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MindMap Gallery Chapter 5 DC-DC Converter Circuit 2

Chapter 5 DC-DC Converter Circuit 2

This is a mind map about Chapter 5 DC-DC Converter Circuit 2, including basic chopper circuits, compound chopper circuits and polyphase multiple chopper circuits.

Edited at 2023-11-22 22:35:27

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Chapter 5 DC-DC Converter Circuit 2

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Outline

ELEKTRONIKA DAYA MIND MAPPING
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DC-DC converter circuit

Overview

Convert direct current into another fixed voltage or adjustable voltage direct current

Direct DC converter circuit

Indirect DC converter circuit

1. Basic chopper circuit

Buck chopper circuit

It is mainly used as a power supply for electronic circuits, and can also drive DC motors or battery loads.

working principle

When t=0; V conducts; E supplies power to the load;

When t=t1; V is turned off; diode VD freewheels; load voltage uo is close to 0

Quantitative relationship

Current continuous

Load current average

average load voltage

is the duty cycle

Intermittent current

Current intermittent conditions

Output voltage average

Load average current

Three control methods of chopper circuit

Pulse width modulation (pulse width modulation type)

Keep the switching period T unchanged and adjust the switch conduction time ton

Frequency modulation (FM type)

Keep the switch conduction time ton unchanged and change the switching period T

Hybrid

Both ton and T are adjustable to change the duty cycle

Boost chopper circuit

working principle

When V is in the on-state, the power supply E charges the inductor L, the current is constant I1, the capacitor C supplies power to the load R, and the output voltage is constant.

When V is in the off-state, the power supply E and the inductor L charge the capacitor C at the same time and provide energy to the load.

Quantitative relationship

Output voltage average

升压比：

Output current average

Supply current

application

One is used for DC motor transmission, the other is used as a single-phase power factor correction circuit, and the third is used in other AC and DC power supplies.

Quantitative relationship

Current continuous

Intermittent current

Buck-boost chopper circuit and Cuk chopper circuit

Buck-boost chopper circuit

working principle

When the controllable switch V is in the on state, the power supply E supplies power to the inductor L via V to store energy. At this time, the current is i1; at the same time, the capacitor C maintains a constant output voltage and supplies power to the load R. After that, V is turned off, the energy stored in the inductor L is released to the load, and the current is i2.

The output voltage

Cuk chopper circuit

Relationship between output voltage and power supply

Sepic chopper circuit and Zeta chopper circuit

working principle

The basic working principle of the Sepic chopper circuit is: when V is in the on-state, the E-L1-V loop and the C1-V-L2 loop are turned on at the same time. L1 and L2 energy storage. When V is in the off state, the E - L1 - C1 - VD - load (C2 and R) circuit and the L2-VD-load circuit are turned on at the same time. At this stage, E and L1 not only supply power to the load, but also charge C1, and C 1The stored energy is transferred to L2 when V is in the on-state.

The basic working principle of the Zeta chopper circuit is: when V is in the on-state, the power supply E stores energy in the inductor L1 through the switch V. able. At the same time, E and C1 jointly supply power to the load via L2. After V is turned off, L1 charges C1 through VD, and its stored energy is transferred to C1. At the same time, the current of L2 continues to flow through VD.

Input-output relationship

the difference

In the Sepic circuit, the power supply current is continuous but the load current is a pulse waveform, which is conducive to input filtering; conversely, the power supply current of the Zeta circuit is a pulse waveform and the load current is continuous. Compared with the two circuits in the previous section, the output voltages of the two circuits here are both positive polarity, and the input-output relationship is the same.

2. Compound chopper circuit and polyphase multiple chopper circuit

Current reversible chopper circuit

It is a combination of a buck chopper circuit and a boost chopper circuit.

Fundamental

1. Em——R——L——VD2——E——Em 2. E（ )——V1——L——R——Em——E（-） 3. L——R——Em ——VD1 4. Em——R——L——V2——Em

The armature current of the motor can be positive or negative, but the voltage can only be of one polarity, so it can work in the first and second quadrants.

Bridge reversible chopper circuit

When V4 is kept in the on-state, the chopper circuit is equivalent to the above-mentioned current reversible chopper circuit, providing positive voltage to the motor, allowing the motor to operate in the 1st and 2nd quadrants, that is, forward motoring and forward regenerative braking states. . At this time, it is necessary to prevent V3 from being turned on and causing a short circuit in the power supply. When V2 is kept in the on-state, V3, VD3 and V4, VD4 are equivalent to another set of current reversible chopper circuits, which provide negative voltage to the motor, allowing the motor to operate in the 3rd and 4th quadrants.

Polyphase multiple chopper circuit

1. The total output current is the sum of the output currents of the three chopper circuit units. Its average value is three times the average value of the unit output current, and the pulsation frequency is also three times. 2. The total output current pulsation amplitude becomes very small. 3. The total weight of the required smoothing reactor is greatly reduced. 4. The maximum pulsation rate of the total output current being touched (the ratio of the current pulsation amplitude to the average current value) is inversely proportional to the square of the number of phases.

Isolated DC-DC converter circuit

There are the following reasons for using this circuit with a relatively complex structure to complete the DC-DC conversion: 1) The output and input terminals need to be isolated. 2) Some applications require multiple outputs that are isolated from each other. 3) The ratio of output voltage to input voltage is much less than 1 or much greater than 1. 4) Using a higher operating frequency in the AC link can reduce the size and weight of the transformer, filter inductor, and filter capacitor. Generally, the operating frequency should be higher than the human hearing limit of 20kHz to avoid harsh noise from the transformer and inductor.

forward circuit

The output inductor current is continuous

Output inductor current is discontinuous