CN203883673U - Improved Z-source boost DC-DC converter - Google Patents

Abstract

The utility model discloses an improved Z-source step-up DC-DC converter, which comprises a voltage source, a Z-source impedance network, a MOS tube, a second diode, an output filter capacitor and a load; the Z-source impedance network consists of The first inductance, the second inductance, the first capacitor, the second capacitor and the first diode form, the voltage source V _s , the Z source impedance network and the MOS transistor form a boost circuit, the second diode, the output filter Capacitors and loads form the output circuit. The entire circuit of the utility model has a simple structure, high output voltage gain, and low voltage stress of the capacitance of the Z source impedance network, and the circuit does not have the problem of start-up impact.

Description

An Improved Z Source Boost DC-DC Converter

technical field

The utility model relates to the field of power electronics, in particular to an improved Z-source step-up DC-DC converter.

Background technique

In fuel cell power generation and photovoltaic power generation, due to the low DC voltage provided by a single solar cell or a single fuel cell, it cannot meet the electricity demand of existing electrical equipment, nor can it meet the needs of grid connection. It is often necessary to combine multiple batteries connected in series to achieve the desired voltage. On the one hand, this method greatly reduces the reliability of the entire system, and on the other hand, it needs to solve the problem of series voltage equalization. For this reason, a high-gain DC-DC converter capable of converting low voltage to high voltage is required. The Z-source step-up DC-DC converter proposed in recent years is a high-gain DC-DC converter, but the circuit has a high Z-source impedance network capacitor voltage stress, and there is a large startup shock when the circuit starts Current and voltage limit the practical application of this circuit.

Utility model content

In order to overcome the shortcomings and deficiencies of the prior art, the utility model provides an improved Z-source step-up DC-DC converter.

The utility model adopts the following technical solutions:

An improved Z source step-up DC-DC converter, including a voltage source V _s , a Z source impedance network, a MOS transistor S, a second diode D ₂ , an output filter capacitor C _o and a load R _L ; the voltage The source V _s , the Z source impedance network and the MOS transistor S form a boost circuit, and the second diode D ₂ , the output filter capacitor C _o and the load _RL form an output circuit.

The Z source impedance network is composed of a first inductor L ₁ , a second inductor L ₂ , a first capacitor C ₁ , a second capacitor C ₂ and a first diode D ₂ ;

The anode of the voltage source V _s is respectively connected to one end of the first inductor _L1 and the negative electrode of the first capacitor _C1 , and the anode of the first diode _D1 is respectively connected to the other end of the first inductor L1 and the first capacitor _C1 . The cathode of the second capacitor _C2 is connected; the cathode of the first diode _D1 is respectively connected to the positive electrode of the first capacitor _C1 and one end of the second inductance _L2 , and the other end of the second inductance _L2 is respectively connected to The anode of the second capacitor _C2 , the drain of the MOS transistor S, and the anode of the second diode _D2 are connected, and the cathode of the second diode _D2 is respectively connected to the anode of the output filter capacitor C _o and the load R _L One end of the load _RL is connected to the negative pole of the output filter capacitor C _o , the source of the MOS transistor S and the negative pole of the voltage source V _s respectively.

The first capacitor C ₁ , the second capacitor C ₂ and the output filter capacitor C _o are all electrolytic capacitors.

When the MOS tube is turned on, the voltage source is connected in series with the first capacitor to charge and store energy for the second inductor; at the same time, the voltage source is connected in series with the second capacitor to charge and store energy for the first inductor; the output filter capacitor supplies power to the load; when the MOS tube is turned off, The voltage source, together with the first inductor and the second inductor, supplies power to the output filter capacitor and the load to complete the voltage boosting function.

The beneficial effects of the utility model:

The utility model has high voltage gain, low capacitive voltage stress of the Z source impedance network, and has a good inhibitory effect on the starting impulse current and voltage;

The circuit of the utility model is suitable for occasions where the input voltage varies widely, such as fuel cell power generation, photovoltaic power generation and other new energy power generation technical fields.

Description of drawings

Fig. 1 is a kind of improved Z source step-up DC-DC converter circuit diagram of the utility model;

Figure 2(a) to Figure 2(b) are the equivalent circuit diagrams of the circuit shown in Figure 1 when the MOS transistor S is turned on and off, respectively. The solid line in the figure indicates the part where current flows in the converter. The dotted line indicates the part of the converter where no current flows;

Fig. 3 (a) ~ Fig. 3 (e) are the wave diagrams when the circuit of the utility model is working, wherein Fig. 3 (a) is the driving waveform diagram of the MOS tube, and Fig. 3 (b) is the waveform diagram of the input voltage source, Fig. 3(c) is the current waveform diagram of the first inductor and the second inductor in the Z source impedance network, Figure 3(d) is the waveform diagram of the output voltage, and Figure 3(e) is the first capacitor and the second capacitor in the Z source impedance network The voltage waveform diagram of the second capacitor.

Detailed ways

The utility model will be described in further detail below in conjunction with the embodiments and accompanying drawings, but the implementation of the utility model is not limited thereto.

Example

As shown in Figure 1, an improved Z-source step-up DC-DC converter includes a voltage source V _s , a Z-source impedance network, a MOS transistor S, a second diode D ₂ , an output filter capacitor C _o and a load R _L ; the voltage source V _s , Z source impedance network and MOS transistor S constitute a boost circuit, and the second diode D ₂ , output filter capacitor C _o and load R _L constitute an output circuit.

The Z source impedance network is composed of a first inductor L ₁ , a second inductor L ₂ , a first capacitor C ₁ , a second capacitor C ₂ and a first diode D ₁ ;

The specific connection method of the circuit is:

The anode of the voltage source V _s is respectively connected to one end of the first inductor _L1 and the negative electrode of the first capacitor _C1 , and the anode of the first diode _D1 is respectively connected to the other end of the first inductor L1 and the first capacitor _C1 . The cathode of the second capacitor _C2 is connected; the cathode of the first diode _D1 is respectively connected to the positive electrode of the first capacitor _C1 and one end of the second inductance _L2 , and the other end of the second inductance _L2 is respectively connected to The anode of the second capacitor _C2 , the drain of the MOS transistor S, and the anode of the second diode _D2 are connected, and the cathode of the second diode _D2 is respectively connected to the anode of the output filter capacitor C _o and the load R _L One end of the load _RL is connected to the negative pole of the output filter capacitor C _o , the source of the MOS transistor S and the negative pole of the voltage source V _s respectively.

The first capacitor C ₁ , the second capacitor C ₂ and the output filter capacitor C _o are all electrolytic capacitors.

When the MOS transistor S is turned on, the voltage source V _s is connected in series with the first capacitor C ₁ to charge and store energy for the second inductor L ₂ , and at the same time, the voltage source V _s is connected in series with the second capacitor C ₂ to charge and store energy for the first inductor L ₁ ; The output filter capacitor C _o supplies power to the load R _L ; when the MOS transistor S is turned off, the voltage source V _s together with the first inductor L ₁ and the second inductor L ₂ supplies power to the output filter capacitor C _o and the load R _L to complete the boost Function. The whole circuit has simple structure, high output voltage gain, and low capacitive voltage stress in the Z source impedance network, and the circuit does not have the problem of start-up shock.

Concrete work process of the present utility model:

Stage 1, as shown in FIG. 2( a ): the MOS transistor S is turned on, and at this time, the first diode D ₁ and the second diode D ₂ are in an off state. The circuit forms three loops, namely: the voltage source V _s and the second capacitor C ₂ together charge and store the energy of the first inductor L ₁ to form a loop; the voltage source V _s and the first capacitor C ₁ together charge the second inductor L ₂ charges and stores energy to form a loop; the output filter capacitor C _o supplies power to the load R _L to form a loop.

Phase 2, as shown in Fig. 2(b): the MOS transistor S is turned off, and at this time, both the first diode D ₁ and the second diode D ₂ are turned on. The circuit forms three loops, which are: the voltage source V _s together with the first inductor L ₁ and the second inductor L ₂ supplies power to the output filter capacitor C _o and the load R _L to form a boost loop; the first inductor L ₁ pairs The first capacitor _C1 is charged to form a loop; the second inductor _L2 is charged to the second capacitor _C2 to form a loop.

In summary, it is assumed that the duty ratio of the MOS transistor S is D, and the switching period is T _s . Due to the symmetry of the Z source impedance network, that is, the inductance of the first inductor L ₁ and the second inductor L ₂ are equal, the capacitance values of the first capacitor C ₁ and the second capacitor C ₂ are equal. Therefore, v _L1 =v _L2 =v _L , V _C1 =V _C2 =V _C . v _L1 , v _L2 , V _C1 and V _C2 are the voltages of the first inductor L ₁ , the second inductor L ₂ , the first capacitor C ₁ and the second capacitor C ₂ respectively, so that v _L and V _C are respectively set to Z The inductor and capacitor voltages of the source impedance network.

In one switching cycle, let the output voltage be V _o , when the converter enters steady-state operation, the following derivation process of the voltage relationship is obtained.

During the conduction period of the MOS transistor S, the voltage source V _s is connected in series with the first inductor L ₁ and the second capacitor C _2. Since the polarity of the voltage source V _s is consistent with the voltage polarity of the second capacitor C ₂ , there is a formula:

v _L1 =v _L =V _s +V _C2 =V _s +V _C (1)

At the same time, the voltage source V _s is connected in series with the second inductance L ₂ and the first capacitor C ₁ , and since the polarity of the voltage source V _s is consistent with the voltage polarity of the first capacitor C ₁ , there is a formula:

v _L2 =v _L =V _s +V _C1 =V _s +V _C (2)

The conduction time of the MOS transistor S in a switching period T _s is DT _s .

When the MOS transistor S is turned off, the first diode _D1 is turned on, and the first inductor _L1 is connected in parallel with the first capacitor _C1 , so the formula is:

v _L1 =v _L =-V _C1 =-V _C (3)

At the same time, the second inductor _L2 is connected in parallel with the second capacitor _C2 , so there is a formula:

v _L2 =v _L =-V _C2 =-V _C (4)

The voltage source V _s is connected in series with the first inductance L ₁ , the second inductance L ₂ and the output circuit part, so the formula is:

V _o =V _s -v _L1 -v _L2 =V _s -2v _L =V _s +2V _C (5)

The turn-off time of the MOS transistor S in a switching cycle T _s is (1-D)T _s .

From the above analysis, according to the symmetry of the Z source impedance network and the conservation principle of inductive volt-seconds, the simultaneous equations (1) to (4) can be obtained:

(V _s +V _C )DT _s +(-V _C )(1-D)T _s =0 (6)

Therefore, the relationship expression between the capacitance voltage V _C of the Z source impedance network and the voltage source V _s can be obtained as:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; D.</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; D.</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

And from the formula (5), the gain factor expression of the circuit can be obtained as:

$\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

From formula (7) and formula (8), the relationship between the capacitance voltage V _C of the Z source impedance network of this circuit and the output voltage V _o can be obtained as:

V _C =DV _o (9)

Since the duty cycle D of the utility model circuit is not more than 0.5, it can be seen from formula (9) that the maximum value of the capacitance voltage V _C in the utility model circuit Z source impedance network is not more than 0.5 times the output voltage V _o value, so the capacitive voltage stress in the utility model circuit Z source impedance network is relatively low. Figure 3(a) is the waveform diagram of the driving V _g of the MOS transistor S; Figure 3(b) is the waveform diagram of the voltage source _Vs ; Figure 3(c) is the first inductance L ₁ and the second inductance in the Z source impedance network The waveform diagram of the current i _L of the inductor L ₂ ; Figure 3(d) is the waveform diagram of the output voltage V _o ; Figure 3(e) is the voltage V _C of the first capacitor C ₁ and the second capacitor C ₂ in the Z source impedance network Waveform diagram.

In addition, due to the characteristics of the topological structure of the utility model circuit itself, when it is started, the first inductance _L1 and the second inductance _L2 in the Z source impedance network have an inhibitory effect on the start-up inrush current, which is beneficial to the soft start of the converter , reducing the impact damage to the device.

To sum up, the circuit of the utility model not only has higher voltage gain, but also has low capacitor voltage stress in the Z source impedance network, and there is no start-up shock circuit.

The above-mentioned embodiment is the preferred implementation mode of the present utility model, but the implementation mode of the present utility model is not limited by the described embodiment, and any other changes, modifications, modifications made without departing from the spirit and principle of the present utility model Substitution, combination, and simplification should all be equivalent replacement methods, and are all included in the protection scope of the present utility model.

Claims (3)

1. An improved Z source step-up DC-DC converter, including a voltage source (V _s ), characterized in that it also includes a Z source impedance network, a MOS tube (S), and a second diode (D ₂ ) , output filter capacitor (C _o ) and load (R _L ); the Z source impedance network consists of the first inductor (L ₁ ), the second inductor (L ₂ ), the first capacitor (C ₁ ), the second capacitor ( C ₂ ) and the first diode (D ₁ ); The anode of the voltage source (V _s ) is respectively connected to one end of the first inductor (L ₁ ) and the cathode of the first capacitor (C ₁ ), and the anode of the first diode (D ₁ ) is respectively connected to the first The other end of the inductor (L ₁ ) is connected to the negative pole of the second capacitor (C ₂ ); the cathode of the first diode (D ₁ ) is connected to the positive pole of the first capacitor (C ₁ ) and the second inductor (L ₂ ) connected to one end, the other end of the second inductor (L ₂ ) is respectively connected to the anode of the second capacitor (C ₂ ), the drain of the MOS transistor (S) and the anode of the second diode (D ₂ ) connected, the cathode of the second diode (D ₂ ) is respectively connected to the anode of the output filter capacitor (C _o ) and one end of the load ( _RL ), and the other end of the load ( _RL ) is respectively connected to the output filter The negative pole of the capacitor (C _o ), the source pole of the MOS transistor (S) and the negative pole of the voltage source (V _s ) are connected. 2. An improved Z source step-up DC-DC converter according to claim 1, characterized in that the voltage source (V _s ), Z source impedance network and MOS tube (S) constitute a boost circuit , the second diode (D ₂ ), the output filter capacitor (C _o ) and the load (R _L ) form the output circuit. 3. An improved Z-source step-up DC-DC converter according to claim 1, characterized in that the first capacitor (C ₁ ), the second capacitor (C ₂ ) and the output filter capacitor (C _o ) are electrolytic capacitors.