CN-116155106-B - Isolated bipolar output self-equalizing DC-DC converter

Abstract

The isolated bipolar output self-equalizing DC-DC converter comprises a forward converter and a bipolar equalizing unit, wherein the forward converter comprises a direct current input source u in , a power switch S 1 , a reset inductor L p1 , a transformer T, a reset diode D p1 , a rectifying diode D 1 , a freewheel diode D 2 , an inductor L 1 and an output capacitor C 1 , and the bipolar equalizing unit comprises a rectifying diode D 3 , a freewheel diode D 4 , an inductor L 2 , an inductor L 3 , an output capacitor C 2 and an equalizing capacitor C p . The invention can effectively and greatly reduce the problem of unbalanced voltage caused by the cross adjustment rate when the traditional forward converter outputs the bipolar voltage, reduce the voltage deviation, has simple circuit control, realizes the automatic voltage equalizing of the bipolar output through the bipolar voltage equalizing unit, does not need complex sampling and control algorithm, has lower design and realization difficulty of a control system, and is suitable for occasions needing bipolar voltage power supply.

Inventors

• ZHU BINXIN
• YANG YUJIN
• WANG KAIHONG
• ZHOU LIJUAN
• ZHENG ZHENYU

Assignees

• 三峡大学

Dates

Publication Date

20260508

Application Date

20221214

Claims (4)

1. 1. The isolated bipolar output self-equalizing DC-DC converter is characterized by comprising a forward converter and a bipolar equalizing unit; The forward converter comprises a direct current input source u in , a power switch S 1 , a reset inductor L p1 , a transformer T, a reset diode D p1 , a rectifier diode D 1 , a freewheel diode D 2 , an inductor L 1 and an output capacitor C 1 , and the connection modes are as follows: The positive electrode of the direct current input source u in is respectively connected with the upper end of the primary winding L p of the transformer T and one end of the reset inductor L p1 ; The lower end of the primary winding L p of the transformer T is connected with the drain electrode of the power switch S 1 ; The anode of the reset diode D p1 is respectively connected with the cathode of the direct-current input source u in and the source of the power switch S 1 , and the grid electrode of the power switch S 1 is connected with the controller; The other end of the reset inductor L p1 is connected with the cathode of the reset diode D p1 ; The upper end of a secondary winding L s of the transformer T is connected with the anode of a rectifier diode D 1 ; the cathode of the rectifying diode D 1 is respectively connected with the cathode of the freewheeling diode D 2 and one end of the inductor L 1 ; the other end of the inductor L 1 is connected with one end of the output capacitor C 1 ; The other end of the output capacitor C 1 is respectively connected with the anode of the freewheeling diode D 2 and the lower end of the secondary winding L s of the transformer T; The bipolar voltage equalizing unit comprises a rectifying diode D 3 , a freewheeling diode D 4 , an inductor L 2 , an inductor L 3 , an output capacitor C 2 and a voltage equalizing capacitor C p , wherein the connection modes are as follows: The other end of the equalizing capacitor C p is respectively connected with the anode of the rectifying diode D 3 and one end of the inductor L 2 ; The cathode of the rectifying diode D 3 is respectively connected with the cathode of the freewheeling diode D 4 and one end of the inductor L 3 ; The other end of the inductor L 3 is connected with one end of the output capacitor C 2 ; The other end of the output capacitor C 2 is respectively connected with the anode of the freewheeling diode D 4 and the other end of the inductor L 2 ; The connection relation between the forward converter and the bipolar voltage equalizing unit is as follows: The upper end of the secondary winding L s of the transformer T is connected with one end of the voltage-sharing capacitor C p , and one end of the output capacitor C 2 is connected with the other end of the output capacitor C 1 ; both ends of the load R L1 are respectively connected with one end and the other end of the output capacitor C 1 , and both ends of the load R L2 are respectively connected with one end and the other end of the output capacitor C 2 .
2. 2. The isolated bipolar output self-equalizing DC-DC converter of claim 1 wherein said power switch S 1 has a gate connected to a controller with a duty cycle that can vary from 0 to 1.
3. 3. The isolated bipolar output self-equalizing DC-DC converter according to claim 1, wherein when the power switch S 1 is turned on, the rectifying diode D 1 and the rectifying diode D 3 are turned on, the reset diode D p1 , the freewheel diode D 2 and the freewheel diode D 4 are turned off, the input voltage is applied to the primary winding of the transformer T, energy is transmitted to the secondary winding of the transformer T, the inductor L 1 and the left inductor L 2 , the right inductor L 3 and the equalizing capacitor C p in the bipolar equalizing unit are charged, and the output capacitor C 1 and the output capacitor C 2 are discharged; When the power switch S 1 is turned off, the rectifying diode D 1 and the rectifying diode D 3 are turned off, the reset diode D p1 , the freewheel diode D 2 and the freewheel diode D 4 are turned on, the inductor L 1 and the left inductor L 2 and the right inductor L 3 in the bipolar equalizing unit discharge through the freewheel diode D 2 and the freewheel diode D 4 to convert stored magnetic energy into electric energy, the equalizing capacitor C p discharges, and the output capacitor C 1 and the output capacitor C 2 charge.
4. 4. The bipolar output self-equalizing method of an inverter according to claim 1 or 2, characterized in that: In the whole switching period, the average voltage of the secondary winding L s of the transformer T, the inductor L 1 and the left inductor L 2 and the right inductor L 3 in the bipolar voltage-equalizing unit is 0, and the voltage u cp of the voltage-equalizing capacitor C p is equal to the output voltage u o2 according to the L s →C p →L 2 →C 2 →L s loop KVL principle; During the on period of the switch, the rectifying diode D 1 and the rectifying diode D 3 are conducted, and the equalizing capacitor C p is connected with the output capacitor C 1 in parallel through a loop C p →D 1 →L 1 →C 1 →L 3 →D 3 →C p ; During the switch turn-off period, the freewheeling diode D 2 and the freewheeling diode D 4 are turned on, the voltage-sharing capacitor C p is connected in parallel with the output capacitor C 1 through the loop C p →L s →D 2 →L 1 →C 1 →L 3 →D 4 →L 2 →C p , so that the voltage u cp of the voltage-sharing capacitor C p in the whole period is equal to the output voltage u o1 , and when the capacitor C p is large enough, the output voltage of the forward converter is equal to the output voltage of the bipolar voltage-sharing unit, and the self-voltage sharing of bipolar output is realized.

Description

Isolated bipolar output self-equalizing DC-DC converter Technical Field The invention relates to a bipolar converter, in particular to an isolated bipolar output self-equalizing DC-DC converter. Background In the prior art, the transient control characteristic of the output voltage of the single-ended forward converter and the load characteristic of the output voltage are relatively good, so that the operation is relatively stable, the output voltage is not easy to shake, and the single-ended forward converter is often used in occasions with relatively high requirements on the output voltage parameters. The bipolar single-ended forward converter can realize that one path of output fails and the other path of output can normally work, and can provide three voltage levels including two symmetrical positive and negative voltages and the grounding current is close to zero when the bipolar single-ended forward converter normally works. However, a conventional bipolar single-ended forward converter, for example, patent document CN111245243 a discloses a "multiple-output single-tube forward converter", which adds a series capacitor to achieve isolation between the forward switching power supply transformer output and diode rectification, and in order to achieve multiple-channel output, the transformer output may be followed by a multiple-capacitor isolated output circuit. The input AC power supply is modulated by PWM switch to provide PWM pulse signal energy to the transformer, the transformer converts the voltage VIN to generate low voltage AC pulse power supply signal in the secondary coil, the signal passes through N paths of output capacitors, reaches the energy storage inductors and the free wheeling diode of each channel, and then becomes DC power supply output of each channel through the energy storage inductors, thus realizing the output of the multi-channel power supply. When each path of load is unbalanced, the output voltage is related to the load size, and the loop output voltage which does not participate in feedback cannot reach balance, so that the cross adjustment rate is poor, and the method is difficult to be qualified in occasions with higher requirements on multiple paths of output voltages. Disclosure of Invention In order to solve the problem that the output voltage of the traditional bipolar output forward converter is easily influenced by load disturbance to generate deviation, the invention provides an isolated bipolar output self-equalizing DC-DC converter based on a basic forward converter. Compared with the traditional converter adopting the double-winding output, the energy distribution imbalance problem caused by load disturbance is avoided. The technical scheme adopted by the invention is as follows: An isolated bipolar output self-equalizing DC-DC converter comprises a forward converter and a bipolar equalizing unit; The forward converter comprises a direct current input source u in, a power switch S 1, a reset inductor L p1, a transformer T, a reset diode D p1, a rectifier diode D 1, a freewheel diode D 2, an inductor L 1 and an output capacitor C 1, and the connection modes are as follows: The positive electrode of the input power supply u in is respectively connected with the upper end of the primary winding L p of the transformer T and one end of the reset inductor L p1; The other end of the primary winding L p of the transformer T is connected with the cathode of the reset diode D p1; the anode of the reset diode D p1 is respectively connected with the cathode of the input power supply u in and the source of the power switch S 1; The upper end of a secondary winding L S of the transformer T is connected with the anode of a rectifier diode D 1; the cathode of the rectifying diode D 1 is respectively connected with the cathode of the freewheeling diode D 2 and one end of the inductor L 1; the other end of the inductor L 1 is connected with one end of the output capacitor C 1; The other end of the output capacitor C 1 is respectively connected with the anode of the freewheeling diode D 2 and the lower end of the secondary winding L S of the transformer T; The bipolar voltage equalizing unit comprises a rectifying diode D 3, a freewheeling diode D 4, an inductor L 2, an inductor L 3, an output capacitor C 2 and a voltage equalizing capacitor C p. The connection form is as follows: The other end of the equalizing capacitor C p is respectively connected with the anode of the rectifying diode D 3 and one end of the inductor L 2; The cathode of the rectifying diode D 3 is respectively connected with the cathode of the freewheeling diode D 4 and one end of the inductor L 3; The other end of the inductor L 3 is connected with one end of the output capacitor C 2; The other end of the output capacitor C 2 is respectively connected with the anode of the freewheeling diode D 4 and the other end of the inductor L 2; The connection relation between the forward converter and the bipolar voltage