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university:courses:electronics:switched-cap-power-supplies [09 Apr 2018 22:51] – Figure resizing Mark Thoren | university:courses:electronics:switched-cap-power-supplies [25 Jun 2020 22:07] (current) – external edit 127.0.0.1 | ||
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====== Activity 1: Switched Capacitor Voltage Inverter ====== | ====== Activity 1: Switched Capacitor Voltage Inverter ====== | ||
+ | ===== Theory and Simulation ===== | ||
Some op-amp circuits can operate on a single supply, with the op-amp negative supply pin connected to ground. However there are applications that benefit from the use of a " | Some op-amp circuits can operate on a single supply, with the op-amp negative supply pin connected to ground. However there are applications that benefit from the use of a " | ||
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<WRAP centeralign> | <WRAP centeralign> | ||
- | Each source outputs 3 microsecond pulses with a 10 microsecond period. The only difference is that V3 is delayed by 5us - this produces a " | + | Each source outputs 3 microsecond pulses with a 10 microsecond period. The only difference is that V3 is delayed by 5us - this produces a " |
{{ : | {{ : | ||
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When S3 and S4 close, C1 and C2 are placed in parallel, so the 5uc is then divided among two 1uF capacitors, resulting in a voltage of -2.5V. Subsequent charge / discharge cycles drive the output voltage closer to its final value of nearly -5V. The 1k load resistor prevents the output from ever reaching exactly -5V, but if the switching is fast enough, it can come close. | When S3 and S4 close, C1 and C2 are placed in parallel, so the 5uc is then divided among two 1uF capacitors, resulting in a voltage of -2.5V. Subsequent charge / discharge cycles drive the output voltage closer to its final value of nearly -5V. The 1k load resistor prevents the output from ever reaching exactly -5V, but if the switching is fast enough, it can come close. | ||
+ | ===== Circuit Construction and Testing ===== | ||
+ | With the simulation understood, let's move on to actual components. Open the // | ||
- | With the simulation understood, let's move on to actual components. Open the // | + | {{ : |
- | + | <WRAP centeralign> | |
- | {{ : | + | |
Build the following breadboard circuit for the voltage inverter. | Build the following breadboard circuit for the voltage inverter. | ||
- | {{ : | + | {{ : |
- | <WRAP centeralign> | + | <WRAP centeralign> |
The circuit can also be soldered on a "Perma Proto" solderable breadboard from Adafruit, which matches the layout of typical solderless breadboards. | The circuit can also be soldered on a "Perma Proto" solderable breadboard from Adafruit, which matches the layout of typical solderless breadboards. | ||
{{ : | {{ : | ||
- | <WRAP centeralign> | + | <WRAP centeralign> |
Connect a voltmeter (or M2K in voltmeter mode) between circuit ground and the OUT pin of the LT1054, and Apply 5V to the IN pin. The voltmeter should read close to -5V. | Connect a voltmeter (or M2K in voltmeter mode) between circuit ground and the OUT pin of the LT1054, and Apply 5V to the IN pin. The voltmeter should read close to -5V. | ||
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Set Scopy to Oscilloscope mode, with the following settings: | Set Scopy to Oscilloscope mode, with the following settings: | ||
- | * Timebase: | + | * Timebase: |
* CH1, CH2: 1V/div | * CH1, CH2: 1V/div | ||
* Triggering: Ch1, -1V, Falling Edge, Single Shot mode. | * Triggering: Ch1, -1V, Falling Edge, Single Shot mode. | ||
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Momentarily short LT1054 pin 1 (FB) to ground. This disables the LT1054. Release FB; this allows the LT1054 to operate again, and produces a " | Momentarily short LT1054 pin 1 (FB) to ground. This disables the LT1054. Release FB; this allows the LT1054 to operate again, and produces a " | ||
- | {{ : | + | {{ : |
- | <WRAP centeralign> | + | <WRAP centeralign> |
Run the LTspice simulation, and probe the corresponding nodes. You should see results similar to the figure below: | Run the LTspice simulation, and probe the corresponding nodes. You should see results similar to the figure below: | ||
{{ : | {{ : | ||
- | <WRAP centeralign> | + | <WRAP centeralign> |
This shows reasonable correlation between the simulation and actual measurements. This is a good thing, but it's always important to keep in mind that: | This shows reasonable correlation between the simulation and actual measurements. This is a good thing, but it's always important to keep in mind that: | ||
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{{ : | {{ : | ||
- | <WRAP centeralign> | + | <WRAP centeralign> |
If you built this circuit up on a PermaProto board, you can put it in a box and use it with your next project that requires a split (positive and negative) power supply. | If you built this circuit up on a PermaProto board, you can put it in a box and use it with your next project that requires a split (positive and negative) power supply. | ||
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====== Activity 2: Charge Pump Voltage Doubler ====== | ====== Activity 2: Charge Pump Voltage Doubler ====== | ||
+ | ===== Theory and Simulation ===== | ||
Another useful power conversion function is producing a high voltage from a lower voltage, which was demonstrated in the second half of Experiment 0. The LT1054 switches are not configured in a way that will perform this function directly, but we can use the LT1054 to drive a " | Another useful power conversion function is producing a high voltage from a lower voltage, which was demonstrated in the second half of Experiment 0. The LT1054 switches are not configured in a way that will perform this function directly, but we can use the LT1054 to drive a " | ||
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{{ : | {{ : | ||
- | <WRAP centeralign> | + | <WRAP centeralign> |
**clk_bar** asserts, turning on S1. The lower terminal of C1 is driven to Vusb, and the Pump node is driven to Vusb plus another Vusb (minus a diode drop.) | **clk_bar** asserts, turning on S1. The lower terminal of C1 is driven to Vusb, and the Pump node is driven to Vusb plus another Vusb (minus a diode drop.) | ||
{{ : | {{ : | ||
- | <WRAP centeralign> | + | <WRAP centeralign> |
The result is that Vout is " | The result is that Vout is " | ||
{{ : | {{ : | ||
- | <WRAP centeralign> | + | <WRAP centeralign> |
+ | |||
+ | As with the inverter circuit, the output takes several clock cycles to reach its final value due to charge sharing. | ||
+ | ===== Circuit Construction and Testing ===== | ||
+ | With the simulation understood, let's move on to actual components. Construct the LT1054 doubler circuit, following the LTspice schematic // | ||
- | As with the inverter circuit, the output takes several clock cycles to reach its final value due to charge sharing. With the simulation understood, let's move on to actual components. Construct the LT1054 doubler circuit, following the LTspice schematic | + | {{ : |
+ | <WRAP centeralign> | ||
Build the following breadboard circuit for the voltage inverter. | Build the following breadboard circuit for the voltage inverter. | ||
- | {{ : | + | {{ : |
- | <WRAP centeralign> | + | <WRAP centeralign> |
The circuit can also be soldered on a "Perma Proto" solderable breadboard from Adafruit, which matches the layout of typical solderless breadboards. | The circuit can also be soldered on a "Perma Proto" solderable breadboard from Adafruit, which matches the layout of typical solderless breadboards. | ||
{{ : | {{ : | ||
- | <WRAP centeralign> | + | <WRAP centeralign> |
Connect a voltmeter (or M2K in voltmeter mode) between circuit ground and the OUT pin of the LT1054, and Apply 5V to the IN pin. The voltmeter should read close to +8.6V. | Connect a voltmeter (or M2K in voltmeter mode) between circuit ground and the OUT pin of the LT1054, and Apply 5V to the IN pin. The voltmeter should read close to +8.6V. | ||
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Set Scopy to Oscilloscope mode, with the following settings: | Set Scopy to Oscilloscope mode, with the following settings: | ||
- | * Timebase: | + | * Timebase: |
* CH1, CH2: 1V/div | * CH1, CH2: 1V/div | ||
* Triggering: Ch1, +5V, Rising Edge, Single Shot mode. | * Triggering: Ch1, +5V, Rising Edge, Single Shot mode. | ||
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Momentarily short LT1054 pin 1 (FB) to ground. This disables the LT1054. Release FB; this allows the LT1054 to operate again, and produces a " | Momentarily short LT1054 pin 1 (FB) to ground. This disables the LT1054. Release FB; this allows the LT1054 to operate again, and produces a " | ||
- | {{ : | + | {{ : |
- | <WRAP centeralign> | + | <WRAP centeralign> |
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{{ : | {{ : | ||
- | <WRAP centeralign> | + | <WRAP centeralign> |
- | Note that there is a noticeable qualitative difference between the Scopy measurement and the LTspice simulation; the measured rampup appears more linear, while the LTspice rampup appears more exponential. | + | //Note that there is a noticeable qualitative difference between the Scopy measurement and the LTspice simulation; the measured rampup appears more linear, while the LTspice rampup appears more exponential.// |
====== TBD: Activity 3: Voltage Divider ====== | ====== TBD: Activity 3: Voltage Divider ====== | ||
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===== Questions: ===== | ===== Questions: ===== | ||
+ | <WRAP round download> | ||
+ | **Lab Resources: | ||
+ | * Fritzing files: [[downgit> | ||
+ | * LTSpice files: [[downgit> | ||
+ | </ | ||
**Return to Lab Activity [[university: | **Return to Lab Activity [[university: | ||