Average-Value DC-DC Converter

Average-value DC-DC converter

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Libraries:
Simscape / Electrical / Semiconductors & Converters / Converters

Description

The Average-Value DC-DC Converter block represents a controlled average-value DC-DC converter. You can program the block as a buck converter, boost converter, or buck-boost converter by providing the duty cycle. The diagram shows the equivalent circuit for the block with duty cycle as input. The converter contains a controlled current source and a controlled voltage source. Use the duty cycle, the current reference, or the voltage reference ports as control input to convert the electrical energy between the connected components on either side of the converter.

Equations

If you set the Control input parameter to Duty cycle, the input current and output voltage are a function of the duty cycle and depend on the converter type.

Voltage and Current Equations

Converter Type	Output Voltage, $v_2$	Input Current, $i_1$
Buck	$$v_2=DutyCycle\cdot v_1$$	$$i_1=DutyCycle\cdot i_2$$
Boost	$$v_2=\frac{v_1}{1-DutyCycle}$$	$$i_1=\frac{i_2}{1-DutyCycle}$$
Buck-Boost	$$v_2=\frac{DutyCycle\cdot v_1}{1-DutyCycle}$$	$$i_1=\frac{DutyCycle\cdot i_2}{1-DutyCycle}$$

If you set the Control input parameter to Current reference, the converter sets the output current and it computes the voltage.

Similarly, if you set the Control input parameter to Voltage reference, the converter sets the output voltage and it computes the current.

Variables

Since R2025a

To enable the Initial Targets and Nominal Values sections, set the Implementation mode parameter to Average value.

To set the priority and initial target values for the block variables before simulation, use the Initial Targets section in the block dialog box or Property Inspector. For more information, see Set Priority and Initial Target for Block Variables.

Nominal values provide a way to specify the expected magnitude of a variable in a model. Using system scaling based on nominal values increases the simulation robustness. You can specify nominal values using different sources, including the Nominal Values section in the block dialog box or Property Inspector. For more information, see System Scaling by Nominal Values.

Limitations and Assumptions

• The input voltage is positive.

• All converter types use the same polarity for input and output.

Examples

Average-Value DC-DC Converter Control

Control the output voltage of a buck-boost converter. To adjust the duty cycle, the Control subsystem uses a PI-based control algorithm. An average-value DC-DC converter model is used to speed up the simulation. The input voltage and the system load are held constant throughout the simulation. The total simulation time (t) is 0.25 s. At t = 0.15 s, the voltage reference changes and the system switches from buck mode to boost mode.

• Open Model

Linearize DC-DC Converter Model

Linearize a model of a DC-DC converter using averaged switching or an average-value converter.

• Since R2023b
• Open Live Script

Ports

Conserving

DutyCycle — Duty cycle

physical | scalar

Electrical conserving port associated with the duty cycle.

Dependencies

To enable this port, set Control Input to Duty Cycle.

Data Types: double

Iref — Current reference

physical

Electrical conserving port associated with the current reference.

Dependencies

To enable this port, set Control Input to Current reference.

Data Types: double

Vref — Voltage reference

physical

Electrical conserving port associated with the voltage reference.

Dependencies

To enable this port, set Control Input to Voltage reference.

Data Types: double

1+ — Positive DC voltage 1

electrical | scalar

Electrical conserving port associated with the positive terminal of the first DC voltage.

Data Types: double

1- — Negative DC voltage 1

electrical | scalar

Electrical conserving port associated with the negative terminal of the first DC voltage.

Data Types: double

2+ — Positive DC voltage 2

electrical | scalar

Electrical conserving port associated with the positive terminal of the second DC voltage.

Data Types: double

2- — Negative DC voltage 2

electrical | scalar

Electrical conserving port associated with the negative terminal of the second DC voltage.

Data Types: double

Parameters

Implementation mode — Converter implementation mode

Behavioral (default) | Average value

Since R2025a

Option to specify the implementation mode of the converter. To control the inverter state variables, set this parameter to Average value. For fast simulation with no dynamics, set this parameter to Behavioral.

Converter type — Converter type

Buck converter (default) | Buck-boost converter | Boost converter

Type of converter.

Dependencies

To enable this parameter, set Control Input to Duty Cycle or Implementation mode to Average value.

Control input — Control input

Duty cycle (default) | Current reference | Voltage reference

Specify the control input to convert the electrical energy between the two sides.

Dependencies

To enable this parameter, set Implementation mode to Behavioral.

Converter efficiency — Converter efficiency parameterization

Constant (default) | Tabulated

Specify the parameterization of the converter efficiency. If you select Tabulated, the conduction losses depend on the provided output current.

Note

For tabulated efficiency, the extrapolation method is nearest. Therefore, the efficiency does not go above the highest value or below the lowest value in the Efficiency vector (%) parameter.

Dependencies

To enable this parameter, set Implementation mode to Behavioral.

Efficiency (%) — Converter efficiency

100 (default) | positive scalar

Efficiency of the converter, in percentage.

Dependencies

To enable this parameter, set Implementation mode to Behavioral and Converter efficiency to Constant.

Output current vector — Vector of output current

[0, 2, 5] A (default) | row vector of at least two elements

Vector of output currents.

Dependencies

To enable this parameter, set Implementation mode to Behavioral and Converter efficiency to Tabulated.

Efficiency vector (%) — Vector of efficiencies

[90, 95, 98] (default) | row vector of at least two elements

Vector of efficiencies for each output current specified in Output current vector, in percentage. This parameter must have the same size of Output current vector.

Dependencies

To enable this parameter, set Implementation mode to Behavioral and Converter efficiency to Tabulated.

Inductance — Inductance

1e-6 H (default) | positive scalar

Since R2025a

Inductance.

Dependencies

To enable this parameter, set Implementation mode to Average value.

Inductor series resistance — Series resistance of inductor

0 Ohm (default) | nonnegative scalar

Since R2025a

Series resistance of the inductor.

Dependencies

To enable this parameter, set Implementation mode to Average value.

Capacitance — Capacitance

1e-7 F (default) | positive scalar

Since R2025a

Capacitance.

Dependencies

To enable this parameter, set Implementation mode to Average value.

Capacitor effective series resistance — Series resistance of capacitor

1e-6 Ohm (default) | nonnegative scalar

Since R2025a

Series resistance of the capacitor.

Dependencies

To enable this parameter, set Implementation mode to Average value.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2018b

R2025a: Support bidirectional power flow and model LC dynamics

The Average-Value DC-DC Converter block now supports bidirectional power flow. You can also model the converter LC dynamics. To model LC dynamics, set the Implementation mode parameter to Average value. This option exposes the LC parameters, including the inductance and the capacitance.