Stepper motor current PWM control circuit

Use UC3637 to generate the H-bridge drive signal V,. and WIN (7-
pin and 4-pin). It uses a single power supply vcc-+isv. Use three 20kn resistors to divide the voltage
so that Vi=lOV (pin 1), V3-5V (pin 3), and the triangle wave changes within s-iov
(pin 2 output). The inverting input terminal of internal comparator A is pin 10, and the non-inverting input terminal of comparator B
is connected to pin 8 and pin 2. The other input terminals of comparators A and B (pins 11
and 9) are connected to pin 17 (error amplifier output). When the applied voltage at this point changes within +s-iov
, the duty cycle of the PWM output at pin 4 and pin 7 is controlled. However, the internal error
amplifier output (pin 17) may exceed this voltage range, which will cause the PWM duty cycle
to reach 0% or 100%. As pointed out earlier, this is
something that must be avoided when using capacitive coupling as the P-channel driven by the MOS-FET gate. Therefore, the outputs of pins 9 and 11 are connected to ground, +15V and pin 17 respectively with three 20kn resistors
to attenuate the output signal of pin 17.