Dual Channel Voltage-to-Current (V-I) converter circuit with BJT

This low-side voltage-to-current (V-I) converter delivers a well-regulated current to a load. The circuit accepts an input voltage from 0V to 3V and converts it to a current from 0A to 6A (combined). The current is accurately regulated by feeding back the voltage drop across a low-side current-sense resistor (R8, R9 + R16, R17) to the OPAMP. Resistor divider (R4 and R5 + R12 and R13) is implemented to limit the maximum voltage at the non-inverting input, Vin, and sense resistor, (R8, R9 + R16, R17), at full-scale. Using a Darlington BJT reduces the output current requirement for the OPAMP. Feedback components R6+R13, R7+R15, and C5+C6 provide compensation to ensure stability. R6+R13 isolates the input capacitance of the bipolar junction transistor (BJT) R7+R15 provides a DC feedback path directly at the current setting resistor (R8, R9 + R16, R17), and C5+C6 provides a high-frequency feedback path that bypass the BJT.

The project is built using the OPA2170 dual OPAMP, which enables the creation of two separate channels. Each channel is capable of handling a current of up to 3A, and when combined, they provide a total current of 6A. Users have the flexibility to utilize only one channel if a lower current is required, in which case the components associated with the second channel can be omitted. To achieve a 6A load, simply tie inputs A1 and A2 together. For a 3A load, only one input is necessary.

Features

• Input Power Supply Range 12V to 30V DC
• Load 5Amps (3A + 3A)
• Input Voltage 0 to 3V
• 4 x 4 mm Mounting Holes
• On Board Power LED
• PCB Dimensions 91.44 x 36.20 mm

Connections

• CN1: Pin 1 = Power Supply Input 12V TO 30V, Pin 2 = GND
• CN2: Pin 1 = +Load, Pin 2 = -Load
• CN3: Pin 1 = No Use, Pin 2 = Analog Voltage in for Channel A1, Pin 3 = GND
• CN4: Pin 1 = No Use, Pin 2 = Analog Voltage in for Channel A2, Pin 3 = GND
• D1: Power LED