Chopper (electronics)
In electronics, a chopper circuit is any of numerous types of electronic switching devices and circuits used in power control and signal applications.
Essentially, a chopper is an electronic switch that is used to interrupt one signal under the control of another.
In power electronics applications, since the switching element is either fully on or fully off, its losses are low and the circuit can provide high efficiency.
However, the current supplied to the load is discontinuous and may require smoothing or a high switching frequency to avoid undesirable effects.
In signal processing circuits, use of a chopper stabilizes a system against drift of electronic components; the original signal can be recovered after amplification or other processing by a synchronous demodulator that essentially un-does the "chopping" process.
Comparison between step up and step down chopper: Chopper circuits are used in multiple applications, including: For all the chopper configurations operating from a fixed DC input voltage, the average value of the output voltage is controlled by periodic opening and closing of the switches used in the chopper circuit.
The average output voltage can be controlled by different techniques namely: In pulse-width modulation the switches are turned on at a constant chopping frequency.
The total time period of one cycle of output waveform is constant.
The average output voltage is directly proportional to the ON time of chopper.
Although this modulation technique can be used to encode information for transmission, its main use is to allow the control of the power supplied to electrical devices, especially to inertial loads such as motors.
The average value of voltage (and current) fed to the load is controlled by turning the switch between supply and load on and off at a fast rate.
The longer the switch is on compared to the off periods, the higher the total power supplied to the load.
The PWM switching frequency has to be much higher than what would affect the load (the device that uses the power), which is to say that the resultant waveform perceived by the load must be as smooth as possible.
Typically switching has to be done several times a minute in an electric stove, 120 Hz in a lamp dimmer, from few kilohertz (kHz) to tens of kHz for a motor drive and well into the tens or hundreds of kHz in audio amplifiers and computer power supplies.
In frequency modulation, pulses of a fixed amplitude and duration are generated and the average value of output is adjusted by changing how often the pulses are generated.
The chopper is switched ON and OFF periodically so that the load current is maintained between predetermined maximum and minimum values.
Some types of signals that need amplifying can be so small that an incredibly high gain is required, but very high gain DC amplifiers are much harder to build with low offset and
In this way, extremely small DC signals can be amplified.
This approach is often used in electronic instrumentation where stability and accuracy are essential; for example, it is possible using these techniques to construct pico-voltmeters and Hall sensors.
Because this technique creates a very low input offset voltage amplifier, and because this input offset voltage does not change much with time and temperature, these techniques are also called "zero-drift" amplifiers (because there is no drift in input offset voltage with time and temperature).
Related techniques that also give these zero-drift advantages are auto-zero and chopper-stabilized amplifiers.
Chopper-stabilized amplifiers use a combination of auto-zero and chopper techniques to give some excellent DC precision specifications.
[5] Take a general step-up chopper with voltage source
The chopper switch would be in parallel with the series diode and load.
Whenever the chopper switch is off and using Kirchhoff Voltage Law in determining inductor voltage with respect to average current within the turn-on time,
Equating both average current and taking the duty cycle
Taking a general step-down chopper with voltage source
which is in series with the chopper switch, inductor, and the load with voltage
The diode would be in parallel with the series inductor and load.
be in series with the chopper switch, reverse biased diode, and the load with voltage
