Magnetically coupled forward-flyback single-step DC converter
The magnetically coupled forward-flyback single-ended DC/DC converter addresses inefficiencies by using a single magnetic element, reducing power losses through controlled energy transfer and rectangular current waveforms.
Patent Information
- Authority / Receiving Office
- RU · RU
- Patent Type
- Patents
- Current Assignee / Owner
- OBSHCHESTVO S OGRANICHENNOI OTVETSTVENNOSTIU INPUT TRANSFORMEISHN AUTPUT KORPOREISHN
- Filing Date
- 2026-02-22
- Publication Date
- 2026-07-10
AI Technical Summary
Existing single-ended DC/DC converters require two magnetic elements, leading to inefficiencies and increased power losses.
A magnetically coupled forward-flyback single-ended DC/DC converter uses a single magnetic element, employing a transformer with a clamping circuit and rectifier diodes to transfer energy forward and reverse, minimizing power losses through controlled energy transfer.
Reduces power losses by using a single magnetic element, achieving efficient energy transfer with reduced dynamic losses and rectangular current waveforms.
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Abstract
Description
[0001] The invention relates to electrical engineering, in particular to single-ended DC voltage converters, and can be used in secondary power supply systems for converting, regulating and stabilizing the level of a DC output voltage galvanically isolated from the input DC voltage.
[0002] Single-ended DC / DC converters with galvanic separation of the output DC voltage from the input DC voltage are known [1].
[0003] The disadvantage of known single-ended DC to DC output converters is the use of two magnetic elements.
[0004] The closest in technical essence to the proposed device is a single-ended DC voltage converter with energy transfer to the output circuit in forward motion [1], containing a primary winding of a transformer connected through a controlled key to the terminals of a capacitor, and through a rectifier diode and linear inductance to an input source of DC voltage, and a secondary winding of a transformer connected through a rectifier diode to a capacitive filter, in parallel to which a load is connected.
[0005] The disadvantages of this converter are that it uses two magnetic elements.
[0006] The purpose of the invention is to generate the required level of constant output voltage from a constant input voltage using a single magnetic element.
[0007] The stated objective is achieved by the fact that in the magnetically coupled forward-flyback single-ended DC / DC converter, the beginning of the primary winding 1 of the transformer 2 is connected to the positive pole of the first capacitor 3, and the end of the primary winding 1 is connected through the regulating key 4 to its negative pole and the negative pole of the input DC voltage source. A clamping element is connected in parallel to the primary winding 1 of the transformer 2, consisting of a rectifier diode 5 and a second capacitor 6 connected in series, connected with the cathode of the diode 5 to the positive pole of the first capacitor 3, and the anode to the first pole of the second capacitor 6, the second pole of which is connected to the common connection point of the end of the primary winding 1 with the regulating key 4.The common connection point of the anode of the rectifier diode 5 with the second capacitor 6 is connected to the end of the second primary winding 7, the beginning of which is connected to the positive pole of the input DC voltage source. The anode of the rectifier diode 9 is connected to the beginning of the secondary winding 8 of the transformer 2, the cathode of which is connected to one of the terminals of the filter capacitor 10 with a parallel-connected load 11, the second terminal of which is connected to the end of the winding 8.
[0008] Fig. 1 shows the basic electrical circuit diagram of a magnetically coupled forward-flyback single-ended DC / DC converter.
[0009] In it (Fig. 1), the beginning of the primary winding 1 of the transformer 2 is connected to the positive pole of the first capacitor 3, and the end of the primary winding 1 through the regulating key 4 with its negative pole and the negative pole of the input DC voltage source. A clamping element is connected in parallel to the primary winding 1 of the transformer 2, consisting of a rectifier diode 5 and a second capacitor 6 connected in series, connected with the cathode of the diode 5 to the positive pole of the first capacitor 3, and the anode to the first pole of the second capacitor 6, the second pole of which is connected to the common connection point of the end of the primary winding 1 with the regulating key 4. The common connection point of the anode of the rectifier diode 5 with the second capacitor 6 is connected to the end of the second primary winding 7, the beginning of which is connected to the positive pole of the input DC voltage source.The anode of the rectifier diode 9 is connected to the beginning of the secondary winding 8 of the transformer 2, the cathode of which is connected to one of the terminals of the filter capacitor 10 with a parallel-connected load 11, the second terminal of which is connected to the end of the winding 8.
[0010] We will consider the operating principle of a magnetically coupled forward-flyback single-ended DC / DC converter based on the assumption of ideal key elements, steady-state operating mode, and continuous change in magnetic flux in the core of transformer 2.
[0011] Let us denote by D the duration of the on state of switch 4 relative to the period T. In this case, at the stage of the closed state DT of switch 4, magnetic energy accumulates in the core of transformer 2 from the input DC voltage source through the second primary winding 7 and the second capacitor 6 through the regulating switch 4, while capacitor 6 is discharged and through the first primary winding 1 from the first capacitor 3, which is also discharged. At the same time, energy is transferred through the secondary winding 8 to load 11 through the forward-biased rectifier diode 9. In this case, due to the charge balance at time intervals DT and (1-D)T of capacitor 10, current I flows through rectifier diode 9 L / D, where I L - load current, and the voltage on the capacitor 10 is determined by the expression nV IN (1-D) / (1-2D), where n is the ratio of turns of winding 8 to windings 1, 7.
[0012] After turning off key 4, over the time interval (1-D)T, the voltage on the windings of transformer 2 changes sign, and on windings 1, 7, due to the action of the clamping circuit, voltage V is established. IN D / (1-2D) equal to the voltage on capacitor 6, as a result of which the magnetic properties of transformer 2 are restored and capacitor 6 is charged, which is transformed into the output circuit via secondary winding 8 and rectifier diode 12, as a result of which voltage V is established on filter capacitor 11. IN D / (1-2D), which in sum with the voltage on the capacitor 10 forms an output voltage on the load equal to nV IN / (1-2D). At the same time, through the included rectifier diode 5, energy is extracted through the second winding in capacitor 3 and its charge, as a result of which a voltage of V is established on it. IN (1-D) / (1-2D).
[0013] When energy is transferred to the output circuit during the time interval DT, when switch 4 is on, two processes occur: one of which is associated with the simultaneous magnetization of transformer 2 via primary windings 1, 7 from the voltage on capacitor 3 and the primary source of constant input voltage via winding 7 and capacitor 6, and via secondary winding 8 from the voltage on capacitor 10. As a result of these magnetizations, the currents increase proportionally and linearly. In secondary winding 8, the increase in this current leads to a decrease in the current through rectifier diode 9, which is in the conducting state during this time interval. The linear decrease in current through rectifier diode 9 is transformed into primary windings 1, 7 and compensates for the linear increase in current through primary windings 1, 7, which leads to a rectangular current waveform through regulating switch 4.
[0014] The second process is associated with the moment of turning on the regulating switch 4. When turning on the regulating switch 4, a polarity reversal of the voltage on the transformer windings occurs and the rectifier diode 9 is turned on. However, the turning on of the rectifier diode 9 occurs with a time delay in relation to the moment of turning on the regulating switch 4. This delay is due to the finite time of voltage change on the windings of transformer 2 and the positive potential on the cathode of the rectifier diode 9 equal to V IN (1-D) / (1-2D).
[0015] The time delay in energy transfer to the output circuit when regulating switch 4 is turned on leads to the separation of the current and voltage fronts on regulating switch 4 and a reduction in dynamic losses when it is turned on.
[0016] As noted above, the current through the regulating switch 4 is rectangular in nature, which reduces losses on the regulating switch 4 when it is turned off, since the switch is turned off at a lower current.
[0017] Thus, the proposed magnetically coupled forward-flyback single-ended DC / DC converter, in comparison with the known device, uses one magnetic element, allows energy to be transferred to the load on the forward and reverse stroke when using one magnetic element and, due to the specificity of energy transfer to the output circuit in the form of a voltage pulse, to form a time delay in the energy transfer to the output circuit when the regulating switch 4 is turned on and thereby spread the increase in current through the regulating switch and the voltage drop, which significantly reduces power losses on the switch when it is turned on, and the rectangular shape of the current flowing through switch 4 reduces losses on it when it is turned off.
[0018] 1. Russian Federation Patent for Invention No. 2837260 with priority dated October 4, 2024.
Claims
A magnetically coupled forward-flyback single-ended DC / DC converter comprising a transformer having a primary winding, the end of which is connected through a controlled switch to one pole of a first capacitor, the second pole of which is connected to a common connection point of the beginning of the primary winding and the cathode of a rectifier diode, the anode of which is connected through a linear inductance to an input DC voltage source, a secondary winding connected through a rectifier diode to the output terminals of a filter capacitor, characterized in that a clamping element is connected in parallel to the first primary winding of the transformer, composed of a rectifier diode with a second capacitor connected in series, connected in such a way that one pole of the second capacitor is connected to the end of the first primary winding, and the other to a common connection point of the anode of the rectifier diode with the end of the second primary winding,the beginning of which is connected to the positive pole of the constant input voltage source, while the secondary winding of the transformer is connected at its beginning to the anode of the first rectifier diode, the cathode of which is connected to the first terminal of the filter capacitor, the second terminal of which is connected to the end of the secondary winding, a second filter capacitor is connected in series with the first filter capacitor, the second terminal of which is connected to the anode of the second rectifier diode, the cathode of which is connected to the beginning of the secondary winding, a load is connected in parallel to the two series-connected filter capacitors.