Regulation of a DC power converter

In order to set a DC chopper or a switched-mode power supply to the desired output voltage or current, there are various methods of controlling the required switching times (on / off) of the electronic switch (e.g. transistor ).

Classification

There are various features or parameters that characterize the controller. They can be combined as desired. Each combination has specific advantages and disadvantages.

Frequency:

• Pulse width modulation (PWM): the frequency is constant, the ratio on / off time ( duty cycle ) is variable.
• Pulse frequency modulation (PFM): switch-on and switch-off times are constant, the frequency or period is variable. A variable duty cycle also results .
• Hysteretic Mode (. Dt hysteresis control or hysteresis control ): on / off time and the frequency are variable, the switching time is controlled by a threshold switch obtained from the actual current or voltage value.

Current / coil state:

• DCM ( discontinuous current mode ): the storage choke ( coil ) is temporarily de-energized, also known as intermittent operation.
• CCM ( continuous current mode ): the coil is continuously energized.

Controlled variable:

• Voltage mode : the input variable for regulation is only the output voltage. Coil current and output voltage are set with a control loop.
• Current Mode : the current is controlled with the help of an inner loop. The output voltage is regulated indirectly by setting the current setpoint.
• Hysteretic mode (hysteresis mode, also two-point control): the current or the output voltage are sent to a threshold valueswitch( Schmitt trigger ) which, with its hysteresis, freely controls the switch-on and switch-off times.