SIMPLIS Parts

Switched Voltage-Controlled Voltage Source

The Switched Voltage-Controlled Voltage Source (VCVS) models the passing of an analog voltage from input to output with unity gain. The block uses an ON/OFF control where:

VOUT = VSENSE (the input) when the control signal is in the ON state.
VOUT = RTN (ground) when the control signal is in the OFF state.

The control signal is referenced to the RTN pin.

The Logic parameter sets the control state logic. The two choices are:

POS - A CNTL voltage greater than Threshold + 1/2 Hysteresis turns on the VCVS and the output voltage equals the input voltage.
NEG - A CNTL voltage less than Threshold - 1/2 Hysteresis turns on the VCVS and the output voltage equals the input voltage.

Most users implement this function with two simple switches connected in a totem-pole configuration where VSENSE is the input voltage and VOUT is the output voltage.

Because the SIMPLIS simple switches S1 and S2 have finite ON and OFF resistances, the totem-control configuration will always have numeric inaccuracies. These inaccuracies are caused by the inherent resistive divider network formed by the switch resistances. More importantly, the totem-pole switch implementation can slow down your simulation if a small capacitive load is applied to the output. This is due to the R-C time constant formed by the switch on resistance and the capacitive load.

In contrast to the totem-pole switch circuit, this block was designed to eliminate the numeric inaccuracies caused by the voltage divider, and doesn't suffer from slow simulations with capacitive loads. You should always use this block instead of a totem-pole switch configuration since this block is speed-optimized for SIMPLIS simulations and does not exhibit the numeric inaccuracy inherent to the totem-pole switch configuration.

In this Topic ShowHide

I/O Table
Editing the Switched VCVS
Examples
Waveforms

Model Name:	Switched Voltage-Controlled Voltage Source
Simulator:		This device is compatible with the SIMPLIS simulator.
Parts Selector Menu Location:	Controlled Sources \| Voltage-Controlled Voltage Source with turn-on/turn-off
Symbol Library:	SIMPLIS_BB.sxslb
Model File:	SIMPLIS_cntl_parts_BB.lb
Subcircuit Name:	SIMPLIS_SWITCH_VCVS_BB
Symbols:
Multiple Selections:	Multiple devices can be selected and edited simultaneously.

I/O Table

The following table describes the pins on the Switched VCVS symbol.

Pin_Name	I/O	Function	Description
CNTL	I	On/Off control voltage	The threshold voltage, hysteresis, and logic of the control voltage are set in the input dialog box described in Editing_the_Switched_VCVS.
VSENSE	I	Input voltage for VCVS	The input voltage for the VCVS
RTN		Circuit return for this VCVS	The ground reference for this circuit
VOUT	O	Output Voltage for VCVS	VOUT = VSENSE when the CNTL signal is in the ON state. VOUT = 0 when the CNTL signal is in the OFF state. The initial condition can be set to either ON or OFF.

Editing the Switched VCVS

To configure the Switched VCVS, follow these steps:

Double click the symbol on the schematic to open the editing dialog.
Make the appropriate changes to the fields described in the table below the image.

Label	Parameter Description
Threshold	The threshold voltage of the CNTL signal; default is 2.5.
Hysteresis	The hysteresis of the CNTL signal; default is 1.
Initial Condition	Initial condition of the CNTL signal: default is 0 Off.
Logic	The logic of the CNTL signal, which can be set to positive or negative; default is 'POS'.

Examples

The test circuit used to generate the waveform examples in the next section can be downloaded here: simplis_071_switched_vcvs.sxsch.

Waveforms

The waveform below is the test circuit showing a sinusoidal VSENSE waveform and an asynchronous CNTL waveform.

The following waveform is for the test circuit with VSENSE hidden.