Bridge circuit

A bridge circuit is a

In some motor controllers, an H-bridge is used to control the direction the motor turns.

Bridge current equation

From the figure to the right, the bridge current is represented as I₅

Per Thévenin's theorem, finding the Thévenin equivalent circuit which is connected to the bridge load R₅ and using the arbitrary current flow I₅, we have:

Thevenin Source (V_th) is given by the formula:

${\displaystyle V_{th}=\left({\frac {R_{2}}{R_{1}+R_{2}}}-{\frac {R_{4}}{R_{3}+R_{4}}}\right)\times U}$

and the Thevenin resistance (R_th):

${\displaystyle R_{th}={\frac {(R_{1}+R_{3})\times (R_{2}+R_{4})}{R_{1}+R_{3}+R_{2}+R_{4}}}}$

Therefore, the current flow (I₅) through the bridge is given by Ohm's law:

${\displaystyle I_{5}={\frac {V_{th}}{R_{th}+R_{5}}}}$

and the voltage (V₅) across the load (R₅) is given by the voltage divider formula:

${\displaystyle V_{5}={\frac {R_{5}}{R_{th}+R_{5}}}\times V_{th}}$

See also

• Phantom circuit - a use of balanced bridge circuits in telephony
• Lattice filter
  - an application of bridge topology to all-pass filters

Gallery

References