Hydraulic brake boost

A brake system for actuating a pair of front wheel brakes and a pair of rear wheel brakes, the system comprising:

• a reservoir;
• a master cylinder operable during a manual push-through mode by actuation of a brake pedal connected to the master cylinder to generate brake actuating pressure at a first output for hydraulically actuating the pair of front wheel brakes;
• a power transmission unit configured for selectively providing pressurized hydraulic fluid for actuating the pair of front wheel brakes during a braking event;
• a pair of rear brake motors for selectively electrically actuating respective rear wheel brakes;
• an electronic control unit for controlling at least one of the power transmission unit and the pair of rear brake motors;
• a pedal simulator in selective fluid communication with the master cylinder for providing predetermined brake pedal response;
• a two-position three-way valve hydraulically connected with the master cylinder and the power transmission unit and with the front wheel brakes;
• a plurality of arrangements of normally open first and second parallel valves arranged in parallel with one another to provide multiplex control to the pair of front wheel brakes, each of the plurality of arrangements of normally open first and second parallel valves being positioned hydraulically between the three-way valve and a corresponding one of the front wheel brakes, with each of the front wheel brakes having an associated one of the plurality of arrangements of normally open first and second parallel valves, the second parallel valve, of a selected one of the plurality of arrangements of normally open first and second parallel valves, associated with a selected front wheel brake receiving input directly from an output of the first parallel valve, of the selected one of the plurality of arrangements of normally open first and second parallel valves, associated with the selected front wheel brake, each of the plurality of arrangements of normally open first and second parallel valves being in fluid communication with the reservoir only via the three-way valve;
• the three-way valve selectively controlling hydraulic fluid flow from a chosen one of the master cylinder and the power transmission unit to at least one of the pair of front wheel brakes via a corresponding one of the plurality of arrangements of normally open first and second parallel valves.