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Higher than the Interleaved Boost step-up circuit analysis

In Electronic Infomation Category: H | on March 19,2011

Abstract: This paper analyzes the practical application of traditional BooST circuit problems, proposed a modified Interleaved Boost circuit. In the continuous inductor current mode, according to the duty cycle is greater than or less than 0.5 in the case, detailed analysis of the working process of the circuit are derived under the steady state relation between output voltage, and CXA2045Q datasheet and finally the simulation verify the theoretical analysis of the correct sex.

0 Introduction

Boost converter is the most commonly used as a converter, with the promotion of new energy sources, as solar energy, fuel cells, batteries and CXA2045Q price and other input source with the characteristics of the input voltage is low, boost converter become indispensable key components. Boost commonly used non-isolated boost converter, the high output voltage applications, the parasitic parameters can not achieve a high ratio of input and CXA2045Q suppliers and output voltages. The other step-up circuit is isolated boost circuits, such as forward, flyback circuit. Isolated boost circuit in the transformer must be used often have isolation transformer functions in isolation or volume requirements that do not need the smaller applications, step by difficult to meet the requirements of the transformer, the other caused a transformer leakage inductance series of problems, such as switching voltage overshoot, EMI, etc., often on the power supply itself and the surrounding equipment, a security risk.

Order to overcome the common boost converter in high power, high input and output variables and other occasions than the application of the restrictions of this paper, a new circuit topology and its working methods, and simulation was carried out.

1 works

The following shortcomings of Boost Circuit, in an ideal situation:


M (D) = U0Uin = 11-D (1) according to equation (1), in a certain input voltage, in theory, can generate any output voltage higher than the input voltage. The reality, due to the inductor, diode, the switch will have some losses, these losses could be equivalent to a resistor in series with the inductor RL, shown in Figure 1:


equivalent circuit of Figure 1 Boost At this time balancing based on magnetic principles

:


From (2), (3) available:


According to equation (4), in different RL / R case, M (D) shown in Figure 2. Thus, in the real circuit, Boost circuit than the limited boost the limit, the output voltage to input voltage is generally 4 to 5 times. In high power applications, due to a serious loss, but lower than boost.

To overcome the above shortcomings of non-isolated step-up circuit, we study the boost converter shown in Figure 3, which consists of Interleaved Boost circuit and the capacitor in series combination.


Figure 2 Relationship between step-up ratio and duty cycle curve


high step-up ratio in Figure 3 Interleaved Boost circuit diagram

In continuous inductor current mode, when the duty cycle is greater than 0.5, the system works timing shown in Figure 4, PS1, PS2, respectively, for the switch S1, S2 of the driving pulse. ID1, ID2, respectively flow through the freewheeling diode D1, D2 of the current.


system working waveform in Figure 4

In a cycle system status as follows:

[T0 ~ t1] stage, S1, S2 simultaneously. Input current flows through the inductor and switch, all of the diode current is zero, the inductor stores energy in Figure 5.


Figure 5 [t0 ~ t1] stage of the circuit diagram

[T1 ~ t2] stage, S1 turn-on, S2 off. The energy stored in inductor L2 through D4, D2 released to the C1, Co, shown in Figure 6. At this point C1, C2 through the D4 series, while in parallel with the Co through D2, the output voltage is equal to the voltage across C1 or C2 twice.


Figure 6 [t1 ~ t2] stage of the circuit diagram

[T2 ~ t3] stage, S1, S2 simultaneously. System state and the [t0 ~ t1] the same stage.

[T3 ~ t4] stage, S1 off, S2 turns on. The energy stored in inductor L1 through D3, D1 released to the C2, Co, shown in Figure 7. At this point C1, C2 D3 series by the same time, in parallel with the Co through D1, L2 to turn and store energy.


Figure 7 [t3 ~ t4] stage of the circuit diagram

In continuous inductor current mode, the duty cycle greater than 0.5, the set L1 = L2 = L, C1 = C2 = C, UC1 = UC2 = U, the flux conservation was:


According to equation (5) available:


Output voltage U0 is equal to the sum of UC1 and UC2:


From (7) shows that under the same duty cycle, the circuit structure described in this paper is the boost circuit Bibi Boost boost traditional than tripled.

In continuous inductor current mode, the duty cycle is less than 0.5, the switch S1, S2 of the driving pulse shown in Figure 8.


Figure 8 duty cycle is less than 0.5, the switch S1, S2 of the driving pulse

In a cycle system working state as follows:

[T0 ~ t1] phase, switch S1 S2 turn-off. The energy stored in inductor L2 through D4, D2 released to the C1, C0, then the circuit shown in Figure 6 the same state, and the C1, C2 through the D4 series, while in parallel with the Co through D2, the output voltage is equal to two ends of C1 or C2 twice the voltage.

[T1 ~ t2] phase, switch S1, S2 at the same time off. Inductor current, respectively, by C1, D1 and C2, D2 to the load discharge, shown in Figure 9.


Figure 9 S1, S2 off when the same principle diagram

[T2 ~ t3] stage, S1 off, S2 turns on. The energy stored in inductor L1 through D3, D1 released to the C2, Co, then the state circuit shown in Figure 7, the same, and the C1, C2 in series by D3, while D1 in parallel with the Co through the inductor L2 to turn and store energy .

[T3 ~ t4] phase, switch S1, S2 off at the same time, system status, and [t1 ~ t2] phase of the same.

In continuous inductor current mode, the duty cycle of less than 0.5, the set L1 = L2 = L, C1 = C2 = C, UC1 = UC2 = U, UCo = Uo, the state based on the above analysis, [t0 ~ t1] period, the voltage across the inductor L1 to Uin, in [t2 ~ t3] time period, the voltage across the inductor L1 is UC2-Uin, in [t3 ~ t4] and [t2 ~ t3] time period, voltage across the inductor L1 UCo-UC1-Uin, by the flux conservation was:


According to equation (8), (9) available:


Output voltage Uo is the sum of UC1 and UC2:


Therefore, in the continuous inductor current mode, whether the duty cycle is greater than or less than 0.5, the output voltage and input voltage between both satisfy (11).

2 simulation results

Verify the circuit in order to analyze the working principle of this selection of PSIM simulation software. Circuit parameters are as follows: Uin = 25V, Uo = 200 V, L1 = L2 = 200H, C1 = C2 = Co = 200F, switching frequency is 50 kHz, output power 1 000 W. Inductance and capacitance parameters of the size of the type (12), (13), (14) OK.


Where, lL1 L1 of the inductor current ripple.


Where, UC1 ripple voltage for the capacitor C1, Iin is input current.


Uo the output voltage ripple.

Simulation results below, an analysis of the circuit works. Figure 10 shows the steady state switch S1, S2 of the drive waveform, the duty cycle can be seen from Figure 0.75, the input voltage and output voltage relationship:



Figure 10

Figure 11,12 shows the switch current IS1, IS2 and diode current ID3, ID4 plot. The figure shows simulation waveforms shown in Figure 4, switch, diode waveforms consistent with theoretical analysis to verify the theoretical analysis. Figure 13, Figure 14 for the input inductor L1, L2 and the output voltage Uo waveforms. By the formula (12), (14) can be obtained, theoretical inductor current, output voltage ripple are 1.875 A, 0.125 V.


Figure 11, switch S1, S2 diode current waveform Figure 12 D3, D4 current waveform


Figure 13, inductor L1, L3 current waveform output voltage waveforms in Figure 14

3 Conclusions

A detailed analysis of this non-isolated boost Boost circuit restriction than by reason of a high step-up circuit than the Interleaved Boost topology. This circuit structure can not use under the conditions of the transformer, effectively improve the input and output voltage ratio. In the main text of the working process of the circuit and its main parameters were analyzed by the simulation experiments to validate them. Through analysis, the use of the circuit than the ordinary Boost circuit, step-up ratio increased 2-fold, greatly expanded the Boost circuit of non-isolated applications.

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