Hardware » History » Version 11
Luiz Fernando Lavado Villa, 2019-02-28 14:54
1 | 1 | Luiz Fernando Lavado Villa | h1. Hardware |
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2 | 2 | Luiz Fernando Lavado Villa | |
3 | 4 | Luiz Fernando Lavado Villa | {{>toc}} |
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5 | 2 | Luiz Fernando Lavado Villa | The hardware of the single-phase project consists of a 10cm by 10cm printed circuit board that hosts 5 electronics blocks. |
6 | 3 | Luiz Fernando Lavado Villa | These blocks all fulfill functions which are necessary to the proper operation of any power electronics converter. |
7 | Figure 1 illustrates these blocks. |
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8 | 1 | Luiz Fernando Lavado Villa | |
9 | 9 | Luiz Fernando Lavado Villa | p=. {{thumbnail(theory_power_converter_1.png, size=350, title=General overview of a power electronics converter)}} |
10 | _Figure 1 - General overview of a power electronics converter_ |
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11 | 1 | Luiz Fernando Lavado Villa | |
12 | 4 | Luiz Fernando Lavado Villa | Each block is explained in detail in the sections below. |
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14 | 4 | Luiz Fernando Lavado Villa | h2. Power Block |
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16 | 9 | Luiz Fernando Lavado Villa | To better explain the Power Block, this page splits its presentation in theory and practice. |
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18 | h3. Theory |
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20 | 11 | Luiz Fernando Lavado Villa | The theory of the power block is explained in the page below. |
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22 | * [[Power Block Theory|Power Block Theory Page]] |
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24 | 5 | Luiz Fernando Lavado Villa | The Power Block is the part that manages input/output power within the board. |
25 | It consists of a single inverter leg, as illustrated in the figure below. |
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28 | 1 | Luiz Fernando Lavado Villa | p=. {{thumbnail(single_phase_topology.png, size=350, title=The power topology of the single-phase board)}} |
29 | 9 | Luiz Fernando Lavado Villa | _Figure 2 - The power topology of the single-phase board_ |
30 | 1 | Luiz Fernando Lavado Villa | |
31 | 9 | Luiz Fernando Lavado Villa | Figure 2 shows a Vlow, VHigh, T1, T2, D1, D2 and L. |
32 | Vlow is the low-side voltage, VHigh is the high-side voltage, T1 and T2 are two transistors, D1 and D2 are two diodes and L is an inductor. |
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35 | This topology is current bi-directional. |
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36 | This means that its input can be either on the high-side or on the low-side. |
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37 | If the input is on the high-side, the circuit acts as a buck or step-down converter. |
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38 | If the input is on the low-side, the circuit acts as a boost or step-up converter. |
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41 | 6 | Luiz Fernando Lavado Villa | This topology allows the control of the current in the inductor L by controlling its charge and discharge using the switches. |
42 | The figure below shows the switching and the current flow within the inductor. |
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44 | 1 | Luiz Fernando Lavado Villa | p=. {{thumbnail(states_converter_1.png, size=700, title=Current flow during switching)}} |
45 | 9 | Luiz Fernando Lavado Villa | _Figure 3 - The power topology of the single-phase board_ |
46 | 8 | Luiz Fernando Lavado Villa | |
47 | The switching leads to an average current flow between its input and output as shown in the image below. |
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49 | 1 | Luiz Fernando Lavado Villa | p=. {{thumbnail(switching_states_1.png, size=700, title=Current flow during switching)}} |
50 | 9 | Luiz Fernando Lavado Villa | _Figure 4 - Left: average current in the inductor increases_ |
51 | _Center: average current in the inductor stable_ |
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52 | _Right: average current in the inductor decreases_ |
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53 | 1 | Luiz Fernando Lavado Villa | |
54 | 9 | Luiz Fernando Lavado Villa | As figure 4 shows, the key to control the current in the power converter is to control the duration of the signal that is sent to the transistors. |
55 | This duration is called *duty cycle* . |
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56 | A longer duty cycle will lead to a increase in current, while a shorter duty cycle will lead to a decrease in current. |
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58 | The duty cycle is the single most important control variable in a power converter. |
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60 | 10 | Luiz Fernando Lavado Villa | The presentation above is, obviously, not complete since there are further phenomena to be taken into account. |
61 | 9 | Luiz Fernando Lavado Villa | The instantaneous rise and fall in current will lead to abrupt variations in voltage at both the high and low sides. |
62 | To filter these variations, power converters are equipped with capacitors in both sides, which effectively provide the instantaneous current needed by the converter. |
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64 | The relationship between high and low side voltages, high and low side currents, and the duty cycle is given by the equations below. |
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66 | 1 | Luiz Fernando Lavado Villa | |
67 | 9 | Luiz Fernando Lavado Villa | p=. !http://www.codecogs.com/eq.latex?\dfrac{V_{High}}{V_{Low}}=\dfrac{I_{Low}}{I_{High}}=\dfrac{1}{1-D}! |
68 | 10 | Luiz Fernando Lavado Villa | _Equation 1 - Relation between High and Low variables, and the duty cycle for a Boost Mode operation_ |
69 | 9 | Luiz Fernando Lavado Villa | |
70 | 1 | Luiz Fernando Lavado Villa | p=. !http://www.codecogs.com/eq.latex?\dfrac{V_{High}}{V_{Low}}=\dfrac{I_{Low}}{I_{High}}=\dfrac{1}{D}! [1] |
71 | 10 | Luiz Fernando Lavado Villa | _Equation 2 - Relation between High and Low variables, and the duty cycle for a Buck Mode operation_ |
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73 | 11 | Luiz Fernando Lavado Villa | These equations explain the need for all the other blocks of the system. |
74 | To estimate the correct duty cycle, it is necessary to measure either voltage or current, leading to a measurement block. |
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75 | Once these measurements are made, they must be converted in digital values, treated through a mathematical control loop and calculate the duty cycle value, leading to a control block. |
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76 | Once the duty cycle has been correctly calculated, it must be converted in analog voltage pulses which are in turn used to drive the transistors, leading to a driver block. |
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77 | Since all of these operations require some energy, the Feeder block is thus needed to power all of the other blocks. |
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78 | 1 | Luiz Fernando Lavado Villa | |
79 | 11 | Luiz Fernando Lavado Villa | Each block has its own specific challenges and technical difficulties, which are explained in their respective wiki page. |
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81 | 9 | Luiz Fernando Lavado Villa | |
82 | 8 | Luiz Fernando Lavado Villa | h3. Practice |
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91 | h2. Measurement Block |
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93 | h2. Control Block |
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95 | h2. Driver Block |
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97 | 1 | Luiz Fernando Lavado Villa | h2. Feeder Block |