / (1-D) The voltage polarity of all windings of transformer 2 is reversed, while the voltage of the primary winding 1 of transformer 2 is fixed. Rectifier diodes 7 and 10 are locked, and shunt diode 14 is turned on, switching the current of inductor 11 to itself. At the same time, the magnetizing current of transformer 2 is switched to its included auxiliary switch 5 and capacitor 4, which together form a clamping element.

[0013] When in time interval DT During the process of transferring energy to the output circuit, when switch 3 is in the on state, two processes occur: one of which involves the transformer 2 transferring energy from the input voltage source along the primary winding 1. V IN Magnetization and the voltage across capacitor 8 along secondary winding 6 n 1 V INMagnetization is also related. As a result of this magnetization, the current increases linearly in proportion. In the secondary winding 6, this increase in current causes a decrease in the current flowing through the rectifier diode 7, which is in a conducting state during this time interval. The linear decrease in the current flowing through the rectifier diode 7 is transferred to the primary winding 1 and compensates for the linear increase in the current flowing through the primary winding 1, which causes the current flowing through the regulating key 3 to become rectangular.

[0014] The second process is related to the timing of turning on the power control switch 3. When the power control switch 3 is turned on and the additional switch 5 of the clamping element is turned off, the voltage polarity on the winding of transformer 2 reverses, and the rectifier diode 7 conducts. However, there is a time delay between the turn-on of the rectifier diode 7 and the turn-on of the power regulation switch 3. This delay is due to the finite time of voltage change on the winding of transformer 2 and the fact that the positive potential at the cathode of the rectifier diode 7 is equal to n1. V IN Caused by.

[0015] The time delay in energy transfer to the output circuit when the power regulating switch 3 is turned on causes the leading edges of the current and voltage on the power regulating switch 3 to separate, thereby reducing dynamic losses when turned on.

[0016] Introduce a small linear inductor of the Nahen class 16 ( Figure 2 It is connected in series with the secondary winding 6, which enhances the effect of forming a zero current value when the power control switch 3 is turned on.

[0017] Introducing an additional third-stage winding 17 ( Figure 3 Its starting point is connected to the common connection point of capacitors 8 and 12, and its ending point is connected to the anode of shunt diode 14. The cathode of shunt diode 14 is connected to the common connection point of diode 10 and inductor 11, which can extend the control range to (n 1 V IN +(n 2+ n 3 )V IN D) The value of , where n 3 is the turns ratio of winding 17 to winding 1.

[0018] As mentioned above, the current flowing through the power regulating switch 3 is essentially rectangular, which reduces the losses of the power regulating switch 3 when it is turned off, since the switch turns off at a lower current.

[0019] Therefore, compared with known devices, the proposed DC voltage converter with active clamp can form a constant output voltage from a constant input voltage, while reducing dynamic losses and providing the ability to turn the power switch to zero current value, thereby reducing dynamic losses when the power switch is turned on, as well as losses caused by the rectangularity of the current in the on state when the power switch is turned off.

[0020] 1.AsNo.892614 (CCCP)MKI H02M3 / 335 "Single-stroke constant pressure regulator" AG Polikapov, EF Sergienko.

Claims

1. A DC-DC voltage converter with active clamping, comprising a transformer, wherein the primary winding is connected to the terminals of a DC input voltage source via a power regulating switch, and a clamping element is connected in parallel, consisting of a series capacitor and an additional switch, and the secondary winding of the transformer has a rectifier diode connected to an L-shaped LC filter, characterized in that, Its primary winding is connected to the first filter capacitor via a series diode, the secondary winding is connected at its end to the start of the first filter capacitor, and is connected to the input of the L-shaped LC filter via a series diode. The output capacitor of the filter is connected in series with the first filter capacitor, and the input of the L-shaped LC filter is connected to the common connection point of the filter capacitor via a parallel diode. The load is connected in parallel with the common connection point.

2. The DC-DC voltage converter with active clamping according to claim 1, characterized in that, The linear inductor is connected in series with the primary winding of the transformer.

3. The DC-DC voltage converter with active clamping according to claim 1, characterized in that, A third secondary winding of the transformer is introduced, with its end connected to the anode of the shunt diode and its beginning connected to the common connection point of the capacitor connected in parallel with the load.

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