Hydraulic control system for automatic transmission

A hydraulic control system for an automatic transmission that controls a powertrain, which includes a brake for discontinuing operation of a one-way clutch operating in a low L range and a reverse R range and includes a clutch for transmitting power in third and fourth speeds, the hydraulic control system comprising:

• a manual valve including a forward range port for exhausting hydraulic pressure when driving in a forward range, and an L range port for exhausting hydraulic pressure for low speed control;
• and
• a switch valve controlled by L range pressure of the manual valve, forward range pressure, and solenoid pressure, the switch valve being controlled by a solenoid valve to selectively supply pressure to the clutch and the brake,
• wherein the switch valve, in the case where the forward range pressure is supplied, supplies pressure controlled by the solenoid valve to the clutch in the case where L range pressure is not input and supplies the pressure controlled by the solenoid valve to the brake by control of the solenoid pressure in the case where the L range pressure is input, and
• wherein the switch valve supplies pressure controlled by the solenoid valve to the brake when the forward range pressure is not input.