High School

A 100 V regulated DC-DC converter must be designed using an unregulated 50-200 V source. There are two possible ways of designing the converter:

1. Use a buck-boost converter.
2. Use a buck converter that produces an intermediate voltage \(V_m\), followed by a boost converter that boosts \(V_m\) to 100 V.

For the second converter, determine a value for \(V_m\) (in terms of the duty ratios that the two converters must operate) that will allow it to operate with minimal switch current and voltage stresses.

Answer :

Options: buck-boost or buck + boost converters for 100 V dc-dc converter from 50-200 V source. Minimize switch stress with duty ratios (D and D') for desired output voltage. Values depend on voltage range.

To design a regulated 100 V dc-dc converter using an unregulated 50-200 V source, there are two possible ways: using a buck-boost converter or using a buck converter followed by a boost converter. For the second converter, we need to determine a value for Vm (the intermediate voltage) that minimizes switch current and voltage stresses.

To achieve minimal switch current and voltage stresses, we need to choose duty ratios that optimize the operation of the two converters.
1. Start by considering the buck converter. In this configuration, the duty ratio (D) is defined as the ratio of the ON time of the switch to the total switching period. The output voltage of the buck converter is given by:
Vout = (1 - D) * Vin
Since Vout should be Vm, we can write:
Vm = (1 - D) * Vin

2. Next, consider the boost converter. The duty ratio (D') of the boost converter is defined as the ratio of the ON time of the switch to the total switching period. The output voltage of the boost converter is given by:
Vout = Vin / (1 - D')
Since Vout should be 100 V, we can write:
100 = Vin / (1 - D')

3. To minimize switch current and voltage stresses, we need to choose duty ratios D and D' that satisfy both equations.
By substituting Vm = (1 - D) * Vin from equation (1) into equation (2), we can solve for D':
100 = Vin / (1 - D') => 1 - D' = Vin / 100

=> D' = 1 - Vin / 100

4. Substituting D' into equation (1), we can solve for D:
Vm = (1 - D) * Vin => D = 1 - Vm / Vin
Now we have expressions for D and D' in terms of Vm and Vin.

To design a 100 V regulated dc-dc converter using an unregulated 50-200 V source, two options are available: a buck-boost converter or a combination of buck and boost converters. For the latter, we determine Vm (intermediate voltage) to minimize switch current and voltage stresses by solving equations for the duty ratios of both converters. Specific values will depend on the desired output voltage and the unregulated source voltage range.

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