Isolated bipolar output self-voltage-sharing dc-dc converter

Abstract

An isolated bipolar output self-voltage balancing DC-DC converter, the converter comprising a forward converter, a bipolar voltage balancing unit; the forward converter comprises a DC input source u in , a power switch S1, a reset inductor L p1 , a transformer T, a reset diode D p1 , a rectifier diode D1, a freewheeling diode D2, an inductor L 1, an output capacitor C 1; the bipolar voltage balancing unit comprises a rectifier diode D3, a freewheeling diode D4, an inductor L 2, an inductor L 3, an output capacitor C 2, a voltage balancing capacitor C p The application can effectively reduce the voltage imbalance problem caused by cross regulation ratio of the traditional forward converter in bipolar output, reduce voltage deviation, and the circuit control is simple, the automatic voltage balancing of the bipolar output is realized through the bipolar voltage balancing unit, without complex sampling and control algorithm, the control system design and implementation difficulty is low, and the application is suitable for the occasions requiring bipolar voltage power supply.

Description

Technical Field

[0001] This invention relates to a bipolar converter, specifically to an isolated bipolar output self-equalizing DC-DC converter. Background Technology

[0002] In existing technologies, single-ended forward converters exhibit relatively good transient control characteristics and output voltage load characteristics, resulting in stable operation and less output voltage fluctuation. They are frequently used in applications with stringent output voltage parameter requirements. Specifically, bipolar single-ended forward converters can ensure normal operation even if one output fails; furthermore, during normal operation, they can provide three voltage levels, including two symmetrical positive and negative voltages, with near-zero ground current. Due to these characteristics, bipolar single-ended forward converters are widely used in data centers and DC microgrids, offering greater flexibility, reliability, and efficiency.

[0003] However, traditional bipolar single-ended forward converters, such as the "multi-output single-transistor forward converter" disclosed in patent document CN111245243 A, add a series capacitor between the output of the forward switching power supply transformer and the diode rectification to achieve isolation. To achieve multi-channel output, multiple capacitor-isolated output circuits can be connected after the transformer output. This achieves multi-channel output. The input AC power supply voltage VIN, after rectification and filtering, is modulated by a PWM switch to provide PWM pulse signal energy to the transformer. After conversion by the transformer, a low-voltage AC pulse power signal is generated in the secondary coil. This signal passes through N output capacitors and reaches the energy storage inductors and freewheeling diodes of each channel. Then, it is converted into DC power output for each channel through the energy storage inductors, thus achieving multi-channel power output. When the load is unbalanced in each channel, the output voltage is related to the load size. The output voltage of loops not participating in feedback cannot reach equilibrium, resulting in poor cross-regulation and making it unsuitable for applications requiring high multi-output voltage. Summary of the Invention

[0004] To address the issue of output voltage deviation in traditional bipolar output forward converters being susceptible to load disturbances, this invention proposes an isolated bipolar output self-equalizing DC-DC converter based on a basic forward converter. This converter comprises a basic forward converter and a bipolar voltage equalizing unit, with only one winding on the secondary side of the transformer. Compared to traditional converters employing dual-winding outputs, this design avoids the problem of uneven energy distribution caused by load disturbances.

[0005] The technical solution adopted in this invention is as follows:

[0006] An isolated bipolar output self-equalizing DC-DC converter, the converter comprising: a forward converter and a bipolar voltage equalizing unit;

[0007] The forward converter includes a DC input source u in Power switch S1, reset inductor L p1 Transformer T, Reset diode D p1 The rectifier diode D1, freewheeling diode D2, inductor L1, and output capacitor C1 are connected as follows:

[0008] Input power u in The positive terminals are respectively connected to the primary winding L of transformer T. p Upper end, reset inductor L p1 One end;

[0009] The primary winding L of transformer T p The other end is connected to the reset diode D p1 The cathode;

[0010] Reset diode D p1 The anodes are respectively connected to the input power supply u. in The negative terminal of the power switch S1;

[0011] The secondary winding L of transformer T S The upper end is connected to the anode of rectifier diode D1;

[0012] The cathode of rectifier diode D1 is connected to the cathode of freewheeling diode D2 and one end of inductor L1, respectively.

[0013] The other end of inductor L1 is connected to one end of output capacitor C1;

[0014] The other end of the output capacitor C1 is connected to the anode of the freewheeling diode D2 and the secondary winding L of the transformer T, respectively. S The lower end;

[0015] The bipolar voltage equalization unit includes a rectifier diode D3, a freewheeling diode D4, an inductor L2, an output capacitor C2, and a voltage equalization capacitor C. p Its connection form is as follows:

[0016] equalizing capacitor C p The other end is connected to the anode of rectifier diode D3 and one end of inductor L2, respectively;

[0017] The cathode of rectifier diode D3 is connected to the cathode of freewheeling diode D4 and one end of inductor L3, respectively.

[0018] The other end of inductor L3 is connected to one end of output capacitor C2;

[0019] The other end of the output capacitor C2 is connected to the anode of the freewheeling diode D4 and the other end of the inductor L2, respectively.

[0020] The connection relationship between the forward converter and the bipolar voltage equalization unit is as follows:

[0021] The secondary winding L of transformer T S The upper end and the equalizing capacitor C p One end of the capacitor is connected, and one end of the output capacitor C2 is connected to the other end of the output capacitor C1.

[0022] Load R L1 The two ends are connected to one end and the other end of the output capacitor C1, respectively, and the load R L2 The two ends are connected to one end and the other end of the output capacitor C2, respectively.

[0023] The gate of the power switch S1 is connected to the controller, and its duty cycle can vary between 0 and 1.

[0024] When power switch S1 is turned on, rectifier diodes D1 and D3 are turned on, and reset diode D... p1 When freewheeling diodes D2 and D4 are turned off, the input voltage is applied to the primary winding of transformer T, transferring energy to the secondary winding of transformer T. Inductor L1 and the left inductor L2, right inductor L3, and equalizing capacitor C in the bipolar voltage equalization unit... p Charging, output capacitor C1 and output capacitor C2 discharging;

[0025] When power switch S1 is turned off, rectifier diodes D1 and D3 are turned off, and reset diode D... p1 When freewheeling diodes D2 and D4 are turned on, inductor L1 and the left inductor L2 and right inductor L3 in the bipolar voltage equalization unit discharge through freewheeling diodes D2 and D4, converting the stored magnetic energy into electrical energy. Voltage equalization capacitor C... p Discharge occurs, while output capacitors C1 and C2 are charged.

[0026] Throughout the entire switching cycle, according to the inductor volt-second balance principle, the transformer secondary coil L... s The average voltage of inductor L1 and the left inductor L2 and right inductor L3 in the bipolar voltage equalization unit is 0. s →C p →L2→C2→L s The equalizing capacitor C can be obtained from the KVL principle of the circuit. p voltage u cp Equal to output voltage u o2 During the switch's conduction period, rectifier diodes D1 and D3 are turned on, and the voltage equalization capacitor C... p Through loop Cp →D1→L1→C1→L3→D3→C p It is connected in parallel with the output capacitor C1; during the switch-off period, the freewheeling diodes D2 and D4 are turned on, and the voltage equalizing capacitor C... p Through loop C p →L s →D2→L1→C1→L3→D4→L2→C p The voltage equalization capacitor C is connected in parallel with the output capacitor C1, therefore the voltage equalization capacitor C is connected throughout the entire cycle. p voltage u cp Equal to output voltage u o1 When capacitor C p When the voltage is large enough, the output voltage of the forward converter and the output voltage of the bipolar voltage equalizing unit are equal, thus achieving self-equalizing voltage of the bipolar output.

[0027] This invention discloses an isolated bipolar output self-equalizing DC-DC converter, with the following technical advantages:

[0028] 1) This invention can significantly reduce the voltage imbalance problem caused by the cross-regulation rate when the traditional forward converter is bipolar output, realize the self-equalizing effect of the bipolar output circuit, and reduce voltage deviation.

[0029] 2) The circuit topology is simple, the control system design and implementation are relatively easy, and it is suitable for applications requiring bipolar voltage power supply.

[0030] 3) The circuit is simple to control. It achieves automatic voltage equalization of bipolar output through a bipolar voltage equalization unit, without the need for complex sampling and control algorithms. Attached Figure Description

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0032] Figure 1 This is a schematic diagram of a traditional bipolar output forward converter circuit.

[0033] Figure 2 This is a simulation diagram of the output voltage waveform of a basic dual-winding output forward converter under unbalanced two-way loads;

[0034] Figure 3 This is the circuit schematic diagram of the present invention;

[0035] Figure 4 This is a simulation diagram of the output voltage waveform under unbalanced two-way load when using the present invention.

[0036] in: Figure 2 , Figure 4 All operating conditions are the same. Detailed Implementation

[0037] Depend on Figure 1 It can be seen that the traditional bipolar output forward converter contains two secondary windings. Due to the problem of cross regulation, the bipolar output voltage will have a voltage deviation when the load is unbalanced, and it is difficult to keep the dual output voltages consistent.

[0038] Depend on Figure 2 It can be seen that the output voltage difference of the traditional bipolar output forward converter is 11V when the load is unbalanced, which is difficult to meet the output voltage requirements under unbalanced load conditions.

[0039] like Figure 3 As shown, an isolated bipolar output self-equalizing DC-DC converter includes a basic forward converter and a bipolar voltage equalizing unit, wherein:

[0040] A basic forward converter includes a DC input source u in Power switch S1, reset winding L p1 Transformer T, Reset diode D p1 The components are: rectifier diode D1, freewheeling diode D2, inductor L1, and output capacitor C1. Their connection configuration is as follows: reset inductor L... p1 The upper end and the primary winding L of transformer T p The upper end is also connected to the input power supply u in The positive terminal, reset inductor L p1 The lower end is connected to the reset diode D. p1 The cathode, the primary winding L of transformer T p The lower end is connected to the drain of power switch S1, the source of power switch S1, and the reset diode D. p1 The anodes are connected to the input power supply u. in The negative terminal, the gate of power switch S1 is connected to the controller, and the secondary winding L of transformer T is connected to the controller. S The upper end is connected to the anode of rectifier diode D1. The cathode of rectifier diode D1 is connected to the cathode of freewheeling diode D2 and the left end of inductor L1. The right end of inductor L1 is connected to the upper end of output capacitor C1. The lower end of output capacitor C1 and the anode of freewheeling diode D2 are connected together to the secondary winding L of transformer T. S The lower end.

[0041] A bipolar voltage equalization unit includes a rectifier diode D3, a freewheeling diode D4, a left inductor L2, a right inductor L3, an output capacitor C2, and a voltage equalization capacitor C. p Among them, the equalizing capacitor C pThe right end of the circuit is connected to the anode of the rectifier diode D3 and the upper end of the left inductor L2, respectively. The cathode of the rectifier diode D3 is connected to the cathode of the freewheeling diode D4 and the left side of the right inductor L3. The right side of the right inductor L3 is connected to the upper end of the output capacitor C2. The lower end of the output capacitor C2 and the anode of the freewheeling diode D4 are connected to the lower end of the left inductor L2.

[0042] The connection relationship between the basic forward converter and the bipolar voltage equalization unit is as follows: the upper end of the secondary winding of transformer T is connected to the voltage equalization capacitor C. p The left end of the capacitor is connected, and the upper end of the output capacitor C2 and the lower end of the output capacitor C1 are connected.

[0043] Load R L1 The two ends of the capacitor are connected to the upper and lower ends of the output capacitor C1, respectively, and the load R is connected to the lower end of the output capacitor C1. L2 The two ends are connected to the upper and lower ends of the output capacitor C2, respectively.

[0044] The gate of the power switch S1 is connected to a controller, and its duty cycle can vary between 0 and 1.

[0045] When power switch S1 is turned on, rectifier diodes D1 and D3 are turned on, and reset diode D... p1 When freewheeling diodes D2 and D4 are turned off, the input voltage is applied to the primary winding of transformer T, transferring energy to the secondary winding of transformer T. Inductor L1 and the left inductor L2, right inductor L3, and equalizing capacitor C in the bipolar voltage equalization unit... p During charging, output capacitors C1 and C2 discharge.

[0046] When power switch S1 is turned off, rectifier diodes D1 and D3 are turned off, and reset diode D... p1 When freewheeling diodes D2 and D4 are turned on, inductor L1 and the left inductor L2 and right inductor L3 in the bipolar voltage equalization unit discharge through freewheeling diodes D2 and D4, converting the stored magnetic energy into electrical energy. Voltage equalization capacitor C... p Discharge occurs, while output capacitors C1 and C2 are charged.

[0047] Throughout the entire switching cycle, according to the inductor volt-second balance principle, the transformer secondary coil L... s The average voltage of inductor L1 and the left inductor L2 and right inductor L3 in the bipolar voltage equalization unit is 0. s →C p →L2→C2→L s The equalizing capacitor C can be obtained from the KVL principle of the circuit. p voltage u cp Equal to output voltage u o2During the switch's conduction period, rectifier diodes D1 and D3 are turned on, and the voltage equalization capacitor C... p Through loop C p →D1→L1→C1→L3→D3→C p It is connected in parallel with the output capacitor C1; during the switch-off period, the freewheeling diodes D2 and D4 are turned on, and the voltage equalizing capacitor C... p Through loop C p →L s →D2→L1→C1→L3→D4→C p The voltage equalization capacitor C is connected in parallel with the output capacitor C1, therefore the voltage equalization capacitor C is connected throughout the entire cycle. p voltage u cp Equal to output voltage u o1 When capacitor C p When the voltage is large enough, the output voltage of the forward converter and the output voltage of the bipolar voltage equalizing unit are equal, thus achieving self-equalizing voltage of the bipolar output.

[0048] Depend on Figure 4 As can be seen from the present invention, the output voltages under unbalanced loads are equal and there is no difference, which effectively reduces the output voltage difference of traditional bipolar output forward converters. Under unbalanced load conditions, the circuit itself achieves self-equalization of output voltage, thus solving the problem of unbalanced output voltage.

Claims

1. An isolated bipolar output self-equalizing DC-DC converter, characterized in that... The converter includes: a forward converter and a bipolar voltage equalization unit; The forward converter includes a DC input source. u in Power switch S1, reset inductor L p1 Transformer T, Reset diode D p1 1. Rectifier diode D1, Freewheeling diode D2, Inductor L 1. Output capacitor C 1. Its connection method is as follows: DC input source u in The positive terminals are respectively connected to the primary winding of transformer T. L p Upper end, reset inductor L p1 One end; The primary winding of transformer T L p The lower end is connected to the drain of power switch S1; Reset diode D p1 The anodes are respectively connected to the DC input source. u in The negative terminal of the power switch S1 and the source terminal of the power switch S1 are connected to the controller. Reset Inductor L p1 The other end is connected to the reset diode D p1 The cathode; The secondary winding of transformer T L s The upper end is connected to the anode of rectifier diode D1; The cathode of rectifier diode D1 is connected to the cathode of freewheeling diode D2 and the inductor, respectively. L One end of 1; inductance L The other end of 1 is connected to the output capacitor. C One end of 1; Output capacitor C The other end of 1 is connected to the anode of the freewheeling diode D2 and the secondary winding of the transformer T, respectively. L s The lower end; The bipolar voltage equalization unit includes a rectifier diode D3, a freewheeling diode D4, and an inductor. L 2. Inductance L 3. Output capacitor C 2. Equalizing capacitor C p Its connection form is as follows: equalizing capacitor C p The other end is connected to the anode of rectifier diode D3 and the inductor, respectively. L One end of 2; The cathode of rectifier diode D3 is connected to the cathode of freewheeling diode D4 and the inductor, respectively. L 3 at one end; inductance L The other end of 3 is connected to the output capacitor. C One end of 2; Output capacitor C The other end of 2 is connected to the anode of the freewheeling diode D4 and the inductor, respectively. L The other end of 2; The connection relationship between the forward converter and the bipolar voltage equalization unit is as follows: The secondary winding of transformer T L s upper end and equalizing capacitor C p One end is connected to the output capacitor. C 2 One end is connected to the output capacitor C The other end of 1 is connected; load R L1 The two ends are respectively connected to the output capacitor C One end of 1 is connected to the other end, and the load is... R L2 The two ends are respectively connected to the output capacitor C Connect one end of 2 to the other end.

2. The isolated bipolar output self-equalizing DC-DC converter according to claim 1, characterized in that: The gate of the power switch S1 is connected to the controller, and its duty cycle can vary between 0 and 1.

3. The isolated bipolar output self-equalizing DC-DC converter according to claim 1, characterized in that: When power switch S1 is turned on, rectifier diodes D1 and D3 are turned on, and reset diode D... p1 When freewheeling diodes D2 and D4 are turned off, the input voltage is applied to the primary winding of transformer T, transferring energy to the secondary winding of transformer T. The inductor... L 1. The left inductor in the bipolar voltage equalization unit L 2. Right side inductor L 3. Voltage equalizing capacitor C p Charging, output capacitor C 1. Output capacitor C 2. Discharge; When power switch S1 is turned off, rectifier diodes D1 and D3 are turned off, and reset diode D... p1 When freewheeling diodes D2 and D4 are turned on, the inductor... L 1. The left inductor in the bipolar voltage equalization unit L 2. Right side inductor L 3. Discharge is achieved through freewheeling diodes D2 and D4, converting the stored magnetic energy into electrical energy; equalizing capacitors... C p Discharge, output capacitor C 1 and output capacitor C 2. Charging.

4. The bipolar output self-equalizing voltage method of the converter according to claim 1 or 2, characterized in that: Throughout the entire switching cycle, the secondary winding of transformer T L s ,inductance L 1. The left inductor in the bipolar voltage equalization unit L 2 and the right inductor L The average voltage of 3 is 0, due to L s → C p → L 2→ C 2→ L s The equalizing capacitor can be obtained from the KVL principle of the circuit. C p voltage u cp equal to output voltage u o2 ; During the switching period, rectifier diodes D1 and D3 are turned on, and the voltage equalization capacitor... C p Through the loop C p →D1→ L 1→ C 1→ L 3→D3→ C p With output capacitor C 1. Parallel connection; During the switch-off period, freewheeling diodes D2 and D4 are turned on, and the voltage equalization capacitor... C p Through the loop C p → L s →D2→ L 1→ C 1→ L 3→D4→ L 2→ C p With output capacitor C 1. Parallel connection, therefore the voltage equalizing capacitors throughout the entire cycle C p voltage u cp equal to output voltage u o1 When the capacitor C p When the voltage is large enough, the output voltage of the forward converter and the output voltage of the bipolar voltage equalizing unit are equal, thus achieving self-equalizing voltage of the bipolar output.

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