Hydraulic pressure control apparatus for automatic transmission

A hydraulic pressure control apparatus for an automatic transmission comprising:

• an oil tank for storing oil;
• a first hydraulic pump fluid-connected with the oil tank to receive the oil from the oil tank, for generating a first hydraulic pressure;
• a second hydraulic pump fluid-connected with the first hydraulic pump via a passage to receive the first hydraulic pressure from the first hydraulic pump for generating a second hydraulic pressure higher than the first pressure of the first hydraulic pump;
• a torque converter and a lubrication portion fluid-connected to a first low pressure supply line fluid-connected to the passage to receive the first hydraulic pressure from the first hydraulic pump;
• a first high pressure supply line fluid-connected to the second hydraulic pump and to a powertrain to supply the second hydraulic pressure of the second hydraulic pump to the powertrain;
• a switching valve bifurcated from the first low pressure supply line and fluid-connected to the first hydraulic pump and both the torque converter and the lubrication portion;
• and
• a feedback line fluid-connected to the first high pressure supply line to the switching valve to supply a part of the second hydraulic pressure to the switching valve through the feedback line so as to selectively open or close the switching valve according to the second hydraulic pressure in the first high pressure supply line.