Hydraulic pressure supply system of automatic transmission

A hydraulic pressure supply system of an automatic transmission for a vehicle which generates low hydraulic pressure and high hydraulic pressure using oil stored in an oil pan and supplies the low hydraulic pressure and the high hydraulic pressure respectively to a low pressure portion and a high pressure portion, the hydraulic pressure supply system comprising:

• a low-pressure hydraulic pump receiving the oil stored in the oil pan through a first input line that fluid-connects the oil pan and the low-pressure hydraulic pump, generating the low hydraulic pressure, and discharging the low hydraulic pressure to a first low-pressure line;
• a low-pressure regulator valve fluid-connected to the first low-pressure line and controlling the low hydraulic pressure of the first low-pressure line to be stable low hydraulic pressure;
• a reducing valve fluid-connected to the low-pressure regulator valve and receiving the stable low hydraulic pressure from the low-pressure regulator valve through a second low-pressure line, lowering the stable low hydraulic pressure, and supplying a hydraulic pressure to the low pressure portion through a third low-pressure line;
• a high-pressure hydraulic pump fluid-connected to the first low pressure line and increasing the low hydraulic pressure supplied from the low-pressure hydraulic pump through the first low-pressure line, and discharging the high hydraulic pressure to a high-pressure line fluid-connected to the high-pressure hydraulic pump;
• a switch valve disposed between the first low-pressure line and the high-pressure line, and selectively connecting the first low-pressure line and the high-pressure line;
• a high-pressure regulator valve fluid-connected to the high-pressure line and controlling the increased hydraulic pressure supplied from the high-pressure hydraulic pump through the high-pressure line and the low hydraulic pressure selectively supplied from the low-pressure hydraulic pump through the switch valve to be a stable high hydraulic pressure, and supplying the stable high hydraulic pressure to the high pressure portion;
• and
• a second input line connecting the oil pan to the first low-pressure line;
• wherein the high-pressure regulator valve is selectively connected to the first low-pressure line through the switch valve and is directly connected to the high-pressure line so as to supply a portion of hydraulic pressure supplied from the first low-pressure line or the high-pressure line to a supply line and to control the high hydraulic pressure to be stable, and
• wherein the supply line is connected to the third low-pressure line.